Physiology- Quiz #6

The Coelom picture

FIGURE 2.7 Acoelomates, pseudocoelomates, and coelomates -Triploblastic animals can be distinguished on the basis of the presence and nature of the coelom. (a) Acoelomates lack a coelom. (b) The coelom appears between endoderm and mesoderm in pseudocoelomates, and (c) between two mesodermal layers in coelomates

Monosaccharides picture

FIGURE 3.18 Common monosaccharides -These structural models of monosaccharides show how side groups extend above and below the plane of the ring structures. The α and β forms of glucose differ in the orientation of the hydroxy group on C-1.

Complex Carbohydrates picture

FIGURE 3.20 polysaccharides (a) Plants and animals use polymers of glucose as energy stores. Amylose and amylopectin are the two polysaccharides that compose starch, an important dietary source of energyfor animals. Animals produce glycogen, which resembles the plant polysaccharides but with much greater branching.

Glycogen Metabolism picture

FIGURE 3.21 Control of glycogen synthase and glycogen phosphorylase -Under conditions in which glycogen breakdown is desirable, both glycogen synthase and glycogen phosphorylase are phosphorylated by protein kinases. Phosphorylation inhibits glycogen synthase but stimulates glycogen phosphorylase. Similarly, dephosphorylation of these two enzymes by protein phosphatases favors glycogen synthesis.

Triglycerides picture

FIGURE 3.28 triglycerides -Triglycerides are composed of three fatty acids esterified to a glycerol backbone. Fatty acids can vary in chain length and number of double bonds.

Feeding in Simple Animals: Cnidaria picture

FIGURE Cnidarian digestive system - A cnidarian, such as Hydra, captures food with its tentacles, and carries it to the mouth in mucous streams. The food passes through the open mouth into the gastrovascular cavity for digestion. Particles are phagocytosed by nutritive cells lining the cavity, and digested in endocytic vacuoles. Nutrients can then diffuse from the nutritive cells of the gastrodermal layer to the other cells of the gastrodermis (gland cells) and epidermis (sensory cells, nematocytes, epithelial cells).

Figure 13.29

I added this FIGURE 13.29 Countercurrent multiplication a) lsoosmotic fluid in tubule (no tubular flow) b) Na+ into interstitium (no tubular flow) c) water into interstitium (no tubular flow) d) tubular flow into loop of henle e) Na+ and water movements into interstitium TB -In step (a), imagine that the entire loop of Henle is filled with a fluid that has an osmolarity roughly similar to that of blood (note that this does not actually occur in a real nephron, but it provides us with a starting point with which to understand the countercurrent multiplier). As we have already discussed, the thick ascending limb actively pumps Na+ into the interstitial fluid (step b), but water cannot follow. Instead, water is drawn from the descending limb into the interstitial fluid (step c), so that the fluid in the descending limb and the interstitial fluid equilibrate, but at an osmolarity that is somewhat higher than that of blood because of the Na+ movement from the ascending limb. This increase in osmolarity in the tubular fluid is the starting point for the countercurrent multiplier, which comes into play when we consider that fluid is continuously flowing through the kidney tubules. As shown in step (d), new fluid flows from the proximal tubule into the descending limb of the loop of Henle, pushing the concentrated fluid around into the base of the ascending limb. In step (e), the ascending limb continues to pump Na+ into the interstitial fluid, but it is starting from a more concentrated solution, so it is able to generate a higher osmolarity within the interstitial fluid. In the next steps (not shown), more fluid flows into the loop of Henle from the proximal tubule and the process continues, further increasing the osmolarity in the medulla. This process repeats as the fluid flows through the loop of Henle, ultimately establishing a large osmotic gradient in the medulla. The exact extent of this osmotic gradient depends on a variety of factors, including the size of the single effect, the rate of fluid flow through the loop of Henle, and the length of the loop itself. pg.573

teeth and diet picture

look at personal slides

picture

look at picture on slides of amino acid and know where everything goes

note

Nutritionally many minerals play fundamental roles. These are usually, though not always, found in ionic form and they play a variety of roles.

Complete Digestive Tract picture

earthworm research -Digestive system of the earthworm consists of alimentary canal (mouth, buccal cavity, pharynx, esophagus, gizzard, stomach, intestine and anus) and digestive glands (pharyngeal gland, gastric epithelium, intestinal epithelium and intestinal caecae)

mosquito mouthparts picture

my note: -piercing and sucking TB -Many species possess hardened mouthparts or oral appendages that help penetrate or mechanically disrupt the surface of food Insects of the order Diptera use their mouthparts to suck fluids. For example, fruit flies siphon plant juices from rotting fruit, and mosquitoes extract blood from vertebrates.

vitamin table

no dont memorize

Coelom Formation picture

FIGURE 2.6 Gastrulation in protostomes and deuterostomes -The main distinction between protostomes and deuterostomes is the fate of the first invagination, typically the blastopore. In protostomes it forms the mouth, whereas in deuterostomes it forms the anus.

Osmotic Gradient picture

-only picture on slides FIGURE 13.26 Osmotic gradients in the interstitial fluid of the medulla -The loop of Henle passes through osmotic gradients in the medulla. The osmolarity is lowest near the border of the cortex, and increases deeper into the kidney.

osmotic gradient picture

-only picture on slides FIGURE 13.26 Osmotic gradients in the interstitial fluid of the medulla The loop of Henle passes through osmotic gradients in the medulla. The osmolarity is lowest near the border of the cortex, and increases deeper into the kidney.

note

-Salivary gland secretion is under control of the nervous system and uses both unconditioned and conditioned reflexes. -Saliva is primarily for lubrication, but in some vertebrates contains ptyalin, a salivary amylase.

notes

-The anatomy of the mammalian kidney is closely related to the physiology of the kidney: capsule, renal cortex, renal medulla, renal hilus, renal artery, renal vein, renal pelvis, and ureter.

notes

-The descending limb is permeable to water and NaCl. -The ascending limb is impermeable to water and pumps Cl- from the glomerular filtrate (in the tubule) into the interstitial fluid. Na+ follows.

note

-The distinction between a complete and an incomplete digestive tract is important.

notes

-The interstitial tissue and interstitial fluids in the cortex are isoosmotic to the blood, but toward the medulla and tips of the renal pyramids the interstitial tissue becomes more and more hyperosmotic. This is due to activities in the loop of Henle. -The descending limb is permeable to water and NaCl. -The ascending limb is impermeable to water and pumps Cl- from the glomerular filtrate (in the tubule) into the interstitial fluid. Na+ follows. -NaCl now diffuses from the interstitial fluid into the descending limb. -This active transport of NaCl is magnified by the counter-current nature of the loop. This is a counter-current multiplier.

protein deficiency picture

-the kids have bloated stomach -if you dont get essential amino acids, lack of essential amino acids cause fluid imbalance notes: -Amino acids cannot be stored to any significant extent in the animal body. Since many proteins are unstable, protein synthesis is an ongoing event. Thus, a ready supply of amino acids in the cellular amino acid pool is mandatory. -Protein function if often facilitated by non-protein accessory molecules generally referred to collectively as cofactors. These may be metal ions, prosthetic groups, or coenzymes. Many vitamins function as coenzymes.

note

-The kidney is also important in acid-base control of the blood. -my note: note H+, NH4+, HCO3- in tubular fluid and collecting duct TB -The body copes with changes in acid production through changes in ventilation and by regulating the excretion of H+ and HCO3− at the kidneys. When blood pH falls, an animal will hyperventilate, resulting in a reduction in plasma PCO2. As PCO2 falls, the carbonic anhydrase equilibrium shifts, and the concentration of H+ ions in the plasma declines, increasing the pH and restoring homeostasis. The respiratory system plays the major role in regulating body pH, but the kidneys also provide an important component. -Transport processes in each segment of the nephron contribute to changes in the pH of the primary urine as a way of controlling whole-body acid-base balance. Conversely, changes in pH of the primary urine affect the ability of cells to use pH-dependent transporters to recover or secrete ions. The main way that the nephron regulates pH of the urine is through transport and metabolism of H+, HCO3−, and ammonia. For example, metabolic acidosis leads to secretion of H+ and NH4+, and reabsorption of HCO3−. Many transporters affect pH by expelling protons into the lumen.

note

-The process of digestion can be divided into mechanical digestion and chemical digestion. -Mechanical digestion is particularly concerned with cellulose. Molluscs, insects, and herbivorous mammals are good illustrations of this phenomenon. -Chemical digestion can be intracellular or extracellular. The more "complex" the animal, the more likely we are to see an emphasis on extracellular digestion. -Food is moved along the digestive tract by mechanisms involving cilia in some animals and specialized gut musculature in other animals (peristalsis).

note

-The vasa recta is a circulatory system loop that parallels the loop of Henle. It is another counter-current system and its function is to insure that the interstitial tissue is serviced with blood but that the high osmotic concentration generated by the loop of Henle is not destroyed by flushing away all the NaCl in the circulatory system.

notes

-The vertebrate mouth features the initiation of mechanical and chemical digestion. -Teeth shape varies in carnivores and herbivores.

Transport in the Loop of Henle picture

-only picture on slides FIGURE 13.27 Transport in the loop of henle a) thin descending limb b) thick ascending limb

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The Nephron pictures (2 on slides)

FIGURE 13.15 Nephron structure -Two types of nephrons are distinguished by their location within the kidney. Though the glomerulus is in the cortex, tubules can penetrate the medulla to different degrees. (a) Cortical nephrons are located predominantly in the outer cortex. (b) Juxtamedullary nephrons are mainly in the inner medulla. FIGURE 13.16 Blood vessels of the nephron -Blood delivered to the kidney by the renal artery passes through smaller arteries and reaches an afferent arteriole that services one nephron. The arteriole diverges into the glomerulus, a network of capillaries within the Bowman's capsule. After leaving the glomerulus, blood enters an efferent arteriole. The efferent arterioles that drain cortical nephrons empty into peritubular capillaries. The efferent arterioles that drain juxtaglomerular nephrons flow into the vasa recta.

Filtration picture

FIGURE 13.17 Glomerulus (a) The glomerulus is a network of capillaries that empty much of the fluid from the blood into the Bowman's capsule of the nephron. (b) Mesangial cells between the capillaries help control blood flow through the glomerulus. The individual capillaries are composed of loosely connected endothelial cells and are covered on the external surface by podocytes. (c) The podocytes issue several foot processes that form filtration slits. (d) The podocytes interact with the basement membrane to create a filter that retains blood cells and large proteins in the plasma while permitting the passage of fluids through filtration slits.

Reabsorption of Glucose picture

FIGURE 13.21 reabsorption of glucose and Na+ -Suites of specific transporters remove solutes from the lumen in the process of reabsorption. Glucose, and other organic molecules, may be reabsorbed using a Na+-linked cotransporter. Once in the cytoplasm, the glucose can be exported across the basolateral membrane by facilitated diffusion using glucose permease. Na+ can also be reabsorbed by other transporters, such as the Na+/H+ exchangers shown here. Na+ is exported from the cytoplasm to the peritubular fluid by Na+/K+ ATPase.

Transport in Tubule Regions picture

FIGURE 13.23 Solute and water transport in each region of the nephron -Each region of the nephron has specific transporters that can reabsorb or secrete molecules.

picture on slides

FIGURE 13.23 Solute and water transport in each region of the nephron -Each region of the nephron has specific transporters that can reabsorb or secrete molecules

Vasopressin Increases Cell Permeability picture

FIGURE 13.30 Vasopressin and water permeability -Vasopressin changes the water permeability of the distal tubule and collecting duct by altering the levels of aquaporins present in the membrane. 1. Vasopressin binds G protein-linked receptor. 2. Receptor activates adenylate cyclase, increasing cAMP and activating protein kinase 3. Phosphorylation of cytoskeletal and vesicle proteins occurs. 4. This triggers translocation of vesicle to the cell membrane, with insertion of aquaporins.

Incomplete Digestive Tract picture

FIGURE 14.10 Flatworm GI tracts -Like the simple animals, such as sponges and cnidarians, the flatworms have two-way guts. (a) Most flatworms, such as Macro stomum, possess a simple gut with a single sac. (b) In some larger flatworms, such as Dugesia, the gut can have three or more side branches with lateral diverticula.

Salivary Glands

FIGURE 14.15 Salivary glands -Like most mammals, the dog has multiple sets of salivary glands that secrete liquid and enzymes into the oral cavity

Overview picture

FIGURE 14.2 Digestion -Animals use combinations of sensory and mechanical processes to acquire and ingest food. Vision and smell are central to the feeding strategies of most vertebrates. Once acquired, the food begins to undergo the process of digestion. Frequently, ingestion begins with mechanical disruption in the upper digestive tract, followed by chemical processing of the food material that is required for assimilation. Undigestible material is expelled from the animal note -An overall outline of "nutrition" information will include consideration of (a) qualities of food (b) processes of feeding (c) digestion (d) absorption/ assimilation. TB -Digestive physiology is concerned with all of the structures, tissues, and processes that contribute to the physical and chemical breakdown of food (Figure 14.2). Digestion begins with the neurosensory machinery utilized to identify food, such as an insect's antennae or a knifefish's electrical sensors. Once food is located in the broad environment, it must be captured using specialized anatomy, such as the lobster's claw, the eagle's talon, or the mosquito's proboscis. Once acquired, food is usually mechanically disrupted with the help of other specialized structures, such as a mammal's teeth or the snail's tongue. -Animals then begin the process of assimilation whereby nutrients are broken down, absorbed, and converted into useable forms. The food may be macerated, or softened, by soaking in fluids such as saliva. Chemical digestion begins with the enzymatic processes that convert large food items to macromolecules and small molecules, and releases micronutrients—ions, vitamins, and minerals—from the food. Chemical breakdown is primarily enzymatic and in most cases takes place outside the animal. Note that the inner surface of the gastrointestinal tract (or GI tract) is contiguous with the external environment. Nutrients are then transported into the animal across the epithelial cells that line the GI tract. The GI tract is wondrous in its complexity. It is composed of many cell types: absorptive cells that take up nutrients, glands that secrete suites of chemicals (mucus, acid, ions, and enzymes), muscles that control the GI tract shape and motility, and nerves that regulate GI tract function. Once the nutrients are absorbed into the animal, they may be broken down for energy or converted into other forms or stored for later use. Undigested food is expelled from the body by the process of egestion.

Carbohydrate Breakdown picture

FIGURE 14.20 Carbohydrate digestion -Starch and glycogen are broken down in the mouth and duodenum by the action of amylase. The resulting disaccharides are further processed in the duodenum by the specific disaccharidases.

Diets Provide Energy picture

FIGURE 14.3 Dietary energy -Not all food energy is digestible. Undigestible material, such as dietary fiber, is lost in the feces. Some of the nutrients taken up by the gut are lost in the urine, unmetabolized by the animal. A portion of the metabolizable energy is released as heat during the process of digestion. The remainder can be used to fuel activity, growth, reproduction, and other energy-dependent processes necessary for life.

Feeding in Simple Animals: Sponges picture

FIGURE 14.4 Sponge digestion -Water is brought through channels by the flagellated choanocytes. Food particles are phagocytosed by choanocytes and amoebocytes

Teeth picture

FIGURE 14.8 Mammalian tooth structure (a) The mammalian tooth is composed of three layers. The outer enamel is dead tissue. The inner pulp and intermediate dentin are composed of living cells, nourished by blood vessels, and innervated. The shape and size of the types of teeth vary among species. (b) Molars and premolars are generally flattened teeth used for grinding and chewing. Incisors and canines are used for piercing and tearing.

Gastrointestinal Tract picture

FIGURE 14.9 Features of a typical gastrointestinal tract -Although the exact organization of the GI tract differs among species, most complex animals have regions that are functionally analogous to the typical mammal, such as the horse shown here. then description of the mouth pharynx and larynx goes here.

Spiders and Snakes picture

TB -Many species possess hardened mouthparts or oral appendages that help penetrate or mechanically disrupt the surface of food. -A spider uses its chelicerae to attack and mechanically disintegrate its prey (Figure 14.6a) -The most important feeding structure of vertebrates is the jaw. Several species have evolved a more mobile upper jaw. Some snakes can separate or disarticulate the jawbones. The egg-eating snake can disarticulate its jaw, allowing it to open its mouth more than four times larger than its normal gape, enabling it to swallow an intact egg (Figure 14.6b). It then uses strong neck muscles to crush the egg against the spine. Once the egg contents slide down the throat, the snake vomits the eggshells.

note

The animal version of stored nutritional carbohydrate is the polysaccharide glycogen.

note

The collecting ducts pass through the interstitial tissue and it is here that the final concentration of the urine occurs, regulated by anti-diuretic hormone (ADH).

Transamination

research -Transamination is the process by which amino groups are removed from amino acids and transferred to acceptor keto-acids to generate the amino acid version of the keto-acid and the keto-acid version of the original amino acid. -Transamination as the name implies, refers to the transfer of an amine group from one molecule to another. This reaction is catalyzed by a family of enzymes called transaminases. Actually, the transamination reaction results in the exchange of an amine group on one acid with a ketone group on another acid. note: -Essential amino acids must be present in an animal's diet; non-essential amino acids do not have to be in the diet, but are still critically important in the life of the animal. Non-essential amino acids can be produced from essential amino acids by transamination.

Carbohydrates

slide - "Formula"—(CH2O)n - "Hydrates of carbon" - Many hydroxyl (-OH) groups - Glucose is the most common carbohydrate in animal diets - Energy metabolism - Biosynthesis- precursor to many other carbohydrates TB -Carbohydrates share a preponderance of hydroxyl (−OH), or alcohol, groups, and for this reason they are often called polyols. For any animal, the diet is a vital source of the carbohydrates used to build and fuel cells. Glucose, the most common carbohydrate in animal diets, is central to cellular energy metabolism and biosynthesis because of its metabolic versatility. Cells can break glucose down for energy, or store it for later consumption, or use it to build other carbohydrates needed by the cell.

Lipids

slide - All are hydrophobic (do not dissolve in water) - Carbon backbone • Linear- aliphatic • Ring- aromatic • Examples: fatty acids, triglycerides, phospholipids, steroids - Lipids are used for long term energy storage. note -Lipids (specifically triglycerides/triacylglycerols) are an important form of long term stored chemical energy in an animal. TB -Lipids are a class of hydrophobic organic molecules including fatty acids, triglycerides, phospholipids, steroids, and steroid derivatives. They have many roles in animal cells, acting as substrates for energy production, building blocks for membranes, and signaling molecules. -Fatty acids are long chains of carbon atoms (aliphatic) ending with a carboxyl group (Figure 3.25). They can vary in chain length from two carbons, as with acetate, to more than 30 carbons. -Steroids are a collection of lipid molecules that share a basic aromatic structure of four hydrocarbon rings. The steroid cholesterol is found in many cellular membranes and is part of the lipoprotein complexes that transport lipids through the blood. It is also a precursor for synthesis of the vertebrate steroid hormones. Although invertebrates don't possess steroid hormones, some use a steroidlike hormone, ecdysone, to control maturation and development. -Triglycerides are vital energy stores for animals, and can be found in high concentrations in lipid-storage tissues in the form of lipid droplets. In insects, a tissue called the fat body is the main site of lipid storage. - Lipids are used for long term energy storage. (from slides)

Sensing Food

slide - Animals detect food with different sensory receptors • Gustatory and olfactory receptors detect chemical stimuli • Various receptors detect energy emitted by, or reflected from, the food source- For example, light, sound, heat, or electricity TB -Many animals possess means of detecting the presence of specific chemicals in the environment. The chemical may be a nutrient, and movement toward the source of the nutrient increases the likelihood that the animal will find more food. -As we discussed in Chapter 7, complex animals use gustatory receptors and olfactory receptors to locate food, determine its palatability, and control the drive to feed (appetite) -Herbivorous insects, such as aphids, use gustatory receptors to detect chemicals that either stimulate feeding (phagostimulants) or deter feeding (phagodeterrents). The most important phagostimulants in insects are sugars and amino acids. Plants can deter insects from feeding by releasing secondary metabolites that an insect recognizes as toxic. -Many animals find prey by sensing the energy emitted or reflected from the animal in the form of light, sound, heat, or electricity. A bird of prey, such as the golden eagle, uses its visual system to spot a field mouse moving in a distant meadow. Some insects can detect the infrared light emitted from the warm bodies of potential prey species.

Finding and Consuming Food

slide - Basic dietary strategies • Herbivory • Carnivory • Omnivory - Physiology of digestion is matched to the chemical and physical nature of the diet TB -You are familiar with the basic dietary strategies seen in animals—carnivory, herbivory, and omnivory—each with its advantages and disadvantages. -The physiology of digestion is matched to the chemical and physical nature of the diet. To find the food that matches their dietary needs, animals use neurosensory systems. Some feeding strategies, such as filter feeding, depend on random encounters. Most animals, however, actively seek out and often pursue their food. Once found, the food must be ingested to begin the process of digestion research -Three different types of animals exist: herbivores, omnivores, and carnivores. Herbivores are animals that eat only plants. Carnivores are animals that eat only meat. Omnivores are animals that eat both plants and meat. -Herbivores eat only plant or plant products like sheep, cow, goat, etc. Carnivores are those who can eat animals only, for example lions, tigers, etc. Omnivores are those who eat both plants and animals, for example dogs, cats, and human beings.

Diets Provide Energy

slide - Energy content of diet must match the metabolic demands of the animal -Caloric equivalent - Energy content of a gram of a specific macromolecule • Protein and carbohydrates = 4 kcal/gm • Fat = 9 kcal/gm -Some food is indigestible or unmetabolizable • Energy is lost in feces or urine -Some energy is spent digesting the food • Specific dynamic action (SDA) or heat increment Increase in metabolic rate during digestion Important source of thermal energy note: -Animals are heterotrophic. Energy content of diet must match the metabolic demands of the animal. TB -The diet provides animals with nutrients that can be oxidized for energy. Every diet has an energy content that can be described in the standard units of energy: joules or calories. There must be enough energy in the diet to match the metabolic demands of the animal, also measured in joules or calories. remember the use of the term Calorie is 1 kilocalorie. -Each macromolecule has a corresponding energy con- tent, measured as a caloric equivalent. A gram of protein or carbohydrate possesses 4 kilocalories (kcal) of energy, whereas fat has 9 kcal per gram. Thus, for an animal to obtain an equivalent amount of energy, it would have to eat more than twice as much protein as fat. Gross energy is measured experimentally by calorimetry. The food material is burned to ash, and the resulting heat production reflects the total energy content (Figure 14.3). However, not all of the food an animal consumes is digestible -If you ate nothing but wood chips (4 kcal/g), you would obtain little energy because you can't digest the plant material to liberate the chemical energy trapped within the cellulose molecules. The gross energy that can be broken down is the digestible energy, and the remainder is lost in the feces. Of this digestible energy, only a fraction is metabolizable energy, with the remainder of the absorbed nutrients lost in the urine. Much of the metabolizable energy is used by the animal to support maintenance, growth, and reproduction. This is called the net energy. The remainder of the metabolizable energy is lost as a result of the digestion process. This energy, called specific dynamic action (SDA), is reflected in the increase in metabolic rate during the digestive process. The SDA, measured as heat production, is a result of the complex events occurring as a result of digestion, including the chemical hydrolysis of food as well as the elevations in metabolic rate of the digestive machinery. Anyone who has overindulged in a holiday meal will recognize the effects of SDA. The heat warms the body, and this in combination with neurotransmitters can induce drowsiness. Many large predators, such as lions and snakes, sleep after gorging in feeding bouts. -The SDA, or heat increment, as it is often termed, is an important source of thermal energy for the animal. The heat of digestion is rapidly transferred to the rest of the body by the abundant vasculature that serves the GI tract. Thus, SDA contributes to heat production in endothermic animals, reducing the need for specific thermogenic pathways. For a hummingbird feeding on a cold morning, SDA is an important contribution to whole-body heat production, helping it cope with cold air temperatures as well as cold nectar; ingesting a normal-sized nectar meal at 4°C creates a thermal challenge equivalent to that experienced when the entire hummingbird is at 15°C. In some ectothermic animals, SDA causes local warming to speed the rate of digestion. The bluefin tuna, for example, possesses counter- current heat exchangers to help retain heat within the GI tract, accelerating digestion.

Digestive Enzymes

slide - Enzymes convert macromolecules to forms that can be absorbed and processed • Lipases- Break down triglycerides and phospholipids into fatty acids • Proteases- Break down proteins into shorter polypeptides • Amylases- Break down polysaccharides into oligosaccharides • Nucleases- Break down DNA into nucleotides TB -Digestive enzymes allow animals to convert the complex macromolecules arriving in the diet to forms that can be absorbed by the animal and processed into usable forms. Although the nature of diets is very diverse, most animals rely on the same suites of digestive enzymes. • Lipases release fatty acids from triglycerides (triglyc- eride lipases) and phospholipids (phospholipases). • Proteases (trypsin, chymotrypsin) break down proteins into shorter polypeptides. • Amylases such as dextrinase and glucoamylase break down polysaccharides into oligosaccharides. Disaccharidases such as maltase, sucrase, and lactase break down specific disaccharides. • Nucleases break down DNA into nucleotides, which are then broken into nucleosides and nitrogenous bases for absorption.

Triglycerides

slide - Fatty acids esterified to a glycerol backbone • For example, mono-,di-, tri-acylglycerol - Fatty acids are stored as triglycerides • Long-term storage of fatty acids • Primary storage tissues: adipose and liver (vertebrates), hepatopancreas (invertebrates) - Lipases break the bond between fatty acid and glycerol backbone (lipolysis) TB Triglyceride is the major form of lipid storage -Most fatty acids in animal cells are esterified to a glycerol backbone. A monoacylglyceride has a single fatty acid esterified to glycerol, typically at the first position of the glycerol molecule. Diacylglyceride has fatty acids esterified to the first and second position of glycerol. Triglyceride has three fatty acids esterified to the glycerol backbone (Figure 3.28). Each of these terms—monoacylglycerides, diacylglycerides, and triglycerides—refers to a class of molecules. For example, hundreds of chemically distinct triglyceride molecules can be constructed by using different fatty acids in each of the three positions on the glycerol backbone. -Triglycerides are vital energy stores for animals, and can be found in high concentrations in lipid-storage tissues in the form of lipid droplets. In insects, a tissue called the fat body is the main site of lipid storage. Many other invertebrates, such as mollusks and crustaceans, store lipid in a large hepatopancreas. Vertebrates store triglyceride in liver, muscle, and adipose tissue, such as blubber. Adipocytes, the cells within adipose tissue, store triglyceride when an animal is well fed, then release lipids when the animal needs extra fuel. -Triglyceride synthesis, or lipogenesis, is a multistep process overlapping with phospholipid synthesis -Triglyceride breakdown, or lipolysis, requires enzymes called lipases that attack the triglyceride molecule, breaking the bond between the fatty acid and the glycerol backbone.

Control of Gut Motility

slide - Food moves along the GI tract by contractions of smooth muscle • Controlled by nerves and hormones - Optimal speed • Fast enough to minimize amount of indigestible material in the GI tract • Slow enough to allow time for digestion and assimilation • Rate will vary according to diet note -Smooth and skeletal muscle percentages vary in the wall of the esophagus of carnivores and herbivores. TB -As with most physiological systems, muscles and nerves play important roles in regulating the digestive system. Food is moved along the gastrointestinal tract by visceral smooth muscles, which are under the control of nerves and hormones. -By increasing gut motility, an animal increases the rate of passage of food down the GI tract, which in turn affects the efficiency of absorption. It must be fast enough to ensure that the animal is not carrying around a mass of undigestible material, but slow enough to allow time for digestion and assimilation. -The interplay between gut passage rates and digestibility is illustrated in the comparison of birds with different diets. Fruit-eating birds have fast passage rates. They must be able to move food quickly through the gut because undigestible material is a load that must be carried around when the animal flies. Conversely, nectar-eating birds have a nutrient- rich diet that contributes little to body mass. Slow passage rates allow these birds abundant time to absorb the nutrients. -Gut motility is regulated by nerves and hormones that act on smooth muscle

Carbohydrates + Other Macromolecules

slide - Glycosylation- addition of carbohydrates to other macromolecules - Alters function of the macromolecule. For example, glycolipids, glycoproteins. Both are typically found in plasma membranes and extracellular fluid TB -The addition of carbohydrates to other macromolecules is called glycosylation. Glycosylated lipids (glycolipids) and proteins (glycoproteins) are common in the plasma membrane of cells. A glycosylated macromolecule displays an altered molecular profile, changing how it interacts with other macromolecules and reducing its susceptibility to degradation.

Vitamins

slide - Group of unrelated molecules with diverse functions - Many participate in catalysis as cofactors for enzymes - Usually categorized based on solubility • Fat-soluble- vitamins A, D, E, K • Water soluble- vitamins B, C - Obtained in diet or from bacteria living in the gastrointestinal (GI) tract note -Vitamins can be grouped as waster- or lipid-soluble. TB -Vitamins are a group of chemically unrelated molecules with diverse functions. For simplicity, they are usually categorized based on their solubility. The fat-soluble vitamins are A, D, E, and K; the water-soluble vitamins include the B family and vitamin C -Solubility influences both the mode of uptake and the potential toxicity. An animal can consume copious amounts of water-soluble vitamins with little ill effect because any excess is readily excreted in the urine. Fat- soluble vitamins can be problematic, however, because they are stored in lipid depot tissues and can be released in a toxic pulse when fats are mobilized. -Some animals obtain selected vitamins from symbiotic bacteria living in the GI tract. For example, the gut flora of most mammals produce all the vitamin C needed in the diet.

Regulation of Urinary Function

slide - Hormones affect kidney function • Steroid hormones- For example, aldosterone. Slow response • Peptide hormones- For example, vasopressin. Rapid response - Dietary factors that affect urine output • Diuretics» Stimulate excretion of water • Antidiuretics» Reduce excretion of water TB -Endocrine hormones have a central role in regulating osmotic and ion balance in mammals, acting on both the cardiovascular system and the nephron itself to alter the nature of the urine. The steroid hormones that affect ion and water balance (mineralocorticoids) act over hours to alter transporter levels in the tubule. The peptide hormones released from the hypothalamic-pituitary axis act much more rapidly. Superimposed on the natural, hormonal controls are dietary factors that affect urine properties: Diuretics stimulate the excretion of water, and antidiuretics reduce the excretion of water. Often, these dietary factors induce maladaptive changes—dehydration or water retention—that must be overcome by intrinsic negative feedback pathways. more info -Steroid hormones called mineralocorticoids stimulate Na+ reabsorption (and secondarily water recovery from the urine) and enhance K+ excretion. The mineralocorticoids are produced by the adrenal cortex in tetrapods and the interrenal tissue in fish. These tissues, both physically close to the kidney, release aldosterone into the blood. Aldosterone targets the principal cells of the distal tubule and collecting ducts, binding to a cytoplasmic hormone receptor and entering the nucleus to stimulate transcription of genes involved in ion transport (Figure 13.31). The effects of aldosterone manifest over several hours because the process involves gene transcription, translation at the endoplasmic reticulum, processing in the Golgi apparatus, packaging into vesicles, and the fusion of the vesicles with the plasma membrane. Aldosterone and ion reabsorption= Aldosterone stimulates the transcription of a variety of genes involved in sodium and potassium transport. The renin-angiotensin-aldosterone pathway regulates blood pressure. remember... RAA pathway Angiotensin II acts at a number of different sites, including the kidney, brain, heart, adrenal cortex, and blood vessels. Recall from Chapter 9: Circulatory Systems that angiotensin II is an important regulator of the cardiovascular system, exert- ing effects on cardiac growth and angiogenesis. In terms of ion and water balance, angiotensin II stimulates Na+ reabsorption in the proximal tubule and vasoconstricts postglomerular blood vessels. It can also stimulate the synthesis and release of other hormones that exert their own effects on the kidney to increase solute and water recovery. Angiotensin II increases the synthesis and release of aldosterone from the adrenal cortex and vasopressin from the pituitary. -Vasopressin alters the permeability of the collecting duct. Note that the net effect of countercurrent multiplication is to produce a fluid in the distal tubule that has a lower osmolarity than that of blood. Producing a highly concentrated urine requires that water be reabsorbed from this dilute solution. Vasopressin, also known as antidiuretic hormone or ADH, is the main hormone responsible for recovery of water from the tubule.

The Coelom

slide - Internal cavity between layers of mesoderm - Linked to evolutionary and developmental origins of the one-way gut • Acoelomates- No coelom • Pseudocoelomates- Cavity between endoderm and mesoderm • Coelomates- Cavity within mesoderm TB -The evolutionary and developmental origins of a one- way gut are intimately linked to the appearance of the coelom, an internal cavity that arises in a developing embryo. -There are different types of coeloms that are distinguished by their embryonic origins. A pseudocoelom appears in rotifers and nematodes, arising as a gap between the endoderm and mesoderm. • Acoelomates- No coelom • Coelomates- Cavity within mesoderm (slide) -Some triploblastic animals (nemerteans and flatworms) lack an internal body cavity and are called acoelomates (Figure 2.7a). However, most triploblasts possess some form of coelom. -In pseudocoelomates, a gap appears between the endoderm and mesoderm (Figure 2.7b). -Coelomates possess a true coelom, which forms within the mesoderm layer (Figure 2.7c

Carbohydrate Breakdown and Absorption

slide - Main types consumed by animals • Polysaccharides- Glycogen, starch, cellulose, chitin • Disaccharides (sucrose, lactose, maltose) • Polysaccharides and disaccharides are broken down to monosaccharides- For example, glucose, fructose, galactose • Monosaccharides are absorbed by epithelial cells in the intestine (enterocytes)- Active transport and facilitated diffusion TB -The main types of carbohydrate consumed by animals are polysaccharides—primarily glycogen, starch, cellulose, and chitin. -Disaccharides such as sucrose, lactose, and maltose are also important in some species. -Polysaccharides and disaccharides must be broken down to monosaccharides for absorption. The various amylases and disaccharidases at work in the gut ultimately break these larger carbohydrates down to produce monosaccharides, primarily glucose, fructose, and galactose, which are absorbed by the enterocytes of the small intestine (Figure 14.20) -Animals use a combination of active transport and facilitated diffusion to carry monosaccharides from the lumen into the intestinal absorptive cells (enterocytes). Glucose and galactose typically enter enterocytes by a Na+-glucose cotransporter, whereas fructose, which occurs at relatively low concentrations in the cytoplasm, enters the cell via facilitated diffusion.

Terrestrial Animals

slide - Major innovation was loop of Henle, allowing production of concentrated urine - Mammals producing more concentrated urine have longer loop of Henle and relatively thicker medulla - Birds and reptiles without a loop of Henle conserve water by excreting uric acid TB -The variations in kidney morphology among reptiles, birds, and mammals reflect different solutions to the challenge of avoiding dehydration. The challenges of reducing water loss are greatest in desert animals, but all terrestrial animals have multiple means of matching kidney function to the constraints of environmental water availability. -Modern reptiles reduce the need for water by producing uric acid as a nitrogenous end product. Because uric acid is insoluble, water is not wasted as a solvent, although some water is used to wash the uric acid down the tubule lumen. This water can be reabsorbed in the cloaca. The reptilian kidney has much reduced glomeruli, and in some species the glomerulus is absent. As with the amphibians, the reptilian nephron lacks a loop of Henle, and therefore cannot produce hyperosmotic urine. -One of the major innovations in terrestrial vertebrate evolution was the loop of Henle. This extended segment between the proximal and distal tubules occurs only in birds and mammals, although birds have some nephrons that lack a loop of Henle. Because of the loop of Henle, most mammals can produce urine with an osmolarity that is about five times greater than the plasma osmolarity. -If it were simply the total length of the loop of Henle that determined the ability to produce concentrated urine, the elephant would be a champion; it has a long loop of Henle simply because its kidney is so large. The best predictor of the ability of the nephron to produce concentrated urine takes into account the size of the kidney. Because the loop of Henle spans the medulla, the potential to produce concentrated urine is best expressed as relative medullary thickness: the width of the medulla relative to the total width of the kidney (Figure 13.36). -Mammals that live in environments with abundant water, such as beavers, have a low relative medullary thickness and nephrons with a short loop of Henle that produce dilute urine. Conversely, mammals that live in very dry environments, such as the kangaroo rat, have a high relative medullary thickness and nephrons with a long loop of Henle that produce highly concentrated urine, typically four to five times more concentrated than that of most mammals. - Birds and reptiles without a loop of Henle conserve water by excreting uric acid (from slides)

Teeth

slide - Many vertebrates have toothlike structures - Mammalian teeth are structurally unique - Three main parts • Crown • Neck • Root - Three main layers • Enamel • Dentin • Pulp - Four types of teeth • Incisors • Canines • Premolars • Molars - Shape of the teeth reflects the type of diet TB -Many vertebrates possess oral structures that resemble and function as teeth, but mammalian teeth are structurally unique. Each tooth is composed of a crown, neck, and root (Figure 14.8). -The crown extends above the gum, or gingiva; the root is embedded in the gum; and the neck is a narrow region between the crown and the root. A cross section through the tooth reveals the three layers of a typical tooth: enamel, dentin, and pulp. -Mammals possess four main types of teeth: incisors, canines, premolars, and molars (Figure 14.8b). Incisors and canines are long, sharp teeth that aid in piercing and tearing flesh. The broad, flat molars aid in grinding. Premolars are intermediate in shape and have a role in both tearing and grinding. -Like beak morphology, the shape of mammalian teeth differs markedly in ways that reflect the nature of the diet.

Minerals

slide - Metallic elements that participate in protein structure • Calcium • Phosphorus • Iron • Copper • Zinc - Most are absorbed along the GI tract by specific transporters TB -Mineral nutrients are a collection of metallic elements that participate in many aspects of physiology, including osmoregulatory balance, cell signaling, and protein structure. -Most minerals, however, are absorbed from the diet. Calcium enters the intestinal cell through Ca2+ channels and is exported into the blood by Ca2+ ATPases. The entire transport process is accelerated in the presence of the protein calbindin. Ca2+ uptake is controlled by vitamin D, which regulates the synthesis of calbindin. Phosphorus is imported into the intestinal cells as inorganic phosphate, transported using Na+ cotransporters. Iron is imported into the cell in the ferrous form (Fe2+) by a nonspecific divalent metal transporter, co- transported with H+. If the iron arrives in the diet incorporated into heme, it can be transported into the cell in that form. Copper, zinc, and other minerals are also transported into intestinal cells by specific carriers. Once absorbed, these minerals are pumped out of the intestinal cell into the circulation. The target tissues import the minerals from the blood as needed for their own biosynthetic processes.

Salivary Glands

slide - Multicellular exocrine glands • Ducts open into mouth - Saliva • Lubricates food • Dissolves food so nutrients can bind to gustatory receptors • Cleanses the mouth with antimicrobial properties • Contain enzymes that initiate digestion • Salivation is controlled by nerve signals-Parasympathetic nerves stimulate salivation. Sympathetic nerves inhibit salivation TB -Digestion depends on secretions from multicellular exocrine glands working in conjunction with single secretory cells scattered throughout the GI tract. Many species have glands located near the mouth, typically called salivary glands. -Salivary gland secretions include enzymes that initiate the chemical breakdown of food. In terrestrial animals, saliva provides fluid to help lubricate and dissolve food, which allows solubilized nutrients to bind to gustatory receptors. The saliva may also have antimicrobial properties to help cleanse the mouth. -The rate of secretion from salivary glands is regulated by the parasympathetic system in response to pressure-sensitive receptors and chemoreceptors in the mouth. When food is taken into the mouth, the mechanical stimulation triggers pressure-sensitive receptors that send signals to the region of the brain- stem that controls serous gland secretions. Similarly, when chemoreceptors detect specific chemicals in the food, a signal is sent to the brain. As Pavlov discovered long ago, animals can also salivate in response to sights and sounds that are associated with food. Salivary gland secretions can also be inhibited. Dehydrated animals use the sympathetic nervous system to restrict blood flow to the salivary glands, preventing secretion. The same sympathetic response induces dry mouth, a response often induced in humans under stressful conditions, such as public speaking.

Cofactors

slide - Nonprotein components of enzymes - Many are loosely associated with enzymes - Prosthetic group- cofactor covalently bonded into the enzyme - Coenzymes- organic cofactors usually derived from vitamins - Inorganic ion cofactors- copper, iron, magnesium, zinc TB -Many enzymes possess nonprotein components, called cofactors. A cofactor that is covalently bonded into the enzyme is called a prosthetic group. -Some enzymes use cofactors that are metals, such as copper, iron, magnesium, zinc, and selenium. -Organic cofactors, or coenzymes, are usually derived from vitamins; coenzyme A is derived from pantothenic acid, FAD from riboflavin, and NAD from niacin. -Many of the life-threatening diseases we associate with vitamin deficiencies can be traced back to perturbations of metabolism due to loss of function of specific enzymes.

Complete Digestive Tract

slide - One-way gut (gastrointestinal tract) • Specialized regions • Mouth, pharynx, esophagus- Mechanical breakdown of food • Stomach- Acidic compartment • Upper or small intestines- Digestion and absorption • Lower or large intestines- Absorption of water • Anus- Release of indigestible material note -A complete digestive tract allows much more specialization of various sections of the tract. One can note successive regions of such a tract: reception, conduction and storage, digestion, absorption, and conduction and formation of feces. TB -Sponges lack a gut; cnidarians and platyhelminths have blunt-ended sacs or two-way guts, where food enters and leaves through a single opening. With the evolution of the one-way gut, animals were better able to create specialized regions. The nature of these regions varies considerably among animals. Our description of gut regions is based on the terminology used for mammals (Figure 14.9). The mouth opens into the upper region of the GI tract called the pharynx or esophagus. This upper region typically participates in the mechanical breakdown of food. The gastric region or stomach follows; in most animals this is an acidic compartment. The upper intestine, or small intestine, neutralizes the acidic solution released from the stomach, and carries out much of the digestion and nutrient absorption. The upper intestine also receives exocrine secretions from digestive glands: the liver and pancreas in most vertebrates and the hepatopancreas in most invertebrates. The lower intestine, or large intestine, is responsible for reclamation of water and salts. Finally, undigestible material is released through the anus.

Complex Carbohydrates

slide - Polysaccharides (Glycans) - Long chain of monosaccharides • Energy storage- Example: glycogen (in animals), starch (in plants) • Structural molecules- chitin (in insects), cellulose (in plants) TB -Complex carbohydrates, or polysaccharides, are larger polymers of carbohydrates that serve in energy storage and structure. Polysaccharides can be composed of long chains of a single type of monosaccharide or combinations of two alternating monosaccharides. Common polysaccharides important in metabolism and structure are shown in Figure 3.20. -Polymers of glucose are important forms of stored energy in plants and animals. Long chains are created when α-D-glucose molecules are attached between carbons 1 and 4 (α1,4 glycoside bonds). Plant starch is a mixture of amylose, which has few branches, and amylopectin, which has a side branch approximately every thirty glucose molecules. Starch is used by the plant for glucose storage, but it is an important dietary source of energy for many animals. Glycogen is like amylopectin but with branches approximately every ten glucose molecules. Acting as an internal energy store for most animals, glycogen is central to the energy metabolism of an animal and is a nutrient for animals that eat other animals. -Cellulose, another plant-derived glucose polymer, is essentially indigestible in animals because the glucose units are connected by β1,4 glycoside bonds. Cellulose, in most animals, provides dietary fiber. However, some animals, such as ruminants and termites, possess gastrointestinal symbionts that can degrade cellulose for energy. -Polysaccharides are also critical structural components of animal cells. Arthropods build their exoskeletons with chitin, a polysaccharide of N-acetyl-glucosamine. Vertebrates secrete hyaluronate, a polymer of N-acetyl-glucosamine and glucuronic acid, into the extracellular space, where its gel-like properties act as a spacer between cells and tissues. Hyaluronate is a member of a class of compounds called glycosaminoglycans that include chondroitin sulfate and keratan sulfate. These compounds are important components of animal tissues such as cartilage.

Amino Acids

slide - Proteins are polymers of amino acids - Amino acids- amino group (-NH2) and carboxylic acid group (-COOH) - Termed a-amino acids because-NH2 and-COOH are located on the first (a alpha) carbon - Distinguished by side groups (R) - Can be nonpolar (hydrophobic), polar-uncharged (hydrophilic) and polar-charged (hydrophilic) - Animals use 20 amino acids to build proteins - Most can be produced by the animal • Eight essential amino acids must be obtained in the diet • Diets deficient in any essential amino acid lead to developmental defects and slow growth PROTEIN QUALITY -Animal tissue provides higher protein quality than plant tissue -Some plants lack specific amino acids -The amino acid profile of dietary protein (this point might go first) note -Essential amino acids must be present in an animal's diet; non-essential amino acids do not have to be in the diet, but are still critically important in the life of the animal. Non-essential amino acids can be produced from essential amino acids by transamination. TB Proteins are polymers of amino acids -Animals build proteins from combinations of 20 amino acids. As the name implies, amino acids share the general structure of an amino group (−NH2) and a carboxylic acid group (−COOH). They are called α-amino acids because both the amino and carboxyl groups are located on the first, or α, carbon. -Amino acids are distinguished from one another by their side groups (R). The R groups of polar amino acids form hydrogen bonds with water. Some polar amino acids are uncharged at physiological pH values (serine, threonine, cysteine, tyrosine, asparagine, glutamine), while others possess R groups with side chains that can become charged. -Acidic amino acids (aspartate, glutamate) are negatively charged at physiological pH when carboxyl groups become deprotonated (−COOH → −COO− + H+). Basic amino ac- ids (arginine, lysine) take on a positive charge when amino groups become protonated (−NH2 + H+ → −NH3+). Many amino acids are nonpolar because their R groups are aliphatic chains (alanine, valine, leucine, isoleucine, methionine) or aromatic rings (phenylalanine, tryptophan) that do not readily interact with water. -Inadequate supply of essential amino acids compromises growth Most of the 20 amino acids that animals use to build proteins can be produced de novo, but a subset of amino acids must be obtained preformed in the diet. Typically, there are eight essential amino acids: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Some species have additional essential amino acids. -If a diet is persistently deficient in any of the essential amino acids, the animal may experience developmental defects or slower growth. Because dietary protein is the source of these amino acids, protein quality—the profile of amino acids in dietary protein—is a critical nutritional concern. Animal tissues provide a higher quality dietary protein than do plant tissues, because they possess an amino acid profile that more closely resembles the needs of other animals. In contrast, plant proteins are often deficient in one or more of the essential amino acids. For example, maize proteins are deficient in lysine and wheat proteins are deficient in tryptophan. An herbivore can avoid amino acid deficiencies by eating plants with different combinations of deficiencies.

Feeding in Simple Animals: Sponges

slide - Simple animals (e.g., sponges) ingest food by phagocytosis • Digestion occurs intracellularly in endocytic vacuoles TB -The simplest of animals, the sponges, obtain nutrients primarily by phagocytosis, much like protists such as the amoeba. Sponges subsist on particles of various sizes, ranging from organic debris much smaller than bacteria (50 μm). Water carrying food particles passes through the sponge's network of pores and channels, flowing in currents generated by flagellated cells called choanocytes (Figure 14.4). As the water permeates the animal, it flows through biological filters that sort particles by size. Cells that line the pores, choanocytes as well as amoebocytes, engulf the particles using phagocytosis. -Digestion occurs inside these cells in endocytic vacuoles. Breakdown products are released into the cell, and undigested material is exocytosed out of the cell.

Specialized Compartments

slide - Specialized compartments increase efficiency of digestion - Compartments have functional specializations • pH • Enzymes • Types of secretory and absorptive cells - Muscular valves (sphincters) control passage of food from one compartment to the next - Complexity of gut morphology varies across taxa • Reflects complexity of the diet and ease of digestion TB -Specialized compartments increase the efficiency of digestion -Regional specializations are more developed in animals with a one-way gut. In many cases, muscular valves called sphincters control the passage of food from one compartment to the next. Regional properties are created and maintained by specific types of cells. Some cells alter the pH of the fluids in the lumen by secreting acids or bases. Because most of the macromolecules that appear in food are stable at a pH near neutrality, extremes in pH can enhance their breakdown. Mucus secretions help protect cells and lubricate the surface. Secretory cells release the digestive enzymes— proteases, amylases, lipases, and nucleases—that accelerate chemical breakdown of macromolecules. The absorptive cells in each region also possess specialized transport capacities. -Muscular valves (sphincters) regulate passage through the different compartments. -Superimposed on the evolutionary (interspecies) variation in gut design are modifications that arise in individuals in response to diet and life history. The mammalian diet changes as offspring transition from maternal blood-borne nutrients across the placenta, to mammary gland secretions, to solid food

Incomplete Digestive Tract

slide - Two-way gut • Simple internal sac • Sac may have diverticula to increase surface area • Food enters and wastes leave via the same opening TB -The nature of the digestive system differs greatly in animals. The simplest of animals—sponges—lack a discrete digestive system. Cnidarians possess a blunt-ended gastrovascular cavity, where food enters and exits through the same opening. -With some exceptions, other animals possess some form of gastrointestinal tract, the complexity of which grows with the evolution of the three cell layers and an internal coelom. -The digestive tract of flatworms is, as in cnidarians, a two-way gut; however, the gut itself can be simple or quite complex, with many branches called diverticula (Figure 14.10).

Urine Concentration

slide -Osmotic concentration of final urine depends on permeability (aquaporins) of the collecting duct, which can be regulated by vasopressin • Impermeable > Water not reabsorbed from collecting duct > Dilute urine (formed in ascending limb) excreted • Permeable > Water reabsorbed from collecting duct > Concentrated urine (formed in collecting duct) excreted TB -Another factor that contributes to the formation of the osmotic gradient within the medulla is the permeability of the collecting duct to urea. Urea enters the tubule through the glomerulus, but travels through the tubule with little reabsorption because of the low urea permeability of the tubule. With much of the water removed from the original filtrate, the urea concentrations increase dramatically. The concentrated urea solution leaves the tubule and enters the collecting duct. The cortical regions of the collecting duct have low permeability to urea, but as the collecting duct moves deeper into the medulla, the permeability to urea increases due to the presence of specific urea transporters. Movement of urea into the interstitium increases the local osmolarity, further contributing to the osmotic gradient within the medulla.

Mechanical and Chemical Digestion

slide • Mechanical digestion is particularly concerned with cellulose. Molluscs, insects, and herbivorous mammals are good illustrations of this phenomenon. my note: chemical digestion is when macromolecules are broken down glycogen into glucose for example. cellulose to glucose. Peristalsis slide that is not on there TB -Peristalsis is a slow wave of contraction that progresses down the GI tract to push food toward the anus. It is controlled by the intrinsic myogenic activity of the smooth muscle cells, but also influenced by interstitial cells of Cajal that act as pacemaker cells. Much like the pacemaker cells of the heart, these cells spontaneously depolarize to initiate a wave of depolarization to the smooth muscle cells to which they are attached via gap junctions note: -Food is moved along the digestive tract by mechanisms involving cilia in some animals and specialized gut musculature in other animals (peristalsis).

Selective or Non-selective Feeding

slide • Selective feeding, food procurement in which the animal exercises choice over the type of food being taken, as opposed to • non-selective feeding, in which food is taken randomly. notes -Food gathering methods can be illustrated by considering the types of food being gathered such as mechanisms for dealing with small particles, larger particles or masses, or for taking in fluids or soft tissue. -A second way to organize feeding techniques is to contrast selective feeding with non-selective feeding. -Selective feeders frequently illustrate interesting correlations between anatomy and physiology. my personal note: -earthworm is a non-selective feeder. TB -Beak morphology is very diverse among birds, reflecting the type of food each bird gathers. Very long beaks can be used to reach deep into flowers; the beak of the sword- billed hummingbird is longer than the body of the bird itself. Flamingos use the beak as a sieve to strain food out of water. Some birds, such as the puffin, possess toothlike ridges on the margins of the beak to assist in tearing apart flesh.

Digestion steps

slide • The gathering of food • Digestion events • Absorption events note -Major steps of consideration are (a) the gathering of food (b) digestion events and (c) absorption events. TB nothing

Vasopressin

slide - Also called antidiuretic hormone (ADH) • Peptide hormone • Produced in hypothalamus and released by posterior pituitary gland • Increases water reabsorption from the collecting duct by increasing number of aquaporins • Release stimulated by increasing plasma osmolarity detected by osmoreceptors in the hypothalamus • Release is inhibited by increasing blood pressure detected by stretch receptors in atria and baroreceptors in carotid and aortic bodies note -ADH is synthesized in the supraoptic nuclei of the hypothalamus and stored/released from the posterior pituitary gland. This is an example of neurosecretion. TB Vasopressin alters the permeability of the collecting duct -Note that the net effect of countercurrent multiplication is to produce a fluid in the distal tubule that has a lower osmolarity than that of blood. Producing a highly concentrated urine requires that water be reabsorbed from this dilute solution. Vasopressin, also known as antidiuretic hormone or ADH, is the main hormone responsible for recovery of water from the tubule. After this peptide hormone is produced in the cell bodies of hypothalamic neurons, it travels down the neurons to the pituitary gland, where it is released into the circulation. High vasopressin levels increase the reabsorption of water by the collecting duct. Vasopressin alters water uptake by affecting the number of aquaporins in the apical membrane of the principal cells of the collecting duct (Figure 13.30). -When the hormone binds to its G protein-linked receptor in the plasma membrane, it triggers a signaling pathway that acts via cAMP and protein kinase A to translocate vesicles containing preformed aquaporins to the apical membrane. Because vasopressin acts through a G protein- coupled pathway to alter the localization of already existing proteins, its actions are very rapid; the permeability of the collecting duct can be altered within a few minutes. Once vasopressin levels fall, the pathway reverses and aquaporins are removed from the membrane by endocytosis. (from slides) • Release stimulated by increasing plasma osmolarity detected by osmoreceptors in the hypothalamus • Release is inhibited by increasing blood pressure detected by stretch receptors in atria and baroreceptors in carotid and aortic bodies

Monosaccharides

slide - Basic units of carbohydrates - Used for energy and biosynthesis - Small carbohydrates have three to seven carbons- six is most common TB -Monosaccharides are small carbohydrates that have from three to seven carbons. The most common monosaccharides are the six-carbon sugars (hexoses), including glucose, fructose, and galactose (Figure 3.18). Glucose and galactose, as well as mannose, can be modified by the addition of acidic groups, amino groups, and modified amino groups. These sugar derivatives serve many purposes in the cell, primarily as modifications of other macromolecules, including proteins, lipids, and nucleic acids. -Many of the sugars that animals obtain in the diet are disaccharides, two monosaccharides connected by a covalent bond (Figure 3.19). In order to use disaccharides, animals first break them down into monosaccharides. Animals can also produce disaccharides such as lactose, an important component of milk in mammalian mammary secretions, and trehalose, an energy store and solute.

Coelom Formation

slide - Blastopore appears early in development, during gastrulation - Protostomes • Most invertebrates • Blastopore becomes mouth • Coelom forms when mesoderm splits (schizocoelous) - Deuterostomes • Chordates, hemichordates, echinoderms • Blastopore becomes anus • Coelom forms when mesoderm pinches off from the gut (enterocoelous) • Schizocoelous process in chordates TB -During early gastrulation, a region of the blastula (a hol- low ball of cells) migrates inward, causing first a depression and then a pit called the blastopore. In animals classified as protostomes ("first mouth") the blastopore becomes the mouth, and the anus forms at a distant site. Arthropods, annelids, and mollusks are all protostomes. -In deuterostomes ("second mouth"), the anus arises from the blastopore, and the mouth is formed second. Deuterostomes include chordates, hemichordates, and echinoderms (Figure 2.6). -A coelom forms by enterocoely or schizocoely The appearance of the coelom was important in the evolution of physiology because it allows greater specialization of internal organs. The coelom arises early in embryonic development, though it originates by different routes in protostomes and deuterostomes. It may form when the mesoderm splits to form an internal compartment (schizocoely) or when layers of mesoderm pinch off from the gut (enterocoely). Protostomes generally display schizocoely and deuterostomes enterocoely, though chordates show schizocoely.

Feeding in Simple Animals: Cnidaria

slide - Cnidaria bring food into the gastrovascular cavity • Digestion occurs extracellularly and intracellularly TB -Other metazoans possess something akin to a mouth— an entrance to an internal compartment that carries out digestion. The challenge for many animals is to get the food to the mouth. Cnidarians, such as corals and Hydra, use tentacles to capture small prey, such as zooplankton. Once the prey is captured, the tentacle bends to the mouth to release the food. The mouth gapes to permit food to enter the gastrovascular cavity. Movement down the tentacles and into the mouth is aided by a layer of mucus secreted by the epithelial cells. The wall of the gastrovascular cavity is composed of gastrodermal cells, including nutritive cells and enzymatic gland cells (Figure 14.5). The enzymatic gland cells release digestive enzymes that break down prey into a slurry of nutrients. The nutritive cells phagocytose the smaller particles and process them within the endocytotic food vacuole, releasing nutrients that escape the gastrodermis and cross the gelatinous mesoglea to supply the diverse cells of the epidermis, including the stinging cells, or nematocytes. Once the meal is digested, the animal expels the remaining material from the gastrovascular cavity and feeds again.

Proteins

slide - Contribute to cell structure (cytoskeleton) and function - Mediate all cellular processes • Enzymes - Have complex three-dimensional structure - Protein structure is coded in DNA - Nutritional function note -Proteins play many roles in animals, including a nutritional one. TB -Proteins play many important roles in cell structure and function. Almost all enzymes are proteins (though many have nonprotein components). Proteins form the internal skeleton of a cell (cytoskeleton) as well the extracellular matrix needed to organize cells into complex tissues. The diversity in protein structure is afforded by the use of 20 amino acids that can be strung together in countless combinations. The blueprint for all proteins in a cell is in the form of DNA, which is transcribed into RNA and translated to form the appropriate proteins at the right time. -Once the primary structure is established, proteins are organized into more complex three-dimensional conformations (Figure 3.17). In many cases, the three-dimensional arrangement is a natural consequence of the primary structure, arising automatically when the protein is made. The overall structure is, however, also labile. The weak bonds discussed earlier in this chapter control the structure of proteins, and their vulnerability to physical and chemical factors means protein structure changes in response to specific environments. - Nutritional function (from slides)

Ion and Water Transport in the Loop of Henle

slide - Descending limb is permeable to water and NaCl > Water is reabsorbed > Volume of primary urine decreases > Primary urine becomes more concentrated - Ascending limb is impermeable to water > Ions are reabsorbed > Primary urine becomes dilute - Reabsorbed ions accumulate in interstitial fluid > An osmotic gradient created in the medulla TB -When the primary urine has passed through the proximal tubule, the volume has diminished and most of the valuable solutes have been recovered. The remainder of the tubule is responsible for recovering the balance of the solutes and water -The next region encountered by the primary urine is the descending limb of the loop of Henle. This region of the tubule is specialized to transport water, but it is not a major site of transport for solutes. As with the proximal tubule, aquaporins allow water to move across epithelial cells in relation to the osmotic difference from the lumen to the interstitial fluid. -Critical to the water recovery strategy is an osmotic gradient that exists within the medulla (Figure 13.26). At the transition between the proximal tubule and descending loop of Henle, the osmolarity of the interstitial fluid is similar to that of the blood—about 300 mOsM. As the descending loop of Henle goes deeper into the medulla, the osmolarity of the interstitial fluid increases, drawing water from the primary urine across the epithelial cells. With loss of water, but not solutes, the osmolarity of the primary urine increases, reaching a maximum at the loop region of the loop of Henle. -Once the tubule turns and moves back toward the cortex, the epithelial cell transport capacity changes. Instead of expressing aquaporin genes, these epithelial cells express solute transporters. As the tubule passes through the medulla, the interstitial osmolarity decreases. Because the epithelial cells can only transport solutes, the transepithelial gradients drive movements of solutes from the primary urine to the interstitial fluid. As a result of various transporters in the apical and basolateral membranes, there is a net movement of Na+ and Cl− from the primary urine to the interstitial fluid. On the apical membrane, the NKCC transporter mediates uptake of Na+, K+, and Cl− into the cell. The basolateral membrane transports Na+ and Cl− into the interstitial fluid: Na+ via the Na+/K+ ATPase, and Cl− via Cl− channels and a K+-Cl− co- transporter. An apical K+ channel allows K+ imported via NKCC to escape back to the lumen. The transport processes in the ascending limb and descending limb are summarized in Figure 13.27.

Transport in Tubule Regions

slide - Differences in transport and permeability due to differences in epithelium along the tubule TB -previous flashcard -DONT MEMORIZE CELL TYPES picture: FIGURE 13.24 Cell type and morphology in the tubule and collecting duct -The wall of the tubule is composed of a single layer of epithelial cells that differ in morphology.

Kidney Structure and Function picture

title: Mammalian kidney -The kidney is composed of two layers, the cortex and the medulla. As urine is produced, it is collected by the minor calyces, which join together to form the major calyx. The urine passes through the ureter into the urinary bladder for storage, eventually leaving the animal through the urethra.

Tubule Regions

slide - Different regions of the tubule have different transport functions and permeabilities • Proximal tubule- Most of the solute and water reabsorption • Loop of Henle- Descending limb and Ascending limb • Distal tubule- Reabsorption completed for most solutes • Collecting duct- Drains multiple nephrons and Carries urine to renal pelvis TB -The transformation of the primary urine to the final urine involves a series of specialized regions of the tubule that depend upon cellular specializations (Figure 13.23). Though the tubule wall is a single layer of epithelial cells connected together by tight junctions, cell morphology and function differ considerably among regions of the tubule. -The proximal tubule can be a simple, straight tube or take a path with many convolutions; for this reason it is sometimes called the proximal convoluted tubule. The cells of the proximal tubule are tall cuboidal epithelial cells, with abundant mitochondria and microvilli. As with other epithelial tissues, these features are common in cells that carry out energy-dependent solute transport processes. -The proximal tubule then gives way to the loop of Henle. There is considerable variation in the nature of the loop of Henle among species, and even among nephrons of a single animal. In general, the loop of Henle is divided into a descending limb, a loop, and an ascending limb. The first part of the descending limb of the loop of Henle is composed of cuboidal epithelial cells, much like the proximal tubule. These are gradually replaced with the flatter squamous epithelial cells. The difference in the height of the cuboidal and squamous cells creates a difference in width of the wall, and these regions of the tubule are often distinguished as thick descending limb and thin descending limb. Further along the tubule, the ascending limb of the loop of Henle becomes thicker as cuboidal epithelial cells predominate. As with the descending limb, the ascending limb may be subdivided as thin ascending limb and thick ascending limb. These distinctions are made because the differences in cell shape coincide with distinctions in transport properties. -Following the loop of Henle is the distal tubule, which can be simple and straight or long and convoluted. In contrast to the proximal tubule, most of the epithelial cells of the distal tubule have simple membranes with few microvilli. This type of cell, known as a principal cell, also dominates the cell profile of the collecting duct. The less common intercalated cells are cuboidal epithelial cells with abundant microvilli. Not surprisingly, the functions of principal cells and intercalated cells differ as much as their structures. -The differences in cell type and morphology along the tubule and collecting duct are summarized in Figure 13.24. -The proximal tubule is specialized for transport, and it is the region where most solute and water reabsorption occurs

Urine Production

slide - Four processes • Filtration- Filtrate of blood formed at glomerulus • Reabsorption- Specific molecules in the filtrate removed • Secretion- Specific molecules added to the filtrate • Excretion- Urine is excreted from the body note: -Blood pressure is high enough in the glomerulus to drive fluid out of the circulatory system into Bowman's capsule. This filtration event removes a great deal of water, materials the body intends to remove (i.e. urea), and materials the body does not intend to remove (i.e. glucose and amino acids). Water and materials in this latter category now begin to be reabsorbed (that is, moved from within the contents of the nephron back into the circulatory system from where they were filtered in the first place.) TB -The kidney performs four main processes -The four main processes performed by the kidney are filtration, reabsorption, secretion, and excretion. -The first step in urine formation involves the process of glomerular filtration, when plasma is filtered from the glomerular capillaries into the Bowman's capsule. This filtration step results in a fluid, called primary urine, with a composition very similar to that of blood, except that it lacks cells and large macromolecules such as proteins (and also has low levels of some small molecules such as calcium and fatty acids that are closely associated with plasma proteins). Note that filtration is not a very selective process, as almost all molecules below a certain size will pass through the filter into the primary urine. The primary urine then passes into the tubules of the nephron, where its composition is altered through the processes of reabsorption and secretion. Reabsorption occurs when a substance is moved from the tubular fluid back into the blood, whereas movement from the blood into the tubular fluid is called secretion. Both reabsorption and secretion are highly selective and can be isolated to particular locations. Thus, only specific substances are moved out of or into the tubular fluid. Together, the processes of reabsorption and secretion act to transform the composition of the primary urine into the urine that is collected in the urinary bladder and excreted.

The Nephron

slide - Functional unit of the kidney - Composed of • Renal tubule > Lined with transport epithelium. > Various segments with specific transport functions • Vasculature > Glomerulus: Ball of capillaries. Surrounded by Bowman's capsule > Capillary beds surrounding renal tubule note -The functional unit of the kidney is the nephron. TB -The nephron is the functional unit of the kidney -The nephron is the main structural and functional unit of the kidney -In a typical kidney, some nephrons (termed cortical nephrons) are located relatively high within the renal cortex and extend only a short distance into the renal medulla. -Others are longer and extend deep into the renal medulla (these are termed juxtamedullary nephrons because they begin fairly deep within the renal cortex near the junction with the medulla) (Figure 13.15). -Each nephron is composed of two regions with differing functions: (1) the renal corpuscle (or Malphigian corpuscle), which filters the blood, and (2) the renal tubules, which modify the filtered fluid by reabsorbing or secreting specific substances. The renal corpuscle is composed of a twisted ball of capillaries called the glomerulus and the surrounding Bowman's capsule, which is a cuplike expansion of the renal tubules. The renal tubules are formed from a single layer of epithelial cells and can be divided into three regions with differing transport properties. extra from TB but should know because it goes with pictures on slides... -Fluid leaving the Bowman's capsule first enters the proximal tubule and then enters the loop of Henle, which forms a hairpinlike loop consisting of a descending limb and an ascending limb. After leaving the loop of Henle, the fluid then enters the distal tubule. The fluid from multiple distal tubules drains into a single collecting duct, several of which fuse together to form papillary ducts, which in turn empty into the minor calyx of the kidney. -The vasculature of the nephron is central to nephron function, (Figure 13.16)(second picture, on slides its on right) Blood enters the kidney from the renal artery, which branches into smaller vessels that ultimately give rise to the afferent arteriole that leads into the capillaries of the glomerulus. After the filtered blood leaves the glomerulus, it passes into an efferent arteriole. This arrangement is unlike that of a conventional capillary bed where the venous system is immediately downstream of the capillaries. The efferent arteriole generates enough smooth muscle contraction to maintain a degree of vasoconstriction, causing a higher degree of resistance than could a venule. The blood passes through the efferent arteriole into one of two types of capillary beds. In cortical nephrons, the efferent arterioles flow into peritubular capillary beds that wrap around the tubules In juxtamedullary nephrons, the efferent arterioles diverge into the vasa recta, long, straight vessels that run along the loop of Henle. The blood from these capillary beds then drains into the venous system, carrying away recovered solutes and water from the interstitial fluid that surrounds the tubule.

Glycogen Metabolism

slide - Glycogen synthesis (glycogenesis) - Glycogen breakdown (glycogenolysis) TB -In order to use glycogen as an energy store, animals control the balance between glycogen synthesis (glycogenesis) and glycogen breakdown (glycogenolysis). Glycogen phosphorylase initiates glycogenolysis, releasing glucose in the form of glucose 1-phosphate. When glucose is abundant, glycogen synthase is activated and glucose 1-phosphate is used to increase the size of the glycogen particle. Protein kinases and protein phosphatases regulate both glycogen synthase and glycogen phosphorylase (Figure 3.21).

Gut Formation

slide - Gut is derived from endoderm - Three regions • Foregut- Esophagus, stomach, and the anterior section of the duodenum. Forms buds that become the pancreas and liver • Midgut- Posterior part of duodenum, jejunum, ileum, and large intestine • Hindgut- Colon and rectum TB -The early embryonic gut is derived from endoderm, and divided into three regions: foregut, midgut, and hindgut. These regions differentiate to form the embryonic gastrointestinal tract. -The foregut endoderm gives rise to the esophagus, stomach, and anterior region of the duodenum of the small intestine. It also forms buds that develop into the pancreas and liver. -The midgut endoderm develops into the posterior part of the duodenum, the remainder of the small intestine (jejunum and ileum), and much of the large intestine, including cecum, appendix, and part of the colon. -The hindgut endoderm develops into the remainder of the colon and the rectum.

Filtration

slide - Liquid components of the blood are filtered into Bowman's capsule • Water and small solutes cross glomerular wall • Blood cells and large macromolecules are not filtered - Glomerular capillaries are very leaky • Podocytes with foot processes form filtration structure - Mesangial cells control blood pressure and filtration within glomerulus - Filtrate flows from Bowman's capsule into proximal tubule TB -Filtration occurs at the glomerulus -The wall of a glomerular capillary is a complex biological filter that retains the blood cells and large macromolecules but permits liquid and small molecules in blood to escape into the lumen of the Bowman's capsule (Figure 13.17). The glomerular capillaries are fenestrated, with pores that allow low-molecular-weight molecules to escape the blood. A specialized type of epithelial cell called a podocyte covers the outer surface of the capillary. The podocytes have foot processes, which are cytoplasmic extensions that help form the filtration structure. The podocyte attaches to the basement membrane, a filamentous extracellular matrix produced by the capillary cells. The gap between the foot processes, about 14 nm wide, is called a filtration slit. The fibrous basement membrane spans the filtration slits to act as the biological filter of the glomerulus, excluding blood cells and large proteins, and passing water, ions, and low-molecular-weight molecules. -The mesangial cells, similar to smooth muscle cells, wrap around the capillaries of the glomerulus. Contraction of the mesangial cells restricts blood flow to specific vessels within the capillary network, regulating blood pressure within the glomerulus and altering the surface area available for filtration. - Filtrate flows from Bowman's capsule into proximal tubule (slide)(but look at picture)

Countercurrent Multiplier

slide - Loop of Henle acts as countercurrent multiplier - Creates an osmotic gradient that facilitates reabsorption of water • Low osmolarity near cortex • High osmolarity deep in medulla -Counter-Current Multiplication Helps Create a Concentration Gradient in the Renal Medulla—transport of salts out of the ascending limb of loop of Henle is multiplied (i.e., enhanced by counter-current flow between the descending and ascending limbs of the loop of Henle. -look at all the pictures on slides TB -The loop of Henle creates a countercurrent multiplier -As we discussed the transport processes in the various segments of the tubule, we alluded to the existence of an osmotic gradient through the medulla: low osmolarity near the cortex and high osmolarity deep into the medulla (see Figure 13.26). This osmotic gradient is produced and maintained by the concerted actions and arrangement of the loop of Henle, the collecting duct, and the vasa recta. -Let's first consider how the descending and ascending flows through the loop of Henle establish the osmotic gradient within the renal medulla. This function of the loop of Henle is easiest to understand if we work backward through the tubules. The thick ascending limb of the loop of Henle actively pumps Na+ from the lumen of the tubule into the surrounding interstitial fluid, which lowers the osmolarity of the fluid within the ascending limb. The ascending limb of the loop of Henle has low expression of aquaporin genes and is thus not permeable to water, so water cannot follow the salts that are pumped out of the ascending limb. The pumping of Na+ by the ascending limb raises the osmolarity of the interstitial fluid in the medulla compared with the fluid in the descending limb of the loop of Henle. -The descending limb of the loop of Henle is permeable to water, but not to salts. Because the interstitial fluid surrounding the loop has been made more concentrated (due to the active pumping of Na+ by the ascending limb), water is drawn out of the descending limb into the interstitial fluid, until the osmolarity within the interstitial fluid and the descending limb equilibrate. The ascending limb of the loop of Henle continues to pump ions into the in- terstitial fluid, so the net effect of these processes is that the osmolarity in the interstitial fluid and in the descend- ing limb of the loop of Henle are higher than that of the fluid in the proximal tubule, and the osmolarity of the fluid in the ascending limb of the loop of Henle is lower than in the proximal tubule. This process, which is termed the single effect, results in a modest increase in the osmolarity of the renal medulla compared with the renal cortex. But establishing the very large osmotic gradient within the medulla requires another process. The loop of Henle acts as a countercurrent multiplier. -As the name suggests, the countercurrent multiplier of the loop of Henle acts to multiply the single effect to allow the renal medulla to maintain a much larger osmotic gradient than would be possible from ion pumping alone. This multiplication is possible because of the countercurrent arrangement of the descending and ascending limbs of the loop of Henle: Fluid that flows through the descending limb is traveling in the opposite direction to fluid that flows through the ascending limb. Figure 13.29 provides a conceptual example of how the countercurrent multiplier of the kidney works.

Kidney Structure and Function

slide - Mammalian kidney has two layers • Outer cortex • Inner medulla - Urine leaves kidney via ureter • Ureters empty into urinary bladder TB -The typical mammalian kidney (Figure 13.14) is crescent shaped with two layers: an outer cortex and an inner medulla. The medulla is composed of a number of parallel cone-shaped segments called renal pyramids. The inner narrow region of each pyramid is called the papilla. Once the urine is formed, it passes into a cavity called the minor calyx. -Multiple minor calyces drain into the major calyx, which in turn empties into the ureters that drain the kidney. -The ureters empty into the urinary bladder where urine is stored. -Eventually, the urine is expelled from the bladder through a single urethra, a process with the elegant name micturition. -the kidney may process 4 liters of blood per kilogram each minute but exercising muscle receives only about 0.5 liters per kilogram per minute (lab, how gut and kidneys receive a lot of blood flow but decreases tremendously during exercise)

The Kidney

slide - Most animals maintain ion and water balance using some form of internal organ - Multiple cell types combine to produce a tubelike structure - Vertebrate kidneys have six roles in homeostasis • Ion balance • Osmotic balance • Blood pressure • pH balance • Excretion of metabolic wastes and toxins • Hormone production TB -the kidney pg. 559 -Most animals maintain ion and water balance using some form of internal organ derived during the development of the embryonic digestive system. Multiple types of cells combine to produce a tubelike structure, or tubule, through which excretory solutions pass from the animal to the external environment. Animals differ in the way the tubule fluid is produced and how it is modified prior to excretion. In some animals, a few simple tubules are sufficient to produce the excretory products. More complex animals, such as vertebrates, combine tubules to form the kidney, which has six roles in homeostasis 1. Ion balance. Sodium levels are an important determinant of extracellular fluid osmolarity. Potassium balance is important because changes in [K+] can alter resting membrane potential, which affects the function of excitable tissues such as muscles and neurons. If blood [K+] is too high (hyperkalemia), excitable tissues can undergo spontaneous depolarization, causing cardiac arrhythmias and muscle twitches. Low [K+], or hypokalemia, can cause muscle weakness. The kidney also controls the loss of ions that have important roles as micronutrients, including Ca2+, iron, and trace metals. 2. Osmotic balance. The kidneys determine the volume of urine produced, and thereby control water balance. Dehydration results from inadequate consumption of water, or consumption of chemicals known as diuretics, which in- crease water loss in the urine. Conversely, inadequate water excretion can result in high blood pressure and edema. 3. Blood pressure. By controlling blood volume, the kidney acts over the long term to regulate blood pressure. It acts in concert with shorter term cardiovascular effectors, such as cardiac contractile properties and peripheral resistance of the vasculature. The volume of the extracellular fluid is under the control of the kidney, through hormones and nerves that integrate cardiovascular conditions with the output of the central cardiovascular control center. 4. pH balance. The kidney augments the respiratory system in control- ling the pH of body fluids. The kidney regulates the pH of the extracellular fluid by retaining or excreting H+ or HCO3−. Many of the metabolic and transport pathways of ammonia metabolism also involve acid or base production. The production of urea leads to the consumption of bicarbonate, which also has consequences for whole- body pH regulation. 5. Excretion. The kidney plays an important role in the excretion of nitrogenous wastes as well as other water-soluble toxins. Excess water- soluble vitamins, for example, are excreted in the urine. 6. Hormone production. The kidney has an important role in the synthesis and release of hormones, such as renin, which controls blood pressure, and erythropoietin, which regulates red blood cell synthesis.

Complete Digestive Tract

slide - One-way gut (gastrointestinal tract) • Specialized regions • Mouth, pharynx, esophagus- Mechanical breakdown of food • Stomach- Acidic compartment • Upper or small intestines- Digestion and absorption • Lower or large intestines- Absorption of water • Anus- Release of indigestible material TB -With some exceptions, other animals possess some form of gastrointestinal tract, the complexity of which grows with the evolution of the three cell layers and an internal coelom.

Reabsorption

slide - Primary urine • Initial filtrate filtered in Bowman's capsule that is isosmotic to blood - Most water and salt in primary urine reabsorbed using transport proteins and energy • Rate of reabsorption limited by number of transporters • Renal threshold. Concentration of a specific solute that will overwhelm reabsorptive capacity - Each zone of the nephron has transporters for specific solutes TB -The primary urine is modified by reabsorption and secretion -The primary urine that is formed by filtration is essentially isosmotic to blood (about 300 mOsM). As the fluid passes through the tubule, about 99 percent of the volume is recovered. For example, an average-sized human produces about 7.5 liters of primary urine each hour, but generates only about 75 ml of final urine. The remodeling of the primary urine occurs as it passes through successive regions of the tubule, each with specialized transport capacities. Recall that the tubule wall is composed of a single layer of epithelial cells. Like most epithelial cells, the apical membranes (facing the lumen) and basolateral membranes (facing the interstitium) have specialized profiles of transporters. Also, the cells of the epithelium may be interconnected in ways that form a tight epithelium or a leaky epithelium. -Recovery of substances from the lumen of the tubule requires a favorable electrochemical gradient and appropriate transport capacities. Some substances in the primary urine are reclaimed by transepithelial transport, moving from the lumen of the tubule, across the single layer of epithelial cells, into the interstitial fluid (peritubular fluid), and ultimately back into the blood. Some hydrophobic solutes cross the tubular epithelium by passive transport; as water is removed from the primary urine, concentration gradients are created that can drive hydrophobic solutes back to the blood. Larger molecules in the filtrate, such as small proteins, can be recovered by transcytosis: endocytosis into the epithelial cell and exocytosis into the interstitial fluid. Most molecules, however, are reabsorbed through a combination of facilitated diffusion and active transport, both primary and secondary. -The ability to reabsorb solutes such as glucose is limited by transport capacity. Like many active transporters, the kinetics of the transport machinery can become saturated at high substrate levels (Figure 13.22). This capacity for solute recovery is known as the renal threshold. If the amount of substance to be recovered is in excess of the capacity of the transport machinery, some of the substance will escape in the urine. (continuation on next flashcard, they go hand in hand)

Blood flow to the kidney

slide - Renal arteries are short, large diameter arteries that branch directly off the abdominal aorta. This maximizes blood flow to the kidneys because: -Why is this important? TB -nothing? -we might have already gone over it when talking about the nephron and the picture with blood vessels personal notes on slides: -"because:..." the equation BF=Q= look for equation here shorter blood vessel= increase in blood flow "why is this important?"... because all blood needs to go through the kidney to excrete wastes (urea)

Reabsorption of Glucose

slide -Glucose is reabsorbed by secondary active transport -Reabsorbed molecules taken up by the blood TB continuation of what was above (they go hand in hand) -Consider how cells reabsorb sodium and glucose (Figure 13.21). The concentrations of Na+ and glucose in the primary urine are not different from that of the blood, so the challenge is how to recover these solutes in the absence of favorable concentration gradients. The major driving force underlying the transport is the Na+/K+ ATPase found in the basolateral membrane. By pumping Na+ out of the cell into the interstitial fluid, the nephron cells create a favorable inward Na+ electrochemical gradient on the apical side that can be used to drive both Na+ uptake and Na+-coupled glucose uptake. Na+ can cross into the tubule cells by a Na+ channel, Na+/H+ exchanger, or by suites of other carriers that couple the import of organic molecules and Na+, including the Na+-glucose cotransporter. Concentrating glucose inside the cell creates a favorable outward chemical gradient for glucose; glucose permease allows glucose to cross into the peritubular interstitial fluid via facilitated diffusion. Each of these transport processes requires energy, either in the form of ATP used by the primary active transporters (for example, Na+/K+ ATPase) or in the form of electrochemical gradients used by secondary active transporters (for example, the Na+-glucose cotransporter). -The ability to reabsorb solutes such as glucose is limited by transport capacity. Like many active transporters, the kinetics of the transport machinery can become saturated at high substrate levels (Figure 13.22). This capacity for solute recovery is known as the renal threshold. If the amount of substance to be recovered is in excess of the capacity of the transport machinery, some of the substance will escape in the urine.

Structure of the kidney

slide -picture *try to know the different structures

vasa recta

slide -picture FIGURE 13.16 Blood vessels of the nephron Blood delivered to the kidney by the renal artery passes through smaller arteries and reaches an afferent arteriole that services one nephron. The arteriole diverges into the glomerulus, a network of capillaries within the Bowman's capsule. After leaving the glomerulus, blood enters an efferent arteriole. The efferent arterioles that drain cortical nephrons empty into peritubular capillaries. The efferent arterioles that drain juxtaglomerular nephrons flow into the vasa recta. TB The vasa recta maintains the medullary osmotic gradient via a countercurrent exchanger -The osmotic gradient may arise along the depth of the medulla through the movement of salts and water between the tubule and the interstitial fluid, but it is maintained because the vasa recta (see Figure 13.16) works as a countercurrent exchanger.2 In most tissues, capillaries drain the interstitium, collecting solutes and water and emptying them into the blood. The vasculature in the medulla is arranged in a way that it can meet the circulatory needs (O2 delivery, CO2 removal) with- out disrupting the osmotic gradient. Consider what would happen if the blood vessels flowed unidirectionally from the cortex through the medulla and out of the kidney; the blood would draw fluids and solutes out of the kidney, rapidly dissipating the gradient created within the medulla. Instead, the vessels of the vasa recta carry blood into the medulla, then back out of the medulla. As blood leaves the efferent arteriole and enters the vasa recta, it is carried into the medulla, where the higher osmolarity causes it to passively pick up solutes and lose water. As the vessels head back toward the cortex, the decreasing osmolarity causes the blood to lose solutes and gain water. The blood vessels exit the kidney at the junction between cortex and medulla, where interstitial fluid is isosmotic to blood. Thus, the countercurrent arrangement of the vasa recta ensures that the osmotic gradient within the medulla is maintained.

Type I Diabetes Mellitus

slide -picture (look at slides) my personal notes: -cannot make enough insulin. target beta cells destroy - A= low - B= high - C= really high. sugar levels go up. goes to kidney in capillaries it leaks out? TB (continuation from previous 2 flashcards) -In type 1 diabetes, the levels of glucose can be very high in the blood. When the blood is filtered by the glomerulus, the primary urine also has a very high glucose concentration. Despite the active glucose transporters, the kidney cannot reabsorb all of the glucose, and some is lost in the urine (glucosuria). extra info (but know just in case) (below) -The other way the primary urine is modified is through secretion. Secretion is similar to reabsorption in that it uses transporters found in the cells that line the lumen. However, the process works in the opposite direction, transferring solutes from the blood, through the peritubular fluid, and across the cells into the tubule lumen. The most important secretory products are K+, NH4+, and H+. Many water-soluble waste products are also secreted into the tubule, including pharmaceuticals and water-soluble vitamins. Like other active transport processes, secretion depends on transport proteins and requires energy.

enzymes

slide • Catalysts that accelerate chemical reactions - Enzymes have three properties 1. Activate at low concentrations 2. Increase the rate of reactions but are not altered 3. Do not change the products - Most are made of proteins • Some are made of RNA (ribozymes) note -Protein function if often facilitated by non-protein accessory molecules generally referred to collectively as cofactors. These may be metal ions, prosthetic groups, or coenzymes. Many vitamins function as coenzymes. TB -Enzymes are biological catalysts that convert a substrate to a product. Enzymes, like other types of catalysts, have three properties: (1) they are active at very low concentrations within the cell; (2) they increase the rate of reactions but they themselves are not altered in the process; (3) they do not change the nature of the products. -Although some enzymes, called ribozymes, are made of RNA, most enzymes are composed of protein.