Anatomy Exam #3

What are pH imbalances called that are not due to respiratory system malfunction, but are due to other issues, and how would you recognize these imbalances? What are some issues that can cause this?

- "Metabolic" pH imbalances include all of the acid-base imbalances caused by anything other than abnormal CO2 levels. - Metabolic acidosis can be caused by things like increased acid production from excessive exercise (lactic acid), metabolism of fats (ketoacidosis) or loss of bicarbonate ion in diarrhea - Metabolic acidosis is characterized by low pH and low HCO3 - levels - Bicarbonate levels are low because bicarbonate ions are used up trying to buffer the high levels of H+ (from the acids). - Metabolic alkalosis can be caused by vomiting (loss of stomach acid) or excessive antacid use. It is characterized by increased pH and increased HCO3 - levels

Flow of urine through the organs of the urinary system

- A minor calyx surrounds the renal papillae of each pyramid and collects urine from that pyramid. Several minor calyces converge to form a major calyx. From the major calyces, the urine flows into the renal pelvis - Renal pelvis - funnel shaped tube drains into ureter - collects all urine - Ureter - carry urine from kidney to bladder - composed of 3 layers (mucosa composed of transitional epithelium & lamina propria, muscularis - Urine stretches muscularis layer - stimulates peristaltic waves of contraction which propels urine toward bladder , adventitia - outer CT layer holding ureter in place) - Urinary bladder - stores urine (very distensible), has rugae when empty - also 3 layers (mucosa w/ transitional epithelium, muscularis/detrusor muscle, adventitia/serosa) muscular wall called the detrusor muscle stretches and thins allowing for increased storage w/o increasing internal pressure - trigone: triangular region formed by openings of ureters and urethra, may be site of persistent infections - Urethra - conveys urine out of the body (2-3 cm in women; 20 cm in men w/ 3 regions - prostatic, membranous and spongy regions) - Internal urethral sphincter: smooth muscle, involuntary/controlled by ANS - External urethral sphincter: skeletal muscle, voluntary/controlled by somatic NS

Difference between a strong base and a weak base

- A stron base dissociates completely into its components - e.g. NaOH will dissociate into Na+ and OH- (hydroxide ions) - the hydroxide ions will join with the free hydrogen ions in solution, forming water - this will decrease the concentration of hydrogen ions in the solution, and OH- will predominate, increasing the pH (making it more basic) - A weak base usually exists in solutions as salt - it can partially dissociate and accept H+ to form more carbonic acid - Bases are proton acceptors (bind H+)

How do weak acids and weak bases help to resist changes in pH?

- A weak acid, like H2CO3 (carbonic acid), releases its H+ to resist an increase in pH. A weak base, like HCO3- (bicarbonate ion) accepts H+ ions to resist changes in pH. - In a buffering system the weak acid buffers the strong base by pairing its H to the OH to form water and a weak base. The weak base buffers the strong acid by pairing with its H to form a weak acid.

What is the medullary osmotic gradient

- AN increase in the concentration of solutes (osmolarity) in the interstitial spaceas you go deeper in the renal medulla - this increasing osmotic gradient extends through the renal medulla - the gradient starts at the cortical-medulla junction at 300 mOsm (isotonic to the blood) and increases in osmolarity as you move deeper in the medulla - Summary in numbers - 300 -> 300 -> 300 -> 300 -> lost water on the way down so filtrate becomes more concentrated (1200) -> pumped out salt on the way up so filtrate becomes more dilute (100)

Vessels of nephron

- Afferent arteriole - carries blood into the glomerulus (flow and pressure can be affected from either side) - Efferent arteriole leads out of glomerulus and drains into peritubular capillary bed (cortical nephrons) - In juxtamedullary nephrons, efferent arteriole drains into vasa recta - Vasa recta - low pressure capillary beds which favor exchange of substances from interstitial spaces around tubule

Nephron

- Basic structural and functional unit of the kidney - contained in cortex (renal corpuscles, proximal & convoluted tubules) and medulla (straight structures - loop od henle, collecting ducts & vasa recta) consists of 2 parts: - Renal corpuscle - responsible for filtering the blood and forming a "pre-urine" - composed of the glomerulus (a capillary bed) inside a cup-shaped capsule (Bowman's capsule - parietal layer=simple squamous - visceral layer = podocytes) - Renal tubule - continuous w/ renal corpuscle and adjusts contents of pre-urine to form urine - its long length increases processing capability (Removes 99% of water from pre-urine and returns it to the blood (concentrates urine) - adjusts ion levels - adjust pH) - proximal convoluted tubule: leads out of glomerular capsule - loop of henle: descending limb into medulla, ascending limb back to cortex - distal convoluted tubule: leads to collecting duct - Multiple nephrons empty into one collecting duct (which completes modifications of urine and each renal pyramid will have many collecting ducts

Protein buffer system

- Buffers ICF and plasma - Some amino acids have exposed side chains (R group) composed of either acid (carboxyl) groups or amine groups that can donate or accept H+ allowing it to function as a weak acid or base as needed - When pH begins to rise: (R-COOH -> R-COO- + H+) - In the presence of an acid (pH drops): (R-NH2 + H+ -> R-NH3+) -Works inside cells or in plasma: H+ buffering by hemoglobin in RBCs and H+ buffering by plasma proteins in plasma

CCK & secretin

- CCK is released by enteroendocrine cells in the duodenum following activation of chemoreceptors that sense proteins and fats in the chyme - once released CCK will increase secretion of pancreatic juice by acinar cells, initiate gallbladder contraction & relax the hepatopancreatic sphincter allowing pancreatic juice & bile to enter the duodenum - Secretin is also released by enteroendocrine cells in the duodenum, but is stimulated by chemoreceptor that are activated by increased acidity, or decreased pH - works primarily at the pancreas to increase the secretion of HCO3 from duct cells

Pulmonary disease/ respiratory system dysfunction lead to pH changes in body

- CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3 - Shallow, slow breathing or impaired pulmonary gas exchange (as in emphysema, COPD, cystic fibrosis), will lead to a buildup of CO2 in the body. CO2 levels lead to H+ formation (as described in the above relationship). Increased H+ leads to more acidic blood or acidosis when the arterial blood pH drops below 7.35. This is called respiratory acidosis because it is caused by a malfunction of the respiratory system - Rapid, deep breathing blows CO2 out of the blood and lungs. When this happens, H+ is decreased (the above equation shifted to left), so the blood pH becomes more alkaline. If blood pH is > 7.45, this is considered alkalosis. Alkalosis caused by respiratory system malfunction is called respiratory alkalosis. - pH imbalances caused by respiratory system dysfunction can't be solved by the respiratory system (by changing breathing patterns). Instead renal mechanisms (kidney) try to compensate for respiratory system imbalances

Three phases of gastric secretions

- Cephalic phase - occurs before food enters the stomach - stimulated by the sight, smell or thought of food - these events activate the cerbral cortex which causes increaed Parasympathetic activation through the vagus nerve, which stimulate increased gastric juice secretions - can be inhibited by loss of appetite or depression & is manifested as reduction in parasympathetic activity to the stomach (decreased prod. of gastric juice) - Gastric phase - initiated when food enters the stomach - increased stretch of the stomach wall activates stretch receptors which initiates both intrinsic (short) an extrinsic (long) reflexes to initiate gastric juice secretion - The long reflexes activate the vagus nerve again (parasympathetic), the short reflexes are mediated by nerve plexuses within the wall of the stomach which make up the enteric nervous system - chemicals present in the food will also activate chemoreceptors which can activate enteroendocrine cells. Of particular interest is the activation of the G cell, which will stimulate parietal cells to increase the production of HCl when the pH in the lumen starts to get too high (alkaline). Proteins in the stomach will buffer acid and raise the pH, and this stimulates more production of gastrin (which will stimulate more gastric secretions, including more acid production by parietal cells). The gastric phase is inhibited by excessive acidity which results in inhibition of G cells. If the pH drops below pH 2, less gastrin is produced, and secretions of HCl by parietal cells are decreased as well. Emotional stress or anything that triggers the fight and flight response activates the sympathetic nervous system which also decreasing gastric activity. Activation of the sympathetic division overrides any parasympathetic nervous system activity. - Intestinal phase - stimulation is activated by the presence of partially digested food in the duodenum resulting in the release of intestinal gastrin from enteroendocrine cells of the SI - briefly continues stimulating gastric juice production - once more chyme starts entering SI, gastric secretions are inhibited through short & long reflexes (called enterogastric reflex designed to make sure SI doesn't get overwhelmed by too much chyme entering SI too fast - decreases gastrin release & gastric contractions as well as constricting pyloric sphincter

Stomach mucosal barrier

- Chemical barrier that protects te wall of the stomach from the highly acidic gastric juice - Established by the secretions of the surface mucus cells that release mucus and bicarbonate ions - the mucus builds up on the surface of the epithelial cells, separating the acidic contents of the lumen from the cells underneath - The bicarbonate secretions form a layer between the mucus and epithelium and helps neutralize the acid near the surface of the epithelium. - The mucosal barrier is aided by the tight junctions that exist between the epithelial cells which prevents any gastric juice from passing through the epithelium to the layers below - The epithelial cells are also quickly replaced by dividing stem cells.

Characteristics and components of urine

- Color: indicator of hydration, blood in urine - pH: affected by diet (high protein - acidic urine; vegetarian - alkaline) - Smell: diabetics may have sweet smelling urine - Turbidity: normal is clear - increased turbidity due to suspended particles - due to cells, urinary tract infections - Constituents: water, urea, salts, pigments - Normal urine composition: 95% water and 5% solutes § Nitrogenous wastes: § Urea - derived from normal breakdown of amino acids § Uric acid - end product of nucleic acid metabolism § Creatinine - breakdown product of creatine phosphate Normal solutes (in order of decreasing concentration: § Urea, Na+, K+, PO43-, SO42-, creatinine, uric acid; § less: Ca2+, Mg2+, HCO3- - Abnormal urine composition: Plasma proteins, RBCs,WBCs, bile pigments may indicate pathology

Pancreatic juice

- Contains digestive enzymes - some of which are release in inactive forms (zymogens - so not to destroy pancreas while in transit) and bicarbonate - produced & released from acinar cells of exocrine part of the pancreas --> release enzymes into the ducts which will convey enzymes to the large main pancreatic duct - The cells that line the small branches of ducts closest to the acinar cells secrete bicarbonate and water to help transport the enzymes - The inactive forms of the enzymes will be activated within the lumen of the small intestine, and they will digest food into smaller nutrients. Proteases digest (break down) proteins into smaller peptides and amino acids, amylase digests starch into smaller oligosaccharides and disaccharides (chains of sugar molecules), lipases digests fats, and nucleases digest nucleic acids. The bicarbonate that's released with the pancreatic juice helps to neutralize the acidic chyme.

Two types of nephrons

- Cortical nephron -Almost entirely in the cortex with just a little part of the loop of henle dipping into the medulla - 85% of all nephrons - Filter blood to make 'filtrate' - Juxtamedullary nephrons - renal corpuscle located near the cortex-medulla junction - · Loop of Henle dips deep into the medulla - Primary role is to establish osmotic gradient in kidney to make it possible to concentrate urine

Countercurrent mechanism

- Creates an osmotic gradient through interactions of the two limbs of the nephron loop - occurs when fluid flows in opposite directions through adjacent segments of the same tube - these segments are parallel to each other, usually because of a hairpin turn in the tube (nephron loop) - The nephron loop of j-m nephrons is called a "countercurrent multiplier" because the actions of each of the limbs of the loop "multiplies" the effects of the other limb. Pumping salt out of the ascending limb makes it more likely water will leave the descending limb by osmosis. Water leaving the descending limb increases the osmolarity of the filtrate in the loop, which drives the pumping of salt out of the ascending limb of the loop

Dietary sources, uses in the body and considerations of carbohydrates

- Dietary Sources: sugars (mon- & disaccharides), most from plants (fruits, sugar cane, sugar beets, honey, (exception: milk sugar) - starch (polysaccharides include grains and vegetables - Glycogen - negligible amount from meats - Uses in the body: · Glucose - the body's main fuel source for ATP production - Brain & red blood cells use glucose for energy - used or storage (glycogen and/or fat) - other monosaccharides converted to glucose in liver - pentose sugars in RNA, DNA, sugars in glycocalyx - polysaccharides are sources of fiber- insoluble fiber - increases the bulk of the stool to improve defecation (provides the roughage required in our diet to keep our colon healthy - soluble fiber - helps control cholesterol and blood sugar levels - Dietary considerations - 45-65% total calorie intake is from carbs (ideally complex carbs) · Get plenty of fiber (25-30 gm/day) · Highly processed carbs (candy, soda) - concentrated energy source without benefits of other nutrients (empty calories)

Dietary sources, uses in the body and considerations of proteins

- Dietary sources: complete proteins - contain all the essential amino acids for tissue maintenance and growth (eggs, milk, fish, most meats, soybeans) - Incomplete proteins lack one or more essential amino acid (legumes like peas & beans, nuts, cereal grains) - Uses in the body: Proteins provide important structural materials such as keratin (skin), collagen and elastin (connective tissues) and muscle proteins. Proteins are also important functional molecules such as enzymes, hormones and membrane transport proteins - they are also used for ATP production when not enough carb or fat calories in diet - Nitrogen balance: rate of protein synthesis equals rate of protein breakdown and loss - positive balance during growth, pregancny; negative balance during stress starvation - Dietary considerations: · Will vary based on age, size, metabolic rate and need (state of nitrogen balance); generally, ~0.8 gm/kg body weight - need to get essential amino acids from diet · Gluten sensitivity - celiac disease (genetic) - gluten breakdown products stimulate T cells that attack epithelium - damage villi, decrease surface area for absorption - malabsorption

protein digestion and absorption

- Digestion - begins in the stomach by pepsin, and is complete by the end of the SI in the presence of pancreatic enzymes - digest proteins into small peptides and these small peptides are broken down into individual amino acids by brush border enzymes embedded in the icrovilli on the apical surface of enterocytes - Absorption - transported into enterocytes by sexondary active transport on the apical surface, are transported across the basolateral membrane by carrier mediated facilitated diffusion, and enter blood capillaries in the lamina propria of the villi.

Fat digestion & Absorption

- Digestion - digested by lipases (most digestion occurs in SI) - since fats are hydrophobic they form large fat globules in an aqueous environment like chyme - emulsification of these fat droplet by bile salts in bile help to break the fat droplets into smaller fat droplets so that lipases have better access to the fats (triglyceride molecules) that will be digested - after bile emulsifies fat droplets, lipases cleave triglycerides into 2 fatty acid chains and one monoglyceride -> because these are still nonpolar, bile salts and phospholips in bile form micelles around the fatty acids and monoglycerides and transport them through the aqueous environment to the microvilli - Absorption - (simple diffusion) lipids leave the micelles and cross the lipid bilayer into the cell. Inside the cell the fatty acids and monoglycerides are converted back to triglycerides. They are then combined with phospholipids and cholesterol and coated with a skin of proteins to form water soluble chylomicrons which are released from the cell by exocytosis and enter the lacteals to travel through the lymph system and then back into the bloodstream. (Chylomicrons are too big to be absorbed or transported through plasma membrane or directly into blood capillaries). While in bloodstream, triglycerides of chylomicrons are hydrolyzed to free fatty acids and glycerol by lipoprotein lipase, and enzyme associated with capillary endothelium. The fatty acids and glycerol can then pass through the capillary endothelial walls to be used by tissue cells for energy or stored as fats in adipose tissue (fat is absorbed into the lymph)

carbohydrate digestion & absorption

- Digestion: starts in the mouth with amylase (in mouth - salivary glands) converting polysaccharides to disaccharides, continues with pancreatic amylase in SI, finishes with sucrase/maltase/lactase from the small intestine converting disaccharides to monosaccharides (glucose/fructose/galactose) - Absorption: Monosaccharides are transported into enterocytes by secondary active transport on the apical surface, diffuse across the cytoplasm of the cell and are transported across the basolateral membrane by carrier mediated facilitated diffusion - The monosaccharides can enter the blood capillaries in the lamina propria of the villi by passing through the intercellular clefts between the endothelial cells that form the capillary epithelium

Phosphate buffer system

- Dihydrogen phosphate (H2PO4) acts as a weak acid that can release H+ ions in the presence of a strong base; and monohydrogen phosphate (HPO4) acts as a weak base that can accept H+ ions - Important buffer in urine and ICF Where phosphate levels are high) - will help ensure excretion of H+ ions in urine

Major cations and anions of ECF and ICF and why HCO3- and HPO4- are important

- ECF - major cation is Na+; major anions are Cl- and HCO3- - ICF - major cation is K+; major anions are HPO4- and negatively charged proteins - HCO3- (bicarbonate) and HPO4- are important because they are weak bases that will participate in the chemical buffering systems to resist changes in pH.

Electrolytes & nonelectrolytes

- Electrolytes (like NaCl) are compounds that dissociate into ions when placed in a solvent like water. Because the ions are charged particles, they conduct electricity. - Non-electrolytes are compounds that are formed by bonds (like covalent bonds) that prevent them from dissociating in a solution. Glucose is an example of a nonelectrolyte. It dissolves easily in solution, but it doesn't dissociate into its component parts.

5 cell types of the epithelium of the SI

- Enterocytes - bulk of epithelia: simple columnar absorptive cells responsible for absorbing the nutrients and have microvilli (brush border) on their apical surface - located on the villi and in the crypts (intestinal crypts or intestinal glands) - Goblet cells produce mucus and are found on both the villi and crypts - Enteroendocrine cells are responsible for secreting enterogastrones (hormones like CCK & secretin) and are mostly located in the intestinal crypts but can be found on villi also - Paneth cells are secretory cells located in the crypts that release antimicrobial agents that help control bacterial populations in the intestinal lumen - Stem cells are continuously dividing cells in the crypts that help replace all four cell types

How enteroendocrine cells differ from other secretory cells in the GI tracts

- Enteroendocrine cells secrete hormones into the lamina propria, instead of into the lumen of the GI tract organ like the other secretory cells do. Once the hormone is released into the lamina propria, it can effect a nearby cell, or enter the bloodstream and travel throughout the body to effect target cells that have receptors for that particular hormone. - Enteroendocrine cells release their hormones in response to the contents of the chyme in the lumen of the GI tract. For example, enteroendocrine cells can sense solute concentrations (increased proteins or fats) or acidity of the chyme

Extrinsic and intrinsic control of digestive activity

- Extrinsic- involves the central nervous system - influence can be observed in two ways: First, the activation of the receptors in the alimentary organs activates visceral afferent nerve fibers that modulate activity in the CNS - This long reflex can result in activation of the sympathetic or parasympathetic nervous systems, which will modulate the activity of the enteric neurons. - The second influence of the extrinsic controls is directly through the CNS and does not involve any initial input from the alimentary organs. In this case external stimuli like smell, sight or taste can activate neurons in the CNS that will activate the sympathetic or parasympathetic fibers that innervate the digestive organs resulting in a modulation of contractile or secretory activity - Intrinsic control of digestive activity involves only the enteric nervous system and receptors of the organs in the alimentary canal - Stimuli in the organs cause activation of chemoreceptors, osmoreceptors, and/or mechanoreceptors, which modulate the activity of neurons in the submucosal and myenteric plexuses - The local neuronal activity effects the activity of smooth muscles and glands resulting in a change of contractile or secretory activity

Filtration membrane

- Filtration is a passive process moving fluid and solutes from blood, through the filtration membrane and into capsular space - 3 layers: - 1)Fenestrated endothelium of glomerular capillary (allows passage of everything but blood cells) - 2)Basement Membrane (repels negatively chared macromolecules/plasm proteins - 3)Filtration slits between the foot processes of podocytes (visceral layer of glomerular capsule) - Anything smaller than 3nm (water, glucose, amino acids, drugs) easily passes through membrane Anything larger than 5nm stays in the capillary - maintains the osmotic pressure of blood, preventing loss of all water to capsular space - Blood cells and plasma proteins DO NOT CROSS the filtration membrane!

Gall bladder

- Function: store and concentrate bile that is produced in the liver - When bile is released from the liver (through the hepatic ducts), it travels down toward the small intestine. If the hepatopancreatic sphincter is closed, the bile can't enter the small intestine, and backs up in the common bile duct. It enters the gall bladder through the cystic duct and is stored there until it is released - When the enteroendocrine cells of the duodenum sense proteins and fat in the chyme, they release cholecystokinin or CCK. CCK causes gall bladder contraction, which will release bile, and also causes relaxation of the hepatopancreatic sphincter, so that the bile can enter the SI.

Three major renal (urinary) processes responsible for urine formation

- Glomerular filtration - dumps cell-free and protein-free blood filtrate into the container (glomerular capsule or Bowman's capsule) - Tubular reabsorption - reclaims what the body needs to keep (from tubule to the blood - Tubular secretion - selectively adds to the filtrate (from blood to tubule)

ultrafiltrate

- High pressure blood entering glomerular capillary bed is filtered through the walls of the fenestrated capillary producing an ultrafiltrate of plasma - the fluid resulting from the initial filtration of metabolic by-products from the filtered blood within the tubule of the kidney

Forces that promote or oppose glomerular filtration and fluid flow

- Hydrostatic pressure - pressure of fluid against walls of a vessel - Can be in blood vessel (capillary) or capsular space (promote) - Osmotic (oncotic) pressure - pressure exerted by particles (proteins) in the blood (or fluid) which tend to 'pull' water into the vessel or space (oppose) - The sum of all opposing forces determines the net pressure in a system

Fluid movement of solutes and water in the body and how hydrostatic and osmotic pressure relate

- Hydrostatic pressure - pressure of fluid in a system (like a capillary) - Osmotic pressure - the pressure exerted by the concentration of solutes in a solvent, which causes water to move into an area of higher solute concentration - These pressures control fluid movement by pushing a fluid out of one space and into another across a membrane (hydrostatic pressure) and drawing fluid out of a less concentrated environment into a more concentrated environment across a membrane (osmotic pressure) - In the ECF and ICF, water will move to maintain osmotic equilibrium. If the concentration of solutes is high inside the ECF, water will leave the ICF (leave cells) to balance the osmolarity. This water movement will increase the volume of the ECF and decrease the volume of the ICF. If the concentration of solutes is low in the ECF, water will leave the ECF and enter the ICF (enter cells). This might lead to cell swelling. - Anything that changes solute concentration in a compartment leads to water (water follows solutes almost always)

hypotonic, isotonic & hypertonic solutions solution

- Hypotonic - A solution in which the concentration of solutes is less than that of the cell that resides in the solution - Isotonic - when the concentration of two solutions is the same - Hypertonic - concentration of solutes is greater than that of the cell that resides in the solution

Zygomens

- Inactive enzymes like trypsinogen & chymotrypsinogen - once in the ducts they are delivered to duodenum to be activated by enzyme enteropeptidase which is embredded in the apical membrane of SI epithelial cells - Enteropeptidase activates trypsinogen by cleaving off a small peptide fragement, which converts trypsinogen to its active form, trypsin - Enterokinase can continue to activate more trypsinogen, but the active trypsin can also activate more zymogen enzymes which will start digesting the foodstuffs in the chyme

6 essential digestive functions & processes

- Ingestion - taking in food and water via the mouth - Propulsion - movement of food/water by swallowing or peristalsis - alternating waves of contraction of smooth muscle - Mechanical breakdown - increases surface area of food, preparing for chemical digestion by enzymes - In mouth - chewing, tongue mix food with saliva - Churning - pummeling of food in stomach - Segmentation - back and forth movement in SI - Digestion - enzymes secreted into lumen break food into chemical building blocks (catabolic process) - Absorption - movement of nutrients from lumen to blood or lymph - Defecation - elimination of solid waste (feces): indigestible substances and metabolic wastes

Defecation reflex

- Initiated when feces move into the rectum and distends the walls, activating stretch receptors --> activation of stretch receptor sends nerve impulses via sensory nerve fibers to spinal cord that activates the parasympathetic spinal reflex - A spinal reflex is initiated in which parasympathetic motor (efferent) fibers stimulate contraction of the rectum and sigmoid colon and relaxation of internal anal sphincter - IF it is convenient to defecate, voluntary motor neurons are inhibited, allowing the external anal sphincter to relax so feces may pass

2 main fluid compartments and which contributes the greatest percent to the fluid in our body

- Intracellular fluid (ICF) - (2/3) most of fluid in the body is in the intracellular fluid compartment - Extracellular fluid (ECF) - (1/3) broken down into the plasma (in blood) and the interstitial fluid (IF) in the spaces between cells

Stomach

- J-shaped temporary "storage tank" that aids in chemical and mechanical digestion (convert bolus to chyme), propulsion of food - can hold ~1 gallon of food - The mucosa of the stomach has gastric pits and gastric glands, the muscularis externa has 3 layers of smooth muscle instead of just 2 layers, and the mucosa/submucosa has special longitudinal folds called rugae. - The cells of the gastric glands secrete gastric juice which is important for the function of the stomach. The epithelial cells secrete mucus which helps protect the stomach from acid - The gastric juice contains hydrochloric acid (to denature proteins and activate pepsinogen), pepsin (a protease to begin the digestion of proteins) and intrinsic factor (help absorb Vitamin B12 in intestine) - Enteroendocrine cells of the gastric glands secrete gastrin and histamine into the lamina propria, which help increase the production of gastric juice. - The 3 layers of smooth muscle help create a special form of peristalsis that is very powerful and helps with the mechanical breakdown of food in the stomach and helps in mixing of food with gastric juice. The back and forth actions created by the force of contractions helps break up solids - Serosa - covered by visceral peritoneum - allows stomach to move freely without friction across neighboring organs - The rugae are temporary longitudinal folds in the mucosa and submucosa of the stomach - When the stomach begins to fill the rugae can flatten out increasing the volume of the stomach allowing it to accommodate up to a gallon of food - Pyloric sphincter controls entry of chyme into small intestine

Urinary system organs

- Kidneys - filter blood and form urine - Ureters - long muscular tubes that transport urine from kidneys to urinary bladder - Urinary bladder - muscular organ that stores urine - Urethra - tube that transmits urine from bladder to exterior

Location and layers of kidney

- Kidneys are retroperitoneal in the superior lumbar region surrounded by 3 layers of supportive tissue: - Fibrous capsule - thin layer of dense regular connective tissue surrounding kidney - Renal fascia - outer dense fibrous connective tissue anchoring the kidney to surrounding structures - Perirenal fat capsule - fatty mass that protects kidney

Small intestine

- Main location of digestion and absorption - Duodenum(12 in) - most digestion, alkaline & mucus secretions to neutralize acidic chyme; retroperitoneal - Jejunum (8 ft) - a lot of absorption; intraperitoneal, suspended by mesentery - Ileum - (12 ft) - absorption vitamin B12, bile salts, peyer's patches; intraperitoneal, suspended

General processes that occur in the stomach

- Mechanical breakdown (churning), chemical digestion (pepsin - protease; HCl denatures proteins), propulsion (peristalsis), secretion: mucus, pepsinogen, HCl, intrinsic factor, gastrin, histamine; absorption (minor) - not much absorption, but two lipid soluble substances - alcohol and aspirin are absorbed across the stomach mucosa into the blood.

Layers of the alimentary canal (tissue composition & function)

- Mucosa - innermost layer - secrete mucus, digestive enzymes and hormones - absorb the end products of digestion into the blood - protect against infectious disease - this is the protective barrier of the alimentary canal - 3 sublayers: epithelium (simple columnar rich in mucus secreting cells), lamina propria (loose areolar connective tissue w/ lymphoid follicles), muscularis mucosa (thin smooth muscle layer) - Submucosa - areolar connective tissue w/ blood vessels, lymphatic vessels, lymphoid follicles, nerve fibers, glands; location of submucosal plexus - Muscularis externa - main muscle layer - functions in segmentation & peristalsis (churning of stomach) - 3 sublayer: inner circular smooth muscle (can contribute to sphincters), outer longitudinal smooth muscle, in between is the myenteric plexus - Serosa - visceral peritoneum - areolar connective tissue with mesothelium (simle epithelium) - adventitia if no peritoneum (dense connective tube)

4 cell types located in the gastric pits & gastric glands

- Mucus cells - lines the epithelial surface of the stomach & the walls of the gastric pits - secrete mucus & bicarbonate to protect stomach wall from acidic gastric juices - - Parietal cells - located in gastric glands and provide 2 vital secretions: intrinisc factor (required for intestinal absorption of vitamin B12, which is required for RBC production) & hydrocholirc acid (helps denature proteins in the stomach, provides protection from bacteria & microorganisms and facilitates the activation of pepsin from the inactive enzyme pepsinogen) - Chief cells - located in the gastric glands & secrete pepsinogen (inactive form of the protease pepsin) - the secretions then flow into the lumen of the stomach - Enteroendocrine cells - cells that release hormones into the lamina propria & then the bloodstream to influence other cell behavior - Some secreted chemicals act as paracrine (local acting) or as hormones, entering the blood supply - a common enteroendocrine cell in the stomach is the G cell which secretes the hormone gastrin (gastrin is important in stomach function because it stimulates secretions from parietal cells and it causes secretion of histamine from other enteroendocrine cells in the stomach) - o Both gastrin and histamine have synergistic effects on HCl secretion from parietal cells - Gastrin increases gastric secretions and gastric motility.

Regulation of water and sodium levels in the body

- No known receptors that monitor Na+ levels in the body fluids - Changes in bp or volume trigger neural and hormonal controls to regulate Na+ content (baroreceptors/mechanoreceptors) - Concentration of Na+: determines osmolality of ECF and influences excitability of neurons & muscles; remains stable because water shift out of or into ICF - drink enough water to maintain osmolarity of 300 mOsm - Aldosterone - released from adrenal cortex at distal tubules of kidney - conserves Na+ and water by maintaining chemical gradients - increased reabsorption of Na and secretion of K and H to maintain electrolyte & acid-base balance (increases bp and bv) - Anti-diuretic hormone (ADH) - regulates water absorption in the final part of the nephron (decreases urine production) - 3 triggers: high blood osmolarity (dehydration), low bp, low bv - ADH increases aquaporin insertion into collecting duct cells increasing water reabsorption (more concentrated urine - increased blood volume) - Atrial natriuretic peptide (ANP) reduces reabsorption of Na+, so it tends to decrease blood volume and blood pressure

Chemical buffer system and why we need them in the body

- One or more compounds that resists pH change in the presence of a strong acid or a strong base - The resist changes in Ph b releasing hydrogen ions (acting as acids) when pH begins to rise or binding hydrogen ions (acting as bases), when pH begins to fall - Needed to maintain blood pH within a narrow range of pH 7.35-7.45 - this is because most cell processes work effectively at this pH - most proteins would denature if pH drops too much and enzymes would stop to function

Swallowing (deglutination)

- Oral phase - (voluntary) - tongue pushes bolus back - sensory receptors in pharynx initiate next phase - upper esophageal sphincter is closed - tongue presses against the hard palate, forcing the food bolus into the oropharynx - Pharyngeal-esophageal phase - (involuntary) - Nasopharynx blocked by soft palate - tongue blocks mouth- Larynx rises, epiglottis blocks airway - Coordinated by brainstem centers and cranial nerves - the upper esophageal sphincter relaxes; food enters the esophagus - Pharyngeal constrictor muscles push food into upper esophagus - Peristalsis will take over in esophagus - alternating waves of muscle push food through esophagus - peristalsis

Differentiate between organs of the alimentary canal (gastrointestinal tract) and accessory digestive organs.

- Organs of the alimentary canal (gastrointestinal tract) - what food passes through - the mouth (oral cavity), pharynx, esophagus, stomach, small intestine (duodenum, jejunum, ilium) and the large intestine (cecum, colon, rectum, appendix) - Accessory digestive organs - tongue, salivary glands, liver, gallbladder, pancreas - provide chewing, enzymes and buffers that assist in mechanical and chemical breakdown of food

Pressures impacting glomerular filtration rate

- Outward (out of capillary) pressures promote formation ->Hydrostatic pressure in glomerular capillary (HPgc) - Glomerular capillary pressure - Higher than normal capillary pressure to ensure filtration across whole length - Inward (into capillary) pressures oppose filtrate formation § Hydrostatic pressure in the capsular space (HPcs) - pressure exerted by filtrate in the glomerular capsule § Colloid osmotic pressure in glomerular capillary (OPgc) - pressure exerted by proteins in the blood - NFP = HPgc - (HPcs + OPgc)

Overhydration and dehydration

- Overhydrated - decrease in osmolarity of ecf - decrease in ADH release from posterior pituitary - no aquaporins in collecting duct cells - Water is not reabsorbed from the lumen of the collecting duct - it stays in the filtrate - Large amount of dilute urine is produced and excreted because we want to get rid of excess water. - Dehydration lead to increase osmolarity in EF - decrease plasma. Volume - stimulates renin-angiotensin-aldosterone system (which stimulates thirst centers in the hypothalamus)

Movement of blood & bile within the liver lobule

- Oxygen rich blood enters the liver through the hepatic artery (from branches of the aorta) --> oxygen poor but nutrient rich blood enters the liver from the portal vein, which is formed by veins coming from digestive system organs (like the intestines) --> Blood from portal vein branches and hepatic artery branches percolate from the triads through the sinusoids and empties into the central vein --> From central veins, blood flows to the hepatic veins which leave the liver and drain into the inferior vena cava --> Within the walls of the sinusoids are macrophages which remove debris such as bacteria and worn-out blood cells from the blood as it flows past - The blood in the sinusoids is mixed (arterial and venous) from branches of hepatic artery and portal vein, so the blood brings both oxygen and nutrients to the hepatocytes - Bile is produced by the hepatocytes --> It is released into the bile canaliculi, which are little spaces in between the hepatocytes --> Bile flows through the canaliculi toward the branches of the bile duct in the portal triad --> Blood flows through sinusoids toward the central vein (in the center of the lobule), but bile flows in the opposite direction, out toward the edges of the lobule, to leave the liver in the bile ducts

Reabsorption capabilities of the proximal convoluted tubule, descending and ascending limb of the nephron loop

- PCT is responsible for reabsorption of most water (99%) and potassium and sodium (~65%) and practically all glucose, amino acids, bicarbonate ion, vitamins, and other nutrients - The descending limb of the nephron loop is permeable only to water - some reabsorption of water occurs here (filtrate becomes more concentrated) - The ascending limb of the nephron loop is responsible for the reabsorption of sodium, chloride, and potassium by active transport (some passive reabsorption of Na+ occurs too). The ascending limb is not permeable to water, so no water reabsorption can occur here (becomes more dilute)

Peristalsis vs. segmentation

- Peristalsis involves alternating waves of contraction and relaxation in adjacent segments of the alimentary canal wall resulting the food moving in an aboral direction (away from the mouth, toward the anus) - This action is considered to be a propulsive function - moving food forward through the alimentary canal - Segmentation is the contraction and relaxation of nonadjacent segments of the alimentary canal wall resulting in mixing of the food - commonly observed in the small intestine and helps mix food with digestive enzymes and facilitates absorption - Unlike peristalsis, segmentation does little to move food along the alimentary canal and is thus considered to be involved primarily in mechanical breakdown. - Both actions are caused by the actions of the muscular externa

Filtrate

- Pre-urine, produced at the glomerulus by filtering blood - Isosmotic (same osmotic pressure) with blood - Contains waste products we want to eliminate from blood as well as water (180 liters/day filtered at glomerulus), ions, glucose & amino acids

Carbonic acid-bicarbonate buffer system

- Primary buffer system for the ECF - System centers around the weak acid H2CO3 (carbonic acid) and the weak base NaHCO3 (sodium bicarbonate - Large amounts of plasma bicarbonate (HCO3) produced from metabolic CO2 - Bicarbonate ions enter the plasma and form the alkaline reserve which will help buffer acids entering the blood - (CO2 + H2O <-> H2CO3 <-> HCO3- + H+) - IN the presence of a strong acid like HCL: the sodium bicarbonate salt buffers the hydrogen ions from the HCL, forming more weak acid (carbonic acid) and the salt NaCl (HCl + NaCO3 → H2𝐶O3 + 𝑁aCl) - In the presence of a strong base: the carbonic acid dissociates, releasing hydrogen ion - the H+ joins with the OH- (hydroxide) from the strong base, to form water, and more weak base (sodium bicarbonate) is formed (NaOH + H2CO3 --> NaHCO3 + H2O)

Liver

- Primary digestive function is to produce bile (in order to emulsify fats) - Processes nutrient-rich venous blood from digestive organs (portal vein): helps maintain blood glucose homeostasis, involved in fat metabolism, storage and transport of lipids, stores some vitamins, produce plasma proteins, synthesizes cholesterol, lipoproteins - Detox blood by converting ammonia to urea, metabolize alcohol, drugs, medications, hormones, process bilirubin and excrete bile pigments - Left lobe & bigger right lobe (posteriorly: caudate lobe is more superior - quadrate lobe is more inferior) - Portal hepatis - "door" of the liver - allows passage of hepatic portal vein, hepatic artery proper and common hepatic duct

Esophagus

- Propels food from the laryngopharynx of the stomach - Mucosa contain non-keratinized stratified squamous epithelium (continuous w/ oral cavity) - transition to simple columnar near stomach - Submucosa - contains esophageal glands (mucus-secreting for lubrication) - Muscularis externa - contains skeletal muscle in the upper third, skeletal/smooth in middle third, smooth muscle in inferior third - role in peristalsis - propel food to stomach - Adventitia - dense CT, no serous layer - Upper esophageal sphincter - skeletal muscle; prevent passage of air into esophagus while breathing - Lower esophageal sphincter - smooth muscle; prevents reflux of stomach contents into esophagus (GERD) - (Achalasia - difficulty opening LES sphincter, or weakness of peristalsis)

Osmolarity

- Refers to the number of particles or solutes in a given volume of water (kg of water) - The goal of the kidneys is to keep the solute load of body fluids constant by regulating urine concentration and volume - maintaining constant osmolality of extracellular fluids is crucial for preventing cells, particularly in the brain, from shrinking or swelling from osmotic movement of water

Internal structure of the kidney

- Renal cortex - superficial layer with granular appearance - Renal medulla - medullary (renal) pyramids: cone-shaped tissue that appear striped due to parallel bundles of urine collecting tubes & capillaries - renal columns: inward extensions of cortex separating pyramids - lobes: pyramid surrounded by cortical tissue - Major & minor calyces - A minor calyx surrounds the renal papillae of each pyramid and collects urine from that pyramid. Several minor calyces converge to form a major calyx. From the major calyces, the urine flows into the renal pelvis - Renal pelvis - funnel shaped tube drains into ureter - collects all urine

Respiratory acidosis vs. Metabolic acidosis

- Respiratory acidosis is characterized by low pH and an increase in the partial pressure of CO2. - Metabolic acidosis is characterized by low pH and a decrease in the concentration of bicarbonate ions.

Respiratory alkalosis vs. metabolic alkalosis

- Respiratory alkalosis is characterized by high pH and a decrease in the partial pressure of CO2. - Metabolic alkalosis is characterized by high pH and an increase in the concentration of bicarbonate ions

2 motility patterns in SI

- Segmentation - after a meal - ensures that the chyme is thoroughly mixed with bile and pancreatic and intestinal juices - It also ensures that the absorbable products of digestion come in contact with the mucosal epithelium (and the microvilli) for absorption - Peristalsis (migrating motor complex) - observed between meals - begin in proximal duodenum and move distally to the end of SI - motion sweeps any remaining non-digested particles to the end of the ileum and into the large intestine (controlled by hormone motilin)

Saliva

- Sero-mucous secretion released into the oral cavity by exocrine glands called the salivary glands - mostly water (98%), electrolytes, digestive enzymes (amylase and lipase), proteins mucin, lysozyme and IgA, metabolic waste - 3 types: (parotid, sublingual, and submandibular) - Functions: cleanse the mouth (prevent tooth decay), dissolve food chemicals (taste), moistens food to help compact the bolus, begin digestion of starch by enzyme amylase - PNS activity (from chemoreceptors / mechanoreceptors). =increased saliva - SNS activity = decreased secretion/ dry mouth

Juxtaglomerular apparatus

- Specialized region where the last part of the ascending nephron loop interacts w/ renal corpuscle - monitors blood pressure and filtrate concentration - Macula densa cells - loacted in the wall of the ascending limb of the nephron loop and have chemoreceptors that monitor the amount of NaCl in the filtrate entering the distal convoluted tubule - Granular cells - modified smooth muscle cells in the wall of the afferent arteriole that monitor blood pressure and cna release renin if the bp gets too low - extraglomerular mesangial cells - lie between the tubule and arteriole and pass signals between granular and macula densa cells

Difference between a strong acid and weak acid

- Strong acid will completely dissociate into its ions in an aqueous environment - an example is HCL which completely dissociates into H+ and Cl- when in solution - the high concentration of H+ ions causes a large decrease in pH (more acidic) - A weak acid will only partially dissociate into its ions in an aqueous environment - a weak acid like carbonic acid can release H+ in response to rise s in pH - Acids are proton donors (release H+)

Liver lobule

- Structure and functional unit fo the liver - Portal triads - branch of the hepatic artery (oxygen rich arterial blood enters sinusoids), portal vein (oxygen low, nutrient-rich blood enters sinusoids) & bile duct - Sinusoids - "leaky capillaries between rows of hepatocytes; containing macrophages - Bile flows through bile canalculi which drains into bile duct - Hepatocytes - (liver cells) - produce & secret bile, process nutrients, store fat soluble vitamins & glucose), detoxification of blood - Lobule is drained by central vein (after portal vein carries nutrient rich blood to liver & blood enters sinusoids)

micturition

- The act of emptying urinary bladder - spinal reflex with CNS influence - Parasympathetic nervous system contracts detrusor muscle, relaxes internal urethral sphincter - (During bladder filling, sympathetic nervous system relaxes detrusor, and contracts internal urethral sphincter to prevent voiding)

How does the enteric nervous system interact with the autonomic nervous system?

- The enteric nervous system is composed of the neurons in the submucosal and myenteric plexuses - These neurons participate in short reflexes that control GI activity such as segmentation and peristalsis in response to stimuli within the GI tract - At the same time, the ENS sends information to the CNS via visceral sensory fibers - Long reflexes involve integration between the ENS, CNS and ANS - The parasympathetic and sympathetic divisions of the nervous system can also influence digestive activity. In general, the parasympathetic nervous system increases digestive system activity, and the sympathetic nervous system inhibits it.

Histology of the renal tubule

- The filtrate is modified through the processes of reabsorption and secretion which occur by transport mechanisms in the epithelial cells of the renal tubule. - Proximal tubule - simple cuboidal epithelium, each cell w/ microvilli to increase surface area for absorption and mitochondirion providing energy needed for active transport process - Descending limb - lined w/ simple squamous epithelium limited in active transport (relatively passive) - Ascending limb - thick with simple cuboidal epithelium capable of significant active transport - Distal tubule - similar to proximal tubule but with fewer microvilli since the cells perform less transport (absorption & secretion)

How the renal system tries to compensate for pH changes in the body

- The kidneys regulate acid-base balance by adjusting the amount of bicarbonate in the blood, which can act as part of the alkaline reserve to buffer hydrogen ions. - The kidneys also adjust pH by ridding the body of so-called fixed acids - acids generated by cellular metabolism. - The kidneys get rid of acid by actively secreting hydrogen ions, using the phosphate buffer system in urine to ensure that secreted H+ are excreted, and by secreting the weak acid ammonium (NH4 + ), which is produced by glutamine metabolism in the PCT cell. - When a hydrogen ion is secreted, a bicarbonate ion is retained. This helps replenish the bicarbonate reserve. - In cases of alkalosis, the kidneys can secrete bicarbonate ions and retain H+ ions (basically vice versa)

Peritoneum

- The serous membrane that surrounds & protects organs in the abdominopelvic cavity - the visceral peritoneum covers the external surface of most digestive organs and is continuous with the parietal peritoneum which lines the walls of the abdominopelvic cavity - The potential space in-between the visceral and parietal peritoneum's is the peritoneal cavity which contains serous fluid - allowing the organs of the cavity to glide over each other - Organs that are wrapped by visceral peritoneum and are suspended in the abdominal cavity by mesentery are considered to be "intraperitoneal". Organs that are positioned on the posterior abdominal wall and are not wrapped by mesenteries, are located posterior to the peritoneum and are considered to be "retroperitoneal". The duodenum, pancreas and rectum are retroperitoneal.

Transcellular vs. paracellular routes of tubular reabsorption

- The transcellular route involves - transport across apical membrane - diffusion through the cytosol - transport across the basolateral membrane (often involves the lateral intercellular spaces because membrane transporters transport ions into these spaces) 0- movement through the IF an into capillary - Paracellular route involves - movement though leaky tight junctions, particularly in the PCT - movement through IF and into capillary

Renal clearance

- The volume of plasma from which the kidneys clear a particular substance in one minute - any compound that is completely cleared by the kidneys can be used to estimate GFR - To measure - compare amount of substance in the plasma to the amount of that same substance that ends up in the urine - Indicates GFR (monitoring GFR allows us to detect glomerular damage or follow progress of kidney disease) - Tells us how that substance is handled by the kidneys - for instance, whether it is reabsorbed from the filtrate, or whether it is secreted into the filtrate, and therefore excreted in the urine.

Dietary sources, uses in the body and considerations of fats

- Triglycerides - large organic molecules composed of three fatty acid chains attached to a glycerol molecule - most abundant form of dietary lipid, are good energy sources, and are stored as fat in adipose tissue - Dietary sources: · Saturated fats - (more H atoms, single bonds, solid at room temp - meat, dairy, coconut, hydrogenated oils - trans fats: margarine/solid shortening) · Unsaturated fats - (one or more double bonda, oils - liquid at room temp - seeds, nuts, olive oil, vegetable oils) · Cholesterol - (not used for energy) - egg yolk, meat, organ meat, shellfish, milk products - Uses in the body: · Protect from heat loss, cushion body organs, energy store · Phospholipids create myelin and cell membranes · Cholesterol precursor to hormones, stabilizes cell membranes · Triglycerides are major fuel source for skeletal muscle & hepatocytes · Presence of fats in diet aids in absorption of fat-soluble vitamins - Dietary considerations: · 20-35% of total calorie intake · Saturated should be less than 10% of total fat intake · Limit cholesterol in diet - liver makes 85% of what we use · Liver can't make 2 essential FA: linoleic acid (omega-6 FA) or linolenic acid (omega-3 FA)

How does changing the diameters of the afferent and efferent arteriole affect GFR?

- Vasoconstriction of the afferent arteriole decreases the blood flow into the glomerulus, so decreases hydrostatic (blood) pressure, or HPgc in the glomerulus. This decreases NFP and GFR. - Vasodilation of the afferent arteriole increases blood flow and blood pressure in the glomerulus, which increases NFP and GFR. - Vasodilation of the efferent arteriole decreases the resistance to blood flowing out of the glomerulus. This decreases glomerular blood pressure, or HPgc, so also decreases NFP and GFR. - Vasoconstriction of the efferent arteriole increases the resistance to blood flow out of the glomerulus. This increases the blood pressure inside the glomerulus, so increases HPgc, increases NFP and increases GFR.

Fat-soluble and water-soluble vitamins

- Vitamins - required in small amounts for growth & good health - help us use nutrients because serve as co-enzymes in metabolic reactions - Fat-soluble vitamins - include vitamins A, D, E and K - absorbed together with other lipids in the intestines - anything that interferes with lipid absorption also interferes w/ fat soluble vitamin absorption - stored in fatty tissues & liver (besides K) - excess can result in toxicity - Water-soluble vitamins - B complex vitamins and Vitamin C - absorbed along w. water in intestines - have their own transporters besides vitamin B12 where intrinsic factor complex binds to receptor, uptake by endocytosis - Not stored, excess excreted in urine

Glomerular filtration rate (GFR)

- Volume of filtrate formed by all the glomeruli in both kidneys per minute - modulated by three variables: - net filtration pressure (directly proportional to GFR - glomerular hydrostatic pressure has the largest influence on GFR) - Surface area - can be adjusted by glomerular mesangial cells, such that a decrease in surface area will decrease GFR - Filtration membrane permeability - rarely changes, but if altered any decrease in permeability of the membrane will lead to a decrease in GFR - If GFR increases: more filtrate is formed and urine output increases Blood volume and blood pressure decrease (because water is excreted) - If GFR decreases: less filtrate is formed and urine output decreases Blood volume and blood pressure increase (because water is conserved)

What does it mean when we say the gastrointestinal tract has a mind of its own (its own brain)?

- Within the wall of the gastrointestinal tract organs are extensive networks of neurons and fibers that form intrinsic nerve plexuses - These intrinsic nerve plexuses form the enteric nervous system (ENS) and are responsible for regulating digestive system activity - The intrinsic nerve plexuses are the submucosal plexus (located in the submucosa) and the myenteric plexus (located in between the smooth muscle layers of the muscularis externa). - The ENS provide the major nerve supply to the GI tract wall and control GI tract motility (motion) - These neurons of the ENS participate in short reflexes that control GI activity in response to stimuli within the GI tract - Receptors in the wall of the GI tract can respond to stimuli such as stretch of the organ wall, changes in osmolarity, or changes in pH to change organ activity.

Importance of renal osmotic gradient

- Without the osmotic gradient we would never be able to concentrate urine over 300 mOsm - driving force for water movement by osmosis - Even if aquaporins are present, there won't be any net water movement through them unless there is a high concentration of solutes (high osmolarity) in the interstitial space. In osmosis, water wants to move from an area of high water concentration (low osmolarity) to an area of low water concentration (high osmolarity). The osmolarity must be high in the interstitial space in order for enough water to be reabsorbed to concentrate the urine.

Large intestine

- absorb most of the remaining water form indigestible food residues, store residues temporarily and then eliminate them from the body as semisolid feces - Mucosa - simple columnar with goblet cellsthrough most of colon, no circular fold / villi - Intestinal crypts (glands) - contain many more goblet cells to help lubricate tract for feces propulsion protect epithelium; enterocytes - absorptive cells to absorb water and electrolytes - Muscularis externa - incomplete outer longitudinal layer forms teniae coli (3 longitudinal strips of smooth muscle - arrangement creates a puckering of LI wall resulting in pocket-like sacs called haustra) - Internal anal sphincter - involuntary smooth muscle - External anal sphincter - voluntary skeletal muscle

Intrinsic controls the kidney uses to regulate GFR

- act locally within the kidney to maintain GFR despite changes in systemic blood pressure- changes are minute to minute in response to normal fluctuating changes in blood pressure - allow kidney "to do its job" - Myogenic mechanism - smooth muscle reflexively contracts when stretched and relaxes when not stretched - inherent property of smooth muscle - increased systemic bp stretches afferent arteriole causing reflexive smooth muscle contraction - blood flow into glomerulus decreases preventing increase of GFR - Tubuloglomerular feedback mechanism - Directed by the macula densa cells in the juxtaglomerular apparatus - Macula densa cells are sensitive to filtrate NaCl concentration in the ascending limb of loop - When GFR increases, time to reabsorb NaCl goes down, and the concentration of NaCl in the ascending limb of loop goes up! - Macula densa cells release vasoconstrictor chemicals constricting the afferent arteriole - Glomerular hydrostatic pressure decreases and GFR is decreased - allows more time for NaCl reabsorption

The oral cavity

- includes the lips, cheeks, hard palate, soft palate, uvula, tongue, and salivary glands. - Physiological functions include ingestion, mechanical breakdown (chewing assisted by the tongue), secretion (salivary glands), and propulsion (tongue)

Dehydration

- leads to increased osmolality in ECF, dry mouth - stimulates thirst and activates hormonal systems working at the kidney to conserve water - helps regulate water intake

Transport maximum

- number of transport proteins available in tubule cell membrane - If the amount of a substance in the filtrate exceeds the number of transport proteins that are available, the transporters are saturated. - transports are maximally active - When all the transport proteins are saturated for a given substance (ex. glucose), the excess is secreted in the urine.

Pharynx

- provides a common pathway for food, fluids and air - involved in propulsion of food (swallowing) - a voluntary activation that also has some involuntary aspects (coordination) - Mucosa of oropharynx and laryngopharynx contains stratified squamous epithelium (continuous w/ oral cavity) - Muscularis externa - contains skeletal muscle - longitudinal and circular layers

Collecting ducts

- receives filtrate from nephrons in the renal cortex and contains two cell types: •Principal cells - maintain body's water and sodium balance •Intercalated cells - maintain the acid-base balance in blood - Near the papilla, collecting ducts fuse into papillary ducts with columnar epithelium - Once the fluid reaches the end of the papillary duct it is officially called urine because the processing is done

2 structures responsible for the formation & maintenance of the osmotic gradient

- the long nephron loops of the juxtamedullary nephrons (countercurrent flow of filtrate between the descending & ascending limbs) are responsible for establishing the osmotic gradient - The vasa recta (countercurrent exchanger flow of blood through descending and ascending parts)are responsible for maintaining the osmotic gradient - They follow the long nephron loops deep into the medulla and are very permeable to both water and solutes, so the blood that travels through the vasa recta is isosmotic with the extracellular fluid around it - stuff moves in and out of vasa recta t maintain osmotic equilibrium between the blood and interstitial fluid

tubular secretion

- the process by which the body gets rid of substances it doesn't want by moving them from the blood to the filtrate in the lumen of the tubule.

Extrinsic controls

- under extreme conditions in which blood pressure falls outside normal range (i.e. hypovolemic shock), nervous system and endocrine (hormonal) systems kick in to maintain systemic blood pressure and preserve blood flow to brain, vital organs (sometimes to the detriment of the kidneys) - include activating the sympathetic nervous system and activating the reninangiotensin-aldosterone mechanism to maintain systemic blood pressure. When there are extreme drops in blood pressure outside the normal range, as observed during extreme blood loss or hypovolemic shock, the sympathetic nervous system is activated - Norepinephrine is released from sympathetic nerve fibers and epinephrine is released by the adrenal medulla to cause vasoconstriction in peripheral blood vessels, which helps to increase blood pressure

Tubular reabsorption in the PCT

- utilizes sodium gradients to facilitate the movement of other ions. The sodium gradient is established by the Na+/K+ ATPase on the basolateral surface of the tubule cell. The Na/K ATPase moves 3 Na+ ions out of the cell for each K+ ion moved into the cell. This occurs by primary active transport because an ATP molecule is used to do this --> -This establishes the Na-K gradient so that Na+ is high outside the cells and K+ is high inside the cells. The reabsorption of Na by active transport provides the energy and the means for reabsorbing almost every other substance, including water - The result of this is that Na+ will now be able to move down its concentration gradient and bring things along with it - by co-transport. Na+ moving down its concentration gradient (on a carrier or transport protein in the apical membrane) will co-transport glucose, amino acids, some ions and vitamins. This is secondary active transport. - Carrier or transport proteins in the apical membrane of the tubule cell will move Na down its concentration gradient into the cell, and at the same time cotransport other substances into the cell against their concentration gradient. (Substances that are moved this way are glucose, amino acids, some ions and vitamins) - Passive transport (moving down concentration gradient) - Water is reabsorbed by moving through aquaporins (water channels) in the cell membrane. Water moves by osmosis - it follows the osmotic gradient. - Water reabsorption in the PCT is called "obligatory water reabsorption" because water is "obliged" to follow the solutes. - Water reabsorption happens regardless of the hydration status of the body. In the DCT and collecting duct we can regulate water reabsorption. Lipid soluble substances are reabsorbed by diffusing down their concentration gradient. Many ions such as Ca++, Cl-, and K can be reabsorbed by the paracellular route in between cells. Most amino acids, glucose, ions, lipid-soluble solutes, vitamins, and 99% of the filtered water is reabsorbed in the proximal convoluted tubule.

Structural modifications of SI mucosal layer that increase efficiency of absorption

-circular folds (plicae circulares) - permanent folds of the mucosa and submucosa that force chyme to spiral around the lumen, slowing its movement and allowing more time to interact with the epithelial cells - Villi - finger like projections of the mucosa that stick out into the luminal space - actively increase the surface area of the mucosa allowing for more absorptive cells to be packed into a small space. - Microvilli - cytoplasmic extensions on the absorptive enterocytes. The microvilli also house brush border enzymes that are responsible for breaking food stuffs down into their building blocks

blood flow of the kidneys to the nephron

1-Aorta 2-Renal Artery 3-Segmental Arteries 4-Interlobar Artery 5-Arcuate Artery 6-Cortical Radiate Artery 7-Afferent Arterioles (Renal corpuscule) 8-Glomerulus (Renal corpuscule) 9-Efferent Arterioles (Renal corpuscule) 10-Peritubular Capillaries (Renal Tubule) 11-Cortical Radiate Vein 12-Arcuate Vein 13-Interlobar Vein 14-Renal Vein 15-Vena Cava

Which minerals are necessary to make our bones strong? To produce thyroid hormone? For hemoglobin synthesis?

Calcium salts are the minerals deposited in bones and help make them strong. Iodine is necessary for the production of thyroid hormone. Iron is part of the heme group in the hemoglobin that binds oxygen.

How is inulin handled by the kidneys, and how can its renal clearance be used as an indicator of kidney function?

Inulin is a plant compound that is freely filtered at the glomerulus, and is neither reabsorbed or secreted. All the inulin that is filtered ends up in urine, so the clearance of inulin (the amount that shows up in urine) is the same as the glomerular filtration rate. Inulin can be intravenously infused at a known concentration, and its appearance in the urine over a 24 hour period can be used to determine GFR. A normal rate for the clearance of inulin is 125 ml/min, so GFR is 125 ml/min. - If a substance has a C less than inulin, that suggests the substance is at least partially reabsorbed. - If a substance has a C equal to inulin, there is no net reabsorption or secretion. - If a substance has a C greater than inulin, then the tubule cells are secreting the substance into the filtrate. This is the case with most drug metabolites.

Summary: Tubular reabsorption

Proximal Convoluted Tubule (PCT) •Reabsorption of all nutrients, electrolytes, most Na+ and water (obligatory reabsorption) Descending limb of nephron loop •Reabsorption of water only through aquaporins Ascending limb of nephron loop •Reabsorption of solutes (Na+, K+, Cl-) Distal Convoluted Tubule (DCT) and/or Collecting Duct •Aldosterone stimulates synthesis of Na+ channels (apical) and Na+/K+ ATPase (basolateral) increasing Na+ reabsorption •Parathyroid hormone increases Ca2+ reabsorption •Antidiuretic hormone stimulates aquaporin synthesis increasing water reabsorption •Atrial natriuretic peptide (ANP) inhibits aldosterone effect (so prevents Na+ reabsorption) - Water reabsorption in the DCT and Collecting Duct is regulated water reabsorption

Regulation of Sodium Balance

Sodium is most abundant cation in ECF Only cation exerting significant osmotic pressure Controls ECF volume and water distribution because water follows salt Changes in Na+ levels affect plasma volume, blood pressure, and ICF and IF volumes! Regulating dietary sodium intake is a major strategy in control of blood pressure

Mesentery

a double layer of peritoneum that extends to the digestive organs from the body wall. Two layers of serous membranes fuse together and suspend the digestive organs from the posterior abdominal wall, holding individual organs in place. Some digestive organ mesenteries have specific names, such as the greater omentum, or sigmoid mesocolon. - Mesenteries provide a route for blood vessels, lymphatics, and nerves to travel to the individual organs, they hold organs in place, and they store fat.

What is tubular secretion and which types of substances are generally secreted into the tubule?

the process by which the body gets rid of substances it doesn't want by moving them from the blood to the filtrate in the lumen of the tubule. As long as the substance doesn't get reabsorbed back into the blood, anything that remains in the tubule will be excreted in the urine. Things that the kidneys secretes are excess ions (K+), drugs or their metabolites, toxins, H+ (acid-base balance) and nitrogenous wastes such as urea

Major functions of the kidneys

•Regulate total volume of water in the body and the total concentration of solutes (osmolality) •Regulate the concentration of ions in the extracellular fluids •Regulate long term acid-base balance •Excrete metabolic wastes and foreign substances (drugs, toxins) •Producing hormones (erythropoietin, renin) •Converting Vitamin D to its active form