Unit 4 test

Villi (1 of 3 folds of the small intestines) (not visible to eye)

1. Mucosa folds into projections called villi. -a. Each villus consists of a layer of enterocytes surrounding a central core of blood capillaries and a lymphatic vessel called a lacteal. -b. Between villi mucosa indents to form intestinal crypts. --1. House glands with enteroendocrine cells and mucus-secreting goblet cells.

High-density lipoproteins (HDLs) ( 1 of the 3 types of lipoproteins)

3. High-density lipoproteins (HDLs) - synthesized in liver and released into bloodstream or small intestine. -a. Transfer lipids from peripheral cells back to liver; in liver, cholesterol is absorbed and excreted from body in bile. -b. HDL is considered "good" cholesterol because it carries cholesterol back to liver where it is excreted from body as component of bile

The Esophagus

A. Muscular tube about 25 cm (10 in.) long found posterior to trachea. B. Transports a bolus from pharynx to stomach. C. Esophageal mucosa contains esophageal glands which secrete mucus to lubricate bolus as it passes through esophagus. *contains upper esophageal sphincter and the gastroesophageal sphincter

Metabolic States

A. Two basic metabolic states ensure that cells are provided with energy at all times. B. States differ in terms of their proximity to feeding and metabolic reactions that predominate. 1. Absorptive state 2. Postabsorptive state

Describe the peritoneal cavity. Define intraperitoneal, retroperitoneal and mesenteries.

C. Between the two peritoneal layers we find peritoneal cavity. -1. Contains serous fluid. D. Intraperitoneal: organs located entirely within peritoneal cavity. E. Retroperitoneal: abdominal organs partly or completely outside peritoneal cavity. F. Mesenteries: areas where visceral peritoneum folds over on itself around certain organs, particularly small intestine. -1. Support and bind these organs together and keep small intestine in a particular shape that fits within abdominopelvic cavity. -2. Mesenteries also house blood vessels, nerves, and lymphatic vessels, anchoring them in place.

Describe factors that affect metabolic rate

E. Factors that affect metabolic rate. 1. Thyroid hormones, growth hormones, fever, nutritional status, physical activity, and certain drugs. 2. BMR varies between individuals, depending on factors such as gender and muscle mass.

Describe the functions of the large intestine

Functions of Large Intestines A. Receives material from small intestine that was not digested or absorbed, and is a passageway for feces or fecal matter to exit body. B. Active in absorbing water and electrolytes. -1. Critical for maintaining fluid, electrolyte, and acid-base homeostasis. C. Secretion (primarily in form of mucus), propulsion, and defecation. D. Houses numerous bacteria that perform important functions such as synthesizing vitamins.

Describe the function of the gallbladder and trace the pathway of bile to the small intestine.

Gallbladder A. Stores bile, concentrates it (removing water), and releases it when stimulated. B. Pathway of bile: -1. Gallbladder to release bile into cystic duct. -2. Cystic duct joins common hepatic duct to form common bile duct. -3. Common bile duct joins main pancreatic duct near duodenum to form hepatopancreatic ampulla. -4. Ampulla is surrounded by a ring of smooth muscle called hepatopancreatic sphincter. --a. Controls emptying of bile and pancreatic fluids into duodenum. -5. Contents of hepatopancreatic ampulla empty into duodenum at major duodenal papilla.

discuss the histology of the large intestines.

Histology of the Large Intestine A. Mucosa of large intestine lacks villi and its cells lack microvilli. -1. These structural adaptations reflect fact that nutrient absorption is not large intestine's primary function. B. Mucosa is rich with goblet cells that secrete protective and lubricating mucus.

Define metabolic rate and explain how it is measured.

Metabolic rate A. Definition: total amount of energy expended by body to power all of its processes. -1. Heat is generated as a byproduct of these collective reactions, which is a vital source of body heat for maintenance of temperature regulation (thermoregulation). B. Measured in units of heat or calories. C. Metabolic rate can be determined indirectly by measuring oxygen consumption. -1. Directly related to amount of energy generated and thus, heat produced.

Describe the other functions of the liver

Other Liver Functions 1. Liver excretes bilirubin; a waste product that results from breakdown of hemoglobin by spleen. -a. Some remains in blood and is excreted by kidneys. 2. Nutrient metabolism - processes nutrients obtained from diet. 3. Detoxification - detoxifies substances produced by body, and substances that we eat or drink, some of which are harmful to body. 4. Excretion - directly excretes bilirubin in bile along with other substances liver processes, particularly certain antibiotics; also modifies substances so that they can be excreted by kidneys.

Describe the role of the pharynx in regards to digestion.

Pharynx (throat) A. Only oropharynx and laryngopharynx are part of alimentary canal. B. Oropharynx houses two sets of tonsils—palatine tonsils and lingual tonsils. -1. Tonsils perform defensive functions; protect remainder of alimentary canal from any pathogens that enter body via oral and nasal cavities. C. Primary function of pharynx is propulsion in form of swallowing, during which bolus passes through pharynx and into esophagus.

List the three pairs of salivary glands

Submandibular, sublingual, parotid glands

. Explain the process of deglutition, including the three phases

Swallowing or Deglutition A. Specialized type of propulsion that pushes a bolus of food from oral cavity through pharynx and esophagus to stomach. B. Swallowing relies on coordinated action of upper alimentary canal, including soft palate, pharynx, and esophagus; tongue also plays a role in this process. C. Consists of three phases: -1. Voluntary phase: tongue pushes bolus toward oropharynx. -2. Pharyngeal phase: bolus enters oropharynx; soft palate and epiglottis seals off nasopharynx and larynx. -3. Esophageal phase: peristaltic waves move bolus down esophagus.

Define vitamin and state the importance of vitamins to the diet. Define water-soluble and fat soluble vitamins and list the vitamins in each group.

Vitamins (vital amines): 13 organic compounds that are required for the body's functions. a. Fat-soluble vitamins - hydrophobic compounds structurally similar to cholesterol. -1. Vitamin A, D, E, and K. b. Water-soluble vitamins - hydrophilic compounds featuring polar covalent bonds. -1. Vitamin C and B vitamins

Describe the functions of Saliva

a. Moistening, lubricating, and cleansing oral mucosa. b. Lysozyme and IgA deter growth of pathogenic bacteria in oral cavity. c. Mechanical digestion, achieved by moistening and helping to mix ingested food into a bolus so it can be swallowed. d. Chemical digestion, achieved by actions of salivary amylase. e. Many food molecules dissolve in water of saliva, and these molecules then stimulate taste receptors on tongue.

Absorptive state (1 of the 2 metabolic states)

1. Absorptive state - occurs right after feeding, from time ingested nutrients enter bloodstream. -a. Can last up to 4 hours. -b. Following processes occur as nutrients are absorbed from small intestine: --1. Oxidation of nutrient molecules, primarily glucose, provides fuel to cells. --2. Glyconeogenesis stores excess glucose in skeletal muscle and hepatocytes. --3. Lipogenesis stores triglycerides in adipocytes and hepatocytes. --4. Protein synthesis provides structural materials for cells. -c. Pancreatic hormone insulin orchestrates many of absorptive state processes. --1. Release is triggered by increased blood glucose levels.

. Describe the composition of saliva

1. Consists primarily of water; electrolytes such as sodium, chloride, and potassium ions; and variable amounts of mucus. 2. Also contains: -a. Salivary amylase - first digestive enzyme that ingested food encounters; catalyzes beginning of carbohydrate digestion. -b. Enzyme lysozyme catalyzes perforation of bacterial plasma membranes; allows bacteria-killing substances in saliva to enter and kill bacteria. -c. Secretory IgA - antibody immunoglobulin A, or IgA; binds specific antigens on pathogens and mediates their destruction. -d. Bicarbonate ions function is to neutralize any acid from stomach that regurgitates into esophagus.

Mechanical digestion (1 of the 2 types of digestion)

1. Mechanical digestion, in which food is physically broken into smaller parts. -a. All nutrients go through same mechanisms of mechanical digestion— mastication in mouth, churning in stomach, and segmentation in small intestine.

Explain the motility of the stomach in terms of its Receptive function

1. Receptive function - when food or liquid is swallowed, gastroesophageal sphincter and smooth muscle of fundus and body of stomach relax to allow stomach to fill, a process known as receptive relaxation

Very low-density lipoproteins (VLDLs) ( 1 of the 3 types of lipoproteins)

1. Very low-density lipoproteins (VLDLs) - contain a higher percentage of lipids than protein. -a. Transport primarily triglycerides from liver to adipose tissue for storage and to muscle tissue for immediate use as fuel. -b. Lipoprotein lipase - enzyme found on endothelial cell plasma membranes; removes triglycerides from VLDLs, and converts them to free fatty acids and monoglycerides; can be absorbed by cells where they are oxidized for fuel or reassembled into triglycerides

Describe the absorption of water, electrolytes

A. Alimentary canal absorbs large quantities of water, electrolytes, and vitamins: -1. Much of this absorption occurs in small intestine, but a significant quantity occurs in large intestine too. B. 8 liters or water are absorbed into enterocytes of small intestine. C. Most of remaining water is absorbed into enterocytes of large intestine, leaving only about 0.1 liter of water to be excreted in feces

Define alimentary canal and accessory organs and list organs that belong to each

B. Alimentary canal - continuous tube through which food passes directly. -1. Consists of oral cavity (mouth), pharynx, esophagus, stomach, small intestine, and large intestine. C. Accessory organs - not part of alimentary canal but assist in digestion in some way. -1. Include teeth, tongue, salivary glands, liver, gallbladder, and pancreas. -2. Food generally does not come into direct contact with accessory organs, although teeth and tongue are exceptions.

what is the roles of the upper esophageal sphincter and the gastroesophageal sphincter

D. At junction of pharynx and esophagus, muscularis externa is modified into a sphincter called upper esophageal sphincter. -1. Controls passage of bolus into esophagus. E. At esophagus' inferior end is another sphincter, gastroesophageal sphincter, also known as lower esophageal sphincter. -1. Regulates passage of bolus into stomach. -2. Also prevents contents of stomach from re-entering esophagus. F. Primary functions of esophagus are propulsion and a small amount of secretion of mostly mucus.

Define basal metabolic rate and explain how it is measured.

D. Basal metabolic rate (BMR) - defined as minimal rate of metabolism for an awake individual or "energy cost of living". -1. Body continues to use energy even when at rest. -2. Measurement requires following conditions to be met. --a. Person has not eaten for past 12 hours and has had a restful night of sleep. --b. Person is not performing physical activity and has not performed strenuous physical activity for at least 1 hour. --c. Person is not under physical or emotional stress. --d. Temperature surrounding person is constant and comfortable.

Differentiate between radiation, conduction, convection, and evaporation.

Heat Exchange A. Heat moves when gradients are present. B. Heat produced by body's metabolic reactions is exchanged with environment by 4 mechanisms: -1. Radiation - process that transfers heat from one object to another through electromagnetic wave. -2. Conduction - process where heat is transferred from one object to another through direct contact. -3. Convection - process in which heat is transferred through a liquid or gaseous medium. -4. Evaporation - process by which water changes from a liquid to a gas

Explain the motility of the stomach

Motility enables stomach to receive food from esophagus, churn incoming bolus into chyme, and control rate at which chyme empties into small intestine It has: receptive function, churning function, emptying function.

. Digestive system

Set of organs that breaks down food items into nutrients that can be delivered by bloodstream to cells. A. Digestive system consists of two types of organs. 1. Organs of alimentary canal, also known as gastrointestinal (GI) tract or digestive tract. 2. Accessory organs.

Explain the importance of thermoregulation in the body. Define core body temperature and state the average

Thermoregulation A. Thermoregulation (regulation of body temperature) - a key homeostatic variable that must be maintained within a narrow range to ensure all systems function properly. B. Body temperature is maintained within a relatively constant range of 35.8 to 38.2 °C (96-101 °F) with an average of 37.5 °C (99.5 °F); reflects core body temperature. C. Core body temperature -temperature of deep body structures including liver and brain. -1. Fluctuates throughout day. -2. Accurately measured with a rectal thermometer. D. Body temperature is regulated by a negative feedback loop.

Types of lipoproteins

1. Very low-density lipoproteins (VLDLs). 2. Low-density lipoproteins (LDLs) 3. High-density lipoproteins (HDLs) *Types of lipoproteins differ in ratios of lipid to protein

Chemical digestion (1 of the 2 types of digestion)

2. Chemical digestion, in which chemical bonds between food molecules are broken. -a. Chemical digestion varies for each nutrient because digestive enzymes are specific for a single type of bond in a single type of nutrient

. Explain the motility of the stomach in terms of its churning function

2. Churning function - after a meal, smooth muscle layers of stomach begin to produce waves of peristalsis. -a. Peristalsis propels bolus to pylorus, where small amounts of chyme are propelled through pyloric sphincter into duodenum. -b. Remainder of chyme is pushed backward into stomach where peristaltic waves churn and mix chyme, and process repeats.

Low-density lipoproteins (LDLs) ( 1 of the 3 types of lipoproteins)

2. Low-density lipoproteins (LDLs) - what is left over after VLDLs have unloaded their triglycerides, increases density of complex. -a. LDLs are main mechanism by which cholesterol is delivered to body's cells. -b. When LDL binds to a cellular receptor, it triggers receptor-mediated endocytosis and uptake of cholesterol. -c. VLDL and LDL - considered "bad" cholesterol because they carry cholesterol to peripheral cells; can contribute to disease

Postabsorptive state (1 of the 2 metabolic states)

2. Postabsorptive state - begins once nutrient absorption is complete, usually after 4-hour absorptive window has ended. -a. Body is usually in this state in late morning, late afternoon, and most of night. -b. Anabolic processes slow or stop and following processes dominate. --1. Breakdown of proteins in muscle cells releases glucogenic amino acids into blood. --2. Ketogenesis in hepatocytes converts fatty acids to ketone bodies and releases them into blood. --3. Gluconeogenesis and glycogenolysis in hepatocytes release glucose into blood. --4. Lipolysis in adipocytes releases fatty acids into blood. --5. Oxidation of molecules such as fatty acids provides most cells with fuel. ---a. Glucose sparing - phenomenon in which cells catabolized newly delivered fatty acids preferentially in order to conserve glucose for cells of nervous system. ----b. Non-nervous system cells can also use ketone bodies and amino acids for fuel. -c. Pancreatic hormone glucagon, released when blood glucose level drops. --1. Triggers glycogenolysis and gluconeogenesis

Microvilli (1 of 3 folds of the small intestines) (not visible to eye)

2. Smallest folds, microvilli, are found in plasma membrane of enterocytes. -a. Each enterocyte has as many as 3000 microvilli; gives cell appearance of a bristle brush, or brush border. -b. Digestive enzymes produced and secreted by enterocytes catalyze reactions that break down disaccharides and peptides.

. Explain the motility of the stomach in terms of its emptying function

3. Emptying function -control movement of chyme into duodenum; different materials pass through pyloric sphincter at different rates. -a. Liquids move rapidly from stomach to duodenum with essentially no delay. -b. Solids must be converted to a nearly liquid state before they are able to enter small intestine. -c. Control of gastric emptying is critical because duodenum must mix incoming chyme thoroughly before it moves to rest of small intestine; two reasons. --1. Chyme is acidic, and duodenum must mix it with bicarbonate ions to avoid damaging intestinal mucosa. --2. Chyme is generally very concentrated and must be diluted with water from pancreatic juice to prevent chyme from drawing water into intestinal lumen by osmosis.

Describe the digestion and absorption of proteins

A. Chemical digestion of proteins does not begin until they reach stomach, where they encounter enzyme pepsin. -1. Activated pepsin catalyzes reactions that digest proteins into smaller polypeptides, oligopeptides, and some free amino acids. -2. Pepsin reactions catalyze only about 10-15% of proteins in ingested food. B. Majority of protein digestion takes place in small intestine with help of pancreatic enzymes and brush border enzymes. -1. First pancreatic enzyme to become activated is precursor trypsinogen; becomes active enzyme trypsin when it encounters enzymes on intestinal brush border. C. Na+/K+ pump creates gradient for Na+ absorption; certain amino acids then transported into enterocyte. D. Amino acids cross by facilitated diffusion and enter blood. E. Once in blood, delivered to liver via hepatic portal vein for processing

Explain the importance of cholesterol and how the liver processes cholesterol

A. Cholesterol is not oxidized for fuel. B. Important to many anabolic processes in body. -1. Modified to produce vitamin D, steroid hormones, and bile salts. -2. Also an important structural molecule in plasma membranes. C. Cholesterol is found in animal-based foods including meats and dairy products. D. Liver is capable of synthesizing 85% of required cholesterol with diet contributing only 15%. E. Cholesterol is packaged along with other lipids and proteins into structures called lipoproteins. -1. Provide transportation for cholesterol and other lipids in bloodstream.

Describe the digestion and absorption of carbohydrates

A. Digestion begins in mouth with help of salivary amylase from salivary glands. -1. Catalyzes reactions that break long polysaccharides into shorter oligosaccharides. -2. Generally accomplishes little actual chemical digestion because food simply is not in mouth long enough for it to have much effect. B. Salivary amylase digestion continues in stomach, but stomach acid generally inactivates this enzyme before it can complete task. C. Chemical digestion of carbohydrates resumes in small intestine, where polysaccharides and oligosaccharides encounter pancreatic amylase. D. Brush border enzymes break disaccharides into monosaccharides. E. Na+ /K+ pump creates gradient for Na+ absorption; glucose and galactose transported by Na+ /glucose cotransporter. F. Fructose absorbed by facilitated diffusion. G. Monosaccharides diffuse into blood. H. Once in blood, delivered to liver via hepatic portal vein for processing.

Describe the peritoneal membranes

A. Digestive organs that reside in abdominopelvic cavity share a common set of serous membranes, blood vessels, and nerves. B. Peritoneal membranes - largest serous membrane in body. -1. Consists of following two layers: --a. Outer parietal peritoneum lines inner surface of body wall. --b. Visceral peritoneum, or serosa- where parietal peritoneum meets abdominal organs, it folds in on itself; forms outer tissue layer of such organs.

. Discuss the basic functions of the oral cavity, the teeth, and the tongue. Include definitions of bolus, deglutition and mastication. PT 1

A. Digestive system begins at oral cavity, or mouth, where four different digestive processes occur: ingestion, secretion, chemical and mechanical digestion, and propulsion. B. Although oral cavity is technically part of alimentary canal, it houses two accessory organs: teeth and tongue. C. Three pairs of accessory organs, salivary glands, are located in and around oral cavity. -1. Turn ingested food into a moist, chewed mass called a BOLUS.

Describe motility in the small intestine during fasting

A. During fasting, small intestine exhibits slow, rhythmic contractions along its length in a pattern called migrating motor complex. -1. Contractions clear any remaining material, including leftover food and secretions. -2. Requires about 2 hours to push digesting food from duodenum to ileocecal valve. -3. Controlled by both ENS and a hormone called motilin; produced by cells in duodenal mucosa

Overview of Metabolism and Nutrition

A. Energy content in human diet is measured in terms of heat. B. Calorie (C) - measure of heat. -1. One calorie is amount of heat required to raise temperature of one gram water by one degree Celsius C. Kilocalorie - actual unit of calorie used to measure human diet. -1. One kilocalorie is amount of heat required to raise temperature of one kilogram of water by one degree Celsius.

overview of Regulation of Feeding

A. Feeding is controlled by a variety of hormonal and neural signals that stimulate and/or inhibit feeding-related nuclei found in hypothalamus. B. Hypothalamus houses two nuclei that control homeostatic variables associated with feeding. -1. Satiety center elicits feeling of fullness and inhibits desire to eat. -2. Hunger center (feeding center) elicits feelings of hunger and stimulates desire to eat.

Describe the six basic processes of the digestive system.

A. Ingestion: bring food and water into digestive system. -1. Occurs via mouth under normal conditions. B. Secretion: digestive organs contain both endocrine and exocrine glands that secrete a variety of substances—such as mucus, enzymes, acid, and hormones—to aid other digestive processes. C. Propulsion: process that allows ingested food and liquids pass from one digestive organ to next. -1. Propulsion is accomplished largely by rhythmic contractions of smooth muscle of alimentary canal called peristalsis; aided by mucus secreted by multiple organs. D. Digestion: food breakdown. E. Absorption: movement of digested food particles through wall of alimentary canal into blood or lymphatic vessels. -1. Water, electrolytes, and vitamins are also absorbed into blood in same manner. F. Defecation: exit of certain ingested materials are not digestible or usable by body. -1. Defecation also provides body with a way to eliminate certain metabolic wastes

Small intestine 3 folds

A. Internally three progressively smaller types of folds; most absorption that occurs takes place in this region. 1. Folds increase surface area available for absorption about 400 to 600 times The 3 types of fold: -Circular folds -Mucosa folds into projections called VILLI -Microvilli: smallest folds

Describe roles of the proximal and distal portions of the large intestines

A. Large intestine has two functional segments: -1. Proximal large intestine consists of ascending and transverse colon. -2. Distal large intestine consists of descending and sigmoid colon, rectum, and anal canal. B. Proximal large intestine is primary site of water and electrolyte absorption and bacterial activity. C. Distal large intestine performs a small amount of absorption, primarily of water, but its main role is to store fecal material until it is ready to be expelled during defecation.

Describe the functions of the small intestine

A. Main processes occur in small intestine: secretion, digestion, absorption, and propulsion. -1. Enterocytes produce multiple digestive enzymes, hormones, and mucus. -2. Enzymes are responsible for bulk of chemical digestion. -3. After nutrients are digested chemically, they are absorbed across enterocytes into either blood or lymph, along with water, vitamins, and other substances. -4. Also mixes and propels its contents along its length and into large intestine.

Describe the digestion and absorption of lipids

A. Majority (90%) of lipids taken in by diet are triglycerides. -1. Nonpolar lipids tend to stick together, forming large globules rather than distributing evenly in a water-based solution. B. Lipid globules can be broken up into smaller particles in two ways: -1. Mechanical digestion—mastication in mouth, churning in stomach, and segmentation in small intestine. -2. Bile salts in small intestine emulsify lipids. --a. Gives digestive enzymes enough surface area on which to work to efficiently digest lipids. C. Digestion Steps: -1. See figure 22.31 -2. Micelle: digested lipids coated in bile salts. D. Absorption Steps: 1. See figure 22.33. E. Lipids are not delivered directly to liver via hepatic portal vein after absorption. -1. Hepatic portal vein delivers leftover bile salts to liver, where they are used to make new bile. -2. Lipids travel within chylomicrons through lymphatic vessels and eventually to thoracic duct, where they join blood with rest of lymph. -3. As chylomicrons travel through blood capillaries, lipids are progressively removed and enter cells, where they can be used for a number of different purposes.

Describe the major functions of the digestive system.

A. Most fundamental function of digestive system is to take food into body and break it down into its component nutrients so that they can be used by body cells. B. Other functions include: 1. Playing a critical role in fluid, electrolyte, and acid-base homeostasis by taking in water and electrolytes via diet and delivering them to blood. 2. Ingesting vitamins and minerals. 3. Producing hormones. 4. Excreting metabolic wastes

Briefly explain regulation of motility by the endocrine and nervous systems

A. Motility, or movement, of alimentary canal is a key process in every region of canal. B. Each type of motility is regulated by nervous system and/or endocrine system. C. Nervous system regulation of motility consists of nerves of autonomic nervous system, or ANS. -1. Enteric nervous system, or ENS is a self-contained branch of autonomic nervous system that extends from esophagus to anus.

Describe the digestion and absorption of Nucleic Acids

A. Nucleic acids in food we eat begin chemical digestion in small intestine with help of pancreatic enzymes called nucleases. B. Nucleases catalyze reactions that break nucleic acids into individual nucleotides. C. Further digestion occurs via brush border enzymes. -1. Remove phosphate group and sugar from nucleotide to leave a phosphate ion, ribose or deoxyribose, and a nitrogenous base. D. These three molecules are absorbed via primary and secondary active transport mechanisms into capillaries in villi

Define the terms nutrient, essential nutrient, macronutrient, and micronutrient

A. Nutrient - molecule obtained from food that body requires for its metabolic processes. B. 5 main categories of nutrients. -1. Macronutrients - carbohydrates, proteins, and lipids. --a. Because they are required in relatively large amounts thus make up bulk of diet. -2. Micronutrients - vitamins and minerals. C. Essential nutrients - molecules that body is incapable of producing and must obtain from dietary sources. D. Macronutrients: see table 23.1 E. Micronutrients are not used as fuel but play critical roles in nearly all of body's physiological processes

Overview of Digestion and Absorption

A. Process of digestion breaks food down into smaller and smaller pieces until only individual nutrient molecules remain. B. Two types of digestion: *Mechanical digestion *Chemical digestion C. Most digestive enzymes catalyze hydrolysis reactions that use a water molecule to break a bond between two molecules. -1. Explains why so much water is secreted with fluids. -2. Water molecules are key components of reactions that chemically break down food molecules. 3. Digestive enzymes speed up these reactions by a process known as enzymatic hydrolysis. D. Once nutrients are digested into component molecules, they must enter body

Describe the acid secretion function of the stomach

A. Secretion 1. Acid secretion from stomach occurs continuously throughout day between meals, at what is known as basal rate. 2. During eating, secretion can be divided into three phases: -Cephalic Phase -Gastric Phase -Intestinal Phase

Describe the histology of the stomach. Define chyme.

A. Stomach has same four tissue layers as rest of alimentary canal; exceptions: -1. Additional oblique layer of smooth muscle allows stomach to perform churning. --a. Pummels food into a liquid called CHYME. -2. Mucosa of stomach is heavily indented to form deep structures called gastric pits. --a. Contains columnar cells and numerous goblet cells, both of which secrete a thick mucus that lines and protects cells of stomach from its own secretions. 3. Gastric gland contain both endocrine and exocrine cells. --a. Secrete hormones and an acidic gastric juice.

List the three pairs of salivary glands. List the two types of cells in a salivary gland and explain what product each produces and when.

A. Three pairs of salivary glands secrete saliva, a fluid containing water, enzymes, mucus, and other solutes, through a duct into oral cavity. -1. Submandibular, sublingual and parotid glands. B. Two main types of acinar cells in salivary glands: -1. Serous cells secrete a water-based fluid with enzymes and other solutes. --a. Generally released just before or during eating. -2. Mucous cells secrete mucus; primarily involved in keeping oral mucosa moist. --a. Released continually.

Describe the absorption of both types of vitamins

A. Vitamins - chemicals generally provided by diet that are involved in a host of metabolic reactions. B. Two types of vitamins: -1. Water-soluble vitamins, which are polar molecules. --a. Most water-soluble vitamins are absorbed in small intestine by diffusing through enterocytes' plasma membranes. -2. Fat-soluble vitamins, which are lipid-based and mostly nonpolar. --a. Fat-soluble vitamins are packaged into micelles with fats and other lipids and are absorbed with them.

Circular folds (1 of 3 folds of the small intestines)

B. Circular folds: largest type of folds, visible with naked eye as ridges in wall. -1. Folds also slow down transit of chyme through small intestine; gives nutrients more time to be digested, and small intestine cells (enterocytes) more time to absorb nutrients.

Describe motility in the small intestine during eating

B. During eating: peristalsis and segmentation -1. Peristalsis is accomplished by alternating contractions of longitudinal and circular layers of smooth muscle in muscularis externa. --a. Primary function is to propel chyme toward ileum and ultimately through ileocecal valve to cecum. -2. Segmentation, also known as intestinal churning, involves contractions of only circular layer of smooth muscle. --a. Produces a squeezing motion. --b. Primary functions are mechanical digestion and mixing chyme with intestinal and pancreatic enzymes as well as bile.

Four cell types in gastric glands

B. Four cell types in gastric glands 1. Enteroendocrine cells secrete hormones that influence digestion. -a. Gastrin stimulates acid secretion. 2. Chief cells secrete pepsinogen. -a. When pepsinogen encounters an acidic pH, it becomes pepsin. --1. Begins protein digestion in stomach. 3. Parietal cells secrete hydrochloric acid (HCl). -a. Responsible for acidic pH of gastric juice. -b. Acid activates pepsinogen, destroys many disease-causing organisms, and stimulates parietal cell production of chemical intrinsic factor; required for intestinal absorption of vitamin B12. 4. Mucous neck cells secrete acidic mucus. -a. Prevents neutralization of acid produced by parietal cells.

Describe the functions of the bacteria within the large intestines.

Bacteria in the Large Intestine A. About 10 times more bacteria in large intestine than cells in human body; bacteria make up as much as 60% of dry mass of feces. B. Bacteria, normal flora (gut flora) consist of about 500 different bacterial species that coexist with humans in a symbiotic (mutually beneficial) relationship. C. Functions: -1. Produce vitamins -such as vitamin K, which is necessary for blood clotting. -2. Metabolize undigested materials. -3. Deter growth of harmful bacteria. -4. Stimulate immune system - during infancy, normal flora induce immune tolerance to their own antigens; at same time, they stimulate development of mucosa-associated lymphoid tissue (MALT) and production of antibodies to pathogens.

. Long-term regulation of feeding including the hormones involved

C. Long-term regulation of feeding is primarily hormonal. -1. Leptin - hormone produced by adipocytes. --a. Stimulates satiety center and inhibits neurons in hunger center. -2. Ghrelin - hormone produced by stomach mucosal cells. --a. Stimulates neurons in hunger center to promote hunger. -3. Hunger center is also stimulated by a drop in leptin levels; allows hunger center neurons to become activated

. Discuss the basic functions of the oral cavity, the teeth, and the tongue. Include definitions of bolus, deglutition and mastication. PT 2

D. Posterior oral cavity, pharynx, and esophagus then deliver bolus to stomach through process of swallowing or DEGLUTITION. E. Teeth masticate, or chew, ingested food, grinding it into smaller pieces. -1. MASTICATION aids digestion by increasing overall surface area of food, giving digestive enzymes more places to catalyze reactions of chemical digestion. F. Tongue is involved during ingestion phase of digestion. -1. Movement of tongue during chewing helps turn food into a bolus. -2. Tongue also pushes the food against hard palate during chewing, which assists in mechanical digestion, and also push bolus posteriorly during swallowing.

Short-term regulation of feeding including the hormones involved

D. Short-term signals can also inhibit or stimulate feeding. 1. Insulin is released in response to feeding and has similar actions as leptin, which decreases food intake. 2. Feeding stretches stomach walls and initiates release of gastrointestinal hormones such as cholecystokinin. 3. Both stimulate vagus nerve to indirectly suppress hunger center and decrease release of hunger-related neurotransmitters (orexins and neuropeptide Y). E. Levels of certain molecules in blood can stimulate or inhibit these hypothalamic centers. -1. Example: low level of glucose in blood (hypoglycemia) stimulates hunger center and release of orexin

Explain the motility of the large intestine

D. Two main types of motility of proximal segment: -1. Type of segmentation (churning). --a. Circular muscle of each haustrum contracts repeatedly; swirls material around in haustrum. --b. Aids in water and electrolyte absorption primarily controlled by local neurons of ENS; triggered by stretch. -2. Propulsive motion known as a mass movement (mass peristalsis). --a. During a mass movement, multiple haustra undergo peristalsis; propels their contents toward distal large intestine. --b. Mass movements occur three to four times per day, and appear to be triggered by food consumption; initiates reflexes controlled by ENS. E. Distal large intestine is much less motile than proximal large intestine. -1. When mass movements force fecal material into normally empty rectum, it initiates parasympathetic-mediated defecation reflex.

Describe the three regulatory phases of the stomach. Define enterogastric reflex.

During eating, secretion can be divided into three phases: A. Cephalic Phase- mediated by sight, smell, taste, or even thought of food under direction of CNS. -1. Prepares stomach to receive food by increasing release of hydrogen ions into it. B. Gastric Phase- begins when food enters stomach. -1. Presence of food or partially digested protein stimulates acid secretion due to gastrin. C. Intestinal Phase- responsible for only about 10% of remaining acid secretion, after which it inhibits further acid secretion. -1. Triggered by presence of partially digested proteins in fluid entering duodenum; releases more gastrin. -2. Stimulatory effect of intestinal phase is brief; as chyme enters duodenum, declining pH and presence of lipids trigger enterogastric reflex; decreases vagal activity and acid secretion. -3. Secretin and gastric inhibitory peptide (GIP) from duodenum reduce acid secretion.

Define metabolism, catabolism, and anabolism, and identify the nutrients the body is able to use for fuel.

Metabolism A. Definition: sum of body's chemical reactions. 1. Series of enzyme-catalyzed reactions called metabolic pathways. B. Phases of Metabolism: -1. Catabolism - series of reactions in which one substance is broken down into smaller parts. --a. Process as a whole releases energy that cell can harness to drive other processes. --b. Body catabolizes three types of nutrient monomers to generate ATP. ---1. Glucose. ---2. Fatty acids. ---3. Amino acids. -2. Anabolism - series of reactions in which smaller molecules are combined to make a larger molecule. --a. Cells use smaller molecules to build larger macromolecules such as proteins, nucleic acids, lipids, and carbohydrates.

Define mineral and state the importance of minerals to the diet. List the minerals required for optimal health and state food sources to obtain minerals

Minerals: a mineral is any element other than carbon, hydrogen, oxygen, and nitrogen that is required by living organisms. a. Not used as fuels but are important components in many physiological processes. b. Seven major minerals are ions that are required in moderate amounts for optimal health: calcium, chloride, magnesium, phosphorus, potassium, sodium, and sulfur. c. Mineral-rich foods include fruits, vegetables, dairy products, and certain meats.

. Describe liver functions that pertain to digestion. Explain the role of bile. Define emulsification.

The Liver A. Main digestive function is to produce bile. -1. Bile: a liquid that contains multiple components, including water, electrolytes, and organic compounds. -2. Bile serves two critical functions. --a. Required for digestion and absorption of lipids. --b. Mechanism by which liver excretes wastes and other substances that kidneys cannot excrete. -3. Liver produces bile continually but generally does not secrete it at a basal rate. B. Bile- one of bile's main organic compounds is bile salts. -1. Bile salts are amphiphilic, meaning they have both polar and nonpolar parts. --a. Allows bile salts to interact with both lipids and watery environment of small intestine. -2. Coat lipids in duodenum and physically break them apart into smaller pieces. --a. Process known as emulsification. 3. Mechanical digestion necessary for chemical digestion and absorption of lipids. 4. Bile also contains varying amounts of materials that liver excretes, including cholesterol, waste products, and toxins such as heavy metals.

Describe the pancreas and its digestive functions.

The Pancreas A. For digestive system: secretes enzymes that are released into ducts of pancreas that empty into alimentary canal; makes pancreatic juice. B. Pancreatic juice - collective secretions of pancreatic acinar and duct cells. -1. Consists of water and multiple digestive enzymes and other proteins. -2. Duct cells also secrete bicarbonate ions, a base, which make pancreatic juice alkaline. --a. Alkaline juice helps neutralize acidic chyme that enters duodenum from stomach; protects duodenum from damage by acid. -3. Its digestive enzymes, secreted by acinar cells, are crucial in chemical digestion. --a. Catalyze reactions that digest carbohydrates, proteins, lipids, and nucleic acids. C. Pancreatic secretion occurs at a basal rate between meals; during eating, pancreatic secretion rises due to parasympathetic and hormonal stimulation.