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A&P ch. 16, 23, 24
endocrine, digestive, and nutrition systems
| Term | Definition |
|---|---|
| Mesentary | a double layer of peritoneum Routes for blood vessels, lymphatics, and nerves Holds organs in place and stores fat |
| Retroperitoneal | organs lie posterior to the peritoneum |
| Intraperitoneal (peritoneal) | organs are surrounded by the peritoneum |
| Peritoneum | serous membrane of the abdominal cavity (2 layers) Visceral peritoneum Parietal peritoneum |
| Visceral peritoneum | on external surface of most digestive organs |
| Parietal peritoneum | lines the body wall |
| Peritoneal cavity | Between the two peritoneums Fluid lubricates mobile organs |
| The alimentary canal or gastrointestinal (GI) tract | digests and absorbs food 2 parts: Alimentary canal Accessory digestive organs |
| Alimentary canal | mouth, pharynx, esophagus, stomach, small intestine, and large intestine |
| Accessory digestive organs | teeth, tongue, gallbladder, salivary glands, liver, and pancreas |
| Arteries | Hepatic, splenic, and left gastric Inferior and superior mesenteric |
| Hepatic portal circulation | Drains nutrient-rich blood from digestive organs Delivers it to the liver for processing |
| Histology of the Alimentary Canal | 4 layers Mucosa (most inner) Submucosa Muscularis externa Serosa (most outer) |
| Mucosa | Lines the lumen Three sublayers: epithelium, lamina propria muscularis mucosae |
| Functions of mucosa | Secretes mucus, digestive enzymes and hormones Absorbs end products of digestion Protects against infectious disease |
| Muscularis mucosae (layer of mucosa) | smooth muscle cells that produce local movements of mucosa |
| Lamina Propria (layer of mucosa) | Loose areolar connective tissue |
| Simple columnar epithelium and mucus-secreting goblet cells (layer of mucosa) | Stomach and small intestine mucosa contain: Enzyme-secreting cells Hormone-secreting cells |
| submucosa | dense connective tissue, blood and lymphatic vessels, lymph nodes, and nerves |
| Muscularis externa | responsible for segmentation and peristalsis (movement of GIT) inner: circular outer: longitudinal |
| serosa | the protective visceral peritoneum Replaced by the fibrous adventitia in the esophagus Retroperitoneal organs have both an adventitia and serosa |
| Sympathetic | impulses inhibit secretion and motility |
| Parasympathetic | impulses stimulate (motility and secretion) |
| Myenteric nerve plexus | Controls GI tract motility |
| Submucosal nerve plexus | Regulates glands and smooth muscle in the mucosa |
| Intrinsic nerve supply of the alimentary canal | Submucosal nerve plexus Myenteric nerve plexus |
| retroperiteneal organs | duodenum pancreas ascending colon descending colon |
| difference between colon and large intestine | colon is a part of the large intestine |
| stratified squamous epithelium in the digestive tract | mouth pharynx esophagus anus |
| teeth | Primary and permanent dentitions are formed by age 21 20 deciduous teeth erupt (6–24 months of age) 32 permanent teeth |
| permanent teeth | 32 All except third molars erupt by the end of adolescence |
| deciduous teeth | 20 Roots are resorbed, teeth fall out (6–12 years of age) as permanent teeth develop |
| Tooth structure | crown root cementum periodontal ligament dentin pulp cavity pulp root canal |
| crown | the exposed part above the gingiva (gum) Covered by enamel: the hardest substance in the body (calcium) |
| root | portion embedded in the jawbone Connected to crown by neck |
| cementum | calcified connective tissue Covers root and attaches it to the periodontal ligament |
| periodontal ligament | Forms fibrous joint called a gomphosis |
| dentin | bonelike material under enamel maintained by osteoblasts |
| pulp cavity | cavity surrounded by dentin |
| pulp | connective tissue, blood vessels, and nerves |
| root canal | extends from pulp cavity to the apical foramen of the root |
| Salivary glands | Parotid gland Submandibular gland Sublingual gland |
| Parotid gland | Anterior to the ear external to the masseter muscle Parotid duct opens into the vestibule next to second upper molar |
| Submandibular gland | Medial to the body of the mandible Duct opens at the base of the linguinal frenulum |
| Sublingual gland | Anterior to the submandibular gland under the tongue Opens ducts |
| Pharynx | Oropharynx and laryngopharynx Allow passage of food, fluids, and air Stratified squamous epithelium lining skeletal muscle layers: inner longitudinal, outer pharyngeal constrictors |
| Esophagus | Flat muscular tube from laryngopharynx to stomach Esophageal mucosa contains stratified squamous epithelium Changes to simple columnar at the stomach Esophageal glands in submucosa secrete mucus to aid in bolus movement |
| Where does the esophagus pierce the diaphragm? | esophageal hiatus |
| Where does the esophagus join the stomach? | at the cardiac orifice |
| Heartburn | stomach acid regurgitating into esophagus First symptom of (GERD) Caused by excess food/drink, extreme obesity, pregnancy, running OR hiatal hernia: (part of stomach protrudes above diaphragm) lead to issues with esophagus |
| Gross anatomy of stomach | Cardiac region (cardia) Fundus Body Pyloric region Greater curvature Lesser omentum Greater omentum |
| Greater curvature | Convex lateral surface |
| Lesser curvature | Concave medial surface |
| Lesser omentum | From the liver to the lesser curvature |
| Greater omentum | Drapes from greater curvature Anterior to the small intestine |
| Cardiac region (cardia) | Surrounds the cardiac orifice |
| Fundus | Dome-shaped region beneath the diaphragm |
| body | midportion |
| Pyloric region | antrum, pyloric canal, and pylorus Pylorus is continuous with the duodenum through the pyloric valve (sphincter) |
| ANS nerve supply | Sympathetic via splanchnic nerves and celiac plexus Parasympathetic via vagus nerve |
| Blood supply | Celiac trunk Veins of the hepatic portal system |
| cell types in gastric gland | Mucous neck cells Parietal cells Chief cells Enteroendocrine cells |
| Mucous trunk | secrete thin, acidic mucus |
| Parietal cells | secrete HCl and Intrinsic factor |
| Chief cells | secrete pepsinogen |
| Enteroendocrine cells | hormones - gastrin |
| Small intestine subdivisions | Duodenum Jejunum Illeum (attached posteriorly by mesentery) |
| duodenum | retroperitoneal |
| Jejunum | attached posteriorly by mesentery |
| Illeum | attached posteriorly by mesentery |
| Small intestine | Major organ of digestion and absorption 2–4 m long; from pyloric sphincter to ileocecal valve |
| Duodenum | The bile duct and main pancreatic duct Join at the hepatopancreatic ampulla Enter the duodenum at the major duodenal papilla Are controlled by the hepatopancreatic sphincter |
| Circular folds (Modification) | Permanent (~1 cm deep) Force chyme to slowly spiral through lumen |
| Structural modifications | Increase surface area of proximal part for nutrient absorption Circular folds (plicae circulares) Villi Microvilli |
| Villi | Motile fingerlike extensions (~1 mm high) of the mucosa Villus epithelium Simple columnar absorptive cells (enterocytes) Goblet cells |
| Microvilli | Projections (brush border) of absorptive cells Bear brush border enzymes |
| Liver associated structures | Lesser omentum anchors liver to stomach Hepatic artery and vein at the porta hepatis Bile ducts |
| Bile ducts | Common hepatic duct leaves the liver Cystic duct connects to gallbladder Bile duct formed by the union of the above two ducts |
| Liver lobules | Hexagonal structural and functional units Filter and process nutrient-rich blood Composed of plates of hepatocytes (liver cells) Longitudinal central |
| Gallbladder | Thin-walled muscular sac on the ventral surface of the liver Stores and concentrates bile by absorbing its water and ions Releases bile via the cystic duct, which flows into the bile duct |
| Pancreas location | Location Mostly retroperitoneal, deep to the greater curvature of the stomach Head is encircled by the duodenum; tail abuts the spleen |
| Pancreas endocrine function | Pancreatic islets secrete insulin and glucagon |
| Pancreas exocrine function | Acini (clusters of secretory cells) secrete pancreatic juice granules of secretory cells contain digestive enzymes |
| Large intestine features | Teniae coli Haustra Epiploic appendages |
| Teniae coli | Three bands of longitudinal smooth muscle in the muscularis |
| Haustra | Pocketlike sacs caused by the tone of the teniae coli |
| Epiploic appendages | Fat-filled pouches of visceral peritoneum |
| Large intestine regions | Cecum (pouch with attached vermiform appendix) Colon Rectum Anal canal |
| which parts of the large intestine are retroperitoneal? | Ascending colon and descending colon are retroperitoneal |
| Function of mesocolons? | Transverse colon and sigmoid colon are anchored via mesocolons (mesenteries) |
| Rectum | Three rectal valves stop feces from being passed with gas |
| Anal cavity | The last segment of the large intestine |
| Sphincters | Internal anal sphincter—smooth muscle External anal sphincter—skeletal muscle |
| Large intestine microscopic anatomy | Mucosa of simple columnar epithelium except in the anal canal (stratified squamous) Abundant deep crypts with goblet cells Superficial venous plexuses of the anal canal form hemorrhoids if inflamed |
| Digestive process essential activities | ingestion Propulsion & mechanical digestion Chemical digestion absorption defecation |
| Digestive process | The GI tract is a “assembly” line Nutrients become more available to the body in each step |
| Enteric nervous system | Short relexes Long reflexes |
| Short relexes | mediated by enteric nerve plexuses (gut brain); respond to stimuli in GI tract |
| Long reflexes | respond to stimuli arising inside or outside of gut, such as from autonomic nervous system Parasympathetic system enhances digestive process Sympathetic system inhibits digestion |
| Mucosa | main site of nutrient absorption |
| mesentery | Omenta is the special name for part of the mesentery. It holds the organs of the abdomen in place. It provides a route for blood vessels, lymphatics, and nerves to reach the digestive viscera |
| Muscularis externa | Responsible for segmentation and peristalsis |
| accessory organs of the digestive system? | teeth tongue salivary glands |
| the major means of propulsion in the digestive system | Peristalsis |
| serosa | Protective outermost layer of the alimentary canal |
| Chemical digestion. | Enzymatic degradation of foodstuffs into simpler molecules |
| layers of the wall of the GI tract | Mucosa, submucosa, muscularis externa, serosa |
| The short reflexes in the digestive system are mediated by | the enteric nerve plexuses |
| absorption | Passage of digested materials from the lumen of the GI tract into the blood or lymph |
| visceral peritoneum | serous membrane that covers the external surface of most digestive organs is called the |
| which cells produce HCI | parietal cells |
| activation of pancreatic proteases occurs in the __________. | duodenum |
| Pepsin enzymatically digests | protein |
| intestinal phase of gastric regulation | the stomach is initially stimulated and later inhibited |
| found in pancreatic secretions | Bicarbonate ions Procarboxypeptidase Chymotrypsinogen |
| characteristics of the liver | It is highly regenerative. It stores glucose as glycogen. It has a role in detoxifying the blood. |
| gastrin | Stimulated by partially digested proteins in the stomach and increases gastric gland secretions |
| CCK | Increases the secretions of enzyme-rich pancreatic juice |
| What is the main organic molecule digested in the stomach? | proteins |
| What substances from different organs would mix together at the hepatopancreatic ampulla? | Bile and pancreatic enzymes |
| Some aspects of the __________ phase of gastric secretion may be considered conditioned reflexes. | cephalic |
| Which of the following products does the stomach produce? | HCI and intrinsic factor |
| Digestion of carbohydrates and proteins by brush border enzymes occurs within the __________ of the small intestine. | microvilli |
| The only stomach function that is essential to life is __________. | the secretion of intrinsic factor |
| Functions of saliva | Cleanses mouth Dissolves food chemicals for taste Moistens food; compacts into bolus Begins breakdown of starch with enzyme amylase |
| mechanical digestion | food is "chopped up" with teeth |
| Peristalsis | adjacent segments of the ailmentary canal organs alternately contract and relax (food is moved distally) little mixing, mostly for propulsion |
| Segmentation | nonadjacent segments of the ailmentary canal contract and relax (food is moved forward then backwards) mostly mixing, little propulsion |
| Enteric Nervous System (the two reflexes it participates in) | Short reflexes Long reflexes |
| Short reflexes | mediated by enteric nerve plexuses (gut brain); respond to stimuli in GI tract |
| Long reflexes | respond to stimuli arising inside or outside of gut, such as from autonomic nervous system Parasympathetic system enhances digestive process Sympathetic system inhibits digestion |
| regulating digestive activity | Mechanical and chemical stimuli Effectors Neurons |
| Effectors | smooth muscle and glands |
| Neurons | intrinsic and extrinsic) and hormones and glands |
| What do Mechanoreceptors and chemoreceptors respond to? | stretch changes in osmolarity Changes in pH presence of substrate and end products of digestion |
| The GI tract initiates reflexes that activate or inhibit digestive glands and stimulate smooth muscle to mix and move lumen contents | true |
| Salivary glands | composed of 2 types of secretory cells Serous cells Mucous cells |
| Serous cells | produce watery secretion, enzymes, ions, bit of mucin |
| mucous cells | produce mucous |
| Composition of saliva | 97–99.5% water, slightly acidic solution containing Electrolytes—Na+, K+, Cl–, PO4 2–, HCO3– Salivary amylase Mucin |
| Extrinsic salivation | Ingested food - stimulates chemoreceptors and mechanoreceptors in the mouth Salivatory nuclei in the brain stem - impulses along parasympathetic fibers in cranial nerves VII and IX |
| Sympathetic nervous system | stimulation inhibits salivation and causes dry mouth |
| Mouth | Ingestion Mechanical digestion Mastication is partly voluntary, partly reflexive Chemical digestion (salivary amylase) Swallowing Deglutition (swallowing) |
| Deglutition | Involves the tongue, soft palate, pharynx, esophagus, and 22 muscle groups |
| Deglutition phases | Pharyngeal-esophageal phase Buccal phase |
| Buccal phase | Voluntary contraction of the tongue |
| Pharyngeal-esophageal phase | Involuntary Control center in the medulla and lower pons |
| Bolus | saliva mixed partially digested food which is swallowed |
| Stomach | Holds ingested food Degrades this food both physically and chemically Delivers chyme to the small intestine Enzymatically digests proteins with pepsin Secretes intrinsic factor factor required for absorption of vitamin B12 |
| Gastric Gland Secretion types | Mucous nek cells Parietal cell secretions Chief secretions |
| Mucous nek cells | thin, acidic mucous |
| Parietal cell secretions | HCl Intrinsic factor required for absorption of vitamin B12 in small intestine |
| Chief secretions | Pepsinogen - inactive enzyme Activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism) |
| Enteroendocrine cells | Secrete chemical messengers into the lamina propria Paracrines Serotonin and histamine Hormones Somatostatin and gastrin |
| Mucosal barriers | Mucosal barrier protects stomach and is created by three factors Thick layer of bicarbonate-rich mucus Tight junctions between epithelial cells |
| Gastritis | Inflammation caused by anything that breaches stomach’s mucosal barrier |
| Peptic or gastric ulcers | Can cause erosions in stomach wall Most ulcers caused by bacterum Helicobacter pylori Can also be caused by non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin |
| Digestive processes in the stomach | Carries out breaking down of food Serves as holding area for food Delivers chyme to small intestine Denatures proteins by HCI |
| pepsin | carries out enzymatic digestion of proteins |
| what is the only necessary function of the stomach for survival? | secretion of intrinsic factor for vitamin B12 absorption |
| Neural mechanisms | Vagus nerve stimulation increases secretion Sympathetic stimulation decreases secretion |
| Hormonal mechanisms | Gastrin stimulates enzyme and HCI secretion Gastrin antagonists are secreted by small intestine |
| phases of gastric secretion | Cephalic (reflex) phase Gastric phase Intestinal phase |
| Cephalic phase (reflex phase) | few minutes prior to food entry thought, sight, smell, taste of food |
| Gastric phase | 3–4 hours after food enters the stomach |
| Intestinal phase | brief stimulatory effect as partially digested food enters the duodenum, followed by inhibitory effects (enterogastric reflex and enterogastrones) |
| where is Gastric Contractile Activity most vigorous? | pylorus |
| Chyme | Delivered in about 3 ml spurts to the duodenum, or Forced backward into the stomach |
| Vomiting (emesis) | Extreme stretching Intestinal irritants, such as bacterial toxins, excessive alcohol, spicy food, certain drugs |
| Intestinal juice | Secreted in response to distension or irritation of the mucosa Slightly alkaline and isotonic with blood plasma Largely water, enzyme-poor, but contains mucus Facilitates transport and absorption of nutrients |
| Bile | Yellow-green, alkaline solution containing |
| bile salts | cholesterol derivatives that function in fat emulsification and absorption |
| Bilirubin: | pigment formed from heme |
| Enterohepatic circulation | Recycles bile salts Bile salts duodenum reabsorbed from ileum hepatic portal blood -> liver -> secreted into bile |
| Protease activation in duodenum | Trypsinogen is activated to trypsin by brush border enzyme enteropeptidase Procarboxypeptidase and chymotrypsinogen are activated by trypsin |
| Bile secretion is stimulated by... | Bile salts in enterohepatic circulation Secretin from intestinal cells exposed to HCl and fatty chyme |
| Gallbladder contraction is stimulated by... | Cholecystokinin (CCK) from intestinal cells exposed to proteins and fat in chyme Vagal stimulation (minor stimulus) |
| major nutrients | lipids, carbs, protein |
| Food groups represented on MyPlate | dairy grains fruits vegetables |
| Monosaccharide & disaccharides | Sugars (mono- and disaccharides) in fruits, sugarcane, sugar beets, honey, and milk |
| Polysaccharides | insoluble fibers soluble fibers |
| insoluble fiber | cellulose in vegetables provides roughage |
| soluble fiber | pectin in apples and citrus fruits reduces blood cholesterol levels |
| What role does excess glucose play? | converted to glycogen or fat, then stored |
| Glucose | Glucose: fuel most used by cells to make ATP Some cells use fat for energy Neurons and RBCs rely entirely on glucose Neurons die quickly without glucose |
| Carbohydrates daily dosage | 45-65% of caloric intake should be mostly complex carbohydrates (whoke grains and vegetables) |
| Triglycerides | most abundant form Found in saturated fats in meat, dairy foods, tropical oils, or hydrogenated oils Unsaturated fats found in seeds, nuts, olive oil, and most vegetable oils |
| Cholesterol | found in egg yolk, meats, organ meats, shellfish, and milk products Liver makes ~85% cholesterol |
| Essential fatty acids | linoleic and linolenic acid found in most oils - must be eaten |
| Role of lipids: Adipose tissue | protection, insulation, fuel storage |
| Role of lipids: Phospholipids | essential in myelin sheaths and cell membranes |
| Role of lipids: Cholesterol | stabilizes membranes; precursor of bile salts, steroid hormones |
| Role of lipids: Prostaglandins | - smooth muscle contraction, BP control, inflammation |
| other roles of lipids | Help absorb fat-soluble vitamins Major fuel of hepatocytes and skeletal muscle |
| Dietary recommendations: lipids | American Heart Association recommendations Fats: 30% or less of total caloric intake Saturated fats: 10% or less of total fat intake Cholesterol: no more than 300 mg/day (about 1-1/2 egg yolks) |
| Types of proteins | complete proteins incomplete proteins |
| complete proteins | Animal products (eggs, milk, fish, most meats), soybeans, Contain all needed essential amino acids |
| incomplete proteins | Legumes, nuts, and cereals contain (lack some essential amino acids) |
| Uses of protein in the body | Structural materials: makes cell membrane Functional molecules Nitrogen balance |
| Nitrogen balance | Homeostatic state: protein synthesis = rate of breakdown and loss (+) balance: synthesis exceeds breakdown (children, pregnant women, tissue repair) (-) balance: breakdown > synthesis (ex: stress, burns, infection, injury, poor dietary proteins) |
| daily diet breakdown: | carbs: 45-65% protein: 10-20% lipids: less than 30% |
| role of vitamins | organic compounds that function as coenzymes most must be ingested except vitamin D, B, K, and beta carotene |
| types of vitamins | water-soluble fat-soluble |
| Vitamin B deficiency | beriberi |
| B12 deficiency | anemia |
| folic acid deficiency | spina bifida and anemia |
| vitamin C deficiency | scurvy |
| vitamin A deficiency | night blindness |
| vitamin D deficiency | children: rickets adults: osteomalacia |
| vitamin K deficiency | defective blood clotting |
| minerals | Calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium |
| Anabolism | synthesis of large molecules from small ones (example: triglycerides |
| Catabolism | hydrolysis of complex structures to simpler ones |
| Metabolism | sum of all biochemical reactions inside a cell involving nutrients |
| Cellular respiration | catabolic breakdown of food fuels whereby energy from food is captured to form ATP in cells |
| Phosphorylation | enzymes shift high-energy phosphate groups of ATP to other molecules Phosphorylated molecules become activated to perform cellular functions |
| How many stages are there to digesting nutrients? | three stages |
| Stage one of digesting nutrients | Digestion, absorption, and transport to tissues – GI tract |
| Stage two of digesting nutrients | Cellular processing (in cytoplasm) – tissue cells Synthesis of lipids, proteins, and glycogen, or Catabolism (glycolysis) into pyruvic acid and acetyl CoA |
| Stage three of digesting nutrients | Oxidative breakdown of intermediates into CO2, water, and ATP –mitochondria |
| Glucose catabolism reaction formula | C6H12O6 + 6O2 6H2O + 6CO2 + 32 ATP + heat |
| three pathways to complete glucose catabolism | Glycolysis Krebs cycle Electron transport chain and oxidative phosphorylation |
| Glycolysis | Also called glycolytic pathway Anaerobic: occurs despite presence/absence of O2 Occurs in cytosol Glucose -> 2 pyruvic acid molecules ATP – net gain of 2 ATP |
| Krebs Cycle | Also called Citric acid cycle Occurs in mitochondrial matrix Fueled by pyruvic acid and fatty acids pyruvic acid enters transitional phase pyruvic acid is converted to acetyl coenzyme A (acetyl CoA) |
| Glycogenesis | formation of glycogen (glucose -> glycogen) |
| Glycogenolysis | breakdown of glycogen (glycogen -> sugar) |
| Gluconeogenesis | AA and FA -> glucose |
| Lipogenesis: | making of fat |
| lipolysis | breakdown of stored fats into glycerol and fatty acids; reverse of lipogenesis |
| What are fatty acids prefered by? | liver, cardiac muscle, resting skeletal muscle for fuel |
| When does lipolysis occur? | when carb intake is inadequate |
| amino acid degredation | Transamination Oxidative deamination Keto acid modification |
| Transamination | transfer their amine group and become glutamic acid |
| Oxidative deamination | In liver, amine group is removed as ammonia (NH3) |
| Keto acid modification | -Keto acids formation |
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