Digestive System PDF

v Omental bursa – a long, double fold of DIGESTIVE SYSTEM mesentery that extends inferiorly from § With the help of the circulatory system, is like a the stomach before looping back to the gigantic ‘meals on w...

v Omental bursa – a long, double fold of DIGESTIVE SYSTEM mesentery that extends inferiorly from § With the help of the circulatory system, is like a the stomach before looping back to the gigantic ‘meals on wheels’, serving 100 T transverse colon to create a customers the nutrients they need cavity/pocket § Has its own quality control and waste disposal v Mesentery proper – attaches the small methods intestine to the posterior abdominal wall FUNCTIONS (IDEA) Retroperitoneal – abdominal organs that have no 1. Ingestion of food. mesenteries; duodenum, pancreas, ascending + 2. Digestion of food. descending colon, rectum, kidneys, adrenal glands, 3. Elimination of wastes. urinary bladder 4. Absorption of nutrients. ORAL CAVITY, PHARYNX, AND ESOPHAGUS ANATOMY AND HISTOLOGY Anatomy of Oral Cavity Digestive Tract / Gastrointestinal Tract § Bounded by the lips and cheeks ++ contains the § Oral cavity, pharynx, esophagus, stomach, small teeth and tongue intestine, large intestine, anus Lips – muscular structures formed by the orbicularis Four Tunics oris muscle 1. Mucosa § Innermost tunic Cheeks – buccinators muscles flatten the cheeks against § Consists of mucous epithelium, lamina propria teeth (loose CT), muscularis mucosae (thins SM layer) § Mouth, esophagus, anus; resists abrasion Mastification – begins the process of mechanical digestion § Stomach, intestine; absorbs and secrets Tongue – plays a major role in the process of 2. Submucosa swallowing; major sensory organ for taste; one of the § Thick layer of loose CT, consists of nerves, blood major organs of speech vessels, small glands v Frenulum – thin fold of tissue inferior to the § Plexus – extensive network of nerve cell tongue processes (innervated by the autonomic nerves) Teeth 3. Muscularis § 32 teeth in normal adult mouth § Consists of circular SM (inner), longitudinal SM (outer) § Located in the mandible and maxillae § Enteric nervous system – composed of the 1. Incisor – to cut nerve plexuses of the submucosa and 2. Canine – to tear muscularis; controls movement and secretion 3. Premolars within the tract 4. Molars 5. Wisdom teeth – third molars 4. Serosa § Outermost layer Permanent teeth – secondary teeth § Consists of the peritoneum (smooth epithelial layer + underlying CT) Primary teeth – deciduous teeth; milk or baby teeth § Adventitia – connective tissue; regions of the DT not covered by the peritoneum Parts a. Crown Peritoneum b. Cusps 1. Visceral Peritoneum / Serosa – serous c. Neck membrane that covers the organs d. Root 2. Parietal Peritoneum – serous membrance that Pulp cavity – center of the tooth; contains blood vessels covers the wall of the abdominal cavity nerves, and pulp (connective tissue) Mesenteries – CT sheets that hold the abdominal cavity Dentin – bonelike tissue that surrounds the pulp cavity organs in place a. Lesser omentum – connects the lesser curvature Enamel – extremely hard, acellular substance that covers of the stomack to the liver and diaphragm the dentin of the tooth drown b. Greater omentum – connects the greater Cementum – covers the surface of the dentin in the root; curvature of the stomach to the transverse colon anchors the tooth in the jaw and posterior body wall M A V M. Alveoli (along the alveolar process of mandible x Esophagus maxillae) – where the teeth are rooted § Muscular tube that ransports food from the pharynx to the stomach Gingiva – dense fibrous CT and most stratified § Esophageal sphincters – regulate the movement squamous epithelium that covers the alveolar processes of food into and out of the esophagus § Cardiac sphincter – lower ES Periodontal ligaments – CT fibers that extend from the alveolar walls that hold the teeth in place Swallowing / Deglutition 1. Voluntary Phase Dental caries / Tooth decay – result of the breakdown of § Bolus (mass of food) us formed in the mouth enamel by acids produced by bacteria on tooth surface § Bolus is pushed by the tongue forcing in into the oropharynx Periodontal disease – inflammation x degeneration of the periodontal ligaments, gingiva, alveolar bone 2. Pharyngeal Phase § A reflex initiated when a bolus of food Palate and Tonsils stimulates receptors in the oropharynx Palate – roof of the oral cavity; prevents food from § Epiglottis – tipped posteriorly to cover the passing into the nasal cavity during chewing and larynx swallowing a. Hard palate – anterior part that contains bone 3. Esophageal Phase b. Soft palate – posterior portion that consists of skeletal muscle _ CT § Responsible for moving food form the pharynx to the stomach v Uvula – grape-like; posterior extension of the soft palate § Peristaltic waves – muscular contractions of the esophagus Tonsils – protect against pathogens from entering the STOMACH nose and mouth § Functions primarily as a storage and mixing Salivary Glands chamber for ingested food § Produce saliva (serous + mucous fluids) Anatomy 3 Pairs of SG Gastroesophageal opening – opening from the 1. Parotid glands – largest; serous glands located esophagus ino the stomach anterior to each ear Cardiac region – region of t around the 2. Submandibular glands – produce more serous gastroesophageal opening; near the heart than mucous secretions 3. Sublingual glands – smallest; produce primarily mucous secretions Fundus – most superior part of the stomach Mumps – inflammation of the parotid gland caused by Body – largest part of the stomach viral infection v Greater curvature v Lesser curvature Saliva § Helps keep the oral cavity moist Pyloric opening – opening from the stomach into the small intestine § Contains enzymes that begin the process of digestion Pyloric sphincter – thick ring of smooth muscle Salivary amylase – a digestive enzyme that breaks the Pyloric region – region near the pyloric opening covalent bonds bet. glucose molecules (starch) and other polysaccharides; enhances the sweet taste of food Outer longitudinal, middle circular, and inner obique Lysozyme – enzyme that has weak antibacterial action layer – produce a churning action in the stomach Mastification Rugae – large folds where the submucosa and mucosa are thrown into when the stomach is empty § Breaks large food particles into many small ones § Increases the efficiency of digestion Gastric pits – openings for the gastric glands; formed by simple columnar epithelium Pharynx § Throat Epithelial cells of the Stomach § Connects the mouth with the esophagus 1. Surface mucous cells – inner surface of stomach § Oropharynx + laryngopharynx – transmit food & lining the gastric pits; coats and protects the § Contains pharyngeal constrictor muscles stomach lining 2. Mucous neck cells – produce mucus M A V M.  3. Parietal cells – produce hydrochloric acid & Common bile duct (liver) and pancreatic duct intrinsic factor (pancreas) – join and empty into the duodenum 4. Endocrine cells – produce regulatory chemicals 5. Chief cells – produce pepsinogen (precursor of Increased surface area the protein digesting enzyme pepsin) 1. Circular folds – formed by mucosa and submucosa that run perpendicular to the long Secretions of the Stomach axis of the digestive tract Chyme – semifluid mixture (food + stomach secretions) 2. Villi – formed by tiny, fingerlike projections of the mucosa 1. Hydrochloric acid kills microorganisms and 3. Microvilli – numerous cytoplasmic extensions activates pepsin on the surface of the villi 2. Pepsin breaks covalent bond of proteins to form smaller peptide chains. Lacteal – lymphatic capillary 3. Mucus lubricates and protects epithelial cells from the damaging effect of acidic chime + Simple Columnar Epithelium pepsin 1. Absorptive cells – have microvilli, produce 4. Intrinsic factor binds with vit. B12 (DNA digestive enzymes, absorb digested food synthesis and RBC prod.) and makes it more 2. Goblet cells – produce a protective mucus readily absorbed in the small intestine 3. Granular cells – help protect the intestinal epithelium from bacteria Regulation of Stomach Secretions 4. Endocrine cells – produce regulatory hormones 1. Cephalic phase – stomach secretions are initiated by the sight, smell, taste, or thought of Intestinal glands – epithelial cells produced within food tubular galnds of mucosa 2. Gastric phase – partially digested proteins and distention of the stomach promote secretion Duodenal glands – mucous glands in the submucosa of Ø Gastrin – hormone that enters the the duodenum circulation and is carried back to the stomach Peyer patches – clusters of lymphatic nodules along the 3. Intestinal phase – acidic chime in the digestive tract duodenum stimulates neuronal reflexes and the secretion of hormones that inhibit gastric Ileocecal junction – where the ileum connects to the secretions by negative feedback loops large intestine Ø Secretin – hormone that inhibits gastric secretions; released from the duodenum Ileocecal sphincter – ring of smooth muscle in response to low pH Ø Cholecystokinin – major inhibitor of Ileocecal valve – allow intestinal contents to move from gastric motility; released from the the ileum to the large intestine; but not in opposite duodenum initiated by fatty acids and direction peptides Secretions of the Small Intestine Movement in the Stomach 1. Peptidases – break peptide bonds in proteins to § Increased motility = increases emptying form amino acids § Distention of stomach = increases gastric motility 2. Disaccharidases – break down disaccharides (maltose) into monosaccharides (glucose) A. Mixing waves – thoroughly mix ingested food with stomach secretions to form chime Movement of the Small Intestine Ø Fluid part of chime – pushed toward A. Peristaltic contractions – proceed along the the pyloric sphincter length of the intestine for variable distances; causes the chime to move along the small Ø Solid center – moves back toward the intestine body of the stomach B. Segmental contractions – propagate for shot B. Peristaltic waves – force the chime toward and distances; mix intestinal contents through the pyloric sphincter LIVER AND PANCREAS SMALL INTESTINE Anatomy of Liver § Major site of digestion and absorption of food Major Lobes § Major function is the absorption of nutrients 1. Right lobe 2. Left lobe Anatomy 1. Duodenum – 12 in. long Falciform ligament – CT septum that separates the right 2. Jejunum – 2.5 m long; makes up 2/5 and left lobe of the liver 3. Ileum – 3.5 m long; makes up 3/5 M A V M. Smaller Lobes Pancreatic islet / Islets of Langerhans – endocrine part; 1. Caudate lobe produce insulin and glucagon 2. Quadrate lobe Compound acinar gland – exocrine part Porta – gate through which blood vessels, ducts, and nerves enter and exit the liver Acini – produce digestive enymes Sources of Blood in the Liver Pancreatic duct – formed by larger ducts from clusters 1. Hepatic artery – takes oxygen-rich blood to the of acini liver; supplies liver with oxygen 2. Hepatic portal vein – oxygen-poor blood but Functions of the Pancreas rich in nutrients Major Proteolytic enzymes – continue protein digestion that began in the stomach Hepatic veins – where blood exits the liver and empty 1. Trypsin into the inferior vena cava 2. Chymotrypsin 3. Carboxypeptidase Portal Triads 1. Hepatic artery Pancreatic amylase – continues polysaccharide digestion 2. Hepatic portal vein that began in the oral cavity 3. Hepatic duct Lipase – lipid-digesting enzyme Hepatic cords – located bet. the center and margins of each lobule Nucleases – enzymes that degrade DNA and RNA to their component nucleotides Hepatocytes – platelike groups that form the hepatic cords LARGE INTESTINE Anatomy Hepatic sinusoids – blood channels that separates the Cecum hepatic cords from one another § Proximal end of the large intestine Central vein – where mixed blood flows toward the Appendix – 9 cm tube attached to the cecum center of each lobule Colon Bile canaliculus – a cleftlike lumen bet. the cells of each 1. Ascending colon hepatic cord 2. Transverse colon 3. Descending colon Common hepatic duct – right + left hepatic ducts 4. Sigmoid colon Common bile duct – common hepatic duct + cystic duct Crypts – straight, tubular glands in the mucosal lining of the colon Gallbladder – stores and concentrates bile Teniae coli – three bands Duodenal papilla – where the common bile duct joind the pancreatic duct and opens into the duodenum Rectum § Straight, muscular tube that begins at the Functions of the Liver termination of sigmoid colon & ends at the anal 1. Digestion canal 2. Excretion 3. Nutrient storage Anal Canal 4. Nutrient conversion § Begins at the inferior end of the rectum and ends 5. Detoxification of harmful chemicals at the anus (external digestive tract opening) 6. Synthesis of new molecules Internal anal sphincter – smooth muscle layer at Bile – dilutes and neutralizes stomach acid; dramatically superior end increases the efficiency of fat digestion and absorption; stimulated by secretin External anal sphincter – skeletal muscle at inferior end Bile salts – emulsify fats Hemorrhoids – enlarged or inflamed rectal or hemorrhoidal, veins that supply the anal canal; may Bilirubin – bile pigment that results from the cause pain, itching, bleeding around anus breakdown of hemoglobin Functions of Large Intestine Anatomy of Pancreas 1. Feces production 1. Head – near the midline of the body 2. Water absorption 2. Tail – extends to the left M A V M. Feces – converted chyme Lipase – secreted by pancreas; digests lipid molecules Defecation – elimination of feces from the colon Micelles – aggregated bile salts around small droplets of digested lipids Mass movements – strong contractions in the large parts of the colon; propel the colon contents a considerable Chylomicrons – packaged lipid-protein complexes distance towards the anys (lipoproteins) Defecation reflex – local (weak contractions) + Chyle – lymph containing late amounts of absorbed parasympathetic (strong contractions) reflexes lipid DIGESTION, ABSORPTION, AND TRANSPORT Proteins Digestion – breakdown of food to molecules tha are § Chains of amino acids small enough to be absorbed into the circulation a. Mechanical digestion – breaks large good Pepsin – enzyme secreted by stomach that breaks down particles into smaller ones proteins b. Chemical digestion – breaking of covalent chemical bonds in organic molecules by Polypeptides – shorter amino acid chains digestive enzymes Trypsin, Chymotrypsin, Carboxypeptidase – enzymes Absorption – begin in stomach; lipid-soluble molecules produced by pancreas that continue the digestive diffuse through the stomach epithelium into the process circulation Peptidases – small peptides Transport – requires carrier molecules and includes facilitated diffusion, cotransport, and active transport Water and Minerals § Approximately 9 L of water enters the digestive Carbohydrates tract § Consist primarily of starches, cellulose, sucrose § Approximately 2 L from food & drink & (table sugar), small amounts of fructose (fruit remaining 7 liters is from digestive secretions sugar), and lactose (milk sugar) § Polysaccharides – large carbohydrates that consist of many sugars linked by chemical bonds Salivary amylase – begins the digestion of carbohydrates in the mouth Pancreatic amylase – continues digestion of carbohydrates Disaccharides – two sugars; broken down polysaccharide Disaccharidase – group of enzymes that break the disaccharides to monosaccharides Monosaccharides – single sugars; glucose, galactose, and fructose Lipids § Molecules which are insoluble or slightly soluble in water Triglycerides – most common type of lipid; 3 fatty acids bound to glycerol Saturated – fatty acids have only single bonds Unsaturated – fatty acids have one or more double bonds Emulsification – large lipid droplets are transformed into much smaller droplets M A V M.