Anatomy and Physiology of the Digestive System PDF

Anatomy and Physiology DIGESTIVE SYSTEM DIGESTIVE SYSTEM ORAL CAVITY PROPER - lies within the teeth and the gums LABIAL FRENULUM...

Anatomy and Physiology DIGESTIVE SYSTEM DIGESTIVE SYSTEM ORAL CAVITY PROPER - lies within the teeth and the gums LABIAL FRENULUM - median fold that joins the internal aspect of each lip to the gum B. HARD PALATE - forms the anterior roof of the mouth - underlain by palatine bones and the palatine process of the maxillae - forms a rigid surface against which the tongue forces food during chewing - has a slightly corrugated mucosa on both sides which helps create friction C. SOFT PALATE - forms the posterior roof of the mouth - mobile fold formed mostly of skeletal muscle that rises reflexively to close off the nasopharynx when swallowing FAUCES - formed by the palatoglossal and palatopharyngeal arches - contains the palatine tonsils FUNCTIONS UVULA 1. breakdown of ingested food - projecting downward from the free edge 2. absorption of nutrients in the blood D. TONGUE 3. production of cellular energy (ATP) - grips and repositions food during chewing 4. constructive and degradative cellular activities - mixes food with saliva to form a bolus (lump) initiating STRUCTURES OF THE DIGESTIVE SYSTEM swallowing by pushing it into the pharynx ALIMENTARY CANAL E. SALIVARY GLANDS - gastrointestinal tract - produces saliva which aids to moisturize the mouth - continuous muscular tube that winds through the - involved in the process of cleansing, food dissolution, body from the mouth to the anus moistening, and initiating breakdown of starchy foods - digests food or break it down into smaller fragments SALIVA - absorbs digestive fragments through its lining into the - provides protection against microorganisms through blood antibodies, bactericidal enzymes, and defensins ORAL CAVITY OR MOUTH SEROUS CELLS - primary site for mechanical digestion through chewing - produces watery saliva with enzymes and ions - initiates chemical digestion through the release of mucous CELLS saliva containing enzymes that breaks down food - produces stringy mucus - digestive processes includes mastication (chewing) F. TEETH and deglutition (swallowing) - gum-covered sockets that aids in food processing MASTICATION through tearing and grinding during mastication, - voluntary and reflexive actions of the cheeks, lips, breaking it into smaller fragments tongue, and teeth to breakdown food ENAMEL DEGLUTITION - hard mineralized substance covering the crown - voluntary buccal and involuntary pharyngeal- - hardest material in the body esophageal phases DENTIN A. LIPS (LABIA) AND CHEEKS - protein-rich material underlying the enamel and - help keep food between the teeth when chewing providing resilience during biting - protects the anterior opening and forms the lateral PULP CAVITY - contains soft tissues, blood vessels, and nerves walls respectively ORAL VESTIBULE supplying nutrients and sensation - recess bounded externally by the lips and cheeks and PHARYNX internally by the gums and teeth - consists of oropharynx and laryngopharynx which are common passageways for food, fluids, and air Anatomy and Physiology DIGESTIVE SYSTEM - facilitates seamless transfer of swallowed substances - secretes gastrin into the bloodstream to the esophagus, initiating the swallowing reflex - mixes saliva, food, and gastric juices to form chyme A. OSOPHARYNX CHYME - posterior to the oral cavity - semifluid mixture made of partially digested food and B. LARYNGOPHARYNX digestive juices - located below the oropharynx and connected to the esophagus C. NASOPHARYNX - not a part of the digestive system ESOPHAGUS - muscular tube that carries food and collapses when not involved in food propulsion - main passageway particularly for food - conducts food by peristalsis PERISTALSIS - food movement by alternating rhythmic contractions of the muscle layers ALIMENTARY CANAL LAYERS OF THE ESOPHAGUS A. MUCOSA - innermost layer REGIONS OF THE STOMACH - moist membrane A. CARDIAL OR CARDIA REGION B. SUBMUCOSA - surround the cardiac orifice through which food enters - beneath the mucosa the stomach from the esophagus - soft connective tissue with blood vessels, nerve - contains the cardio esophageal sphincter endings, and lymphatics B. FUNDUS C. MUSCULARIS EXTERNA - dome-shaped part - smooth muscle - tucked beneath the diaphragm. - inner circular layer - bulges superolateral to the cardia - outer longitudinal layer C. BODY D. SEROSA - midportion of the stomach - outermost layer or the visceral peritoneum - inferior to the fundus - layer of serous fluid-producing cells D. PYLORUS - funnel-shaped terminal end - demarcates the end of the stomach and the beginning of the small intestine PYLORIC SPHINCTER - controls stomach emptying by regulating the entry of food from the stomach into the duodenum E. LESSER CURVATURE - concave medial surface on the external region of the stomach F. GREATER CURVATURE - convex lateral surface on the external region of the stomach G. OMENTA STOMACH - help tether the stomach to other digestive organs and - J- shaped enlargement of the gastrointestinal tract the body wall - most distensible part of the GI tract which can LESSER OMENTUM accommodate a large quantity of food - runs from the liver to the lesser curvature of the - secretes gastric juice containing HCl, pepsin, intrinsic stomach, where it becomes continuous with the factor, and gastric lipase visceral peritoneum covering the stomach - serves as a storage tank and breakdown site for food before its release into the small intestine Anatomy and Physiology DIGESTIVE SYSTEM GREATER OMENTUM REGULATION OF GASTRIC SECRETION - drapes inferiorly from the greater curvature of the A. CEPHALIC PHASE stomach to cover the coils of the small intestine - initiated by sensory stimuli such as sight, smell, taste, - protects other organs from inflamed or diseased or even the thought of food organs - stimulation of gastric glands to release gastric juices SPECIALIZED MUCOSA OF THE STOMACH like hydrochloric acid and pepsinogen in preparation - comprises of a layer of surface mucous cells or simple for food that is anticipated but not yet ingested columnar epithelial cells B. GASTRIC PHASE A. GASTRIC PITS - initiated by the arrival of food in the stomach - indentations in the stomach which denote entrances - ingested food stimulates gastric activity through to the tubular shaped gastric glands formed by folded stretching the stomach and increasing the pH level of mucosa its contents B. GASTRIC GLAND - stimulates the parietal cells to release hydrochloric - responsible for the synthesis and secretion of gastric acid that lowers pH levels, breaking apart food juice GASTRIC SECRETION - contains cells that secrete their products into the - stimulated by three chemicals namely, acetylcholine stomach lumen (ACh), histamine, and gastrin MUCOUS NECK CELLS C. INTESTINAL PHASE - produce a sticky alkaline mucus, forming a protective - initiated by the entry of partially digested food barrier that prevents digestion of the stomach wall (chyme) into the small intestine CHIEF CELLS - as the chyme stimulates the secretion of gastrin, it - produces pepsin or protein-digesting enzymes stimulates the stomach by stretching the duodenum PARIETAL CELLS and enhancing the gastric function via the vagus nerve - secretes hydrochloric acid which aids in the digestion ENTEROGASTRIC REFLEX of food, absorption of minerals, and control of harmful - duodenum sending inhibitory signals to the stomach bacteria through the enteric nervous system ENTEROENDOCHRINE CELLS GASTRIC MOTILITY - secretes gastrin, a peptide hormone that stimulates A. RECEPTIVE RELAXATION secretion of gastric acid - occurs in anticipation of and in response to food C. MUCOSAL BARRIER moving through the esophagus and into the stomach - protects the stomach from highly acidic gastric juice B. GASTRIC ACCOMODATION and self-digestion - visceral smooth muscle exhibiting the stress-relaxation - thick coating of bicarbonate-rich mucus buildup on the response stretching without greatly increasing its stomach wall tension and contracting impulsively C. GASTRIC CONRACTILE ACTIVITY - peristalsis beginning near the gastroesophageal sphincter where it produces gentle rippling movements of the thin stomach wall - back-and-forth pumping action breaking up solids effectively in gastric contents GASTRIC EMPTYING - receptors in the stomach walls responds to the chyme entering the duodenum causing it to stretch, initiating the enterogastric reflex and the enterogastrone (hormonal) mechanisms that inhibits acid and pepsin secretion - inhibiting of gastric secretion to prevent further duodenal filling by reducing the force of pyloric contractions SMALL INTESTINES - major digestive organ which is also the longest part of the alimentary canal - digestion is completed within its twisted passageways where virtually all absorption occurs Anatomy and Physiology DIGESTIVE SYSTEM - primary site of nutrient absorption, as well as the STRUCTURES INVOLVED IN digestion of proteins, fats, and carbohydrates ABSORPTION OF NUTRIENTS INTESTINAL JUICE A. ABSORPTIVE CELLS - slightly alkaline juice secreted by the intestinal glands - responsible for absorbing nutrients and electrolytes stimulated by the hypertonic or acidic chyme B. VILLI A. DUODENUM - transports glucose and amino acids into the blood - attached to the stomach and mixes food with enzymes C. LACTEALS and bile to digest it - specialized lymphatic capillaries that absorb large B. JEJUNUM molecules of fats and lipids from the small intestine - about 2.5 m (8 ft) long, extends from the duodenum LARGE INTESTINES to the ileum - frames the small intestine on three sides extending C. ILEUM from the ileocecal valve to the anus - approximately 3.6 m (12 ft) in length, joins the large - absorbs at temporarily stores most of the remaining intestine at the ileocecal valve water from indigestible food residues, then eliminates - where Peyer’s patches are most common them from the body as semisolid feces PEYER’S PATCHES A. CECUM D. small clusters of lymphatic tissue found in the wall of - first part of the large intestine that is saclike which lies the small intestine below the ileocecal valve in the right iliac fossa E. contains huge numbers of bacteria as it prevents it BACTERIAL FLORA from entering the bloodstream - received by the cecum from the small intestine which STRUCTURAL MODIFICATIONS forms a diverse bacterial flora of the large intestine A. CIRCULAR FOLDS which colonizes the colon - deep permanent folds of the mucosa and submucosa - synthesizes B complex vitamins and some of the - forces chyme to spiral through the lumen, slowing its vitamin K the liver needs to produce clotting proteins movement and allowing time for full nutrient - metabolize some host-derived molecules (mucin, absorption heparin, and hyaluronic acid) B. VILLI - ferments some indigestible carbohydrates (cellulose, - fingerlike projections of the mucosa that greatly xyan, etc.) increases the surface area of the small intestine for B. APPENDIX food absorption - contains masses of lymphoid tissue which plays an C. MICROVILLI important role in body immunity - small projections of the plasma membrane found on - has a twisted structure to provide an ideal location for the absorptive cells that helps increase the surface enteric bacteria to accumulate and multiply area in the intestine C. COLON - maximizes nutrient absorption, ensuring the utilization - retroperitoneal organ with several distinct regions of carbohydrates, proteins, and fats for energy and namely the ascending colon, right colic (hepatic ) other physiological processes flexure, transverse colon , left colic (hepatic ) flexure, descending colon, and sigmoid colon D. RECTUM - runs posteroinferiorly just in front of the sacrum ANAL CANAL - terminal part of the large intestine - has an involuntary internal anal sphincter comprising of smooth muscles - has a voluntary external anal sphincter which is composed of skeletal muscles ACCESSORY DIGESTIVE ORGANS - produces a variety of secretions that help break down foodstuffs LIVER - largest gland in the body that is rich in blood - has four primary lobes namely the right lobe which is the largest and most visible, left lobe which is smaller, Anatomy and Physiology DIGESTIVE SYSTEM caudate, and quadrate lobes which can be seen in the A. CARBOHYDRATE DIGESTION inferior part of the liver - carbohydrate monomers or monosaccharides are SUBSTANCES IN THE LIVER absorbed A. BILE 1. Starchy foods and digestible carbohydrates are broken - produced by stored in the gallbladder down by the salivary amylase. - a yellow-green, alkaline solution composed of bile 2. Pancreatic amylase in the small intestines then acts on salts, bile pigments, cholesterol, triglycerides, the broken-down food. phospholipids, and various electrolytes 3. About 10 minutes after entering the small intestines, B. BILE SALTS starch is entirely converted to various - emulsifies fats, breaking them down into smaller oligosaccharides, mostly maltose. droplets in the watery intestinal contents 4. Internal brush border enzymes like dextrinase and - solubilizes cholesterol in bile from dietary sources glucoamylase, maltase, sucrase, and lactase then C. BILIRUBIN further digests these products to monosaccharides. - chief pigment of bile 5. All monosaccharides leave the epithelial cells via - absorbed by liver cells which is excreted into bile an facilitated diffusion metabolized in the small intestine by resident bacteria 6. It will then enter the capillary blood in the villi, which D. RECYCLING MECHANISM are transported to the liver via the hepatic portal vein. - where bile salts undergo through enterohepatic MONOSACCHARIDES circulation - glucose, fructose, and galactose are common in ENTEROHEPATIC CIRCULATION human diet - recycling mechanism that conserves bile salts SALIVARY AMYLASE GALLBLADDER - splits starch into oligosaccharides (two eight-linked - green thin-walled muscular sac resembling the size of glucose molecules) a kiwi fruit B. PROTEIN DIGESTION - stores and concentrates bile that is not immediately 1. Pancreatic proteases and brush border enzymes of required for digestion mucosal cells digest protein and protein fragments to PANCREAS amino acids. - produces pancreatic juice containing enzymes that 2. Amino acids are then absorbed into absorptive cells break down all food categories via active transport, then moves to the opposite side. PANCREATIC JUICE 3. The amino acids will then leave the villus epithelial cell - creates an optimal environment for intestinal and by facilitated diffusion and enter the capillary via pancreatic enzymes preventing self-digestion of intercellular clefts. pancreas About 10 minutes after entering the small intestines - composed of water and electrolytes which has a high C. FAT/LIPID DIGESTION pH crucial for neutralizing acidic chyme entering the 1. Bile salts in the duodenum emulsify large fat globules duodenum by physically breaking them into smaller fat droplets. 2. Pancreatic enzyme lipase yields free fatty acids and monoglycerides to be able to digest fat. 3. These then associate with bile salts to form micelles which “ferry” them to the intestinal mucosa. 4. Fatty acids and monoglycerides leave micelles and defuse to the epithelial cells where they recombine and package with other fatty substances and proteins, forming chylomicrons. 5. Chylomicrons are then extruded from the epithelial cells by exocytosis. They then enter lacteals and are carried away from the intestine in lymph. D. NUCLEIC ACID DIGESTION 1. Sodium-potassium pump stores energy that drives DIGESTION glucose and galactose uptake by creating a steep - catabolic process that breaks down large food concentration gradient for sodium entry into intestinal molecules to monomers small enough to be absorbed cells. in the GI tract lining Anatomy and Physiology DIGESTIVE SYSTEM 2. As sodium moves across the membrane through a 1. ACUTE DIARRHEA membrane cotransporter protein, which drives - most common type of loose and watery diarrhea that glucose against its concentration gradient into the lasts one to two days cells. 2. PERSISTENT DIARRHEA - lasts about two to four weeks 3. Fructose then enters the cell via facilitated diffusion. 3. CHRONIC DIARRHEA 4. All three monosaccharides exit across the basolateral - may last more than four weeks membrane via facilitated diffusion on GLUT2 sugar - comes and goes regularly over a long period of time transporter. SIGNS AND SYMPTOMS ABSORPTION NAD TRANSPORT 1. abdominal pain and cramping A. CARBOHYDRATE ABSORPTION 2. strong urgent need to poop 1. Glucose and galactose liberated by breakdown of 3. nausea and vomiting starch and disaccharides, are shuttled by secondary 4. loose watery stools active transport along with sodium into the epithelial 5. fever and chills cells. 6. bloating 2. They then move out of the epithelial cells via TREATMENT facilitated diffusion and passed on into the capillaries 1. replace lost fluids and electrolytes to prevent via intercellular clefts. dehydration 3. In contrast, fructose moves entirely via facilitated 2. drinking of water, fruit juices, sports drinks, diffusion to enter and exit the cells. decaffeinated sodas, and salty broths for adults B. PROTEIN ABSORPTION 3. oral rehydration solutions for children 1. Protein digestion allows several types of carriers to transport the different amino acids. 2. These carriers are coupled to the active transport of sodium. 3. Short chains of two or three amino acids like dipeptides and tripeptides are actively absorbed by Hydrogen dependent cotransport. 4. They are then digested to their respective amino acids within the epithelial cells. 5. The amino acids will then enter the capillary blood via B. CONSTIPATION diffusion. - problem with passing stool causing fewer than three C. FAT/LIPID ABSORPTION bowel movements a week 1. As water-insoluble products of fat digestion are - may cause death when chronic liberated by lipase activity, they quickly become IDIOPATHIC MEGACOLON associated with bile salts and lecithin. - bowel wall disruption and subsequent redness and 2. Upon reaching the epithelial cells inflammation of abdominal lining D. NUCLEIC ABSORPTION - may cause death due to bowel perforation and 1. Special carriers in the epithelium of the villi will obstruction associated with constipation actively transport the breakdown products of nucleic SIGNS AND SYMPTOMS acid digestion. 1. fewer than three stools a week 2. hard, dry, or lumpy stools 2. Pentose sugars, nitrogenous bases, and phosphate ions will then enter the blood. 3. straining or pain when passing stools 4. feeling that not all stool has passed, or the rectum is DISEASES OF THE DIGESTIVE SYSTEM A. DIARRHEA blocked - loose watery stools lasting three or more times a day TREATMENT 1. diet and lifestyle changes - eventually leads to dehydration and malabsorption 2. prescription medications - affects the stomach, small intestines, and colon 3. laxatives, enemas, and suppositories - second leading cause of death in children under five 4. surgery if necessary years old - caused by bacteria and parasites in contaminated food or water, norovirus or rotavirus, food intolerances, antibiotics, cancer drugs, and antacids with magnesium Anatomy and Physiology DIGESTIVE SYSTEM C. CELIAC DISEASE - triggered by an immune reaction in the small intestine E. GASTROESOPHAGEAL REFLUX DISEASE (GERD) linings (villi) due to excessive gluten consumption, - chronic gastrointestinal disorder characterized by the preventing the absorption of nutrients regurgitation of gastric contents into the esophagus GLUTEN - develops when the lower esophageal sphincter - protein found in foods containing wheat, barley, or rye becomes weak or relaxes when it shouldn’t SIGNS AND SYMPTOMS SIGNS AND SYMPTOMS 1. diarrhea 1. heartburn 2. weight loss 2. regurgitation or belching of food or sour liquid 3. constipation 3. developing a sour taste in mouth 4. abdominal pain 4. upper abdominal or chest pain 5. nausea and vomiting 5. dysphagia or trouble swallowing 6. swollen belly and foul-smelling stools in children 6. lump sensation in the throat TREATMENT 7. excessive salivating 1. strict, lifelong gluten-free diet 8. wheezing and chronic coughing 2. vitamin and mineral supplements 9. difficulty breathing 3. follow-up care TREATMENT 1. lifestyle changes 2. over-the-counter prescription medications 3. surgery if necessary F. IRRITABLE BOWEL SYNDROME (IBS) - poorly coordinated signals between the brain and intestines causing the body to overreact and hinder the digestive process - changes the contraction of bowel muscles, making the gut more sensitive SIGNS AND SYMPTOMS 1. abdominal pain, cramping, or bloating D. GALLSTONES 2. mixed bowel habits (diarrhea and constipation) - forms when bile contains too much cholesterol and 3. mucus in bowel movements bilirubin creating pebble-like pieces of material that 4. looser and/or more frequent stools forms in the gallbladder TREATMENT SIGNS AND SYMPTOMS 1. manage stress 1. abdominal pain lasting for several hours 2. dietary and lifestyle changes 2. nausea or vomiting 3. prescription medications 3. fever 4. jaundice 5. tea-colored urine 6. light-colored stools 7. shoulder pain 8. back pain between shoulder blades 9. sudden and intensifying pain TREATMENT 1. surgery to remove gallbladder Anatomy and Physiology DIGESTIVE SYSTEM G. CROHN'S DISEASE - lifelong form of inflammatory bowel disease which I. AMOEBIASIS mainly irritates the small and large intestines - caused by a parasite called Entamoeba histolytica - may be influenced by genes, smoking, abnormal infecting through contaminated food or water, soil, or balance of gut bacteria, or problems with the immune fertilizer system - can occasionally lead to symptoms such as diarrhea, SIGNS AND SYMPTOMS nausea, and weight loss 1. abdominal pain, cramping, or bloating SIGNS AND SYMPTOMS 2. inflammation of eyes and joint 1. loose stools 3. skin ulcers and sores 2. abdominal cramping 4. liver and bile ducts inflammation 3. stomach pain 5. anemia TREATMENT 6. stomatitis or oral inflammation 1. antibiotic treatment for asymptomatic cases 7. ulcers in digestive tract 2. 10-day course of metronidazole followed by 8. rectal bleeding antibiotics TREATMENT 3. surgery when necessary 1. therapies to reduce signs and symptoms COMMON NURSING INTERVENTIONS 2. medicine to reduce inflammation of digestive system A. MANAGING DIARRHEA AND RESTORING NORMAL 3. surgery FUNCTION - evaluate the patient’s pattern of defecation to promote immediate treatment - asses abdominal pain, cramping, hyperactive bowel sounds, frequency, urgency, and loose stools for the collection of stool culture B. PREVENTING DEHYDRATION - assess client's skin turgor and mucous membranes to assess for signs of dehydration caused by interstitial H. SMALL INTESTINAL BACTERIAL OVERGROWTH fluid loss (SIBO) C. PROMOTING ADEQUATE NUTRITIONAL BALANCE - due to an abnormal increase in the overall bacterial - provide clients their parenteral fluids, as ordered to population in the small intestine ensure adequate fluid and electrolyte levels SIGNS AND SYMPTOMS D. INITIATING PATIENT EDUCATION AND HEALTH 1. abdominal pain and nausea TEACHINGS 2. loss of appetite - it is important for nurses to educate their clients 3. bloating and gas - regarding perianal care, as well as a patients' 4. diarrhea or constipation education plays a vital role in improving and 5. food sensitivities preventing further complications 6. weight loss due to malabsorption E. ADMINISTERING MEDICATIONS AND PROVIDING TREATMENT PHARMACOLOGIC SUPPORT 1. antibiotics - carefully assess each patient considering the severity 2. probiotics of symptoms, the presence of complications and the 3. fecal microbiota transplants individual's overall health status F. ASSESING AND MONITORING FOR POSSIBLE COMPLICATIONS - assess the clients for any signs of dehydration including electrolyte level and assessing the renal function - monitoring a client's neurological status is also a crucial part since infections may lead to complications such as seizures or encephalopathy - monitoring organ dysfunction is necessary to identify any signs of organ involvement or complications Anatomy and Physiology DIGESTIVE SYSTEM PHYSIOLOGICAL PROCESSES INVOLVED IN THE DIGESTIVE SYSTSEM A. INGESTION - process begins with the intake of food through the mouth or oral cavity B. MASTICATION OR CHEWING - teeth break down food into smaller particles, increasing the surface area for enzymatic action C. SALIVATION - salivary glands release saliva containing enzymes like amylase that start the digestion of carbohydrates D. DEGLUTITION OR SWALLOWING - the tongue pushes the chewed food to the back of the throat, initiating the swallowing reflex E. PERISTALSIS - food travels down the esophagus through a series of muscular contractions F. PROTEIN DIGESTION - food enters the stomach, where gastric juices like hydrochloric acid and pepsin aid in the digestion of proteins G. CHURNING AND MIXING - stomach muscles contract and relax, churning and mixing the food with gastric juices to form chyme H. SECRETION OF BILE AND PANCREATIC ENZYMES - bile and enzymes are secreted into the small intestine to emulsify fats and break down nutrients I. ABSORPTION - the small intestine absorbs nutrients such as amino acids, fatty acids, and glucose through the intestinal walls into the bloodstream J. LARGE INTESTINE STORAGE - remaining indigestible material like water and fiber moves to the large intestine for water absorption and formation of feces K. FORMATION AND STORAGE OF FECES - the colon compacts the remaining material into feces and stores it until it is ready for elimination L. DEFECATION - fecal material is stored in the rectum until it is ready to be expelled from the body thru the anus