Module 13 Digestive System PDF

NURSING ANAPHY / PROF. ALARZAR DIGESTIVE SYSTEM Mass movement Contractions that ALIMENTARY CA...

NURSING ANAPHY / PROF. ALARZAR DIGESTIVE SYSTEM Mass movement Contractions that ALIMENTARY CANAL move material in the Mouth distal parts of the Pharynx large intestine to the Esophagus anus Stomach ○ Mixing Small intestine Movement of food back and Large intestine forth in the digestive tract without forward movement Mixing waves ACCESSORY ORGAN ○ Gentle Teeth contractions Tongue that churn the Gallbladder food with Salivary glands gastric Liver secretions Pancreas Segmental contractions ○ Mix food FUNCTIONS OF THE DIGESTIVE SYSTEM particles with Ingestion and mastication digestive ○ Ingestion secretions in Intake of solid or liquid food the small into the stomach intestines ○ Mastication Process by which the teeth chew food in the mouth to begin digestion (mechanical breakdown Propulsion and mixing ○ Propulsion Movement of food from one end of the digestive tract to Secretions the other ○ Added to liquify, lubricate, buffer and Swallowing digest food as it moves through the Deglutition GIT Moves liquid/ soft ○ Mucus mass of food called a Lubricates food bolus from oral cavity to esophagus ○ Water Peristalsis Liquefies the food making it Propels materials easier to digest and absorb through most of the digestive tract BSN CHAVEZ, K. | 11/1/24 1  ANAPHY | DIGESTIVE SYSTEM ○ Enzymes Mechanical breakdown Breaks down large food ○ Preparing for digestion by enzymes, molecules into smaller includes chewing, mixing with saliva, churning the stomach, and molecules that can be segmentation absorbed by the intestinal Digestion wall ○ Enzymatic degradation of food molecules Absorption ○ Passage of end-products from lumen to blood or lymph HISTOLOGY Tunics Digestion ○ Major functions Secretion of mucus ○ Breakdown of large organic Absorption of end products of molecules into their component parts digestion Consists of mechanical Protection against infectious digestion (mastication and disease mixing) and chemical ○ Mucus secretions digestion (enzymes) Protect digestive organs from Absorption digesting themselves Ease food along the tract ○ Movement of molecules out of the ○ Stomach and small intestine mucosa digestive tract and into the blood or contains: into the lymphatic system Enzyme-secreting cells Elimination Hormone-secreting cells ○ Process by which the waste (making them endocrine and products of digestion are removed digestive organ) from the body Feces HISTOLOGY OF THE DIGESTIVE TRACT Semisolid waste Has four tunics products stored in the ○ Mucosa distal large intestines Innermost layer that lines the and eliminated by the lumen of the alimentary canal process of defecation Consists of mucous epithelium. Lamina propria, and muscularis mucosae MAJOR PROCESSES ○ Submucosa Connective tissue layer Ingestion containing the submucosal ○ Taking food into the digestive tract plexus (part of the enteric Propulsion plexus), blood vessels, and ○ Moving food through the canal, small glands includes swallowing and peristalsis ○ Muscularis Consists of an inner layer of circular smooth muscle and an outer layer of longitudinal smooth muscle BSN CHAVEZ, K. | 11/1/24 2  ANAPHY | DIGESTIVE SYSTEM The myenteric plexus is Mesentery connecting between the two muscle greater curvature of the layers stomach to transverse colon ○ Serosa / Adventitia and posterior body wall Forms the outermost layer of the digestive tract BLOOD FLOW Arterial flow NERVOUS REGULATION OF THE DIGESTIVE Venous flow SYSTEM Hepatic portal circulation Enteric nervous system Enteric nervous system ○ Sensory neurons ○ In-house nerve supply of the Detects chemical changes in alimentary canal that regulates the chemical composition of digestive system activity the digestive tract Submucosal nerve plexus ○ Motor neurons Myenteric nerve plexus Stimulate or inhibit smooth Arterial blood flow muscle contraction and glandular secretion ○ Interneurons Connect sensory to motor neurons ○ Nervous regulation involves local reflexes in the ENS and CNS reflexes PERITONEUM Most extensive membrane in the abdominopelvic cavity Visceral peritoneum ○ Covers the external surface of digestive organs Parietal peritoneum ○ Lines the body wall Peritoneal cavity ○ Potential space containing fluid secreted by serous membranes which allows digestive organs to glide easily across one another Mesentery ○ Double layer of peritoneum Provides routes for blood vessels, lymph and nerves Holds organ in place Store fat ○ Lesser omentum Mesentery connecting lesser curvature of stomach to liver and diaphragm ○ Greater omentum BSN CHAVEZ, K. | 11/1/24 3  ANAPHY | DIGESTIVE SYSTEM Venous blood flow Contains accessory glands (salivary glands) and accessory organs (teeth and tongue) which begin the digestive process Lips and cheeks ○ Involved in facial expression, mastication, and speech Palate ○ Forms the roof of the mouth ○ Hard palate Assists the tongue in chewing ○ Soft palate Hepatic portal circulation Mobile fold formed mostly of skeletal muscle Projecting from the soft palate is the uvula ○ Closes off the nasopharynx during swallowing Tongue ○ Occupies the floor of the mouth and fills the oral cavity when mouth is closed ○ Functions: Gripping an repositong food during chewing DIGESTIVE TRACT ANATOMY Mixing food with saliva and forming the bolus Initiation of swallowing and MOUTH / ORAL CAVITY speech Bounded by lips anteriorly, cheeks laterally, ○ Frenulum secures the tongue to the palate superiorly, and tongue inferiorly floor of the mouth Continues with the oropharynx Teeth Lined with stratified squamous epithelium ○ Tear and grind food and slightly keratinized ○ Babies are born with 20 deciduous ○ Withstands friction teeth ○ Prevents abrasion while eating Erupt between about 6 Divided into 2 regions: months and 24 months of ○ Vestibule age Space between the lips of Deciduous teeth are replaced cheeks and the alveolar by 32 permanent teeth processes that contains the Replacement starts at about teeth 5 years and the process is ○ Oral cavity proper complete by about 11 years Lies medial to the alveolar processes BSN CHAVEZ, K. | 11/1/24 4  ANAPHY | DIGESTIVE SYSTEM ○ Types of teeth: Incisors Canines Premolars Molars ○ A tooth consists of: Crown Exposed part of the tooth above the gingiva Dentin is covered by enamel ○ Enamel - acellular material composed of calcium salts and hydroxyapatite crystals (the hardest substance in the body) Root Portion of the embedded in the jawbone Composed of dentin In the dentin of the root is the pulp cavity Pulp cavity is filled with pulp, blood vessels, and nerves SALIVARY GLANDS Periodontal ligaments hold Produce and secrete saliva teeth in the alveoli Functions: ○ Cleanses the mouth ○ Moisten and dissolve food chemicals ○ Aids in bolus formation ○ Contains enzymes that break down starch Produce serous and mucous secretions Has 3 pairs: ○ Parotid glands ○ Submandibular glands ○ Sublingual glands Saliva ○ 1L of saliva / day ○ Secreted from serous and mucous cells of salivary glands BSN CHAVEZ, K. | 11/1/24 5  ANAPHY | DIGESTIVE SYSTEM Serous Enzymes Ions Mucin Mucous Produces mucus ○ Composed of 97-99.5% water and slightly acidic solution containing Electrolytes Digestive enzyme Salivary amylase Proteins Mucin PHARYNX Lysozyme Defensins Food passes posteriorly into the oropharynx IgA Then passes to the laryngopharynx which Metabolic wastes is a common passageway for food, fluids, Urea and air Uric acid Control of salivation ○ Primarily controlled by the parasympathetic division of the autonomic nervous system ○ Salivary glands secretes serous, enzyme-rich saliva in response to: Ingested food which ESOPHAGUS stimulates chemoreceptors and pressoreceptors Muscular tube about 25 cm and collapsed The thought of food when not propelling food ○ Dry mouth is caused by strong Once food moves through the sympathetic stimulation that inhibits laryngopharynx, the epiglottis will close the salivation larynx and food will posteriorly move to the esophagus Gastroesophageal sphincter (cardiac sphincter) surrounded by circular smooth muscle that keeps it closed when food is not being swallowed ○ Mucous cells at the sides will help protect the tube from reflux of stomach acid BSN CHAVEZ, K. | 11/1/24 6  ANAPHY | DIGESTIVE SYSTEM Swallowing ○ Pyloric orifice ○ During the voluntary phase of Opening to the duodenum swallowing Major regions: A bolus of food is moved by ○ Cardiac part the tongue from the oral ○ Fundus cavity to the pharynx Superior to the cardiac ○ During the pharyngeal phase opening Pharyngeal phase is a reflex ○ Body caused by the stimulation of Largest part of the stomach stretch receptors in the ○ Pyloric part pharynx Continuous with the The soft palate is elevated , duodenum through the closing off the nasopharynx pyloric sphincter The pharynx and larynx are Lateral sides consists of the greater and elevated lesser curvatures The pharyngeal muscles Wall of the stomach: move the bolus to the ○ External serosa esophagus ○ Muscle layer ○ During the esophageal phase Longitudinal It is a reflex initiated by the Circular stimulation of stretch Oblique receptors in the esophagus ○ Submucosa Peristalsis causes the food to ○ Simple columnar epithelium move to the stomach Has surface mucous cells ○ This produces alkaline mucous with bicarbonate that coats and protects the stomach lining ○ Rugae Folds in the stomach when the stomach is empty STOMACH Lies on the LUQ, hidden by the liver and diaphragm 50mL is empty but it can hold around 4L of food Temporary storage tank where chemical breakdown of proteins begins and food is Contains the 4 typical layers but muscularis converted from a bolus to chyme and mucosa are modified Openings: ○ Muscularis ○ Gastro-esophageal Allows food to be pummeled, Opening to the esophagus churned, mixed to physically BSN CHAVEZ, K. | 11/1/24 7  ANAPHY | DIGESTIVE SYSTEM break it down into smaller Kills microorganisms fragments and activates the ○ Mucosa enzyme, pepsin Composed of mucous cells Pepsin that produce a cloudy, Inactive form is called protective layer consisting of pepsinogen insoluble mucus that traps Digest proteins bicarbonate-rich fluid Mucus beneath it Forms a thick layer It is also dotted with gastric pits that allows which lubricates the gastric glands to secrete the gastric juice stomach walls and ○ Has four secretory cells: protects them from Mucous neck the damaging effect Secretes acid mucus of the acidic chyme Parietal cells and pepsin Secretes HCl and Irritation of the intrinsic factor stomach causes more Chief cells secretion of mucus Produces pepsinogen Intrinsic factor ○ Activated by Necessary for vitamin HCl in the B12 absorption stomach and Gastrin and histamine by itself Regulate stomach through secretions positive ○ A proton pump (H+-K+ exchange mechanism pump) moves H+ out of parietal cells Endocrine cells HCl production Produce regulatory hormones ○ Gastrin ○ Histamine ○ Endorphins ○ Serotonin ○ Cholecystokini n ○ Somatostatin Secretions in the stomach ○ Chyme When food is mixed with stomach secretions to become a semifluid mixture ○ Gastric juices HCl BSN CHAVEZ, K. | 11/1/24 8  ANAPHY | DIGESTIVE SYSTEM Gastrointestinal phase (slow down) Acidic chyme, which enters the duodenum and stimulates neuronal reflexes and the secretion of hormones (secretin, cholecystokinin) that inhibit gastric secretions Regulation of stomach secretions Gastric motility ○ Has 3 phases ○ Waves mix the stomach contents Cephalic phase (get with stomach secretions to form started) chyme Initiated by the sight, ○ Peristaltic waves move the chyme smell, taste, or into the duodenum thought of food Hunger contractions Nerve impulses from Vomiting the medulla stimulate Reverse peristalsis hydrochloric acid, pepsinogen, gastrin, SMALL INTESTINE and histamine secretion Body’s major digestive organ Gastric phase (go for it) Where digestion is completed and Initiated by distention absorption occurs of the stomach, which Runs from pyloric sphincter to ileocecal stimulates gastrin valve secretion and Chyme takes around 3-5 hours to pass activates CNS and through local reflexes that Has 3 divisions: promote secretion ○ Duodenum 10 inches long Bile and pancreatic ducts empties here BSN CHAVEZ, K. | 11/1/24 9  ANAPHY | DIGESTIVE SYSTEM Contains microvilli, Help protect the intestinal absorptive, goblet, granular, epithelium from bacteria and endocrine cells ○ Endocrine glands ○ Jejunum Produce regulatory 8 inches long hormones Absorption of Duodenal glands nutrients ○ The submucosa of the duodenum Has more goblet cell that contains mucous glands than duodenum Peyer's patches With brunner’s gland ○ Cluster of lymphatic nodules More vascular than ileum ○ Ileum 12 inches long Has the most goblet cells Contains peyer’s patches The small intestine has three modifications that increase its surface area about 600-fold ○ Circular fold Deep folds of the mucosa and submucosa ○ Villi Fingerlike extensions of the mucosa ○ Microvilli Tiny projections of absorptive mucosal cells’ plasma membranes. This forms a brush border Intestinal glands / crypts of Lieberkuhn ○ Epithelial cells that are located within tubular glands of mucosa The epithelium of the mucosa is made up of: ○ Absorptive cells Has microvilli Produce digestive enzymes Absorb digested food ○ Goblet cells Produce a protective mucus ○ Granular cells BSN CHAVEZ, K. | 11/1/24 10  ANAPHY | DIGESTIVE SYSTEM Histology ○ Enterocytes Simple columnar cells endowed with microvilli that secrete intestinal juice (mucus and carrier fluid) ○ Goblet cells Produce mucus ○ Enteroendocrine cells Source of secretin and cholecystokinin which inhibit gastric secretion ○ Paneth cells Releases defensins and lysozymes ○ Stem cells Divides to form daughter cells that become other cell types ○ Mucosa-associated lymphoid tissue includes Peyer’s patches that contains Ig-A secreting plasma cells for intestinal pathogen Secretion of the small intestine ○ Mucus protects against digestive enzymes and gastric acids ○ Digestive enzymes (disaccharidases and peptidases) are bound to the intestinal wall ○ Chemical or tactile irritation, vagal stimulation, and secretin stimulate intestinal secretion BSN CHAVEZ, K. | 11/1/24 11  ANAPHY | DIGESTIVE SYSTEM LIVER Produces bile for export into the duodenum Largest internal organ/ gland in the body, occupies most of the right hypochondriac and epigastric region ○ Weighs about 1.36kg Has 4 lobes ○ L & R lobe Separated by falciform ligament ○ Caudate & quadrate lobe Composed of sesame seed-sized functional units called liver lobules consisting of liver cells called hepatocytes Portal triads ○ Hepatic duct Conduct bile towards the duodenum ○ Hepatic artery Supplies oxygen-rich blood to the liver ○ Hepatic portal vein Carries venous blood with nutrients from digestive viscera ○ The hepatic cords are composed of columns of hepatocytes separated by the bile canaliculi Hepatocytes can: Secrete some 900mL of bile/day Process bloodborne nutrients Store fat soluble vitamins Detoxification ○ Sinusoids are enlarged spaces filled with blood and lined with endothelium and hepatic phagocytic cells BSN CHAVEZ, K. | 11/1/24 12  ANAPHY | DIGESTIVE SYSTEM Kupffer cells Enterohepatic circulation Hepatic macrophages found in liver sinusoids Functions: ○ Digestive and excretory functions ○ Store and process nutrients ○ Detoxifies harmful chemicals ○ Synthesizes new molecules ○ Secretes 700mL of bile each day PANCREAS Lies deep to the greater curvature of the stomach Head is encircled by the duodenum and the tail sits against spleen Only the pancreas produces enzymes that break down all categories of digestible foods Bile Has both endocrine and exocrine roles ○ Dilutes and neutralizes stomach acid ○ Exocrine and breakdown fats Secretes pancreatic juice Bile secretion and release which breaks down all categories of foodstuff A compound acinar gland Acinar cells within the acini produce digestives enzymes Exocrine secretions flow from the pancreas to the small intestine via a series of ducts, which merge to form the main pancreatic duct Bicarbonate ions neutralizes the acidic chyme that enters the small intestine from the stomach BSN CHAVEZ, K. | 11/1/24 13  ANAPHY | DIGESTIVE SYSTEM Neutralized pH component and relaxation of the prevents the stomach sphincters of the pancreatic duct and acid from damaging hepatopancreatic ampulla the duodenum ○ Parasympathetic stimulation ○ Endocrine increases and sympathetic Consists of pancreatic islets stimulation decreases secretion of or Islets of Langerhans enzymes Produces glucagon and insulin which are important for controlling blood levels of nutrients, such as glucose and amino acids Also secretes somatostatin, which regulates glucagon and insulin secretion Pancreatic enzymes includes ○ Proteases Protein-digesting enzymes Control of pancreatic secretion Major proteases: ○ Parasympathetic stimulation from Trypsin the vagus nerve causes the Chymotrypsin pancreas to release a secretion rich Carboxypeptidase in digestive enzymes. Conversely, Continues the protein sympathetic action potentials inhibit digestion that started in the pancreatic secretion stomach ○ Acidic chyme in the duodenum ○ Amylase stimulates secretin release. In turn, Continues the secretin stimulates the pancreas to polysaccharide digestion that release a watery secretion, rich in began in the oral cavity HCO3− into the duodenum ○ Lipases ○ Fatty acids and amino acids in the A lipid-digesting enzyme duodenum stimulate cholecystokinin ○ Nucleases release. In turn, cholecystokinin Degrade DNA and RNA to stimulates the pancreas to release their component nucleotides an enzyme-rich solution. These ○ These are produced in an inactive pancreatic enzymes digest the fatty form then activated in the duodenum acids and amino acids Regulation of bile secretion and release ○ Secretin stimulates the release of the aqueous component, which neutralizes acidic chyme ○ Cholecystokinin stimulates the secretion of the enzymatic BSN CHAVEZ, K. | 11/1/24 14  ANAPHY | DIGESTIVE SYSTEM GALLBLADDER Thin- walled muscular sac that appears green when filled with bile Stores bile that is not immediately needed for digestion and concentrates it by absorbing some of its water and ions Too much cholesterol or too few bile salts allow cholesterol to crystallize and forms gallstones LIVER, GALLBLADDER, PANCREAS, AND DUCT SYSTEM 1. The hepatic ducts converge and empty into the right and left hepatic ducts to transport bile out of the liver. The right and left hepatic ducts unite to form a single common hepatic duct 2. The gallbladder is a small sac on the inferior surface of the liver that stores concentrated bile. The cystic duct carrying bile from the gallbladder joins the common hepatic duct to form the common bile duct 3. The common bile duct joins the pancreatic duct 4. Together they open into the duodenum at the duodenal papilla. Together they open into the duodenum at the duodenal papilla 5. Pancreatic secretions may also enter the duodenum through an accessory pancreatic duct, which also empties into the duodenum BSN CHAVEZ, K. | 11/1/24 15  ANAPHY | DIGESTIVE SYSTEM REGULATION OF BILE SECRETION LARGE INTESTINE Parasympathetic stimulation through the Portion of the digestive tract extending from vagus nerve stimulates bile secretion by the the ileocecal junction to the anus liver. Vagus nerve stimulation causes the Consists of 4 parts gallbladder to contract, thereby releasing ○ Cecum bile into the duodenum Proximal end of the large Secretin from the duodenum also intestine where it joins the stimulates bile secretion and release small intestine at the Cholecystokinin, also produced by the ileocecal junction duodenum, is carried through the blood to This is where the appendix is the gallbladder. There cholecystokinin attached stimulates the gallbladder to contract and Contains many the sphincters to relax, which releases the lymphatic nodules stored bile into the duodenum that contributes to Bile salts increase bile secretion through a immune functions positive-feedback system ○ Colon ○ Over 90% of bile salts are Has 4 parts reabsorbed in the ileum and carried Ascending colon in the blood by the hepatic portal Transverse colon circulation Descending colon ○ Upon their return to the liver, the bile Sigmoid colon salts stimulate further bile secretion In the colon, the chyme is and are once again secreted into the converted to feces bile. This recycling process reduces Stores the feces until they the loss of bile salts in the feces. Bile are eliminated by defection secretion into the duodenum Crypts continues until the duodenum Numerous straight empties tubular glands in the mucosal lining of the colon The longitudinal smooth muscle layer of the colon does not completely envelop the intestinal wall but forms three bands called teniae coli ○ Rectum Straight muscular tube that begins at the termination of the sigmoid colon and ends at the anal canal ○ Anal canal Last 2-3cm of the digestive tract BSN CHAVEZ, K. | 11/1/24 16  ANAPHY | DIGESTIVE SYSTEM Begins at the inferior end of Has 3 unique features the rectum and ends at the ○ Teniae coli anus Three bands of longitudinal Internal anal sphincter smooth muscle in its Formed by the muscularis smooth muscle layer ○ Haustra of the anal canal Pocketlike sacs caused by which is even more the tone of the teniae coli thicker than rectum ○ Epiploic appendages External anal sphincter Fat-filled pouches of visceral Formed by the peritoneum skeletal muscle at the Secretions of the large intestine inferior end of the ○ Mucus protects the intestinal lining anal canal ○ The bacterial flora of the large Hemorrhoids intestine consist of: Enlarged or inflamed Bacteria surviving the small rectal, or intestine that enter the hemorrhoidal veins cecum that supply the anal Those entering via the anus canal ○ These bacteria: Causes pain, itching, Colonize the colon bleeding around the Ferment indigestible anus carbohydrates Can be treated by Release irritating acids and diet or medications gases (flatus) 18-24 hours are required for materials to Synthesize B complex pass through the large intestine vitamins and vit K ○ Movements of colon are more Constitute about 30% of the sluggish than the small intestine dry weight of the feces The mucosa is thicker with more number of Movement in the large intestine goblet cells to ease passage of feces and ○ Haustra mix the contents and moves protect the wall from irritation by acids and them slowly toward the anus gases released by bacteria ○ Mass movements are strong The bacterial flora functions by fermentation peristaltic contractions that occur (fatty acids can be absorbed from three or four times a day indigestible carbohydrates) and vitamin ○ Defecation is the elimination of feces synthesis especially B and K are Distension of rectal walls synthesized by bacteria caused by feces ○ Fermentation produces gases Stimulates (smelly dimethyl sulfide) around contraction of the 500mL each day rectal walls Relaxes the internal anal sphincter BSN CHAVEZ, K. | 11/1/24 17  ANAPHY | DIGESTIVE SYSTEM Reflex activity moves feces PHYSIOLOGY OF DIGESTION AND through the internal anal ABSORPTION sphincter Voluntary activity regulates movement through the external anal sphincter Carbohydrate digestion Protein digestion Fat digestion Nucleic acid digestion BSN CHAVEZ, K. | 11/1/24 18  ANAPHY | DIGESTIVE SYSTEM Water movement Lipoproteins ○ Water can move across the intestinal ○ Lipoproteins include chylomicrons, wall in either direction VLDL, LDL, and HDL ○ The movement depends on osmotic ○ LDL transports cholesterol to cells, pressures and HDL transports it from cells to ○ 99% of water entering intestine is the liver absorbed ○ LDL are taken into cells by receptor-mediated endocytosis, which is controlled by a negative-feedback mechanism BSN CHAVEZ, K. | 11/1/24 19  ANAPHY | DIGESTIVE SYSTEM EFFECTS OF AGING The mucous layer, the connective tissue, the muscles, and the secretions all tend to decrease as a person ages These changes make an older person more open to infections and toxic agents CONTRIBUTION OF DIGESTIVE SYSTEM TO OTHER BODY SYSTEMS BSN CHAVEZ, K. | 11/1/24 20