Digestive System - A&P Lecture Notes Guide Nursing PDF

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A&P Lecture Notes Guide Nursing...

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Digestive System Starts in the oral cavity, then into esophagus and goes to the stomach, small intestine and large intestine  Basic tube that runs from mouth to anus (30 feet in length)  Enzymatic activity break down food  Food never leaves this tube  Can be called the alimentary canal, gastrointestinal track or GI track Break down large molecules into smaller molecules so we can absorb them into the blood and carry it to the cells Pathway of Food  Enter through mouth or oral cavity and process it  esophagus  stomach  small intestine  large intestine  out through the anus Liver, Gallbladder, and Panaceas – you never see food come through these organs, they just help contribute to digesting the food at the level of the small intestine – we never want to see backup in the digestive system – this is why we have valves to prevent food from backing up Steps of Digestion  INGESTION – taking the food and placing it in the oral cavity (eating)  PROPULSION – moves the food along o Swallowing – occurs in oropharynx (voluntary until in the pharynx) o Peristalsis – wave like contraction of the musculature all along the digestive tube – digestive tubes have muscular layers (involuntary process) – occurs through entire digestive tube  MECHANICAL DIGESTION o Chewing – mouth o Churning – stomach o Segmentation – peristalsis in the small intestine  CHEMICAL DIGESTION – enzymatic digestion, breaking down the food material by enzymes  ABSORBATION – occurs in the small intestine o Passing nutrients into the blood supply – with this exchange there is leakage which is why we have lymphatic vessels by the small intestine to return the fluid to the blood supply  DEFECTION – excreting excess waste Whatever is non-digestible enters the large intestines – this is mostly water, which is removed in the large intestine – based on how fast it goes through determines how much water goes through Most of the digestive organs reside within the abdominopelvic cavity – very large, ventral cavity  We have a lining to this cavity as well as a covering on the organs  Parietal Peritoneum – lines the cavity / Visceral Peritoneum – covers the organs  Parietal and visceral peritoneum merge together to form mesenteries o Mesentery – strong layer that supports digestive organs – holding them in place  Given name due to location  Greater or lesser omentum – depends on thickness

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Stores fat (lipid cells/adipose tissue), helps to hold organs in place, contains blood and lymphatic vessels – compresses organs o Peritonitis – infection of the peritoneum – we have invited and introduced a bacteria to the peritoneal layers  This can be from a striking wound to the area, a perforating ulcer (gastric or duodenal ulcers need to be addressed)  Crimp the muscle behind the food to move it along and opens the muscles ahead to leave area open Design of Digestive System  Esophagus  Anus  4 basic tunics/layers that create the design of the digestive tube – INSIDE  OUTSIDE o Mucosa – has the lumen (opening) where the food goes through – has a smooth mucosa lining so the food passes through easily – has a lot of goblet cells that produce the mucosa  Epithelial Layer – layer that the food comes in contract with – simple columnar epithelium (usually what you see in the digestive system)  Lamina Propria Layer – has MALT, connective tissue layer, strong with connective fibers that allows the tube to be supportive  Muscularis Mucosa – smooth muscle, helps in moving the food along o Sub-Mucosa – white tissue, contains glands that produce mucous, glands and nerves, very well vascularized o Muscularis – muscular layer, allows for peristalsis, stomach has 3rd layer (oblique)  Circular Layer  Longitudinal Layer o Serosa – supportive, areolar connective tissue, seen through the entire length of the tube expect for in the esophagus instead there is adventitia (lighter type of covering) Anatomy of the Digestive System  Mouth (Oral Cavity) – where digestion starts o Boundaries  Lips (inferior/superior)  Cheeks (laterally) right and left  Contain muscles called buccinators – the press on the food to keep it contained in the oral cavity – we want to make sure when we bite down the food is in the location where the teeth come down  Tongue (inferior)  Contains taste buds (papillae) – main purpose is to manipulate the ball (bolus) of food to keep pushing it under the teeth to be chewed and also to mix the food around with salvia – the tongue is anchored by the frenulum so you cant swallow your tongue  Hard/soft palate (top/roof) o 3 Pairs of Salivary Glands – one on each side (right and left) – per pair 1 liter of salvia per day is produced – saliva has a pH 6.3-6.8, slightly acidic – mostly water, contains few electrolytes – Salivary Amylase or Ptyalin: enzyme saliva produces, starts to break down complex carbohydrates

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Parotid Gland – at the lower base of the ear Submandibular Gland – under the tongue Sublingual Gland – under the jaw

3 Areas  Crown – lines above the gum line, covered by enamel, the part that we can see – contains the top pulp cavity or the area with blood vessels and nerves – gains nourishment by diffusion  Neck – junction point between the crown and the gum (gingiva)  Root – contains all the pulp cavity, blood vessels and nerves – deep within the bone – very vascular  2 Sets of Teeth – incisors are in the front of the mouth (very sharp, to tear into the food when you bite it)  cuspid/canine (long teeth that help us tear meat)  premolars/bicuspid  molars (are flat to help us crush food)  wisdom teeth  Deciduous Teeth (baby teeth) – 20 teeth in total – found in young children – the front teeth form first and then come in as you get further into the back of the mouth  Permanent (secondary) Teeth – 32 teeth total – these erupt from underneath – primary dentition o Swallowing  Hard and Soft Palate – function is to rise when you are swallowing (deglutition) – this is to close off nasal cavity when you swallow  Soft Palate – extends into the uvula  Gerd – gastro esophageal reflux disease – when we have a weak lower esophageal spinclar – this is serious because this skin in our esophagus is not as thick as lining of our stomach – when the acid from the stomach hits the lining of the esophagus it causes burning - pH2 o Esophagus – stratified squamous – mucous lining is not thick – acid backflow is not good  No digestive aid or enzyme in the esophagus  Proton pump inhibitors – reduce acid levels in stomach o Stomach – simple columnar  Cardia – closest to the heart  Fundus – extends up by the esophagus  Main Body  Pylorus  Then into the small intestines  Lower esophageal sphincter and Pylorus sphincter – doesn’t allow regurduation  Rugae – the bumps, contract on all the food material and slam it against rough surface with presence of rugae  Layers of Smooth Muscles  Longitudinal layer  Circular layer  Oblique layer  Chyme  Gastric Pit

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Fundic Glands  Chief Cells – secretes pepsinogen (inactive form of enzyme – must turn into active form of pepsin to digest proteins) and gastric lipase  Parietal Cells – secretes hydrochloric acid (allows for pepsinogen  pepsin, inactive to active HCl is needed)(release HCl separately, as H and Cl) and intrinsic factor o Gastric Bypass Surgery – create a pouch in the top of the stomach o Lap-Band Surgery – regulates speed of food coming into stomach (hopefully people feel full) Small Intestine – 20 feet in length but 1 inch in diameter  Contains villi (extensions) – 4 to 5 million – present to inches absorption area – count on them to delivery nutrients to other cells o Microvilli – extension at the edge of villi  Absorption cell (digests and absorbs nutrients) – produce Brush Border enzymes, digest carbohydrates and proteins  Enterokinase – specifically involved in protein digestion  Maltose = maltose  glucose and glucose  Sucrase = sucrose  glocuse and fructose  Lactase = lactose  glucose and galuctose  Aminopeptidace o Paneth Cell – secretes lysosome and is capable of phagocytosis – allow for the kill of anything that could infect o Goblet Cells – secrete mucus  Digestion completed and absorption of nutrients  Three parts o Duodenum o Jejunium o Ileum CHO – Carbohydrates  Starts  mouth – salivary amylase  Completed  small intestine (pancreas, liver, gallbladder – secretions comes from these areas – as well as brush border enzymes) Protein  Start  stomach (using pepsin) – pancreas  Completed  small intestine (brush border enzymes help – entrokinase allows for proteins to turn into amino acids) Fat 

Pancreatic Lipase (in small intestine)

Nucleic Acids  Broken down by enzymes called nucleases (in small intestine) – break down back into sugar rings and nitrogen bases

Accessory Digestive Organs  Pancreas – deposit substances within the small intestine o Granular tissue o Endocrine function – cells in the pancreas that will release certain hormones (don’t aid in digestion) – ductless glands  Islets of Langerhans – produce hormones and regulate blood sugar levels (glucose) – no aid in digestion  Alpha – produce glucagon – aid the body when there is too little glucose – works at the level of the liver o Glucagon  glucose = blood sugar raises  Beta – produce insulin – aid the body when there is too much glucose o Takes excess glucose  glucagon = decrease in blood sugar o Exocrine function – release of fluids that flow out of a duct and then into duodenum of small intestine  Acinar Cells (acini) – produce digestive juices that will go into the duct and be delivered to the small intestine – 7.1 and 8.2 pH  Stomach contracts and fluids from pancreas immediately raises pH  Clear/watery fluid  Pancreatic Amylase – digests carbohydrates  Pancreatic Lipase – digests lipids/fats  Ribonuclease and Deoxyribonuclease – digest nucleic acids  Protein digesting enzymes – released from the pancreas and go into the duodenum  Inactive forms must be converted into active forms o Membrane bound enterokinase (brush border enzyme) – which allows trypsinogen to convert into trypsin – without all other conversions would not be able to occur o Procarboxypeptidase (inactive)  Carboxypeptidase o Chymotrypsinogen (inactive)  Chymotrypsin (active) o Trypsinogen (inactive)  trypsin  Liver – gets rid of bile o Second largest organ in the body – below diaphragm – majority of liver sits on right side of body o Produces heparin – anticoaguient (therefore blood doesn’t always clot) o Contains enzymes – present to break down toxic poison  NH2 = amine group (not toxic to the body – but can pick up another hydrogen converting to NH3 = ammonia which is toxic to the body) enzymes take NH3 and break it down to urea o Destroys old red blood cells – Kupfer Cells break down RBC  Broken down RBC due to broken down hemoglobin cause a pigment called Bilirubin o Stores vitamins – stores fat soluble vitamins  Vitamin A, D, E, K, B12  Iron  Copper o Maintain blood glucose levels – stores glycogen o Produces bile – breaks down fat (emulsifies lipids)

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Presents of bile aids pancreatic lipase  1 glycerol + 3 fatty acids  Chylomicrons – tiny droplets of fat o Left and right lobe to liver o Hepatic duct system – left and right – which merge into common hepatic duct  common bile duct  deposit bile into duodenum  sphincter of oddi/hepatic ampulla  Sphincter of Oddi – regulates what comes down the common bile duct and the pancreatic duct o What can go wrong?  Hepatitis A – infectious hepatitis  Virus caused by/thrives off of fecal contamination  Doesn’t do serious liver damage – curable  Always infecting hepatocytes (main cells in liver)  Hepatitis B – comes from an introduction of blood from the blood supply (body fluids, syringe, blood transfusion)  Causes serious damage  Hepatitis C – from blood transfusion  Most serious – long lasting  Can lead to a different disease – Cirrhosis o Dark brown or black o Reduced in size o Deathly  Gall Bladder – stores bile o Stored bile is released through cystic duct o Gall Stones – caused by to much cholesterol in the ball bladder  Large Intestine – colon o 5 feet in length – 2.5 inches in diameter o Extends from ileum of small intestine and goes to the anus o Illeum (starts)  Ascending Colon  (BEND) Right Colic (Hepatic) Flexure  Transverse Colon  Left Colic (Splenic) Flexure  Descending Colon  Sigmoid Colon  Anus o Ileocecal Sphincter (valve) o Water absorption occurs o Control release – internal anal sphincter (involuntary – smooth muscle tissue) and external anal sphincter (voluntary – skeletal muscle tissue) o Defecation – 5 to 10 hours after eating o Diverticuli – little out pouching – weakness in wall o Diverticulitis – o Sigmoidoscopy – examination of only the sigmoid colon o Colonoscopy – examination of the entire colon Digestive Hormones  Not a direct effect – hormone go into blood supply then go into target organ  Gastrin o When food comes into the stomach it stimulates the G cells  G cells in the gastric pit

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 G cells produce gastrin o Gastrin is released from G cells into the circulatory stomach, must go through blood supply and comes back to the stomach and stimulates the released of gastric juice which aid in digestion Entrogastrone o Released by duodenum when fat comes into the stomach o Enterogastrone has to go into the blood supply, then to the stomach and the effect it has here is inhibits stomach contractions – to stop food from getting pushed through because fat needs time to digest o Contractions of stomach when empty are signaled by growling of the stomach Secretin o Acid in the stomach is not projected into the duoduem o When acids (pH 2) hits the duoduem wall it releases secretin and goes through the circulation which stimulates the pancreas and then to the bicarbonate enzyme (pH 9) – raising pH level allows enzymes to work well Cholecystokinin o Fat hits the dueduem wall stimulates enteroendocrine cells which produce cholecystokinin which goes through circulation then directly induces contractions of the gall bladder (contains bile) – bile released down common bile duct into duoduem – bile is necessary for digestion of fat – (liver manufactures bile, gall bladder stores bile)...