NURSE-UP DIGESTIVE SYSTEM AKA G.I. SYSTEM
The digestive system is used for breaking down food into nutrients which then pass into the circulatory system and are taken to where they are needed in the body. Introduction
Introduction There are four stages to food processing: 1. Ingestion: taking in food 2. Digestion: breaking down food into nutrients 3. Absorption: taking in nutrients by cells 4. Egestion (Defecation): removing any leftover wastes
Digestion Types Mechanical (physical) Chew Tear Grind Mash Mix Chemical Enzymatic reactions to improve digestion of Carbohydrates Proteins Lipids
Digestive System Organization Gastrointestinal (Gl) tract Tube within a tube Direct link/path between organs Structures Mouth Pharynx Esophagus Stomach Small intestine Large Intestine Rectum
Accessory Organs Not part of the path of food, but play a critical role. Include: salivary glands, liver, gall bladder, and pancreas
Begins when food enters the mouth. It is physically broken down by the teeth. It is begun to be chemically broken down by amylase, an enzyme in saliva that breaks down carbohydrates. Mouth
Salivary Glands (Accessory Organ) Small intrinsic glands found under mucous membrane of mouth, lips, cheeks and tongue secrete saliva at constant rate 3 pairs extrinsic glands connected to oral cavity by ducts parotid, submandibular and sublingual
Saliva Functions of saliva moisten, begin starch and fat digestion, cleanse teeth, inhibit bacteria, bind food together into bolus Hypotonic solution of 99.5% water and solutes salivary amylase, begins starch digestion lingual lipase, digests fat activated by stomach acid mucus, aids in swallowing lysozyme, enzyme kills bacteria immunoglobulin A, inhibits bacterial growth ph of 6.8 to 7.0 (relatively neutral) Produce 1 1.5 L per day
Tongue & Pharynx The tongue moves the food around until it forms a ball called a bolus. The bolus is passed to the pharynx (throat) and the epiglottis makes sure the bolus passes into the esophagus and not down the windpipe!
Esophagus ~ 10 long Secretes mucus. The bolus passes down the esophagus by peristalsis. Peristalsis is a wave of muscular contractions that push the bolus down towards the stomach.
Cardiac Sphincter To enter the stomach, the bolus must pass through the lower esophageal sphincter (cardiac sphincter), a tight muscle that keeps stomach acid out of the esophagus.
The stomach has folds called rugae and is a big muscular pouch which churns the bolus (Physical Digestion) and mixes it with gastric juice, a mixture of stomach acid, mucus and enzymes. Stomach
The acid kills off any invading bacteria or viruses and triggers the release of pepsin. The enzymes help break down proteins and lipids. (Chemical Digestion). The mucus protects the lining of the stomach from being eaten away by the acid. Stomach
The stomach does do some absorption too. Some medicines (i.e. aspirin) water alcohol The digested bolus is now called chyme and it leaves the stomach by passing through the pyloric sphincter. Stomach
~7 meters long Secretes digestive enzymes The majority of absorption occurs here. The liver and pancreas help the small intestine to maximize absorption. Small Intestine
Small Intestine Most nutrients from the food pass into the bloodstream through the small intestine walls. Lipids pass into the lymphatic system via lacteals. Absorbs: 80% ingested water Vitamins Minerals Carbohydrates Proteins Lipids The small intestine is broken down into three parts:
Duodenum (Small Intestine) 1. Duodenum Bile, produced in the liver but stored in the gall bladder, enters through the bile duct. It breaks down fats. The pancreas secretes pancreatic juice to reduce the acidity of the chyme.
Liver (Accessory Organ) Directly affects digestion by producing bile Bile helps emulsify fat Filters out toxins and waste including drugs and alcohol
Gall Bladder (Accessory Organ) Stores bile from the liver, releases it into the small intestine.
Pancreas (Accessory Organ) Endocrine and Exocrine Gland Secretes insulin and glucagon into the blood Secretes pancreatic juice into duodenum Water, enzymes, zymogens, and sodium bicarbonate Zymogens become enzymes once activated in the small intestine.
2. Jejunum Jejunum (Small Intestine) The jejunum is where the majority of absorption takes place. It has tiny fingerlike projections called villi lining it, which increase the surface area for absorbing nutrients.
Jejunum (Small Intestine) Each villi itself has tiny fingerlike projections called microvilli, which further increase the surface area for absorption.
Ileum (Small Intestine) 3. Ileum The last portion of the small intestine is the ileum, which has fewer villi and basically compacts the leftovers to pass through ileocecal valve into the caecum of the large intestine.
The large intestine (or colon) is used to absorb water from the waste material leftover and to produce vitamin K and some B vitamins using the helpful bacteria that live here. Large Intestine
All leftover waste is compacted and stored at the end of the large intestine called the rectum. When full, the anal sphincter loosens and the waste, called feces, passes out of the body through the anus. Large Intestine
Questions Complied by: D. Leonard Learning Specialist The Academic Support Center @ Daytona State College http://www.daytonastate.edu/asc/ascsciencehandouts.html