Digestion Copy everything in red The Digestive Systems Function As food passes through the digestive system, it gets broken down distributing its nutrient value to the body The function of each organ of the digestive system is to help convert foods into simpler molecules that can be absorbed and used by the cells of the body The Digestive System Structures The digestive system includes:
Mouth Pharynx Esophagus Stomach Small intestine Large intestine Major accessory structures that add secretions to the digestive system include: Salivary glands Pancreas Liver Figure 3810 The Digestive System Mouth Pharynx
Salivary glands Esophagus Liver Gallbladder (behind liver) Stomach Pancreas (behind stomach) Large intestine Small intestine Rectum
Mouth & Salivary Glands Teeth Protected by enamel Chewing begins the process of mechanical digestion = physical breakdown of large pieces of food into smaller pieces (cutting, tearing, crushing) Saliva Secreted by salivary glands Moisten food making it easier to chew Begins the process of chemical digestion = Amylase (digestive enzyme) chemically breakdown large starch molecules into smaller sugar molecules Lysozyme enzyme fights infection
Pharynx Remember from the Respiratory System: The pharynx (throat) is a tube in the back of the mouth that passes both air and food Epiglottis (flap of tissue) covers the trachea to ensure food continue to move along digestive tract Esophagus Food tube Bolus (chewed clump of food) moves along by contractions of smooth muscle surrounding the esophagus = peristalsis Cardiac sphincter closes esophagus after food has passed into the stomach preventing
stomach contents from moving back into the esophagus (heart burn occurs when stomach acid splashing into the esophagus) Stomach A large muscular sac made of smooth muscle that mechanically and chemically digests food Chemical digestion occurs as gastric glands in the stomach lining secrete mucus to protect the inner wall while pepsin and hydrochloric acid break down protein Ulcers = a hole in the stomach wall caused by a bacterial infection that eats away at the lining of the stomach
Mechanical digestions occurs as the stomach muscles contract to churn and mix stomach fluids producing a mixture = chyme Pyloric valve opens allowing chyme to flow from the stomach into the small intestine Duodenum More chemical digestion of chyme occurs in the duodenum (the first part of the small intestines) Chyme mixes with enzymes and digestive fluids from the pancreas and the liver (accessory structures) Pancreas
A gland that produces hormones that regulate blood sugar levels Produces enzymes that break down carbohydrates, proteins, lipids, and nucleic acids Produces sodium bicarbonates (a base) that neutralizes stomach acid Liver Produces bile = detergent dissolving fat droplets Bile is stored in the gallbladder Figure 3813 The Liver and the Pancreas
Section 38-2 Liver Gallbladder Duodenum Bile duct Pancreas Pancreatic duct To small intestine
Small Intestine Made of three parts: duodenum, jejunum, and ileum Where chemical digestion is completed The folded surfaces are covered with villi = small fingerlike projections that increase the surface area of the small intestines for greater absorption of nutrients The products of carbohydrate or protein digestion are absorbed into capillaries in the villi and microvilli Undigested fats are absorbed by lymph vessels = lacteals
Figure 3814 The Small Intestine Section 38-2 Villus Small Intestine Circular folds Epithelial cells Villi Capillaries
Lacteal Vein Artery The Digestive Enzymes KNOW THIS CHART Section 38-2 Site Enzyme Role in Digestion
Mouth Salivary amylase Breaks down starches into disaccharides Stomach Pepsin Breaks down proteins into large peptides Small intestine
(from pancreas) Amylase Continues the breakdown of starch Trypsin Continues the breakdown of protein Lipase Breaks down fat
Maltase, sucrase, lactase Breaks down remaining disaccharides into monosaccharides Peptidase Breaks down dipeptides into amino acids. Small intestine Large Intestine
Food entering large intestine is basically nutrient-free, mainly made of water, cellulose (fiber), and other indigestible substances Removes water left in the chyme by absorbing it across the large intestine wall If water removal is inefficient, diarrhea occurs and can be dangerous due to the loss of salts and water Intestinal bacteria help with digestion The appendix is believed to have formerly stored bacteria to assist with cellulose digestion Solid concentrated waste (feces) is excreted through the rectum
Excretion Copy everything in red Excretion Excretion = the process by which wastes are eliminated from the body The excretory system includes: Lungs: excrete gaseous carbon dioxide from cellular respiration Rectum: excrete solid undigested remains from food Skin: excretes excess water, salts, urea Kidneys and accessory organs The Urinary System
The urinary system rids the blood of wastes produced by the metabolism of nutrients and controls blood volume by removing excess water produced by body cells. The urinary system includes: Kidneys Urinary bladder Connecting tubules: Ureter Urethra The Urinary System DRAW & LABEL THIS Section 38-3
Kidneys Most people have 2 kidneys located on either side of the spinal column on your lower back Ureters = tubes that carry urine from each kidney to the urinary bladder Urinary bladder = saclike organ that stores urine until it can be excreted The kidneys filter blood by removing urea, excess water and other wastes collected as urine and the clean filtered blood returns to circulation Kidney Structure
Inner part = renal medulla Outer part = renal cortex Functional units of the kidney = nephrons About 1 million nephrons in each kidney Each nephron has its own arteriole (small artery), venule (small vein), and network of capillaries to filter blood Figure 3817 Structure of the Kidneys
Glomerulus Renal vein Ureter Collecting duct Vein To the bladder Artery
To the ureter Loop of Henle FILTRATIONREABSORBTIONSECRETION Urine The material that remains = urine containing urea, salts, water and other substances The loop of Henle conserves water and minimizes the volume of urine Urine is stored in the urinary bladder until it can be released from the body through a tube = urethra
Kidney Function The kidneys maintain homeostasis by: Regulating the water content of the blood (blood volume) Maintaining blood pH Removing waste products from the blood
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