Digestive System
The Digestive System Digestion: mechanical and chemical breakdown of food and absorption of nutrients Anatomy of the digestive system: Alimentary canal: 8 meter long muscular tube from mouth to anus (mouth, throat, esophagus, stomach, intestines) Accessory organs that aid in digestion (pancreas, liver, gallbladder, salivary glands)
Mouth Tongue: skeletal muscle, mixes food with saliva, aids in swallowing, has taste buds Teeth: 32 in adult, breaks food into smaller pieces Salivary glands: secrete saliva to moisten food and start chemical process of digestion; contains amylase- enzyme that breaks down carbohydrates
Pharynx and Esophagus Muscular tubes that propel food to stomach but do not digest food Esophagus- 25 cm long, has esophageal sphincter at entrance to stomach to prevent food from coming back up
Stomach Receives food from esophagus, mixes with gastric juice, begins protein digestion Gastric juice: mix of hydrochloric acid, pepsin (digests protein), mucus Mucus lining prevents stomach from digesting itself (acid eating through stomach wall) Chyme- product of food mixing with gastric juice, sent to small intestine
Small Intestine Receives secretions from pancreas and liver, digests chyme from stomach, absorbs nutrients, transports residue to large intestine Intestinal villi- fingerlike projections that line wall of small intestine, increase surface area for absorption Intestinal enzymes: Peptidase- protein digestion Sucrase, maltase, lactase- sugar digestion Intestinal lipase- fat digestion
Pancreas Secretes mix of digestive enzymes- pancreatic juice Enzymes in pancreatic juice: Pancreatic amylase- breaks carbohydrates into sugars Pancreatic lipase- digests fat Trypsin, chymotrypsin, carboxypeptidase- protein-splitting enzymes
Liver High rate of fatty acid metabolism Formation of glucose Very important role in protein metabolism Removes toxins, filters blood for damaged RBCs and foreign substances Secretes bile- helps digest lipids Excess bile stored in the gallbladder
Large Intestine Absorbs water and electrolytes, forms and stores feces Appendix- small projection with no function Intestinal bacteria break down cellulose (plant carbohydrates) and synthesize some vitamins Rectum- temporary storage for feces at end of large intestine Anus- opening at end of large intestine
Vitamins and Minerals Vitamins: organic compounds needed in small amounts for metabolism Fat Soluble Vitamins: stored in fat, so overdose is possible; Vitamins A, D, E, K Water Soluble Vitamins: dissolve in water, so any extra is excreted, not stored; B Vitamins, Vitamin C Minerals: small amounts of elements needed in metabolism; Calcium, Phosphorus, Potassium, Sodium, Magnesium
Digestive System Review Besides fat and protein digestion, what other important function does the liver perform? In what digestive organ do most of the nutrients get fully digested and absorbed? What organs play no role in digestion but are merely used for transport?
Urinary System
The Urinary System Functions: Remove salt and nitrogenous waste from blood Maintain water/electrolyte balance in body Regulates volume of body fluids Help control RBC production
Organs of Urinary System 4 main organs in urinary system: Kidney- filters waste out of blood and controls how much water is excreted Ureters- transport waste from kidneys to bladder Bladder- stores waste (urine) Urethra- transports urine from bladder to outside
The Kidney Nephron: site of blood filtration in kidney, about 1 million contained in kidney
Urine Formation 3 Steps: Glomerular Filtration: Water, ions, and other plasma substances are filtered out of blood and into glomerular capsule Tubular Reabsorption: certain substances from filtrate are reabsorbed (glucose, amino acids, water, some ions) Tubular Secretion: Waste substances missed in glomerular filtration are removed from blood (ammonia, hydrogen ions, potassium ions, penicillin, histamine)
Urine Composition Volume of urine related to fluid intake (drinking more fluids produces more urine), between 0.6 and 2.5 L per day About 95% water, with urea, uric acid, some amino acids and salts Urea and uric acid: by-products of metabolism of amino and nucleic acids
Urine Elimination Travel from kidney to bladder through ureters Bladder holds ~600 mL urine, urge to urinate comes from bladder contractions which start around 150 mL full Sphincter at bladder opening keep bladder closed, urination occurs when muscles relax and sphincter open