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Chapter 18: Review Digestive and Excretory System Define digestion: process of breaking down food into molecules the body can use List the parts of the digestive tract and label on diagram. (p.985) Mouth: mechanical and chemical digestion Esophagus: Stomach: mechanical and chemical digestion Small intestine: Large intestine: absorption of water, minerals, and vitamins Accessory organs Liver: produces bile Gallbladder: Pancreas: produces digestive enzymes Define Saliva: mixture of water, mucus, and amylase (breaks down starch) moistens food for swallowing Bolus: Peristalsis: rhythmic contractions that move bolus through the esophagus Gastric fluid: carries out chemical digestion in stomach Pepsin: Hydrochloric acid: lowers pH so pepsin can work Mucus: protective coating for stomach Ulcer: sore in stomach caused by bacteria Bile: 1 Absorption: end products of digestion are transferred to blood and lymph (nutrients go into the blood from the small intestines) Villi: fingerlike projections in the lining of small intestines (do absorption) Define excretion: Function of kidneys: Remove nitrogen wastes Name and label the parts of the kidney (p.994) Cortex: outer portion Medulla: Renal pelvis: funnel-shaped structure in the center Renal artery: transports nutrients and wastes into kidney Renal vein: Describe how the nephrons function Nephrons: functional units of kidneys that remove wastes Bowman’s capsule: cup-shaped structure that holds glomerulus Glomerulus: Renal tubule: long tube that collects fluid filtered from blood Steps in the nephron 1. Filtration: Fluids forced from blood into Bowman’s capsule Filtrate: Water, urea, glucose, and vitamins move 2. Reabsorption: needed substance move back into the blood, 99% of water is returned to blood 3. Secretion: substances pass from blood into tubule (wastes go into tubule) Define Urea: Urine: produced in nephrons and contains toxins, urea, water, and salts 2 Describe how urine is eliminated Collecting ducts enter renal pelvis Ureter: tube from kidney to bladder Urinary bladder: sac that stores urine Urethra: tube from bladder and out of body Organs of excretory system Lungs: Skin: eliminate sweat to remove excess water and salt Kidneys: nitrogen waste in the form of urine 3