Chapter 18: The Digestive and Urinary Systems PDF

10/22/20 Chapter 18 Organ Systems The Digestive and Urinary Systems 1 10/22/20 The Digestive System Alim entary canal 1 M outh • Teeth reduce the size of food, increasing surface area available for digestion by enzym es. • Enzym es in saliva then start breaking down carbohydrates. 2 Pharynx •...

10/22/20 Chapter 18 Organ Systems The Digestive and Urinary Systems 1 10/22/20 The Digestive System Alim entary canal 1 M outh • Teeth reduce the size of food, increasing surface area available for digestion by enzym es. • Enzym es in saliva then start breaking down carbohydrates. 2 Pharynx • Epiglottis blocks the opening to the windpipe when we swallow, so that our food goes into our esophagus rather than our lungs. Accessory organs of the digestive system 3 Esophagus • The esophagus transports food to stom ach by rhythm ic waves of m uscle contractions called peristalsis. Liver • Produces bile which aids absorption of fats 4 Stom ach • Acidic gastric juices start breaking down foods. • The enzym e pepsin breaks down proteins. • M ucous prevents gastric juices from digesting stom ach. • Pyloric sphincter regulates m ovem ent of food from stom ach to sm all intestine. G all bladder • Stores bile and em pties into sm all intestine Pancreas • Produces digestive enzym es • Produces a buffer that neutralizes acidity of stom ach acid 5 Sm all intestine • M ost digestion of carbohydrates, proteins, and fats occurs here. • Nutrients are absorbed into the bloodstream . 6 Large intestine • W ater is reabsorbed. 7 Anus • Undigested m aterials are excreted as feces. Figure 16.8 Mouth à Pharynx à Esophagus Epiglottis: a flap made of cartilage tissue attached at the entrance It prevents food from going into the trachea (air pipe) and instead directs it to the esophagus (food pipe) Air pipe Food pipe Choking: if the epiglottis fails, the food goes into a wrong path and blocks the passage of air Treatment: Heimlich Maneuver 2 10/22/20 Stomach à Small Intestine à Large Intestine Gastric acid: digestive fluid formed in the stomach – pH 1~2, “acid reflux” Stomach ulcer: the destruction of the lining (epithelial tissue) of the stomach by gastric acid Small intestine is made of 3 parts: duodenum, jejunum, and ileum Appendix: a blind-ended tube attached to 1st part of large intestine (cecum) Accessory Organs of the Digestive System – Liver and Gall bladder • Liver – The largest glandular organ of the body - Metabolize and store nutrients - Produce bile – help dissolve fats • Gall bladder – store bile and secrete it into the duodenum Gall bladder Figure 16.6 3 10/22/20 Accessory Organs of the Digestive System – Pancreas • Pancreas – The glandular organ that produces digestive enzymes; secrete into the duodenum Amylase: digest carbohydrate - Lipase: digest fat - Protease: digest protein - Nuclease: digest nucleic acid - The Excretory System • An organ system that removes wastes and maintains balance of water, ion, and nitrogen in the body Kidney Ureters • Major organs of the excretory system: Bladder Urethra Figure 17.19 4 10/22/20 • Ureter: the tube from the kidney to the bladder Urethra • Urethra: the tube from the bladder to the outside • Bladder: a storage vessel for urine; enveloped in the detrusor muscle - Normal adult bladder holds ~ 400 ml of urine - Overactive bladder: a condition that results from sudden, involuntary contraction of the detrusor muscle • Kidneys filter the blood and transfer waste urine to the bladder • The functional units of a kidney are looped tubules called nephrons – four phases of function 5 10/22/20 Four Phases of Nephron Function Blood 1 3 Filtration: Blood pressure forces plasma into the nephron through tiny holes in the adjacent capillaries. Reabsorption: Sugars, amino acids, and water are reabsorbed into the blood. Salts are removed from the filtrate on the ascending limbs 2 Toxins 4 Water Salts Figure 17.20 Secretion: Wastes that are in low concentration in the blood are actively secreted into the far end of the nephron. Excretion: After the filtrate is further concentrated as the tube extends into the salty tissue of the kidney, urine is excreted into the bladder. Kidney Failure • Each kidney contains over a million nephrons – 85 miles of tubules per adult • The total volume of blood passes through the kidneys hundreds of times per day – Each kidney filters about 1000 liters of blood per day • Treatments to replace the work of kidneys if they fail: Kidney transplant - Dialysis: clinical purification of blood as a substitute - 6 10/22/20 • Dialysis works on the principles of the diffusion of solutes across a semi-permeable membrane; require 4 hrs each time, once every 3 days Peritoneal Dialysis: convenient (mobile) and low cost – good for people with high work demand; much slower 7