Process of Digestion
Mouth: Enzyme amylase breaks the chemical bonds.
Esophagus: Epiglottis prevents food from entering the lungs. Peristalsis helps food pass through smooth muscles.
Stomach: Chemical digestion (pepsin breaks down proteins with acid). Mucus protects the stomach. Mechanical digestion produces chyme. Cardiac sphincter closes the stomach.
Small Intestine: Chyme enters the small intestine. Bile is released to aid in fat digestion. Enzymes from the pancreas and duodenum complete digestion. Nutrients are absorbed by the villi. Undigestible substances go to the large intestine for elimination.
Functions of the Pancreas:
- Hormones to regulate blood sugar levels.
- Produces enzymes to break down carbohydrates, lipids, and nucleic acids.
- Produces sodium bicarbonate to neutralize stomach acid.
Functions of the Liver & Gallbladder:
Liver produces bile and the gallbladder stores it.
The Excretory System:
Lungs: Get oxygen into the body and eliminate carbon dioxide.
Skin: Removes excess water, salts, and a small amount of urea.
Liver: Converts harmful wastes into less harmful wastes.
Kidneys, Ureter, Urinary Bladder, Urethra:
The kidneys are the major organs of excretion. They remove excess water, urea, and metabolic wastes. Kidneys consist of nephrons where most of the work takes place. The liquid passes through the glomerulus, surrounded by Bowman's capsule. Then, it passes through the loop of Henle, which conserves water and minimizes the volume of the filtrate. After that, the urine goes through the ureters, which connect the kidneys to the urinary bladder. In the urinary bladder, urine is stored until it is released through the urethra.
When the kidneys can no longer filter blood and maintain homeostasis, the patient must receive dialysis or undergo a kidney transplant. There are two types of dialysis.
- Uric acid
- Amino acid
- Carbon dioxide
- Electrolytes (Na+, K+)