Science Digestive System

To break down food into small diffusible molecules that will move from the digestive system to the blood stream and then to the cells.

-Food is chewed -Saliva softens food with the enzyme ptyalin -Ptyalin starts breaking down starch - Food is swallowed - Epiglotis covers the trachea so food enters the esophagus

- Walls are very muscular - Gastric glands walls of stomach secrete HCI mucin adn enzymes that digest proteins - Rennin curdles milk - It breaks down large protein molecules into smaller protien chains -Food stays in the stomach for 4-6 hours -(Two sphinter muscels close the opening to the stomach to prevent food from backing up into the esophagus)

- 2 ducts enter the duodenum - The bile duct, brings bile (secreted by the liver) which changes pH of food to alkline; bile emulsifes (cuts up) fats -The pancreatic duct brings thousands of enzymes that break down fats, carbohydrates and proteins. fats- fatty acids and glycerol carbohydrates- glucose proteins - aminoacids

-Those small units of food are diffusible -They move to the blood stream - In the 2nd part of the small intestines there are special structures called villi that increase surface area (to make absorbtion more efficient)

-Blood capillaries -Fatty acids -Amino acids -Glucose -Glycerol -Lacteal with LYMPH = RED BLOOD CELLS AND PLATELETS (THE LIQUID PARTS)

-Glucose and aminoacids diffuse into blood in the capillaries of the villi. -Fatty acids and glycerol diffuse into the lymph in the lacteals in the villi. -Digested food is distributed to cells by blood.

-Cells of the colon absorb water from unabsorbed food that is leaving the body -Unabsorbed food exits the body at the anus as semisolid feces -Has a special bacteria that creats vitamin K (Vitamin K is critical in the clotting of blood)

-Secretes digestive enzymes -Secretes two hormones that work togeter to regulate blood sugar levels

-Secretes bile -Chops up dead red blood cells and stores iron from them (the iron is reused) -Secretes protien messanger molecules that are important in the immune system