Digestive System Notes

Mouth Carbohydrate digestion begins here! Ingestion = eating

Mechanical Digestion (breaking food into smaller pieces) Teeth: breaks down food Tongue: moves food around mouth

Chemical Digestion (bonds are broken) Saliva contains three things…

Water Mucus Salivary amylase = starch digesting enzyme

Pharynx

Pharynx (throat): chewed food is pushed by the tongue to the back of the throat which starts the swallowing reflex.

Epiglottis: a flap of tissue that prevents food and liquids from entering the trachea during swallowing.

Esophagus

Esophagus: the tube through which food passes from the pharynx to the stomach.

Peristalsis: the movement of food is aided by alternate waves of relaxation and contraction of muscles lining the esophagus.

Stomach: protein digestion starts here

Chemical digestion: the stomach contains two types of glands… Pyloric glands: secrete mucus which protects

the stomach from acid and enzymes Gastric glands: secrete hydrochloric acid and

the protein digesting enzyme pepsin.

Mechanical digestion: food is broken down by contractions of the stomach muscle

Sphincter: Cardiac sphincter: a valve between the

esophagus and stomach. Keeps food and acid in stomach.

Pyloric sphincter: a valve between the stomach and small intestines.

The flow of gastric juice is stimulated in three ways… 1. Thought ,sight, smell and taste of food 2. Food is present in stomach 3. Food stretches stomach.

Chyme: food mixed with digestive juices. A thin soupy liquid.

Small Intestines: most digestion occurs here!

Chemical Digestion: the chyme is mixed with three juices: 1. Intestinal juice 2. Pancreatic juice 3. Bile

Peristaltic movements:

The small intestines have a great amount of surface area for maximum absorption. This surface area is due to… 1. The small intestines are very long… 6.5

meters or ___ feet. The small intestines have villi which are finger

like projections.

villi

Absorption of nutrients occurs by diffusion and active transport through the walls of the cells lining the small intestine.

Simple sugars, amino acids, vitamins and minerals are absorbed into the capillaries.

Fatty acids and glycerol are absorbed into the lacteals

Large intestines: NO digestion occurs here

The large intestine has three functions: 1. Reabsorbs water 2. Absorbs vitamins that are produced by

bacteria Eliminates undigested and indigestible

materials.

Pancreatic Juice:

Secreted by the pancreas Passes through the pancreatic duct into the

small intestines Pancreatic juice contains

Sodium bicarbonate: helps neutralize stomach acid

Enzymes: to digest carbs, fats, and proteins

Bile

Secreted by the liver Stored in the gall bladder Passes through the bile duct into the small

intestines. Bile mechanically breaks down (emulsifies)

fats and oils.

Intestinal Juice

Secreted by the small intestines Intestinal juice contains:

Enzymes: which digest carbs, proteins, fats,

and nucleic acids.

diagram

Disorders:

Heartburn: Gastric ulcer: Diarrhea: Constipation: Gall Stones: Appendicitis: Lactose intolerance

…