Human Digestive System

Functions

• Ingest food

• Digestion - Process organic molecules so they can enter cells (break down and absorb food).

• Eliminates waste materials

• Digestion is a metabolic activity.

Mouth

• Breaks down food into small pieces

• Begins starch digestion (amylase)

• Saliva produces amylase and lubricates food

• Moves food into esophagus

• Epiglottis covers trachea

• Peristalsis moves food to stomach

Epiglottis

Stomach

• First opening – cardiac sphincter• Muscles churn food – more mechanical

digestion.• Glands produce gastric juice = pepsin + HCl• Pepsin breaks down proteins (only at pH 2)• Food leaves after 2-4 hrs • Second opening – pyloric sphincter

Stomach

Small Intestine• Digestion is finished here

– Peristalsis finishes mechanical digestion– Pancreatic juice produces enzymes to finish chemical

digestion of fats, proteins and carbohydrates– The digested food passes into the blood vessels in the

wall of the intestine through the process known as diffusion. The small intestine is the site where most of the nutrients from ingested food are absorbed.

Question: What are the building blocks for fats, proteins, and carbohydrates?

Small Intestine Villi

• From the wall of the intestine project microscopic finger-like pieces of tissue called villi (Latin for "shaggy hair"). The function of the villi is to increase the amount of surface area available for the absorption of nutrients.

Liver

• Produces bile

Question: What is the function of bile?

Bile is stored in the gallbladder.

Liver and Gall Bladder

Large Intestine

• Absorbs water

• Bacteria live here (produce methane)

• Bacteria produce B vitamins and Vitamin K

• Stores solid waste in rectum until elimination.

Digestive System Disorders

• Tooth Decay – caused by bacteria. Too much sugar and too little brushing.

• Ulcers – open, painful sore in the stomach lining

• Appendicitis – infection of the appendix• Diarrhea – watery feces. Feces do not

remain in large intestine long enough for water to be absorbed.

• Constipation – Feces remain in colon too long. Caused by too little fiber and water.