Digestive System

Purpose The digestive system is the organ system that breaks down food into carbohydrates, proteins, fats, vitamins, and nutrients for the body to use for energy

Nutrients A nutrient is a substance that the body breaks down and uses to grow, repair, and function

6 Processes of Digestion Ingestion Secretion Mixing & Movement Digestion Absorption Excretion

Alimentary Canal Also called the Gastrointestinal (GI) Tract A long, hollow, twisted, and coiled tube that runs through the body It includes: Mouth, throat, esophagus Stomach, small intestine, large intestine, rectum, anus

1. Ingestion Food enters the digestive system through the mouth eating

2. Secretion Process by which a substance is released from an organ or gland to assist in digestion The body secretes almost 2 gallons of digestive fluids per day! Saliva Mucus Hydrochloric acid Bile

Saliva: produced by salivary glands Watery mixture with digestive enzymes Enzymes speed up a reaction Speeds up the break down of food into simpler substances Moistens food

Hydrochloric acid strong acid that breaks food down in the stomach

Mucus Lubricant: helps food to slide down esophagus easily Protection: mucus lines the stomach walls to protect it from the strong acid inside

Bile Produced by liver Stored in gallbladder Released into the small intestine Thick green fluid Breaks down large fat droplets in the

3. Mixing & Movement Mixing begins with the chewing muscles in the mouth Tongue(large muscle) helps to form the bolus: soft, round mass of chewed food

3. Mixing & Movement (cont) The tongue helps to move the food into the pharynx Movement continues as the food moves through the digestive tract

3. Mixing & Movement (cont) Most of the mixing happens in the stomach Food is mixed with gastric juice Gastric juice is a mixture of mucus, hydrochloric acid and enzymes, especially pepsin

Protease A protease is an enzyme that breaks down proteins Pepsin is a protease in gastric juice

4. Digestion Digestion is the actual breaking down of complex food into basic building blocks

2 types of Digestion A)Chemical digestion: the breakdown of food by chemical means through enzymes It happens in The mouth (saliva) Stomach( protease & hydrochloric acid) Small intestine (enzymes from pancreas and bile from gallbladder) Large intestine (gut flora)

Gut Flora Symbiotic bacteria that break down some materials

2 types of Digestion (cont) B) Mechanical Digestion: the physical breaking down of food. It involves: chewing, churning, & segmentation

5) Absorption This is the process by which substances are passed from the digestive tract into the blood. The blood transports them to other parts of the body Mostly occurs in the small intestine Nutrients are absorbed into capillaries

6)Excretion This is the removal of waste products Digestive waste products accumulate in the large intestine Remaining water is absorbed Solid wastes (feces) are stored in the rectum and eliminated through anus.

Organ Systems related to Digestion 1) Nervous System: prepares for food by contracting stomach or triggering salivary glands

Organ Systems related to Digestion (cont) 2)Endocrine System: releases hormones that regulate body functions. Some of these hormones determine production of digestive juices, control stomach muscle contractions, control absorption rate of nutrients

The Mouth Both chemical and physical digestion takes place in the mouth It contains the teeth, tongue, and salivary glands

Teeth Adult jaw contains 32 teeth 4 types of teeth

Incisors 8 total (4 top, 4 bottom) Chisel shaped Biting large pieces.

Cuspids Also called canine teeth 2 upper, 2 lower Cone-shaped For grasping & tearing food

Bicuspids Also called premolars 4 top, 4 bottom Flat surfaces For grinding food

Molars Similar to premolars, but larger 6 on bottom, 6 top

A tooth is made of…. Enamel: hard tissue on outside of tooth Crown: the part of tooth above gum Root: part of tooth that anchors it into gum Cementum: a thin, bony material that fixes the root to the jaw Dentin: largest part of tooth, hard bone-like tissue under enamel

Salivary Glands Three sets of glands Release saliva for chemical digestion

Tongue Tongue: primary organ of taste Taste buds: send taste information to brain where it is processed Shapes food into the bolus and directs it into the pharynx

Esophagus Movement of muscle contractions which push the food is called peristalsis

Structure of the Stomach Hollow, muscular sac Below the diagram, left side Can expand to about 2 liters Food remains in stomach for 1-2 hours Muscle contractions cause the bolus to mix with gastric juice Now the bolus is called chime.

Small Intestine Long, hollow, muscular tube Between 18-23 feet Length provides surface area and time for the absorption of nutrients.

Villi Small folds in the small intestine Contain artery, vein, and capillaries The capillaries absorb nutrients into the blood

Duodenum: entrance to small intestine from stomach This is where the bile and other enzymes from pancreas an gallbladder

Large Intestine Has a larger diameter than small intestine Less than 5 feet long Function: 1) to absorb any remaining water, electrolytes, and vitamins in the colon 2) remove wastes through rectum and anus.

Liver 2nd largest organ Under right rib cage