The Digestive System

The Digestive SystemFunction: Breaks down

foods into simpler molecules that can be absorbed and used by the cells of the body.

Structures

• Organs: mouth, pharynx, esophagus, stomach, small intestine, and large intestine.

• Accessory glands: salivary glands, pancreas, and liver

Types of Digestion

• Mechanical- grinding and crushing the food into smaller pieces that are easier to process. (example: teeth & chewing) Causes a physical change

• Chemical- enzymes (specialized proteins) breaking to food down into simpler molecules your cells can use. Causes a chemical change

Mouth The mouth is where the digestive system begins.

Mechanical and chemical digestion occur here.

- Teeth tear and crush food

Mouth, cont.

• Salivary glands release saliva into the mouth that contains enzymes like amylase to break down starches into sugars.

Pharynx Esophagus

• Bolus (food ball) passes from mouth through the pharynx into the esophagus

• Peristalsis- smooth muscles contract, pushing food down to the stomach.

Stomach: Structure/Fxn.

• Continues both mechanical and chemical digestion

• Smooth muscle churns and mixes food to produce chyme

• HCl makes it acidic

Chemical Digestion- Enzymes

Enzyme Activity #1

Small intestine: Absorption

• Duodenum, jejunum, ileum (together= 6 m)

• More enzymes

• Absorption occurs on the villi, which are lined with capillaries

Large Intestinea.k.a. colon

• Absorption of water– If too little is absorbed = diarrhea– If too much is absorbed = constipation

• Unabsorbed material passes through rectum, then anus

Accessory Digestive Organs• Pancreas- VERY

important fxns.– Regulate blood sugar

(diabetes)– Produces several

enzymes– Produces sodium

bicarbonate—a base• Why is this important?

• Liver- produces bile which is then stored in the gall bladder

The Excretory System

•Structures: skin, lungs, kidneys, ureters, urinary bladder, urethra

•Function: Remove waste products

The Kidneys

Primary organs of the excretory system.

• Remove waste products from the blood

• Maintain blood pH

• Regulate water content of the blood

• Waste is excreted as urine.

The kidneys, cont.

•Located on either side of the spinal column near the lower back.

Nephron Unit

The functional units of the kidney are called nephrons. Each nephron is a small,independent processing unit. Function:As blood enters a nephron through the inpurities are filtered out and emptied into the collecting duct.

Dialysis/Homeostasis by Machine

The kidneys are the master chemists of the blood supply.In dialysis,blood is removed from the body through a tube inserted in the arm and pumped through special tubing that acts like nephrons.

The Bladder

• Urine (waste) flows from the kidneys thru the ureters to the bladder where it is stored.

• Then, urine passes from bladder thru the urethra to exit the body