Digestive System

Warm Up

• What does digestion mean?

• What does absorption mean in regards to the digestive system?

• How long are your intestines?

Functions of the Digestive System

3 main processes

• Digestion– the mechanical and chemical breakdown of foods for

use by the body’s cells.

• Absorption– the passage of digested food from the digestive tract

into the cardiovascular system.

• Elimination– The expulsion of undigested cardiovascular food or

body wastes.

• Digestion involves both mechanical and chemical processes.

• Mechanical– Chewing– Mashing– Breaking food into smaller pieces

• Chemical– Digestive juices that breakdown food into

simpler substances

• The nervous system and the cardiovascular system play major roles in digestion.

• The nervous system triggers the digestive system process to begin at the smell or sight of food.

• After food has been broken down- nutrients- such as carbohydrates, proteins, fats, vitamins and minerals- are absorbed by the body.

Structures of the Digestive System

• The process of digestion begins in the mouth.

• Teeth– Break down food into smaller pieces.– Mastication: process of chewing

• Salivary Glands– Produce the first digestive juices– Saliva contains an enzyme that begins to break

down the starches and sugars in food.– Lubricates food and makes it easy to swallow

• Tongue– forms chewed food into easy to swallow size

– As you swallow• Muscles force food to pharynx, or throat.• The uvula, a small flap of muscle tissue closes off

opening to nasal passages. • Epiglottis, the flap of tissue covering the throat,

closes the opening to the trachea (windpipe).

The Esophagus

• When food is swallowed, it enters the esophagus.

• 10 inch long muscular tube that connects the pharynx with the stomach.

• Food is moved through the esophagus, stomach, and intestines through a process called peristalsis – a series of involuntary muscle contractions that move food through the digestive tract.

The Stomach• A hollow, saclike organ enclosed in a flexible

muscular wall that allows your stomach to expand when you eat.

3 Tasks of Digestion

#1: Mixing food with gastric juices: secretions from the stomach lining that contain hydrochloric acid and pepsin, and enzyme that digests protein.

#2: Storing swallowed food and liquid

#3: Moving food into the small intestine.– Food is converted into chyme: a creamy, fluid

mixture of food and gastric juices

• Pancreas– Produces enzyme that break down

carbs, fats, and proteins in foods.

• Liver– Produces another digestive juice: BILE

• A yellow-green, bitter fluid important in the breakdown and absorption of fats.

• Gallbladder– Stores the Bile in between meals.– Released at mealtime into the intestines.

Large and Small IntestineSmall Intestine• 20-24 feet in length• Broken into 3 parts

– Duodenum, jejunum & ileum

• The inner wall contains millions of finger-projections called villi, which are lined with capillaries.

• The capillaries absorb and carry nutrients throughout the body.

Large Intestine• Undigested parts of food pass into the colon, or large

intestine.• 2.5 inches in width and 5-6 feet in length.• Main function is to absorb water, vitamins, and salts,

and the eliminate waste.

• The body produces waste in the form of solids, gases and liquids.

• Solid waste is eliminated through the large intestine.

• Bacteria live in the large intestine to convert undigested food into feces, which is then excreted out of the body.

• The skin excretes some waste through the pores.

• Liquid waste is filtered through the urinary system.

Assignment:

• Page 446 - Q#1-5- AYR

• Color the digestive diagram on the back of the crossword puzzle.

3/18

• Jeopardy tomorrow!

• Quiz on FRIDAY

• Chapter 17 Lesson #2 & 3

• Q#1-4 & AYR (2)

• Q#1-4 & AYR (3)