The Digestive SystemChapter 13

Why Do We Eat?

2

What is digestion?

Let’s find out what happened to your breakfast today!

4

DigestionProcessing of Food

(copy)

• Type one • Mechanical (physical)• Chewing• Tearing• Grinding• Mashing• Mixing

(Copy)

• Type two • Chemical• Catabolic

reactions• Enzymatic

hydrolysis• Carbohydrates• Proteins• Lipids

• Ingestion• Movement• Digestion• Secretion• Absorption• Excretion

Functions of the digestive system(copy)

(Copy)• Gastrointestinal System

• Includes alimentary canal and accessory organs

• Accessory organs: Salivary glands, tongue, teeth, liver, gallbladder, and pancreas

Steps in Digestion(Copy)

• Mouth – Crushing and grinding• Stomach – Chemical Breakdown• Small Intestine – Useful material

extracted• Colon – Water removal

Mouth-mechanical digestion mastication) = teeth, tongue-chemical digestion = saliva

Uvula – prevents food entering the nose

Alimentary canal (copy)2 main functions:•Digesting and absorbing nutrients•Protecting from invasion

(COPY)

Epiglottis – safety hatch. A flap of cartilage prevents food from entering the trachea

Trachea - windpipe

11

Swallowing (Copy)

Sequence• Voluntary stage

• Push food to back of mouth

• Esophageal stage• Open esophagus• Start peristalsis

Oesophagus (Copy)-transfers food to stomach by peristalsis

Cardiac sphincter

-opens to allow food oesophagus stomach

-heartburn –acid escapes stomach

13

Peristalsis and Segmentation

http://35.9.122.184/images/41-AnimalNutrition/41-16-Duodenum-L.gif

(Copy) Stomach

Stores the food you eatDigestion = chemically - breaks it down into tiny pieces

= mechanical – mixes food with digestive juices acid in the stomach kills bacteria

Cardiac sphincter

Pyloric sphincter

Slowly releases food into intestine

Small Intestine (copy)Around 6m in an adultFood takes 1-6 h to pass throughEnzymes and bile are added2 main tasks = digestion, absorption

nutrients pass into bloodstream through small intestine walls

16

Anatomy of the Large Intestine

Large Intestine (copy)

• About 1.5 meters long• Accepts what small

intestines don’t absorb.

• Absorbs water and minerals from the waste matter.

Liver (copy)

• Directly affects digestion by producing bile• Bile is an

enzyme that helps dissolve fat

• Processes nutrients in the blood, filters out toxins and waste.

19

Related Organs

Gall Bladder (copy)

• Stores bile from the liver

• Delivers bile when food is digested

• Fatty diets can cause gallstones

Pancreas (copy)

• Produces compounds to digest fats and proteins

• Neutralizes acids that enter small intestine

• Regulates blood sugar by producing insulin

22

The Organs and Positions in the Abdominal Cavity

Rectum and Anus (copy)

• Rectum• About 15cm

long• Stores waste

before egesting.

• Anus• Muscular ring

that controls egesting.