1. Digestive System

2. Digestive System Organs Mouth (oral cavity) Salivary Glands Esophagus
Stomach
Small Intestine
Large Intestine
Rectum

3. Digestive System The 4 Components
Ingestion – the taking in of nutrients (eating).
Digestion – the breakdown of organic molecules into smaller complexes.
Absorption – the transport of digested nutrients to the tissues of the body.
Egestion – the removal of materials from the food that the body cannot digest.

4. Digestive System Oral Cavity
Physical Digestion starts in the mouth where food is chewed into a bolus (ball).
Salivary glands secretions activate the taste buds & lubricate the passage of food.
Different types of nerve cells
respond to specific flavours.
Sweet – tip of tongue
Bitter – back of tongue
Salty – front sides
Sour – back sides
(sugar & salt test)

5. Digestive System Esophagus
Once swallowed, food travels from the mouth to the stomach via the esophagus.
Involuntary contractions called peristalsis move the bolus down the esophagus.
This will still work even if you stand on your head.

6. Digestive System Stomach
The stomach is the site of food storage and initial protein digestion.
Sphincter muscles regulate the movement of food into & out of the stomach. (like a drawstring)
Cardiac sphincter allows food to enter.
Pyloric sphincter allows food to leave.

7. Digestive System Stomach Stomach can hold about 1.5L of food.
Millions of secretory cells line the inner wall.
Mucous cells secrete a protective coating.
Parietal cells secrete hydrochloric acid (HCl).
Peptic cells secrete a protein-digesting enzyme called pepsinogen.
Pepsin breaks proteins into peptones (chains of amino acids)

8. Digestive System Stomach
The stomach is lined with a mucous membrane to protect it from the HCl.
When the mucous membrane breaks down, the cell membrane is exposed to the acid & an ulcer forms.

9. Digestive System The Small Intestine
The small intestine is about 7m long but very narrow.
The majority of digestion occurs in the duodenum first part of the small intestine.
The second part is called the jejunum.
The last part is called the ileum.

10. Digestive System The Small Intestine (SI)
Most absorption takes place in the small intestine.
This happens through villi.
(long finger-like tubes)
Villi increase the surface area of the SI, but also have microvilli, more tubes which increase the surface area even more.

11. Digestive System The Large Intestine (LI)
Any indigestible food is moved to the LI.
Stores wastes & absorbs water.
As wastes build up it triggers receptors in the walls prompting a bowel movement.
Bowel movements ensure removal of toxic wastes from the body. The longer these wastes stay in the LI the more chance you have of getting colon cancer.

12. Digestive System Rectum & Anus
All solid wastes are expelled through the rectum and out the anus.
The anus is controlled by a sphincter which opens to release solid waste (feces).
Yes…all good things must come to an end!