Sarah Brantner: Compendium Four: Digestive System and Nutrition

I. Digestive System and Nutrition
A. Overview of Digestion
B. First part of the Digestive System
C. The Stomach and Small Intestine
D. Three Accessory Organs and Regulation of Secretions
E. The Large Intestine and Defecation
F. Nutrition and Weight Control.

I. Digestive System and Nutrition

A. Overview of Digestion

1. This diagram is the GI tract and the organs that are associated digestion.

(http://en.wikipedia.org/wiki/Image:Digestive_system_diagram_en.svg)

2. Digestion has 5 different processes involved

Ingestion- When food is processed through the mouth.
Digestion- When food is chewed up into small pieces. Digestive enzymes are involved in this process.
Movement- The movement of food through the GI tract
Absorption- When nutrients from food enter the blood system

Elimination- The process of defecation through the anus

3. The GI tract has 4 different layers

First layer is Mucosa (Produces mucous)
Second layer is submucosa (carry nutrients absorbed by mucosa)
Third layer is muscularis (helps with movement)
Fourth layer is serosa (secretes fluid)

B. First part of the Digestive Tract

1. The Mouth

The first part of digestion starts here with the ingestion of food.
3 pairs of salivary gland that help with movement of food (saliva)
Teeth are responsible for grinding the food into small pieces (mechanical digestion)
The tongue is responsible for mixing food with saliva for easy movement.

2. The Pharynx and Esophagus

Mouth and nasal passages make up pharynx
Swallowing is said to be a reflex once food is pushed back into pharynx
Food usually enters the esophagus, and the esophagus is only there to transport food, no chemical digestion occurs.

People do not breathe when they eat because the soft palate closes off nasal passage and the trachea moves up to close up the glottis

C. The Stomach and Small Intestine

1. The Stomach

Stores food, starts digestion, controls the movement to small intestine
do not absorb nutrients

Contains gastric glands which produce gastric juice, which break down food (pepsin is an enzyme that controls digestion of proteins)

Stomach empties in 2 to 6 hours

(http://www.besthealth.com/besthealth/bodyguide/reftext/html/dige_sys_fin.html)

2. Small Intestine

18ft in length
Has the enzymes to digest food
Duodenum is the first 25cm of small intestine and supports the transfer of the enzymes from the pancreas

The walls absorb molecules
Mucosa of the small intestines have villi ("fingerlike projections")

(http://www.besthealth.com/besthealth/bodyguide/reftext/html/dige_sys_fin.html)

D. Three Accessory Organs and Regulation of Secretions

1. Three Accessory Organs

Pancreas- (Pancreatic amylase- digests starch, Trypsin- digests proteins, Lipase-digests fats)----also controls blood glucose by producing insulin
Liver- Receives and filters blood . Removes any toxins from the blood. Is a storage organ. Produces bile
Gallbladder- Bile is stored here

(http://en.wikipedia.org/wiki/Image:Digestive_system_showing_bile_duct.png)

2. Regulation of Digestive Secretions

Digestive juices are controlled by nervous system and digestive hormones
When you smell food it initiates the production of gastric secretion.

E. The Large Intestine and Defecation

1. Large Intestine

Absorbs water (helps with hydration)
No production of enzymes or absorption of nutrients
Forms feces (3/4 water and 1/4 solids)
Defecation is getting rid of feces. Feces leave the intestines, then gather in the rectum until defecation
Defecation helps maintain homeostasis