Digestive system - GI tract

GI tract Definition

Gastrointestinal tract, starts in the mouth and ends in the anus

4 layers of the GI tract

1. Mucosa - inner most layer made of epitheleal tissue

2. Submucosa - Nerve and connective tissue (2nd layer)

3. Muscularis Externa - Muscle tissue (3rd outer layer)

4. Serosa - Connective tissue (Outer layer)

Stage 1 : Ingestion compoonents

Mouth - Chews food and adds saliva to moisten

Teeth - Crown: covered by enamel (hardest substance in the body), inside is softer tissue including nerve

Tongue: moves food around as you chew

Epiglottis Function

Flap of skin that covers the respiratory tract so the chewed food goes down the esophagus instead

Amount of teeth in Adults and children

20 baby teeth

32 adult teeth

Teeth anatomy

16 per jaw

4 incisors (flat chisel front)

2 canines (pointed, sharp)

4 permolers

6 molers (2 wisdom teeth)

Stomach definition

collapsible bag below the diaphragm that can hold 2-4 L of food

Mechanical digestion

food mixes and moves around w the gastric juices to produce chyme (partially digested food)

Chemical digestion

Chemicals break down proteins and fats

Cells of the Stomach

Parietal Cells: make HCI (hydro chloric acid)

• Most acidic body fluid (pH of 2)

• loosen food + kill bacteria

Chief cells

• Produce pepsin, an enzyme to break down proteins

Small intestine definition

7 meter length tube that finishes digestion and complete absorption

parts of the small intestine

1. Duodenum

2. Jejunum

3. ileum

Chyme travels from the Stomach to the SI through

Pyloric Sphincter and Valve

Small intestine functions

1. digest carbs + fats

2. completion of protein digestion

3. Absorb all SOM from breaking down food

Enzymes made in the SI

• Peptidase

• Maltase

• lactase

• Sucrase

Enzymes made in pancreas

• Trypsin

• Chymotrypsin

• Lipase

Enzymes that break down protein

• Peptidase

• Trypsin

• Chymotrypsin

Enzymes that break down carbs to sugars

• Maltase

• Lactase

• Sucrase

Enzyme that breaks down fats

Lipase

What other part of the digestive system breaks down fats?

The liver with a yellow brown liquid called bile

Bile functions

• is a salt

• dissolves cholesterol

• contains detergent and is stored in the gallbladder

• if not enough salt is present then it can form gall stones

How are nutrients absorbed in the SI?

lining the SI there are cells called villi and micro villi that absorb the nutrients

Large intestine functions

• absorb water from material remaining in the digestive tract

• solid material that is left is called feces

Peristalsis function

propels feces through large intestine and into the rectum, then to the anus

Large intestine parts

1. first part (connected to the caecum) Ascending colon

2. transverse colon

3. descending colon

4. Sigmoid colon

5. Rectum+Anus

What happens to carbs?

• turn into simple sugars (Monosaccharides)

• used by cells for cellular respiration

• extra is stored as glycogen

• extra converted to fat

What happens to Fats

• broken into glycecols and fatty acids

• go to liver for usage or stored as fat cadipose tissue

What happens to proteins

• broken down into amino acids

• used to make proteins in the body