Page 3 - 86 human physiology part-2

Chapter 12

GI tract located within the mucosa. On the mucosa layer there are Villi and micro villi.

Submucosa: The submucosa is relatively thick, is highly vascular and serves the mucosa. The
absorbed elements that pass through the mucosa are picked up from the blood vessels of the
submucosa. The submucosa also has glands and nerve plexuses.

Muscularis: The muscularis is responsible for segmental contractions and peristaltic movement in
the GI tract. The muscularis is composed of two layers of muscle: an inner circular and outer
longitudinal layer of smooth muscle. These muscles cause food to move and churn with digestive
enzymes down the GI tract.

Serosa: The last layer is a protective layer. It is composed of avascular connective tissue and
simple squamous epithelium. It secretes lubricating serous fluid. This is the visible layer on the outside
of the organs.

Accessory Organs

1. Salivary glands

• a. Parotid gland
• b. Submandibular gland
• c. Sublingual gland

2. Tongue
3. Teeth

4. Liver

• Produces and excretes bile required for emulsifying fats. Some of the bile drains directly
into the duodenum and some is stored in the gall bladder.
• Helps metabolize proteins, lipids, and carbohydrates.
• Urea, chief end product of mammalian metabolism, is formed in liver from amino acids and
compounds of ammonia.
• Breaks down insulin and other hormones.
• Produces coagulation factors.

5. Gallbladder

• Bile storage.

6. Pancreas

• Endocrine functions: Digestive enzyme secretion.
• Stores zymogens (inactive enzymes) that will be activated by the brush boarder
membrane in the small intestine when a person eats protein (amino acids).
• Trypsinogen – Trypsin: digests protein.
• Chymotypsinogen – Chymotrypsin: digests proteins.
• Carboxypeptidases: digests proteins.

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