Animal Digestion

What is the outermost layer of the GI tract, and what is its function?

The serosa is the outermost layer. It is connective tissue that secretes fluid to lubricate the outside of the GI tract.

What is the function of the muscularis layer in the GI tract?

The muscularis consists of two layers of smooth muscle tissue and is responsible for the movement of food through the GI tract via peristalsis.

What does the submucosa layer of the GI tract contain?

The submucosa is a vascular layer that contains blood vessels and has a rich nerve supply. It penetrates into other layers.

What is the function of the mucosa in the GI tract?

The mucosa is a mucus layer rich in goblet cells that secrete mucus into the lumen to protect and lubricate the GI tract.

What is peristalsis?

peristalsis is the involuntary contraction of smooth muscle tissue that moves food through the GI tract, such as in swallowing.

what is the LUMEN

Hollow portion of the GI tract

What is a bolus?

A bolus is partially digested food that is swallowed and moves through the GI tract.

What is chyme?

Chyme is food that has been further digested, containing digestive enzymes and acid, which moves from the stomach to the small intestine.

How does the esophagus move food?

The esophagus uses peristalsis to transport food from the mouth to the stomach.

What are rugae in the stomach?

Rugae are raised (folded) areas inside the stomach that contain gastric pits.

How many chambers does the ruminant stomach have, and what are they?

The ruminant stomach has 4 chambers:

1. Reticulum

2. Rumen

3. Omasum

4. Abomasum (the true stomach)

What is the function of the reticulum and rumen in ruminants?

The reticulum and rumen are sites of fermentation where microbes (including beneficial fungi and probiotics) help break down food.

What is the function of the omasum in ruminants?

The omasum absorbs water and minerals from digested food.

What is the function of the abomasum in ruminants?

The abomasum is the true stomach, containing rugae and gastric pits, where digestion continues.

What occurs during the cephalic stage of gastric secretion?

The cephalic stage is triggered by the thought, smell, or sight of food, which stimulates saliva production and the secretion of digestive enzymes.

What enzymes are secreted during the cephalic stage?

The enzymes secreted are:

• Salivary amylase (breaks down sugars)

• Lingual lipase (breaks down fats)

• Lysozyme (breaks down pathogens)

What happens during the gastric phase of gastric secretion?

The gastric phase involves the secretion of pepsinogen and hydrochloric acid in the abomasum, which helps digest proteins and activate pepsin.

What is the function of pepsinogen and hydrochloric acid in the stomach?

Pepsinogen catabolizes proteins, and hydrochloric acid assists in pathogen breakdown, activates pepsin, and lowers the stomach pH.

What happens during the intestinal phase of digestion?

During the intestinal phase, chyme enters the small intestine for nutrient absorption through microvilli.

What is the role of the microvilli in nutrient absorption?

Microvilli are raised areas of the small intestine that contain capillaries (for absorbing carbohydrates and proteins) and lacteal glands (for absorbing lipids).

What is absorbed by the capillaries and the lacteal in the small intestine?

Capillaries absorb carbohydrates and proteins, while the lacteal absorbs lipids (fats).