AA22 Animal Science IIAnimal Anatomy & Physiology

Essential Standard 4.00: Understand reproductive and digestive physiology

Objective 4.02: Understand digestive physiology

Digestive System Physiology Terminology

A. Enzymes-organic catalyst substances that speed up the digestive process.

B. Rumination- process of forcing food back up the esophagus to be chewed again. Occurs only in ruminant animals. Also known as “chewing the cud.”

C. Bacteria and Protozoa- one-celled organisms. Found in the rumen and reticulum and aid in digestion.

D. Amino Acids- compounds that are the building blocks of protein. Contain carbon, hydrogen, oxygen and nitrogen. Essential for growth and maintenance of cells.

E. Villi- small finger-like projections in the intestinal wall that increase the surface area and aid in digestive absorption.

F. Gastric Juice- liquid that contains water, mucus, hydrochloric acid and digestive enzymes. Secreted by glands.

G. Chyme- partially digested feed that is acidic, semi fluid, gray, and pulpy. Produced in stomach and sent to small intestine.

H. Prehension- process of grasping feed with lips tongue and/or teeth.

Digestive System Physiology

A. Mouth, Teeth Tongue and Salivary Glands

1. Mouth and teeth masticate (chew) food to increase surface area of food particles.

2. Saliva in mouth stimulates taste and softens and lubricates food.

3. Saliva also contains salivary amylase and maltase enzymes to help change some starch to maltose (malt sugar).

4. Ruminants swallow food rapidly without chewing food adequately. They then ruminate feed.

5. Tongue guides feed to esophagus and can also aid in prehension for some species.

B. Esophagus- carries food from mouth to stomach through a series of muscular waves or contractions.

C. Rumen and Reticulum1. Responsible for breaking down forages. 2. When the ruminant animal is full they

will lie down to initiate the rumination process. Ruminants spend 5-7 hours per day ruminanting.

3. Contain microbes that convert low quality protein from forages into amino acids.

4. Large amounts of gas are produced in rumen (30-50 liters per hour). This gas must be belched or expelled to prevent ruminants from bloating.

5. Cattle often swallow foreign objects such as nails or wire because they eat rapidly and do not use lips to discriminate among food particles.

i. Hardware disease- common term for animals that become ill from these foreign objects.

ii. Prevented by inserting small magnet into reticulum. Holds foreign objects to prevent them from penetrating the heart.

D. Omasum1. Very little digestive action occurs in

omasum.2. Feed is primarily ground and squeezed.3. Liquid is removed.

E. Stomach, Abomasum and Proventriculus1. Responsible for breaking down finer feed

particles from concentrates. 2. Gastric juices secreted when feed enters

stomach/abomasum/proventriculus. i. Contain hydrochloric acid which stops action of

salivary amylase. ii. Contain additional enzymes that break down

feed. a. Pepsin- acts on proteins.b. Gastric lipase- acts on fats.

3. Muscular walls help churn and squeeze feed forcing liquids into small intestine. The gastric juices then continue to break down remaining or new feed. \

4. Very little feed gets “processed” in the proventriculus because poultry swallow food whole.

F. Gizzard1. Muscular contractions and grit/gravel

break down feed. 2. Digestive juices from proventriculus

continue to act on feed.

G. Small Intestine1. Primary site of nutrient absorption for

nonruminants and ruminants who are fed higher concentrate rations.

2. Villi line intestinal wall to increase surface area and aid in absorption of nutrients.

3. Chyme mixed with pancreatic juices, intestinal juices and bile.

i. Pancreatic Juice a. Trypsin- enzyme that breaks down remaining

proteins. b. Pancreatic amylase- changes starch that was not

processed by salivary amylase into maltose. c. Lipase- acts on fats to convert them into fatty

acids.

ii. Intestinal Juicea. Secreted by intestinal wall.b. Secretes several enzymes that break down

proteins and sugars.

iii. Bilea. Produced by the liver. b. Stored in the gall bladder.c. Yellowish green fluid.d. Acts on fats and fatty acids.

H. Cecum1. Bacterial action breaks down roughage

for horses. 2. Serves little function for other

nonruminants and ruminants.

I. Large Intestine1. Primary site of water absorption and

formation of feces. 2. Some enzymatic and microbial

digestion occurs on any remaining feed.

Student Assignment:

Label the digestive parts using page 116 of your textbook.

The provide the physiological action occurring in each part of the digestive system.

You need to label all parts, but provide the function for only the ones in your guided notes.

Poultry Example

Ruminant

Non Ruminant