Essential Standard 4.00: Understand reproductive and digestive physiology Objective 4.02: Understand digestive physiology

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.

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 Reticulum 1. 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. Omasum 1. Very little digestive action occurs in omasum. 2. Feed is primarily ground and squeezed. 3. Liquid is removed.

E. Stomach, Abomasum and Proventriculus 1. 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. Gizzard 1. Muscular contractions and grit/gravel break down feed. 2. Digestive juices from proventriculus continue to act on feed.

G. Small Intestine 1. 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 Juice a.Secreted by intestinal wall. b.Secretes several enzymes that break down proteins and sugars. iii.Bile a.Produced by the liver. b.Stored in the gall bladder. c.Yellowish green fluid. d.Acts on fats and fatty acids.

H. Cecum 1. Bacterial action breaks down roughage for horses. 2. Serves little function for other nonruminants and ruminants.

I. Large Intestine 1. Primary site of water absorption and formation of feces. 2. Some enzymatic and microbial digestion occurs on any remaining feed.

 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.