Digestive System Length The digestive tract extends from the lips to the anus. It includes the mouth, pharynx, esophagus, stomach, and the small and large intestines. Accessory glands include the salivary glands, the liver, and the pancreas.

Let’s Practice – Human Digestive System MODEL ( grab a notecard – be ready to do as it says and read the function)

1. Mouth – grasps the food 2. Teeth- provide mechanical digestion of feed by breaking, cutting, and tearing up food. The increase surface area aids in the chewing and swallowing process.

3. Tongue - covered with finger-like projections (papillae), contain taste buds. 4. Salivary glands - secrete saliva, that moistens food and is mixed with the food material to aid in swallowing. Saliva contains enzymes – speed up chemical reactions (digestion)

Water: moistens consumed feed and aids in the taste mechanisms. Mucin: lubrication aid for swallowing. Bicarbonate Salts: acts as a buffer to regulate pH of the stomach. Enzyme: salivary amylase initiates carbohydrate breakdown. Mature horses can produce 10 gal/day; cows- 12 gal/day; and sheep- 2 gal/day. What happens in the mouth?

5. Pharynx - funnels food into the esophagus, preventing food material from entering the lungs. 6. Esophagus hollow muscular tube from the mouth to the stomach; material is moved by a series of muscular contractions referred to as peristatic waves. Also serves as a storage for food (crop) in chickens.

7. Cardiac Sphincter: valve at the junction of the stomach & esophagus 8. Simple Stomach: Storage of ingested feed. Muscular movements (physical breakdown) Secretes digestive juices: 1) Hydrochloric Acid 2) Pepsin 3) Rennin Material leaving the stomach is called chyme.

OR… 8. Multi-chambered “ruminant stomach” Divided into 4 compartments Rumen Reticulum Omasum Abomasum

Quick Rumination Video

Cud Chewing Regurgitation of partially-digested feed so that it can be further reduced in size to aid microbial fermentation. The cud, or bolus - carried to the mouth by the esophagus. Must also release the enormous quantities of gas that build up as a result of fermentation. Failure to do so can result in bloating, a severe and potentially fatal condition for a ruminant that can interfere with breathing and cause suffocation.

Interpret

Largest portion of ruminant stomach ( gallons) Functions include: Storage Soaking Physical mixing and breakdown Rumen compartment is quite undeveloped at birth and may be functional by 6 to 8 weeks of age. A. Rumen

A. Rumen (cont.) Balance of chemical AND physical breakdown Walls contain papillae (finger like projections to aid in secretion of enzymes) Contractions occur inside muscular walls 1-3 times per minute. This allows mixing and digestion of fermented feed. When sick or if rumen is too acidic, contractions slow and digestion fails

12 Week Old Calf Rumen