Upload
rosalyn-mcgee
View
224
Download
0
Tags:
Embed Size (px)
Citation preview
The Digestive System
Functions
• Ingestion (eating)
• Grinding
• Digestion
• Absorption of nutrients
• Elimination of solid wastes
Introduction
• Digestive system changes food nutrients into compounds easily absorbed by the body
• Nutrients are used for:– Energy, growth and maintenance
Definitions
• Herbivores– Depend entirely on plants for food source– Ex. Cattle, sheep, horses, rabbits
• Carnivores– Depend primarily on flesh of other animals– Ex. Dogs and cats
• Omnivores– Consume both flesh and plants– Ex. Swine, poultry, humans
Digestive Tract
• Extends from the lips to the anus
• Length of digestive tract depends upon the specie– Carnivores is usually short, herbivores is long
• Simple and complex stomachs
Mouth
• Primary functions– Prehension
• Grasping of food
– Grinding of feed– Mixing feed and saliva
Teeth
• Responsible for grinding
• Incisors are used for cutting food
• Premolars and molars are responsible for grinding
• Milk teeth– Lost and replaced by permanent teeth
Tongue
• Used in prehension
• Aids in chewing process
• Mass of muscles covered by a membrane
• Covered with papillae which contain the taste buds
Lips
• Horses and sheep– Used in grasping feed– Used in sorting through feed
• Swine and cattle– Keep mouth closed
Other Mouth Parts
• Cheeks– Lines food up with the teeth
• Jaw – Lined with powerful muscles that aid in
chewing
• Hard Palate– Roof of the mouth
• Soft Palate– Divides pharynx and oral cavity
Salivary Glands
• Common in the mucous lining of the mouth
• Except for:– Tongue– Hard palate– Gums
Pharynx
• Common passageway for air and food
• Several structures open into pharynx:– Mouth, nasal cavity, Eustachian tubes, larynx,
and esophagus
• Pushes food into the esophagus
Esophagus
• Connects the pharynx to the stomach
• Walls have two layers of muscles– Muscles run at right angles to each other
Non-Ruminant Stomach
• Consist of only one compartment
• Called the ‘true stomach”
• On the left side of the body
• High surface area due to folding
• Gastric glands produce:– Hydrochloric acid– Enzymes:
• Pepsin and rennin
Ruminant Stomach
• 4 parts:– Rumen, reticulum, omasum, abomasum
• 1st three parts contain no glands, they soak food and allow for microbial digestion
• Reticulum– Forward most portion– Honeycomb-like
Ruminant Stomach
• Rumen– Fills most of the left side of the abdomen– 2 parts: dorsal and ventral– Consist of two layers of smooth muscle– Mature ruminants: rumen accounts for 80% of
the total stomach
Ruminant Stomach
• Omasum– Round in shape– Contains many small papillae which grind
roughage
• Abomasum– Only glandular stomach– Similar to a non-ruminant stomach
Small Intestine
• 3 parts:– Duodenum
• Digestive juices from pancreas and liver
– Jejunum– Ileum
Large Intestine
• Consists of:– Cecum
• Shaped like a comma• Varies drastically in size across species
– Horses and rabbits have largest ceca
– Blind pouch– Colon– Anus
Poultry Digestive System
• Don’t have teeth
• Crop– Stores and softens food
• Gizzard– Grinds food– Contains grit and gravel
• Proventriculus– Glandular stomach
Pancreas
• Exocrine functions– Produces digestive
juices
• Endocrine– Produces insulin
Liver
• On the right side of the body
• Purifies blood
Gallbladder
• Attached to the liver• Produces bile• Green organ