DIGESTIVE SYSTEM

PATH OF DIGESTION Food is grasped and collected into the oral

cavity This is called prehension

Mastication (chewing) breaks food into smaller pieces

Deglutition moves chewed food into the pharynx and on into the esophagus The epiglottis closes off the entrance to the trachea

Food moves down the esophagus by gravity and peristalsis Peristalsis is a series of wavelike contractions of

smooth muscle -stalsis means contraction

PERISTALSIS VERSUS SEGMENTATION Food moves through

the small intestines by peristalsis and segmentation

Peristalsis is a series of wavelike contractions that move ingesta caudally toward the anus

Segmentation involves the side-to- side mixing of ingesta

STRUCTURES AND FUNCTIONS

• The organs of the gastrointestinal tract (GI) form a tubelike passage through the body cavaties.– From the mouth to the anus by way of the

pharynx, esophagus, stomach, and intestines

• The main functions of this system is – Prehension– Transport– Breakdown of food– Absorption of nutrients– Eliminate waste

STRUCTURES AND FUNCTIONS

• Food moves through the digestive system aided by peristalsis, an involuntary, wavelike movement.

• The digestive tract in all mammals generally has the same parts– Mouth– Teeth– Tongue– Pharynx– Esophagus– Stomach– Small intestine– Large intestine

THE MOUTH

Lips form the entrance to the mouth. The lips of sheep, goats, and horses are soft and flexiable and aid in picking up food.

Lips of cattle and swine are stiff and immobile and do little more than close the mouth.

TEETH

• The number of deciduous (baby teeth) and permanent teeth vary with the species and the natural diet of an animal.

• Teeth provide a variety of functions– Cutting and grinding of food– Defense mechanism

• Ruminants do not have upper incisors, just a pad.

SALIVARY GLANDS

Saliva is produced in 4 salivary glands Parotid Sublingual Mandibular Zygomatic

Referred to as exocrine glands

Saliva begins the breakdown of some foods (carbohydrates) in the mouth.

Moistens food, lubricant for the bolus.

DIGESTION Digestion is the process of breaking down

foods into nutrients that the body can use Metabolism is the processes involved in the

body’s use of nutrients Meta- means change or beyond Anabolism is building up of body cells Catabolism is breakdown of body cells

ABSORPTION

Absorption is the process of taking digested nutrients into the circulatory systemalso called assimilation

Absorption occurs in the small intestineVilli are tiny hairlike projections that help

increase the surface area of the small intestine allowing more nutrients to be absorbed Vill/i means tuft of hair

The valleys that result from the projections of the small intestine are called crypts

DIGESTIVE SYSTEMS

Man and pig have a simple stomach with an extensive intestinal system

Ruminants have a complex stomach with a simpler intestinal system

Horses and rabbits have a simple stomach with an extensive intestinal system and an enlarged cecum

3 MAJOR DIGESTIVE SYSTEMS

All 3 systems will be addressed in detail in the lesson to follow:

Ruminants—have four stomach compartments

Monogastric—have one stomach Modified Monogastric—have one

stomach but the ability to digest roughages

Ruminant Digestive System

DIGESTIVE SYSTEM

Small Intestine: long coiled tube connecting stomach to large intestine rest of the digestion and absorption takes place here surface covered with villi (surface area)

3.5 times the length of animal – dog 18’

Large Intestine: Cecum, colon, rectum absorbs water (makes feces more solid) some vitamins and minerals absorbed here Cecal Fermenters (Horse): similar to rumen

DIGESTIVE SYSTEM

Accessory organs: Pancreas secretes enzymes to break down fat Liver (largest internal organ) secretes bile,

which digests fats also stores iron

DIGESTIVE SYSTEMS Man and pig have a ________stomach with an

extensive intestinal system Ruminants have a ___________ stomach with a

simpler intestinal system Horses and rabbits have a simple stomach

with an extensive intestinal system and an enlarged__________

DIGESTIVE SYSTEM Mouth: “Prehension” tool (grasps food)

___________________secrete juices containing enzymes (digest food)

Chewing food breaks down ____________: muscular tube that connects

mouth to stomach Peristaltic Movement: sequential contraction of ring

like___________ Reverse ___________= blowing chunks

SIMPLE STOMACH

Muscular contractions break down food Enzymes break down food:

Gastric: ___________ Liver and ____________: fats

Ruminant Digestive System

Ruminant Facts (Bovine) Chews cud

40,000-60,000 jaw movements/day

No upper incisors - dental pad

Does not “bite” grass - wraps tongue

Uses fermentation to digest plants

Symbiotic relationship with bacteria

Produces 13 gallons of gas/hour

Produces 40 liters of saliva/day

I thought Dumbo was an elephant

RUMINANT STOMACH Stomach occupies 3/4 of abdominal cavity,

mostly on the left side Rumen (paunch): 80% of stomach, lighter food

collects here microbes digest cellulose lots of water

Reticulum (hardware stomach): 5% of stomach, heavy foreign items are trapped here

RUMINANT STOMACH

Omasum (many plies): 8% of stomach, absorbs water

Abomasum (true stomach): 8% of stomach, typical enzyme activity

Rumination: regurgitation, rechewing of food

Rumen Largest compartment On left side of animal Contains micro-organisms Ferments cellulose Absorbs VFA’s Divided into chambers Continually contracting Contains papillae Produces CO2

pH close to neutral (6 - 7)

Reticulum Smallest compartment

Lies close to the heart

Small sac - part of rumen body

Catches dense, heavy feed for later rumination

Contracts for regurgitation

“Honeycomb” lining

Catches hardware and stores it

Omasum

Third compartment

Globe-shaped

Lining called “many plies”

Reduces feed particle size

Absorbs water and dries out ingesta

Absorbs volatile fatty acids

Abomasum Final compartment

Tubular in design

“True” stomach (glandular)

Secretes HCl and enzymes for chemical digestion

Reduces pH to 2.5 Dissolves minerals Kills rumen bacteria Breaks down proteins

Passes ingesta to small intestine

Ruminant Digestion

Ruminant Digestion Intake

Mastication (chewing)

Swallowing

Regurgitation

Remastication

Fermentation

Eructation

Absorption

Digestion

Rumination

Fermentation Anaerobic bacteria

break down cellulose

VFA’s released by bacteria passed to

bloodstream through papillae

CO2 and CH4 produced by bacteria

Bacteria controlled by protozoa

Ingesta passed to omasum by

contractions

DIGESTIVE SYSTEM Converts feed into a form that can be used for

maintenance, growth, and reproduction In a light horse, the tract is approximately 100

feet long and capacity of 40-50 gallons. Includes:

Mouth, esophagus, stomach, intestines, anus, liver, teeth, pancreas, and salivary glands

EQUINE DIGESTIVE SYSTEM Mouth

Lips, pharynx, soft palate Lips pick up loose feed which is then passed into

the mouth by the tongue Pharynx

Short, funnel shaped tube between the mouth and the esophagus Food and water cannot return through the mouth after

passing through Horse that chokes has food pass through nose

DIGESTIVE SYSTEM

Esophagus is a long muscular tube from the pharynx to the stomach.

Stomach is a U shaped muscular sac Peristalsis moves food through Gastric juices are expressed by the stomach

walls.

HORSE DIGESTIVE SYSTEM

1. Esophagus 5. Large intestine (80 quarts)

2. Stomach (8-16 quarts) 6. Pelvic flexure

3. Small intestine (48 quarts) 7. Colon

4. Cecum (28-32 quarts) 8. Rectum

LARGE INTESTINE, HORSES The large intestine makes up

approximately 60% of the total digestive tract.

Divided into cecum, large colon, small colon and rectum.

Cecum is an important organ in horses.Horses can use large amounts of

roughage because of the presence of bacteria in the cecum and colon.

These bacteria digest cellulose and ferment carbohydrates.

LARGE INTESTINE, HORSES IMPORTANT- because the large intestine of

the horse usually contains substantial quantities of ingested material, impaction occurs easily.

This impaction is the start of what horse ailment?

Signs and symptoms Kicking at abdomen, rolling, lying down and

standing up repeatedly, restlessness .