Comparative anatomy( Chordates)

Digestive system 1-Human 2-Ruminant 3-Avian 4-Horse 5-Fish Dr.Omer

Digestive System

Introduction

• Three (3) basic types of digestive systems according to their stomachs :

►Monogastric – simple stomach.►Ruminant (cranial fermentor) – multi-compartmented

stomachs.►Hind gut (caudal) fermentor – simple stomach, but very

large and complex large intestine

Types of Digestive Systems

Cats

Chickens Pigs

DogsTurkeys

Monogastrics Ruminants Hind Gut Fermentors

Beef Cattle Dairy Cattle

Deer

SheepGoats

Horses

Rabbits

Ostrich

Types of Digestive Systems

• Are divided into three groups based on their food sources1. Herbivores are animals that eat plants

exclusively2. Carnivores are animals that eat other animals3. Omnivores are animals that eat both plants and

other animals

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Carnivore• Eat primarily

other animals.

Herbivore• Eat primarily

plant materials.

omnivore• Eat combination

of plant and animal material.

The Human Digestive System

Human

Kingdom AnimaliaPhylum ChordataClass MammaliaOrder PrimatesFamily HominidaeGenus HomoSpecies sapiens

Introduction• The digestive system is used for breaking down food into

nutrients which then pass into the circulatory system and are taken to where they are needed in the body.

Main Functions of Digestive Tract

• The major activities of GI tract• 1-Ingestion: taking in food

2.Motility • Propel ingested food from mouth toward rectum

3.Secretion of juices e.g. saliva • Aid in digestion and absorption

4.Digestion• Food broken down into absorbable molecules

5.Absorption• Nutrients, electrolytes, and water are absorbed or

transported from lumen of GIT to blood stream6.. Egestion (Elimination) : removing any leftover wastes

Digestion• Types– Mechanical (physical)• Chew• Tear• Grind• Mash• Mix

– Chemical• Enzymatic reactions to improve digestion of – Carbohydrates– Proteins– Lipids

Anatomy of the Digestive TractGIT consists of;– Oral cavity or mouth – Pharynx– Esophagus– Stomach– Small intestine– Large intestine– Rectum– Anus

Mouth or oral cavity

• Ingestion - bringing food into the body– tongue - taste buds detect chemical composition of food

• Mastication - chewing (physical digestion)– teeth and tongue

• Chemical digestion - saliva– moistens food– amylase - breaks down starch – lysozyme - antibacterial agent

Mouth and Teeth

Esophagus• Muscular tube connecting the pharynx to the stomach.• Functions include:1. Secretes mucus2. Moves food from the throat to the stomach using

muscle movement called peristalsis Cardiac Sphincter – connects esophagus and stomach• If acid from the stomach gets in here that’s heartburn.

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Stomach • Muscular sac-like organ• Chemical and physical digestion

– forms chyme • goblet cells – mucus

– forms a protective barrier against the high acidity of the stomach content.

– parietal cells – HCl– kills bacteria, denatures proteins

• chief cells - pepsinogen– pepsinogen activated by HCl pepsin – pepsin breaks down proteins

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The Stomach

Small intestine

FunctionsDigestion

Digest carbohydrates : amylase from pancreasDigest proteins : trypsin & chymotrypsin from pancreasDigest lipids (fats) bile from liver & lipase from pancreas

AbsorptionVILLI – small finger-like projections that increase the surface area

MICROVILLI – even smaller finger-like projections on the VILLILACTEAL – large lymph vessel found on each villus (Absorbs FAT)Capillaries – small blood vessels found on each villus (Absorbs all

nutrients EXCEPT Fat)

The Parts of Small intestine

1. Duodenum - most digestion occurs here 2. Jejunum - some digestion and some

absorption occur 3. Ileum - mostly absorption

SMALL INTESTINE

• The small intestine is divided • duodenum • jejunum • ileum.

• Pancreas has 2 functions:a) Endocrine functions: secretes insulin and glucagon

from islets of Langerhans b) Exocrine function: secretion of pancreatic juice• It has 2 components: aqueous and enzymatic

components.• Aqueous component (contains HCO3) is important for

neutralizing stomach acid in the duodenum so pancreatic enzymes can function properly

• Enzymatic component is essential for the proper digestion and absorption of carbohydrates, fats, and proteins

• Pancreatic enzymes include trypsin, chemotrypsin, lipase, and amylase

Functions of the Pancreas

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Liver

Functions of the Liver:1) Metabolic regulation

• Store absorbed nutrients, vitamins• Release nutrients as needed

2) Hematological regulation• Plasma protein production• Remove old RBCs

3) Production of bile• Required for fat digestion and absorption

Liver

Liver

The Large Intestine (colon)

• Much shorter than small intestine, but has larger diameter

Functions1. Goblet cells: create mucus that lubricates colon and

protects mucosa.2. Absortive cells: Maintain water balance, solidify

feces, absorb vitamins and some ions• Prepare waste for expulsion

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Digestive System– Ruminants –

Mouth, esophagus, liver, pancreas, gall bladder, small intestine, and large intestine have functions similar to monogastrics.

Cow

• • Kingdom Animal• Phylum Chordata• Class Mammalia• Order Artiodactyla• Family Bovidae• Genus Bos• Species indicus Asian humped cattle taurus European non-humped cattle

Reticulum

• Holding area for feed after it passes down esophagus.• Provides additional area for fermentation.• Contains microorganisms, like rumen• Collection compartment for foreign objects.• Helps open and close rumen.• Minimal separation with rumen.

“honeycomb”

Rumen

• Largest of the four components.• On the left side of the animal.• Storage site and fermentation .• Houses millions of microorganisms.• Lined with millions of finger-like projections (papillae) that are needed for

absorption.

“paunch”

Omasum

• A heavy, hard organ that has many folds or leaves.• Little, if any digestive activity.• Grinds feed particles.• Removes moisture.

“many piles”

Abomasum

• True, glandular stomach• Functions similarly to monogastric stomach• Secretes gastric juices which aid in digestion.

Infected with barber pole worms

Organs of the Digestive System– Hind Gut Fermentors –

Mouth, esophagus, stomach, liver, pancreas,, and small intestine have similar functions as compared to monogastrics.

Horse doesn’t have gall bladder

Digestive Tract - Horse-

Esophagus

Stomach

Duodenum

Small intestineCecum

Large colon

Small colon

Rectum

Organs of the Digestive System– Hind Gut Fermentors –

• Large Intestine► Major difference between monogastrics and hind gut fermentors is the large

intestine.► Large intestine is exceptionally large and complex compared to monogastrics

and ruminants.

The large intestine of hind gut fermentors is analogous to the rumen in ruminants.► Microbes digest structural carbohydrates (cellulose, hemicellulose) and

soluble carbohydrates that escape digestion in small intestine to VFA’s. VFA’s absorbed from large intestine and utilized by the animal.

► Microbial protein produced in large intestine is wasted (only very limited absorption from large intestine).

Avian Digestive System

Avian Digestive Systems

• Mouth – no teeth – Salivation excretion moistens food

• Esophagus – has a modification called the “crop” which stores

and moistens food– connects mouth and stomach

Avian Digestive Systems

• Stomach– Contains two parts• Proventriculus: same as monogastric stomach and

provides digestive excretions• Gizzard: located after proventriculus, very muscular,

used to grind food

Avian Digestive Systems

• Small Intestine– similar functions as in ruminants and monogastric

systems• Large Intestine– similar functions as in ruminants and monogastric

systems– “cloaca”: chamber into which urinary and genital

canals open– “ceca”: aids in fiber digestion and absorption

Digestive System Comparisons

Function Monogastric Ruminants Hind Gut Fermentors

Digest and extract energy from cellulose

Very limited(large intestine)

Yes(rumen/reticulum)

Yes(large intestine)

Utilize dietary sugar sources directly

Yes(absorbed as

glucose)

No(fermented to VFA’s)

Yes(absorbed as

glucose)

Utilize protein from feeds directly

Yes Limited(most converted to microbial protein)

Yes

Utilize fat from feeds directly

Yes Some(most fermented to VFA’s)

Yes

Utilize microbial protein

No Yes(60-80% of AA from

microbes)

No

Human Cattle Bird Horses Teeth 32 32 0 40-42

Organs of digestive system Comparisons

Ruminant

• Mouth• Esophagus• Stomach

– Reticulum– Rumen– Omasum– Abomasum

• Small intestines• Large intestines

Monogastric

• Mouth• Esophagus• Stomach• Small intestines• Large intestines

LiverPancreas

LiverPancreas

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