Anatomy and Physiology of Poultry

Anatomy and Physiology of Poultry

Introduction :

An understanding of the anatomy and physiology of birds, and the different body systems found in the bird, is useful when an understanding of how poultry work or function. Knowledge of bird anatomy (body parts) and physiology (body function) enables the poultry industry to maximise bird performance and maintain good welfare practices. Like humans, birds eat, grow, breathe, reproduce, empty out wastes and move about. Both need food, water and air, and must protect themselves from changes in the environment.

Anatomical Terms
The following terms are used to describe locations on
the animal body.
Dorsal: pertains to the upper surface of the animal.
Ventral: relates to the lower and abdominal surface.
Cranial (or anterior): applies to the front or head.
Caudal (or posterior): pertains to the tail or rear

Integumentary System
The skin, feathers, and beak.
Function: to protect the bird from external harm.
Skin
Much like humans, with the exception of plumage production.
Plumage: the outer covering of a bird’s body.
Feathers, scales, filoplumes.
Filoplumes: hair-like structures located at the base of feathers.
Wattle: a red growth underneath the beak, which works in
conjunction with the comb, an excess of skin on top of their head.
Function: circulation of blood between the two regulate the temperature
of the bird.
The size of the comb is an indication of the levels of testosterone in the
body. If the comb is large, then this means more testosterone is present,
often meaning the sex of the bird is male.

Scales and Plumage
Scales are located on the legs and feet.
The plumage is always for altered shape.
Function: body cooling and heating for maintenance of
body temperature, protects against abrasions and bruises
when birds are in groups or lying on the ground.
Plumage shape is particularly important for cooling since
birds lack sweat glands.
Although it is not common for production birds to fly,
plumage type and form is an important determinant in
flight for aerial species.

Respiratory System
Vastly different than the mammalian respiratory
system.
Unlike mammals, birds lack a diaphragm to inflate
and deflate the lungs.
Instead, birds have nine air sacs located in the neck
region and body cavity that function to inflate the lungs.
Gas exchange occurs in the Avian lung and the air sacs
function to move air in and out of the respiratory system.

Breathing process has two phases: inhalation and
exhalation.
Inhalation: when the bird breathes in, air bypasses the lungs
and enters the posterior air sacs. At the same time, air in the
lungs from the last exhalation phase exits the lungs and
enters the anterior air sacs.
Exhalation: the bird releases air from the posterior air sacs,
which enters the lungs. The air that filled the anterior air sacs
from the inhalation phase is then released from the body
through the trachea.
Nares are the nostrils located on the beak. Their
purpose is the passageway for air to be breathed in and
out of the trachea.

Skeletal System
1. Pneumatic Bones
Poultry have pneumatic, or hollow, bones.
Connect with the respiratory system.
Their light weight is an adaptation for flight.
2. Medullary Bone
Medullary bone contains high amounts of calcium.
Storage source is used by the female hen to produce the egg shell
during reproductive periods.
3. Fused Bones
Bones in the foot, or shank, are fused.
Cause birds to walk upright.
Many vertebrate along the backbone are fused for the purpose of
flight.

The Poultry Digestive System
Instead of asking “Why did the chicken cross the road?” poultry hobbyists may better ask, “How does the chicken chew its feed without any teeth?” Even without teeth, chickens have one of the most efficient digestive systems in the animal kingdom. Let’s take a look at how the poultry digestive system works.

Food is taken in with the beak, which is the perfect tool for pecking feed in crumble or pellet form, small grains, grass or insects. Chickens are omnivores – meaning that, in addition to a commercial feed, they can eat meat (grubs, worms, the occasional mouse) and vegetation (grass, weeds and other plants). A small bit of saliva and digestive enzymes are added as the food moves from the mouth into the esophagus.

From the esophagus food moves to the crop, an expandable storage compartment located at the base of the chicken’s neck, where it can remain for up to 12 hours. The food trickles from the crop into the bird’s stomach (proventriculus or gizzard) where digestive enzymes are added to the mix and physical grinding of the food occurs.

The gizzard is why chickens do not need teeth. It is a muscular part of the stomach and uses grit (small, hard particles of pebbles or sand) to grind grains and fiber into smaller, more digestible, particles.

From the gizzard, food passes into the small intestine, where nutrients are absorbed. The residue then passes through the ceca, a blind sack along the lower intestinal tract, where bacteria help break down undigested food. From the ceca, food moves to the large intestine, which absorbs water and dries out indigestible foods.

This remaining residue passes through the cloaca where the chicken’s urine (the white in chicken droppings) mixes with the waste. Both exit the chicken at the vent, the external opening of the cloaca.

And don’t think of chicken manure as “waste” to be disposed of…it makes a great fertilizer for your flower beds or vegetable garden. Because it is high in nitrogen, it is recommended to let it age for a bit in a compost pile before adding it to your gardens.

A quick tour of the digestive system:
Mouth: It all starts here.
Esophagus (Gullet): Transports food from the mouth to the stomach.
Crop: A pouch in the esophagus used to store food temporarily before moving it on to the stomach.
Stomach (Proventriculus/Gizzard): Principally the organ where food is broken into smaller units. It has two parts: the proventriculus for storage and the gizzard. The gizzard is a muscular part of the stomach that uses grit to grind grains and fiber into smaller particles.
Small Intestine: Aids in digestion and nutrient absorption. Composed of the duodenum, jejunum and ileum.
Liver: The largest glandular organ in the body. Aids in the metabolism of carbohydrates, fats and proteins.
Ceca: Bacterial action in the ceca helps break down undigested food passing through the intestine. The ceca turns into the large intestine, which connects with the  cloaca.
Large Intestine: Functions primarily to absorb water, dry out indigestible foods and eliminate waste products.
Cloaca: Where the digestive, urinary and reproductive systems meet.
Urinary System: Consists of two kidneys and two ureters. The kidneys are located in the pelvic bones. They filter waste from the blood and pass it through the ureter to the outside via the cloaca/vent.
Vent: The external opening of the cloaca that passes waste to the outside.