Basic biology of chicken

Basic Biology of Chicken

1. BASIC BIOLOGY OF CHICKEN Department of Livestock Production Management College of veterinary Sciences &AH Central Agricultural University Selesih : Aizawl : Mizoram Dr.Lakshya J Kakati 2016-V-14(M)

2. SKELETON compact, light in weight , and very strong. only one movable vertebra along its length but vertebrae of neck and tail are moveable. pneumatic bones ,that is hollow and are connected to the respiratory system. Pneumatic bones_: skull , humerus , clavicle , keel , lumbar and sacral vertebae . Medullary bone fills the marrow cavity with fine interlacing spicules of bone . Tibia , femur, pubic bones , sternum , ribs , ulna , toes and scapula.

3. MUSCULAR SYSTEM 3 principle muscle: Smooth muscle Cardiac muscle Skeletal muscle Fibres are thicker In male than female. Dark meat : red fibres White meat : white

4. THE SKIN Chickens have a relatively thin skin over most of the body which is free of secretory gland , the only exception is the uropygial gland or oil gland(preen gland) found on the upper portion of tail . The size and colour of comb and wattles are associated with gonad development and secretion of the sex hormones. Skin color depends on combination of pigments in upper and lower layers of skin.

5. FEATHERS

6. CIRCULATORY SYSTEM Chicks has a four chambered heart ,two atria and two ventricles which allow circulation to the lung . Chicken blood contains from about 2.5 to 3.5 million red blood cells per cubic mm depending on sex and age. Adult males contains about 500,000 more red blood cells per cubic mm. Spleen : red and white cells may be formed , and which act as reservoir of red blood cells.

7. RESPIRATORY SYSTEM Lungs : are rigid structures which expand and contract during respiration. Air sac : 4 pairs. Voice of fowl in syrinx. No alveoli Parabronchi present

8. t Air enters during inhalation through nares(heated n filtered) trachea bronchi( primary bronchi or mesobronchi ) posterior sac at the caudal end of the bird anterior sac parabronchi trachea back out through the birds mouth or nares by expiration.

9. EXCRETORY SYSTEM

10. NERVOUS SYSTEM The prime elements of nervous system integrates the functions of the body. The nervous system is divided into two parts : CNS: voluntary actions of the body. ANS: coordination of involuntary actions of intestines , blood vessels and glands. Neo cortex or cerebral cortex : small Optic lobes of brain : well developed Hearing : well developed . Smell : not highly developed.

11. DIGESTIVE SYSTEM The chicken has simple digestive system , with few or no microorganism living in the digestive system to help digest . It usually take about 2.5 hrs for food to pass through digestive tract. BEAK : of the bird replaces the mouth and lips. CROP : is a pouch formed to serve as storage area . PROVENTRICULUS : is the true stomach . Gizzard : oval organ composed of two pairs of thick red muscles. These muscles are extremely strong and are used to grind the food particles..

12. PANCREAS : secrete pancreatic juice. LIVER : bile is produced in the liver which is necessary for proper absorption of fat. SMALL INTESTINE : The digestion and absorption of food . CECA : some digestion of fibre may take place in the caeca by action of microorganism. RECTUM AND CLOACA : The large intestine is short and consist of a short rectum leading to cloaca.The cloaca is common passage for digestive, urinary and reproductive passages which opens externally at vent.

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14. REPRODUCTIVE SYSTEM FEMALE OVARIES :A Laying hen contain 5-6 large yellow developing egg yolks(follicles) . THE OVIDUCT :divided into 5 regions : Infundibulum , Magnum where thick albumen is secreted , Isthmus which secretes the shell membrane , Uterus or shell gland and , the Vagina the passage to the cloaca. Yolk formation : A yolk is produced by the hen ovary in a process called ovulation. The whole ovulation takes 25 hrs. A Yolk is produced by the hen ovay in a process called ovulation.

15. The process of egg formation strat by one yolk getting the major amount of yolk material produced in liver and transported to ovary.; v.j ,/ Egg white formation : Magnum secrete albumen. Four distinct layers of albumen are the chalaziferous layer attached to the yolk ; inner thin albumen ; thick albumen ; and outer thin albumen . Shell Membrane formation : added to egg in the isthmus . These membranes are made up of many interlacing fibres . The membranes adhere to each other except at large end of the egg to form air cell. Egg shell :Uterus shell is formed , 19-20 hrs is required. It is made of calcium carbonate. The final layer of shell is known as cuticle.

16. Contd … MALE Testes : two bean shaped yellowish white bodies . Left is usually larger than right testes. Testes never descend into an external scrotum. Ductus epidymis is also very short . In avian species sperms are stored mainly in the distal part of ductus deferens . The accessory reproductive organs like seminal vesicles, prostate , cowper’s gland and urethral glands are absent in cocks.

17. Contd … Each testes give rise to a relatively short epididymis , through which the spermatozoa pass to a long coied duct , the ductus deferens. The ductus deferens opens directly over the grove in rudimentary copulatory organ situated in the cloaca.

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