Musculo-Skeletal System of Fowls | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

Anatomy of a Fowl: Musculo-Skeletal System

Overview

The musculo-skeletal system in a fowl, which includes its muscles and bones, plays a crucial role in its normal functioning and overall health.

Distinct Features of Birds

• Birds, like fowls, are unique creatures known for their agility and adaptation for flight.
• Their defining characteristic is the presence of feathers, setting them apart from other animals.

Bird Characteristics

• Birds are warm-blooded, meaning they can regulate their body temperature internally.
• They have a high metabolic rate, indicating how fast their bodies use energy.
• Unlike some animals, the development of young birds occurs outside the mother's body.

Fowl Body Temperature

• The fowl's body temperature is higher compared to other domestic animals.
• Average noon temperature is 107.5°F, varying from 105°F to 109.5°F during the day.
• Notable temperature differences in other poultry species: Duck 108°F, Goose 105°F, Turkey 106°F, Guinea Fowl 107°F, and Pigeon 100°F.

Simplified Summary

• Birds, including fowls, are unique due to their feathered covering and ability to regulate body temperature.
• They have a faster metabolism and young ones develop outside the mother's body.
• Fowls maintain a higher body temperature compared to other domestic birds.
• Understanding the musculo-skeletal system is crucial for their health and well-being.

JAS (M) Fowl Respiratory System

• Fowls are rapid breathers, with a high pilae-rate.
• At rest, they have 14-22 respirations per minute and a heart rate of about 300.
• Excitement can lead to a rapid acceleration in the heart rate.

Feathers

• Feathers are epidermal structures embedded in skin follicles, varying in size, color, and shape.
• They protect birds from physical injury and help in maintaining body warmth.
• Different types of feathers include plumales, filoplumes, and contour feathers.
• Contour feathers, found on the body, wings, and tail, play essential roles in flight and body protection.
• A typical feather has a quill (mainstem), barbs, barbules, and barbicels with fine hooks for a smooth appearance.

Feather Facts

• Large feathers on wings and tail are definite in number and molted and replaced in a regular order.
• This molting pattern is used to judge fowls for egg production, estimating their time out of production.

Fowl Skin

• Fowl skin is relatively thin, consisting of an outer layer (epidermis) and an internal layer (dermis).
• Epidermis in feather-covered areas is dry, covered with fine scales constantly shedding and replacing.
• No sweat glands in fowl skin except for the uropygial or preen gland at the tail base.

Skin Modifications

• Scales on shanks, feet, toe nails, beak, and feathers are epidermal modifications.
• Comb, wattles, and ear lobes are developments of the dermis.

Skin Sensitivity and Movement

• Fowl skin is sensitive to touch stimuli applied to feathers.
• Numerous erector, depressor, and retractor muscles provide feathers with considerable movement.

Muscle Types in Fowl

Three types of muscles: 

1. Involuntary or smooth muscles,
2. Voluntary or striated muscles, and
3. Heart or cardiac muscle.

Muscles in Fowls

• Involuntary muscles are found in the walls of the alimentary canal, blood vessels, and tubular structures.
• Voluntary or striated muscles make up the edible portion of the fowl, crucial for moving the skeleton.
• Cardiac muscle, though involuntary, shares characteristics with striated muscle.

Wing Muscles

• Large muscles control major wing movements, primarily attached to the sternum.
• These wing muscles in the body weigh as much as all other muscles combined, about one-twelfth of the total body weight.
• Reflex nature of perching: Toes automatically flex when the tarsal joint is bent, helping the fowl grasp perches effortlessly.

Diaphragm in Fowls

• The diaphragm, though rudimentary, consists of two parts:
• A tendinous sheet attached to the sternum, 6th and 7th ribs, and 6th thoracic vertebra.
• A pulmonary diaphragm as a horizontal sheet dividing the thoracic cavity into upper and lower sections.

Skeleton in Fowls

• Compact, light, and strong, with many hollow bones for reduced weight.
• Fusion of bones creates strong structures where large flight muscles attach.
• Divided into Axial (skull, vertebral column, ribs, sternum) and Appendicular (wings, legs, supporting structures).

Differences in Vertebral Column

• Neck part is long and movable, while the rest is rigid with fused bones.
• Thoracic vertebrae fuse for wing attachment, extensive fusion in lumbar and sacral regions.
• Hip bone is fixed for strength, adapting for laying relatively large eggs.
• Pubic bones are thin strips, well-spread in a laying hen for egg-laying changes.

Overall Adaptations

• Fowl skeleton is adapted for flight, strength, and the unique demands of egg-laying.
• Hollow and fused bones contribute to lightweight yet robust skeletal structures.