Body wall of a Bird :
The body wall of birds has three regions, Skin, Muscles and Perito­neum.
1) The skin is dry. It shows upper stratum corneum, which has flat cornified cells. The feathers cover the body. Dermis shows musculo-fibrous tissue. The muscles help to raise and lower the feathers. It is supplied with blood vessels and nerve fibres.
2) Glands are absent in the skin of a bird except preen gland which is located on the upper surface of the tail. Its secretions keep the feathers water proof.
3) Muscles: Below the skin Muscles are present. In birds skeletal muscles are well developed. The flight muscles are well developed which help to raise and lower the wing.
4) Peritoneum : A thin epithelium called peritoneum will cover the inner surface of the muscles.
5) In birds skin sweat glands are absent and hence bird cools itself in hot environment by panting.