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.