University:
University of Phoenix
Course:
BIO 101T | Principles of Biology 3
Academic year:

2024
Views:

92

Pages:

3
Author:

Graellsew6

Unit-1: Derivatives of Integument The skin of cells is relatively simple, but its derivatives are numerous and complex. Depending on the layer of the skin, it is divided into two categories: Epidermal derivatives Dermal derivatives (a) Epidermal Derivatives: Epidermal Glands: Epidermal glands are derived from the epidermal layer. Hard, horny structures include scales, scutes, beaks, horns, claws, nails, hooves, feathers, and hair. All hard, horny structures together form the exoskeleton of an animal. The major types of epidermal glands are: Mucus gland: Secretes mucus. Poison gland: Secretes poison. Sebaceous gland: Secretes sebum. Scent gland: Secretes scent. Mammary gland: Secretes milk. Femoral gland. Uropygial gland. Epidermal Scales and Scutes: All the hard, horny structures develop from keratin and arise from the cells of the epidermis. These cells are keratinized and become dead. Examples: scales, beaks, horns, claws, nails, hooves, feathers, and hair. (b) Dermal Derivatives: Dermal Scales and Scutes: Bony structures that develop within the dermis and are mesodermal in origin. Types include cosmoid scales, placoid scales, ganoid scales, cycloid scales, and ctenoid scales. Found in fishes and tetrapods. Digital Cornification: Claws, nails, and hooves are built on the same plan. Claws: Curved, horny dorsal plates enclosing the tip of the digit. Nails: Modified claws, developing at the tips of digits. Hoof: U-shaped or V-shaped, e.g., horse shoe. Horns: Found only in hoofed mammals. Present on the skin of the head and help in defense. Five types of horns: True horn Prong horn Antlers horn Bovine horn Hair horn Feathers: Birds are covered by feathers. Light in weight, strong, elastic, and waterproof. Hair: Covers the entire body and is an epidermal product of the integument. Functions of Integument Derivatives: Protects the body from mechanical and chemical injuries. Prevents excessive loss of moisture. Protects against bacteria, fungi, and foreign bodies. Claws, nails, hooves, and horns aid in defense. Feathers help in flight. Excretes salts and urea through sweat. Mammalian skin protects from UV rays.