tailieunhanh - A practical guide with histology (Second edition): Part 2

(BQ) Continued part 1, part 2 of the document A practical guide with histology (Second edition) has contents: Integumentary system, digestive system, urinary system, male reproductive system, female reproductive system, respiratory system, endocrine glands, special senses. Invite you to refer. | 11 INTEGUMENTARY SYSTEM Introduction Integumentary system includes skin and its appendages namely hair and nail. Skin covers the surface of the body and comes into direct contact with the external environment. It is the single heaviest organ of the body forming one-sixth of the total body weight and its surface area is 18 sft. On close observation the external surface of the skin shows many lines such as tension lines due to anchoring fibrils of dermis flexure lines over joints and friction ridges papillary ridges over palm and sole. The papillary ridges and the intervening sulci on the palm and sole assume a unique configuration for each individual and is used for personal identification. The study of these configurations is called dermatoglyphics finger print which is an upcoming field and of considerable medical anthropological and legal interest. The dry skin becomes continuous with the wet mucous membrane at various orifices seen on the surface of the body viz. mouth nostril anus vulva etc. Functions of Skin Protection Skin gives protection against mechanical trauma invasion of microorganisms evaporation water loss and ultraviolet rays by melanin pigments . Sensory perception Skin is the largest sense organ of the body. It contains many receptors for general sensation pain touch temperature and pressure . Thermoregulation It is mainly performed by glands sweating and also by blood vessels and adipose tissue. Synthesis of vitamin D Epidermis of skin is involved in synthesis of vitamin D from 7-dehydrocholesterol by the action of UV light. Excretion Skin acts as a minor excretory organ for certain catabolic nitrogenous waste products and water. Blood pressure regulation This is done by specialized arteriovenous anastomosis called glomus found in the dermis of the skin. Storage Skin acts as a storehouse for glycogen and cholesterol in the subcutaneous fat. Absorption Skin also absorbs certain lipid soluble substances drugs chemicals which are of therapeutic .