What is the structure of the skin and its accessory organs, and what are their functions?
Skin is the largest organ in the human body. It encloses most of our body structure with particular function such as protecting the body from certain harm, sense of touch, thermoregulator, controls the evaporation of fluids, specifically water, to avoid massive dehydration of the body, stores lipids and fats that can be used as reserved form of energy, excretion of body fluids and a lot more. Human skin has layers and parts of different structures and functions.
Epidermis - the outermost part of the skin; the waterproof part of the skin that limits the entrance of water inside the body. It also serves as a barrier to certain infections and diseases. This is the part of the skin that wears off and can be replaced by new growing skin cells.
Dermis - the second layer of the skin; contains connective tissues with embedded structures such as hair follicles, apocrine glands, blood vessels, glands and lymphatic vessels.
Glands - The glands that are part of the skin are the sweat glands, sebaceous glands and the apocrine sweat glands. Sweat glands produce sweats that are excreted through the sweat pores with the opening in the epidermis. Sebaceous glands produce sebum that lubricates and increase the waterproof ability of the skin.
Hypodermis - The third layer, hypodermis, is not actually a part of the skin but it serves as a connector of dermis from the muscle tissues and bones.
Mammalian skin is characterized by having various glands and hairs in abundance. T.S. through skin shows that it is an organ consisting of an ectodermal epithelium, the epidermis, and supporting mesodermal connective tissue, the dermis.
Epidermis constitutes the investing cellular membrane of the organisms. It is a stratified squamous epithelium which represents peculiar metabolic end product in the form of fibrous protein, keratin. The epidermis consists of the following layers like stratum corneum, stratum lucidum, stratum granulosum and stratum malpighi.
Hairs are characteristic of mammalian skin only. Each hair is an elongated structure consisting of hair shaft, hair follicle, hair cuticle, hair cortex, hair medulla, hair bulb and hair papilla.
Beneath epidermis is dermis. It is formed of areolar connective tissue. It originates from dermatome and contains collagen fibres, elastic fibres, histocytes, fibrocytes and mast cells. Dermis contains various glands such as sebaceous glands, sweat glands, mammary glands and meibomian glands.
Lal, S.S. (1995). A Textbook of Practical Zoology Vertebrate.