Regulation of body temperature
Excretion and Absorption
Synthesis of Vitamin D
The skin (cutaneous membrane) covers the body and
is the largest organ of the body by surface area and
Its area is about 2 square meters and weighs 4.5-5kg,
about 16% of body weight.
It is 0.5 – 4 mm thick, thinnest on the eyelids, thickest
on the heels.
It consists of two major layers:
Outer, Thinner layer called the Epidermis,
consists of epithelial tissue.
Inner, thicker layer called the Dermis.
Beneath the dermis is a subcutaneous layer
(also called Hypodermis) which attaches the
skin to the underlying tissues and organs.
The epidermis contains five major layers:
oStratum basale-Forms epidermal ridges(fingerprints)
oStratum spinosum-Spiny Layer
oStratum granulosum-Grainy Layer
oStratum lucidum-Clear Layer
oStratum corneum-Horn Layer
The dermis is composed of connective
tissue containing collagen and elastic
Subcutaneous layer (also called
hypodermis) is not part of the skin but,
among its functions, it attaches the skin to
the underlying tissues and organs.
Hair is composed of dead,
keratinized epidermal cells.
Hairs have a number of important
reduction of heat loss
sensing light touch
Nails are composed of hard,
keratinized epidermal cells located
over the dorsal surfaces of the ends of
fingers and toes.
Each nail consists of:
transparent nail body (plate) with
a whitish lunula at its base
nail root embedded in a fold of
Textbook of Human Anatomy and Physiology- Dr. Sushma Devi; Pg 136-
Ross and Wilson Anatomy and Physiology; 13th edition; Pg 30-32