SKIN ANATOMY

ANATOMY OF INTEGUMENTARY SYSTEM

Prepared by: Mr.Maulik chaudhary

Contents

• 1) Structure of the skin

• 2) Functions of the skin

• 3) Wound healing

Function of skin

• protects the underlying structures from injury and from invasion by microbes

• contains sensory nerve endings that enable discrimination of pain, temperature and touch

• is involved in the regulation of body temperature.

Structure of the skin

• The skin is the largest organ in the body and has a surface area of about 1.5–2 m2 in adults.

• In certain areas, it contains accessory structures: glands, hair and nails.

• Anatomy of skin layers:

• 1) epidermis = is the thinner outer covering

• 2) dermis= is the thicker middle layer of the skin

composed connective tissues.

• 3) subcutaneous layer = composed of areolar tissue and adipose (fat) tissue.

Epidermis

• The epidermis is the outer and thinner region of the skin.

• It is made up of stratified squamous epithelium divided into several layers;

the deepest layer is the stratum basale (germinative layer)

the most superficial layer is the stratum corneum.

• It varies in thickness, being thickest on the palms of the hands and soles of the feet.

• There are several layers (strata) of cells in the epidermis which extend from the deepest germinative layer to the most superficial stratum corneum (a thick horny layer)

• Epidermal cells originate in the germinative layer and undergo gradual change as they progress towards the skin surface.

• cytoplasm has been replaced by the fibrous protein= keratin.

• Complete replacement of the epidermis takes about a month.

Healthy epidermis depends upon three processes being synchronised:

1) desquamation (shedding) of the keratinised cells from the surface

2) effective keratinisation of cells approaching the surface

3) continual cell division in the deeper layers with newly formed cells being pushed upwards to the surface.

• Skin colour is affected by various factors.

• Melanin, a dark pigment derived from the amino acid tyrosine and secreted by melanocytes in the deep germinative layer,

• is absorbed by surrounding epithelial cells. The amount is genetically determined and varies between different parts of the body,

Dermis

• The dermis, is a deeper and thicker region than the epidermis, is composed of dense irregular connective tissue.

• The upper layer of the dermis has fingerlike projections called dermal papillae.

• Dermal papillae project into and anchor the epidermis.

• In the overlying epidermis,dermal papillae cause ridges, resulting in spiral pattern commonly known as “fingerprints’.

• The function of the epidermal ridges is to Increase friction to provide a better ‘grip’.

• Because they are unique to each person, fingerprint and footprints can be used for identification purposes.

The dermis layer contains following:

• blood and lymph vessels

• sensory nerve endings

• sweat glands and their ducts

• hairs, arrector pili muscles and sebaceous glands.

Blood and lymph vessels.

• Arterioles form a fine network with capillary branches supplying sweat glands, sebaceous glands, hair follicles and the dermis. Lymph vessels form a network throughout the dermis.

Sensory nerve endings.

• Sensory receptors (specialised nerve endings) sensitive to touch, temperature, pressure and pain are widely distributed in the dermis.

The Appendages of the Skin:

The appendages of the skin are:

1) the nails

2) the hairs

3) the sweat glands

4) sebaceous glands with their ducts.

• A sweat gland is tubular. The tubule is coiled, particularly at its origin within the dermis.

• These glands become active when a person is under stress.

Two types of sweat glands are present:

1) Apocrine

2) Eccrine

• Apocrine glands open into hair follicles in the anal

region, groin, and armpits. These glands begin to secrete at puberty.

Sweat Glands

• Eccrine glands open onto the surface of the skin.

• They become active when a person is hot, helping to lower body temperature as sweat evaporates.

• Therefore, sweat is a form of excretion. Ears contain modified sweat glands, called Ceruminous glands, which produce cerumen (earwax).

Hairs

• These grow from hair follicles, downgrowths of epidermal cells into the dermis or subcutaneous tissue.

• At the base of the follicle is a cluster of cells called the hair papilla or bulb.

Sebaceous glands

• These consist of secretory epithelial cells derived from the same tissue as the hair follicles.

• They secrete an oily antimicrobial substance= sebum, into the hair follicles and are present in the skin of all parts of the body except the palms of the hands and the soles of the feet.

Nails

• Human nails are equivalent to the claws, horns and hooves of animals.

• Derived from the same cells as epidermis and hair these are hard, horny keratin plates that protect the tips of the fingers and toes.

Functions of the Skin

Immunological function

Secretory function

Thermoregulation function

Receptory function

Excretory function

Protective function