Anatomy & physiology of integumentary system

Anatomy & Physiology Of
Integumentary System
By:
Mr. M. Shivananda Reddy

Structure Of Skin
• The integumentary system is the largest body organ
and is composed of the skin, hair, nails, and glands.
• The skin is further divided into three layers:
a) Epidermis
b) Dermis And
c) Subcutaneous tissue

Epidermis
• The epidermis, the thin avascular superficial layer of the
skin, is made up of an outer dead cornified portion that
serves as a protective barrier and a deeper, living portion
that folds into the dermis.
• Together these layers measure 0.05 to 0.1 mm in thickness.
• The epidermis regenerates with new cells every 28 days.

Layers of Epidermis:
Layers (from deep to superficial):
• Stratum basale or germinatum – single row of cells
attached to dermis; youngest cells
• Stratum spinosum – Made up of bundles of protein resist
tension
• Stratum granulosum – layers of flattened keratinocytes
producing keratin.
• Stratum lucidum layer that is present only on palms and
soles
• Stratum corneum – horny cornified superficial layer

Cells of Epidermis:
• The two major types of epidermal cells are
melanocytes (5%) and keratinocytes (90%).
• Melanocytes are contained in the deep, basal layer
(stratum germinativum) of the epidermis.
• They contain melanin, a pigment that gives color
to the skin and hair and protects the body from
damaging ultraviolet (UV) sunlight.

• Sunlight and hormones stimulate the
melanosome (within the melanocyte) to
increase the production of melanin.
• The wide range of skin color is caused by the
amount of melanin produced; more melanin
results in darker skin color.

• Keratinocytes are synthesized from epidermal
cells in the basal layer.
• As they mature (keratinize), they move to the
surface, where they flatten and die to form the
outer skin layer (stratum corneum).
• Keratinocytes produce a fibrous protein, keratin,
which is vital to the skin’s protective barrier
function.

Dermis
• The dermis is the connective tissue below the
epidermis.
• Dermal thickness varies from 1 to 4 mm. The
dermis is very vascular.

• The dermis is divided into two layers, an
upper thin papillary layer and a deeper,
thicker reticular layer.
• The papillary layer is folded into ridges which
extend into the upper epidermal layer.
• These exposed surface ridges form congenital
patterns called fingerprints and footprints.

Subcutaneous Tissue.
• The subcutaneous tissue lies below the dermis
and is not part of the skin.
• The subcutaneous tissue is often discussed with
the skin because it attaches the skin to
underlying tissues such as muscle and bone.
• The subcutaneous tissue contains loose
connective tissue and fat cells that provide
insulation.

• This layer also stores lipids, regulates
temperature, and provides shock absorption.

Skin Appendages
Appendages of the skin include:
• Hair
• Nails
• Glands (Sebaceous, Apocrine, And Eccrine).

Hair
• Grows on most of the body except for the lips, the
palms of the hands, and the soles of the feet
• The color of the hair is a result of heredity and is
determined by the type and amount of melanin in the
hair shaft.
• Hair grows approximately 1 cm per month.
• On average 100 hairs are lost each day.
• When lost hair is not replaced, baldness results.

Nails:
• Nails grow from the matrix.
• The nail matrix is located at the proximal area of the
nail plate.
• The matrix is commonly called the lunula, which is
the white crescent-shaped area visible through the
nail plate.
• The nail bed that is under the nail matrix and nail
plate is normally pink and contains blood vessels.

• Fingernails grow at a rate of 0.7 to 0.84 mm
per week, with toenail growth 30% to 50%
slower.

Glands:
• Two major types of glands are associated with the skin:
Sebaceous and Sweat (apocrine and eccrine) glands.
• The sebaceous glands secrete sebum, which is emptied
into the hair follicles.
• Sebum prevents the skin and hair from becoming dry.
• Sebum is somewhat bacteriostatic and fungistatic and
consists mainly of lipids.

• These glands depend on sex hormones, particularly
testosterone, to regulate sebum secretion and
production.
• Sebum secretion varies according to sex hormone
levels.
• Sebaceous glands are present on all areas of the
skin except the palms and the soles.
• These glands are most abundant on the face, scalp,
upper chest, and back.

• The apocrine sweat glands are located in the
axillae, breast areolae, umbilical and
anogenital areas, external auditory canals,
and eyelids.

• The eccrine sweat glands are widely
distributed over the body, except in a few
areas, such as the lips.

Functions of Integumentary System
• Regulates body temperature
– regulates heat loss
• Helps regulate fluid balance
– absorbs water
– prevents excessive water & electrolyte loss.
– Slow loss up to 600 ml daily by evaporation
• Immune Response Function

• Vitamin production
– exposure to UV light allows for the conversion of
substances necessary for synthesizing vitamin D
– Necessary to prevent osteoporosis, rickets
• Excretion:
Partial excretion of metabolic wastes occurs
through the skin.

• Transmits sensation – nerve receptors
• allows for feelings of temperature, pain, light
touch and pressure

Functions of hair:
Head:
o UV protection
o Cushion from trauma
o Insulation
Nostrils, Ear canals, Eyelashes:
• Prevent entry of foreign material
Body Hair:
• sensory detection

Anatomy & physiology of integumentary system

Anatomy &amp; physiology of integumentary system

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