Zoology Edition

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to the session on
ANATOMY INTEGUMENTARY SYSTEM
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INTEGUMENTARY SYSTEM
The skin is the largest organ in the body 12-15
of body weight, with a surface area of 1-2
meters. Skin is continuous with, but
structurally distinct from mucous membranes that
line the mouth, anus, urethra, and vagina.
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Skin
Anatomy - Epidermis - Dermis - Hypodermis
Thin skin Thick skin Skin color Skin
Derivatives - Hair - Nails -
Skin glands Functions
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SKIN or INTEGUMENT
Epidermis is made up of Stratified squamous
epithelium. Keratinocyte is the basic cells of
epidermis, which contain keratin, a fibrous
protein. Melanocytes produce the pigment melanin,
and are also in the inner layer of the epidermis.
Comprises two distinct layers occur in the skin
the dermis and epidermis, both layers rests over
the hypodermis
Dermis is a connective tissue layer under the
epidermis, and contains fibroplasts, adipose
cells, nerve endings, sensory receptors,
capillaries, and macrophages.
Hypodermis It attaches the skin to the
underlying bones and muscles. It supplies the
blood vessels and nerve to the skin
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During the keratinization epidermis divided into
5 distinct regions or strata. They are
the Stratum basale Stratum spinosum Stratum
granulosum Stratum lucidium Stratum corneum
As new cells formed in the deepest layers of
epidermis, the older cells are pushed to the
surface which will protect the inner new cells.
Gradually the surface cells are getting filled
with Keratin. This process is called
keratinization.
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Stratum corneum is the upper most layer of the
epidermis having more than 20 layers of dead
cells. These cells get filled with keratin. They
are said to be cornified. These cornified cells
are surrounded by a hard protective envelope.
Stratum lucidium is the next upper layer of the
straum granulosum. It is a thin Zone having
several of dead cells.
Stratum granulosum is the middle layer of the
epidermis. It has 3-5 layers of flat cells.
Stratum spinosum lies over the stratum basale. It
has 8 10 layers of polygonal cells.
Stratum basale is in the deeper region of
epidermis consists of singler layer of columnar
cells. Keratinization begins in this region.
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Dermis layer of the skin
Dermis provides the structural strength to the
skin. It accomodates nerve endings, hair
follicles, smooth muscles and glands. It is
divided into 2 layers, namely the superficial
papillary layer (has papillary projections) and
the deeper reticular layer (major layer of the
dermis, dense in nature continuous with the
hypodermis)
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Hypodermis Layer of the Skin
The skin or integument rests on layers of cells
called Hypodermis The Hypodermis attaches the
skin to the underlying bones and muscles. It
supplies blood vessels and nerves to the skin
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Thin skin Thick Skin
In the thin skin each layer inturn has few layers
of cells. Ther are only has 1 or 2 layers of
cells in Stratum granulosum The general body
surface has thin skin.
In the thick skin all 5 layers are visible.
Stratum corneum contains numerous cells. Thick
skin is formed in the soles of feet, palms of
hands, tips of fingers.
CALLUS The regions of skin subjected to constant
friction or pressure are thickened to form the
callus. The callus has several layers of cells in
stratum corneum
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Skin Color
The thickness of the stratum corneum and blood
circulation can also cause the skin
color. Hormones and exposure to light can also
alter the skin color. Normally skin color is
caused by the Melanin pigments.
Melanin pigments provide color to skin, hair, and
eye. Melanin is produced by melanocytes. Producti
on of melanin is herditary.
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Skin derivatives Hair
Hair has a root and a shaft. Shaft projects above
the skin. Root remains below the surface. The
base of the root has hair bulb.
shaft and the most of the root are formed of dead
keratinized epithelial cells arranged in 3
concentric layers called the medulla, cortex and
cuticle. Central axis of the hair is formed of
the medulla.
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Muscle cells found associated with hair follices
are called Arrector Pili. Cotraction of these
muscles cause goose flesh making the hairs to
stand on end
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Skin derivatives Hair
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HAIR COLOR may vary with the amount and types of
melanin present in the skin. During old age
decrease in melanin causes White hair. Grey hair
has a mixture of faded, unfaded and white hairs.
Skin derivatives Hair
HAIR GROWTH is due to addition of cells at the
base of hair root. The hair growth stops at
specific stages. After a resting period , New
hair replaces old hair. Hairs on the head grow
for a period of 3 years and rest for 1-2 years.
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Skin derivatives Nails
Each Nail is made up of 2 parts. They are Nail
root the Nail body. The Nail body is the
visible part. The Nail root covered by the
skin. The proximal and Lateral edges of the nail
are covered by the nail fold.
The Nail is found placed on the Nail matrix and
nail bed. Lunula, a small white regionat the base
of nail contains nail matrix. The free edge of
the Nail body is the Hyponchium. The stratum
corneum of the nail fold grows on to the nail
body as the Eponchium.
The nails grow at an average rate of 0.5-1.2 mm
per day
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Glands of the Integumentary System
The Skin has - Sebacious glands - Sweat
glands - Apocrine glands
The modified form of sweat glands are -
Mammary glands - Ceruminous glands
The most common type of Sweat glands on the skin
are Merocrine glands. They open directly on to
the skin through seat pores. Numerous Sweat
glands are found in the palms of the hands and
soles of the feet.
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Glands of the Integumentary System
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INTEGUMENTARY SYSTEM
FUNCTIONS OF THE SKIN

• - covers the outside of the body
• detects stimuli such as touch, pain and
  temperature
• prevents the entry of infectious agents
• protects internal structures
• produces Vitamin D
• reduces water loss
• regulates body temperature
• removes excess salts through perspiration

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