The skin is the largest organ of the body, covering the entire surface. It consists of two main layers - the epidermis and dermis. The epidermis is composed of stratified squamous keratinized epithelium and overlies the dermis, a dense connective tissue layer derived from mesoderm. Embedded within the dermis are structures like sweat glands, sebaceous glands and hair follicles which develop from the epidermis during embryogenesis. Skin lines various cavities and becomes continuous with mucous membranes in areas like the lips, anus, nose and urogenital regions.

2. The integument, composed of skin and its
appendages-the sweat glands, sebaceous
glands, hair, and nails-is the largest organ of
the body, constituting 16% of body weight. It
invests the entire body, becoming continuous
with the mucous membranes of the digestive
system at the lips and the anus, the
respiratory system in the nose, and the
urogenital systems where they surface.

3. Additionally, the skin of the eyelids
becomes continuous with the
conjunctiva lining the anterior portion
of the orb. Skin also lines the external
auditory meatus and covers the
external surface of the tympanic
membrane.

9. • Skin consists of two layers: an outer epidermis and
a deeper connective tissue layer, the dermis.
• The epidermis is composed of an ectodermally
derived stratified squamous keratinized epithelium.
• Lying directly below and interdigitating with the
epidermis is the dermis, derived from mesoderm
and composed of dense, irregular collagenous
connective tissue.

10. • The hypodermis, a loose connective tissue
containing varying amounts of fat, underlies
the skin. The hypodermis is not part of the
skin but is the superficial fascia of gross
anatomical dissection that covers the entire
body, immediately deep to the skin.

11. Cells of epidermis
• 1.Keratinocytes
• 2.Melanocytes
• 3.Intraepithelial macrophages
• 4.T-lympocytes
• 5.Merkel’s cells

17. • Dermis (Corium) The dermis, the layer of skin
immediately deep to the epidermis, is derived from
mesoderm and comprises a loose papillary layer
and a deeper, denser reticular layer. The region of
the skin lying directly beneath the epidermis, called
the dermis, is derived from the mesoderm and is
divided into two layers: the superficial, loosely
woven papillary layer and the deeper, much denser
reticular layer.

22. • Sweat glands, sebaceous glands, and hair
follicles, all derived from the epidermis,
invade the dermis and hypodermis during
embryogenesis, where they remain
permanently. Groups of smooth muscle cells
are located in the deeper regions of the
reticular layer at particular sites such as the
skin of the penis and scrotum and the areola
around the nipples; contractions of these
muscle groups wrinkle the skin in these
regions.

23. Hair
• 1.Number-100000 on the head;
• 2.Length is 1mm-1,5-2,0m.
• 3.Speed of growth is 0,3-0,4mm a day.
• a)testosterone stimulates growth of hairs on
the face(mustache, beard).
• b)cytokines stimulate growth of the hair.
• c)haircutting, shaving don’t influence on to
speed of growth and number of hairs.
• 4.Duration of life-several months to 2-6 years.
• 5.One hair is replaced by the new one(during
all the life replacement of several millions of
hairs).