this slide include the explanation of the skin i.e only dermis and hypodermis.

3. DERMIS
• It is tough and elastic
• Formed from connective tissue and
matrix contains collagen fibres
interlaced with elastic fibres.
• Rupture of elastic fibres occurs
when the skin is overstretched,
resulting in permanent striae,
stretch marks.
• Collagen fibres bind water and give
the skin its tensile strength, but as
this ability declines with age,
wrinkles develop.

5. Wrinkles Stretch marks

6. DERMIS
• Fibroblasts (wound healing), mast cells (histamine and heparin) and macrophages
(engulfing bacteria and antigen)are the main cells found in the dermis
• Its deepest layer is the subcutaneous layer containing areolar tissue & varying
amount of Adipose tissue
• The structure in the dermis are:
 Blood and lymph vessels
Sensory nerve endings
Sweat glands & their ducts
Hairs, arrector pili muscles & sebaceous glands

7. BLOOD AND LYMPH VESSELS
• Arterioles from a fine network with capillary branches supplying sweat glands,
sebaceous glands, hair follicles and the dermis.
• Lymph vessels form a network throughout the dermis

8. SENSORY NERVE ENDINGS
• Sensory receptors sensitive to touch, temperature, pressure and pain are widely
distributed in dermis.
• Incoming stimuli activate different types of sensory receptors
• E.g: Pacinian corpuscles is sensitive to deep pressure
• Meissner’s corpuscles – Light pressure
• Free nerve endings- Pain

10. SWEAT GLANDS
• Widely distributed throughout the skin
• Most numerous in palms of hands, soles of feet, axillae and groins.
• Formed from epithelial cells
• Body of glands lie coiled in subcutaneous tissues
• There are 2 types of seat glands:
1. Eccrine glands
2. Apocrine glands

11. SWEAT GLANDS
ECCRINE GLANDS:
 Common type and open on to skin surface
through tiny pores
 Sweat produced here is clear, watery fluid
important in regulating temperature.
APOCRINE GLANDS:
 Open into hair follicles and become active in
puberty
May play role in sexual arousal
They are found e.g in axilla
 Bacterial decomposition of their secretions
causes unpleasant odour.
Specialized example of this type of gland
is CERUMINOUS GLAND OF THE
OUTER EAR;
WHICH SECRETES EARWAX.

12. FUNCTIONS OF SWEAT GLANDS
 Regulation of body temperature (Thermoregulation)
 Excessive sweating may lead to dehydration and depletion of sodium chloride.
Improves grip by moistening palms and soles
 Excretion of drugs
Role as odoriferous sexual attractants (Pheromones)
 Increases frictional resistance and tactile sensibility

13. HAIRS
 Grow from hair follicles
At the base of follicles; is a cluster of cells
called hair papillae or bulb
 The hair is formed by multiplication of the cells
of the bulb
 As they are pushed upwards, away from their
source of nutrition, the cells die and become
keratinized.
 The part of the hair above the skin is Shaft and
the remainder is root

14. HAIRS
 This figure shows the hair growth and desquamation,
which roughens the skin surface and harbor the
microbial growth and removed constantly by rubbing
off of the top most layer.
 Hair color is genetically determined and depends on
the amount and type of melanin present
White hair is the result of replacement of melanin by
tiny air bubbles.

15. ARRECTOR PILI
 These are the little bundles of smooth muscle fibres
attached to the hair follicles
Contraction makes the hair stand erect and raises the
skin around the hair causing ‘goose flesh’.
 The muscles are stimulated by sympathetic nerve fibres
in response to fear and cold
Erect hair trap air, which acts as an insulating layer.
This is an efficient warming mechanism, especially
when accompanied by shivering (involuntary
contraction of skeletal muscles)

16. SEBACEOUS GLANDS
 Secretes an oily antimicrobial substance, Sebum,
into hair follicles.
 Present in the skin of all the body pars except the
soles of feet and palms of the hands
 Most numerous in scalp, face, axillae and groins
In regions of transition from one type of superficial
epithelium to another, such as: lips, eyelids, nipple,
labia minora and glans penis, there are sebaceous
glands that are independent of hair follicles, secreting
sebum directly on to the surface.

17. FUNCTIONS OF SEBACEOUS
GLANDS
 Keeps hair soft, pliable and gives shiny appearance
 On skin, it provides waterproofing and acts as bactericidal and fungicidal agent;
preventing infection
 Prevents drying and cracking of skin; especially on exposure to heat and sunlight
Their activity increases in puberty and declines with increasing in age
(maceration)

18. NAILS
 Equivalent to claws, horns and
hooves of the animals
 These are hard, horny keratin
plates that protects the tips of
the fingers and toe
 The root of the nail is
embedded in the skin and
covered by the cuticle, which
forms the hemispherical plates
area called the lunula.

19. NAILS
 The nail plate is the exposed part
that has grown out from the nail bed
 Finger nail grow more quickly than
toe nails and growth is faster when
the environmental temperature is
high.

20. • Hypoderm consists of thick bundles of collagen
and elastic fibres stretching from the reticular
dermal layer and forming a wide-loop reticulum in
which accumulations of large fat cells, lobules of
fatty tissue, are lodged
• The thickness of the hypoderm varies from 2mm
till 10cm and more
• In some areas there is no hypoderm at all (eyelids,
prepuce, small pudendal, lips, scrotum
HYPODERMIS