Integumentary system

The skin and hypodermis
Skin structure Functions
Epidermis
Layer of the Epidermis
Dermis
Hypoderm
Skin color
Skin Appendages

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Ahmed Abdulwahab
UG : (1330095)

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3. The skin and hypodermis
Skin – our largest organ
Accounts for 7% of body weight
The skin varies in thickness from 1.5 to 4mm distinct
region
The superficial region is a thick epithelial tissue
Divided into two distinct layers
Epidermis
Dermis
Hypodermis – lies deep to the dermis
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Skin structure

5. Functions
Protection : Skin cushions and insulates
the deeper body organs
Protects the body from scrapes ,chemicals
and invading microorganisms
The epidermis is waterproof, preventing
unnecessary loss of water across the body
surface
produce pigment to protect the skin from
the harmful effects of ultraviolet (UV)
radiation
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6. Function
Body temperature regulation :The skin’s rich
capillary networks and sweat glands
regulate the loss of heat from the body
Excreation : The skin acts as a miniature
excretory system when urea, salts, and
water are lost through sweat.
Production of vitamin : The epidermal cells
use UV radiation to synthesize vitamin D
Sensory reseption : touch, pressure,
temperature, and pain
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7. Epidermis
A keratinized stratified squamous
epithelium that contains four distinct
types of cells
Keratinocytes – most abundant epidermis cell
Produce keratin – a tough fibrous protein that gives
the epidermis its protective properties.
Produce antibodies and enzymes
Arise from deepest layer of epidermis
Keratinocytes are dead at skin's surface
Merkel cells ,Tactile epithelial cells –
associated with sensory nerve ending and
function as a receptor for touch
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8. Epidermis
Melanocytes – secrete the pigment melanin
 Melanin is made in membrane-walled granules and then
transferred through the cell processes to nearby keratinocytes
Langerhans cells : macrophage like dendritic cells
Millions of these dead cells rub off every day, giving us an
entirely new epidermis every 35 to 45 days—the average
time from the birth of a keratinocyte to its final wearing
away.
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9. Layer of the Epidermis
Stratum basale
Deepest layer of epidermis
Attached to underlying dermis
Also called the Stratum
germinativum
these Cells divide rapidly
Merkel cells – associated with
sensory nerve ending
Melanocytes – secrete the
pigment melanin
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10. Layer of the epidermis
Stratum spinosum (spiny layer)
"Spiny" appearance caused by artifacts of histological preparation
Contains thick bundles of intermediate filaments
Contains star-shaped cells are part of the immune system
Dendritic cells police the outer body surface, using receptor-mediated
endocytosis to take up foreign proteins (antigens) that have invaded the
epidermis
Stratum granulosum
Consists of one to five layers of flattened keratinocytes and intermediate
filaments
intermediate filaments contain
Keratohyaline granules – help form keratin
Lamellated granules – contain a waterproofing glycolipid
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11. Layer of the epidermis
Stratum lucidum (clear layer)
Occurs only in thick skin but not in thin skin
Consists of a few rows of flat, dead
keratinocytes
It is also named the transition zone
Stratum corneum (horny layer)
Thick layer of dead keratinocytes and
thickened plasma membranes
Protects skin against abrasion and
penetration
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12. Dermis
Second major layer of the skin
Strong, flexible connective tissue
Richly supplied with blood vessels and nerves fibers
The deep dermal plexus is located between the hypodermis
and the dermis
It nourishes the hypodermis and the structures located within the
deeper portions of the dermis
subpapillary located just below the dermal papillae
perform a critical role in temperature regulation. These vessels are
so extensive that they can hold 5% of all blood in the body.
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13. Dermis
The dermis has two layers
papillary layer the superficial 20% of the
dermis
is areolar connective tissue containing very thin
collagen and elastic fibers It includes the dermal
papillae
increase the surface area for exchange of gases,
nutrients, and waste products between these layers
reticular layer the deeper – 80% of thickness
of dermis. is dense irregular connective tissue
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14. Hypodermis
Deep to the skin – also called superficial fascia
Contains areolar and adipose connective
tissues
Besides storing fat, the hypodermis anchors the
skin to the underlying structures
 is also an insulator because fat is a poor
conductor of heat, it helps prevent heat loss
from the body
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15. Skin color
Three pigments contribute to skin color
Melanin – most important pigment – made
from tyrosine
Carotene – yellowish pigment from carrots
and tomatoes
Hemoglobin – Caucasian skin contains little
melanin
Allows crimson color of blood to show through
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16. Skin color
Melanin in granules passes from melanocytes (same number in all
races) to keratinocytes in stratum basale
Digested by lysosomes
Variations in color
Protection from UV light vs vitamin D?
Derived from epidermis but extend into dermis
Include
Hair and hair follicles
Sebaceous (oil) glands
Sweat (sudoriferous) glands
Nails
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17. Skin Appendages
Hair
Minor protective functions (retain heat, decrease sunburn,
eyelashes protect eyes)
Structure
shaft – projects from skin
follicle – extends into dermis
root – lies within the follicle
bulb – contains CT, vessels and nerves
sebaceous gland – lubricates hair
arrector pili muscle – attached to follicle and contracts to move
hair (hair growth, goosebumps)
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19. Skin Appendages
Hair Growth
influenced by: (in this order)
nutrition - main influence
hormones
blood flow
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Hair Pigment
caused by proportions of 3 melanin types
•dark hair – true melanin
•blonde and red – melanin with iron and sulfur
•gray/white hair - melanin replaced by air bubbles in shaft

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21. Skin Appendages
Nails
Scale-like modifications of the epidermis
Heavily keratinized
Stratum basale extends beneath the
nail bed to form nail matrix
Responsible for growth ( matrix region)
Lack of pigment makes them colorless
Lunula “little moon” – area of cell
growth (white semicircle at base of nail)
Cuticle – area of skin that covers base
of nail
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Nail Structures

22. Skin Appendages
Sebaceous glands
all over except palms and soles of feet
Produce oil for waterproofing
Lubricant for skin & kills bacteria
Most with ducts that empty into hair follicles
Glands are activated at puberty: stimulated by hormones
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23. Skin Appendages
Eccrine glands
Widely distributed in skin:
abundant on palms, soles,
forehead
Sweat composition:
mostly water with a slightly
acidic 4-6 pH
Function:
thermoregulation
Apocrine glands
Ducts empty into hair follicles
Found mainly in anogenital &
axillary region
Begin to function at puberty
due to hormones /
pheromones
Organic contents: Fatty
acids and proteins – can
have a yellowish color that
stains clothes
Odor is from associated
bacteria
Ceruminous glands
Modified apocrine gland
Found in outer 1/3 of ear
canal
Produce ear wax to trap
“invaders”
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Sweat Glands

24. Thank you
for your attention
Ahmed abdulwahab
UG : (1330095)
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