the skin - my anatomy and physiology mentor · pdf filethe skin • function –...
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THE SKIN • Function
– Protective covering
• Bacterial infection
• Physical trauma
– Receptors
• Touch, pressure, pain, heat and cold
– Vitamin D production
• UV light
– Regulation of body temperature
• Dilation or constriction of blood vessels
• Sweat glands
Epidermis
Dermis
Hypodermis
(Subcutaneous
Layer)
SKIN REGIONS
SKIN REGIONS
• Epidermis
– Protective outer
epithelial layer
– Avascular
Dermis
Tough, fibrous
connective tissue
layer
Largest region of
the skin
Vascular
SKIN REGIONS
Hypodermis
Region just deep to
the dermis
Adipose and areolar
C.T.
Anchors the skin
SKIN REGIONS
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
LAYERS of the EPIDERMIS
THE EPIDERMIS
• Definition
– Keratinized, stratified squamous E.T.
• Layers
– Five layers in thick skin
– Four in all other skin
THE EPIDERMIS
• Cells
– Keratinocytes
• Most numerous cell type
• Produce the protein keratin for waterproofing and
protection
• Replaced every 25 to 45 days
EPIDERMAL LAYERS
• Stratum Basale
– Deepest layer
– Attached to dermis
– Single layer of cuboidal
keratinocytes
– Mitotic layer
– Contains melanocytes
• Produce the pigment melanin
– Contains Merkel’s discs =
• Sensory nerve endings
• Pressure
melanocytes
EPIDERMAL LAYERS:
Stratum basale
EPIDERMAL LAYERS
Stratum spinosum
Several layers of
keratinocytes with a “spiny”
appearance
Scattered melanin granules
Langerhans cells =
macrophages
EPIDERMAL LAYERS:
Stratum Spinosum
EPIDERMAL LAYERS
Stratum granulosum
Thin region of dark-
staining cells
Flat cells with
keratohyaline granules
Cells above are dead
EPIDERMAL LAYERS:
Stratum Granulosum
EPIDERMAL LAYERS
Stratum lucidum
Only present in thick
skin
Thin, translucent layer
of dead keratinocytes
EPIDERMAL LAYERS:
Stratum Lucidum
EPIDERMAL LAYERS
Stratum corneum
Outer, loose layer of
dead, flaky cells
Protects skin from:
Abrasion or penetration
EPIDERMAL LAYERS:
Stratum Corneum
THE DERMIS
Definition
A thick, flexible C.T. layer
Rich in nerve fibers
Very vascular
Layers
Papillary layer
Reticular layer
THE DERMIS
Papillary Layer
Loosely woven
Highly vascular
Contains:
Dermal papillae
Meissner’s corpuscles
• Detect touch
Free nerve endings
• Detect pain
Larger dermal folds form
ridges = fingerprints
On palms of hands and
soles of feet
dermal papillae Meissner’s
corpuscle
LAYERS of the DERMIS
dermal papilla
epidermal peg
STRUCTURES of the DERMIS
Meissner’s Corpuscle
STRUCTURES of the DERMIS
Reticular Layer
Makes up 80% of the
dermis
Dense, irregular C.T. rich
in collagen
Contains:
Hair follicles
Sebaceous glands
Blood vessels and nerves
Pacinian corpuscles in
deep regions
• Detect crude touch; deep
pressure
Pacinian corpuscle
LAYERS of the DERMIS
Pacinian Corpuscle
STRUCTURES of the DERMIS
Three Pigments Determine Skin Color
Melanin
Brown to black pigment
Prevents UV damage
Carotene
Yellowish, orange pigment
Noticeable in the palms and soles
Hemoglobin
Red pigment when oxygenated
Gives the skin a bluish or gray appearance when
poorly oxygenated (cyanosis)
SKIN COLOR
Definition
Keratinized cells produced by hair follicles
Hair Structure
Papilla
At the hair base
Supplies the cells with nutrients
Arrector pili
Smooth muscles
Pull hair upright
APPENDAGES of the SKIN:
Hair and Hair Follicles
papilla
epidermal tissue
Hair and Hair Follicles
Arrector Pili Muscle
Hair and Hair Follicles
Types of Hair
Vellus Hair
Soft body hair of children and adult females
Terminal Hair
Coarse, longer growing hair
Found:
• Eyebrows, head, armpits, pubic regions of
adults
• Face, chest, arms and legs of adult males
APPENDAGES of the SKIN:
Hair and Hair Follicles
Definition
Epidermal modifications
Protects the dorsum of the
fingers and toes
Contain keratin
APPENDAGES of the SKIN:
Nails
Two Types:
Eccrine Sweat Glands
Open to skin surface
Regulation of body temperature
Merocrine
sweat gland
APPENDAGES of the SKIN:
Sudoriferous (Sweat) Glands
Apocrine Sweat Glands
Open into hair follicles
in anal, groin and
axillary region
Active at puberty
Not important in thermoregulation
Active during stress
Apocrine
sweat gland
APPENDAGES of the SKIN:
Sudoriferous (Sweat) Glands
Sudoriferous (Sweat) Glands
Definition
Modified sweat glands
Within breasts
Produce milk following
childbirth
mammary
glands
APPENDAGES of the SKIN:
Mammary Glands
Definition
Simple alveolar glands
found all over the body
except on the palms
and soles
Near hair follicles
Secretes sebum
Sebaceous
gland
APPENDAGES of the SKIN:
Sebaceous (Oil) Glands
Sebaceous (Oil) Glands
Hyperthermia
An abnormally high body temperature
Can result in:
• Heat exhaustion (headache, vomiting, and
tiredness)
• Heat stroke (dizziness, confusion, delusions)
• Increased fluid intake and possible medical
care are needed in both cases
Fever
• Hyperthermia brought on by illness
• Body’s attempt to fight off infection
SKIN DISORDERS
Hypothermia
An abnormally low body temperature
Results in:
• Shivering, incoherent speech and lack of
coordination
• Body functions slow and death occurs when
metabolism stops completely
• Person must be warmed immediately
SKIN DISORDERS
Skin Cancer
Squamous cell carcinoma and basal cell
carcinoma
Most common
Likely caused by sun exposure
Surgical removal is the standard treatment
Melanoma
Arises from melanocytes
Can metastasize
SKIN DISORDERS
Basal Cell
Carcinoma
Squamous Cell
Carcinoma
Malignant
Melanoma
SKIN CANCER
Burns
Factors affecting burn severity
Depth of burn
Extent of area burned
Classification of burns
1st degree burns
• Epidermis is burned: redness and pain
• Damaged skin peels off
SKIN DISORDERS
Burns
Classification of burns
2nd degree burns
• Extends through epidermis and part of the dermis
• Results in redness, pain and blisters
• May result in scarring
SKIN DISORDERS
Burns
Classification of burns
3rd degree burns
• Entire thickness of skin is burnt
• Blood vessels, sweat glands, and other skin
accessories are also burnt
• Fluid and heat loss and bacterial infection
• Skin grafting required
• Survival chances are not good if large area
SKIN DISORDERS
2nd Degree Burn 3rd Degree Burn
1st Degree Burn
BURNS