integumentary system components cutaneous membrane (skin) ▪ epidermis ▪ dermis ▪ accessory...
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Integumentary System Components Cutaneous membrane (skin)
▪ Epidermis▪ Dermis▪ Accessory structures
Subcutaneous layer (hypodermis)
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Main Functions of the Integument Protection Temperature maintenance Synthesis and storage of nutrients Sensory reception Excretion and secretion
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Figure 5-1
The Epidermis Stratified squamous
epithelium Several distinct cell layers
▪ Thick skin—five layers▪ On palms and soles
▪ Thin skin—four layers▪ On rest of body
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The Epidermis Keratinocytes
▪ 90% of epithelial cells Melanocytes
▪ 8% of epithelial cells▪ Produce pigment melanin
▪ Pigments skin (brown)▪ Absorbs UV
The Epidermis Langerhans cells
▪ Participate in immune responses Merkel cells
▪ Located in the deepest layer of epidermis▪ Contact tactile (Merkel disk) of sensory
neurons▪ Help to detect touch sensations
Cell Layers of The Epidermis Stratum germinativum (basale) Stratum spinosum Stratum granulosum Stratum lucidum (in thick skin) Stratum corneum
▪ Dying superficial layer▪ Keratin accumulation
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The Structure of the Epidermis
Figure 5-2
Melanocytes
Figure 5-3
Effects of UV Radiation Beneficial effect
▪ Activates synthesis of vitamin D3
Harmful effects▪ Sun burn▪ Wrinkles, premature aging▪ Malignant melanoma▪ Basal cell carcinoma
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Figure 5-4
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Types of SkinThin skin
▪Covers all of body except for palms, soles, and fingertips▪Lacks stratum lucidum▪Thin stratum spinosum and stratum corneum▪Lacks epidermal ridges▪Fewer sweat glands than thick skin▪Sparser distribution of sensory receptors
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Types of Skin Thick Skin
▪ Covers palms, soles, fingertips▪ Has stratum lucidum▪ Thicker stratum spinosum and stratum
corneum▪ Lacks hair follicles, arrector pili muscles, and
sebaceous glands▪ Has a greater number of sweat glands▪ Sensory receptors more densely clustered
Epidermal Ridges Palms, fingers, soles, toes Ridges and grooves Develop during 3rd and 4th months of
fetal development
Skin Color Melanin
▪ Causes colors from pale yellow to tan to black▪ Melanocytes
▪ More in areas of darker color (ex. Penis, nipples, areolae, face, limbs)
▪ Color determined by amount of pigment produced▪ Accumulation of pigment = freckles or liver spots (age
spots)
Skin Color Carotene
▪ Yellow-orange pigment▪ Precursor of vitamin A
▪ Used to synthesize pigments needed for vision
▪ Found in stratum corneum and fatty areas of dermis and subcutaneous layer
Hemoglobin ▪ Oxygen carrying pigment▪ Red▪ Causes pink skin when little carotene or melanin are
present
Albinism Inherited Inability to produce melanin
Vitiligo Partial or incomplete loss of melanocytes Produces white patches
Skin Color Cyanotic
▪ Bluish▪ Appears in mucous membranes, nail beds,
skin▪ Sign of lack of oxygen
Jaundice▪ Yellowish coloration▪ Caused by buildup of bilirubin in the blood▪ Can indicate liver disease
Skin color Erythema
▪ Redness of the skin▪ engorgement of capillaries in the dermis with
blood▪ Caused by injury, exposure to heat, infection,
inflammation, or allergic reactions
Hair Function = protection
▪ Scalp – from sun’s rays & injury▪ Also decreases heat loss
▪ Eyebrows & eyelashes – protect eyes from foreign objects▪ Nostrils – protect from foreign objects▪ Ear canal – protect from foreign objects
Function = touch▪ Touch receptors associated with hair follicles (root hair
plexus)▪ Activated when hair is moved
Hair Follicles
Figure 5-5(b)
Hair Follicles
Figure 5-5(c)
Hair growth cycle Each follicle goes through a growth cycle
▪ Growth stage▪ Scalp: 2-6 years growth▪ 0.3 mm/day growth rate
▪ Resting stage▪ Growth of hair stops▪ Scalp: 3 months
▪ After resting stage▪ Hair replaced▪ New growth stage
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Rate of growth & replacement altered by: Illness Radiation therapy Chemotherapy Age Genetics Gender Severe emotional stress Rapid weight loss (reduction of calories and/or
protein)
Hair loss Normal = 100 per day (from scalp) Rate of hair shedding increases 3-4
months after childbirth
Alopecia▪ Partial or complete loss of hair▪ May result from genetic factors, aging,
endocrine disorders, chemotherapy, or skin disease
Types of hair Lanugo
▪ Very fine, nonpigmented hairs▪ Produced by the 5th month of fetal development▪ Cover body of fetus▪ Usually shed before birth (except scalp, eyebrows,
eyelashes) Vellus hairs
▪ “peach fuzz”▪ Replace lanugo▪ Short, fine hairs▪ Slightly thicker than lanugo
Terminal hairs Head Eyebrows Eyelashes Coarse pigmented hairs
▪ Develop in presence of androgens▪ During puberty▪ In axillae (armpits) and pubic regions
Male = 95% terminal hair:5% vellus hair Female =65% terminal hair:35% vellus hair
Hair color amount and type of melanin in keritinized
cells▪ melanocytes found in the matrix of bulb
Dark hair = pure melanin Blond or red hair = variants of melanin
▪ More sulfur or iron Graying = decline of tyrosinase
▪ Enzyme that catalyzes production of melanin White = accumulation of air in medullary shaft
Sebaceous Glands - Oil glands In dermis Usually open into the neck of hair follicle
▪ Except in lips, glans penis, labia minora, and tarsal glands
Absent in palms and soles Small on trunk and limbs Large on breasts, face, neck and upper chest Secrete sebum
▪ Oily substance - triglycerides, cholesterol, proteins, and inorganic salts
▪ Coats surface of hairs - Prevents drying and becoming brittle
▪ Prevents excessive evaporation from skin▪ Keeps skin soft & Inhibits growth of certain bacteria
Acne Inflammation of sebaceous glands Usually begins during puberty
▪ Infected by bacteria
Sudoriferous glands - Sweat glands 3 to 4 million Secrete through exocytosis into hair
follicles or onto skin surface through pores
Sudoriferous glands (continued) Eccrine sweat glands
▪ Simple, coiled tubular▪ More common type▪ Distributed throughout skin, except:
▪ Lips, nail beds, glans penis, glans clitoris, labia minora, eardrums
▪ Most numerous on forehead, palms, soles▪ Sweat consists of water, ions, urea, uric acid, ammonia, amino
acids, glucose, and lactic acid▪ Function = regulate body temperature
▪ Insensible perspiration – sweat that evaporates before perceived as moisture
▪ Sensible perspiration – sweat seen as moisture
▪ Function = eliminate waste
Sudoriferous glands (continued) Apocrine sweat glands▪ Simple, coiled tubular▪ Found in axilla (armpit), groin, areolae, and
bearded regions of face▪ Secretions through exocytosis
▪ These are actually merocrine glands They used to be thought to be apocrine
Sudoriferous Glands (continued) Ceruminous glands
▪ Sweat glands of the external ear▪ waxy secretion▪ Combined secretion of ceruminous and
sebaceous glands in the ear is called earwax▪ In combinations with hairs – impedes
entrance of foreign objects
Figure 5-7
Accessory Structure Nails
▪ Plate of tightly packed, hard, keratinized epidermal cells
Average growth = 1mm /week Function = grasp small objects, protection,
scratching
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Figure 5-8
Deep Wound Healing Occurs when injury extends into the dermis
and hypodermis 4 phases:
▪ Inflammatory phase▪ Blood clot forms; inflammation
▪ Migratory phase▪ Clot becomes scab; granulation tissue forms
▪ Proliferative phase▪ Extensive growth of epithelial cells in random patterns
▪ Maturation phase▪ Scab sloughs off
Deep Wound Healing Fibrosis
▪ Scar tissue formation
▪ Hypertrophic scar▪ Scar remaining within boundaries of wound
▪ Keloid scar▪ Scar extending beyond boundaries of wound
Skin Grafts Covering a wound with healthy skin
taken from a donor site▪ Transplanted skin taken from:
▪ Self = autograft▪ Identical twin = isograft
▪ Analogous skin transplantation Especially with burn patients
Major Age-Related Changes Injury and infection increase Immune cells decrease Sun protection diminishes Skin becomes dry, scaly Hair thins, grays Sagging, wrinkles occur Heat loss decreases Repair slows
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