integumentary system components cutaneous membrane (skin) ▪ epidermis ▪ dermis ▪ accessory...

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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