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

Integumentary System Components Cutaneous membrane (skin)

▪ Epidermis▪ Dermis▪ Accessory structures

Subcutaneous layer (hypodermis)

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Main Functions of the Integument Protection Temperature maintenance Synthesis and storage of nutrients Sensory reception Excretion and secretion


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


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


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


Figure 5-4


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


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


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


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


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

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