Chapter 5: The Integumentary System
I. Function of Integumentary System
A. Regulation of Body Temperature
B. Protection from Dehydration and Infection
C. Respond to Tepmperature, Pressure, Pain
D. Excretion of Water, Salts, Urea (nitrogenous waste)
E. Synthesis Vitamin D (essential for Ca + P absorption)
F. First Defensive Barrier of Immune Response
II. Structure of Integumentary System
A. Epidermis (epithilial tissue)
1. stratum corneum
2. stratum lucidum
3. stratum granulosum
4. stratum spinosom
5. stratum basale
B. Dermis (connective tissue)
1. papillary layer (region)
2. reticular layer (region)
III. Structure of Epidermis (epithelial tissue)
A. Different Cells of Epidermis
1. keratinocyte - produce protein "keratin" (structure)
2. melanocyte - produce "melanin" (pigment)
3. nonpigmented granular dendrocytes
a. Langerhan's cells
b. Granstein cells both assist in immunity
B. Stratum Corneum
1. stratified sqamous epithilium
2. 25-30 rows of dead keratinized cells
3. keratinization occurs as cells rise from below
4. protects against light, heat, bacteria, chemicals
5. most superficial layer of epidermis
C. Statum Lucidum
1. present only in thick areas (palms, feet)
2. contain clear substance called eleidin
3. eleidin eventually changes into keratin at surface
D. Stratum Granulosum
1. cells from lower layers begin to die here
2. contain granules with keratohyalin
3. keratohyalin is precursor to eleidin and keratin
E. Stratum Spinosum
1. 8-10 rows of polyhedral shaped cells
2. contain spine-like projections ("spinosum")
F. Statum Basale (Stratum Germinativum) (germination)
1. deepest layer of the epidermis
2. single layer of cuboidal-columnar shaped cells
3. origin of all cells of epidermis through mitosis
4. origin of cells for sweat-oil glands and hair
IV. Structure of the Dermis (connective tissue)
A. Overall Features
1. thick in some areas, thinner in others
2. contains blood supply, nerves, glands, hair follicle
B. Papillary Layer (Region)
1. loose connective tissue - much "elastin"
2. dermal papillae cause ridges in the epidermis above
3. Meissner's corpuscles - sense organ for touch
4. small capillaries supply O + nutrients
C. Reticular Layer (Region)
1. dense, irregular connective tissue "collagen"
2. collagen fibers interlace in net-like fashion
3. contains: adipose, hair follicle, nerves, glands
4. subcutaneous layer attaches skin to tissue below
a. Paccinian corpuscles - sense pressure change
V. Hair (pili)
A. Shaft - projects above surface of epidermis
1. medulla - polyhedral cells with eleidin
2. cortex - elongated cells with/out pigment
3. cuticle - outermost layer, like shingles on roof
B. Root - below epidermis, penetrates into the dermis
C. Hair Follicle - at the base a a single hair
1. external root sheath - basale and spinosum extension
2. internal root sheath - internal hair cell layers
3. bulb - base of hair cell
4. papilla - in the bulb, provides nourishment for hair
5. matrix - origin of new hair cells
D. arrector pili - smooth muscle, cause hair to rise
E. hair root plexuses - nerve bundle responds to touch
VI. Glands
A. Sebaceous Glands (oil glands)
1. genearlly connected to hair follicles
2. simple branched acinar glands
3. sebum - mixture fat, protein, cholesterol, salt
4. prevent dessication, keep skin soft, anti-bacterial
a. infected gland - acne, blackheads
B. Sudoriferous Glands (sweat glands)
1. Apocrine Sweat Glands
a. simple branched tubular glands
b. only in axilla (arm pit), pubic + areole areas
c. in dermis, duct opens into a hair follicle
2. Eccrine Sweat Glands
a. simple coiled tubular glands
b. all over the body
c. subcutaneous, opens onto epidermal surface
3. Perspiration (sweat)
a. mixture of water, salt, urea, ammonia, acids
b. eliminates waste and heat
C. Ceruminous Glands
1. simple coiled tubular glands
2. in the external auditory meatus (canal)
3. cerumen - wax-like substance, prevents entry
VII. Nails
A. Nail Body - portion resting in the digit itself
B. Free Edge - extends from the end (part you cut)
C. Nail Root - extends from the proximal nail groove
a. lunula - whitish semilunar area
b. eponychium (cuticle) - extension of epidermis
c. nail matrix - superficial cells -> nail cells
VIII. Skin Color
A. Melanin - pigment made in melanocytes
1. in basale and spinosum layers of epidermis
2. melanoblasts -> melanocytes in stratum basale
3. darkness due to melanin quantity (not cell #)
4. albinism - inability to produce melanin
5. vitligo - patchy loss of melanocytes
6. freckles - patchy concentration of melanocytes
7. UV light causes: tyrosine --> melanin production
B. Carotene
1. in stratum corneum and fatty areas of dermis
2. melanin + carotene = yellowish color
C. Other Colors
1. pink (Caucasian) - lack of pigment, capillaries
2. blue (cyanosis) - lack of oxygen in blood
3. yellow (jaundice) - liver disorder, protein release
IX. The Healing Process : How Skin Repairs Itself
A. Superficial Wound Healing - Epidermal Repair
1. epidermal cells of stratum basale migrate over area
2. contact inhibition - cells stop when they meet
3. dead cells sluff off (scab) as new cells replace
B. Deep Wound Healing - Dermal Repair
1. inflammatory phase - blood clot, fibroblasts
2. migratory phase - scab forms, epidermal migration
a. fibroblasts make scar tissue (collagen fibers)
b. damaged vessels grow into place
c. granulation tissue - new scar tissue in place
d. fibroplasia - period of scar fromation
i. hypertrophic scar - normal
ii. keloid scar - abnormal
3. proliferative phase - new growth
a. epithilium grows beneath scab
b. fibroblasts make random collagen deposit (scar)
c. blood vessels continue to grow
4. maturation phase - final healing process
a. epidermis is restored
b. fibroblasts disappear, collagen more organized
c. blood vessels repaired to normal
X. Skin Cancers
A. Basal Cell Carcinoma
1. Least malignant and most common skin cancer
2. Stratum basale cells proliferate and invade the dermis and hypodermis
3. Slow growing and do not often metastasize
4. Can be cured by surgical excision in 99% of the cases
B. Squamous Cell Carcinoma
1. Arises from keratinocytes of stratum spinosum
2. Arise most often on scalp, ears, and lower lip
3. Grows rapidly and metastasizes if not removed
4. Prognosis is good if treated by radiation therapy or removed surgically
C. Melanoma (most dangerous type of skin cancer)
1. Cancer of melanocytes
2. Highly metastatic
3. Resistant to chemotherapy
Melanomas have these characteristics (ABCD rule)
A: Asymmetry; the two sides of the pigmented area do not match
B: Border is irregular and exhibits indentations
C: Color (pigmented area) is black, brown, tan, and sometimes red or blue
D: Diameter is larger than 6 mm (size of a pencil eraser)
XI. Burns of the Skin
A. First-degree – only the epidermis is damaged
- Symptoms include localized redness, swelling, and pain
B. Second-degree – epidermis and upper regions of dermis are damaged
- Symptoms mimic first degree burns, but blisters also appear
C. Third-degree – entire thickness of the skin is damaged
- Burned area appears gray-white, cherry red, or black; there is no initial edema or pain (since nerve endings are destroyed)
Burns considered critical if:
- Over 25% of the body has second-degree burns
- Over 10% of the body has third-degree burns
- There are third-degree burns on face, hands, or feet