Download The Integumentary System

The Integumentary System
Chapter 5
• Integumentary system is the skin and the
organs derived from it (hair, glands, nails)
• One of the largest organs
– 2 square meters; 10-11 lbs.
– Largest sense organ in the body
• The study of the skin is Dermatology
Functions:
1. Regulation of body temperature
– Cellular metabolism produces heat as a
waste product .
– High temperature
• Dilate surface blood vessels
• Sweating
– Low temperature
• Surface vessels constrict
• shivering
2. Protection
physical abrasion
dehydration
ultraviolet radiation
3. Synthesis and Storage of Nutrients
4. Sensation
touch
vibration
pain
temperature
4. Excretion/ Secretion
5. Immunity/ Resistance
6. Blood Reservoir
8-10 % in a resting adult
Epidermis
Anatomy
• Epidermis
Skin
• Dermis
• Subcutaneous layer or hypodermis
Epidermis
• Stratum Germinativum (stratum basale)
– Single layer of cuboidal to columnar cells
– Stem cells that produce keratinocytes
– Melanocytes - # the same for all races
• Melanin produced in a melanosome
• Stratum spinosum (thorn-like, prickly)
– 8-10 layers attached by desmosomes
• Stratum granulosum
– 3-5 layers
– Keratinization begins here
• Stratum lucidum (lucid = clear)
– 3-5 layers of clear cells
– Eleidin
• Stratum corneum
– Dead, flat cells full of keratin
Skin Color
• Pigmentation
– Carotene- an orange-yellow pigment that
normally accumulates in epidermal cells.
• (i.e. carrots and squashes)
– Melanin- a brown, yellow-brown pigment
produced by melanocytes.
Skin Cancer
• Most common form of cancer
• Malignant Melanoma- extremely
dangerous.
• The outlook for long term survival depends
on when the condition is detected and
treated
• Dermal Circulation
– Blood with abundant oxygen is bright red,
gives skin a reddish tint.
– When vessels are dilated, as during
inflammation, the red tones become much
more pronounced.
– When the vessels are temporarily consricted,
as when you are frightened, the skin becomes
pale.
Dermis
• Connective tissue layer
• Collagen and elastic fibers, nerves, blood
vessels, muscle fibers, adipose cells, hair
follicles and glands.
• Papillary layer
– 1/5 of dermis – loose areolar connective
tissue
– Highly vascular
– Dermal papillae - fingerprints
• Reticular (net) layer
– Dense irregular connective tissue
– Both elastic fibers and collagen fibers are
present
• Other Dermal Components
– Sebaceous (oil) glands
– Hair follicles
– Ducts of sudoriferous (sweat) glands
– Striae or stretch marks
Subcutaneous Layer
(Hypodermis)
• Attaches the reticular layer to the
underlying organs
• Boundary between dermis and
hypodermis is indistinct
• Consists of loose connective tissue and
adipose tissue (“baby fat”)
• Major blood vessels and lack of vital
organs makes useful method for
administering drugs.
Accessory organs or epidermal
derivatives
• Hair and Hair Follicles
• Structure:
– Hair papilla- peg of connective tissue
containing capillaries and nerves.
– Hair root- the portion that anchors the hair into
the skin
– Hair shaft- the part we see on the surface
• Hairs grow and are shed according to a
hair growth cycle based on the activity
level of hair follicles.
• Hair in the scalp grows for 2-5 years at a
rate of about .3mm per day.
• Hair Functions:
– Protection from UV light
– Insulation
– Entry of foreign particles
– Touch and sensation
– Arrector pilli- “goose bumps”
Nails
• Plates of highly packed, keratinized cells
• Protection, scratching, & manipulation
• Formed by cells in nail bed called the
matrix ( in area of lunula)
• Grows about 1 mm / week
• Eponychium - cuticle
Skin Glands
• Sebaceous (oil) glands
– Usually connected to hair follicles
– Holocrine glands
– Fats, cholesterol, proteins, salts, and cell
debris
– Moistens hair and waterproofs skin
– Sebum- lubricates the hair and skin and
inhibits growth of bacteria
• Sweat (sudoriferous) glands
– Merocrine (eccrine) sweat glands
• merocrine glands
• Secrete water, salt, wastes
• Function is to cool the body (also nervous)
– Apocrine sweat glands
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•
•
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Larger, merocrine glands
Associated with hair follicles
More viscous – fatty acids and proteins
Odor occurs when broken down by bacteria
• Ceruminous glands
– Modified sudoriferous glands
– Secrete cerumen (ear wax)
• Mammary glands
– Secrete milk
Wound healing
• Inflammation
– Blood vessels dilate and become permeable
• Heat, redness, swelling and pain
• Shallow cuts
– Epithelial cells migrate
– Contact inhibition
Deeper wounds
• Inflammatory phase
– Fibrin forms clot
• Migratory phase
– Fibroblasts make granulation tissue
• Proliferative phase
• Maturation phase
• Scars – hypertrophic scar
Burns
• First degree or partial thickness burn
– Only epidermis is damaged
– Erythema, mild edema, surface layer shed
– Healing – a few days to two weeks
– No scarring
• Second degree- deep partial-layer burn
– Destroys epidermis
– Blisters form
– Healing depends on survival of accessory
organs
– No scars unless infected
• Third degree or full-thickness burn
– Destroys epidermis, dermis and accessory
organs of the skin
– Healing occurs from margins inward
– Skin grafting may be needed
• Autograft
• Homograft