The Integumentary System
Chapter 6
• Organs are two or more tissues which
together perform a specialized function.
• Epithelial membranes are thin structures
that usually contain both epithelial and
connective tissue.
Three types of epithelial
membranes
• Serous Membranes
– Line cavities and cover organs
– Simple squamous epi. over loose connective
tissue
– Parietal and visceral portions
– Secrete a serous (watery) fluid for lubrication
• Mucous membranes
– Line cavities that open to the exterior
– Layer of epithelium over connective tissue;
epithelium varies with location
– Tight junctions and goblet cells
• Cutaneous membrane is the skin
– the major organ of the integumentary system
• 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. Sensation
touch
vibration
pain
temperature
4. Excretion
5. Immunity/ Resistance
6. Blood Reservoir
8-10 % in a resting adult
7. Synthesis of vitamin D
uv light
aids absorption of calcium
Anatomy
• Epidermis
Skin
• Dermis
• Subcutaneous layer or hypodermis
Epidermis
• Stratum basale (stratum germinativum)
– 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
– See spines when cell is stained for
microscopy
– Keratinocytes take in melanin by cytocrine
secretion
• Stratum granulosum
– 3-5 layers
– Keratinization begins here
– Keratohyalin found in granules
– Cells beginning to die
• Stratum lucidum (lucid = clear)
– More apparent in thick skin
– 3-5 layers of clear cells
– Eleidin
• Stratum corneum (corneum means horny)
– Dead, flat cells full of keratin
– Keratin is waterproof
– Cells are shed
• Basal cell to surface – about 2-4 weeks
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
– Sebaceous (oil) glands
– Hair follicles
– Ducts of sudoriferous (sweat) glands
– Striae or stretch marks
– Meissner’s corpuscles and Pacinian
corpuscles
Hypodermis
• Attaches the reticular layer to the
underlying organs
• Loose connective tissue and adipose
tissue
• Major blood vessels – rete cutaneum
Accessory organs or epidermal
derivatives
• Hairs
– Epidermal growths that function in protection
– Shaft, root, and folllicle
– Sebaceous glands, arrector pili muscle, and
hair root plexus (touch)
– Hair growth and replacement have a cyclical
pattern
– ‘male-pattern’ baldness
Nails
• Plates of highly packed, keratinized cells
• Protection, scratching, & manipulation
• Formed by cells in nail bed called the
matrix ( in area of lunula)
• 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
• Sweat (sudoriferous) glands
– Eccrine sweat glands
• Merocrine glands
• Water, salt, wastes
• Function is to cool the body (also nervous)
– Apocrine sweat glands
•
•
•
•
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
Skin color
• Genetic factors
– Same number of melanocytes
– Albinism
• Environmental factors
– Uv light or x-rays
• Physiological factors
– Amount of blood
– Amount of oxygen
• Cyanosis
• Carotene accumulation
• Jaundice – liver disorder
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
– keloid
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
• Rule of Nines