the integumentary system

Chapter 4. The Integumentary System & Body Membranes

1) Body Membranes
a) Functions- Covers body surfaces, line body cavities, form protective sheets around organs.
b) Classification
i) Epithelial
ii) Connective tissue- Synovial membrane
c) Cutaneous = skin- Dry membrane, outermost protective boundary, superficial epidermis is composed of keratinized stratified squamous epithelium, underlying dermis is mostly dense connective tissue.
d) Mucous = digestive & respiratory interior surfaces- Surface epithelium type depends on site: stratified squamous epithelium(mouth, esophagus), simple columnar epithelium(rest of digestive tract), underlying loose connective tissue, lines all body cavities that open to the exterior body surface(digestive & respiratory systems), often adapted for absorption or secretion.
e) Serous – internal: visceral & parietal- Surface layer of simple squamous epithelium, underlying layer is a thin layer of areolar connective tissue, lines open body cavities that are closed to the exterior of the body, serous membranes occur in pair separated by serous fluids: visceral layer covers the outside of the organ, parietal layer lines a portion of the wall of ventral cavity.
i) Peritoneum-Around the abdominal
ii) Pleura-Around the lung
iii) Pericardium-Around the heart
iv) Synovial – connective tissue only, lines fibrous capsules surrounding joints, secretes a lubricating fluid.
2) The Integumentary System
a) Definition: skin and derivitives-Sweat glands, oil glands, hair, nails.
b) Structure of the Integumentary System
i) Epidermis-Outer layer: stratified squamous epithelium, often keratinized(harden by keratin).
ii) Dermis-Dense connective tissue(mainly collagen)= blisters develop between E & D).
iii) Hypodermis(subcutaneous tissue)- Is deep to tissue, not part of skin, anchors skin to underlying organs, composed mostly of adipose tissue
iv) Strata or layers of the epidermis (See Fig. 4.3)
(a) Stratum basale (germinating layer)-Deepest layer of epidermis, lies next to dermis, cells undergoing mitosis, daughter cells are puches upward to become more superficial layers.
(b) Stratum spinosum (prickly layer)- Becoming more squamous.
(c) Stratum granulosum (granular layer)-Becoming imbedded with keratin.
(d) Stratum lucidum (clear layer)-Formed from dead cells of the deeper strata, occurs only in thick, hairless skin of the palms of hands and soles of feet.
(e) Stratum corneum (horny layer)- Outermost layer of epidermis, ¾ of its thickness, shingle-like dead cells are filled with karatin(protective protein prevents water loss from skin)
v) Melanin(pigment)- Produced by melanocytes. Melanocytes are mostly in the stratum basale, color is yellow to brown to black, amount of melanin produced depends upon genetics and exposure to sunlight. Albino=no melanin.
(1) The Dermis (See Fig. 4.4)
(2) Characteristics-Collagen and elastic fibers located throughout the dermis.
(3) Layers of the dermis
vi) Papillary layer(upper dermal region)= projections called dermal papillae, some contain capillary loops, other house pain receptors and touch receptors.
vii) Dermal papillae
viii) Reticular layer(deepest skin layer)= blood vessels, sweat and oil glands, deep pressure receptors.
(1) Collagen & elastic Collagen=toughness, Elastic= elasticity.
(2) Blood vessels-Play a role in body tempurature
ix) Hypodermis
3) Skin Color
a) Pigments
i) Melanin-Yellow, brown, or black pigments
ii) Carotene-Orange-yellow pigment from some vegetables
iii) Hemoglobin-Red coloring from blood cells in dermal capillaries, oxygen content determines the extent of red coloring

4) Appendages of the skin
a) Glands (See Fig. 4.6)
i) Sebaceous or oil glands-Produce oil: lubricant for skin, prevents brittle hair, kills bacteria, most ducts that empty into hair follicles; others open directly onto skin surface, glands are activated at puberty.
(1) Sebum
ii) Sweat glands-Produce sweat, widely distributed in skin. Odor is from breakdown by associated bacteria. Two types:
(1) Merocrine or ecrine-Open via duct to pore on skin surface, all over body, produce sweat.
(2) Apocrine-Ducts empty into hair follicles, axillary & genital areas, mysterious
(3) Composition-Mostly water, salts and vitamin C, some metabolic waste, fatty acids and proteins(appocrine only)
(4) Function-Helps dissipate excess heat, excretes waste products, acidic nature inhibits bacteria growth.
(5) Ceruminous glands
(6) Mammary glands
b) Nails (See Fig. 4.9)-Scale-like modifications of the epidermis, heavily keratinized. Stratum basal extends beneath the nail bed=responsible for growth, lack of pigment makes them colorless. Free edge,body is the visible attached portion, root of nail embedded in skin, cuticle is the proximal nail fold that projects onto the nail body.
i) Nail bed
ii) Nail matrix
iii) Nail folds
c) Hair (See Fig. 4.7)-Produced by hair follicle, consists of hard keratinized epithelial cells, melanocytes provide pigment of hair color.
i) Structure
(1) Root
(2) Shaft
ii) Arrector pili muscle-Smooth muscle, pulls hair upright when cold or frightened.
iii) Concentric layers
(1) Medulla
(2) Cortex
(3) Cuticle
iv) Hair follicle (See Fig. 5.5)-Dermal and epidermal sheath surround hair root.
(1) Hair bulb
(2) Root hair plexus
(3) Hair papilla
(4) Hair mat
v) Hair thinning and baldness – genetic trait
5) Infections
a) Athlete’s foot(tinea pedis)- Caused by fungal infection
b) Boils & carbuncles-Caused by bacterial infection
c) Cold sores-Caused by virus
d) Contact dermatitis-Exposures cause allergic reaction
e) Impetigo-Caused by bacterial infection
f) Psoriasis-Cause is unknown…autoimmune? Triggered by trauma, infection, stress.
6) Burns-Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals. Associated dangers: dehydration, electrolyte imbalance, circulatory shock.
a) Effect
b) Rule of nines- Way to determine the extent of burns. Body is divided into 11 areas for quick estimation, each area represents about 9% of total surface area.
c) Classification of burns
i) First degree-Only epidermis is damaged, skin is red and swollen.
ii) Second degree-Epidermis and upper dermis are damaged, skin is red with blisters.
iii) Third degree-Destroys entire skin layer, burn is gray or white.
iv) Critical burns-Over 25% of body has second degree burn, over 10% of body has ten degree burns, there are third degree burns on face, hands, or feet.
7) Skin cancer(is the most common type of cancer.
a) Defined-Abnormal cell growth.
b) Abnormal cell mass
i) Benign-Does not spread(encapsulated).
ii) Malignant-Metastasized(moves) to other parts of the body.
c) Types
i) Basal cell carcinoma-Least malignant(dangerous), most common type, arises from stratum basale.
ii) Squamous cell carcinoma-Metastasizes to lymph nodes if not removed, early removal allows a good chance of cure, believed to be sun included, arises from stratum spinosum
iii) Melanoma-Most deadly of skin cancers, cancer of melanocytes, metastasizes rapidly to lymph and blood vessels, detection uses ABCD rule.
d) ABCD rule
i) A = asymmetry-Two sides of pigmented mole do not match.
ii) B = border irregularity-Borders of mole are not smooth.
iii) C = color-Different colors in pigmented area.
iv) D = diameter-Spot is larger than 6 millimeter(mm) in diameter.