Chapter 4: Skin and Body Membranes

Body Membranes

Cover surfaces, line body cavities, and form protective sheets around organs. Classified according to tissue makeup. Epithelial and Connective tissue membranes.

Epithelial membranes

Cover and line body parts, contain epithelial tissue with underlaying layer of connective tissue.

cutaneous membrane

skin. dry and exposed to air. stratified squamous over fibrous CT.

Mucous Membranae

lines body cavities open to the exterior. Organs of respiratory, digestive, urinary, and reproductive tracts, continuously bathed in mucous. Epithelium over loose CT.

Serous Membrane

Lines body cavities closed to the exterior. walls of ventral body cavity, outer covering of organs. Simple squamous over areolar CT. two layers.

Parietal layer

outermost layer

visceral layer

hugs the organ

serous fluid

clear fluid separating the parietal and visceral layers

peritoneum

lines the abdominal cavity and the abdominal organs

pleura

surrounds lungs

pericardium

surrounds the heart

connective tissue membranes

formed of only CT. hold organs in place and line moveable joints.

Synovial membranes

line capsules surrounding joints, provide smooth surface and cushioning between moving bones. soft areolar CT. produce synovial fluid.

Integumentary system

composed of skin, hair, nails, and sweat and oil glands. largest organ. insulation, cushions and protects deeper organs. protection from mechanical, chemical, thermal, and ultraviolet damage.

epidermis

outermost layer of the skin, made of stratified squamous. 5 layers (strata). avascular.

keratin

fibrous protein in epithelial cells, makes the epidermis tough and waterproof.

keratinocytes

cells that make keratin

5 stratum basale

deepest layer, connected to dermis, contains actively diving cells. receive nutrients from the dermis.

4 stratum spinosum

living cells with thick bundles of filaments and keratin

3 stratum granulosum

cells that are flattened with deteriorating organelles.

2 stratum lucidum

clear layer, not in all skin regions. protection and waterproofing. palms, fingers, and feet. all dead cells.

1 stratum corneum

flattened membranes filled with keratin. replaced daily. 20-30 cell layers.

epidermal dendritic cells

special immune cells scattered through the epidermis, activate the immune system to threats like bacterial or viral infection.

melanin

pigment, yellow, brown, black, protects DNA in skin cells.

melanocytes

cells that produce melanin, found in stratum basale. stimulated by sunlight. accumulates in vesicles called melanosomes. taken up by keratinocytes and transferred to skin cells. forms umbrella on top of cells to cover nucleus.

dermis

layer of CT deep to the epidermis. varies in thickness; thick on palms, light on eyelids; mostly collagen and elastic fibers. needed for hydration, elasticity. decreases with age. rich nerve supply. abundance of blood vessels. helps with temperature regulation.

papillary layer

top layer of dermis

dermal papillae

projection that cause indentations in the epidermis above. arranged in definite patterns on hands and feet, fingerprints. enhance friction and grip.

reticular layer

contains blood vessels, sweat and oil glands, and phagocytes to stop spread of bacteria

subcuatneous tissue

adipose, anchors skin to underlying organs, not part of skin. shock absorption, fat storage, insulation from extreme temperature changes

merkel cells

respond to light pressure, shapes, and edges. found in stratum basale. connected to sensory nerves.

meissner corpuscle

respond to pressure. throughout skin mainly in dermal papillae just under dermis

ruffini corpuscle

respond to sustained pressure and skin stretch. between dermal papillae and hypodermis

pacinian corpuscle

respond to texture. found in hypodermis.

thermoreceptors

respond to temperature. found throughout skin.

nociceptors

sensory neurons, detect pain. found throughout skin.

three pigments that contribute to skin color

melanin, carotene, and hemoglobin

carotene

orange-yellow; in foods like oranges, and deep yellow fruits and vegetables; leafy green vegetables

hemoglobin

red, in RBC in dermal blood vessels

redness

embarrassment, allergy, fever, inflamation

blanching

pale, fear, low BP, impaired blood flow, anemia

skin cancer

various skin changes

skin appendages

accessory structures that arise from the epidermis. each has a unique role in maintaining homeostasis. glands, hair, nails.

exocrine glands

release secretions to the surface of skin through ducts. grow out of epidermis. formed by cells in the stratum basale. extend deep into and reside almost entirely in dermis.

sebaceous glands

empty secretions into hair follicle or directly to surface of skin. found all over the skin except for palms of hands and sole of feet.

sebum

oily substance and cell fragments. keeps the skin soft. prevents hair from becoming brittle. kills bacteria

sweat glands

produce sweat. two kinds.

eccrine glands

empty sweat directly to surface of skin

apocrinen glands

larger, empty into hair follicles. in areas abundant with hair

sweat

clear secretion primarily made of water, salts, and waste. important for heat regulation. glands produce sweat. sweat evaporates and carries body heat away

hair

thread-like, flexible epithelial structure made of keratine and dead keratinized cells. fastest growing tissue. insulation. some protective functions like nose hair and eyebrows.

hair follicle

tube-like structure that produces and maintains hair growth

arrector pili

smooth muscle attached to hair follicles, contraction pulls hair upright

nails

keratinized, scale-like modification of the epidermis. root is embedded in skin

open wound

produce breaks in the skin and expose the body to the external enviroment

abrasions

scraping the epithelium. May cause slight bleeding.

incisions

linear cut, may require stitches, caused by sharp objects

lacerations

jagged and irregular tear from an irregular object, may cause tissue damage.

punctures

pierce to skin, may have little bleeding, serious risk of infection.

avulsion

chunks of tissue torn away by force, serious internal damage may occur.

closed wounds

injury of internal tissue, epithelium stays in tact

contusion

bruise, bleeding in dermis. blood collects in underlying tissue

boils

bacterial infection. usually caused by staph, causes inflamation of hair follicles and sebaceous glands.

impetigo

bacterial infection. highly contagious staph or srep infection. common in children. causes pink raised lesions on face, arm, and legs.

cellulitis

bacterial infection. secondary skin infection caused by staph or strep. affects dermis and underlying tissue. can spred to other body parts.

chicken pox

viral infection. caused by varicella virus. causes blister-like rash. virus stays in body permanently

shingles

viral infection. reactivation of varicella. common in adults who had chicken pox. affects the skin and nerves.

hand foot and mouth

caused by enterovirus, highly contagious and common in children. flat discolored bumps that may blister on hands feet and mouth

ringworm

fungal infection. highly contagious. caused by direct contact with fungus. causes scaly red bumps in circular pattern.

athletes foot

fungal infection. highly contagious. causes scaly rash, itching, burning, and peeling skin.

scabies

parasitic infection. mites that burrow and lay eggs under the skin. contagious. causes scaly swelling of the skin.

pediculosis

parasitic infection. lice. causes intense itching and small patches of crust and blood.

contact dermatitis

exposure to chemicals that provoke allergic reaction. itching, redness, and swelling.

psoriasis

chronic overproduction of skin. causes red dry scales and lesions that itch, burn, and crack. common on scalp, back, neck, and knees. immune system attacks healthy cells and causes inflamation. flare ups caused by injury, infection, stress