BSCI201 - Integumentary System

What are the layers of the epidermis

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

stratum basale (basal layer)

deepest layer of epidermis

• single layer of cells (keratinocytes, melanocytes, Merkel cells)

Merkel cells

function as touch receptors in association with sensory nerve endings

• located at epidermal-dermal junction

Melanocytes

cells that produce melanin and protect UV against radiation

stratum spinosum (spiny layer)

several layers of cells connected with desmosomes

• contain tonofilaments that resist tension

• appear spiny under microscope

• contains Langerhan's cells

Langerhans cells

epidermal macrophages that help activate the immune system

stratum granulosum (granular layer)

3-5 layers of cells that contain two types of granules

• lamellated granules and keratohyaline granules

lamellated granules

contain a waterproofing glycolipid

keratohyaline granules

contains tough, insoluble proteins

makes epidermis tough and abrasive resistant

Stratum lucidum (clear layer)

Only in thick skin (palms, soles)

• thin, translucent layer of dead cells

• thickens epidermis

Stratum corneum (horny layer)

most superficial layer; dead cells filled with keratin (barrier area)

• 20-30 layers

• cornification (waterproofing)

cornification (keratinization)

dead cells are filled with glycolipids and keratin to make a tough waterproof coating (superficial layer)

Dermis

middle layer of skin, consists of papillary and reticular layers

papillary layer

superficial layer of dermis

• made of loose, areolar CT

• surface projections called papillae

papillae

house blood capillaries, nerve endings, and Meissner's corpuscles (touch receptors)

• thick skin --> surface of papillae supported by dermal ridges (causes fingerprints and enhances friction)

reticular layer

deep layer of dermis

• made of dense irregular CT

• contains Pacinian corpuscles (deep pressure receptors)

cleavage tension lines

areas of the reticular layer w/ less collagen bundles

*important for incisions

Striae

Stretch marks; Linear dermal scars that affects skin that is subjected to continuous stretching

Root hair plexus location

wrapped around the base on the hair follicle called bulb, stimulated when hair bends

Accessory structures of the skin

hair, skin glands, and nails

• all derived from the stratum basale but reside in dermis

Sweat glands (sudoriferous glands)

simple, coiled, tubular, multicellular exocrine glands

eccrine sweat glands (merocrine)

abundant in palms, soles, and forehead (3mil per person)

• secrete sweat for thermoregulation

• use merocrine mode of secretion

composition of sweat

99% water

• also contains antibodies, Vit. C, NaCl, dermicidin, metabolic waste

is sweat acidic or basic

acidic (pH 4-6)

What is the sweat acid mantle

combination of acidic sweat and dermicidin to push away microbial growth

Where are appocrine sweat glands located?

Armpits and genital areas (2000)

Appocrine sweat glands

sweat glands only active after puberty; secrete a milky sweat with lipids and proteins

ceruminous glands

produce ear wax (cerumen)

mammary glands

sweat glands that secrete milk

Oil glands (sebaceous)

simple, branched alveolar multicellular exocrine glands

• located everywhere except palms and soles

• holocrine mode of secretion

What do sebaceous glands secrete?

sebum (oil)

holocrine mode of secretion

accumulate products within, then rupture (sebaceous oil glands)

hair

pilli

• produced by cells in the matrix inside follicles

• functions for thermoregulation, protection

2 regions of hair

shaft and root

Explain thermoregulation with hair

In cold temps --> arrector pilli muscle cause goosebumps

• hair insulates the skin

Nails

horny plates made from flattened keratinized epithelial cells, tightly packed cells

Nail body

visible part of the nail

• free edge extends past finger (white part)

Nail root

the portion of a nail that is buried in a fold of skin

Lanula

crescent shaped area of nail body near cuticle

Hyponychium

secures the nail to fingertip

• thickened stratum corneum

cuticle (eponychium)

narrow bond on epidermis

Where does nail growth occur

nail matrix

basal cell carcinoma

proliferation of keratinocytes in stratum basale

• least malignant, grows slowly, common

squamous cell carcinoma

proliferation of cells in the stratum spinosum

• 2nd most common, grows faster than carcinoma

melanoma

proliferation of melanocytes

• very agressive, highly metastic and resistant to chemo

What is ABCD

A (asymmetry); B (border); C (color change) D(diameter bigger than eraser)

Burns

Tissue damage from heat, chemicals, or radiation.

1st degree burn

damage only to the epidermis

• heals within 3 days, sunburn

2nd degree burn

damage to entire epidermis and papillary layer of dermis

• blisters (fluid in epidermal-dermal junction), heals within 3-4 weeks

3rd degree burn

Full thickness damage through skin into nerves and muscles

Rule of Nines (burns)

Used to guide treatment decisions for burns

• divides the body into regions of 9%

autograft

obtained from another part of the body

allograft

skin graft from another person or a cadaver (usually temporary)

xenograft

a graft from another species (usually temporary and usually pigs)

artificial skin grafts

skin substitutes created in the laboratory that contain components of donated skin tissue that is more useful because it will not be rejected by the body

Wrinkles

form from loss of elasticity, lack of moisture and thinning

• skin adheres to underlying muscle tissue as it thins

How does Botox reduce wrinkles?

blocks transmission of signals from nerves to muscles

• hinders release of neurotransmitter