Integumentary system

What are the 3 layers of the skin?

Epidermis, dermis, subcutaneous layer

Epidermis

Outermost layer composed of epithelium & first layer of protection

Dermis

Composed of connective tissue, smooth muscle, and nerve fiber

Subcutaneous

Composed of areolar and adipose connective tissues that acts as a shock absorber and insulator

Stratum basale

Deepest layer, single layer of cuboidal/columnar cells, keratinocytes & melanocytes

Stratum spinosum

2nd deep layer, several layers thick, provides structural strength and flexibility.

Stratum Granulosum

3rd deepest layer, 3-5 layers thick, Flattened keratinocytes undergoing cell death, marked by dark-staining keratohyalin granules, and lamellar granule

Stratum Lucidum

4th layer, 2-3 thin clear layers, filled with eleiden

Stratum Corneum

Most superficial layer, 15-30 dead keratinized cells,

What layer does skin color originate from?

Stratum Basale

Melanin

Only pigment made in the skin and delivered to keratinocytes within melanosomes.

Carotene

Yellow/orange pigment that accumulates in the stratum corneum & fatty

tissues of the hypodermis

What are the 2 layers of the dermis?

Papillary and Reticular layer

Papillary Layer

Located near the superior surface made of areolar connective tissue, has dermal papillae - small projections indenting into epidermis

Reticular layer

Dense irregular connective tissue with mostly collagen fibers running parallel to the skin surface, highly vascularized and innervated, and possesses flex lines

What are the functions of the epidermis?

Responsible for protection, water loss prevention, metabolic regulation, secretion, absorption, and immunity

What are the functions of the dermis?

Temperature regulation and sensory reception

Nail

Scalelike modifications of the stratum corneum compromised of hard keratin

Hair

Flexible strands of dead keratinized cells produced by the hair follicle

Lanugo hair

Fine, downy hair found on a fetus (third trimester)

Vellus hair

Fine, pale body hair

Terminal hair

Darker, thicker hair located on the head, axillary & pubic regions

Shaft

Projects above the skin surface composed of dead epithelial cells

Root

Lies below the skin surface composed of dead epithelial cells

Hair bulb

Region at the base of the hair follicle, located deep in the dermis, and consists of living epithelial cells

Hair papilla

Possessing capillaries supplying nutrients and nerves and contain hard keratin proteins

Medulla

Innermost portion, loosely arranged cells containing soft, flexible keratin and air pockets.

Cortex

External to the medulla and several layers of flattened cells

Cuticle

Outer layer consisting of a single layer of cells

Arrector pili muscle

Responsible for contraction of the hair follicle

Function of Hair

Protection, Heat retention, Sensory reception, Visual identification, Chemical signal dispersion

Anagen

Active phase, Producing new hairs, Pushes club hair out of follicle

Catagen

Regression phase, Involution of the hair foillicle

Telogen

Resting phase for the follicle, Hair is shed

Merocrine sweat glands

Abundant on palms, soles, & forehead, Emotionally-induced sweating, Thermoregulation, Excretion, Protection

Apocrine sweat gland

Located in axillary & anogenital regions, Secretions are odorless but when decomposed by bacteria on the skin = body odor,

Precise function is unknown, but activity begins in puberty

Sebaceous glands

Secrete an oily substance called sebum stimulated by hormones, Secretions soften and lubricate hair and skin, Prevent excessive water loss and bacterial growth

Regeneration

Replacement of destroyed tissue with the same kind of tissue, Restores organ function

Fibrosis

Replaces lost cells with collagen fibers (& fibroblasts) resulting in scar tissue, Some structural restoration, but no functional restoration

Step 1 of wound healing

Clotting proteins and thrombocytes hold the sides of the wound together

Step 2 of wound healing

Clot stops blood flow and protects damaged tissue, Immunocytes remove cellular debris and pathogens internal to the clot

Step 3 to wound healing

Blood vessels regrow into the wound, Fibroblasts in the granulation tissue proliferate, Macrophages remove old tissue and clot material

Step 4 of wound healing

Surface epithelium grows and migrates under the scab, Fibrous tissue (granulation tissue) matures and contracts