BIOL2311 Integumentary system

hypodermis

layer beneath the dermis, consists of apipose or areolar connective tissue

Epidermis

stratified squamous epithelium, and dermis primarily dense irregular connective tissue.

keratinocytes

most abundant, produces a fibrous water resistant protein called keratin and are linked together by desmosomes into layers

desmosomes

Anchoring junctions that prevent cells from being pulled apart

melanocytes

produces melanin pigment granules and are responsible for the coloration of the skin; production increases with exposure to UV radiation(sunlight)

langerhans cells

macrophages that are involved in immunity

merkel cells

touch receptors cells that reside in the deepest layer of the epidermis

stratum basale (germinativum)

deepest layer of epidermis; contains most of the dividing cells

stratum spinosum

contains few dividing cells; cells in this layer begin to produce intermediate filaments of prekeratin proteins

stratum granulosum

contains cells that are thinning and filling with protein granules; as cell layers are pushed to outside they begin to die

stratum lucidum

thin translucent layer of dead cells between the stratum granulosum and stratum corneum; only present in thick skin

Stratum corneum

consists of 20 to 30 layers of dead, but fully keratinized cells; abrades constantly and is replaced by deeper layers

Dermis layers

papillary layer and reticular layer

superficial papillary layer of dermis

composed of areolar connective tissue and forms the dermal papillae

Dermal papillae

form a wavy boundary between the dermis and the stratum basale of the epidermis; contain an abundance of capillaries to supply the epidermis; contain free nerve ending and Meissner's touch corpuscles

reticular layer

contains many arteries, veins, nerves, sweat glands, sebaceous glands, and hair follicles; deep areas of the reticular layer contain Pacinian touch corpuscles; collagen and elastin fibers of the reticular and papillary layers provide structural strength to the integument.

Pacininan corpuscles

Pressure receptors found in the lower region of the dermis

Accessory structures of the skin

hair, skin glands, and nails

Nail

keratinized derivatives of the epidermis; consist of keratinized cells

Nail matrix

nail growth; formed from stratum basale

lunula

matrix visible beneath the body of the nail

hair

compressed, keratinized cells that arise from hair follicles, the sacs that enclose the hair fibers

shaft

visible part of the hair

hair follicle

sac within which each hair grows

hair bulb

base of the follicle

hair papilla

dermal tissue that extends into the base of the hair root and provides nutrition to the hair matrix

hair matrix

actively dividing area of the hair bulb that produces the hair

Melanocytes of hair

secrete melanin granules into the cortex of the hair and determine its color

hair cortex

Middle layer, hard keratin. Tapering cornified cells with pigment (gives color and connective tissue sheath around the follicle

hair medulla

innermost portion of a hair shaft

hair cuticle

Outermost layer of hair; consisting of a single, overlapping layer of transparent, scale-like cells that look like shingles on a roof.

arrector pili muscle

smooth muscle attached to the hair follicles; responds to stimuli to contract and raise hair away from skin; goosebumps

Sebaceous glands

secrete an oily substance called sebum that lubricate the shaft of the hair

sweat glands (sudoriferous glands)

open onto the surface of the skin via pores; classified by their secretion; secrete a thin solution of water, salt, and urea

Apocrine glands

secrete a milky solution of fats and proteins; concentrated in the axillary(armpits) and genital regions

Eccrine glands

found over most of the surface of the skin

Mammary glands

modified apocrine glands that secrete milk

lucanae

cavities that house chondrocytes

Chrondrocytes

Cartilage cells found in the spaces called lucunae