Layers of the Integument
Epidermis - composed of Stratified-Squamous-Epithelium connected by a Basement-Membrane
functions to control skin-permeability, provide a barrier to pathogens, and to synthesize vitamin-D.
strata of epidermis
Stratum-Basale (Germinativum) - mitotically active
Stratum-Spinosum - cells attached by spine like projections
Stratum-Granulosum - keratinization begins here
Stratum-Lucidum - nuclei and organelles disappear
Stratum-Corneum - dead cell residue and Keratin
functions to nourish epidermis, restrict and destroy pathogens, store lipids, attach skin to underlying tissue, provide for sensory-detection, assist in thermoregulation by way of blood vessels.
Papillary-Layer - composed of Loose-Connective-Tissue
Dermal-Papillae - extensions into epidermis (cause Ridges)
contain many Blood-Capillaries and Lymphatic-vessels
contain Meissner's-Corpuscles for detecting light-touch
Reticular-Layer - composed of Dense-Irregular-Connective-Tissue
contain Blood-Vessels, Lymph-Nodes and Lymphatic-Vessels
contain Pacinian-Corpuscles for detecting deep-pressure
Hypodermis (Subcutaneous-Layer) - composed of Adipose-Tissue
functions to provide cushioning and storage of fat.
contains loose connective tissue and blood vesels
Epidermal-Derivatives (Accessory Structures)
Hair-Follicles - originate from the epidermis
functions to protect skull and to assist in sensory detection.
Hair-Shaft and Root - exposed and deep portions of hair
Arrector-Pili-Muscles - Smooth-Muscle connecting to hair follicle
function to straighten hair.
Sebaceous-Glands (Oil-Glands) - associated with hair follicles
function to lubricate and protect hair shaft and surrounding skin
secrete sebum (mainly a lipid) into hair follicles
anatomically are simple-branched-acinar-glands
functionally are Holocrine-Glands (whole cell secretion)
Merocrine-Sweat-Glands - associated with epidermis
function to excrete salts, water, and organic-wastes.
secrete sweat onto surface of epidermis
anatomically are simple-coiled-tubular-glands
functionally are Merocrine-Glands (transmembrane)
by increasing blood flow in dermis heat is disipated
by increasing perspiration heat is disipated
sensible perspiration is from sweat glands
insensible perspiration is from leakage from capillaries
© David G. Ward, Ph.D. Last modified by wardd 23 May, 2006