Integumentary System

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

Dermis

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)

Thermoregulation

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