- regulate body temp
- water-repellent and protective barrier
- sensory information about environment
- excretes salts and organic compounds
- helps to synthesize Vitamin D
Hypodermis (subcutaneous layer)
- not part of skin
- consists of areolar and adipose tissues
- fiber anchors dermis to hypodermis, and hypodermis to fascia (connective tissue around muscles and bones)
- storage depot for fat
- has large blood vessels
- contains lamellated (pacinian) corpuscles (nerve endings sensitive to pressure)
Epidermis and Dermis Cross Section
4 cell types of epidermis
- produce keratin: tough, fibrous protein that protects skin from heat, microbes, chemicals
- most numerous epidermal cell type
- found in 4-5 layers
- produce melanin
- in deepest layer of epidermis
- mount immune response against microbes
- small fraction of epidermal cells
4) Merkel cells
- works with Merkel disc to detect pressure
- least numerous of epidermal cells
- in deepest layer of epidermis
- superficial portion that consists of areolar connective tissue with elastic fibers and dermal papillae
- contains capillary loops, corpuscles of touch, free nerve endings
- deeper portion of dermis consisting of dense irregular connective tissue with bundles of collagen and elastic fibers, adipocytes, hair follicles, nerves, sebaceous glands, and sudoriferous glands
Sebaceous gland: distribution, location (gland and duct), secretion, functions (and its onset)
Distribution: most skin surfaces except palms & soles
Location: dermis, secretes onto hair follicles or sometimes skin surface
Secretes sebum, mixture of triglycerides, cholesterol, proteins, and inorganic salts
Function: prevents hair from drying out, excessive water loss from skin, keeps skin soft, inhibits growth of some bacteria. Functions inactive during childhood, activated during puberty.
Eccrine suderiferous gland: distribution, location (gland and duct), secretion, functions (and its onset)
Distribution: throughout skin of most body regions, especially on forehead, palms & soles
Location: mostly in deep dermis (more superficial to apocrine sweat glands). Secretes onto surface of skin.
Secretes perspiration (water, ions, urea, uric acid, ammonia, amino acids, glucose, lactic acid)
Function: body temp regulation, waste removal (small role), stimulated during emotion stress. Functions after birth.
Apocrine suderiferous gland: distribution, location (gland and duct), secretion, functions (and its onset)
Distribution: skin of armpits, groin, bearded regions of face, areolae of breasts.
Location: mostly in deep dermis; secretes into hair follicle
Secretes perspiration, same as eccrine glands (water, ions, urea, uric acid, ammonia, amino acids, glucose, lactic acid), in addition to lipids & proteins
Function: stimulated during emotional stress and sexual excitement. Onset at puberty.
Ceruminous gland: distribution, location (secretory portion and termination of excretory duct, secretion, functions (and its onset)
Distribution: type of modified sweat glands located in external ear (ext auditory canal)
Location: subcutaneous layer, secretes onto surface of ear canal or into ducts of sebaceous glands.
Secretes cerumen, a waxy substance
Function: impede entrance of foreign bodies into ear canal; waterproofs canal, prevents microbes from entering cells. Functions after birth