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Skin function

- 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

1) Keratinocytes
- produce keratin: tough, fibrous protein that protects skin from heat, microbes, chemicals
- most numerous epidermal cell type
- found in 4-5 layers
2) Melanocytes
- produce melanin
- in deepest layer of epidermis
3) Langerhans
- 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

Epidermal Stratum

Dermis regions

Papillary region
- superficial portion that consists of areolar connective tissue with elastic fibers and dermal papillae
- contains capillary loops, corpuscles of touch, free nerve endings

Reticular region
- 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

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