A&P - 5.2 Accessory Structures of the Skin

structures of the skin

• epidermis

• dermis

  • cutaneous vascular plexus

• hypodermis

  • adipose tissue

• accessory organs of skin

  • sensory nerve fiber

  • pacinian corpuscles

  • hair follicle

  • hair root

  • hair follicle receptor

  • hair shaft

  • arrector pili muscle

  • sebaceous (oil) gland

  • eccrine sweat gland

  • pore of sweat gland duct

accessory organs of skin

• nerve fibers and corpuscles

• hair follicles, hair shafts, and arrector pili muscles

• glands, arteries, veins, and lymph vessels

• nails

cutaneous vascular plexus

network of blood vessels within the skin that nourishes and supports the skin’s layers and structures

hair

• keratinous filament growing out of the epidermis

• found almost everywhere on the body

  • except palms of hands, soles of feet, side of fingers, and toes, lips, and parts of external genitalia

• body has about 2.5 million hairs

  • 75 percent on general body surface (not on head)

• nonliving structures

• FUNCTION: sensory input and protection from UV rays

• each hair produced by a hair follicle

associated structures of hair

• hair follicle

• hair follicle receptor

• hair shaft

• hair root

hair follicle

cavity or sac from which hair originates

hair follicle receptor

• a sensory nerve ending, called a hair plexus, that wraps around the base of a hair follicle, allowing for the sensation of touch

• sensory input; you feel a bug land on you even though its not touching your skin, or you’ll feel a breeze

hair shaft

• part of hair that is above the epidermis but is not anchored to the follicle

• layers of the hair shaft:

  • medulla

  • cortex

  • cuticle

medulla

in hair, the innermost layer of keratinocytes originating from the hair matrix

cortex

in hair, the second or middle layer of keratinocytes originating from the hair matrix

cuticle

in hair, the outermost layer of keratinocytes originating from the hair matrix

hair root

part of hair that is below the epidermis anchored to the follicle

glassy membrane

layer of connective tissue that surrounds the base of the hair follicle, connecting it to the dermis

types of hair

• terminal hairs

• vellus hairs

terminal hairs

• large, coarse, darkly pigmented

• examples: hairs found on scalp or in armpit

vellus hairs

• smaller, shorter, delicate

• found on general body surface

arrector pili muscle

smooth muscle that is activated in response to external stimuli that pull on hair follicles and make the hair “stand up”

accessory glands

• skin has 5 types of glands:

  • merocrine sweat glands

  • apocrine sweat glands

  • sebaceous glands

  • ceruminous glands

  • mammary glands

pore of sweat gland duct

small opening on the surface of the skin where sweat, produced by the sweat gland, is released

sudoriferous glands

• sweat glands:

  • eccrine (merocrine)

  • apocrine

eccrine (merocrine) sweat gland

• hypotonic sweat

• thermoregulation

• all over skins surface

• water, salt, antibodies, metabolic waste, dermicidin

apocrine sweat gland

• hair follicles in axillary and genital regions

• water, salts, organic compounds

• waxy sweat

sebaceous gland

• oil gland found in the dermis

  • sebum (oil on skin)

  • lubrication of skin and hair

  • antibacterial properties (sweat and oil are antimicrobial)

  • water retention

  • keeps skin and hair from becoming dry, brittle, and cracked

  • lanolin - sheep sebum

sebum

oily substance that is secreted from sebaceous glands that is composed of a mixture of lipids that lubricates the skin and hair

ceruminous glands

• simple, coiled, tubular glands in external ear canal

• this secretion combines with sebum and dead epithelial cells to form earwax (cerumen)

  • keeps eardrum pliable

  • waterproofs the canal

  • kills bacteria

  • makes guard hairs of ear sticky to help block foreign particles from entering auditory canal

mammary glands

milk-producing glands located in the breasts

nails

• form from thickened epidermal cells nestled into the dermis forming a nail field

• FUNCTION: protection and back-support for picking up small objects

accessory structures of the nails

• free edge

• nail

• lateral nail fold

• lunula

• eponychium

• proximal nail fold

free edge

the hard, white part of the nail that extends beyond the fingertip

nail body (nail)

main keratinous plate that forms the nail

nail fold

• fold of the epithelium that extends over the sides of the nail body, holding it in place

• lateral nail fold overlaps the nail of the sides, helping to anchor the nail body

• proximal nail fold at the end of the nail body form the nail cuticle

lunula

basal part of the nail body that consists of a crescent-shaped layer of thick epithelium

eponychium

nail fold that meets the proximal end of the nail body, also called the cuticle

nail bed

layer of epidermis upon which the nail body forms

nail root

part of the nail that is lodged deep in the epidermis from which the nail grows

hyponychium

thickened layer of stratum corneum that lies below the free edge of the nail