A&P: The Integumentary System

what is the epidermis?

most superficial layer of the skin, varying in thickness in different areas [thick in scalp, back, and soles of feet; thin in other areas]

what is the composition of the epidermis?

composed of several layers of cells, separated into 2 regions

• germinal layer: base of epidermis, continuously producing new cells that rise to surface; HAS A BLOOD SUPPLY

• stratum corneal layer: dead layer of the skin that the cells of germinal layer enter once they rise to surface and die; NO BLOOD SUPPLY

!!! takes 4 weeks to make the journal from germinal layer to surface

what is the dermis?

the layer of the skin below the epidermis, home to the sweat glands, sebaceous glands, and hair follicles

• has blood vessels that provide nutrients and oxygen to the skin

• has specialized nerve endings that are sensitive to environmental stimuli and respond to the stimuli, sending impulses along nerves to the brain

what are sweat glands?

glands that produce sweat to help cool the body/regulate temperature

• sweat travels from the sweat glands in the dermis, through small pores/ducts to the epidermis

what are sebaceous glands?

glands that secrete an oily substance called sebum along the hair follicles to the skin surface

• sebum seals the surface, waterproofing the skin and preventing it from drying and crying

what are hair follicles?

small organs that produce hair

• as it grows, it passes along a shaft, emerging from the epidermal surface

• connected to the hair is a muscle that pulls the hair into an erect position when triggered by stimuli [cold or fright]

what is the subcutaneous tissue layer?

layer of the skin beneath the dermis that is composed largely of fat, which serves as an insulator for the body and a reservoir to store energy

• amount varies from individual to individual

what does the subcutaneous layer do?

helps anchor the skin to the muscular and skeletal structures below it

• as we age, the loss of this layer causes the skin to wrinkle due to limited support

what areas does skin not cover?

the various openings tot he body, such as mouth, nose, anus, and vagina → instead lined with mucous membranes that provide protective barrier against bacterial invasion

• mucous membranes secrete mucus to lubricate and keep them moist

where is the continuous mucous membrane in the body?

lining the entire length of the gastrointestinal tract, from mouth to anus

what is the first major function of the skin?

protect the body in the environment

• water makes up a large portion of the body → contains delicate balance of chemical substances -→ skin is watertight to keep that balanced internal solution intact

• protects the body from the invasion of infectious organisms

what is the second major function of the skin?

regulate temperature

• cold environment → blood vessels constrict, shunting blood away from skin to decrease amount of heat radiated from surface

• hot environment → blood vessels dilate, skin becomes flushed, and heat radiates from body surface

  • sweat is secreted by sweat glands and evaporation [takes energy from the body] occurs and causes body temp to fall

  • !!! EVAPORATION MUST OCCUR for reduction of body temp

what is the third major function of the skin?

transmit info from environment to the brain

• nerve endings in skin perceive and transmit info about heat, cold, pressure, pain, and position of body in space

• skin recognizes any changes in environment AND reacts to pressure, pain, and pleasurable stimuli