Hole's Human Anatomy and Physiology - Chapter 6

organ

two or more kinds of tissues grouped together and performing specialized functions

Integumentary system function

- composed of several tissue types

- maintains homeostasis

- protective covering

- retards water loss

- regulates body temperature

- houses sensory receptors

- contains immune system cells

- synthesizes chemicals

- excretes small amounts of wastes

Epidermis

- outer layer

- stratified squamous epithelium

dermis

- inner layer

- contains collagenous and elastic fibers

subcutaneous layer (hypodermis)

- beneath dermis

- areolar and adipose C.T

Epidermis

- stratified squamous epithelium

- keratinized

- rests on basement membrane

- lacks blood vessels

- melanocytes provide melanin

Epidermis thickest

on palms and soles (0.8-1.4mm)

Five layers of epidermis (top to bottom)

- stratum corneum

- stratum lucidum

- stratum granulosum

- stratum spinosum

- stratum basale

Stratum corneum

dead keratinized cells

Stratum lucidum

only in thick skin-palms, soles

Stratum basale

mitotic layer

keratinization

process that happens as cells move up from basement layer - drying out

Melanocytes

- located in the stratum basale

- produce the dark pigment melanin

Melanin

- gives skin color

- also absorbs UV light

Genetic factors that affect skin color

- varying amounts of melanin

- varying size of melanin granules

- albino lack melanin

Environmental factors that affect skin color

- sunlight

- UV light from sunlamps

- x-rays

Physiological factors that affect skin color

- dilation of dermal blood vessels (blush)

- constriction of dermal blood vessels (cold, shock, sick)

- accumulation of carotene (pigment in plants)

- jaundice

Dermis two layers

Papillary layer

Reticular layer

Papillary layer

- areolar

- thin

- superficial

- dermal papillae

Reticular layer

- dense irregular C.T.

- most of dermis

Dermal papillae

- extend into spaces between epidermal ridges

- form fingerprints

- genes determine pattern

Dermis

- on average 1-2 mm thick

- binds epidermis to underlying tissues

- dense irregular connective tissue

- muscle cells

- nerve cells processes

- specialized sensory receptors

- blood vessels

- hair follicles

- glands

Accessory structure of the skin

- originate from the epidermis

- nails

- hair follicles

- skin glands

Nail

protective covering

- nail plate

- nail bed

- lunula

Hairs develop from

epidermal cells at the base of hair follicle

follicle extend into

dermis

three parts of hair follicles

- hair root

- hair bulb

- hair shaft

hair bulb

mitotic region

hair shaft

kerantinized, dead , epidermal cells

hair papilla

contains nourishing blood vessels

hair color

type and amount of melanin

arrector pili muscle

causes hair to stand on end

Sebacous glands

usually associated with hair follicles

- holocrine glands

- secrete sebrum (fatty material and cellular debris)

- waterproof and lubricates skin

- absent on palms and sole

Sweat glands

also called sudoriferous glands

- widespread in skin

- orginates in deeper dermis or hypodermis

4 types of sweat glands

- eccrine glands

- apocrine sweat gland

- ceruminous glands

- mammary glands

Eccrine glands

sweat

Aprocrine glands

- inguinal and axillary

- activate at puberty

- scent

Ceruminous glands

in ear canal - secrete wax

Mammary glands

produce milk when lactating

Regulation of body temperature

slight shifts can disrupt rates of metabolic reactions

Skin plays a key role in the

homeostatic mechanism that regulates body temperature

Heat

is a product of cellular metabolism

Heat producing body cells

- skeletal muscle

- cardiac muscle

- cells of certain glands such as the liver

The primary means of heat loss

radiation

conduction

heat moves from the body directly into the molecules of cooler objects in contact with its surface

convection

continuous circulation of air over a warms surface - removing heat

Hyperthermia

abnormally high body temperature

Hypothermia

abnormally low body temperature

Inflammation

is a normal response to injury or stress

During inflammation

- blood vessels in affected tissues dilate and become more permeable allowing fluids to leak into the damage tissues

Inflamed skin may become

- reddened

- swollen

- warm

- painful

A shallow cut

- epidermal cell along its margin are stimulated to divide more rapidly than usual

- new cells cover the gap

A deep cut

- into the dermis or subcutaneous layer

- blood vessels break which cause a clot to form

scab

clot and dried tissue fluid

growth factors

stimulate new tissue formation

phagocytic cells

remove dead cells and debris

scar

formed from excess collagenous fibers

First degree burn

superficial, partial-thickness

- epithelial only

Second degree burn

deep, partial-thickness

- part of dermis - some blood supply damaged

Third degree burn

full-thickness

- all of dermis - no blood supply

Third degree burn treatment

- autograft

- homograft

- various synthetic skin substitutes

Life-span changes

- skin becomes scaly

- age spots appear

- epidermis thins

- dermis becomes reduced

- loss of fat

- wrinkling

- sagging

- sebaceous glands secrete less oil

Life-span changes (cont.)

- melanin production slows

- hair thins

- number of hair follicles decreases

- nail growth becomes impaired

- sensory receptors decline

- body temp. unable to be controlled

- diminished ability to activate Vit. D - brittle bones