Ch. 5 The Integumentary System

integumentary system

system including skin and accessory structures like hair, glands, and nails

provides protection and is first line of defense

5 functions

protection, sensation, temperature regulation, vitamin D production, excretion

protection

protects against UV light, microorganisms, water loss

sensation

sensory receptors for heat, cold, touch, pressure, pain

temperature regulation

modulation of blood flow through the skin and activities of sweat glands

vitamin D production

from a molecule made in the skin when exposed to UV light

excretion

small amounts of waste products eliminated

epidermis

superficial layer of stratified squamous epithelial tissue

protection and reduces water loss

dermis

deep layer of connective tissue

structural strength

subcutaneous tissue

not part of skin

loose connective tissue that connects skin to underlying structure

epidermis - avascular

nourished by diffusion from capillaries of the papillary layer of the dermis

what is the epidermis composed of

stratified squamous epithelium, epithelial cells arranged into layers or strata

basement membrane

separates epidermis and dermis

keratinocytes

most cells, produce keratin for strength

melanocytes

contribute to skin color

melanin produced by these cells then transferred to keratinocytes

same number of melanocytes in all people

langerhans cells

part of the immune system

merkel cells

detect light touch and superficial pressure

kertinization

as cells move outward through the layers they fill with keratin, die, and serve as a layer that resists abrasion and forms permeability layer

stratum basale

innermost layer, attached to the basement membrane

form epidermal ridges that interdigitate dermis (increases SA)

dominant cell type in stratum basale

basal cells (stem cells)

divide to produce cells that move into the upper layers

other cell types include sensory cells (merkel cells) and melanocytes (produce melanin)

stratum spinosum

composed of keratinocytes held together by desmosomes

include special cells for defense (langerhan cells)

stratum granulosum

cells no longer divide

lose nucleus and organelles

accumulate keratinohyaline granules and lamellated granules

stratum lucidum

clear layer

only found in thick skin

dead keratinocytes

stratum corneum

superficial layers of 20-30 layers

cells filled with keratin and surrounded by waterproofing material

cells still held together by desmosomes

melanin

provides for protection against UV light

group of chemicals derived from amino acid tyrosine

colored brown to black, may be yellowish or reddish

carotene

yellow pigment from vegetables; accumulates in stratum corneum, in adipose cells of dermis, and in subcutaneous tissue

melanosomes

vesicles of melanin

variations in skin color are due to

types/amount of melanin produces, size, number, distribution of melanosomes

certain hormones, such as estrogen or MSH, can increase melanin production during pregnancy

cyanosis

blue color caused by decrease in blood oxygen content

erythema

red color caused by increased blood flow

impacts color of skin

thickness of stratum corneum

thicker areas can be yellowish

what does the dermis consist of

connective tissue with many fibers - fibroblasts, macrophages, and adipocytes

papillary layers

loose connective tissue, contains capillaries and sensory neurons, papillae extend between the epidermal ridges

reticular layer

dense irregular connective tissue, collagen & elastic fibers extend into papillary layer and subcutaneous tissue

blood vessels, roots of hair & smooth muscle, sebaceous glands, sweat glands

cleavage lines

elastic and collagen fibers oriented in some directions more than in others

important in surgery

subcutaneous tissue, also called hypodermia

deep to skin

consists of loose connective tissue with collagen and elastic fibers

functions: energy source, insulation, padding

hair

outgrowth of the skin composed of keratin

lanugo

delicate, unpigmented hair of the fetus

terminal hair

long, course, pigmented hair of the scalp, eyelids, eyebrows, and with puberty, axilla, pubic, and face

vellus hair

fine, short hair on the rest of the body

growth stage

cells added at base and hair elongates

resting stage

follicle shortens and holds hair in place. rest, then hair falls out of follicle. new hair begins

hair color

caused by varying amounts and types of melanin. color is controlled by several genes

muscles

arrector pili - type of smooth muscle

sebaceous glands

holocrine, oily secretion, prevents drying and inhibits some bacteria, most empty into hair follicle

sweat glands (sudoriferous)

merocrine, most common; numerous in palms and soles

open onto surface of skin, have own pores

important in body temperature regulation

apocrine glands

activated at puberty

simple coiled tubular, usually open into hair follicles superficial to opening of sebaceous gland

do not regulate temp

ceruminous glands

modified eccrine sweat glands in the external auditory canal

mammary glands

modified apocrine sweat glands that produce milk

nail structure

thin plate of dead stratum corneum cells mixed with hard keratin

nail body

stratum corneum; visible portion

matrix

cells that give rise to the nail

nail root

covered by skin; extends from nail matrix

physiology of integumentary system: protection

against abrasion and diffusion, sloughing off damaged cells and holds water

against microorganisms and other foreign substances

melanin protects against uv radiation

hair on head is insulator and protection against light and from abrasion

physiology of integumentary system: sensation

pressure, temperature, pain, heat, cold, touch, movement of hairs - assorted skin cell types

physiology of integumentary system: temperature regulation

sweating and radiation

physiology of integumentary system: production of vitamin D

exposure to sunlight triggers cells to convert a steroid into inactive vitamin D

physiology of integumentary system: excretion

removal of waste products from the body