Anatomy and Phys - Ch. 5

Integumentary System

skin, accessory structures (hair, nails, glands) and other tissues (blood vessels, muscles, nerves)

The organs of the integumentary system include:

epidermis

The outer layer of the skin

made up of 4-5 layers of keratinized stratified squamous epithelium, contains 4 main cells types

in most areas of the body, made up of 4 distinct strata, except in thick skin which contains an extra layer

structure of the epidermis

?

function of the epidermis

produce a hard protein called keratin; protects underlying tissues from abrasion, heat, microbes, and chemicals

main cell type of the epidermis

keratinocytes

produce a pigment protein called melanin; absorbs UV light, prevents DNA damage

melanocytes

intraepidermal macrophages involved in immunity; type of WBC that migrate to epidermis and monitor for pathogens

Langerhans cells

special touch receptor cells that contact sensory neurons; found mostly in the bottom layer of the skin

tactile epithelial (Merkel) cells

single row of mostly cuboidal/columnar keratinocytes along with melanocytes and tactile epithelial (Merkel) cells; deepest layer

structure of stratum basale

process by which cytoplasm is replaced with hardening protein keratin as cells move further away from the dermis and are no longer receiving nutrients, oxygen, blood supply

keratinization

8-10 layers of keratinocytes, contain organelles and produce coarser bundle of keratin

cells appear rounded in living tissue and appear shrunk/covered in spines when prepared for microscopic examination

structure of stratum spinosum

3-5 layers of flattened keratinocytes that are undergoing apoptosis; cells contain dark staining granules of keratohyalin (protein) and lamellar granules

structure of stratum granulosum

helps organize keratin filaments

keratohyalin

secrete lipid-filled product that acts as a water repellant

lamellar granules

4-6 layers of flattened, clear, dead keratinocytes

present only in thick skin (fingertips, palms, and soles)

structure of stratum lucidum

provides additional toughness to the fingertips, palms, and soles

function of stratum lucidum

25-30 layers of flattened, dead keratinocytes (membrane enclosed packages of keratin with no nucleus, cytoplasm, or organelles); most superficial layer

structure of stratum corneum

7-10 weeks

length of the entire process of keratinization

excessive number of keratinized cells shed from the skin of the scalp

dandruff

disorder in which keratinocytes divide and move more quickly than normal; results in thicker, flaky, silvery scales that form on the skin’s surface (usually the knees, elbows, and scalp)

psoriasis

binds the epidermis to the underlying tissues

function of the dermis

composed mostly of connective tissue with two regions: papillary and reticular

structure of the dermis

superficial portion of the dermis composed of loose areolar connective tissue (contains thin collagen and fine elastic fibers) and contains dermal papillae that project into the undersurface of the epidermis

structure of the papillary region of the dermis

nipple-shaped projections that anchor the epidermis to dermis; contain blood vessels that feed epidermis and touch receptors

dermal papillae

True/False: The dermal papillae are more pronounced on the fingertips and toes.

True

thicker and deeper portion of the dermis composed of dense irregular connective tissue; also contains hair follicles, nerves, and skin glands

structure of the reticular region of the dermis

dense irregular connective tissue contains bundles of thick collagen fibers and coarse elastic fibers that are arranged in a net-like manner to resist stretching on multiple planes

function of the reticular region of the dermis

caused by tears or excessive stretching in the reticular region of the dermis

stretch marks (striae)

attaches the skin to the underlying tissues and organs

function of the subcutaneous layer (hypodermis)

mostly composed of adipose tissue; contains blood vessels and nerves that feed superficial layers

structure of the subcutaneous layer (hypodermis)

pigment protein produced by melanocytes in the stratum basale that protects the underlying layers from the sun’s harmful UV rays

melanin

process by which melanocytes transfer pigment to nearby cells

cytocrine secretion

inherited inability of an individual to produce melanin; the melanocytes are unable to synthesize tyrosinase and melanin is missing from the hair, eyes, and skin

albinism

True/False: All people do not have the same number of melanocytes.

False

True/False: Genetic differences in skin color result from differing amounts of melanin and in size/distribution of melanin granules

True

Exposure to sunlight (increases/decreases) melanin production and causes (darkening/lightening) of the skin.

increases, darkening

the oxygen-carrying pigment in RBCs

hemoglobin

appearance of well-oxygenated skin

pinkish

appearance of skin that has poor oxygen

bluish color (cyanosis)

yellow-orange pigment that gives egg yolks and carrots their color; is a precursor of vitamin A

carotene

part of the hair that is above the skin surface

shaft

epithelium that surrounds the hair root and bulb that is the more actively growing area

hair follicle

area of the hair below the skin surface containing the epithelial and dermal root sheaths

root

smooth muscle in the dermis that contracts with cold or fear and pulls down on the hair to form “goosebumps”

arrector pili muscles

free nerve endings that come up from below and wrap around and make contact with the hair follicles; detects hair movement

hair root plexus

secrete sebum (oil) into hair follicles, prevents skin and hair from drying out, inhibits some bacterial growth

function of sebaceous glands

mixture of triglycerides, cholesterol, proteins, and inorganic salts that coats the surface of hairs and prevents them from drying and becoming brittle; also prevents excessive evaporation of H2O from the skin, keeps skin soft/pliable, inhibits growth of some bacteria

sebum

found in most areas of the body, except thick skin

location of sebaceous glands

secrete watery sweat through ducts that open to pores in the skin to help with thermoregulation as sweat evaporates from the skin

function of eccrine sweat glands

found in most regions of the body

location of eccrine sweat glands

secrete a thicker sweat into hair follicles and become active after puberty

function of apocrine sweat glands

found mainly in the skin of the axilla (armpits), groin, and areolae (around nipples)

location of apocrine sweat glands

lipids and proteins in which bacteria feed off of and give a musky scent (body odor)

contents of sweat from apocrine glands

secrete cerumin (wax) into the ear canal

function of ceruminous glands

provide a sticky barrier that impedes the entrance of foreign bodies and insects as well as waterproofing the ear canal and prevents the growth of bacteria and fungi

function of cerumin (wax)

found only in the external auditory canal (ear canal)

location of ceruminous glands

plates of tightly packed, hard, dead, keratinocytes

structure of nails

forms a clear, solid covering over the dorsal surface of the distal portion of the digits

location of nails

visible part, filled with harder keratin

nail body (plate)

crescent-shaped area of the proximal portion of nail body, appears whitish because it is the thicker, most actively growing region of the nail

lunula

part that extends past the distal end of the digit

free edge

a thickened region of epidermis that binds the nail to the tip of the digit (fingertip)

hyponychium

part that is not visible and is buried in a fold of skin

nail root

proximal to the nail root, containing cells that divide mitotically to produce new nails cells

nail matrix

stratum corneum of the epidermis

eponychium (cuticle)

thickness, strength, flexibility, degree of keratinization, distribution and type of hair, density and types of glands, pigmentation, vascularity, and innervation

local variations of skin

skin that is hairy

thin skin

skin that is hairless; typically has a thicker stratum corneum due to increased number of layers

thick skin

Sensory receptors in thin skin are ___.

sparser

Sensory receptors in thick skin are ___.

denser

Sudoriferous glands are ___ in thin skin.

fewer

Sudoriferous glands are ___ in thick skin.

more numerous

Sebaceous glands are ___ in thin skin.

present

Sebaceous glands are ___ in thick skin.

absent

Epidermal ridges are ___ in thin skin.

lacking due to poorly developed, fewer, and less well-organizaed dermal papillae

Epidermal ridges are ___ in thick skin.

present due to well-developed and more numerous dermal papillae organized in parallel rows

stratum lucidum essentially lacking; thinner strata spinosum and corneum

thin skin

stratum lucidum present; thicker strata spinosum and corneum

thick skin

homeostatic regulation of body temperature

thermoregulation

by releasing sweat onto the surface and adjusting the flow of blood in the dermis

2 ways the skin contributes to thermoregulation

How does adjusting the flow of blood in the dermis contribute to thermoregulation?

blood vessels in the dermis dilate to allow more blood to flow closer to surface of skin, increases amt. of heat loss thru the skin

or

blood vessels constrict to decrease amt. of blood flow to decrease heat loss

True/False: The dermis has an extensive network of blood vessels, housing 8-10% of the total volume of blood in an adult.

True

___protects underlying tissues from microbes, abrasion, heat, and chemicals

Keratin

Tightly packed cells of the epidermis act as a ___ to prevent evaporation.

water barrier

___in the epidermis guard against bacteria and viruses.

Macrophages

include touch, pressure, vibration, and thermal sensations; rely on special sensory receptors as well as free nerve endings

cutaneous sensations

nerve endings that are sensitive to light touch

Meissner corpuscles

dendrites that lack any apparent structural specialization that initiate signals that give rise to heat, cold, pain, tickle, and itch

free nerve endings

nerve endings that are sensitive to pressure, deep touch, and vibration sense

pacinian corpuscles (or lamellar corpuscles)

True/False: The skin plays a small role in excretion as a small amount of water is released through sweat and evaporation. Most substances are excreted through the digestive and urinary systems.

True

True/False: Water soluble substances can be absorbed by the skin.

False

fat-soluble vitamins (A, D, E, and K)

certain drugs

gases (oxygen and carbon dioxide)

some hormones

lipid-soluble substances that can be absorbed through the skin

a drug contained in a skin patch, released continuously at a controlled rate; normally used for drugs that are quickly eliminated from the body (if they were taken by mouth, would need to be taken more frequently)

transdermal drugs

requires the activation of a precursor molecule in the skin by ultraviolet (UV) rays in sunlight

synthesis of vitamin D

Enzymes in the liver and kidneys modify the activated molecules to produce ____.

calcitriol

the most activate form of Vitamin D, hormone that aids in the absorption of calcium from foods in the gastrointestinal tract into the blood

calcitriol

How does vitamin D play a large role in immunity?

helps to activate cells that respond to infections (especially respiratory infections)

occurs following a superficial wound (such as abrasions or minor burns) that only affects the epidermis; returns to normal function

epidermal wound healing

How does epidermal wound healing occur?

basal cells of the epidermis enlarge and migrate across the wound; eventually the wound is sealed, and the epidermis returns to normal

occurs when an injury extends to the dermis and subcutaneous layer and involves bleeding; may result in loss of function and development of scar tissue

deep wound healing