Chapter 5

What are the two major parts that make up the integumentary system?

Cutaneous membrane (aka skin) and accessory structures

What type of skin/tissues do we focus on in the cutaneous membrane?

stratified squamous epithelium, areolar connective tissue, and dense irregular connective tissue

What are the main accessory structures that make up the integumentary system?

hair, exocrine glands, and nails

The skin contains two layers, the epidermis or ______ and the dermis or _____

epithelium, connective tissue

Loose connective tissue beneath the dermis makes up what layer?

subcutaneous layer/hypodermis

What does the hypodermis do?

separates integument from deeper tissues and organs

What is NOT part of the integumentary system yet interwoven with connective tissue of the dermis?

hypodermis

What are the 5 main functions of the integumentary system?

Protection, temperature maintenance, synthesis and storage of nutrients, sensory reception, and excretion and secretion

How does the protection function work?

the skin covers and protects underlying tissues and prevents fluid loss

How does the temperature maintanence function work?

skin regulates heat exchange with the environment

The epidermis synthesizes …

vitamin D

the dermis stores lipids in …

adipose tissue

How does sensory reception work?

receptors detect touch, pressure, pain, and temperature that is relayed to the nervous system

What do glands excrete?

salts, water, and organic waste

Specialized integumentary/_______ glands secrete milk

mammary

The epidermis is composed of ____ epithelial tissue

layered

Is epithelial tissue vascular or avascular?

avascular

How does epithelial tissue get nutrients and oxygen?

relies on diffusion from underlying connective tissue

What cells are the most active in the epidermis?

The deepest cells (closest to the dermis)

In the epidermis, the cells in the outer/superficial layers are ______

dead

What are the majority of the cells in the epidermis?

keratinocytes (contain the protein keratin)

thick skin has 5 layers of cells also known as …

strata

Where is thick skin found?

palms of hands and soles of feet

Thick skin has a very thick what layer?

stratum corneum

What is the total thickness of thick skin?

0.5 mm (standard paper towel)

Thin skin has ____ layers of cells

4

Thin skin covers…

the rest of the body

total thickness of thin skin is about..

0.08 mm (plastic sandwich bag)

Stratum basale is the _____ layer of the epidermis and is also known as stratum_______

deepest, germinativum

germinativum

“to start growing”

Stratum basale is attached to the basement membrane with the help of what?

hemidesmosomes

What are the three main cells in stratum basale?

basal/germinative cells, tactile/Merkel cells, and melanocytes

Basal/germinative cells

stem cells that continually divide (by mitosis) to replace cells lost at the surface

Tactile/Merkel cells

sensitive to touch

Melanocytes

synthesize melanin (pigment that gives color to our hair and skin)

Psoriasis

skin condition where basal cells of stratum basale divide more often compared to normal stem cells resulting in hyperkeratosis

hyperkeratosis

overproduction of keratin in areas such as the elbow, palms, soles, and scalp

How are epidermal ridges formed?

formed by cells of the stratum basale extending down into the dermis

Where are dermal projections/dermal papillae located?

they extend up into the epidermis between the ridges

the ridges and dermal papillae _____

interlock

Contours of skin surface follow …

ridge patterns

ridge patterns increase….

the surface area for diffusion of nutrients between epidermis and dermis

Contours of skin that follow ridge patterns make up the basis for what?

fingerprints

How are epidermal ridge shapes determined?

by the environment outside the uterus

What is special about epidermal ridge shapes?

they are unique and don’t change over time (even different in identical twins)

What happens to new daughter cells formed in stratum basale?

they migrate upward toward skin surface

What are the three layers that new daughter cells from the stratum basale progress through?

stratum spinosum, stratum granulosum, and stratum lucidum

Stratum spinosum is also known as the _____ layer

spiny

in what layer may cells continue to divide

stratum spinosum

Stratum spinosum is made up of what?

keratinocytes

How is stratum spinosum held together?

with desmosomes

Stratum spinosum contains what that is involved in immune response?

branded dendritic cells

stratum granulosum is known as the ___ layer

grainy

Cells stop dividing in what layer?

stratum granulosum

Cells start to make large amounts of keratin in what layer?

stratum granulosum

Keratin

durable, water-resistant protein that coats surface of skin and forms hair and nails

stratum lucidum is also known as the _____ layer

clear

What makes up stratum lucidum?

flattened, densely packed cells filled with keratin

What is stratum corneum made up of?

15-30 layers of flattened, dead cells packed with keratin (keratinized or cornfield cells)

Cells in stratum corneum are tightly connected by what?

desmosomes

Generally takes how many days from cells to move from stratum basale to stratum corneum?

7-10 days

As cells move through the skin, what happens to the cells?

they fill with keratin and die

Dead cells stay in stratum corneum how much time before being shed or washed away?

two weeks

What are the two pigments that influence skin color?

carotene and melanin

Polygenetic inheritance

when a trait or phenotype (like skin color) is determined by several genes

What color is carotene?

orange-yellow

Carotene accumulates in the _____ cells

epidermal cells

Where is carotene found (sources)?

orange-colored foods (carrots, squash)

What are the two types of melanin?

red-yellow and brown-black

Melanin is made by…

melanocytes

Melanosomes

store melanin in vesicles

When does melanocyte activity increase?

in response to sunlight (UV radiation) exposure

How does melanin protect the skin?

absorbs UV radiation, protecting deeper layers of epidermis and dermis

Thiamine Dimer

when 2 adjacent thiamine bases form covalent bonds with each other instead of hydrogen bonds with adenine bases → DNA kinks → mutations →cancer

Albinism

when person has melanocytes but isn’t able to make melanin

Freckles

small pigmented spots on the skin where melanin production is greater than average

How is vitamin D formed?

converted from cholesterol-related steroids when epidermal cells are exposed to sunlight

Liver and kidneys convert vitamin D into what?

calcitriol

Calcitriol

essential for absorption of calcium and phosphorus in the small intestine

Inadequate vitamin D3 can lead to….

weak and flexible bones

Oxygenated blood is _____

bright red

How does an increase in body temperature affect blood vessels?

dilates superficial blood vessels in the dermis, resulting in flushed red skin color

How do you get pale skin?

temporary constriction of the same vessel

cyanosis

a blush coloration that occurs when blood oxygen supplies are diminished

Carcinoma

any cancer of epithelial tissue

What is the most common skin cancer?

basal cell carcinoma

Where does basal cell carcinoma originate from?

stratum basale

Squamous cell carcinoma is found where?

in more superficial layers

What is the most dangerous skin cancer?

malignant melanoma

Malignant melanoma

usually begins as a mole and can metastasize through the lymphatic system

What are the two main layers in the dermis?

superficial papillary layer and deeper reticular layer

What type of tissue makes up the papillary layer of the dermis?

areolar tissue

function of dermal papillary layer

supports and nourishes epidermis

What are the main components of the dermal papillary layer?

capillaries, lymphatic vessels, and sensory neurons supplying skin surface

the dermal reticular layer can be described as…

interwoven meshwork of dense irregular connective tissue

What does the dermal reticular layer contain that provides flexability?

elastic fibers

In the dermal reticular layers, what limits flexibility to prevent damage to tissues?

collagen fibers

What is the dominant cell type in the dermal reticular layer?

fibroblast

What is extended into the dermal reticular layer?

accessory organs derived from epidermis (hair follicles, sweat glands)

What are some accessory components to the reticular layer?

blood vessels, lymphatic vessels, nerve fibers, and sensory receptors