Integumentary System

epidermis

The outermost layer of skin, composed of stratified squamous epithelial cells. It provides a protective barrier against environmental hazards and prevents water loss.

dermis

The thick layer of skin beneath the epidermis contains proper connective tissue, blood vessels, and nerve endings. It supports and nourishes the epidermis and is involved in thermoregulation and sensation.

hypodermis

underneath the skin, not technically part of the skin but it is part of the integumentary system, also called subcutaneous tissue (superficial fascia), mostly made up of adipose tissue, absorbs shock, insulates the body, & anchors skin to structures underneath

Keratinized stratified squamous epithelium

what is the epidermis

4 cells of the epidermis

keratinocytes, melanocytes, dendritic cells, & Merkel (tactile) cells

keratinocytes

most common epithelial cell, produces keratin (a fibrous protein), starts in stratum basale

What happens as keratinocytes move up the layers of the epidermis?

They undergo keratinization, becoming more flattened and filled with keratin, eventually dying and forming a protective outer layer.

how often is epidermis replaced?

every 25-45 days

melanocytes

make melanin

melanin

A pigment responsible for skin, hair, and eye color, providing protection against ultraviolet (UV) radiation.

Organelles within melanocytes that produce and store melanin; transfer melanin to keratinocytes in the epidermis.

melanosomes

dendritic cells

Security guards of the epidermis:

-patrol for foreign substances

-eat & ingest these foreign substances

-activate the immune system

Merkel (tactile) cells

Touch receptors

cornified cells

Dead keratinocytes that form the outermost layer of the skin, providing a barrier to protect underlying tissues.

stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

Layers of the epidermis from deep to superficial

stratum lucidum

Which layer of the epidermis is only found in thick skin?

After what layer in the epidermis are cells considered dead?

stratum granulosum

outermost layer of the epidermis

stratum corneum

-consists of rows of cornified cells (dead & flat cells)

-has a glycolipid coating

-protects against biologic agents, chemicals, and physical damage

-nearly waterproof

-sheds regularly

characteristics of stratum corneum

parts of dermis

cells & semi fluid matrix

2 layers of the dermis

papillary & reticular

papillary layer

-made up of areolar connective tissue

-contains: blood vessells, pain receptors, & touch receptors

-has dermal papillae

-fingerprints

dermal papillae

Little projections that push toward the epidermis which create friction ridges that:

-help us grip things

-help with touch

-create our fingerprints

reticular layer

The deeper layer of the dermis is composed of dense irregular connective tissue, providing strength and elasticity to the skin. It contains hair follicles, sweat glands, and other structures.

it also has: cleavage lines & flexure lines

Cleavage lines are areas where collagen is less dense, while flexure lines are deep creases around joints

Difference between cleavage and flexure lines

pneumonic for layers of the epidermis

Can Lambo Get Some Baseballs?

the amino acid that makes up the polymer melanin

tyrosine

melanin, carotene, hemoglobin

3 pigments of the skin

reddish-yellow to brownish-black

range of melanin

local accumulations of melanin

freckles and moles

increase in need for the production of mleanocytes

the closer you are to the equator….

protects the DNA of our skin cells from UVA radiation by absorbing rays and dissipating them as heat

Why is melanin so important?

yellow-orange pigment; builds up in the stratum corneum and fat of the hypodermis

carotene

can be turned into Vitamin A, which is vital for our vision and epidermal health

Why is carotene important?

gives fair-skin a pinkish color

Hemoglobin

the epidermis is almost transparent, so you can see the RBC in the dermal capillaries underneath

Why does the hemoglobin give fair skin a pinkish color?

blue skin; caused by low oxygen levels in the blood & respiratory and cardiovascular issues; most noticeable in mouth and nail beds

cyanosis

pallor

pale skin: due to emotional stress, fear/rage, anemia & low BP; look at palsms and nail beds of darker skinned people

erythema

redness of skin; caused by fear, hypertension, inflammation, allergies, & embarassment

ecchymoses

bruising, red/purple/green/yellow marks, happens when blood vessels are damaged so the blood leaks into tissue

hyperpigmentation

Excess melanin production that leads to darker patches of skin; brown or black patterns, darker & thickened areas of skin; may indicate endocrine disorder

jaundice

A yellowing of the skin and eyes caused by elevated blood bilirubin, often associated with liver dysfunction

sclera (white of eyes) & skin

where is jaundice seen?

extra structures that come from the epidermis

appendages of skin

made up of dead, keratinized cells

what is the hair made up of?

pili

another name for hair

the root is below the skin and the shaft is the visible part

difference between root and shaft of hair

Functions of hair

-detect things touching skin

-protect us from physical trauma

-reduce heat loss

-protect skin from sunlight

-protect the eyes (lashes)

-filter things (nose hairs)

shape of the hair shaft

what determines the shape of hair

flat/ribbon like shaft

kinky & curly hair

oval shaft

silky/wavy hair

round shaft

straight/course hair

pigments

Where does hair color come from?

melanins

origin of blond/black/brown hair

phenomelanin

origin of red hair

decrease in melanin & increase in air bubbles in the hair shaft

origin of gray/white hair

pale, thin, fine, unpigmented hair found on most of the body (kids & female adults)

vellus hair (peacefuzz)

thicker, coarser, and pigmented hair found on the scalp, face, armpits, and pubic area.

terminal hair

2 mm/week

average hair growth

4 years

hair follicles on head lifespan

few months

hair follicle lifespan of the eyebrows

age 40

At what age does hair thinning begin in both sexes?

most common type of baldness and it is genetically determined

male pattern baldness

-stress

-low thyroid hormone

-dietary deficiency

-certain drugs (chemotherapy)

hair loss or texture changes can also be related to

modified epidermis that protect the ends of fingers and toenails

what are nails?

hard keratin

what makes up the nails?

responsible for growth

nail matrix

sudoriferous glands

sweat glands are also called..

eccrine (merocrine) & apocrine

two types of sweat glands

part of sweat glands; contract when stimulated by the nervous system and force sweat into ducts

myoepithelial cells

difference between eccrine and apocrine glands

Eccrine glands are distributed widely across the skin and produce a watery secretion, while apocrine glands are mainly found in specific areas such as the armpits and groin, producing a thicker secretion that can contain fatty substances.

important for thermoregulation; help to cool us down

eccrine (merocrine) sweat glands

palms, soles of feet, and forehead

location of eccrine (merocrine) sweat glands

axillary and anogenital areas

location of apocrine sweat glands

they are broken down by bacteria

Why does apocrine sweat gland secretion become odorous?

may act as a sexual scent gland

potential function of apocrine sweat gland

modified apocrine gland that lines external ear canal and makes earwax (cerumen)

Ceruminous gland

modified apocrine gland that secretes milk

Mammary gland

secrete sebum

function of sebaceous (oil) glands

soften skin, soften hair, slow water loss, anabacterial properties

Functions of sebum

face, neck, and upper chest

location of sebaceous (oil) glands

thick skin of palms and soles

where sebaceous glands are not found

protection, body temperature, cutaneous sensation, metabolism, blood reservoir, & excretion

6 functions of the integumentary system

keratin blocks out water and water soluble substances

How does the skin physically protect the body?

dendritic cells (epidermis) & macrophages (dermis)

Biological barriers

capture foreign substances and help trigger an immune response

dendritic cells role in biological protection

destroy viruses & bacteria

macrophage role in biological protection

Sweat that you don’t really notice

insensible perspiration

0.5 L

How much insensible perspiration do you have daily?

sweat that you notice; used when you need to cool down

sensible perspiration

when blood vessels widen and warm blood flows to surface of skin

vasodialation

blood vessels get narrow and warm blood does not reach surface of skin

vasoconstriction

cutaneous sensation

-skin has many sensory receptors that detect temperature, touch, and pain

-receptors are part of nervous system

how does the skin work as a blood reservoir?

skin has a lot of blood vessels so when another part of the body needs more blood, dermanl blood vessels can constrict and send blood elsewhere

5%

How much of your body’s blood volume can the skin hold?

metabolic functions of the skin

-vitamin d synthesis

-creates collagenase

-supports the liver

-enzymes in keratinocytes can help disarm cancer-causing chemicals & activate anti-inflammatory drugs

disarm cancer-causing chemicals & activate anti-inflammatory drugs

roles of enzymes in keratinocytes

sweat helps to remove nitrogenous waste, water, and salt

how does the skin help with excretion?