Integumentary System and Epidermis Layers Overview

How large is skin?

~22ft. squared

What area does skin cover?

Entire external surface

What % body mass is skin?

`16%`

Main function of the epidermis

Protective barrier from external harm like UV rays, chemicals; provides touch sensation

What tissue is the epidermis made out of?

Stratified squamous epithelial tissue

Stratum Corneum

Made of dead keratinocytes, dead superficial layer, protects skin against abrasions, waterproofs

Stratum Lucidum

Made of dead keratinocytes, clear, cells die, lose nuclei, found ONLY in thick skin

Stratum Granulosum

Made of living keratinocytes, produces keratin, produced lipids to waterproof skin (lamellar bodies/granules)

Stratum Spinosum

Made of living keratinocytes, spiny, connected by desmosomes

Stratum Basale

Made of living keratinocytes, single layer of cells, repeatedly divide to push up new keratinocytes

Keratinocytes

Function- produce keratin protein that waterproofs skin and resists abrasion (nails, hair); location- stratum basale, move up and shed continuously

Langerhans Cells

Function- immune cells, fight infections, ingest foreign particles; location- produced in bone marrow, migrate to stratum spinosum

Melanocytes

Function- produce melanin (pigment that darkens skin); location- stratum basale

Merkel Cells

Function- sense light touch (neurons); location- @ junction of epidermis and dermis

The Dermis

Deeper layer, majority of skin, vascular (with blood vessels); main function: support and protect skin and deeper layers, assist in thermoregulation, aid in sensation

Papillary Layer

Thin, superficial, 1/5 of Dermis, helps control temp. of skin; Structures include: dermal papillae, meissner's corpuscle, capillary loops, free nerve endings

Reticular Layer

Thick, big portion of Dermis, vascular (contains blood vessels), and supports skin; Structures include: hair follicle, arrector pili muscle, sebaceous gland, sudoriferous gland, pacinian corpuscle

Dermal Papillae

Bumps that bind dermis to epidermis; creates fingerprints

Meissner's Corpuscle

Sense light touch; nerves

Capillary Loops

Blood vessels; delivers O2 + nutrients, removes CO2 + waste

Free Nerve Endings

Sense pain, heat, cold, tickling, itching

Hair Follicle

Tunnel where hair grows

Arrector pili muscle

Contracts to raise hair (goosebumps)

Sebaceous Gland

Oil glands, oil is called 'sebum'

Sudoriferous Gland

Sweat glands, odor

Pacinian Corpuscle

Sense heavy pressure, vibrations

Hypodermis

AKA Subcutaneous layer (technically not skin); main functions: storing energy, insulating body, connecting Dermis to muscles and bones; made of adipose tissue (fat)

Adipose Tissue

Adheres skin to muscle below loosely, allows sliding; insulation; absorbs shock

Sensory nerve

Sends sensory messages TO brain from: merkel cells, pacinian corpuscle, free nerve endings, meissner's corpuscle

Motor Nerve

Sends messages FROM brain to: arrector pili, sebaceous and sudoriferous glands

Blood Vessels

Deliver O2 + nutrients; removes CO2 + waste

Artery

Provides nutrients to the skin; helps regulate body temp

Vein

Collects blood from skin and surrounding superficial tissues

Eccrine Glands

Palms, soles, forehead; around 2-4 million; made of 99% water, salts, waste; function: prevents the body from overheating (evaporative cooling)

Apocrine Glands

Axillary and genital regions (skin, ear, breast, eyelid); only around 2,000, very few; made of water, salts, waste, fat; function: odorless bacteria that feeds on sweat; ceruminous glands- make ear wax; mammary glands- produce milk

Melanin

Produced by melanocytes, and the abundance of and type of melanin impacts skin color. Melanin absorbs harmful UV rays.

Carotene

Yellow/orange pigment that is produced depending on your diet; carotenemia can occur when skin turns orange color when one eats many orange foods like carrots.

Hemoglobin

The red pigment that appears on lighter skinned people impacts skin color. Oxygen-carrying protein in red blood cells contributes to the red pigment on skin (ex. blushing).

Why does vitamin D deficiency cause rickets?

If there is a lack of vitamin D, your calcium and phosphorus levels in your bones would drop and not be maintained properly. This leads to weak bones and rickets.

Body Hair

Senses insects on skin

Eyelashes

Shields eyes from dust and dirt

Nose Hair

Filters particles in air we inhale

Scalp Hair

Protects against heat loss and sunlight

Physical Barrier

Skin forms a physical barrier with layered epidermis that is keratinized. Example would be the lipids secreted in lamellar bodies in stratum granulosum protecting skin from water loss.

Chemical Barrier

Skin forms a chemical barrier by skin secretions and melanin. Example would be sweat and sebum having antimicrobial ingredients that kill bacteria and melanin shielding UV light.

Biological Barrier

Skin forms a biological barrier by using Langerhans cells to ingest invaders and activate the immune system. Example would be that skin protects our bodies from external harm, protects our immune system, and regulates water loss.