Layers Of The Skin

definition & functions of the integumentary system

the organ system that includes the skin and it’s accessory organs

maintains homeostasis, regulates body temperature, delays water loss, synthesize biochemicals (Vitamin D), excretes small amounts of waste

layers of the skin (superficial to deep)

epidermis, dermis, hypodermis (subcutaneous layer)

def + function of the epidermis

outer layer of skin composed of stratified squamous epithelium; lacks blood vessels

protect the body — acts as a tough outer barrier

prevent/delay water loss

protect against damage and stress through keratinization

protect DNA from UV radiation through melanin produced by melanocytes

continuously replace itself — cells are produced in the stratum basale and old cells are shed

sublayers of the epidermis (superficial to deep)

all begin w/ “stratum” which is means layer

CORNEUM — dead/older cells → shed
LUCIDUM — palms + soles ONLY
GRANULOSUM
SPINOSUM
BASALE — cells reproduce/divide, new epidermal cells are produced, cells receive nourishment from blood vessels in the dermis

how do new epithelial skin cells form

1. Cells in the stratum basale divide → this makes new skin cells

2. The new cells push the older cells upward toward the surface

3. As the cells move upward, they get farther away from the blood vessels that provide nourishment

4. Eventually, the older cells die

5. The dead cells reach the stratum corneum and are eventually shed off

6. Meanwhile, the stratum basale keeps making new cells to replace them

when do cells during formation get kertainized & why

older cells are called keratincoytes

during: throughout the process

why: To protect the skin; keratin makes the cells harder and more resistant to damage and stress

what’s a callus & how does it relate to the epidermis’s sublayers

stratum basale balances the loss of dead cells from the stratum corneum, and that regular rubbing/pressure increases cell division, producing a callus

melancoytes & melanin

melanocytes: body cells capable of producing a pigment called melanin; located in stratum basale

• melanin: a pigment occurring in the hair, skin, and iris of the eye

  • functions: produces skin color, eye color, hair color, protection against possible DNA mutations

2 types of pigment
eumelanin: brown-black
pheomelanin: yellow-red

how does melanin protect cells against UV radiation

higher UV exposure can decrease folate levels

• melanin helps protect skin cells from UV radiation by absorbing UV and concentrating around the nuclei of skin cells, helping reduce UV-related damage

folate levels: how much folate (a vitamin) is available in your body/blood

• aids with DNA synthesis, cell division, repairment, embryo development, etc — so the higher the level, the better

skin color disorders

Albinism

Type: Genetic condition

Cause: A genetic defect affects tyrosinase, an enzyme involved in making melanin

• the melanocytes are still there. The problem is that they cannot make melanin

  • genetic defect → melanocytes can't make melanin → very little/no pigment → very light skin, hair, and eyes

  • lack of melanin also means more sensitivity to sunlight

Vitiligo

Type: Autoimmune disorder

Cause: The body's immune system destroys melanocytes in certain areas.

• the problem is the melanocytes themselves being destroyed.

  • immune system attacks → melanocytes destroyed → no melanin in those areas → lighter patches of skin

  • the patches can spread and develop later in life

skin cancers

Carcinoma

Type: Skin cancer that originates in epithelial cells

Where does it start: Epithelial cells of the skin

How common: It is the most common type of skin cancer in your notes.

Where is it commonly found: Neck, face, and scalp

How does it grow: It generally grows slowly.

Treatment:: Usually surgery or radiation

Melanoma

Type: Skin cancer that originates in melanocytes

Where does it start: Melanocytes — the cells that normally produce melanin.

Where can it occur: Anywhere on the body (often develops from moles)

• mole: is a small, usually dark or pigmented spot on the skin. It happens when pigment-producing cells (melanocytes) grow together in a cluster.

What does it look like: It can appear as a pigmented area with varied colors and may be irregular or bumpy.

Treatment: Surgery, radiation, medications, or chemotherapy

def & function of the dermis

binds the epidermis to the underlying tissues; causes skin to be tough and elastic; middle layer

• supports and connects the epidermis to the tissue underneath it

• provides nutrients to skin cells through its blood vessels

• helps regulate body temperature through its blood vessels

sublayers of the dermis

Papillary Layer

• Upper layer of the dermis

• Closer to the epidermis

• Forms dermal papillae, which create the ridges that contribute to fingerprints

Reticular Layer

• Deeper layer of the dermis

• Makes up most of the dermis

• Contains things like blood vessels, nerves, hair follicles, sweat glands, and sebaceous glands

• Has collagen and elastic fibers, giving skin strength and elasticity

def & function of the hypodermis / subcutaneous layer

deepest layer of the skin; located beneath the dermis

• connects the skin to the tissues underneath it, including the fascia of bones and muscles

• insulates the body → helps keep body temperature stable

• cushions the body → helps protect underlying structures from impacts

other skin diseases

Cellulitis

Type: Bacterial infection

Cause: Bacteria enter through a break in the skin

What happens: The infection affects the deeper layers of skin and the tissues underneath it

Symptoms: Redness, Swelling, Pain, Fever

Treatment: Antibiotics

Scabies

Type: Contagious skin disease

Cause: An itch mite.

How is it transmitted: Through prolonged direct skin-to-skin contact with someone who has it

What happens: The mites cause an itchy rash

What does it look like: Small red bumps, Blisters, Very itchy

Treatment: creams or antiparasitic medication