Biology midterm one grade 12 integumentary system

The skin is made up of four types of tissues:

1- Epithelial tissue: cover the body surface .

2-Connective tissue :supports and protects.

3-Muscle tissue :enables movement.

4-Nerve tissue :is the body’s communication network

The skin has two main

layers :

Epidermis

2-dermis

The outer layer of the skin is the epidermis which consists of

a thin layer of epithelial cells:

The outer layer of epidermal cells contain

Keratin

Keratin is

Keratin : is a protein that waterproofs and protects the

cells and tissues below.

The inner layer of epidermal cells continually divide by

mitosis to replace the cells that are shed ,and produces a

pigment called

Melanin

Melanin…

Melaninprotects deeper cells from damaging effects of

ultraviolet rays of sunlight, the amount of melanin produced

determines skin color.

The dermis is made up of ….. tissue which

prevents the skin from tearing and enables the skin to

its normal state after it is stretched.

connective

The dermis contains:

1- Nerve cells

2- Muscle fibers

3- Sweat glands

4- Oil glands sebaceous gland

5-Hair follicles

Note

Hair follicles :holes in the dermis from which Hair cells grow out of .

Cells at the base of a hair follicle divide and push cells away from the

follicle. This causes hair to grow

Just note

Around the hair follicles are sebaceous glands:

These oil-producing glands lubricate skin and hair.

When glands produce too much oil, the follicles can

become inflamed and blocked. This can result in a

whitehead, a blackhead, or acne—an inflammation of

the sebaceous glands

Note

Skin regulates body temperature so when you’re cold… when yours hot

When you are cold, your muscles contract causing goose bumps. In animals, these

contractions cause hair to stand up and trap air to warm the animal. With little hair to

keep us warm, humans depend on fat in the subcutaneous layer for warmth

When you are hot, your body sweats. The evaporation of sweat cools your body.

Evaporation transfers heat energy from your body to your surroundings

Skin has an important role in vitamin D production

Skin responds to exposure to the Sun's

ultraviolet rays by producing vitamin D.

Vitamin D helps the body absorb

calcium and is essential for proper bone

formation

Skin protects our bodies, and helps us sense our surroundings

Unbroken skin keeps microorganisms out of the body.

• Skin helps maintain body temperature by preventing the loss of too much

water.

• Melanin protects from ultraviolet rays.

• Nerves in the skin relay messages about changes in the environment to the

brain. The nerves make a person aware of pain, pressure, and changes in

temperaturE

Skin serves several important functions:

1-It regulates body temperature.

2-produces vitamin D

3- protects our bodies, and helps us sense our surroundings

Damage to the Skin

Skin usually repairs itself. If it did not, the body could be

invaded by microbes through breaks in the skin.

- For minor scrapes, epidermal cells divide and replace

the injured cells.

- Deeper injuries that harm blood vessels result in bleeding.

Blood clots form a scab to close the wound. Cells beneath

the scab

divide and fill the wound, while blood cells help fight infections

How does the

ultraviolet radiation of

the sun affect the skin?

Can cause skin cancer or skin burn

Degrees of skin burn

First-degree burns :only

involve epidermal cells.

2. Second-degree burns: damage

both dermis and epidermis,

causing blisters and scars.

3. Third-degree burns: damage

muscle

tissue and nerve cells in both

layers, and skin function is lost

Skin cancer due to uv rays

Ultraviolet radiation

can damage DNA in skin cells, causing those cells to

divide uncontrollably.

This gland releases an oil

known as sebum.

Sebaceous gland

The skin has three layers

1- Epidermis

2-dermis

3-hypodermia

Skin

Skin

What layer of skin produces melanin?

Inner layer of epidermis