Integumentary Tissue - Chad A&P Lecture

What are the main functions of the integumentary system?

• Protection

• Sensation

• Temperature regulation

• Vitamin D production

• Excretion

What are the two main layers of the skin?

• Epidermis → epithelial tissue

• Dermis → connective tissue

• Subcutaneous tissue (hypodermis) is underneat but not officially part of the skin

What are the important characteristics of the epidermis?

• Made of epithelial tissue

• avascular → no direct blood supply

• Innervated → has nerve endings

• Gets nutrients through diffusion

• Separated from the dermis by the basement membrane

Identify the layers of the epidermis from deep to superficial

stratum basale → stratum spinosum → stratum grandulosum → stratium lucidum → stratum corneum

What does the integumentary system protect the body from?

Physical injury, ultraviolet radiation, microorganisms, and water/fluid loss

What are the two main layers of skin?

Epidermis → epithelial tissue

Dermis → connective tissue

What is the subcutaneous tissue(hypodermis)?

Loose connective tissue, especially adipose tissue, located below the dermis. It is not officially part of the skin

What separates the epidermis from the dermis?

The basement membrane

What are the four major cell types of the epidermis?

Keratinocytes, melanocytes, epidermal dendritic cells, and Merkel (tactile) cells

What are keratinocytes?

The most common cells of the epidermis. They produce keratin, which provides strength and helps prevent water loss

What are melanocytes?

Cells that produce melanin, which contributes to skin color and protects against ultraviolet radiation

What do epidermal dendritic cells and Merkel cells do?

• Epidermal dendritic cells → immune defense

• Merkel cells → detect light touch

What are the five epidermal layers from deep to superficial?

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum

5. stratum corneum

What happens in the stratum basale?

It is the deepest epidermal layer. Cells divide rapidly by mitosis to produce new epidermal cells

How is the stratum basale attached to the basement membrane?

Hemidesmosomes attach the cells to the basement membrane. Desmosomes connect cells to each other

What happens when a cell in the stratum basale divides?

One daughter cell remains attached to the basement membrane while the other moves toward the surface

How quickly are epidermal cells replaced according to the lecture?

Basal cells divide about every 19 days, and a cell takes about 40-56 days to travel from the stratum basale to the surface

What happens in the stratum spinosum?

Living keratinocytes remains metabolically active and develop lamellar bodies. It is about 8-10 layers thick

What are lamellar bodies?

Lipid-filled structures that help form the skin’s water barrier

What happens in the stratum granulosum?

Cells become flatter accumulate keratohyalin granules, and begin dying

Why do epidermal cells die as they move toward the surface?

They become too far from the dermal blood supply to receive enough nutrients by diffusion

What is the stratum lucidum?

A clear layer found only in the thick skin

What are calluses and corns?

• Callus → thickening of the stratum corneum from repeated friction

• Corn → localized thick callus over a bony prominence

Do people with different skin colors have different numbers of melanocytes?

No. Melanocytes package melanin into melanosomes, which are transferred into keratinocytes. Everyone has the same amount of melanocyte, just produce different type of melanin

What stimulates melanocytes to produce more melanin?

Ultraviolet radiation. More ultraviolet exposure stimulates more mlanin production.

What is the relationship between melanin, ultraviolet radiation, and vitamin D?

More melanin provides greater protection from ultraviolet radiation, but it also decreases ultraviolet penetration needed to begin vitamin D production.

What are the three skin cancers discussed in lecture?

Basal cell carcinoma, squamous cell carcinoma, and melanoma

What is basal cell carcinoma?

Cancer involving cells of the stratum basale. It is the most common skin cancer discussed in lecture

What is squamous cell carcinoma?

Cancer involving squamous epidermal cells; associated with the stratum spinosum

What is melanoma? Why is it especially dangerous?

Cancer of melanocytes. It can metastasize because melanocytes are near the basement membrane and the blood vessels of the dermis.

ABCDE?

A → Asymmetry

B → Border irregularity

C → Color variation

D → Diameter greater than 6 millimeters

E → Evolving/changing

What structures are found in the dermis?

Blood vessels, nerves, hair follicles, smooth muscle, glands, and lymphatic vessels

What are the two layers of the dermis?

Papillary layer → superficial

Reticular → deeper

What are the dermal papillae?

Finger-like projections of the papillary dermis into the epidermis. Their arrangements helps form fingerprints

What are Meissner corpuscles?

Sesnsory receptors in the papillary dermis that detect light touch.

What is the reticular layer made of, and why?

Dense irregular connective tissue because the skin needs to resist pulling forces from many directions.

What are Pacinian (lamellated) corpuscles?

Deeper sensory receptors that detect deep pressure

How does bleeding differ between epidermal and dermal injuries?

• Epidermis only → no bleeding because it is avascular

• Into dermis → bleeding because the dermis contains blood vessels

What are cleavage lines?

Lines created by the orientation of collagen and elastic fibers. Surgical cuts made parallel to them generally heal better

What causes stretch marks?

Excessive stretching of skin that affects connective tissue along cleavage lines.

What are the three types of hair?

• Lanugo → fine fetal hair

• Terminal hair → long, coarse, pigmented hair

• Vellus hair → fine, short body hair

What are the hair shaft and hair root?

Shaft → part above the skin

Root → part below the skin

What is hair made of, and what determines its color?

Hair is made of dead, keratinized cells. Its color is determined by melanin

What is the hair papilla?

A projection at the base of the hair containing blood vessels that provide nutrients for hair growth.

What is the arrector pili muscle?

An involuntary smooth muscle attached to hair follicle that causes the hair to stand up.

What are the three skin glands discussed in lecture?

Sebaceous glands, apocrine sweat glands, and eccrine sweat glands.

What are sebaceous glands?

Holocrine glands that release sebum (oil) into hair follicles to lubricate the hair and skin

What are aprocine sweat glands?

Sweat glands that:

• Empty into hair follicles

• Are common in the axillae and genital regions

• Become active at puberty

• Are not primarily for temperature regulation

Why is apocrine sweat associated with body oder?

The secretion itself is not strongly odorous. Bacteria acting on the secretion produce the odor.

What are eccrine sweat glands?

Sweat glands that open directly onto the skin surface and primarily help regulate body temperature. They are especially abundant on the palms and soles.

What are nails made of?

Dead, keratinized cells

How does the skin regulate body temperature through blood vessels?

• Superficial blood vessels dilate → more heat loss

• Superficial blood vessels constrict → less heat loss

Where does vitamin D production begin?

In the skin. Further processing occurs in the liver and kidneys.

What is the difference first-, second-, and third-degree burns?

• First-degree → primarily epidermis

• Second-degree → epidermis + part of dermis

• Third-degree → full thickness of skin and may extend into subcutaneous tissue

Why can the center of a third-degree burn have little to no pain?

The sensory nerve endings, in that area may have been destroyed.

Why tattoo ink placed in the dermis instead of the epidermis?

Epidermal cells are continually replaced and shed. The dermis turns over much more slowly, allowing the tattoo to remain

How does tattoo ink stay in the dermis?

Macrophages engulf the ink particles but cannot easily remove them, so pigment-containing macrophages remain in the dermis. Over time, pigment redistribution can make tattoos fade or blur

Identify the papillary and reticular layers of the dermis

Papillary = superficial and contains dermal papillae. Reticular = deeper and thicker

Identify Meissner vs. Pacinian corpuscles

Meissner = superficial, light touch. Pacinian = deeper, deep pressure

Identify a sebaceous gland

Oil-producing gland connected to and emptying to a hair follicle

Identify eccrine vs. apocrine sweat glands

Eccrine → duct opens directly onto skin surface

Apocrine → duct opens into a hair follicle

Identify the arrector pili muscle

Small band of smooth muscle attached to a hair follicle