Exam 2

Major components of the integumentary system

Epidermis, dermis, hypodermis, hair, nails, and cutaneous glands.

6 primary functions of the integumentary system

Protection, body temperature regulation, cutaneous sensation, metabolic functions (vitamin D synthesis), blood reservoir, and excretion.

Main function of the epidermis

Provides a protective, waterproof barrier against pathogens, chemicals, UV radiation, and water loss.

Main functions of the dermis

Provides strength, elasticity, nourishment to the epidermis, sensation, and thermoregulation.

What is the hypodermis?

A layer of connective tissue and adipose tissue deep to the dermis that anchors the skin and provides insulation and energy storage.

What type of epithelium is the epidermis?

Keratinized stratified squamous epithelium.

Is the epidermis vascular or avascular?

Avascular.

How does the avascular epidermis receive nutrients?

Nutrients and oxygen diffuse from capillaries in the dermis through tissue fluid into the epidermis.

5 epidermal layers from deep to superficial

Stratum basale → stratum spinosum → stratum granulosum → stratum lucidum → stratum corneum.

Deepest layer of the epidermis

Stratum basale.

Most superficial layer of the epidermis

Stratum corneum.

Main features of the stratum basale

Contains stem cells and actively dividing keratinocytes; also contains melanocytes and Merkel cells.

Function of the stratum basale

Produces new keratinocytes and anchors the epidermis to the basement membrane.

Main feature of the stratum spinosum

Keratinocytes are connected by strong desmosomes, giving the cells a spiny appearance.

Function of the stratum spinosum

Provides strength and begins keratin production; contains many dendritic cells.

Main features of the stratum granulosum

Keratinocytes accumulate keratin and waterproofing lipids and begin to die.

Function of the stratum granulosum

Helps create the waterproof barrier of the epidermis.

Where is the stratum lucidum found?

Only in thick skin.

What is the stratum lucidum?

A thin layer of dead, flattened keratinocytes between the stratum granulosum and stratum corneum.

What is the stratum corneum?

The outermost layer consisting of many layers of dead, flattened, keratin-filled cells.

Function of the stratum corneum

Provides protection and limits water loss.

What is keratinization?

The process in which keratinocytes produce keratin, flatten, die, and move toward the skin surface.

Why is keratinization important?

Keratin strengthens and waterproofs the epidermis and protects against physical damage, pathogens, and water loss.

What is desquamation?

The shedding of dead keratinized cells from the surface of the stratum corneum.

How long does the epidermal life cycle generally take?

About 4 weeks from the basal layer to the surface and shedding.

4 major epidermal cell types

Keratinocytes, melanocytes, dendritic (Langerhans) cells, and tactile (Merkel) cells.

Most common epidermal cell

Keratinocyte.

Function of keratinocytes

Produce keratin and form the protective epidermal barrier.

Function of melanocytes

Produce melanin, which helps protect DNA from UV radiation.

Location of melanocytes

Primarily in the stratum basale.

Function of dendritic (Langerhans) cells

Immune defense; detect and help respond to pathogens.

Primary location of dendritic cells

Primarily the stratum spinosum.

Function of Merkel cells

Detect light touch.

Location of Merkel cells

Stratum basale.

Where is thick skin found?

Palms of the hands and soles of the feet.

Where is thin skin found?

Most of the rest of the body.

Does thick skin contain a stratum lucidum?

Yes.

Does thin skin contain a stratum lucidum?

No.

Does thick skin contain hair follicles?

No.

Does thick skin contain sebaceous glands?

No.

Which type of skin has more sweat glands?

Thick skin generally has more sweat glands.

Why is thick skin especially useful on the palms and soles?

It provides greater protection against friction and mechanical stress.

What triggers vitamin D synthesis in the skin?

UVB radiation from sunlight.

What precursor is converted during vitamin D synthesis in the skin?

7-dehydrocholesterol.

What is the vitamin D pathway?

Skin → liver → kidneys → active vitamin D.

What does the liver convert vitamin D into?

Calcidiol.

What does the kidney convert vitamin D into?

Calcitriol.

What is the active form of vitamin D?

Calcitriol.

Main function of calcitriol

Increases intestinal absorption of calcium and phosphate and supports bone health.

Where is the dermis located?

Deep to the epidermis and superficial to the hypodermis.

2 layers of the dermis

Papillary layer and reticular layer.

Which dermal layer is superficial?

Papillary layer.

Which dermal layer is deeper and thicker?

Reticular layer.

What type of connective tissue makes up the papillary layer?

Areolar connective tissue.

What type of connective tissue makes up the reticular layer?

Dense irregular connective tissue.

Structures found in the papillary layer

Dermal papillae, capillaries, sensory receptors, and immune cells.

Structures found in the reticular layer

Larger blood vessels, nerves, hair follicles, sweat glands, and sebaceous glands.

Function of collagen fibers in the dermis

Provide strength and resist stretching and tearing.

Function of elastic fibers in the dermis

Allow skin to stretch and return toward its original shape.

How does the dermis contribute to thermoregulation?

Dermal blood vessels dilate or constrict to increase or decrease heat loss.

How does the dermis contribute to sensory perception?

It contains sensory receptors that detect touch, pressure, pain, temperature, stretch, and vibration.

Major sensory receptors of the skin

Free nerve endings, Merkel discs, Meissner corpuscles, Pacinian corpuscles, Ruffini endings, and hair follicle receptors.

What do free nerve endings detect?

Pain, temperature, and itch.

What do Merkel discs detect?

Light touch and sustained pressure.

What do Meissner corpuscles detect?

Light touch and texture.

What do Pacinian (lamellated) corpuscles detect?

Deep pressure and vibration.

What do Ruffini endings detect?

Skin stretch.

What do hair follicle receptors detect?

Hair movement.

What tissues make up the hypodermis?

Areolar and adipose connective tissue.

Major functions of the hypodermis

Insulation, energy storage, shock absorption, stabilization/anchoring of skin, and a site for subcutaneous injections.

Is the hypodermis technically part of the skin?

No. It lies deep to the skin.

Major types of integumentary glands

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

What do sebaceous glands produce?

Sebum.

Functions of sebum

Lubricates and waterproofs skin and hair and inhibits some bacterial growth.

Where do sebaceous gland ducts usually empty?

Into hair follicles.

Where are sebaceous glands absent?

Palms and soles.

What do eccrine sweat glands produce?

Watery sweat.

Primary function of eccrine sweat glands

Thermoregulation through sweat production and evaporation.

Where do eccrine sweat ducts open?

Directly onto the skin surface.

Where are eccrine sweat glands widely distributed?

Throughout the body, especially the palms, soles, and forehead.

Where are apocrine sweat glands primarily located?

Axillary and anogenital regions.

Where do apocrine sweat gland ducts empty?

Into hair follicles.

When do apocrine glands become active?

At puberty.

What is the function of apocrine sweat glands?

Produce a thicker secretion involved in body odor and chemical signaling.

What do ceruminous glands produce?

Cerumen (earwax).

Function of cerumen

Protects and lubricates the external auditory canal and helps trap debris.

What are mammary glands?

Modified sweat glands that produce milk.

How does sweating cool the body?

Sweat evaporates from the skin surface, removing heat.

What happens to dermal blood vessels when the body needs to lose heat?

They dilate, increasing blood flow near the skin surface.

What happens to dermal blood vessels when the body needs to conserve heat?

They constrict, reducing blood flow near the skin surface.

Why is cardiovascular function important for thermoregulation?

Blood transports heat from the body's core to the skin for release.

Major stages of wound healing

Inflammation → proliferation/organization → regeneration/fibrosis → remodeling.

What happens during inflammation in wound healing?

Blood vessels dilate, clotting occurs, and immune cells remove pathogens and debris.

What happens during the proliferative phase of wound healing?

Fibroblasts produce collagen, new blood vessels form, and epithelial cells regenerate.

What happens during remodeling?

Collagen is reorganized and repaired tissue gains strength.

What is a first-degree burn?

Damage limited to the epidermis; skin is red and painful, with no significant blistering; heals without significant scarring.

What is a second-degree burn?

Damage extends into the dermis; skin is painful, red, swollen, and blistered.

What is a third-degree burn?

Full-thickness destruction of the epidermis and dermis; skin may appear white, brown, black, or leathery.

Which burn has the greatest tissue damage?

Third-degree/full-thickness burn.

Why may third-degree burns be painless?

Nerve endings are destroyed.