a&p integument system

What is the cutaneous membrane?

The skin; composed of the epidermis and dermis along with accessory structures such as hair, nails, sweat glands, and sebaceous glands.

What are the accessory structures of the integumentary system?

Hair, nails, sweat glands, sebaceous glands (oil glands), and ceruminous glands.

What is the surface film?

A protective layer made of sweat, sebum, desquamated cells, microorganisms, and other chemicals that coats the skin.

What makes up the surface film?

Sweat, sebum (oil), shed dead skin cells, microorganisms, and antimicrobial chemicals.

What are the two types of skin?

Thick skin and thin skin.

Where is thick skin found?

Palms of the hands and soles (plantar surface) of the feet.

How many epidermal layers does thick skin have?

Five layers.

Does thick skin contain hair?

No, thick skin is hairless.

How many epidermal layers does thin skin have?

Four layers because it lacks the stratum lucidum.

Where is thin skin found?

Covers most of the body.

What is the epidermis?

The superficial layer of the skin made of keratinized stratified squamous epithelium.

What type of tissue makes up the epidermis?

Keratinized stratified squamous epithelium.

What are keratinocytes?

The most abundant epidermal cells that produce keratin.

What is keratin?

A tough structural protein that provides strength and water resistance.

What are melanocytes?

Cells that produce the pigment melanin.

Where are melanocytes located?

In the stratum basale.

What are dendritic (Langerhans) cells?

Immune cells that initiate immune responses.

What are tactile (Merkel) cells?

Sensory receptor cells involved in touch sensation.

How many layers (strata) are in the epidermis of thick skin?

Five.

List the five layers of the epidermis from deep to superficial.

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

What is the deepest epidermal layer?

Stratum basale.

What is the function of the stratum basale?

Contains stem cells that continually produce new keratinocytes.

Which epidermal layer is the thinnest?

Stratum basale.

What is the stratum spinosum?

The layer above the basale that is about 8–10 keratinocyte layers thick.

How thick is the stratum spinosum?

Approximately 8–10 cell layers.

What is the stratum granulosum?

A layer where keratinization increases and cells begin to die.

How thick is the stratum granulosum?

Approximately 2–4 cell layers.

Why do cells die in the stratum granulosum?

They are too far from the blood supply to receive nutrients.

Where is the stratum lucidum found?

Only in thick skin.

How thick is the stratum lucidum?

About 2–3 cell layers.

What is the function of the stratum lucidum?

Provides extra protection in thick skin.

What is the stratum corneum?

The outermost epidermal layer made of dead keratinized cells.

How thick is the stratum corneum?

Approximately 20–30 layers of dead cells.

How long do epidermal cells typically live?

About 3 weeks.

What is the dermoepidermal junction?

A specialized basement membrane that connects the epidermis and dermis.

What is unique about the dermoepidermal junction?

It contains fibrous elements and thick gelatinous ground substance rich in polysaccharides.

What is the dermis?

The true skin (corium) beneath the epidermis.

What is another name for the dermis?

Corium.

What tissue makes up the papillary layer?

Areolar connective tissue.

Which dermal layer is superficial?

Papillary layer.

What are dermal papillae?

Finger-like projections that increase surface area between the epidermis and dermis.

What are friction ridges?

Ridges formed by dermal papillae that create fingerprints.

What is the papillary plexus?

A network (braid) of blood vessels between the papillary and reticular layers.

Which dermal layer is thicker?

Reticular layer.

What tissue makes up the reticular layer?

Dense irregular connective tissue with elastic fibers.

Which dermal layer makes up most of the dermis?

Reticular layer.

Why is the reticular layer strong?

It contains dense irregular collagen fibers.

What are cleavage lines?

Lines showing the general arrangement of collagen fibers in the dermis.

What is the cutaneous plexus?

A network of blood vessels at the bottom of the reticular layer.

What is the hypodermis?

The subcutaneous layer (superficial fascia) beneath the skin.

Is the hypodermis part of the cutaneous membrane?

No; it is part of the integument but not the cutaneous membrane.

What tissues make up the hypodermis?

Areolar connective tissue and adipose tissue.

Why is the hypodermis an ideal injection site?

It contains loose connective tissue and fat for subcutaneous injections.

What is the main determinant of skin color?

The amount and type of melanin.

Where is melanin produced?

By melanocytes in the stratum basale.

Do all humans have about the same number of melanocytes?

Yes; skin color differences are mainly due to melanin production.

What is beta-carotene?

A yellow pigment found in vegetables that contributes to skin color.

What is lipofuscin?

A brown-yellow pigment that accumulates with aging and contributes to age spots.

What gives blood its red color?

Hemoglobin.

What are the major functions of the skin?

Protection, sensation, flexibility, excretion, vitamin D production, immunity, and temperature regulation.

How does the skin provide protection?

Acts as a physical barrier with tight junctions that keeps harmful substances out and body fluids in.

Where are sensory receptors found in the skin?

In both the epidermis and dermis.

What provides flexibility to the skin?

Elastic fibers.

How does the skin contribute to excretion?

Through sweat; although it plays only a minor role.

How does the skin produce vitamin D?

UV light acts on cells in the stratum basale and spinosum.

Why is vitamin D important?

It promotes calcium absorption and deposition in the skeleton.

How does the skin contribute to immunity?

Dendritic cells help initiate immune responses.

How does the skin regulate body temperature?

By sweating, adjusting blood flow, and insulation from adipose tissue.

Approximately what percentage of heat loss occurs through the skin?

About 80%.

How do blood vessels regulate temperature?

They dilate to lose heat and constrict to conserve heat.

What is evaporative cooling?

Heat loss caused by evaporation of sweat.

How does adipose tissue help regulate body temperature?

It insulates the body.

What part of the brain acts as the body's thermostat?

The hypothalamus.

How is body temperature regulated?

By a negative feedback loop controlled by the hypothalamus.

Approximately how many hairs are on the human body?

About 5 million.

What is lanugo hair?

Fine fetal hair that is usually shed after birth.

What is vellus hair?

Fine "peach fuzz" hair covering most of the body.

What is terminal hair?

Coarse, thick hair found in specific regions such as the scalp, eyebrows, axillae, and pubic region.

What is a hair follicle?

The structure in the skin from which hair grows.

What are the parts of the hair follicle?

Outer dermal root sheath, epidermal root sheath, hair papilla, and germinal matrix.

What is the hair papilla?

A connective tissue projection supplying nutrients to growing hair.

What is the germinal matrix?

Rapidly dividing cells responsible for hair growth.

What is the hair root?

The portion of hair below the skin surface.

What is the hair shaft?

The visible portion of hair above the skin surface.

What are the three layers of the hair shaft?

Medulla, cortex, and cuticle.

What is the medulla?

The central core of the hair shaft.

What is the cortex?

The thick middle layer containing most of the hair's pigment.

What is the cuticle of hair?

The outer protective layer of overlapping cells.

What is the arrector pili muscle?

A smooth muscle that raises the hair, producing goosebumps.

What is the hair root plexus?

A sensory nerve network around the hair follicle that detects hair movement.

What are sebaceous glands?

Oil glands that produce sebum.

What secretion do sebaceous glands use?

Holocrine secretion.

What is sebum?

An oily secretion that lubricates skin and hair.

What are the functions of sebum?

Keeps skin soft and flexible and reduces water loss.

Sebaceous glands are usually associated with what structure?

Hair follicles.

What are sudoriferous glands?

Sweat glands.

What are the two types of sweat glands?

Eccrine and apocrine.

Which sweat gland is most common?

Eccrine sweat gland.

What type of secretion do eccrine glands use?

Merocrine secretion.

What is the primary function of eccrine sweat glands?

Evaporative cooling.