CHAPTER 6 - Integumentary System

What are the four components of the integumentary system?

Skin, hair, nails, and associated exocrine glands.

What are the three layers of the skin?

Epidermis, dermis, and hypodermis (subcutaneous layer).

What is fascia?

Connective tissue that connects the skin to underlying muscles and other structures.

What are the main functions of the integumentary system?

Protection from pathogens and UV radiation, fluid balance, energy storage, vitamin D production, sensory input, and temperature regulation.

How does the skin protect the body?

It forms a physical barrier against pathogens, injury, water loss, and UV radiation.

How does the skin help regulate body temperature?

Sweat evaporates to cool the body, and skin blood vessels widen to release heat or narrow to conserve heat.

What does the skin produce that helps the body absorb calcium?

Vitamin D, which helps the intestines absorb calcium.

What are the four major sensory receptors of the skin?

Thermoreceptors, nociceptors, tactile corpuscles, and lamellated (Pacinian) corpuscles.

What do thermoreceptors detect?

Heat and cold.

What do nociceptors detect?

Pain.

What do tactile (Meissner) corpuscles detect?

Light touch and light pressure.

What do lamellated (Pacinian) corpuscles detect?

Deep pressure and vibration.

What is the epidermis?

The most superficial layer of the skin.

What type of tissue makes up the epidermis?

Keratinized stratified squamous epithelium.

What does it mean that the epidermis is avascular?

It has no blood vessels and receives nutrients by diffusion from the underlying dermis.

What is the difference between thick skin and thin skin?

Thick skin has five epidermal layers and is found on the palms and soles

Which has more epidermal layers, thick or thin skin?

Thick skin.

Which type of skin is found on the palms and soles?

Thick skin.

Which type of skin covers most of the body?

Thin skin.

What are the five epidermal layers from deepest to most superficial?

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

What are the four epidermal layers found in thin skin, from deepest to most superficial?

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

Which epidermal layer is absent in thin skin?

Stratum lucidum.

What is the stratum basale?

The deepest epidermal layer, where new keratinocytes are produced

What is another name for the stratum basale?

Stratum germinativum.

What is the main function of the stratum basale?

To continually produce new epidermal cells that replace older cells.

What are epidermal stem cells?

Self-renewing cells, primarily in the stratum basale, that divide to produce new keratinocytes.

What is the stratum spinosum?

The epidermal layer above the basale that contains keratinocytes and immune cells, including Langerhans cells.

What are Langerhans cells?

Immune cells that detect foreign substances and help activate immune responses in the skin.

What is the stratum granulosum?

The layer where keratinization becomes prominent and cells flatten, lose their nuclei, and begin to die.

What happens during keratinization?

Keratinocytes accumulate keratin, flatten, and eventually become dead, protective cells at the skin surface.

What are melanosomes?

Small cellular structures that store and transport melanin pigment.

What is the stratum lucidum?

A thin layer of tightly packed dead keratinocytes found only in thick skin on the palms and soles.

What is eleidin?

A substance found in the stratum lucidum that contributes to the skin's water-resistant barrier.

What is the stratum corneum?

The outermost epidermal layer, made of approximately 15–30 layers of dead, flattened, keratin-filled cells.

What is the main function of the stratum corneum?

To provide a tough, water-resistant protective barrier.

What are keratinocytes?

The main cells of the epidermis

What is keratin?

A tough, fibrous intracellular protein that strengthens and helps waterproof skin, hair, and nails.

How do keratinocytes move through the epidermis?

They are produced in the deepest layer and gradually migrate toward the surface as they mature.

What are melanocytes?

Cells that produce melanin pigment.

What is melanin's main function?

It helps protect skin-cell DNA from UV radiation and helps prevent UV-related breakdown of folic acid.

What are the two main types of melanin?

Eumelanin and pheomelanin.

What color is eumelanin?

Brown to black.

What color is pheomelanin?

Yellowish to reddish.

Why do people have different skin tones?

Mainly because of differences in melanin type, amount, distribution, and how melanosomes are produced and processed—not simply the number of melanocytes.

Do people with different skin tones necessarily have different numbers of melanocytes?

No. People generally have similar numbers of melanocytes, but their melanin production and distribution differ.

What are Merkel cells?

Sensory cells in the stratum basale involved in detecting sustained, fine or discriminatory touch.

What is a Merkel disc?

A sensory nerve ending associated with a Merkel cell that helps detect light touch, texture, and fine details.

What is the dermis?

The connective-tissue layer beneath the epidermis that provides strength, elasticity, nutrients, and support.

What structures are found in the dermis?

Blood vessels, nerves, sensory receptors, hair follicles, glands, collagen fibers, and elastic fibers.

Why does the dermis nourish the epidermis?

The dermis contains blood vessels that supply nutrients and oxygen, which diffuse into the avascular epidermis.

What are collagen fibers?

Protein fibers that provide tensile strength and structural support to the skin.

What are elastic fibers?

Fibers that allow skin to stretch and return toward its original shape.

Which cells produce collagen and elastic fibers in the dermis?

Fibroblasts.

What are the two layers of the dermis?

The papillary layer and the reticular layer.

What is the papillary layer?

The thinner, more superficial dermal layer made of loose areolar connective tissue.

What is the reticular layer?

The deeper, thicker dermal layer made of dense irregular connective tissue.

What is the difference between the papillary and reticular layers?

The papillary layer is superficial and contains loose areolar connective tissue

What are dermal papillae?

Fingerlike projections of the dermis that extend into the epidermis.

What are the functions of dermal papillae?

They anchor the epidermis to the dermis, help prevent separation, and contain capillaries and sensory receptors.

How are dermal papillae related to fingerprints?

Their patterns contribute to the ridges that form fingerprints.

Where are Meissner (tactile) corpuscles commonly found?

In the dermal papillae, where they detect light touch.

Where are Pacinian corpuscles commonly found in the skin?

In the deeper dermis and hypodermis, where they detect deep pressure and vibration.

What is the hypodermis?

The subcutaneous layer beneath the dermis, composed mainly of adipose tissue and loose areolar connective tissue.

What are the functions of the hypodermis?

It cushions the body, stores energy as fat, provides insulation, and helps attach the skin to underlying structures.

Is the hypodermis technically part of the skin?

Strictly speaking, the skin consists of the epidermis and dermis

Why is the hypodermis highly vascularized?

Its blood vessels supply the region and help support temperature regulation and tissue metabolism.

What is brown fat, and why is it important in infants?

Brown adipose tissue produces heat and helps infants maintain body temperature.

What is the correct order of tissues cut during a typical incision from the skin inward?

Epidermis, dermis, hypodermis, and then deeper connective tissue such as fascia.

Why does a cut limited to the epidermis usually not bleed?

The epidermis has no blood vessels.

If a cut bleeds, which skin layer has definitely been injured?

The dermis or deeper tissue, because blood vessels are located beneath the epidermis.

What is the main difference between the epidermis and dermis?

The epidermis is avascular epithelial tissue

What are extracellular lipids in the epidermis?

Lipids released between epidermal cells, especially in the stratum granulosum, that form a water-resistant barrier and reduce water loss.

Where do many of the epidermal barrier lipids come from?

Lamellar bodies in keratinocytes of the stratum granulosum release lipids into the spaces between cells.

Why are extracellular lipids important?

They help prevent excessive water loss and limit the entry of irritants and pathogens.

What is the skin's acid mantle?

A slightly acidic film on the skin surface that supports the protective barrier and helps limit the growth of some harmful microbes.

What are the accessory structures of the skin?

Hair, nails, sweat glands, and sebaceous glands.

What is hair made of?

Dead, keratinized cells derived from the epidermis.

What are four functions of hair?

Physical protection, sensory input, thermoregulation, and UV protection.

What is the hair papilla?

A structure at the base of the hair follicle that contains blood vessels supplying the growing hair.

What is the hair bulb?

The enlarged, deepest portion of the hair follicle.

What is the hair root?

The portion of the hair located 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 from center outward?

Medulla, cortex, and cuticle.

What is the medulla of a hair?

The innermost central region of the hair shaft.

What is the cortex of a hair?

The layer surrounding the medulla that makes up most of the hair shaft and contributes to its strength and color.

What is the cuticle of a hair?

The outermost layer of overlapping protective cells surrounding the cortex.

What is the hair follicle?

A tube-like epidermal structure that surrounds the hair root and anchors the hair.

What is the hair matrix?

A region of actively dividing cells in the hair bulb that produces new hair cells.

How does hair grow?

Cells in the hair matrix divide, and the new cells become keratinized and push older cells outward.

Is hair growth continuous?

No. Hair follicles cycle through growth, transition, and resting phases.

What is the function of the arrector pili muscle?

It contracts to make a hair stand up, producing goosebumps.

What do sebaceous glands associated with hair follicles secrete?

Sebum, an oily substance that lubricates and helps waterproof the skin and hair.

What are nails made of?

Hard, keratinized epidermal cells.

What is the nail body?

The visible, hard portion of the nail.

What is the nail bed?

The skin tissue beneath the nail body

What is the nail root?

The proximal part of the nail where growth begins.

What produces most of the nail body?

The nail matrix, a growth region near the nail root.

What is the eponychium?

The cuticle, a thin layer of skin at the base of the nail.

What is the lunula?

The pale, crescent-shaped area near the base of the nail, visible part of the nail matrix.

What are sweat glands also called?

Sudoriferous glands.