Ch. 5: The Integumentary System

What is the composition of skin?

Skin is composed of the epidermis, dermis, and hypodermis.

What are skin derivatives?

Structures originating from the epidermis that include sweat glands, sebaceous glands, hair and hair follicles, and nails.

What are the skin’s functions?

Protects the deeper tissues, regulates body temperature, provides cutaneous sensation, has metabolic functions, acts as a blood reservoir, and assists in excretion.

What types of barriers does skin create?

Chemical, physical, and biological barriers.

What does skin protect against?

Mechanical, chemical, bacterial, thermal damage, UV radiation, and desiccation.

How does skin regulate body temperature?

Through sweat production and blood flow regulation.

What are the skin's metabolic functions?

It synthesizes vitamin D precursor, etc.

How much blood can the skin reservoir hold?

About 5% of the body's total blood volume.

How does skin assist in excretion?

By eliminating nitrogen-containing wastes, NaCl, and H₂O.

What is the structure of the epidermis?

It consists of five strata of stratified squamous epithelium, mainly composed of keratinocytes.

What connects epidermal cells?

Desmosomes tightly connect the cells.

What are the layers of the epidermis?

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

What happens in the stratum basale?

It's the origin of keratinocytes for all superficial strata and contains melanocytes.

What do melanocytes do?

They produce melanin, which protects against UV radiation.

What is melanin?

A pigment produced by melanocytes to protect skin cells from UV radiation.

How is melanin produced?

Through the activity of tyrosinase acting on the amino acid tyrosine.

What is albinism?

A condition caused by a failure to produce tyrosinase, leading to a lack of melanin.

What is the structure of the dermis?

The dermis consists of strong, flexible connective tissue and contains two layers: the papillary and reticular layers.

What is the function of the papillary layer?

It makes up 20% of the dermis, supports and nourishes the epidermis through blood vessels, and contains dermal papillae, which increase surface area.

What are dermal papillae?

Nipple-like projections of the dermis that extend into the epidermis, increasing surface area for nutrient exchange and strengthening the bond between the two layers.

What is the function of the reticular layer?

It makes up 80% of the dermis and contains dense connective tissue, blood vessels, glands, and nerve receptors.

What is the hypodermis?

A layer that anchors skin to underlying organs, consisting mainly of adipose tissue.

What are sebaceous glands?

Glands that produce oil (sebum) to lubricate hair and skin.

Where are sebaceous (oil) glands found?

They are distributed throughout the body, except for the palms and soles of the feet.

What is acne?

A condition caused by the overproduction of sebum, often due to hormonal changes.

What are sweat (sudoriferous) glands?

Glands that help regulate body temperature through evaporative cooling.

How many sweat glands are there in the body?

Up to 3 million sweat glands distributed body-wide.

What are the two types of sweat glands?

Eccrine and apocrine glands.

What is the function of eccrine sweat glands?

They help dissipate heat through sweat.

Where are apocrine sweat glands found?

In the axillary and pubic areas.

What is the function of apocrine sweat glands?

They are activated by stress, pain, and sexual excitement and secrete fatty acids and proteins.

What are ceruminous glands?

Modified sweat glands found in the ear canal that produce cerumen (earwax).

What are mammary glands?

Modified sweat glands that produce milk.

What is hair made of?

Dead, keratinized epithelial cells.

Where is hair found?

All over the body except for the palms, soles, lips, nipples, and part of the external genitalia.

What is the structure of a hair follicle?

Tubular invaginations of the epidermis formed by mitotically active stratum basale cells.

What is the bulb of the hair follicle?

The growth zone at the inferior end of the follicle.

What is the root of the hair?

The part of the hair enclosed in the follicle.

What is the shaft of the hair?

The visible part of the hair that projects from the skin surface.

What is an arrector pili?

A smooth muscle that causes hair to stand up, causing goosebumps.

What is the clinical use of minoxidil (Rogaine)?

Treating hair loss.

What are nails made of?

Hard keratin that is attached to the nail bed.

What is the eponychium?

The cuticle, or the skin at the base of the nail.

What is the lanula?

The crescent-shaped area at the proximal end of the nail bed, visible through the nail.

What is eponychitis?

An infection of the eponychium (cuticle).

What are the clinical applications of skin?

Injection sites, blisters, lines of cleavage, stretch marks, decubitus ulcers (bed sores), burns, and skin cancer.

What are the types of skin injections?

Intradermal (ID), subcutaneous (SQ), intramuscular (IM), and intravenous (IV).

What is a blister?

A fluid-filled pocket between the epidermis and dermis.

What are lines of cleavage?

Collagen and elastic fibers in the dermis that align to resist stresses.

What are stretch marks?

Marks caused by the overstretching of the skin.

What are decubitus ulcers (bed sores)?

Wounds caused by restricted blood flow, leading to tissue death and bacterial infections.

What is the Rule of Nines?

A method for estimating the extent of burns.

What percentage of the body does the head account for in the Rule of Nines?

The head accounts for 9% of the body (4.5% for the front and 4.5% for the back).

What percentage of the body does each arm account for in the Rule of Nines?

Each arm accounts for 4.5% of the body (2.25% for the front and 2.25% for the back).

What percentage of the body does the torso account for in the Rule of Nines?

The torso accounts for 36% of the body (18% for the front and 18% for the back).

What percentage of the body does each leg account for in the Rule of Nines?

Each leg accounts for 9% of the body (4.5% for the front and 4.5% for the back).

What percentage of the body does the perineum account for in the Rule of Nines?

The perineum accounts for 1% of the body.

How do you add up the percentages in the Rule of Nines?

Add the percentages for each burned area. (e.g., head (9%) + both arms (4.5% each) = 18%)

What is the total percentage for the Rule of Nines?

The total percentage for the Rule of Nines is 100%.

What are the three degrees of burns?

First-degree, second-degree, and third-degree burns.

What are the characteristics of first-degree burns?

They affect only the epidermis, causing redness, pain, and swelling, usually healing in 2-3 days.

What are the characteristics of second-degree burns?

They affect the epidermis and dermis, causing redness, pain, swelling, and blistering, healing in 3-4 weeks.

What are the characteristics of third-degree burns?

They cause total tissue destruction, with discoloration but no pain, requiring skin grafts.

What is the most common type of skin cancer?

Basal cell carcinoma.

What is basal cell carcinoma?

A cancer that arises from the stratum basale and appears as a shiny, dome-shaped nodule, which is the least dangerous and rarely metastasizes.

What is squamous cell carcinoma?

A cancer that arises from the stratum spinosum, resulting in a scaly, reddened papule, and is more dangerous with a higher potential to metastasize if untreated.

What is malignant melanoma?

The deadliest form of skin cancer, with a 90% mortality rate, arises from melanocytes and rapidly metastasizes.

What is the ABCDE rule for detecting melanoma?

A method to evaluate moles: (A) Asymmetry, (B) Border irregularity, (C) Color, (D) Diameter greater than 6mm, and (E) Elevation/Evolution.