BIO65 || CH5: The Integumentary System

Integumentary System

Comprises the skin (integument), hair, nails, & cutaneous glands; the body's largest organ.
Made of two layers: Epidermis & Dermis

Epidermis

The epithelium layer of the skin; Consists of keratinized stratified squamous epithelium, avascular (no blood supply), with sparse nerve endings.

Dermis

The connective tissue layer of the skin.
Rich in collagen fibers, with two layers: Papillary layer & Reticular layer.

Hypodermis

Connective tissue just underneath the skin, not part of the integumentary system.

Thin Skin

Covers most of the body, hairy, with sebaceous oil glands & sweat glands.

Thick Skin

Found in specific areas like palms, soles of feet, and fingers, hairless with sweat glands, adapted for high friction.

Functions of the Skin

Include resistance to trauma & infection, water retention, synthesis of vitamin D, sensation, thermoregulation, and nonverbal communication.

Eccrine Sweat Glands

Glands that secrete sweat.

Apocrine Sweat Glands

Glands that provide an oily substance, generally sticking to hair.

Keratinocytes

Cells that synthesize the fibrous protein keratin, found in many layers of the epidermis; only found in stratum basale

Melanocytes

Cells that produce melanin, a pigment that protects DNA from ultraviolet radiation.

Tactile (Merkel) Cells

Touch receptors that aid in sensation.

Dendritic (Langerhans) Cells

Cells involved in immune surveillance and the immune system.

Layers of the Epidermis

Include Stratum Basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidum (ONLY INTHICK SKIN) , and Stratum Corneum.

Where is the hypodermis located?

Below the dermis

What types of tissues are found in the hypodermis?

Adipose and areolar connective tissue

What are the functions of the hypodermis?

Energy storage, thermal insulation, and connection to deeper tissue

Skin Color

Determined by melanin, hemoglobin, and carotene; varies across individuals.

Diagnostic Skin Colors

Include Cyanosis, Erythema, Pallor, Albinism, Jaundice, and Hematoma.

Skin Markings

Such as friction ridges, flexion lines, freckles, and moles.

Hair

An accessory organ of the skin, filament of keratinized cells that grows from hair follicles; grows on thin skin

Three Types of Hair

Include Downy Hair, Vellus Hair, and Terminal Hair.

Structure of the Hair & Follicle

Comprises the bulb, root, shaft, medulla, cortex, cuticle, hair follicle, hair receptors, and arrector muscle.

Nails

Derivative of the stratum corneum, composed of thin, dead, scaly cells with parallel rows of keratin.

Sweat (Sudoriferous) Glands

Include Eccrine (merocrine) glands, Apocrine glands, Sebaceous glands, Ceruminous glands, and Mammary glands.

Skin Cancer

Induced by UV rays, with three main types: Basal cell carcinoma, Squamous cell carcinoma, and Malignant melanoma.

Burns

Leading cause of accidental death, categorized into First-Degree, Second-Degree, and Third-Degree burns.

Cells Types of the Epidermis

Keratinocytes, Melanocytes, Tactile (Merkel) cells, Dendritic (Langerhans) cells

THICK SKIN LAYERS MNEUMONIC

Come, Let's Get Sun Burned

THIN SKIN LAYERS MNEUMONIC

Careful, Getting Sun Burned

Stratum Corneum

the most superficial layer of the epidermis consisting of dead cells

What makes the Stratum Corneum water-repellant?

Lamellar granules in this layer

How are dead cells in the Stratum Corneum replaced?

These dead cells are shed constantly and being replaced by the process described prior

Stratum Lucidum

a layer of the epidermis found only in the thick skin of the fingers, palms, and soles

What is the composition of the Stratum Lucidum?

Composed of a few layers of dead, flattened, translucent keratinocytes

Stratum Granulosum

3rd layer of the skin

What process occurs as cells move through the Stratum Granulosum?

Keratin replaces their nuclei and organelles, leading to cell apoptosis (death)

Stratum Spinosum

A layer of the epidermis that provides strength and flexibility to the skin

What is another name for the Stratum Spinosum?

Prickle cell

What happens in the Stratum Spinosum?

Keratinocytes begin to actively synthesize keratin which builds up in the cells giving them a "prickly" appearance

What is another name for the Stratum Basale?

Stratum Germinativum

How thick is the Stratum Basale?

Only 1 cell thick

What happens if the Stratum Basale is destroyed?

New skin cannot regenerate

What type of cells are mostly found in the Stratum Basale?

Keratinocyte stem cells

Papillary Layer

outer, thin layer of the dermis, directly beneath the epidermis and rich in blood vessels

Reticular Layer

Deeper & thicker layer of the dermis that supplies the skin with oxygen and nutrients

Striae

stretch marks; stretching of dermal collagen

Eumelanin

brownish black pigment

Pheomelanin

reddish-yellow pigment

Hemaglobin

Oxygen carrying pigment in red blood cells (red)

Carotene

yellow-orange pigment (carots) that concentrate in stratum corneum

Cyanosis

bluish discoloration of the skin; caused by lack of oxygen

Erythema

redness; caused by increase blood flow

Pallor

paleness; caused by lack of blood flow

Albinism

Absence of pigment in the skin, hair, and eyes; caused by genetics/heredity

Jaundice

yellowing of the skin; caused by liver failure

Hematoma

bruise; multiple colors

Friction rides of fingertips

Aid in sensitivity to texture and ability to grasp
Cause fingerprint pattern

Flexion lines (creases)

where skin near joint attaches to deeper tissue

Freckles

flat, melanized patches; vary with heredity & UV exposure

Mole (nevus)

Elevated patch of melanized skin

Hair Follicle

A sac within which each hair grows

What are the two layers of a hair follicle?

Epithelial root sheath (inner layer) and Connective tissue root sheath (derived from dermis)

Downy Hair

fine, unpigmented hair on fetus

Vellus Hair

Fine & Unpigmented, all hair in children
→ ⅔ of women's hair
→ 1/10 of men's hair

Bulb

→ Swelling at base where hair originates in dermis
→ Dermal papilla - provides nutrition
→ Hair matrix - hair's growth center (mitosis)

dermal papilla

A small, cone-shaped area at the base of the hair follicle that fits into the hair bulb

Root

Remainder of hair within follicle, dead tissue

Shaft

visible part of the hair; dead tissue

Medulla

internal layer of hair, loosely arranged cells & air spaces

Cortex

bulk of hair, several layers of long cells

Cuticle

→ Outer layer
→ Overlapping scaly cells

Hair receptors

sensory nerve fibers entwining follicles

Arrector muscle (arrector pili)

smooth muscle that causes goose bumps

Why do we have nails instead of claws?

We have flat nails, as opposed to claws, for easier manipulation.

Nail Plate

Hard part of nail. Includes free edge, nail body, nail root.

Nail fold

Fold of normal skin that surrounds the nail plate; nail groove

Nail bed

skin underlying the nail plate

Hyponychium

Skin between the free edge and fingertip of the natural nail

Lunule

an opaque white crescent at proximal end of nail

Eponichium

cuticle of nail

Cutaneous Glands

sebaceous glands and sweat glands

Where are eccrine (merocrine) glands especially abundant?

On palms, soles, and forehead

What do simple ducts of eccrine glands lead to?

Pores at the skin surface of the epidermis

What is the main function of eccrine glands?

To produce water and salty perspiration to cool the body

Eccrine (merocrine) glands

glands that produce sweat; found over most of the body

Apocrine glands

Sweat glands in the pubic and underarm areas that secrete thicker sweat

Where are apocrine glands found?

Groin, anal region, axilla, areola, and beard

What do apocrine glands produce?

Sweat with many fat molecules

What causes the odor associated with apocrine gland sweat?

Bacterial metabolism of fats

How do apocrine glands respond?

To stress and sexual stimulation

When do apocrine glands develop?

During puberty (not active until puberty)

What is the believed function of apocrine glands?

To secrete pheromones

Sebaceous glands

secrete sebum (oil) into the hair follicles where the hair shafts pass through the dermis

What is the main function of sebaceous glands?

Produce oily secretion called sebum

Where do sebaceous glands usually open into?

Hair follicle

How do sebaceous glands help in maintaining skin and hair health?

They keep skin and hair from becoming brittle

Sebum

oily substance secreted by sebaceous glands

Ceruminous Glands

produce ear wax (cerumen)

Cerumen

ear wax