Module 2: Integumentary System

Integumentum

A covering

Integument

Natural covering of an organism or an organ, such as its skin, husk, shell, or rind.

Skin

The largest organ of the human body.

20 square feet

Measurement of the skin.

Epidermis, Dermis, Hypodermis

Parts of the skin.

Epidermis

A stratified epithelium with cells that flatten as they mature and rise to the surface.

Stratum Basale

Innermost layer of the epidermis, and contains small round cells called basal cells

Stratum Germinativum

The basal cell layer is also known as this due to the fact that it is constantly germinating (producing) new cells.

Melanocytes

Produce the skin coloring or pigment known as melanin.

Melanin

Gives skin its tan or brown color and helps protect the deeper layers of the skin from the harmful effects of the sun.

Melanoma

Develops when melanocytes undergo malignant transformation.

Merkel Cells

Tactile cells of neuroectodermal origin, are also located in the basal layer of the epidermis. They function as touch receptors.

Stratum Spinosum

Spiny layer, thickest layer, due to the fact that the cells are held together with spiny projections.

Keratinocytes

Produce keratin, a tough, protective protein that makes up the majority of the structure of the skin, hair, and nails.

Langerhans cells

Cells in the stratum spinosum, attach themselves to antigens that invade damaged skin and alert the immune system to their presence.

Stratum granulosum and Stratum lucidum

The keratinocytes from the squamous layer are then pushed up through two thin epidermal layers.

Stratum corneum

The outermost layer of the epidermis, also known as the "horny layer," because its cells are toughened like an animal's horn.

10 to 30 thin layers

How many dead keratinocytes on the stratum corneum.

Dermis

A connective tissue layer, composed mainly of collagen, but also contains elastic and reticular fibers, fibroblasts, and the other cells typical of fibrous connective tissue.

Papillary layer

Supplies nutrients to select layers of the epidermis and regulates temperature.

Constriction and expansion

Control the amount of blood that flows through the skin and dictate whether body heat is dispelled when the skin is hot or conserved when it is cold.

Reticular layer

Thicker and made of thick collagen fibers that are arranged in parallel to the surface of the skin.

Subcutis

The innermost layer of the skin, and consists of a network of fat and collagen cells

Hypodermis

Functions as both an insulator, conserving the body's heat, and as a shock-absorber, protecting the inner organs.

Drugs

Introduced into the hypodermis by injection because the subcutaneous tissue is highly vascular and absorbs them quickly.

Hair and nails

Composed mostly of dead, hard keratinized cells.

Hard keratin

More compact than soft keratin and is toughened by numerous cross-linkages between the keratin molecules.

Hair

A slender filament of keratinized cells that grows from an oblique tube in the skin called a hair follicle.

Pilus, Pili

Other term for hair (singular and plural).

Hair follicle

A tube-like structure (pore) that surrounds the root and strand of a hair.

Lower, Middle, Upper Segment

Three regions of the hair folicle.

Lower segment

Extends from the base of the follicle to the insertion of the erector pili muscle (also known as the arrector pili muscle).

Middle segment

A short section that extends from the insertion of the erector pili muscle to the entrance of the sebaceous gland duct.

Upper segment

Extends from the entrance of the sebaceous gland duct to the follicular orifice.

Angiogenesis

Form new blood vessels.

Neurogenesis

Form new nervous system neuron cells.

Folliculitis

Common skin condition that happens when hair follicles become inflamed.

Alopecia areata

A disease that happens when the immune system attacks hair follicles and causes hair loss.

Telogen effluvium

Common type of hair loss that affects people after they experience severe stress or a change to their body.

Hidradenitis suppurativa

A condition that causes small, painful lumps to form under the skin.

Nail unit

Complex structure located on the dorsal surface of the fingers and toes.

Nails

Homologous to the stratum corneum of the epidermis and contain a variety of minerals, such as calcium.

Protection

Protects the digits from trauma.

Sensation

Assists with tactile sensation.

Nail plate

Outer portion of the nail unit, formed by layers of keratin. It forms a hard, yet flexible, translucent plate.

Nail folds

Skin that surrounds and protects the proximal and lateral margins of the nail plate.

Nail bed

Lies underneath the nail plate, attaching it to the distal phalanx.

Germinal matrix

Area of soft tissue proximal to the sterile matrix.

Hyponychium

The area distal to the nail bed, situated underneath the free edge of the nail plate.

Eponychium (Cuticle)

Layer of stratum corneum which extends between the skin of the finger and proximal nail plate.

Lunula

White ‘half-moon’ appearance of the germinal matrix through the proximal nail plate.

Ingrown toenail

Incurvation or impingement of a nail border into its adjacent nail fold, causing pain.

Onychomycosis

Fungal infection of the nails that causes discoloration, thickening, and separation from the nail bed.

Apocrine glands

Specialized sweat glands that can be found only in the armpits and pubic region.

Eccrine glands

The true sweat glands. Found over the entire body, these glands regulate body temperature by bringing water via the pores to the surface of the skin.

3 million

Number of sweat glands in the body.

Impacted cerumen

Obstruction of the external auditory canal by earwax, causing symptoms.

Mammary glands

The milk-producing glands that develop within the female breast only during pregnancy and lactation.

Breast (Mammae)

They rarely contain more than small traces of mammary gland.

Sebaceous gland

Exocrine glands found in the skin. They are classified as holocrine glands, meaning their secretions are released through the rupture and destruction of whole gland cells.

Hair shaft

The visible part of the hair that extends above the skin surface.

Sebaceous duct

Connects the sebaceous gland to the hair follicle, allowing sebum to flow into the follicular canal.

Arrector pili muscle

Small smooth muscle that contracts in response to cold or emotional stimuli (e.g., "goosebumps"); helps expel sebum from the gland.

Sebum

An oily, lipid-rich substance that sebaceous gland secretes.

Holocrine

The entire cell fills with sebum and then disintegrates, releasing its contents.

Hormones

Sebaceous gland activity is regulated primarily by these, especially androgens

Estrogen

May suppress sebaceous activity.

Acne vulgaris

Chronic inflammatory disorder of the pilosebaceous unit.

Cutibacterium acnes proliferation

Refers to the overgrowth of a normal skin bacterium that plays a key role in the development of acne vulgaris.