Integumentary System and Tissue Membranes Review

Flashcards covering tissue membranes, tissue repair, skin anatomy and strata, integumentary functions, skin pigmentation, hair, nails, cutaneous glands, and skin pathologies.

True membranes

Membranes that line closed body cavities (such as the peritoneum, pleura, pericardium, and dura mater), remain continuous with the body surface, and do not open to the external environment.

Membrane-like structures

Structures continuous with the body surface that have a free opening to the external environment, such as the conjunctiva, respiratory mucosa, and anal mucosa.

Serous membranes

True membranes consisting of a mesothelium, basement membrane, and connective tissue layer that line the pericardial, peritoneal, and pleural body cavities.

Mesothelium

The thin simple squamous epithelium layer of serous membranes whose cells produce serous fluid to reduce friction from moving organs.

Parietal layer

The outer layer of a serous membrane that is in contact with the body wall.

Visceral layer

The inner layer of a serous membrane that directly covers organs within a body cavity.

Synovial membranes

Connective tissue membranes lining cavities around freely moveable joints, composed of two connective tissue layers with no epithelial cell layer.

Synoviocytes

Specialized connective tissue cells in the intima layer of synovial membranes that secretes synovial fluid to lubricate joints.

Mucous membranes

Membrane-like structures lining internal body surfaces and hollow organs that open to the exterior, composed of an epithelial layer, lamina propria, and mucus-secreting goblet cells.

Lamina propria

The connective tissue layer and basement membrane that supports the epithelium in mucous membranes.

Regeneration

A tissue repair process in which dead and damaged cells are replaced with cells of the same type, completely restoring original structure and function without scar tissue.

Fibrosis

A tissue repair process in which fibroblasts fill injury gaps with scar tissue composed of dense irregular connective tissue, leading to a loss of tissue function.

Cutaneous membrane

The skin; composed of an outer epidermis (keratinized stratified squamous epithelium) resting on a basement membrane and a deeper dermis (loose and dense irregular connective tissue).

Epidermis

The most superficial, avascular layer of the skin that relies on diffusion of oxygen and nutrients from blood vessels in the underlying dermis.

Dermis

The highly vascular layer deep to the epidermis that provides blood supply, contains sensory receptors, and anchors the epidermis in place.

Hypodermis

The subcutaneous layer deep to the dermis made of loose connective tissue and adipose tissue that anchors skin to muscle and bone; also known as superficial fascia.

Keratinocytes

The most abundant cell type in the epidermis (about $95\%$), linked by desmosomes and responsible for manufacturing the tough fibrous protein keratin.

Keratin

A tough fibrous protein produced by keratinocytes that makes the epidermis resistant to mechanical trauma.

Stratum basale

The deepest epidermal layer consisting of a single layer of stem cells on the basement membrane that are mitotically active and involved in vitamin D synthesis.

Stratum spinosum

The thickest layer of the epidermis, located superior to the stratum basale; contains mitotically active cells that appear spiky on slides due to connecting desmosomes.

Stratum granulosum

An epidermal stratum containing cells with cytoplasmic granules filled with keratin bundles or lipid-based substances that exocytose to provide hydrophobic waterproofing.

Stratum lucidum

A narrow layer of clear, dead keratinocytes found only in thick skin.

Stratum corneum

The outermost layer of the epidermis consisting of multiple layers of dead, flattened keratinocytes filled with keratin bundles that shed as desmosomes break down.

Dendritic (Langerhans) cells

Phagocytic cells located in the stratum spinosum that protect the skin and deeper tissues from pathogens.

Melanocytes

Cells in the stratum basale that synthesize melanin pigment in melanosomes and transfer it to neighboring keratinocytes.

Merkel cells

Sensory cells scattered throughout the stratum basale that detect light touch and discriminate shapes and textures in specialized regions like fingertips and lips.

Papillary layer

The thin, superficial dermal layer composed of loose (areolar) connective tissue that forms dermal papillae and anchors the epidermis.

Dermal papillae

Tiny projections at the surface of the papillary dermis containing capillary loops that supply oxygen and nutrients to the avascular epidermis.

Reticular layer

The deep, thicker layer of the dermis composed of dense irregular connective tissue containing collagen bundles, elastic fibers, proteoglycans, blood vessels, and glands.

Tyrosinase

An enzyme inside melanosomes that catalyzes the joining of two tyrosine amino acids to synthesize melanin.

Albinism

A condition in which melanocytes fail to produce the tyrosinase enzyme, resulting in an inability to synthesize melanin.

Vitiligo

An autoimmune disorder in which the immune system targets and destroys scattered melanocytes, leading to patchy depigmentation.

Freckle

A small area of increased pigmentation caused by a localized increase in melanin production concentrated in one spot.

Mole (nevus)

An area of increased skin pigmentation caused by a localized proliferation of melanocytes.

Carotene

A yellow-orange, lipid-soluble food pigment that accumulates in the stratum corneum.

Hemoglobin

An iron-containing oxygen-transport protein in red blood cells that turns bright orange-red when bound to oxygen, influencing skin color via dermal blood flow.

Hair shaft

The portion of hair projecting above the skin surface, composed of columns of dead keratinized epithelial cells.

Hair root

The segment of hair embedded in the dermis, surrounded by sensory neurons and the epithelial root sheath.

Hair papilla

A projection of dermal blood vessels indenting the base of the hair root to supply nutrients.

Hair bulb

The collective structure at the base of a hair formed by the hair root and the hair papilla.

Matrix (hair)

A small group of keratinocytes at the base of the hair root that actively divide by mitosis to produce hair growth.

Arrector pili muscles

Bands of smooth muscle attaching the dermal root sheath to the papillary dermis that contract to pull hair upright, producing goosebumps.

Lanugo

Thin, nonpigmented downy hair covering the body of a fetus, typically shed around birth.

Terminal hair

Thick, coarse, pigmented hair found on the scalp, around the eyes, and emerging on body regions after puberty.

Vellus hair

Thinner, fine, nonpigmented hair covering most body surfaces prior to puberty.

Nail plate

The visible hard portion of the nail resting on top of the underlying epidermal nail bed.

Nail matrix

The actively dividing region of cells at the proximal nail root that produces new nail cells.

Lunula

A translucent, half-moon shaped region at the proximal nail plate that represents an accumulation of keratin.

Sebaceous glands

Exocrine glands found everywhere except palms and soles that produce oily sebum via holocrine secretion into hair follicles or pores.

Sebum

A waxy, oily mixture of lipids and cellular debris that coats hair and skin to prevent water loss and inhibit bacterial growth.

Holocrine secretion

A secretory mechanism in sebaceous glands where product accumulates inside secretory cells until the entire cell ruptures and dies.

Merocrine secretion

A secretory process where gland cells release products via exocytosis without cellular destruction, utilized by sweat glands.

Eccrine sweat glands

Prevalent simple coiled tubular dermal glands that use merocrine secretion to release a water- and electrolyte-rich sweat onto the epidermis for thermoregulation.

Apocrine sweat glands

Large glands in the axillae, anal area, and areolae that release a protein-rich secretion into hair follicles that becomes odiferous upon bacterial metabolism.

Ceruminous glands

Modified apocrine glands in the ear canal that produce cerumen (ear wax) to lubricate and protect the tympanic membrane.

First-degree burn

A minor superficial burn affecting only the epidermis, causing skin redness and mild pain without permanent damage.

Second-degree burn

A partial-thickness burn involving the epidermis and part or all of the dermis, resulting in pain, blistering, and scarring.

Third-degree burn

A full-thickness burn damaging the epidermis, dermis, hypodermis, and potentially deeper tissues like muscle or bone.

Basal cell carcinoma

The most common skin cancer, arising from keratinocytes in the stratum basale and forming a nodule with a central cratered center.

Squamous cell carcinoma

The second most common skin cancer, arising from keratinocytes in the stratum spinosum and forming scaly plaques that may ulcerate.

Malignant melanoma

A highly metastatic cancer of melanocytes evaluated using the ABCDE diagnostic rule.

ABCDE rule

A diagnostic mnemonic for melanoma: Asymmetrical shape, Border irregularity, Color variation (blue-black), Diameter larger than $6\,mm$, and Evolving shape and size.