Integumentary System

A set of vocabulary-style flashcards covering key terms from the integumentary and skeletal system lectures.

Integumentary system

The organ system comprising the skin and its derivatives that protect the body, regulate temperature, sense stimuli, and synthesize vitamin D.

Keratin

A fibrous protein that fills keratinocytes and gives strength to the epidermis, hair, and nails.

Sebaceous glands

Oil secreting glands connected to hair follicles; stratified cuboidal epithelium; produce sebum to lubricate hair/skin, condition hair, and provide antibacterial protection.

Epidermis

The outermost layer of skin composed of keratinized stratified squamous epithelium.

Water resistant barrier

The lipid-rich stratum corneum that helps prevent water loss from the body.

Melanin

Brown pigment produced by melanocytes in the epidermis that blocks UV radiation.

UV radiation

Ultraviolet light from the sun that can damage DNA and increase skin cancer risk.

Photochemical synthesis

UVB-driven production of vitamin D (cholecalciferol) in the epidermis.

Cholecalciferol (vitamin D3)

The vitamin D synthesized in the skin; fat-soluble and important for calcium absorption.

Epidermal layers

Five distinct layers of the epidermis: basale, spinosum, granulosum, lucidum (only thick skin), corneum.

Dermis

Layer beneath the epidermis containing connective tissue, blood vessels, nerves; subdivided into papillary and reticular layers.

Hypodermis

Deepest skin layer composed of adipose tissue that insulates and stores energy.

Dermal papillae

Upward projections of the dermis that contain capillaries and nerves; contribute to fingerprints. Supply nutrients to epidermal cells and remove waste.

Stratum basale (germinativum)

Deepest epidermal layer with stem cells that divide to form keratinocytes (also contains melanocytes and tactile cells).

Stratum spinosum

Layer above basale; keratinocytes with a spiny appearance; contains Langerhans cells; Defend against infection.

Stratum granulosum

Granular layer where keratinocytes accumulate keratin and lipids, contributing to the water barrier. Cells begin to flatten and prepare for apoptosis.

Stratum lucidum

Clear layer found only in thick skin (palms/heels); appears translucent and is not stained.

Stratum corneum

Most superficial; dead keratinocytes filled with keratin; surrounded by glycolipids to maintain water resistance; continually shed and replaced by cells from deeper layers; turnover about two weeks.

Melanocytes

Pigment-producing cells in the epidermis that transfer melanin to keratinocytes.

Melanosomes

Melanin-containing vesicles within melanocytes and keratinocytes. Form a thicker melanin layer with darker skin.

Langerhans cells

Antigen-presenting leukocytes in the stratum spinosum that defend against infection by recognizing pathogens; monitor for abnormal cells and can trigger removal of cancerous or malfunctioning cells.

Merkel cells

Tactile discs in stratum basale; somatosensory receptors for light touch.

Meissner's corpuscles

Tactile corpuscles in the dermal papillae that detect light touch.

Pacinian corpuscles

Lamellar corpuscles; receptors for deep pressure and high-frequency vibration.

Tactile discs

Merkel cell receptors that detect light touch and skin movement.

Sebaceous glands

Glands that secrete sebum to lubricate hair/skin and provide antibacterial protection.

Sebum

Oily secretion that lubricates hair/skin and helps prevent infection.

Eccrine sweat glands

Widespread glands that produce watery sweat for thermoregulation; ducts open to skin surface.

Apocrine sweat glands

Glands in axillary, groin, and other areas; produce lipid- and protein-rich secretion associated with odor.

Hair follicle

Invagination of epidermis into the dermis from which hair grows; contains hair matrix at the base.

Hair matrix

Layer of mitotically active cells in the hair bulb that forms hair.

Hair (pili)

Hair is primarily keratin and consists of dead keratinized cells; originates from hair follicles.

Hair bulb

Enlarged base of the hair follicle where hair production occurs.

Hair papilla

Connective tissue core of the hair bulb containing blood vessels nourishing hair growth.

Erector pili

Smooth muscle attached to hair follicle; makes hair stand up (goosebumps).

Nails

Hard keratinized plates on fingers and toes formed from the nail matrix.

Nail matrix

Tissue at the base of the nail where nail growth occurs.

Nail plate (body)

Visible, pink due to dermal blood vessels.

Nail root

Portion under proximal skin fold

Cuticle (eponychium)

Proximal nail fold that overlaps the nail body; protective skin cover.

Basal cell carcinoma

Most common skin cancer arising from basal cells; rarely metastasizes.

Squamous cell carcinoma

Skin cancer from keratinocytes in the stratum spinosum; may metastasize.

Melanoma

Malignant tumor of melanocytes; highly metastatic and potentially fatal.

p53

Tumor suppressor gene; promotes DNA repair and apoptosis; commonly mutated in skin cancers.

Oncogenes

Mutated genes that speed up cell division and promote cancer progression.

Proto-oncogenes

Normal genes that regulate cell growth; can become oncogenes when mutated.

RAF-MEK-ERK pathway

MAPK signaling cascade that promotes cell division; often dysregulated in cancer.

EGFR

Epidermal Growth Factor Receptor; receptor tyrosine kinase activating MAPK pathway.

Oncogenesis

The transformation of normal cells into cancerous cells due to mutations that disrupt tissue growth and apoptosis

Benign tumors

Noncancerous masses that do not invade or metastasize (e.g., skin tags, lipomas, nevi).

Malignant tumors

Cancerous tumors that invade tissues and can metastasize to distant sites.

ABCDE

Asymmetry, Border irregularity, Color variation, Diameter >6 mm, Evolution—melanoma warning signs.

Parathyroid hormone (PTH)

Hormone that raises blood calcium by increasing osteoclast activity, renal calcium reabsorption, and vitamin D activation.

Calcitonin

Thyroid hormone that lowers blood calcium by inhibiting osteoclasts and promoting calcium storage in bone.

Vitamin D activation

Process of converting vitamin D to its active form via hydroxylation in liver and kidney (final step in kidney).

Red bone marrow

Site of hematopoiesis in adults; contains hematopoietic stem cells; found in proximal long bones, ribs, sternum, ileum crest, and vertebrae.

Yellow bone marrow

Adipose tissue that replaces red marrow with age; stores fat.

Hematopoiesis

Production of blood cells in red bone marrow.

Osteoclasts

Bone-resorbing cells that break down bone matrix to release calcium.

Osteoblasts

Bone-forming cells that lay down new bone.

Hydroxyapatite

Mineral component of bone; calcium phosphate that gives bone its hardness.

206 bones

The typical total number of bones in an adult human skeleton.

Axial skeleton

Skull, vertebral column, and thoracic cage; central axis of the skeleton.

Appendicular skeleton

Bones of the limbs and girdles that attach to the axial skeleton.

Jaundice

Yellowing of skin and eyes due to elevated bilirubin levels.

Bilirubin

Breakdown product of heme; excreted by the liver; elevated levels cause jaundice.

Cyanosis

Bluish discoloration of the skin due to low blood oxygen.

Petechiae

Small red-purple spots from minor bleeding under the skin.

Purpura

Larger areas of purplish discoloration due to bleeding under the skin.

Sunburn

Skin damage from excessive UV exposure; inflammation and potential long-term effects.

Tan

Increased skin pigmentation due to melanin production in response to UV exposure.

Carotene

Orange pigment from diet; precursor to vitamin A; excess can color skin (keratosis in some cases).

Keratosis

Orange skin coloration from excessive carotene intake; seen in some individuals.

Melanocytic nevus

Benign melanocyte proliferation (mole) that can become melanoma if changes occur.

Hypodermis

Adipose tissue, deepest layer of dermis

Keratinocytes

Primary cell type in epidermis; synthesize keratin, on intermediate filament protein, to provide epidermal strength

Freckles / moles

Local increase in melanin

Heme

Red pigment in erythrocytes; blood flow affects skin color

Oxygenated hemoglobin

Bright red

Deoxygenated hemoglobin

Darker red