Anatomy and Physiology Exam Preparation: Homeostasis, Tissues, Integumentary System, and Bone Biology

Vocabulary practice flashcards covering core human anatomy and physiology concepts including homeostasis, membrane transport, tissues, skin structures, epidermal layers, hair growth cycles, bone ossification, and bone disorders.

Negative feedback loop

A primary homeostatic mechanism that maintains a physiological variable close to its set point by opposing any changes away from it.

Dynamic equilibrium

A state in which the internal conditions of the body fluctuate within a limited, healthy range around a specific set point.

Positive feedback loop

A self-amplifying system in which a stimulus produces a response that further intensifies that change, continuing the feedback loop.

Ectoderm

The outer primary germ layer that gives rise to the epidermis, brain cells, and nervous tissue.

Mesoderm

The middle primary germ layer that develops into mesenchyme, which forms the dermis, mesothelium, blood, muscle, and all connective tissues.

Endoderm

The innermost primary germ layer that forms the epithelial lining of hollow organs, the gastrointestinal tract, and the respiratory tract.

Pinocytosis

A form of endocytosis often termed 'cell drinking', in which the cell engulfs droplets of extracellular fluid.

Phagocytosis

A form of endocytosis known as 'cell eating', in which the cell engulfs large particles or whole microorganisms.

Exocytosis

The cellular process by which vesicular contents are discharged to the outside of the cell.

Serous membrane

A body membrane lining internal cavity surfaces, consisting of simple squamous epithelium (mesothelium) over a thin layer of areolar connective tissue.

Cutaneous membrane

The protective outer skin membrane, composed superficially of keratinized stratified squamous epithelium and deeply of areolar connective tissue.

Mucous membrane

A membrane lining surfaces of hollow organs open to the exterior, composed of epithelium, lamina propria (areolar tissue), and a deep layer of smooth muscle.

Tight junctions

Occluding intercellular junctions that seal off intercellular space and prevent fluids and solutes from passing between adjacent epithelial cells.

Desmosomes

Anchoring intercellular junctions that act like velcro to mechanically hold adjacent cells together and resist mechanical stress.

Hemidesmosomes

Specialized cell junctions that latch the basal surface of epithelial cells to the underlying basal lamina.

Gap junctions

Communicating intercellular junctions made of channel pores that allow ions and small molecules to move directly between cells to equilibrate internal conditions.

Exocrine glands

Glands that secrete their chemical products through ducts onto internal or external body surfaces.

Endocrine glands

Ductless glands that release hormones directly into extracellular fluid and the bloodstream rather than onto body surfaces.

Merocrine secretion

A mode of exocrine secretion (also known as eccrine) where product is released intact via vesicular exocytosis.

Holocrine secretion

A mode of exocrine secretion in which the entire secretory cell disintegrates to release its accumulated product ('suicide secretion').

Apocrine secretion

A mode of exocrine secretion in which the apical surface fragment of the cell detaches to release exocrine product into a duct ('decapitation secretion').

Keratinocytes

The predominant cell type in the epidermis, responsible for synthesizing the protective protein keratin.

Melanocytes

Cells located in the stratum basale of the epidermis that synthesize melanin and transfer melanosomes to surrounding keratinocytes.

Tactile disc

A sensory complex consisting of a tactile cell in the stratum basale paired with an underlying dermal nerve fiber for detecting touch.

Dendritic cells

Immune cells located in the stratum spinosum and stratum granulosum that guard against foreign toxins and pathogens and alert the immune system.

Stratum basale

The deepest layer of the epidermis, comprising a single row of cuboidal or low columnar keratinocytes, stem cells, melanocytes, and tactile cells.

Stratum spinosum

The thickest layer of non-thick-skin epidermis, consisting of several layers of keratinocytes connected by desmosomes and tight junctions.

Stratum granulosum

An epidermal layer consisting of 3 to 5 layers of flattened keratinocytes containing dark keratohyalin granules and lipid-releasing lamellar granules.

Stratum lucidum

A thin, translucent layer of clear, dead keratinocytes filled with eleidin, found exclusively in thick skin.

Stratum corneum

The outermost layer of the epidermis, comprising up to 30 layers of dead, flattened, keratinized cells that form a durable barrier.

Dermis

The connective tissue layer directly deep to the epidermis, composed mostly of collagen, rich in blood vessels, nerves, glands, and hair roots.

Dermal papillae

Fingerlike upward extensions of the dermis that interlock with epidermal ridges to prevent slipping between the skin layers.

Hypodermis

The subcutaneous layer deep to the dermis composed primarily of areolar and adipose tissue, serving to pad the body and anchor the skin.

Cyanosis

A bluish or grayish discoloration of the skin resulting from a lack of oxygen in the blood.

Erythema

Abnormal skin redness produced by increased blood flow through dilated cutaneous blood vessels.

Pallor

A pale skin tone occurring when diminished dermal blood flow allows the light color of dermal collagen to show through.

Albinism

A hereditary lack of skin pigmentation caused by a recessive, non-functional tyrosinase allele, resulting in no melanin production.

Jaundice

An abnormal yellowing of the skin and eyes caused by high levels of bilirubin in the bloodstream.

Hematoma

A localized mass of clotted blood (bruise) visible through the skin, typically caused by physical trauma.

Anagen

The active growth phase of the hair cycle, encompassing approximately $90\%$ of scalp hair at any given time.

Catagen

The transition phase of the hair cycle lasting 2 to 3 weeks, where mitosis ceases and the hair follicle shrinks to form a club hair.

Telogen

The resting phase of the hair cycle lasting 1 to 3 months before a new cycle initiates.

Interstitial growth

The process of bone elongation during young life, occurring through cartilage multiplication and replacement at the epiphyseal plate.

Appositional growth

The process of bone thickening and widening throughout life, occurring by the deposition of new bone tissue at the bone surface.

Intramembranous ossification

Bone formation directly within embryonic fibrous connective tissue (mesenchyme) without a prior cartilage model, producing flat skull bones.

Endochondral ossification

Bone formation process in which a precursor hyaline cartilage model is gradually replaced by bone tissue.

Wolff's law

The principle stating that bone architecture remodels in direct response to the mechanical stresses placed upon it.

Osteitis deformans (Paget disease)

A disease marked by excessive osteoclast proliferation and bone resorption, accompanied by compensatory rapid and disorganized osteoblast bone deposition.

Osteomyelitis

An inflammation of bone tissue and bone marrow resulting from a bacterial infection.

Osteogenesis imperfecta

A genetic collagen disorder rendering bones exceptionally brittle, leading to frequent fractures, tooth deformity, and middle-ear hearing loss.

Osteosarcoma

The most prevalent and lethal form of bone cancer, occurring primarily in the tibia, femur, and humerus of males aged 10 to 25.

Scoliosis

An abnormal lateral postural curvature of the spine to either the left or right side.

Hyperkyphosis

An abnormal anterior postural drift or exaggerated thoracic curvature of the spine ('hunchback').

Hyperlordosis

An abnormal posterior postural drift or exaggerated lumbar curvature of the spine ('swayback').