Human Anatomy and Physiology: Foundations, Cytology, Histology, and Systems

Comprehensive vocabulary flashcards covering chemical foundations, cellular structures and transport, neural electrophysiology, tissue classifications, and the integumentary system.

Anatomy

The study of human structure and form.

Physiology

The study of biological function in the human body.

Palpation

The clinical technique of feeling a structure with the hands, such as taking a pulse or palpating landmarks.

Auscultation

The act of listening to the natural sounds made by the body, such as heart and lung sounds.

Percussion

Tapping on the body surface to feel the resistance and listen to the emitted sound for signs of abnormalities.

Histology

Microscopic anatomy; the examination of tissues under a microscope.

Cytology

The study of the structure and function of individual cells.

Homeostasis

The ability to detect change, activate mechanisms that oppose it, and maintain relatively stable internal conditions around a set point.

Negative Feedback

A primary homeostatic mechanism in which the effector response negates or reverses the stimulus to restore balance.

Positive Feedback

A self-amplifying cycle in which a physiological change leads to greater change in the same direction, seen in childbirth and blood clotting.

Positron Emission Tomography (PET Scan)

A functional imaging modality that assesses the metabolic activity of tissues by injecting radioactively labeled glucose and detecting gamma rays produced by positron-electron collisions.

Magnetic Resonance Imaging (MRI)

A high-quality soft-tissue imaging method that utilizes a magnetic field and radio waves to align and realign hydrogen atoms.

Subatomic Particles

The fundamental components of an atom: protons ($+1$ charge, $1$ mass unit), neutrons (neutral, $1$ mass unit), and electrons ($-1$ charge, negligible mass).

Isotope

A specific version of an element that differs in mass number due to a different number of neutrons while retaining the same number of protons.

Ionic Bond

A chemical attraction between an electron donor that loses electrons to become a cation ($+$) and an electron acceptor that gains electrons to become an anion ($-$).

Polar Covalent Bond

A covalent bond formed by the unequal sharing of electrons between atoms due to disproportionate electronegative pull, producing polar molecules like water.

Hydrogen Bond

A weak polar attraction between slightly positive and slightly negative regions of adjacent polar molecules, responsible for water's surface tension.

Cohesion

The intermolecular attraction that holds molecules of water together.

Adhesion

The attraction of water molecules to the molecules of a surrounding container or tube.

Buffer

A weak acid/salt compound that stabilizes pH by neutralizing strong acids or strong bases, exemplified by sodium bicarbonate ($\text{NaHCO}_3$).

Dehydration Synthesis

An enzymatic chemical reaction that joins monomers into polymers by releasing a water molecule ($\text{H}_2\text{O}$).

Hydrolysis

A chemical reaction that breaks polymers down into individual monomers through the addition of a water molecule ($\text{H}_2\text{O}$).

Glycogen

A branched energy-storage polysaccharide synthesized and stored in the skeletal muscle and liver tissue of humans.

Cellulose

A rigid structural polysaccharide found in plant cell walls that cannot be digested by humans.

Triglyceride

A neutral fat molecule composed of one glycerol molecule linked to three fatty acid chains, functioning as thermal insulation and an energy reserve.

Phospholipid

An amphipathic lipid consisting of a hydrophilic phosphate head and two hydrophobic fatty acid tails, forming cellular membranes.

Amino Acid

A monomer of proteins comprising a central carbon, an amino group, a carboxyl group, a hydrogen atom, and a variable R-group.

Denaturation

A conformational change that permanently alters a protein's three-dimensional shape, causing it to lose its biological function.

Activation Energy

The minimum energy barrier required to initiate a chemical reaction, which enzymes lower to accelerate reaction rates.

Glycocalyx

A fuzzy, carbohydrate-rich surface coating composed of glycolipids and glycoproteins that acts as an identification marker for cell recognition.

Microvilli

Short membrane extensions containing actin microfilaments that increase the absorptive surface area of a cell by $15$ to $40$ times.

Cilia

Hairlike motile processes that beat in coordinated power and recovery strokes to propel fluids and mucus across a cell surface.

Simple Diffusion

The passive net movement of solute particles down their concentration gradient from a region of higher concentration to lower concentration without ATP expenditure.

Osmosis

The net diffusion of water across a selectively permeable membrane toward the side with a higher concentration of nonpermeating solutes.

Hypotonic Solution

A solution with a lower concentration of nonpermeating solutes than intracellular fluid ($\text{ICF}$), causing cells to absorb water and swell.

Hypertonic Solution

A solution with a higher concentration of nonpermeating solutes than intracellular fluid ($\text{ICF}$), causing cells to lose water and crenate.

Sodium-Potassium ($\text{Na}^+-\text{K}^+$) Pump

A primary active transport antiport carrier that hydrolyzes $1\,\text{ATP}$ to pump $3\,\text{Na}^+$ out and $2\,\text{K}^+$ into the cell.

Secondary Active Transport

Carrier-mediated transport where a solute moves against its gradient by coupling to an ion moving down its gradient, indirectly powered by ATP, such as the sodium-glucose transporter ($\text{SGLT}$).

Phagocytosis

A form of endocytosis ('cell eating') in which pseudopods reach out to engulf large particles into a phagosome for lysosomal degradation.

Receptor-Mediated Endocytosis

A selective uptake process where extracellular ligands bind to cell-surface receptors and concentrate in clathrin-coated pits before vesicle internalization.

Rough Endoplasmic Reticulum

Flattened membranous cisternae studded with ribosomes that synthesize proteins destined for secretions, lysosomes, or the plasma membrane.

Smooth Endoplasmic Reticulum

Tubular membranous cisternae devoid of ribosomes that synthesize lipids and steroids, detoxify drugs and alcohol, and store intracellular calcium.

Golgi Complex

A stack of cisternae that receives newly synthesized proteins from the rough ER, chemically modifies and sorts them, and packages them into vesicles.

Lysosome

A membrane-bound organelle containing hydrolytic digestive enzymes that carries out intracellular digestion, autophagy, and autolysis.

Peroxisome

An organelle that utilizes molecular oxygen to oxidize organic molecules, generating hydrogen peroxide ($\text{H}_2\text{O}_2$) that catalase breaks down into $\text{H}_2\text{O}$ and $\text{O}_2$.

Mitochondria

Double-membraned 'powerhouse' organelles with folded inner cristae that synthesize ATP through aerobic cellular respiration.

Resting Membrane Potential (RMP)

The stable electrical voltage difference across the unstimulated plasma membrane, measuring approximately $-70\,\text{mV}$ in neurons, heavily established by $K^+$ diffusion.

Local Potential

A graded, decremental, and reversible fluctuation in membrane potential initiated at dendrites or soma in response to environmental or chemical stimuli.

Threshold

The critical membrane voltage (approximately $-55\,\text{mV}$) required to activate voltage-gated ion channels at the axon trigger zone.

Action Potential

A rapid, all-or-none, nondecremental reversal of membrane polarity driven by voltage-gated $\text{Na}^+$ and $\text{K}^+$ channels.

Absolute Refractory Period

The period following an action potential during which voltage-gated $\text{Na}^+$ channels are open or inactivated, preventing another action potential regardless of stimulus strength.

Saltatory Conduction

The rapid mode of nerve impulse transmission in myelinated nerve fibers where electrical signals leap from one node of Ranvier to the next.

Chemical Synapse

A junction where a presynaptic axon terminal releases neurotransmitters across a synaptic cleft to bind receptors on a postsynaptic cell.

Excitatory Postsynaptic Potential (EPSP)

A graded local depolarization of the postsynaptic membrane toward threshold, typically resulting from the inward movement of $\text{Na}^+$.

Temporal Summation

The algebraic addition of postsynaptic potentials occurring when a single presynaptic neuron fires rapidly in close succession at a single synapse.

Spatial Summation

The summation of postsynaptic potentials generated simultaneously by multiple distinct presynaptic terminals at different sites on the postsynaptic neuron.

Basement Membrane

An extracellular layer containing collagen and glycoproteins situated between an epithelium and its underlying connective tissue, anchoring the tissue.

Pseudostratified Columnar Epithelium

A single layer of cells that appears stratified because nuclei lie at different heights; all cells rest on the basement membrane, and the apical surface often features cilia and goblet cells.

Transitional Epithelium

A specialized stratified epithelium lining the urinary bladder and ureter whose apical cells change between rounded and flattened profiles upon distension.

Fibroblast

The primary, large, flat connective tissue cell responsible for secreting collagen fibers and ground substance.

Areolar Tissue

A loose fibrous connective tissue with loosely organized collagen and elastic fibers and abundant ground substance, located beneath epithelia and around blood vessels.

Dense Regular Connective Tissue

A dense fibrous tissue containing parallel, densely packed bundles of collagen fibers that forms tendons and ligaments to resist unidirectional mechanical stress.

Elastic Cartilage

A flexible, supportive cartilage containing abundant elastic fibers surrounded by chondrocytes in lacunae, found in the external ear and epiglottis.

Fibrocartilage

A tough cartilage with prominent, coarse bundles of collagen fibers that absorbs compressive shock in intervertebral discs and the pubic symphysis.

Desmosome

A mechanical cell junction that anchors adjacent cells together like a clothing snap, distributing shear stress and preventing epithelial tearing.

Gap Junction

An intercellular junction composed of six transmembrane proteins forming a ringlike connexon that allows direct passage of ions and small solutes between cells.

Holocrine Gland

An exocrine gland whose secretory cells accumulate products and entirely disintegrate, releasing dead cell fragments as part of the secretion (e.g., sebaceous glands).

Stratum Basale

The deepest layer of the epidermis consisting of a single layer of cuboidal to low columnar stem cells, tactile cells, and melanocytes undergoing active mitosis.

Stratum Lucidum

A thin, translucent epidermal zone found exclusively in thick skin (palms and soles), containing clear, flat keratinocytes packed with eleidin.

Stratum Corneum

The outermost epidermal stratum comprising up to $30$ layers of dead, scaly, keratinized cells that resist abrasion and water loss.

Dendritic (Langerhans) Cells

Immune macrophages originating in bone marrow that reside in the stratum spinosum and stratum granulosum to guard against toxins and pathogens.

Pacinian (Lamellar) Corpuscle

A deep dermal mechanoreceptor composed of concentric cellular lamellae that senses deep pressure, pokes, and vibrations.

Meissner (Tactile) Corpuscle

A superficial touch receptor located in dermal papillae that detects light touch and low-frequency vibrations, concentrated on fingertips and lips.

Sebum

An oily lipid secretion produced by holocrine sebaceous glands that lubricates the skin and hair shaft to prevent brittleness.

Ceruminous Glands

Modified apocrine glands in the external ear canal that secrete cerumen (earwax) to waterproof the canal and trap foreign particles.

ABCDE Rule

The diagnostic criteria used to recognize malignant melanoma: Asymmetry, Border irregularity, Color variation, Diameter greater than $1/4\,\text{inch}$, and Evolving morphology.

Third-Degree Burn

A full-thickness burn extending completely through the epidermis, dermis, and often into deeper subcutaneous tissues, requiring fluid therapy and skin grafting.

Plasma membrane

Controls the passage of materials into and out of the cell.

Phospholipid bilayer

Hydrophilic phosphate heads face outward; hydrophobic lipid tails point toward the center.

Glycolipids

Phospholipids with carbohydrate chains that contribute to cell recognition markers.

Cell-Adhesion Molecules (CAMs)

Proteins that mechanically link cells to surrounding extracellular material.

Isotonic solution

Has equal solute concentration to ICF, causing no change in cell volume.

Hypotonic solution

Has lower solute concentration than ICF, causing cells to absorb water and swell.

Hypertonic solution

Has higher solute concentration than ICF, causing cells to lose water and shrivel.

Sodium-Potassium (Na⁺-K⁺) Pump

Uses 1 ATP to transport 3 Na⁺ out and 2 K⁺ into the cell.

Microvilli

Membrane extensions that increase surface area for absorption forming the brush border.

Motile cilia

Hairlike processes that beat in waves to sweep materials across cell surfaces.

Rough Endoplasmic Reticulum

Ribosome-studded organelle that synthesizes membrane phospholipids and proteins.

Smooth Endoplasmic Reticulum

Synthesizes lipids and steroids, detoxifies drugs, and stores calcium ions.

Golgi complex

Synthesizes carbohydrates, modifies proteins, and packages them into vesicles.

Lysosomes

Vesicles containing hydrolytic enzymes for intracellular digestion and autophagy.

Peroxisomes

Organelles that oxidize organic molecules using O₂ and neutralize hydrogen peroxide.

Mitochondria

Organelles specialized for synthesizing ATP via aerobic respiration.

Four primary tissue types

Epithelial, connective, nervous, and muscular tissue.

Epithelial tissue features

Closely adhering cells, avascular, innervated, with apical and basal surfaces.

Simple squamous epithelium

Single flat cell layer facilitating rapid diffusion in lung alveoli and glomeruli.

Simple cuboidal epithelium

Single layer of cube-shaped cells specialized for absorption and secretion.

Simple columnar epithelium

Tall single cell layer with microvilli lining the digestive tract.

Pseudostratified columnar epithelium

Ciliated single-layer tissue appearing multilayered, lining the respiratory tract.