Human Anatomy and Physiology: Organ Systems and Development

Comprehensive vocabulary review flashcards covering renal function, cardiovascular mechanics, respiratory physiology, neurobiology, and reproductive development.

Nephron

The microscopic functional unit of the kidney, consisting of renal tubules and an associated vascular network that filters approximately $180\,\text{liters}$ of blood fluid daily.

Glomerular Capsule

The cuplike proximal sac of a nephron tubule that surrounds the glomerulus and receives protein-free fluid during glomerular filtration.

Glomerular Filtration

The bulk flow process driven by high capillary blood pressure that forces a protein-free solution of fluid and small solutes from blood plasma into the glomerular capsule.

Tubular Reabsorption

The active and passive reclamation of filtered water, sodium ($Na^+$), chloride ($Cl^-$), glucose, amino acids, and bicarbonate from the tubule lumen back into the peritubular capillaries.

Tubular Secretion

The active movement of excess solutes, drugs (such as penicillin), metabolic wastes, ammonium, and ions ($H^+$ and $K^+$) from the peritubular capillaries directly into the tubule for elimination.

Antidiuretic Hormone (ADH)

A peptide hormone synthesized by the hypothalamus and released by the posterior pituitary gland that inserts aquaporins into collecting ducts to increase water reabsorption and produce concentrated urine.

Aldosterone

A steroid hormone secreted by the adrenal cortex under the control of the renin-angiotensin system that enhances sodium reabsorption in the distal tubule and collecting ducts.

Atrial Natriuretic Hormone (ANH)

A cardiac hormone released by the atria in response to high blood volume stretching that inhibits renal sodium reabsorption, promoting sodium and water excretion to lower blood pressure.

Erythropoietin

A hormone produced by oxygen-sensitive cells in the kidneys in response to decreased blood oxygen levels that stimulates red blood cell production in the bone marrow.

Micturition

The urination reflex initiated by stretch receptors in the bladder wall, mediated by an involuntary internal smooth muscle sphincter and a voluntary external skeletal muscle sphincter.

Arteries

Thick-walled blood vessels composed of endothelium, smooth muscle, and connective tissue that carry blood away from the heart under high hydrostatic pressure.

Arterioles

Small vascular branches lacking a thick connective tissue layer that adjust their lumen diameter to regulate blood pressure and distribute blood into capillary beds.

Capillaries

Microscopic, thin-walled, single-cell-thick porous vessels where nutrient, gas, and waste exchange occurs between the blood plasma and interstitial fluid.

Lymphatic System

A vascular network of blind-ended capillaries and vessels that absorbs excess interstitial fluid, returns it to venous circulation, transports lipids, and assists immune defense.

Myocardium

The thick middle layer of the heart wall made of electrical-conducting cardiac muscle tissue responsible for contractile pumping action.

Pericardium

A tough, double-layered connective tissue sac that surrounds, anchors, and lubricates the heart while preventing it from overfilling.

Sinoatrial (SA) Node

A cluster of specialized cardiac muscle cells located in the upper wall of the right atrium that spontaneously initiates electrical impulses as the physiological pacemaker.

Systole

The phase of the cardiac cycle when heart chambers contract to eject blood; ventricular systole closes the atrioventricular valves to create the first heart sound ('lub').

Diastole

The relaxation phase of the cardiac cycle when the chambers fill with blood; ventricular diastole closes the semilunar valves to generate the second heart sound ('dub').

Atherosclerosis

A progressive cardiovascular disease marked by cholesterol, low-density lipoprotein (LDL), and inflammatory plaque buildup within arterial walls, narrowing blood flow.

Alveoli

Microscopic, thin-walled terminal air sacs in the lungs lined with simple squamous epithelium that provide approximately $800\,\text{ft}^2$ of surface area for gas exchange.

Surfactant

A lipoprotein mixture secreted by alveolar cells that reduces alveolar surface tension, preventing lung collapse during expiration.

Tidal Volume

The volume of air inspired and expired during a normal, restful breath, measuring approximately $500\,\text{mL}$ in healthy adults.

Oxyhemoglobin

The bright red chemical complex formed in red blood cells when molecular oxygen ($O_2$) binds reversibly to the iron atoms of hemoglobin's heme groups.

Schwann Cells

Glial cells in the peripheral nervous system (PNS) that produce the insulating myelin sheath around axons to accelerate action potential propagation via saltatory conduction.

Depolarisation

The initial upward phase of a neuronal action potential caused by the opening of voltage-gated sodium channels and the rapid influx of positive $Na^+$ ions into the cell.

Repolarization

The restoration of a resting membrane potential following depolarization, driven by the closure of voltage-gated $Na^+$ channels and the efflux of $K^+$ ions through open potassium channels.

Neurotransmitters

Chemical ligands packaged into presynaptic vesicles that diffuse across the synaptic cleft to bind specific receptors on the postsynaptic membrane.

Cerebrum Anatomy

The largest brain division, featuring outer gray matter (cerebral cortex) containing interneurons for processing, inner white matter tracts, the corpus callosum, and distinct functional lobes.

Major Brain Divisions

The gross anatomical hierarchy of the brain, consisting of the forebrain (cerebrum, corpus callosum, thalamus), midbrain, and hindbrain (pons, cerebellum, medulla oblongata).

Sperm Structure

The differentiated male haploid gamete consisting of an acrosome cap with digestive enzymes, a chromosome-containing head, an energy-generating mitochondrial midpiece, and a locomotor flagellum tail.

Spermatogenesis in the Testes

The developmental lineage housed within the uncoiled seminiferous tubules where diploid spermatogonia undergo mitosis and meiosis to form spermatids and mature spermatozoa under Sertoli cell support.

Corpus Luteum

An endocrine structure formed from an ovarian follicle following ovulation that produces progesterone to sustain the vascularized uterine lining during pregnancy.

Endometriosis

A gynecological condition in which uterine endometrial tissue implants outside the uterus onto the ovaries or fallopian tubes, undergoing cyclic bleeding and causing chronic pelvic inflammation.

Embryonic Disk and Early Implantation

The process by which the blastocyst attaches to the endometrium, with its outer trophoblast invading maternal tissue and its inner cell mass differentiating into the bilaminar disk of ectoderm and endoderm.

Ectoderm

The outermost embryonic primary germ layer that gives rise to the nervous system, epidermis of the skin, corneal epithelium, mammary glands, and tooth enamel.

Mesoderm

The middle embryonic germ layer that forms connective tissues, bone, cartilage, all muscle types (skeletal, smooth, cardiac), blood vessels, kidneys, and gonads.

Endoderm

The innermost embryonic germ layer that forms the epithelial lining of the gastrointestinal and respiratory tracts, as well as the liver, pancreas, thyroid, and urinary bladder.

Neurulation

The embryonic folding process occurring in weeks 3–8 that forms the neural tube from ectoderm, an event heavily dependent on maternal folate levels to prevent neural tube defects.

Senescence

The progressive, age-related functional deterioration of cells and organ systems over time, driven by cumulative DNA mutations, reactive oxygen species, and telomere shortening.