Renal and Reproductive Physiology Vocabulary Flashcards

Comprehensive vocabulary flashcards covering renal clearance, glomerular filtration, tubular transport mechanisms, countercurrent multiplication, osmoregulation, endocrine functions of the kidney, reproductive genetics, gonadotropins, spermatogenesis, oogenesis, lactation, and hypothalamic-pituitary regulation based on the provided notes.

Renal Clearance

The volume of plasma that is completely cleared of a specific substance by the kidneys per unit of time, typically expressed in $\text{mL/min}$.

Renal Clearance Formula

The formula used to calculate renal clearance: $C = \frac{U \cdot V}{P}$, where $C$ is clearance in $\text{mL/min}$, $U$ is urine concentration, $V$ is urine flow rate, and $P$ is plasma concentration.

Clearance Ratio (CR)

The ratio of the clearance of a substance ($C_x$) to the clearance of inulin ($C_{\text{inulin}}$), used to determine whether a substance undergoes net reabsorption ($CR < 1$), net secretion ($CR > 1$), or only filtration ($CR = 1$).

Glomerular Filtration Rate (GFR)

The volume of filtrate produced by all nephrons in both kidneys per minute, which averages approximately $120-125\,\text{mL/min}$ (or $180\,\text{L/day}$) in healthy adults.

Podocytes

Specialized epithelial cells that wrap around the glomerular capillaries to form the visceral layer of Bowman's capsule, featuring foot processes that interdigitate to create filtration slits.

Glomerular Hydrostatic Pressure (GHP)

The blood pressure within the glomerular capillaries, approximately $45\,\text{mmHg}$, which promotes filtration by pushing fluid out of the capillaries into Bowman's capsule.

Net Filtration Pressure (NFP)

The overall pressure driving glomerular filtration, calculated as $NFP = GHP - (BCHP + \text{Oncotic Pressure})$, yielding a net force of about $10\,\text{mmHg}$ favoring filtration.

Inulin

A fructose polymer with a molecular weight of around $5000\,\text{daltons}$ that is freely filtered but neither reabsorbed nor secreted, serving as the gold standard marker for measuring GFR.

Creatinine

An endogenous waste product of muscle metabolism that is freely filtered and slightly secreted by renal tubules, commonly measured to provide an approximate clinical estimate of GFR.

Myogenic Mechanism

An intrinsic renal autoregulatory response wherein vascular smooth muscle in the afferent arteriole constricts in response to increased systemic blood pressure to protect GFR and prevent hyperfiltration.

Tubuloglomerular Feedback (TGF)

An autoregulatory process where macula densa cells in the juxtaglomerular apparatus sense increased sodium chloride concentration in the distal tubule and signal the afferent arteriole to constrict, reducing GFR and RBF.

Renal Blood Flow (RBF)

The total volume of blood flowing through the kidneys per unit of time, equal to about $25\%$ of cardiac output ($1.25\,\text{L/min}$ or $1800\,\text{L/day}$ for a cardiac output of $5\,\text{L/min}$).

Fick Principle

A physiological principle stating that the amount of a substance entering an organ equals the amount leaving plus the amount excreted or consumed, used to measure true renal plasma flow.

Para-aminohippuric Acid (PAH)

A substance filtered and actively secreted by the kidneys with a $90-95\%$ extraction ratio, whose clearance is used to measure effective renal plasma flow.

Tubular Reabsorption

The process by which the kidneys reclaim water, ions, and nutrients from the tubular filtrate and return them to the bloodstream to maintain homeostasis.

Tubular Secretion

The active transport of substances from peritubular capillary blood into the tubular fluid to eliminate waste products, regulate blood pH, and excrete excess ions.

Transcellular Transport

A transport pathway where molecules enter one side of a tubular cell across the apical membrane, travel through its cytoplasm, and exit through the basolateral membrane.

Paracellular Transport

The passive movement of solutes (such as $\text{Cl}^-$ and $\text{K}^+$) and water between adjacent tubular epithelial cells through tight junctions.

Proximal Convoluted Tubule (PCT)

The segment of the nephron responsible for reabsorbing $65-70\%$ of filtered water, sodium, and electrolytes, and $100\%$ of filtered glucose and amino acids, consuming the most ATP energy.

Isosmotic Reabsorption

The passive reabsorption of water in the PCT via osmosis through Aquaporin 1 channels that strictly accompanies solute reabsorption in equal proportions.

Thick Ascending Limb of Loop of Henle

A water-impermeable tubule segment that actively reabsorbs sodium, potassium, and chloride via the $\text{Na}^+/\text{K}^+/2\text{Cl}^-$ cotransporter, which is selectively blocked by loop diuretics such as furosemide.

Principal Cells

Cells in the late distal tubule and collecting duct that reabsorb sodium via ENaC channels and secrete potassium via ROMK channels under aldosterone regulation, and reabsorb water via Aquaporin-2 under ADH regulation.

Intercalated Cells

Cells in the collecting duct that regulate acid-base balance; Type A cells secrete $\text{H}^+$ via $H^+\text{-ATPase}$ during acidosis, while Type B cells secrete $\text{HCO}_3^-$ during alkalosis.

Countercurrent Multiplier

The functional system in the loop of Henle that deposits $\text{NaCl}$ into the medullary interstitium and recycles urea to establish a steep osmotic gradient from $300\,\text{mOsm/L}$ in the cortex to $1200\,\text{mOsm/L}$ in the inner medulla.

Countercurrent Exchanger

The passive process occurring in the vasa recta capillaries that maintains the medullary osmotic gradient by exchanging solutes and water without washing out the hyperosmotic interstitium.

Edema

The abnormal accumulation of fluid in the interstitial spaces of tissues or body cavities resulting from an imbalance in Starling forces, increased capillary permeability, or lymphatic obstruction.

Capillary Fluid Exchange Diagram

A visual model illustrating Starling forces across a capillary bed, showing hydrostatic pressure favoring fluid movement out into the interstitial space and oncotic pressure favoring fluid draw into the capillary.

Osmoreceptors

Sensory neurons located in the circumventricular organs (OVLT and SFO) of the hypothalamus that detect changes in plasma osmolality to regulate thirst and ADH release.

Antidiuretic Hormone (ADH)

A peptide hormone synthesized in the supraoptic and paraventricular nuclei of the hypothalamus that binds to $V_2$ receptors on principal cells to insert Aquaporin-2 channels and increase water reabsorption.

Renin

An enzyme secreted by juxtaglomerular cells in response to renal hypoperfusion, low $\text{NaCl}$ at the macula densa, or sympathetic stimulation, which cleaves angiotensinogen into angiotensin I.

Erythropoietin (EPO)

A $34000\,\text{dalton}$ glycoprotein hormone composed of $166$ amino acids, produced primarily ($90\%$) by renal cortical interstitial cells in response to tissue hypoxia to stimulate erythropoiesis in bone marrow.

Calcitriol

The active form of vitamin D ($1,25\text{-dihydroxycholecalciferol}$) produced in the kidneys by $1\alpha\text{-hydroxylase}$ under PTH stimulation, which enhances intestinal calcium absorption and bone mineralization.

SRY Gene

The sex-determining region gene on the short arm of the Y chromosome encoding Testis-Determining Factor (TDF), which directs undifferentiated gonads to develop into testes.

Anti-Müllerian Hormone (AMH)

A glycoprotein hormone secreted by embryonic Sertoli cells that causes regression of the Müllerian ducts, preventing female internal reproductive tract formation in genetic males.

Thelarche

The initiation of breast development driven by rising estrogen levels, usually representing the first physical sign of female puberty.

Menarche

The occurrence of the first menstrual period, typically taking place about 2 years after the onset of thelarche and marking reproductive maturation.

Follicle-Stimulating Hormone (FSH)

A glycoprotein hormone with a half-life of $3-4\,\text{hours}$ secreted by anterior pituitary gonadotrophs that promotes follicular development and aromatase activity in females and supports spermatogenesis in males.

Luteinizing Hormone (LH)

A glycoprotein hormone with a half-life of $50\,\text{mins}$ secreted by anterior pituitary gonadotrophs that triggers ovulation and corpus luteum formation in females and Leydig cell testosterone production in males.

Human Chorionic Gonadotropin (hCG)

A placental glycoprotein hormone secreted by syncytiotrophoblasts that maintains the corpus luteum to sustain progesterone production during early pregnancy.

Human Placental Lactogen (hPL)

A placental hormone that modifies maternal metabolism by inducing insulin resistance and promoting lipolysis, thereby ensuring glucose and free fatty acid delivery to the fetus.

Hogben Test

A historical biological pregnancy test introduced in 1937 wherein a woman's urine was injected into a female Xenopus laevis toad, triggering egg release within $8-12\,\text{hours}$ if hCG was present.

Spermatogenesis Flowchart

A diagrammatic representation showing the lineage of male germ cells from Type A dark and pale spermatogonia through Type B spermatogonia, primary and secondary spermatocytes, spermatids, to mature spermatozoa.

Spermatogenesis

The complete process of male gamete production within the seminiferous tubules taking approximately $64-72\,\text{days}$, consisting of proliferation, growth, meiotic maturation, and spermiogenesis.

Spermiogenesis

The structural transformation phase of spermatogenesis in which round haploid spermatids undergo nuclear condensation, acrosome formation, flagellum development, and cytoplasmic shedding to become motile spermatozoa.

Sertoli Cells

Somatic nurse cells in the seminiferous tubules that form the blood-testis barrier, provide nutrients to developing germ cells, phagocytose residual bodies, and secrete inhibin B.

Leydig Cells

Interstitial cells located between seminiferous tubules that produce approximately $95\%$ of circulating testosterone in males under LH stimulation.

Oogenesis

The process of female gamete formation in the ovaries, initiating during fetal life, arresting at prophase I until puberty, halting at metaphase II until fertilization, and yielding a single mature ovum.

Oocyte Maturation Inhibitor (OMI)

A peptide factor secreted by follicular granulosa cells that maintains primary oocytes in meiotic arrest at the diplotene stage of prophase I from fetal development until puberty.

Graafian Follicle

A mature tertiary ovarian follicle containing a secondary oocyte, a large fluid-filled antrum, and a prominent theca layer, prepared to rupture upon an LH surge.

Corpus Luteum

A temporary endocrine structure formed from the collapsed follicle post-ovulation that secretes progesterone and estrogen to prepare and maintain the endometrium for implantation.

Milk Ejection Reflex

A neuroendocrine reflex activated by infant suckling that causes posterior pituitary oxytocin release, inducing myoepithelial cell contraction around mammary alveoli to expel milk.

Feedback Inhibitor of Lactation (FIL)

A local whey protein in breast milk that down-regulates milk secretion when the mammary gland remains unevacuated, regulating production through a local demand-supply loop.

Pituitary Gland Anatomical Subdivisions

A diagram illustrating the structural divisions of the pituitary gland, highlighting the anterior pituitary (pars distalis, pars tuberalis, pars intermedia) and posterior pituitary connected via the infundibular stalk.

Hypothalamic Releasing Factors

Neuropeptides synthesized by hypothalamic neurosecretory neurons and transported through the hypothalamo-hypophyseal portal system to stimulate or inhibit anterior pituitary hormone release.