A&P II - Urinary System and Fluid Balance

Vocabulary flashcards covering the gross anatomy, histology, nephron physiology, hormonal controls, fluid compartments, and acid-base parameters of the urinary system.

Kidneys (Anatomical Location)

Retroperitoneal organs located between the 12th thoracic ($\text{T12}$) and 3rd lumbar ($\text{L3}$) vertebrae, with the right kidney positioned slightly lower than the left.

Perirenal Fat

A thick layer of adipose tissue surrounding each kidney that helps protect it and keep it anchored in place alongside renal fascia.

Hilum (Kidney)

A medial indentation on the kidney where the renal vein and ureter leave, and the renal artery enters.

Renal Capsule

A layer of thick connective tissue directly enveloping the external surface of the kidney.

Renal Cortex

The outer tissue layer directly beneath the renal capsule that surrounds the renal medulla and projects inward to form renal columns.

Renal Medulla

The inner region of the kidney composed of triangular structures known as renal pyramids.

Renal Pyramids

Triangular structures in the renal medulla whose broad bases border the cortex and whose apices (renal papillae) point toward the center of the kidney.

Renal Papilla

The apex of a renal pyramid that points toward the center of the kidney and empties urine into a minor calyx.

Renal Columns

Extensions of the renal cortex that project downward between adjacent renal pyramids.

Minor Calyx

A cup-like projection that surrounds the renal papilla of each pyramid to collect draining urine.

Major Calyx

A wider urine-collecting channel formed by the convergence of several minor calyces.

Renal Pelvis

The large funnel-shaped basin formed by the union of major calyces that conducts urine into the ureter.

Nephron

The functional unit of the kidney, with more than $1{,}000{,}000$ present in each kidney, consisting of a renal corpuscle and a renal tubule.

Renal Corpuscle

The initial filtration component of a nephron, consisting of a capillary cluster called the glomerulus and an enveloping glomerular (Bowman's) capsule.

Glomerulus

A specialized cluster of capillaries located inside the glomerular capsule where blood filtration begins.

Glomerular (Bowman's) Capsule

A double-layered epithelial cup that encases the glomerulus to receive filtered fluid.

Renal Tubule

The tubular portion of the nephron comprised sequentially of the proximal convoluted tubule (PCT), nephron loop (loop of Henle), distal convoluted tubule (DCT), and collecting ducts.

Juxtaglomerular Apparatus (JGA)

A specialized structure formed where the ascending limb of the loop contacts the afferent arteriole; its modified cells secrete renin to raise blood pressure.

Renal Blood Flow Rate

The volume of blood passing through the kidneys per minute, which is approximately $1\,\text{L/min}$.

Renal Blood Flow Pathway

Abdominal aorta $\rightarrow$ renal artery $\rightarrow$ smaller arterial branches $\rightarrow$ afferent arterioles $\rightarrow$ glomerular capillaries $\rightarrow$ efferent arterioles $\rightarrow$ peritubular capillaries $\rightarrow$ larger veins $\rightarrow$ renal vein $\rightarrow$ inferior vena cava (IVC).

Ureters

Tubular organs lined with transitional epithelium, each measuring approximately $25\,\text{cm}$ in length, that carry urine from the renal pelvis to the urinary bladder.

Urinary Bladder

A pelvic organ lined with transitional epithelium located posterior to the symphysis pubis that stores urine.

Rugae (Urinary Bladder)

Folds in the mucosa of an empty urinary bladder that unfold to allow expansion as urine accumulates.

Trigone

A smooth, triangular floor area in the urinary bladder outlined by the two ureteral openings at its base and the internal urethral opening at its apex.

Detrusor Muscle

The smooth muscle layer of the urinary bladder wall.

Internal Urethral Sphincter

An involuntary sphincter composed of smooth muscle fibers located at the bladder-urethra junction.

External Urethral Sphincter

A voluntary sphincter composed of skeletal muscle fibers surrounding the urethra.

Female Urethra

A transitional epithelium-lined canal measuring approximately $3-4\,\text{cm}$ in length that carries urine to the outside.

Male Urethra

A duct measuring approximately $20\,\text{cm}$ in length divided into prostatic, membranous, and penile (spongy) segments that transports both urine and semen.

Glomerular Filtration Rate (GFR)

The volume of filtrate formed by both kidneys per minute, equal to $125\,\text{mL/min}$ or approximately $180\,\text{L/day}$.

Tubular Reabsorption

The recovery of water and essential solutes (like glucose and protein) from filtrate back into the blood, leaving only $1\%$ of the initial filtrate to form urine.

Ascending Limb of the Nephron Loop

The specific segment of the renal tubule that is completely impermeable to water during tubular reabsorption.

Tubular Secretion

The active passage of waste substances, including creatinine and medications such as penicillin, from peritubular blood into the tubular filtrate.

Urochrome

The primary pigment molecule responsible for the characteristic yellow color of urine.

Micturition

The physiological process of discharging urine from the bladder, also referred to as urination or voiding.

Antidiuretic Hormone (ADH)

A hormone produced by the hypothalamus and released by the posterior pituitary that stimulates water reabsorption by the kidney tubules, decreasing urine volume.

Aldosterone

A mineralocorticoid synthesized and released by the adrenal cortex that promotes $\text{Na}^+$ reabsorption, causing osmotic water retention and decreasing urine volume.

Atrial Natriuretic Hormone (Atriopeptin)

A cardiac hormone released by the atria that stimulates $\text{Na}^+$ and water excretion, thereby increasing urine output while lowering blood volume and pressure.

Intracellular Fluid (ICF)

Fluid contained within cells that makes up about $2/3$ of total body fluid (approximately $40\%$ of total body weight), having $\text{K}^+$ as its chief cation and phosphate as its chief anion.

Extracellular Fluid (ECF)

Fluid situated outside cells that constitutes about $1/3$ of total body fluid (approximately $20\%$ of total body weight), having $\text{Na}^+$ as its chief cation and chloride as its chief anion.

Interstitial Fluid

The component of extracellular fluid that bathes tissue cells, representing $3/4$ of the ECF and approximately $15\%$ of total body weight.

Intravascular Fluid (Plasma)

The liquid fraction of blood representing $1/4$ of the extracellular fluid and roughly $5\%$ of total body weight.

Acidosis

An acid-base disturbance defined by an arterial blood pH below $7.35$, leading clinically to depression of the central nervous system (CNS).

Alkalosis

An acid-base disturbance defined by an arterial blood pH above $7.45$, leading clinically to hyperexcitability of the central nervous system (CNS).