Chapter 26 AI Generated

A comprehensive vocabulary review set containing 100 flashcards covering kidney anatomy, nephron histology, renal physiology, countercurrent mechanisms, clinical testing, and lower urinary tract structures from Chapter 26.

Nephrology

The scientific study of the anatomy, physiology, and pathology of the kidneys.

Urology

The branch of medicine that deals with the male and female urinary systems and the male reproductive system.

Urologist

A physician who specializes in the branch of medicine dealing with the male and female urinary systems and the male reproductive system.

Nitrogenous wastes

Waste products containing nitrogen that are excreted in the urine, including urea, ammonia, creatinine, uric acid, and urobilin.

Calcitriol

The active form of vitamin D produced by the kidneys that helps regulate calcium homeostasis.

Erythropoietin

A hormone produced by the kidneys that stimulates the production of red blood cells.

Gluconeogenesis

The synthesis of new glucose molecules from non-carbohydrate sources, such as the amino acid glutamine in the kidneys and liver.

Osmolarity

A measure of the total number of dissolved particles (molecules, ions, or a mixture of both) per liter of solution.

Osmolality

A measure of solute concentration defined as the number of particles of solute per kilogram of water.

Retroperitoneal

The anatomical position of organs located posterior to the peritoneum of the abdominal cavity, such as the kidneys and ureters.

Renal hilum

An indentation near the center of the concave border of each kidney through which the ureter, blood vessels, lymphatic vessels, and nerves emerge.

Renal capsule

The deep, smooth, transparent layer of dense irregular connective tissue surrounding the kidney that serves as a barrier against trauma and maintains kidney shape.

Adipose capsule

The middle layer of fatty tissue surrounding the renal capsule that protects the kidney from trauma and holds it firmly in place within the abdominal cavity.

Renal fascia

The superficial thin layer of dense irregular connective tissue that anchors the kidney to surrounding structures and to the abdominal wall.

Renal cortex

The superficial, light red, smooth-textured functional region of the kidney extending from the renal capsule to the bases of the renal pyramids and into the spaces between them.

Renal medulla

The deep, darker reddish-brown inner region of the kidney consisting of several cone-shaped renal pyramids.

Renal pyramids

Cone-shaped structures within the renal medulla whose wide bases face the renal cortex and apices point toward the renal hilum.

Renal papilla

The apex (narrower end) of a renal pyramid that points toward the renal hilum and expels filtrate into a minor calyx.

Renal columns

Portions of the renal cortex that extend between adjacent renal pyramids.

Parenchyma

The functional portion of the kidney, consisting of the renal cortex and the renal pyramids of the renal medulla together.

Nephrons

The microscopic functional units of the kidneys, numbering about $1\,\text{million}$ per kidney.

Minor calyx

A cuplike structure receiving filtrate from the papillary ducts of one renal papilla and delivering it to a major calyx.

Major calyx

A large cavity formed by the convergence of minor calyces that conducts urine into the renal pelvis.

Renal pelvis

A single large cavity into which the major calyces drain and through which urine passes out into the ureter.

Renal sinus

A cavity within the kidney into which the hilum expands, containing part of the renal pelvis, calyces, blood vessels, nerves, and adipose tissue.

Renal blood flow

The blood flow through both kidneys, which is about $1200\,\text{mL}$ per minute in adults (about $20\text{--}25\%$ of resting cardiac output).

Renal lobe

A structural division consisting of a renal pyramid, some of the renal column on either side, and the renal cortex at the base of the pyramid.

Arcuate arteries

Arteries that arch between the renal medulla and cortex at the bases of the renal pyramids.

Cortical radiate arteries

Arteries that branch from arcuate arteries, radiate outward into the renal cortex, and give off afferent arterioles.

Glomerulus

A tangled, ball-shaped capillary network positioned between afferent and efferent arterioles where blood plasma filtration occurs.

Efferent arteriole

A vessel that carries blood out of the glomerulus and divides to form peritubular capillaries or vasa recta.

Peritubular capillaries

Capillary networks that arise from efferent arterioles and surround tubular portions of nephrons in the renal cortex.

Vasa recta

Long, loop-shaped capillaries extending from efferent arterioles that supply tubular portions of nephrons in the renal medulla.

Renal corpuscle

The part of a nephron where blood plasma is filtered, comprising the glomerulus and the glomerular capsule.

Glomerular capsule

A double-walled epithelial cup surrounding the glomerular capillaries that receives filtered plasma; also known as Bowman's capsule.

Renal tubule

The tubular portion of a nephron into which filtered fluid passes, consisting of the proximal convoluted tubule, nephron loop, and distal convoluted tubule.

Cortical nephrons

Nephrons ($80\text{--}85\%$ of total) whose corpuscles lie in the outer renal cortex and have short nephron loops penetrating only into the outer medulla.

Juxtamedullary nephrons

Nephrons ($15\text{--}20\%$ of total) whose corpuscles lie deep in the cortex near the medulla and possess long nephron loops extending deep into the medulla.

Podocytes

Modified simple squamous epithelial cells forming the visceral layer of the glomerular capsule whose pedicels wrap around glomerular capillaries.

Pedicels

Footlike processes extending from podocytes that encircle glomerular capillaries to form filtration slits.

Capsular space

The lumen between the visceral and parietal layers of the glomerular capsule into which fluid filtered from glomerular capillaries enters.

Macula densa

Crowded, specialized columnar tubule cells in the final part of the ascending limb of the nephron loop that make contact with the afferent arteriole.

Juxtaglomerular cells

Modified smooth muscle fibers in the wall of the afferent arteriole alongside the macula densa that secrete the enzyme renin.

Juxtaglomerular apparatus

The specialized structure formed by the macula densa and juxtaglomerular cells that helps regulate blood pressure within the kidneys.

Principal cells

Cells in the late distal convoluted tubule and collecting ducts having receptors for ADH and aldosterone that reabsorb $\text{Na}^+$ and secrete $\text{K}^+$.

Intercalated cells

Cells in the late distal convoluted tubule and collecting ducts that reabsorb $\text{HCO}_3^-$ and $\text{K}^+$ and secrete $\text{H}^+$ to regulate blood pH.

Glomerular filtration

The first step of urine production in which water and most solutes in blood plasma move across glomerular capillary walls into the glomerular capsule.

Tubular reabsorption

The process by which tubule and duct cells return about $99\%$ of filtered water and useful solutes to the bloodstream.

Tubular secretion

The process by which renal tubule and duct cells transport wastes, drugs, and excess ions from the blood and tubule cells into the tubular fluid.

Glomerular filtrate

The fluid that passes across the filtration membrane and enters the capsular space of the renal corpuscle.

Filtration fraction

The fraction of blood plasma in the afferent arterioles that becomes glomerular filtrate, typically $0.16\text{--}0.20$ ($16\text{--}20\%$).

Filtration membrane

The leaky barrier formed by glomerular endothelial cells, the basement membrane, and podocyte filtration slits that filters water and small solutes.

Mesangial cells

Contractile cells located among glomerular capillaries and in the cleft between arterioles that regulate the surface area available for filtration.

Filtration slits

The narrow spaces between adjacent pedicels of podocytes that allow passage of filtered fluid into the capsular space.

Slit membrane

A thin membrane extending across each filtration slit that permits the passage of molecules smaller than $0.006\text{--}0.007\,\mu\text{m}$.

Glomerular blood hydrostatic pressure

The hydrostatic blood pressure in glomerular capillaries (about $55\,\text{mmHg}$) that promotes filtration by forcing fluid through the filtration membrane.

Capsular hydrostatic pressure

The hydrostatic back pressure exerted against the filtration membrane by fluid already residing in the capsular space and renal tubule (about $15\,\text{mmHg}$).

Blood colloid osmotic pressure

The osmotic pressure exerted by suspended plasma proteins in glomerular capillaries (averaging $30\,\text{mmHg}$) that opposes filtration.

Net filtration pressure

The total pressure promoting filtration, calculated as $\text{GBHP} - \text{CHP} - \text{BCOP}$ (normally $10\,\text{mmHg}$).

Glomerular filtration rate

The amount of filtrate formed in all renal corpuscles of both kidneys each minute, averaging $125\,\text{mL/min}$ in males and $105\,\text{mL/min}$ in females.

Renal autoregulation

The intrinsic capability of the kidneys to maintain a constant renal blood flow and GFR despite everyday systemic blood pressure changes.

Myogenic mechanism

An autoregulatory mechanism where elevated blood pressure stretches afferent arteriole smooth muscle, triggering contraction that reduces blood flow and normalizes GFR.

Tubuloglomerular feedback

An autoregulatory mechanism where macula densa cells detect increased delivery of $\text{Na}^+$, $\text{Cl}^-$, and water, inhibiting nitric oxide release to constrict afferent arterioles.

Paracellular reabsorption

A passive reabsorption route in which fluid and dissolved solutes leak between adjacent renal tubule cells through leaky tight junctions.

Transcellular reabsorption

A reabsorption route in which a substance passes through the apical membrane of a tubule cell, traverses the cytosol, and exits through the basolateral membrane.

Primary active transport

Transport across a membrane that is directly powered by energy derived from the hydrolysis of ATP, such as by the sodium-potassium pump.

Secondary active transport

Membrane transport driven by the energy stored in an ion's electrochemical gradient rather than directly by ATP hydrolysis.

Symporters

Membrane transport proteins that move two or more substances simultaneously in the same direction across a plasma membrane.

Antiporters

Membrane transport proteins that move two or more substances simultaneously in opposite directions across a plasma membrane.

Transport maximum

The upper velocity limit on how fast a specific transporter protein can work across a renal membrane, measured in $\text{mg/min}$.

Obligatory water reabsorption

Water reabsorption ($90\%$ of total) in the PCT and descending limb that is compelled by osmosis to follow reabsorbed solutes such as $\text{Na}^+$ and glucose.

Facultative water reabsorption

Water reabsorption of the final $10\%$ of filtered water ($10\text{--}20\,\text{liters/day}$) that occurs mainly in collecting ducts and is regulated by antidiuretic hormone.

Tubular fluid

The filtered fluid once it enters the proximal convoluted tubule, whose composition is modified by reabsorption and secretion as it flows through the nephron.

Aquaporin-1

An integral membrane water channel protein located in the PCT and descending limb that greatly increases the rate of water movement across cell membranes.

Carbonic anhydrase

An enzyme that catalyzes the reversible reaction between carbon dioxide and water to form carbonic acid.

Renin

An enzyme secreted by juxtaglomerular cells when blood volume or blood pressure decreases, which clips angiotensinogen into angiotensin I.

Angiotensin-converting enzyme

An enzyme that converts angiotensin I to active angiotensin II by clipping off two amino acids.

Aldosterone

A hormone released by the adrenal cortex that stimulates principal cells in collecting ducts to reabsorb more $\text{Na}^+$ and secrete more $\text{K}^+$.

Antidiuretic hormone

A hormone released by the posterior pituitary (also called vasopressin) that increases water permeability in principal cells by inserting aquaporin-2 channels.

Aquaporin-2

A water channel protein stored in intracellular vesicles of principal cells that inserts into apical membranes in response to ADH stimulation.

Diabetes insipidus

A condition characterized by the pathological absence of ADH activity, resulting in excretion of up to $20\,\text{liters}$ of dilute urine daily.

Atrial natriuretic peptide

A peptide hormone secreted by cardiac atria in response to elevated blood volume that relaxes mesangial cells, increases filtration surface area, and elevates GFR.

Parathyroid hormone

A hormone released during hypocalcemia that stimulates $\text{Ca}^{2+}$ reabsorption in early DCT cells and inhibits phosphate reabsorption in PCT cells.

Countercurrent flow

The flow of fluid in opposite directions in adjacent, parallel tubes, such as between limbs of the nephron loop or limbs of the vasa recta.

Countercurrent multiplication

The process by which countercurrent flow in the long nephron loop establishes a progressively increasing osmotic gradient in the medullary interstitial fluid.

Countercurrent multiplier

The long nephron loop of a juxtamedullary nephron, which establishes the medullary osmotic gradient via countercurrent flow.

Countercurrent exchange

The passive process by which solutes and water are exchanged between the blood of the vasa recta and the medullary interstitium as a result of countercurrent flow.

Countercurrent exchanger

The vasa recta, which maintains the osmotic gradient in the renal medulla through countercurrent exchange without washing it out.

Urea recycling

The continuous transfer of urea between collecting ducts, medullary interstitial fluid, and thin limbs of nephron loops that promotes medullary hyperosmolarity.

Urinalysis

An analysis of the volume and physical, chemical, and microscopic properties of urine used to evaluate body and kidney function.

Blood urea nitrogen test

A blood test measuring the nitrogen part of urea resulting from catabolism and deamination of amino acids, which rises steeply when GFR declines.

Plasma creatinine

A catabolic product of creatine phosphate in skeletal muscle whose blood concentration exceeds $1.5\,\text{mg/dL}$ when kidney function is impaired.

Renal plasma clearance

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

Inulin

A plant polysaccharide that is freely filtered by glomeruli but neither reabsorbed nor secreted, whose clearance ($125\,\text{mL/min}$) equals the GFR.

Para-aminohippuric acid

An organic anion administered intravenously that is completely filtered and secreted in a single pass, used clinically to measure renal plasma flow.

Renal plasma flow

The volume of plasma that passes through both kidneys in one minute, typically averaging $650\,\text{mL/min}$ (about $55\%$ of renal blood flow).

Ureters

Paired retroperitoneal muscular tubes, $25\text{--}30\,\text{cm}$ long, that conduct urine from each renal pelvis to the urinary bladder by peristalsis.

Trigone

A smooth triangular area in the floor of the urinary bladder bounded by the two posterior ureteral openings and the anterior internal urethral orifice.

Detrusor muscle

The intermediate muscularis layer of the urinary bladder, consisting of inner longitudinal, middle circular, and outer longitudinal smooth muscle layers.

Micturition reflex

A spinal reflex coordinated in sacral segments S2 and S3 triggered by bladder stretch receptors that contracts the detrusor muscle and relaxes the urethral sphincters.