Renal Function Lecture Notes Flashcards

A comprehensive set of vocabulary flashcards covering renal anatomy, physiological processes, and clinical diagnostic tests based on the lecture notes.

Nephron

The basic functional unit of the kidney, with approximately $1$ to $1.5$ million present in each kidney.

Cortical nephron

A type of nephron situated primarily in the cortex of the kidney responsible for the removal of waste products and reabsorption of nutrients.

Juxtamedullary nephron

A type of nephron with longer loops of Henle extending deep into the medulla, primarily functioning in the concentration of urine.

Total Renal Blood Flow

The volume of blood delivered to the kidneys per minute, totaling approximately $1,200\,mL/min$ or $25\%$ of cardiac output.

Total Renal Plasma Flow

The volume of plasma delivered to the kidneys, ranging from $600$ to $700\,mL/min$.

Glomerulus

A part of the nephron located in the Bowman capsule that acts as a nonselective filter for plasma substances with molecular weights less than $70,000$ Daltons.

Shield of negativity

A property of the glomerular filtration barrier that repels negatively charged molecules, such as albumin, even if they are small enough to pass through the barrier layers.

Hydrostatic pressure

Pressure resulting from the smaller size of the efferent arteriole relative to the afferent arteriole, which maintains glomerular blood pressure and pushes water out of capillaries.

Oncotic pressure

Pressure regulated by plasma proteins that holds water inside the capillaries.

Renin-Angiotensin-Aldosterone System (RAAS)

A system that regulates blood flow to and within the glomerulus in response to changes in blood pressure and plasma sodium content.

Macula densa cells

Specific cells in the juxtaglomerular apparatus responsible for detecting low blood pressure and low plasma sodium to stimulate renin production.

Angiotensin 2

The active form of angiotensin that causes vasoconstriction, stimulates sodium reabsorption in the proximal convoluted tubule, and triggers the release of aldosterone and ADH.

Aldosterone

A sodium-retaining hormone released by the adrenal cortex that causes sodium reabsorption and potassium excretion in the distal convoluted tubule and collecting duct.

Antidiuretic hormone (ADH)

Also known as vasopressin, a hormone produced by the hypothalamus that stimulates water reabsorption in the collecting duct.

Maximal reabsorptive capacity ($Tm$)

The maximum concentration of a substance that the kidney can reabsorb before the substance begins appearing in the urine.

Renal threshold

The plasma concentration at which active transport stops and a substance begins appearing in the urine, such as $160$ to $180\,mg/dL$ for glucose.

Countercurrent mechanism

A selective reabsorption process that maintains the osmotic gradient of the renal medulla to aid in the concentration of urine.

Bicarbonate ($HCO_3^-$)

An ion filtered by the glomerulus that must be returned to the blood to maintain proper pH, facilitated by the secretion of hydrogen ions.

Clearance Tests

Standard tests used to measure the filtering capacity of the glomeruli by determining the rate at which kidneys remove a substance from the blood.

Creatinine

A waste product of muscle metabolism produced from creatine by creatine phosphokinase, used as a marker for glomerular filtration and renal failure.

Cystatin C

A small protein produced by all nucleated cells that is filtered by the glomerulus and can be used to relate serum concentration directly to $GFR$ without a $24$-hour urine collection.

Beta2-microglobulin ($B2M$)

A marker that dissociates from human leukocyte antigens; increased urinary excretion indicates damaged renal tubules.

Specific Gravity

A screening procedure used to assess tubular reabsorption, influenced by the number and density of particles in the urine.

Fishberg test

A historical test where patients were deprived of fluids for $24$ hours to evaluate the kidney’s ability to concentrate urine to a specific gravity of at least $1.026$.

Osmolality

A measure of the number of particles in a solution used for an accurate evaluation of the renal concentrating ability.

p-amino-hippuric acid (PAH) Test

A test using a nontoxic substance to evaluate tubular secretion and renal blood flow based on its complete removal from the blood in peritubular capillaries.

Renal tubular acidosis

A condition characterized by the inability of the tubules to produce acidic urine even in the presence of metabolic acidosis.