unit 4a - Renal Function

Flashcards covering renal anatomy, physiological functions (filtration, reabsorption, secretion), glomerular filtration rate regulation, and micturition based on lecture notes.

The kidneys process __________ of plasma per day, yet urine output is only approximately $1.5\,L$ per day.

$$180\,L$$

Filtration occurs only in the __________, and once in the tubules, filtrate will be excreted unless reabsorbed.

renal corpuscles

The functional units where all Bowman’s capsules, proximal tubules, and distal tubules are located is the __________.

cortex

The __________ contains the loops of Henle and the collecting ducts.

medulla

In a portal system like that of the nephron, two __________ beds are joined by an arteriole.

capillary

The three barriers to glomerular filtration are the fenestrated endothelium, the basement membrane, and the __________ processes of the specialized epithelium.

podocyte foot

The basement membrane of the glomerular capillary acts as a coarse sieve that keeps most __________ in the plasma, partly due to its negative charge.

proteins

The net driving force for glomerular filtration is low, but the __________ is high (approximately $180\,L/day$) due to the leakiness of the barrier.

glomerular filtration rate (GFR)

Normal GFR is typically maintained at a range of __________.

$$100-125\,ml/min$$

Increasing the resistance of the __________ arteriole causes a decrease in renal blood flow, a decrease in $P_H$, and a decrease in GFR.

afferent

Increasing the resistance of the __________ arteriole causes a decrease in renal blood flow but increases $P_H$ and GFR.

efferent

The intrinsic response of arteriolar smooth muscle to pressure changes is known as the __________ response.

myogenic

In tubulo glomerular feedback, modified tubular epithelium called __________ cells detect NaCl flow and release paracrine factors.

macula densa

Specialized smooth muscle cells in the afferent arteriolar wall, known as __________, secrete the enzyme renin.

granular cells (JG cells)

Approximately __________% of fluid and solute is reabsorbed in the proximal tubule in a process called iso-osmotic reabsorption.

70

The transporter __________ is responsible for moving glucose into the cell against its concentration gradient by coupling it to $Na^+$ moving down its electrochemical gradient.

SGLT (Na+-glucose cotransporter)

Up to __________% of filtered urea is reabsorbed passively in the proximal tubule following the osmotic gradient created by water.

40

The general molecular weight cut-off for protein filtration at the glomerulus is __________.

$$50\,kDa$$

The __________ is the transport rate of a substance when all available membrane carriers are saturated.

Transport maximum (Tm)

The __________ refers to the plasma concentration of a substance at which the Transport maximum ($T_m$) is reached and the substance begins appearing in the urine.

renal threshold

Organic anions are typically secreted across the proximal tubule epithelium via the __________ family of transporters.

OAT (organic anion transporter)

The excretion rate of a substance is calculated as __________ $-$ Reabsorption $+$ Secretion.

Filtration

__________ is defined as the volume of plasma cleared of a substance per minute.

Clearance

The clearance of __________, a plant storage carbohydrate, is equal to GFR because it is neither reabsorbed nor secreted.

inulin

Clinically, GFR is often estimated using the clearance of __________, a breakdown product from muscle phosphocreatine.

creatinine

During the micturition reflex, the __________ nervous system causes the smooth muscle of the bladder to contract.

parasympathetic

The external urethral sphincter is composed of __________ muscle and is kept closed by tonic stimulation from the CNS.

skeletal