Urinary system microscopic anatomy of the kidneys

Vocabulary flashcards covering key nephron structures, functions, and regulatory mechanisms described in the notes.

Nephron

The structural and functional unit of the kidney; filters blood and forms urine.

Renal corpuscle

The beginning part of the nephron consisting of the glomerulus and Bowman's capsule.

Glomerulus

A tuft of fenestrated capillaries where filtration of blood begins.

Bowman’s capsule (glomerular capsule)

Cup-shaped hollow structure surrounding the glomerulus; has an outer parietal layer and an inner visceral layer.

Podocytes

Visceral layer cells with foot processes that wrap around glomerular capillaries and form filtration slits.

Pedicels

Extensions of podocytes that interlock to create filtration slits.

Afferent arteriole

Blood vessel that delivers blood to the glomerulus for filtration.

Peritubular capillaries

Network surrounding renal tubules involved in reabsorption of filtrate back into blood.

Proximal convoluted tubule (PCT)

First tubular segment in the cortex with cuboidal cells and dense microvilli (brush border) for high reabsorption/secretion.

Brush border

Dense microvilli on PCT cells increasing surface area for reabsorption.

Loop of Henle

U‑shaped tubule with descending and ascending limbs; creates medullary concentration gradient.

Descending limb (loop of Henle)

Part of the loop more permeable to water, contributing to medullary osmolality.

Ascending limb (loop of Henle)

Part of the loop where solutes are reabsorbed; thick vs thin segments have different permeabilities.

Distal convoluted tubule (DCT)

Cortical segment with fewer microvilli; involved in reabsorption and secretion; hormone-regulated.

Collecting duct

Final collecting pathway, not technically part of the nephron; site of water reabsorption via aquaporins, regulated by ADH; drains to the renal papilla.

Aquaporins

Water channel proteins in the collecting duct that enable water reabsorption.

Antidiuretic hormone (ADH) / vasopressin

Hormone that increases water reabsorption in the collecting duct by promoting aquaporin insertion.

Renin‑angiotensin‑aldosterone system (RAS)

Hormonal system that increases sodium reabsorption and blood pressure; renin triggers a cascade leading to aldosterone release.

Atrial natriuretic peptide (ANP)

Hormone that promotes sodium loss (natriuresis) and diuresis, opposing aldosterone.

Juxtaglomerular (JG) cells

Cells in the afferent arteriole that regulate GFR by sensing NaCl and BP; secrete renin.

Tubuloglomerular feedback

Mechanism where the tubule communicates with the glomerulus to adjust GFR based on tubular NaCl delivery.

Glomerular filtration rate (GFR)

Volume of filtrate formed per minute; about 125 mL/min in a healthy adult (~180 L/day total processed by kidneys).

Glomerular hydrostatic pressure

Hydrostatic pressure in glomerular capillaries that promotes filtration.

Capsular hydrostatic pressure

Pressure in Bowman's capsule that opposes filtration.

Glomerular osmotic (colloid) pressure

Osmotic pressure due to plasma proteins in blood opposing filtration.

Filtration barrier

Endothelium, basement membrane, and podocytes with filtration slits that allow selective filtration.

Reabsorption

Selective movement of solutes from renal tubule into the peritubular blood.

Secretion

Movement of solutes from peritubular blood into the renal tubule to be excreted.

Normal urine components

Nitrogenous wastes (urea, uric acid, ammonia, creatinine), electrolytes, toxins, urochromes (pigments), and certain excess hormones.

Renal papilla

Tip of the collecting ducts within a renal pyramid; urine exits toward calyces.

Minor calyx

Structure collecting urine from papillae and draining into a major calyx.

Major calyx

Collects urine from minor calyces and drains into the renal pelvis.

Renal pelvis

Funnel-shaped chamber that collects urine and channels it into the ureter.

Ureter

Tube that transports urine from kidney to bladder via peristaltic contractions.

Urochromes

Yellow pigments in urine from breakdown of red blood cells.