Excretory System and Nephron Anatomy

Comprehensive vocabulary flashcards covering the macroscopic and microscopic anatomy, vascular pathways, tubular structures, physiological mechanisms, and endocrine regulation of the human excretory system and nephron.

Nephron

The microscopic functional unit of the kidney (approximately 1 million per kidney) that carries out filtration, reabsorption, and secretion.

Renal corpuscle

The filtration unit of the nephron composed of the glomerulus and Bowman's capsule.

Glomerulus

A tuft of capillaries where blood is filtered under pressure into Bowman's capsule.

Bowman's capsule

The tubular cup-like sac surrounding the glomerulus that receives filtrate forced out of the blood.

Afferent arteriole

The vascular vessel that brings blood toward and into the glomerulus.

Efferent arteriole

The vascular vessel that carries blood away from and exits the glomerulus.

Peritubular capillary network

The capillary network surrounding the renal tubules that reclaims reabsorbed substances and supplies solutes for secretion.

Cortical nephron

A type of nephron with its renal corpuscle in the cortex and a short loop that reaches only to the base of the renal pyramid.

Juxtamedullary nephron

A type of nephron with its renal corpuscle near the cortex/medulla border and a long loop extending deep into the renal pyramid.

Proximal convoluted tubule (PCT)

The primary site of tubular reabsorption where water, sodium ions ($Na^+$), glucose, and amino acids return to the blood.

Loop of Henle

The U-shaped tubular portion consisting of a descending limb and an ascending limb where precise amounts of water and salts are reabsorbed.

Distal convoluted tubule (DCT)

The coiled tubular segment that continues selective reabsorption and secretion to fine-tune blood composition.

Collecting duct

The tubular structure that receives fluid (urine) from multiple nephrons and delivers it to the renal pelvis.

Renal cortex

The outer region of the kidney that contains the renal corpuscles of all nephrons.

Renal medulla

The inner region of the kidney arranged into renal pyramids containing loops of Henle and collecting ducts.

Renal artery

The major blood vessel that delivers unfiltered blood directly into the kidney.

Renal vein

The major blood vessel that carries cleansed blood away from the kidney.

Ureter

A muscular tube that transports urine from each kidney down to the urinary bladder.

Retroperitoneal

The anatomical position of the kidneys behind the peritoneum, high in the posterior abdominal cavity roughly between T12 and L3.

Urea

The primary nitrogenous metabolic waste product derived from protein breakdown, excreted at approximately $21\,\text{g/day}$.

Creatinine

A nitrogenous waste product filtered from the blood and excreted by the kidneys at a rate of approximately $1.8\,\text{g/day}$.

Uric acid

A nitrogenous waste product resulting from the breakdown and recycling of RNA, excreted at approximately $0.4\,\text{g/day}$.

Filtration

The movement of water, ions, glucose, amino acids, and urea under hydrostatic pressure from the glomerulus into Bowman's capsule.

Reabsorption

The transport of useful substances such as water, glucose, and ions from the renal tubule back into the peritubular capillaries.

Secretion

The active transport of wastes and excess ions (such as $H^+$) from the peritubular capillaries into the nephron tubule.

Excretion formula

The mathematical formula governing renal output: $\text{Excretion} = \text{Filtration} - \text{Reabsorption} + \text{Secretion}$.

Antidiuretic hormone (ADH)

A hormone that increases the water permeability of collecting ducts, conserving water and concentrating urine.

Aldosterone

A hormone that acts on the DCT and collecting duct to stimulate $Na^+$ reabsorption (water follows), raising blood volume and blood pressure.

Atrial natriuretic peptide (ANP)

A hormone that acts opposite to aldosterone, promoting sodium and water excretion to lower blood volume and blood pressure.

Renin

An enzyme released when blood pressure falls that triggers a physiological cascade to elevate blood pressure.