Urinary System Key Terms: Structure & Functions

Collecting Duct

A tube that collects urine from several nephrons and carries it to the renal pelvis

Distal Convoluted Tubule

The last part of a nephron through which urine flows before reaching the collecting duct

Glomerulus

A cluster of capillaries around the end of a renal corpuscle

Nephron

The excretory unit of each kidney

Nephron Loop

The U shaped part of a nephron that is between the proximal convoluted tubule and the distal convoluted tubule; has a descending limb and an ascending limb; also called the Loop of Henle

Proximal Convoluted Tubule

The part of the nephron between the glomerular capsule and the nephron loop; minerals, nutrients, and water are reabsorbed from the filtrate here

Renal Corpuscle

The part of a nephron that consists of a glomerular capsule with its included glomerulus

Renal Cortex

The lighter-colored, outer layer of the kidney that contains the glomeruli and convoluted tubules

Renal Medulla

The darker, innermost part of the kidney

Renal Pelvis

A funnel-shaped cavity in the center of the kidney where urine collects before it flows into the ureter

Renal Tubule

The part of a nephron that leads away from a glomerulus and empties into a collecting tubule; consists of a proximal convoluted tubule, nephron loop, and distal convoluted tubule

Urinary System

The organs involved in the formation, storage, and excretion of urine; includes the kidneys, ureters, bladder, and urethra

Aldosterone

A steroid hormone produced in the adrenal cortex that regulates salt and water balance in the body by increasing the amount of sodium reabsorbed from urine

Angiotensin

A polypeptide hormone in the blood that constricts blood vessels and increases blood pressure

ADH Antidiuretic Hormone

A peptide hormone secreted by the pituitary gland that constricts blood vessels, raises blood pressure and reduces excretion of urine; vasopressin

ANP Atrial Natriuretic Peptide

A peptide hormone secreted by the atria of the heart that promotes excretion of sodium and water and lowers blood pressure

Diuresis

Urine excretion

External Urethral Sphincter

A ring of skeletal muscle that surrounds the intermediate part of the urethra where it passes through the urogenital diaphragm; this muscle is voluntarily controlled during release of urine from the body

GFR Glomerular Filtration Rate

The total amount of water filtered from the glomerular capillaries into the glomerular capsule per unit of time; usually measured in mLs per minute

Hydrostatic Pressure

The pressure exerted by a liquid as a result of its potential energy

Internal Urethral Sphincter

A layer of smooth muscle located at the inferior end of the bladder and the proximal end of the urethra; this muscle, which prohibits release of urine, is under involuntary control

Micturition

Urination

Osmosis

The movement of water molecules from a region of low osmotic pressure to a region of high osmotic pressure

Osmotic Pressure

A pressure created by the presence of dissolved substances in water

Reabsorption

The movement of water and dissolved substances from the filtrate (in a renal tubule) back into the blood

Renin

An enzyme made and secreted by the kidneys; aids in the production of angiotensin

Secretion

The active movement of substance from the blood into the filtrate, which will become urine

Ureter

A duct through which urine travels from the kidney to the bladder

Urethra

A thin tube that connects the urinary bladder to the outside environment

Urinary Bladder

A hollow, muscular organ that stores urine