HESI A2 - Urinary System - Key Terms and Concepts

Urinary system

The organ system that filters the blood to create urine and removes metabolic waste from the body. It is made up of two (2) kidneys, two (2) ureters, one (1) bladder, and one (1) urethra.

Excretion

The process of removing metabolic waste products and excess substances from the body.

Homeostasis

The maintenance of stable internal conditions, including fluid and electrolyte balance.

Electrolyte balance

The regulation of minerals like sodium, potassium, and calcium in body fluids.

Acid-base balance

The regulation of hydrogen ion concentration to maintain proper pH levels in the body.

Osmoregulation

The control of water and solute concentrations in the body to maintain fluid balance.

Filtration

The process by which blood plasma is filtered in the kidneys to remove waste and excess substances.

Reabsorption

The process in which valuable substances are returned from the kidney filtrate back into the bloodstream.

Secretion

The movement of additional waste substances from the blood into the kidney tubules for excretion.

Urine formation

The three-step process of filtration, reabsorption, and secretion that results in the production of urine.

Kidneys

The paired organs that filter blood, regulate fluid balance, and produce urine.

Renal medulla

The inner region of the kidney containing structures involved in urine concentration.

Renal pyramids

Cone-shaped tissues in the kidney medulla that transport urine to the renal pelvis.

Renal pelvis

The funnel-shaped structure in the kidney that collects urine before it enters the ureter.

Urinary bladder

The muscular organ that stores urine until it is excreted.

Detrusor muscle

The smooth muscle in the bladder wall that contracts to expel urine.

Urinary sphincters

The muscles that control the release of urine from the bladder.

Renal cortex

The kidney's outermost layer, where filtration takes place.

Ureters

Narrow tubes that transport urine from each kidney to the urinary bladder.

Urethra

The passageway that allows urine to exit the bladder and leave the body.

Nephron

The microscopic functional unit of the kidney that filters blood and produces urine.

Glomerulus

A network of capillaries within the nephron where blood filtration begins.

Bowman’s capsule

The cup-shaped structure that surrounds the glomerulus and collects filtrate.

Proximal convoluted tubule

The first segment of the nephron tubule where most reabsorption occurs.

Loop of Henle

A curved section of the nephron that plays a crucial role in concentrating urine by managing water and salt levels.

Descending limb of the Loop of Henle

The part of the nephron loop where water is reabsorbed.

Ascending limb of the Loop of Henle

Water-retaining part of the nephron loop that aids in diluting the filtrate as salts like sodium and chloride are reabsorbed into the circulation.

Distal convoluted tubule

The nephron segment where further ion exchange and water balance occur.

Collecting duct

A channel in the kidney that gathers fluid from several nephrons and delivers it to the renal pelvis as urine.

Peritubular capillaries

The blood vessels surrounding the nephron tubules that allow reabsorption and secretion.

Glomerular filtration rate

The volume of fluid filtered by the kidneys per minute.

Tubular reabsorption

The process of reclaiming essential substances from the nephron filtrate.

Tubular secretion

The active transport of waste and excess substances from the blood into the nephron for elimination.

Urea

A nitrogenous waste product formed from protein metabolism and excreted in urine.

Creatinine

A waste product from muscle metabolism that is excreted by the kidneys.

Uric acid

A waste product that is eliminated by urine and is created during the metabolism of nucleic acids.

Electrolytes

Minerals in the blood and urine that help regulate body functions.

Renin

An enzyme secreted by the kidneys that helps regulate blood pressure.

Aldosterone

A hormone that increases sodium and water reabsorption to regulate blood pressure.

Antidiuretic hormone

A hormone that controls water retention in the kidneys.

Diuresis

Increased urine production due to high fluid intake or certain medications.

Oliguria

A condition marked by a significantly reduced output of urine.

Anuria

A condition where urine output is almost completely absent.

Polyuria

The excessive production of urine, often associated with diabetes.

Hematuria

When blood appears in the urine, this frequently indicates renal or urinary tract issues.

Proteinuria

The presence of abnormal amounts of protein in the urine, often a sign of kidney disease.

Glycosuria

The presence of glucose in the urine, commonly associated with diabetes.

Urinary tract infection

A bacterial infection affecting the urinary system, causing pain and frequent urination.

Dialysis

A medical treatment that performs the filtering functions of the kidneys when they are no longer able to do so effectively.

Kidney stones

Hard mineral deposits that form in the kidneys and can cause significant pain.

Nephrons

Functional units of the kidney, each containing a glomerulus and renal tubule, with 1 to 1.5 million per kidney.

Renal tubule

It comprises the proximal convoluted tubule (PCT), Loop of Henle, and distal convoluted tubule (DCT), which is involved in reabsorption and secretion.

Renal artery

Supplies blood to the kidneys for filtration.

Glomerular filtration

The process where blood is filtered in the glomerulus, allowing water and small solutes to enter the Bowman's capsule while blocking larger molecules.

Urine

It is a liquid byproduct released from the body through urination.

Parathyroid hormone (PTH)

A hormone that maintains serum calcium levels by enhancing calcium reabsorption and promoting phosphate excretion in the kidneys.

Pathway of urine formation in the nephron

Glomerulus → Proximal Convoluted Tubule→ Descending Loop of Henle → Ascending Loop of Henle → Distal Convoluted Tubule → Collecting Duct

Physiological steps of urine formation

1. Glomerular Filtration

2. Tubular Reabsorption

3. Tubular Secretion