Urinary System Anatomy and Function: Kidneys, Nephrons, and Pathways

Urinary System

Aka The Renal System; Function: regulation of the blood by filtration and production of urine.

Kidney

Filter the blood; one pair (two) located along the posterior wall of the abdominal cavity.

Ureter

Transport urine to bladder.

Bladder

Store urine; contains rugae that allows for expansion.

Urethra

Conveys urine from the body.

Hilum

Concave medial border where blood vessels, nerves, and ureters enter/leave the kidney.

Renal Sinus

Internal space within each kidney; houses renal arteries, renal veins, lymphatic vessels, nerves, renal pelvis, renal calyces.

Renal Cortex

Outer region/layer of the kidney.

Renal Medulla

Inner region/layer of the kidney; darker shade than renal cortex; divided into renal pyramids.

Renal Columns

Extension of renal cortex into the medulla.

Renal Pyramids

Subdivision of medulla created by renal columns; there are approximately 8-15 pyramids/kidney in adults.

Renal Papilla

Tip or apex of renal pyramid; points towards renal sinus.

Corticomedullary Junction

Meeting of cortex and medulla; located at base of pyramid.

Minor Calyx

Funnel shaped space at end of renal papilla; 1 minor calyx for each renal papilla.

Major Calyx

Formed by merger of 2 or more minor calyces; each kidney contains 2-3 major calyces.

Renal Pelvis

Large funnel shaped space formed by merger of all major calyces; collects urine and transports to ureter.

Nephron

The microscopic functional unit of the kidney; both kidneys contain a total of 2.5 million nephrons.

Proximal Convoluted Tubule (PCT)

Small tubule originating from glomerular capsule; functions to reabsorb water, nutrients, and ions from the filtrate.

Nephron Loop (Loop of Henle)

Originates at sharp bend in proximal convoluted tubule; consists of descending limb and ascending limb.

Distal Convoluted Tubule (DCT)

Originates in renal cortex at end of thick ascending limb of loop of Henle; leads to collecting duct.

Collecting Duct

Collects fluid from distal convoluted tubules; runs through medulla towards renal papilla.

Cortical nephron

85% of nephrons; most of nephron lies in the renal cortex; has short loop of Henle.

Juxtamedullary nephrons

Renal corpuscle lies next to corticomedullary junction; have long loops that extend deep into the medulla.

Peritubular capillaries

Capillaries that surround the PCT and DCT in renal cortex.

Vasa recta

Capillaries that surround the Nephron loop in renal medulla.

Renal Artery

Blood supply to kidneys.

Segmental Artery

Branch to superior/inferior regions of kidney.

Interlobar Artery

Flows between adjacent lobes.

Arcuate Artery

Flows along cortico-medullary junction.

Interlobular Artery

Branches off of arcuate artery into the cortex.

Afferent Arteriole

Enters microscopic filtering units of the kidney.

Glomerulus

Location of blood filtration where liquid, ions, and waste leave the blood stream.

Efferent Arterioles

Leave the glomerulus.

Interlobular Vein

Drains blood from peritubular capillaries and vasa recta.

Arcuate Vein

Located along the cortico-medullary junction.

Interlobar Vein

Flows between adjacent lobes.

Renal Vein

Drains blood from the kidneys into the Inferior Vena Cava to return to the heart.

Juxtaglomerular Apparatus

Combination of cells that monitor blood pressure so that urine can accommodate any changes.

Juxtaglomerular Cells

Cells present in the wall of the afferent arteriole.

Macula Densa

Cells present in the wall of the distal convoluted tubule that contain receptors to monitor decreased blood pressure.

Renin

Released by Juxtaglomerular cells, causing a cascade of reactions leading to blood vessel constriction and raising blood pressure.

Transitional Epithelium

Mucosa that accommodates changes in volume.

Urinary Bladder

Expandable muscular sac that serves as a reservoir for urine.

Rugae

Folds in the bladder that allow stretching.

Trigone

Imaginary triangle that connects 2 ureter and 1 urethral openings.

Internal Urethral Sphincter

Smooth muscle, involuntary superior urethral sphincter surrounding the neck of the bladder.

External Urethral Sphincter

Skeletal muscle, voluntary inferior urethral sphincter.

Female Urethra

3-5 cm long, transports urine to outside body.

Male Urethra

18-20 cm long, transports urine and semen to outside body, has 3 regions: Prostatic, Membranous, and Spongy.