Urinary System: Key Terms and Structures

Urinary System Overview

The urinary system is responsible for filtering blood, removing waste products, and regulating fluid and electrolyte balance in the body. The following study notes cover essential terms and structures relevant to the anatomy and physiology of the urinary system.

Main Organs and Structures

• Kidney: Bean-shaped organs that filter blood and produce urine.

• Renal artery: Supplies oxygenated blood to the kidneys.

• Renal vein: Drains deoxygenated blood from the kidneys.

• Ureter: Tubes that transport urine from the kidneys to the urinary bladder.

• Urinary bladder: Muscular sac that stores urine until excretion.

• Urethra: Tube that carries urine from the bladder to the outside of the body.

Urethra and Associated Structures

• Prostatic urethra: Portion of the male urethra passing through the prostate gland.

• Intermediate urethra: Also known as the membranous urethra; short segment between the prostate and the penis.

• Spongy urethra: Longest segment of the male urethra, running through the penis.

• Detrusor: Smooth muscle layer of the bladder wall responsible for contraction during urination.

• Trigone: Triangular area in the bladder formed by the openings of the ureters and urethra.

• External urethral sphincter: Voluntary muscle controlling urine flow from the bladder.

• Internal urethral sphincter: Involuntary muscle at the bladder-urethra junction.

Renal Anatomy

• Renal cortex: Outer region of the kidney containing nephrons.

• Renal medulla: Inner region of the kidney composed of renal pyramids.

• Renal pyramid: Cone-shaped tissues in the medulla containing collecting ducts.

• Renal papilla: Tip of the renal pyramid where urine drains into minor calyces.

• Major calyx: Chamber that collects urine from minor calyces.

• Minor calyx: Small chamber that collects urine from renal papillae.

• Renal column: Extensions of cortical tissue between renal pyramids.

• Fibrous capsule: Tough outer covering of the kidney.

Renal Blood Supply

• Segmental artery: Branches of the renal artery supplying different kidney segments.

• Interlobar artery: Vessels running between renal pyramids.

• Arcuate artery: Vessels arching over the base of renal pyramids.

• Cortical radiate artery: Small arteries supplying the renal cortex.

• Afferent arteriole: Vessel bringing blood to the glomerulus.

• Efferent arteriole: Vessel carrying blood away from the glomerulus.

Nephron Structure and Function

The nephron is the functional unit of the kidney, responsible for filtering blood and forming urine.

• Glomerulus: Network of capillaries where filtration of blood occurs.

• Glomerular capsule (Bowman's capsule): Surrounds the glomerulus and collects filtrate.

• PCT (Proximal Convoluted Tubule): First segment of the renal tubule; reabsorbs water, ions, and nutrients.

• DCT (Distal Convoluted Tubule): Last segment of the renal tubule; involved in selective reabsorption and secretion.

• Nephron loop (Loop of Henle): U-shaped part of the nephron; has descending and ascending limbs for water and salt reabsorption.

• Collecting duct: Receives urine from multiple nephrons and transports it to the renal papilla.

• Cortical nephron: Nephrons located primarily in the renal cortex.

• Juxtamedullary nephron: Nephrons with long loops extending deep into the medulla; important for concentrating urine.

• Vasa recta: Capillary network associated with juxtamedullary nephrons; involved in water and solute exchange.

• Peritubular capillaries: Capillaries surrounding the renal tubules; involved in reabsorption and secretion.

• Juxtaglomerular apparatus: Specialized structure regulating blood pressure and filtration rate.

• Podocytes: Specialized cells in the glomerular capsule aiding filtration.

Summary Table: Key Urinary System Structures and Functions

Structure	Location	Function
Kidney	Abdominal cavity	Filters blood, produces urine
Renal artery	Enters kidney	Supplies blood to kidney
Glomerulus	Renal cortex	Filtration of blood
PCT	Renal cortex	Reabsorption of water, ions, nutrients
Loop of Henle	Renal medulla	Concentration of urine
Collecting duct	Renal medulla	Transports urine to papilla
Ureter	From kidney to bladder	Transports urine
Urinary bladder	Pelvic cavity	Stores urine
Urethra	From bladder to exterior	Excretes urine

Additional info:

• The nephron's filtration process is driven by blood pressure in the glomerulus, and the rate of filtration is regulated by the juxtaglomerular apparatus.

• Podocytes form filtration slits in the glomerular capsule, allowing selective passage of substances.

• Juxtamedullary nephrons are crucial for producing concentrated urine, especially during dehydration.