Urinary system

• Urinary system


  Functions:

  • Filtration of arterial blood in the form of urine
  • Regulation of blood: pH, pressure, volume
  • Regulation of electrolytes

  
• Urinary system contains


  • Kidneys

  Ureters

  Bladder

  Urethra

  
• Kidneys


  • Located on the posterior abdominal wall

  Level of location: from T12 to L3

  Lower ribs partially support kidneys

  Right kidney is slightly lower than the left due to the liver present superiorly

  
• Structures surrounding the kidneys

  • Posteriorly: abdominal muscles (internal oblique muscle + transverse abdominus)

  Superiorly: Suprarenal/adrenal glands

  Anterior to right kidney: part of transverse colon + part of ascending colon + pancreas

  Anterior to left kidney: transverse part of stomach + transverse colon + part of descending colon + pancreas + spleen

  
• External outline of the kidney

  • Darker in colour

  
• Pathway of urine


  Bowman's capsule -> proximal convoluted tubule -> descending loop of Henle -> ascending loop of Henle -> distal convoluted tubule -> collecting duct -> renal papilla -> Minor Calyx -> major Calyx -> renal pelvis -> ureter -> Urinary bladder

  
• Nephron


  • Functional unit of the kidneys

  Kidneys filtrate arterial blood from the descending aorta

  Abdominal aorta gives renal arteries which take blood towards kidneys for filtration

  Renal artery enters the kidney medially through the hilum of the kidney

  Arterioles enter the bowman's capsule and release excess fluids, wastes etc.

  Filtered blood will transport oxygen to the tissues of the kidney

  
• Pathway of blood for filtration

  • Renal artery -> renal hilum -> renal pyramids -> Cortex -> Nephron

  
• Vessels in the kidney

  • Segmental arteries

  Interlobar arteries

  Arcuate arteries

  Interlobular arteries

  Afferent arterioles

  Efferent arterioles

  
• Glomerulus


  • Formed by the interconnection of afferent and efferent arterioles inside the Bowman's capsule
• Pathway of filtrates (urine)

  Bowman's capsule -> proximal convoluted tubule -> descending loop of Henle -> ascending loop of Henle -> distal convoluted tubule -> collecting duct -> renal papilla

  
• Juxtamedullary Nephrons


  Loop of Henle is longer and closer to the renal papilla
• Cortical Nephrons


  Loop of Henle is shorter and closer to the renal cortex
• Ureters


  • Long, fibromuscular tubes that transport urine from the kidneys to the urinary bladder

  Constrictions: 1) Narrowed tube at the ureteropelvic junction, 2) Curved, narrowed ureter as it opens into the urinary bladder to prevent regurgitation, 3) Additional structures (e.g. Vessels) running over ureters help compress them

  
• Urinary Bladder


  • Muscular structure located in the pelvic cavity

  Upside down pyramidal shape

  Superior part: base, Inferior part: apex

  Posterior part is immoveable (Trigone) with 2 ureteral openings and 1 urethral opening

  When full, can be directly palpated posterior to the public symphysis

  In females, the uterus is found posterior-superiorly to the bladder. In males, digestive system structures are found superiorly to the bladder, and the prostate gland is inferior to the bladder.

  
• Urethra


  • Drains urine from the body

  In females, opens into external genitalia (posterior opening: Vagina)

  In males, part of the urethra is surrounded by the prostate gland (prostatic urethra). The reproductive and urinary systems are interconnected in males.

  
• Parts of male urethra

  • Prostatic urethra

  Pelvic urethra

  Penile urethra

  
• The urinary system regulates electrolytes, blood pressure, blood volume, and removes metabolic wastes