The Urinary System: Anatomy, Function, and Blood Supply

THE URINARY SYSTEM Functions ● Filtration of blood and elimination of metabolic waste - Harmful waste is excreted through urine ● Regulate blood volume and blood pressure - Secretion of hormone that controls vasocontraction of blood vessels (angiotensin 2) - Retaining or secreting water as needed ● Stimulates production of RBC - Secretion of erythropoietin is a hormone that controls RBC production in bone marrow - Secretions associated with the organs in the urinary system affect RBC (not direct impact) ● Acid/base balance - Eliminating and preserving hydrogen and bicarbonate ● Clears hormones and drugs - Filtering the blood of unwanted drugs and hormones Kidneys ● Origin is in the abdominal cavity (outside of the pelvic cavity) ● Attached to the posterior abdominal wall ● Extend from T12 to L3 ● Rib 12 crosses the top of the kidneys ● Right kidney is slightly lower than the left (liver takes up space on the right) ● Suprarenal adrenal glands secrete adrenaline for the fight or flight response ● Posterior surface is not covered with peritoneum, so they are retroperitoneal Location with relation to the ribs Retroperitoneal External features ● Bean shaped ● Dark maroon colour ● Superior pole with suprarenal glands ● Inferior pole (R is lower) ● Hilum associated with blood supply to the organs (medially facing) ○ Ureters remove the urine produced by the kidneys and take it to the bladder ○ Renal artery ○ Renal vein ○ Renal pelvis (posterior) ● Not surgically resectable --> cannot remove organs of the kidney and still function normally, needs all of its segments to function Connective tissue protective layers Internal features (Lateral to medial) ● Outer renal cortex ○ ○ ● ● Deep maroon colour Has the majority of the blood vessels (more blood vessels = the darker that it is in colour) Middle renal medulla ○ **Renal columns (they are extensions of the renal cortex which pass through the medulla) which bring the blood vessels towards the hilum and towards the other medial section of the kidney ○ Pyramids have the tubules that bring the urine produced at the base of the pyramid ■ Apex is near the hilum ■ Base is closer to the renal cortex Inner renal pelvis ○ Calyx means chalice (small cups to collect the urine that comes through the tubules) ○ The major calyx is next to the apex of the pyramids ○ 2-3 minor calyx empty into a major calyx ○ All of the major calyxes go to the renal pelvis, where it will exit the kidneys via the ureters Blood supply Renal arteries ● Comes from the first major bilateral branches of the abdominal aorta (there are minor branches that supply to the diaphragm) ● Brings oxygenated arterial blood to the kidneys ● L and R ● Comes off the abdominal aorta inferior to the mesenteric artery Renal veins ● Drains into the inferior vena cava (R of abdominal aorta) ● Posterior to the arteries (anatomical position) Nephrons (functional units of the kidney) ● Renal artery and vein join at the base of the renal pyramid (nephron) ● Nephron acts like the tertiary bronchi of the lung ● Blood vessels wrap around the nephron = transfer of nutrients and waste ● Waste goes into the minor calyx and then continue to be excreted Ureters ● Paired muscular tubes ● Connect kidney to the urinary bladder inn the true pelvis ● Continuous with the renal pelvis of the kidneys ● 25cm long ● Comprised of smooth muscle and transports the urine to the urinary bladder ● Retroperitoneal (because the kidneys are also retroperitoneal) ● Can be easily obstructed (if urine has crystallised) 1. Where the renal pelvis narrows into the ureter 2. Passes bony marking because it has intra abdominal organs on top pushing the bones into the pelvis 3. Narrows to insert into the muscle of the urinary bladder ● ● Urine not crystallised = no blockage Compression/change of direction can block the tubes