1. The Urinary System Flashcards
Describe the location of the kidneys (also in comparison to other organs)
- Posteriorly between ribs 11 & 12
- Embedded in retroperitoneal fat
- Liver is superior to the right kidney
- Spleen is superior to the left kidney
- Liver slightly pushes the right kidney inferiorly - not on identical plane to left kidney
- Upper part of each kidney rests on diaphragm
- Suprarenal/adrenal gland superior to each kidney
Where do you feel kidney pain?
- Pain referred via iliohypogastric and ilioinguinal nerve
* Pain is posterior and travels antero-inferiorly towards the groin
Outline the kidney arterial and venous blood supply
• Arterial
- renal arteries branch from abdominal aorta (posterior to left renal vein)
- Short and wide - good blood supply at high pressure
• Venous - renal veins drain into IVC
Describe the structure of the kidneys
- Surrounded by dense fibrous capsule, middle adipose capsule, superficial renal fascia
- Superior and inferior pole
- Medulla - striated, cone-shaped pyramids, base faces cortex, apex (renal papilla) points towards renal hilium
- Cortex - granular, extends from renal capsule to bases of renal pyramid, forms renal columns between each pyramid
- Renal lobe = renal pyramid, overlying renal cortex, 1/2 of each adjacent renal column
- Cortex - glomeruli, convoluted tubules
- Medulla - loops of Henle (creating striated appearance)
- Urine drains into papillary ducts
- Papillary ducts drain into minor calyces (one papilla to one minor calyx)
- Minor calyces drain into major calyces
- Major calyces drain into renal pelvis => ureter
Which part of the kidney is the most vulnerable to death following trauma and why?
- Renal papilla
- Last to receive blood supply (arcuate arteries - glomerulus => Loop of Henle => renal papilla)
- Polyuria still occurs after blood transfusion as renal papilla are involved in concentrating urine
Describe the anatomy of the ureters (macro and micro)
• Run vertically down posterior abdominal wall
• Lie across the transverse spinal processes on each side of the vertebral column
• Renal colic caused by kidney stones at specific junctions:
- ureteropelvic junction (between renal pelvis + ureter)
- segment near sacroiliac joint
- ureterovesical junctions (between ureter + bladder)
• Open obliquely through bladder wall - valve
- Urothelium with tight gap junctions + plaques preventing leakage
- Folded walls - stretching possible
- 3-layered epithelium with slow cell turnover
- Highly specialised low-permeability luminal membrane - prevents dissipation of urine-plasma gradients
How is urine transported through the ureter?
- Peristalsis
* Circular and longitudinal smooth muscle
What is vesicoureteral reflux?
- Abnormal movement of urine from bladder into ureter
- Urine collects in renal pelvis - drips back down
- Incomplete micturition (emptying)
- Can cause infection
Describe the structure and function of the bladder
- Pyramidal vessel when empty, more spherical when full
- Capacity of 450-550ml
- Voids 120-250ml in each go (should not contract between voids)
- Fundus (base), superior and inferolateral bladder sections
- Median umbilical ligament at apex of bladder (remnant of umbilical cord)
Describe the function of the sphincters and the urethra
• Internal and external smooth muscle sphincters - striated muscle produces tonic contractions to prevent uncontrolled urination
• Internal sphincter (sphincter vesicae)
- involuntary parasympathetic control
- continuation of detrusor muscle (ACh synaptic control)
- reflex opening in response to bladder wall tension involving ACh (loss of control can be treated with anticholinergics)
• External sphincter (sphincter urethrae)
- in perineum
- opened by voluntary inhibition of somatic pudendal nerve (S2, 3, 4)
- sustained closure keeps the sphincter vesicae closed
• In males, the sphincters lie on either side of the prostatic urethra
- urethra is longer
- reduced pressure
- more effort to void the bladder
- internal sphincter prevents retrograde ejaculation
