Urinary system anatomy Flashcards
What is the gross anatomy of the urinary system?
Kidneys, ureters, urinary bladder, urethra.
What are ureters?
Muscular tubes transporting urine from kidneys to the bladder; continuous with the renal pelvis – formed by condensation of 2/3 major calices.
What is the uteropelvic junction?
Narrowing of the renal pelvis where it becomes continuous with the ureter.
What is the course of the ureters?
Descend retroperitoneally on the medial aspect of the Psoas major (tips of the transverse processes of the lumbar vertebrae) to the pelvic brim where they cross anterior to the sacro-iliac joint and region where common iliac arteries bifurcate. In the pelvic cavity, they enter the bladder (at the level of the ischial spine).
How Is urine transported down ureters?
Peristalsis of smooth muscle walls.
What are the constrictions along the ureter? (x3)
- Uteropelvic junction. 2. Point of crossing the common iliac vessels to the pelvic brim. 3. Entrance to the bladder.
What is the relevance of ureteral constrictions in pain?
Constrictions are sites of renal colic (type of referred pain) caused by KIDNEY STONES attempting to pass.
What is the vasculature of the urinary system? (x3 arteries)
Renal arteries, abdominal aorta, internal iliac arteries all branch to supply.
How is the urinary system innervated? (x3) What are the afferents/efferents?
Renal, aortic and superior/inferior hypogastric plexuses all innervate (visceral efferents from both SNS and PSNS sources – visceral afferents return to T11-12 leading to referred pain in those dermatomes e.g. posterolateral abdominal wall pain).
What is the anatomical positioning of the bladder?
Most anterior element of the pelvic viscera.
How is the bladder lined? Purpose?
Lined by urothelium (3-layered membrane with slow cell turnover and large, impermeable luminal cells). PURPOSE: prevents dissipation of urine-plasma gradients.
What makes the urothelium adapted as an impermeable barrier? (x2)
Strong tight junctions that stop paracellular diffusion. Highly keratinised cell membrane surface synthesised from high numbers of Golgi apparatus.
What does urothelium look like histologically?
Characteristic rounded epithelial cells.
What is the structure of the bladder?
Bladder is a triangular pyramid with the apex pointing anteriorly.
APEX: directed towards the top of the pubic symphysis and attached to the umbilical ligament.
BASE: inverted triangle and points posteriorly. Ureters enter at upper corners with the urethra draining inferiorly from the lower corner of the base.
INFERIOR: mucosal lining is smooth and firmly attached to underlying tissue.
TRIGONE: smooth area between the openings of the ureters and urethra.
INFEROLATERAL SURFACES: cradled by pelvic muscles.
How is the urethra anchored in place?
Neck of the bladder anchored in position by tough fibromuscular bands connecting neck of the urethra to the posteroinferior aspect of each pubic bone.
How do the ligamentous attachments of the urethra differ between males and females?
MALES: called PUBOPROSTATIC LIGAMENTS – blend with fibrous capsule of the prostate which surrounds the neck of the bladder. FEMALES: called PUBOVESICAL LIGAMENTS – supported by peritoneum and associated muscles.
How is bladder sphincter opening controlled?
Bladder filling activates sensory PSNS stretch fibres, leading to S2-4 motor neurones to signal detrusor muscle to cause contraction and open internal sphincter. This is a REFLEX action meaning it cannot be controlled consciously. Opened (sphincter relaxes) by PSNS and closed (contraction) due to SNS.
What are the lymphatics of the urinary system? (x2)
Iliac nodes, with ureter draining to para-aortic nodes.
How does the urethra differ between males and females?
MEN: longer, passes inferiorly through the prostate through the deep perineal pouch and perineal membrane and enter the root of the penis.
WOMEN: shorter, travelling inferiorly through the pelvic floor and deep perineal pouch/membrane to open into the vestibule between the labia minora. Small Skene’s (mucous) glands are also associated with the lower end.
What are the divisions of the male urethra?
Divided to preprostatic, prostatic, membranous and spongy parts. There’s also penile and bulbar.
What is the navicular fossa?
Part of the male urethra.
What are the kidneys surrounded by?
Surrounded by dense fibrous capsule. Outside this is a fascial pouch (renal fascia) containing peri-renal adipose tissue.
Paranephric fat surrounds this. Note also that the transversalis fascia (green, thick line) separates the abdomen from the posterior muscles, and the parietal peritoneum is anterior to the kidneys (making the kidneys retroperitoneal).
What is in contact with the kidneys posteriorly?
(Moving medial to lateral): MUSCLES: Psoas major, quadratus lumborum, transversus abdominis. VESSELS: subcostal vessels, ilio-inguinal nerves and ilio-hypogastric nerves also pass posteriorly.
What ribs do the apexes of each kidney lie behind?
LEFT: 11th rib. RIGHT: 11th ICS.
What is the internal structure of the kidney?
HILUM: deep vertical slit through which the renal vessels, lymphatics and nerves enter/leave (continuous internally with the renal sinus).
RENAL SINUS:
RENAL CORTEX: granular-looking outer layer of the kidney – continuous band of place tissue, with projections called renal columns into the inner aspect to divide the medulla to discontinuous aggregations. Random arrangement gives granular appearance.
RENAL MEDULLA: pyramid shaped regions of the kidneys where nephrons are present (tubules and micro-vessels make medulla look striated).
RENAL PAPILLA: each lobe drains through its own papilla and calyx.
MINOR CALLICES: apical projections of the renal pyramids.
MAJOR CALYX: unity of several minor calices – multiple major calices unite to form the renal pelvis.
Renal pyramids are the collecting ducts/regions of the kidneys.
They drain via renal papilla (???) into minor, then major calyces which all drain into the renal pelvis and ureter.
What is the vasculature of the kidneys?
RENAL ARTERIES: lateral branches of the abdominal aorta that supply each kidney; arise inferior of the superior mesenteric artery origin at L2/L3, with the left renal artery shorter and higher.
HILIUM: the renal arteries divide to anterior and posterior branches to supply the parenchyma.
RENAL VEINS: are formed by multiple smaller veins, and run anterior to the arteries. Left renal vein crosses anterior to the aorta but posterior to the superior mesenteric artery, and can be compressed by aneurysms in either vessel.
What does the cortex look like histologically?
Has mostly thick walls, take up more stain, there are more circular cross sections of renal corpuscles containing glomeruli.
Each glomeruli has a vascular pole where the blood vessels enter and leave the glomerulus, and a urinary pole where the filtrate drains into the proximal convoluted tubule.
You will also see thick-walled tubules which indicate the distal and proximal CTs.
How are collecting ducts identified histologically?
Found in the cortex and passing down into the medulla. They have a pale stain and obvious cell-cell boundaries because cell-cell boundaries do NOT INTERDIGITATE. Simple cuboidal epithelium, two layers of smooth muscle for peristalsis, little active pumping so few mitochondria.
How is the medulla identified histologically?
Mass of tubular structures of different sizes and thicknesses, with the majority orientated radially (arranged like rays). More lightly stained.
What does the cross-section of the ureter look like?
Two-layered smooth muscle wall – aligned longitudinally and circularly for peristalsis. Layers of connective tissue with blood vessels. Transitional epithelium is another name for urothelium.
