Urinary system anatomy

Question 1

What is the gross anatomy of the urinary system?

Answer 1

Kidneys, ureters, urinary bladder, urethra.

Question 2

What are ureters?

Answer 2

Muscular tubes transporting urine from kidneys to the bladder; continuous with the renal pelvis – formed by condensation of 2/3 major calices.

Question 3

What is the uteropelvic junction?

Answer 3

Narrowing of the renal pelvis where it becomes continuous with the ureter.

Question 4

What is the course of the ureters?

Answer 4

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).

Question 5

How Is urine transported down ureters?

Answer 5

Peristalsis of smooth muscle walls.

Question 6

What are the constrictions along the ureter? (x3)

Answer 6

1. Uteropelvic junction. 2. Point of crossing the common iliac vessels to the pelvic brim. 3. Entrance to the bladder.

Question 7

What is the relevance of ureteral constrictions in pain?

Answer 7

Constrictions are sites of renal colic (type of referred pain) caused by KIDNEY STONES attempting to pass.

Question 8

What is the vasculature of the urinary system? (x3 arteries)

Answer 8

Renal arteries, abdominal aorta, internal iliac arteries all branch to supply.

Question 9

How is the urinary system innervated? (x3) What are the afferents/efferents?

Answer 9

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).

Question 10

What is the anatomical positioning of the bladder?

Answer 10

Most anterior element of the pelvic viscera.

Question 11

How is the bladder lined? Purpose?

Answer 11

Lined by urothelium (3-layered membrane with slow cell turnover and large, impermeable luminal cells). PURPOSE: prevents dissipation of urine-plasma gradients.

Question 12

What makes the urothelium adapted as an impermeable barrier? (x2)

Answer 12

Strong tight junctions that stop paracellular diffusion. Highly keratinised cell membrane surface synthesised from high numbers of Golgi apparatus.

Question 13

What does urothelium look like histologically?

Answer 13

Characteristic rounded epithelial cells.

Question 14

What is the structure of the bladder?

Answer 14

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.

Question 15

How is the urethra anchored in place?

Answer 15

Neck of the bladder anchored in position by tough fibromuscular bands connecting neck of the urethra to the posteroinferior aspect of each pubic bone.

Question 16

How do the ligamentous attachments of the urethra differ between males and females?

Answer 16

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.

Question 17

How is bladder sphincter opening controlled?

Answer 17

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.

Question 18

What are the lymphatics of the urinary system? (x2)

Answer 18

Iliac nodes, with ureter draining to para-aortic nodes.

Question 19

What are the two urinary sphincters? Overall purpose of them?

Answer 19

S. URETHRAE and S. VESICAE. Purpose = maintain urinary continence.

Question 20

Where is the sphincter vesicae found? Structure? Function?

Answer 20

Internal smooth muscle sphincter at the neck of the bladder that opens reflexively in response to bladder wall tension. The orifice is called the internal urethral orifice.

Question 21

Where is the sphincter urethrae found? Structure? Function?

Answer 21

External striated muscle sphincter in the perineum, whose tone is maintained by somatic nerves in the pudendal nerve (S2-4), opened by voluntary nervous inhibition.

Question 22

How does the urethra differ between males and females?

Answer 22

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.

Question 23

What are the divisions of the male urethra?

Answer 23

Divided to preprostatic, prostatic, membranous and spongy parts. There’s also penile and bulbar.

Question 24

What is the navicular fossa?

Answer 24

Part of the male urethra.

Question 25

What is the relative anatomy of the kidneys?

Answer 25

Retroperitoneally in the upper and posterior abdomen.

Question 26

What are the kidneys surrounded by?

Answer 26

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).

Question 27

What are the suprarenal glands?

Answer 27

Enclosed within renal fascia also, and separated by a thin septum, with the fused layer connecting with the transversalis fascia on the lateral abdominal wall.

Question 28

What lies immediately superior to the kidneys?

Answer 28

Spleen (on the left) and the diaphragm.

Question 29

What is in contact with the kidneys posteriorly?

Answer 29

(Moving medial to lateral): MUSCLES: Psoas major, quadratus lumborum, transversus abdominis. VESSELS: subcostal vessels, ilio-inguinal nerves and ilio-hypogastric nerves also pass posteriorly.

Question 30

What ribs do the apexes of each kidney lie behind?

Answer 30

LEFT: 11th rib. RIGHT: 11th ICS.

Question 31

Where do the hilum of each kidney lie?

Answer 31

L1.

Question 32

What are the anterior relations of the kidneys?

Answer 32

RIGHT: liver, hepatic flexure. LEFT: stomach, pancreas, spleen and splenic flexure.

Question 33

What is the internal structure of the kidney?

Answer 33

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.

Question 34

What is the vasculature of the kidneys?

Answer 34

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.

Question 35

What are the lymphatics of the kidneys?

Answer 35

Lateral aortic (lumbar) nodes at the origins of the renal arteries.

Question 36

What are the branches of the renal arteries called? (x2)

Answer 36

Interlobar arteries within the columns. These form acruate arteries which form anastomoses with their neighbours to supply the nephrons.

Question 37

Is the aorta on the left or the right of the vena cava at the level of the kidneys?

Answer 37

Aorta is left.

Question 38

How does the cortex and medulla differ histologically from the NAKED EYE?

Answer 38

Cortex is external and DARK STAINING; medulla is lighter.

Question 39

What does the cortex look like histologically?

Answer 39

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.

Question 40

Where do podocytes originate in the renal corpuscle?

Answer 40

Develop from the visceral layer of the Bowman’s capsule.

Question 41

What is the renal corpuscle?

Answer 41

Comprises of the Bowman’s capsule, glomerulus and urinary and vascular poles.

Question 42

Where does the glomerular filtrate filter into in the Bowman’s capsule? What is this space surrounded by?

Answer 42

Glomerular space. Surrounded by outer parietal layer of Bowman’s capsule which is simple squamous epithelium.

Question 43

How are collecting ducts identified histologically?

Answer 43

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.

Question 44

How is the medulla identified histologically?

Answer 44

Mass of tubular structures of different sizes and thicknesses, with the majority orientated radially (arranged like rays). More lightly stained.

Question 45

What does the cross-section of the ureter look like?

Answer 45

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.

Question 46

What does the cross-section of the bladder look like?

Answer 46

THREE-LAYERED smooth muscle aka the detrusor – three obliquely orientated layers. Layers of connective tissue with blood vessels.