Urinary tract Flashcards
Which part of the abdomen are the kidneys located in?
The posterior retroperitoneal lumbar regions
What level do they extend from and to (left and right)?
T11/12 to L2/3
The right kidney is often situated slightly lower due to the presence of the liver. Right at (T12) in the abdomen and the left at (T11). Each kidney is approximately three vertebrae in length.
How far does the kidney hilum sit from the body midline?
5cm
What two features protect the kidneys?
The kidneys are surrounded by a thick layer of peri-nephric fat and the upper parts are protected by the 11th and 12th ribs.
What organs lie anterior to the left kidney?
Spleen, stomach, pancreas, jejunum
What organs lie anterior to the right kidney?
Liver, duodenum
What are the four layers of fascia and fat surrounding kidney from deep to superficial?
Renal capsule: tough fibrous capsule.
Perirenal fat: collection of extraperitoneal fat.
Renal fascia (also known as Gerota’s fascia or perirenal fascia): encloses the kidneys and the suprarenal glands
Pararenal fat: mainly located on the posterolateral aspect of the kidney.
What two regions can the renal parenchyma be divided into?
Renal cortex and inner renal medulla
What forms renal pyramids?
The cortex extends into the medulla, dividing it into triangular shapes – these are known as renal pyramids.
What is the name of the apex of the renal pyramid?
Renal papilla
What joins from the renal papilla that drains the renal pyramid?
The minor calyx
What do several minor calices form?
Major calyx
What do the the major calices drain into?
Renal pelvis
From the renal pelvis, where does fluid drain?
Ureter
What enters/leaves at the renal hilum?
Renal vessels and ureter
What vessels supply the kidneys?
Renal arteries, which arise directly from the abdominal aorta
What level do the renal arteries leave the aorta?
Immediately below superior mesenteric arteries L1-L3
Which renal artery is longer, why?
Due to the anatomical position of the abdominal aorta (slightly to the left of the midline), the right renal artery is longer
How does the right renal artery cross the vena cava?
Posteriorly
Are there anastomoses of the renal artery?
No, the renal artery branches are anatomical end arteries
What becomes of the renal artery at the hilum level?
At the hilum level, the renal artery forms an anterior and a posterior division
What proportion of the blood is in the posterior and anterior division of the renal artery?
75% anterior and 25% posterior
What do the anterior and posterior divisions of renal arteries divide into?
5 segmental branches
What do the 5 segmental arteries divide into?
Interlobar arteries
Where are interlobar arteries positioned?
Either side of each renal pyramid
What do interLOBAR arteries divide into?
Arcuate arteries
What do the arcuate arteries give rise to at 90 degrees?
Interlobular arteries
What do the interLOBULAR arteries divide into
Afferent arterioles
What happens to the afferent arterioles?
They converge to form a capillary network (glomerulus) and efferent arterioles
What arteries supply the outer 2/3 of cortex nephron?
Efferent arterioles form a peritubular network, supplying the nephron tubules
What region is the peritubular network in?
Outer 2/3 of the cortex
What supplies nephron in the the inner 1/3 of cortex and medulla
Vasa recta
What drains the blood from kidneys?
Right and left renal veins
Which renal vein is longer, why?
As the vena cava lies slightly to the right, the left renal vein is longer.
How does the left renal vein pass over aorta?
Anteriorly
How many ureters are there?
Two
How long are the ureters?
~25cm
What is the name of the point at which the renal pelvis narrows to form the ureter?
Ureteropelvic junction
Initially what is the course of the ureters?
Retroperitoneal, along the anterior surface of the psoas major
Once in the pelvis, at what level to the ureters move towards the bladder, what direction is this?
Anteromedially, at the ischial spines
What prevents back-flow of urine?
Ureter enters bladder obliquely, creating a one way valve, high intramural pressure collapses ureter (bladder wall acts as sphincter)
How does the ureter force urine into the bladder?
Smooth muscle peristaltic movement
What is the abdominal arterial supply to the ureter?
Renal artery, testicular/ovarian artery, and ureteral branches directly from the abdominal aorta
What is the pelvic arterial supply to the ureter?
Superior and inferior vesical arteries
What gives the nervous supply to the ureter?
Renal, testicular/ovarian and hypogastric plexuses.
Sensory fibres from the ureters enter the spinal cord at T11-L2.
What are the two roles of the bladder?
Temporary storage of urine
Assists in the expulsion of urine
What feature of the bladder wall allows it to expand?
It has a folded internal lining (known as rugae), which allows it to accommodate up to 400-600ml of urine in healthy adults.
What is the base of the bladder described as and what forms it?
The trigone, formed by entry of ureters, thickened tissue and opening of urethra
What differentiates the trigone from the rest of the internal bladder, why is it different?
Trigone has smooth walls (this is explained by the different embryological origin: the trigone is developed by the integration of two mesonephric ducts at the base of the bladder).
What forms the bladder wall?
Smooth detrusor muscle
What lines the inside of the bladder?
Transitional epithelium
How does the muscle in the bladder wall maintain structural integrity?
Fibres oriented in multiple directions
Describe the sympathetic innervation of detrusor muscle, and what it causes
Sympathetic hypogastric nerve (T12 – L2) causes relaxation of the detrusor muscle, promoting urine retention.
Describe the parasympathetic innervation of detrusor muscle, and what it causes
Pelvic nerve (S2-S4). Increased signals from this nerve causes contraction of the detrusor muscle, stimulating micturition.
Describe the somatic innervation of the external urethral sphincter
Pudendal nerve (S2-4). It innervates the external urethral sphincter, providing voluntary control over micturition.
What muscle is controlled somatically to allow urination
External urethral sphincter
Before somatic control is gained what controls urination?
The bladder stretch reflex
Describe the bladder stretch reflex
Bladder fills with urine, and the bladder walls stretch.
Sensory nerves detect stretch and transmit this information to the spinal cord.
Interneurons within the spinal cord relay the signal to the parasympathetic efferents (the pelvic nerve).
The pelvic nerve acts to contract the detrusor muscle, and stimulate micturition.
What is the arterial supply to the bladder?
Arterial supply is via the superior vesical branch of the internal iliac artery.
In males, this is supplemented by the inferior vesical artery.
Females by the vaginal arteries.
In both sexes, the obturator and inferior gluteal arteries may also contribute small branches.
What is the bladder venous drainage?
Venous drainage is achieved by the vesical venous plexus, which empties into the internal iliac veins.
Describe the female urethra
Short, and anchored to the anterior vaginal wall.
Describe the male urethra
Below the bladder is the prostatic part, surrounded by the prostate gland and also the site of the opening of the ejaculatory and prostatic ducts.
There is a short membranous part which passes through the perineal membrane and then the long penile part.
The penile part is surrounded by the erectile tissues of the corpus spongiosum
Describe the role of the internal urethral sphincter in females
Functional sphincter (i.e. no sphincteric muscle present). It is formed by the anatomy of the bladder neck and proximal urethra.
Describe the role of the internal urethral sphincter in males
Consists of circular smooth fibres, which are under autonomic control. It is thought to prevent seminal regurgitation during ejaculation.
Is the external urethral sphincter the same in both sexes?
Yes
How does level of visceral afferent firing reveal the state of the bladder?
High firing rate - full bladder
Low firing rate - empty bladder
What is the main difference between micturition in an adult and an infant?
Stimulation of interneurons
Adults: transmit sensation to thalamus and cerebral cortex, when time is right pudendal nerve signal to trigger urination.
Infants: interneurons relay the signal to the parasympathetic efferents (the pelvic nerve), urination is subconscious.
What receptor promotes contraction of detrusor muscle when activated?
M3
Why are infants unable to voluntarily controlurination?
Corticospinal connections have not yet been established.
What is a drug useful for overactive bladder, what is its side effects?
Oxybutynin, M3 blocker
Can cause dry mouth and constipation
Which structure lies over the hilum of the right kidney?
Descending part of the duodenum
Are the kidneys secondarily retroperitoneal?
No, primarily
Where can a catheter be inserted straight into the bladder?
Above the pubic bone
Where does the urethra attach firmly to?
Anterior vaginal wall
In the hilus or the kidney, which is anterior to posterior order of structures?
Vein, artery, renal pelvis
Where is the external sphincter (male)?
Just below prostatic part
What surrounds the penile urethra?
Corpus spongiosum
What type of epithelium lines the prostatic urethra?
Urothelium (transitional epithelium)
What control is the internal urethral sphincter mainly under?
Sympathetic
