The kidney and urinary tract

Question 1

What does the urinary system consist of?

Answer 1

kidneys, ureter, bladder and urethra

Question 2

Where are the kidneys located?

Describe the arrangement of the kidneys relative to eachother

Answer 2

retroperitoneal in the upper abdomen

Right kidney is lower than the left

Question 3

Describe the structures around the outside of the kidney

Answer 3

Surrounded by dense fibrous capsule

Outside the capsule is the renal fascia containing the peri-renal adipose tissue

Question 4

Describe what organs are found near the kidneys

Answer 4

• Overlapped posterosuperiorly by diaphragm and pleural cavity
• Spleen above and anterior left kidney
• Anterior to left kidney is the stomach, pancreas and splenic flexure (bend)
• Liver above and anterior to right kidney
• Hepatic flexure is anterior to right kidney
• Suprarenal glands above kidneys

Question 5

Where does the superior pole of the right and left kidney lie and the hilum?

Answer 5

right - 11th intercostal space
left - 11th rib
hilum - level of L1/ behind second part of duodenum

Question 6

Blood supply to the kidney - arteries and veins

Answer 6

Abundant blood supply via renal arteries - short direct branches from abdominal aorta, left renal artery is shorter than the right
Renal veins drain into the IVC - left renal vein is longer than the right

Question 7

Name some areas in the kidney

Answer 7

Superior and inferior pole
Renal artery and vein
Renal pelvis
Ureter
Anterior surface
Lateral margin

Question 8

What is the structure of the kidney?

Answer 8

Multilobar - each lobe drains through its own papilla and calyx
All minor calyx to one major calyx
Each pyramid also receives its own blood supply and ureter branch

Question 9

What does the kidney medulla and cortex appear like and why?

Answer 9

Cortex granular-looking because of random organisation

Medulla striated because of radial arrangement of tubules and micro-vessels

Question 10

Where do the ureters pass through?

Answer 10

• Run vertically down posterior abdominal wall in the vertical plane of the tips of the transverse processes of the lumbar vertebrae
• Cross the pelvic brim (edge of pelvic inlet) anterior to the sacro-iliac joint & bifurcation of the common iliac arteries
• Descend anteromedially to enter bladder at the level of the ischial spine

Question 11

How does the ureter open in the bladder wall and why?

Answer 11

Ureters open obliquely through the bladder wall to prevent backflow

Question 12

How urine moved down the ureter?

Answer 12

By peristalsis of their smooth muscle walls

Question 13

What are the three sites of ureteric constriction and their significance?

Answer 13

• pelviureteric junction
• where ureter crosses pelvic brim
• where ureter transverses bladder wall
• constriction are sites of renal colic (pain from kidney stones)

Question 14

What is the shape of the bladder when empty and full?

Answer 14

empty - pyramid with apex anterior and base posterior

full - round

Question 15

What is the capacity of the bladder and when does the desire to urinate begin?

Answer 15

450-550 ml

around 150-200 ml

Question 16

Bladder epithelium

Answer 16

• Lined by urothelium (transitional epithelium)
• 3-layered epithelium with slow cell turn over
• Urothelium acts as barrier to stop waste products leaking back into body
• Large luminal cells have highly specialized low-permeability luminal membrane
• This prevents dissipation of urine-plasma gradients

Question 17

What is the structure of the bladder?

Answer 17

There is a superior area, the inferolateral area, the apex, the fundus (base), the neck the urethra, trigone, median umbilical ligament, internal urethral orifice and sphincters

Question 18

Bladder and urethra in females

Answer 18

Bladder close to vagina wall
Distance from vagina to fixed base of bladder is 6-8mm
Urethra - 4cm

Question 19

Bladder and urethra in males

Answer 19

• Longer urethra – 12-14cm
• Men have to generate more pressure to void as longer urethra means more urethral resistance
• Narrower than female urethra
• Men have separate control between internal and external sphincter
• Sphincters stop ejaculate going into bladder during ejaculation

Question 20

Urethral sphincter

Answer 20

At bottom of urethra there is urethral sphincter (striated muscle) that produces tonic contractions

Question 21

Urinary sphincters

Answer 21

Sphincter vesicae (internal sphincter)
Sphincter urethrae (external sphincter)
In women they are close and in men they are far apart

Question 22

Internal sphincter

Answer 22

• At neck of bladder
• Reflex opening
• In response to bladder wall tension
• Controlled by parasympathetic
• Made of smooth muscle so under involuntary control

Question 23

External sphincter

Answer 23

• In perineum
• At bladder’s distal inferior end in females
• Inferior to prostate in males
• Tone maintained by somatic nerves in pudendal nerve (S2,3,4)
• Opened by voluntary inhibition of nerves
• Sustained closure keeps internal sphincter closed and reduces bladder tone
• Made of skeletal muscle so under voluntary control

Question 24

Where is the aorta in relation to the left renal vein?

Answer 24

Behind it - branch supplying kidney comes off aorta as high pressures allow ultrafiltration

Question 25

Pathway to urine expulsion

Answer 25

• Stretch receptors send impulses to motor neurons controlling external sphincter, inhibiting them and to the parasympathetic nerves as the bladder fills
• The parasympathetic nerve causes the bladder to contract and the internal urethral sphincter opens
• The inhibition of the motor neurone opens the external sphincter and urine can be expelled

Question 26

What are the nerves supplying the kidneys?

Answer 26

• 11th intercostal and sub-costal nerves
• oIliohypogastric nerve
• oIlioinguinal nerve

Question 27

What are some muscles posterior to the kidney?

Answer 27

The diaphragm
Transversus abdominus
Quadratus lumborum
Psoas Major

Question 28

What are the seven areas of the urethra in men

Answer 28

1) Internal urethral orifice – bladder neck, bladder outlet
2) Prostatic urethra
3) Membranous urethra
4) Bulbar urethra
5) Penile urethra
6) Navicular fossa
7) External urethral meatus

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Question 29

What is the significance of women having shorter urethras than men?

Answer 29

Women have a higher prevalence of STIs

Question 30

Lymph drainage

Answer 30

Follows arterial supply

Question 31

Why is the oblique entry of the ureter important?

Answer 31

As ureter runs obliquely in, as the bladder swells (due to corrugated internal membrane), the ureters are pushed back and function as a self-shutting valve

Question 32

Ureter vessel supply

Answer 32

The ureters take supplies from all major vessels in the abdomen:

• A renal arterial branch
• A testicular or ovarian arterial branch
• Small direct branches of the aorta itself
• External and internal iliac arterial branches

Question 33

What are four regions of the urethra

Answer 33

• Preprostatic part of urethra
• Prostatic part of urethra
• Membranous part of urethra
• Spongy part of urethra

Question 34

Where does the urethra open in females?

Answer 34

Passes through perineum to open into the vestibule (space between the labia minora)

Question 35

Process stimulating urination

Answer 35

Beyond a level of fulless, the tension in the bladder wall increases, stimulating receptors that trigger a sacral parasympathetic reflex leading to contraction of the smooth muscle in the bladder wall and relaxation of the smooth muscle sphincter (sphincter vesicae) at the junction of bladder and urethra. Sensory afferents make an individual aware of bladder fullness. A decision to empty the bladder (micturate) leads to voluntary relaxation of the skeletal muscle sphincter (sphincter urethrae) that surrounds the urethra in the perineum, via descending inhibitory pathways that reduce the pudendal nerve induced constriction of the sphincter. In the absence of a decision to empty the bladder, the urethral sphincter stays closed and this leads to closure of vesical sphincter and reduction of bladder tone.

Question 36

Why is urine kept seperate from extracellular fluid?

Answer 36

Urine is often very hypertonic or hypotonic, so osmotic and

diffusive processes between urine and extracellular fluid would undo much of what the kidneys have achieved.