The kidney and urinary tract Flashcards
What does the urinary system consist of?
kidneys, ureter, bladder and urethra
Where are the kidneys located?
Describe the arrangement of the kidneys relative to eachother
retroperitoneal in the upper abdomen
Right kidney is lower than the left
Describe the structures around the outside of the kidney
Surrounded by dense fibrous capsule
Outside the capsule is the renal fascia containing the peri-renal adipose tissue
Describe what organs are found near the kidneys
- 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
Where does the superior pole of the right and left kidney lie and the hilum?
right - 11th intercostal space
left - 11th rib
hilum - level of L1/ behind second part of duodenum
Blood supply to the kidney - arteries and veins
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
Name some areas in the kidney
Superior and inferior pole Renal artery and vein Renal pelvis Ureter Anterior surface Lateral margin
What is the structure of the kidney?
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
What does the kidney medulla and cortex appear like and why?
Cortex granular-looking because of random organisation
Medulla striated because of radial arrangement of tubules and micro-vessels
Where do the ureters pass through?
- 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
How does the ureter open in the bladder wall and why?
Ureters open obliquely through the bladder wall to prevent backflow
How urine moved down the ureter?
By peristalsis of their smooth muscle walls
What are the three sites of ureteric constriction and their significance?
- pelviureteric junction
- where ureter crosses pelvic brim
- where ureter transverses bladder wall
- constriction are sites of renal colic (pain from kidney stones)
What is the shape of the bladder when empty and full?
empty - pyramid with apex anterior and base posterior
full - round
What is the capacity of the bladder and when does the desire to urinate begin?
450-550 ml
around 150-200 ml
Bladder epithelium
- 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
What is the structure of the bladder?
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
Bladder and urethra in females
Bladder close to vagina wall
Distance from vagina to fixed base of bladder is 6-8mm
Urethra - 4cm
Bladder and urethra in males
- 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
Urethral sphincter
At bottom of urethra there is urethral sphincter (striated muscle) that produces tonic contractions
Urinary sphincters
Sphincter vesicae (internal sphincter) Sphincter urethrae (external sphincter) In women they are close and in men they are far apart
Internal sphincter
- At neck of bladder
- Reflex opening
- In response to bladder wall tension
- Controlled by parasympathetic
- Made of smooth muscle so under involuntary control
External sphincter
- 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
Where is the aorta in relation to the left renal vein?
Behind it - branch supplying kidney comes off aorta as high pressures allow ultrafiltration
Pathway to urine expulsion
- 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
What are the nerves supplying the kidneys?
- 11th intercostal and sub-costal nerves
- oIliohypogastric nerve
- oIlioinguinal nerve
What are some muscles posterior to the kidney?
The diaphragm
Transversus abdominus
Quadratus lumborum
Psoas Major
What are the seven areas of the urethra in men
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
In Prague Men buy penguins named emily
What is the significance of women having shorter urethras than men?
Women have a higher prevalence of STIs
Lymph drainage
Follows arterial supply
Why is the oblique entry of the ureter important?
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
Ureter vessel supply
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
What are four regions of the urethra
- Preprostatic part of urethra
- Prostatic part of urethra
- Membranous part of urethra
- Spongy part of urethra
Where does the urethra open in females?
Passes through perineum to open into the vestibule (space between the labia minora)
Process stimulating urination
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.
Why is urine kept seperate from extracellular fluid?
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.
