Renal anatomy Flashcards
Inner blood supply to kidney
Renal artery -> Interlobar arteries (between medullary pyramids)
- > Arcuate arteries (along cortico-medullary junction)
- > Interlobular arteries (into cortex)
- > Afferent arterioles, glomerular capillaries
Venous drainage the same
- veins thinner walls, larger lumen
Renal cortex
Darker, granular
Dense peritubular capillary network surrounding tubules in any spare space
Renal corpuscle includes glomeruli + Bowman’s capsule
Proximal vs distal convoluted tubules in renal cortex
Proximal tubules - no clear lumen, brush border, dark pink
Distal tubules - wider limen, pale purple (as less mitochondria)
More proximal than distal visible, as more convoluted and longer
Renal medulla
Paler, parallel striations
Collecting ducts lined by columnar epithelium
Descending think limb lined by squamous epithelium
Ascending thick limb of loop of Henle lined by cuboidal epithelium
Vasa recta capillaries contain RBCs
Medullary rays
Medullary tissue that perforates renal cortex
Between interlobular arteries and veins
Contains collecting tubules and loops of Henle
To drain fluid from the most superficial, subcapsular nephrons
(rays reaching into granular tissue)
Renal pelvis
Simple columnar epithelium at papilla
Transitional epithelium at pelvis -> ureter
Ureter histology
Ragged outer connective tissue (torn, as retroperitoneal in extraction)
Longitudinal inner and circular outer smooth muscle
Muscular tube that moves urine by peristalsis
Accomodates lumen size to volume of urine conveyed - transitional epithelium can be relaxed or stretched
Urothelium create watertight boundary, impermeable to water and urine
Transtitional epithelium
Lines renal pelvis, ureter and bladder
3-6 cell layers, stratified
Basal - cuboidal, dividing cells
Intermediate - columnar cells
Surface - umbrella cells, large ovoid cells
Umbrella cells
Large ovoid cells projecting into lumen
Form watertight barrier - luminal membranes are thick, with high lipid content, and desmosomes (fibrils to hold cells together for unified contraction) and tight junctions
Adapted to enable stretch of urothelium - luminal membranes have accordion-like, pleated capability so that cells can lengthen quickly when flow of urine increases and lumen is distended - also allows small calculi (stones) to pass without damaging lining
Bladder histology
Sac-like, expandable store
Propels urine out - no peristalsis but single unified contraction
Outer connective tissue Smooth muscle, elastic fibres Delicate muscularis mucosa Lamina propria Transitional epithelia
Structure of kidney
Superior and inferior poles
Renal hilum has renal vein, renal artery and pelvis (AP)
Lymph drains to para-aortic nodes, lumbar
Function of excretion and electrolyte balance
Capsules of kidney
Fibrous capsule - adherent to kidney surface
Perinephric fat - solid, protective adipose tissue
Renal fascia - extraperitoneal fascia
Pararenal fat
Posterior relations of kidney
Psoas major, transversus abdominus, quadratus lumborum, diaphragm 12th rib (and 11th on left) Subcostal, iliohypogastric, ilioinguinal nerves
Anterior relations of kidney
RIGHT
Adrenal gland, liver, duodenum, right colic flexure
LEFT
Spleen, stomach, jejunum, pancreas, left colic flexure
Adrenal glands relations
Right - posterior to liver
Left - posterior to stomach and pancreas
Lie within coverings of perinephric fat and renal fascia
Adrenal gland structure
Outer cortex and inner medulla
Right is pyramidial, left is semilunar shaped
Supplied by branches from inferior phrenic arteries, aorta and renal arteries
Sympathetic nerves from sympathetic chain to renal plexus, along renal vessels
Afferent sympathetic fibres enter spinal cord at T11-12
Adrenal gland function
Medulla - produce hormones, tyrosine -> adrenaline, noradrenaline, dopamine
Cortex - produce cortisol and aldosterone
Developmental abnormalities in kidney
Polycystic kidneys
Horseshoe kidney - caught on IM vessels
Duplication of ureter - may fuse before bladder or enter bladder separately
Ectopic ureter - opens into urethra or vagina
Pelvic or thoracic kidney
Ureter structure
25cm long muscular tube
Lined with urothelium, transitional epithelium
Retroperitoneal
ABDOMINAL URETER - lies on psoas major
PELVIC URETER - from L4, bifurcation of common iliac artery. Turns anteriorly and medially at ischial spine level. Lies close to seminal vesicle and runs under vas deferens in male, lateral to cervix and under uterine vessles in female
INTRAVESICAL URETER - pierces bladder at angle to prevent backflow of urine, high pressure in bladder collapses ureter
Blood supply and lymph drainage of ureter
Blood supply is from local arteries along its course, venous drainage from corresponding veins - aorta, renal artery, gonadal artery, internal iliac artery, inferior vesical artery
Lymph drains to lumbar nodes
Nerve supply via autonomic plexuses
Surface anatomy of kidneys
T12 to L3
Hilum - left kidney at L1, right kidney at L2 (liver in way, so more likely to feel right), 5cm from midline
Pain
Urinary tract - loin to groin (T12 dermatome)
Kidneys - loin/flank level back pain
Renal colic (calculi) - waves of spasmodic pain as muscle walls try to squeeze down Renal cancer - unremittent, non-radiating
Lumbosacral plexus
Iliohypogastric - L1, together
Ilioinguinal - L1, together
Genitofemoral - L1/2, emerges from psoas
Lateral cutaneous - L2/3, under inguinal ligament to supply lateral thigh
Obturator - L2/3/4, big, deep, to medial thigh
Femoral - to femoral triangle
Bladder
Trigone smooth area
Detrusor smooth muscle wall, rugae when empty
Maximum capacity 500ml
Urachus (obliterated allantois) is attached to apex of bladder, in fold of peritoneum - median umbilical fold, umbilical artery in here
Relations of bladder
Empty - in true pelvis, posterior to pubic symphysis
Male - rectum, vas deferens, seminal vesicle posterior
Female - rectum, uterus posterior
Lateral - ischioanal fossa, obturator internus, levator ani
Superior - sigmoid colon, ileum
Inferior - prostate (male), vagina (female)
Blood and lymph supply to bladder
Superior and inferior vesical arteries from internal iliac artery
Vesical venous plexus drains to internal iliac veins
Lymph drains to internal and external iliac nodes
Innervation to bladder
Sympathetic - from sympathetic trunk
Parasympathetic - pelvic splanchnic nerves, S2-4
Fibres join pelvic (inferior hypogastric) plexus on each side of bladder, then to bladder itself
Female urethra
4cm long
Supported by/embedded in anterior wall of vagina
External urethral meatus opening in folds of labia
Male urethra
15-25cm long
PREPROSTATIC - embedded in bladder neck
PROSTATIC - within prostate, 15-20 prostatic ducts empty into prostatic sinus on each side of urethral crest, openings of ejaculatory ducts on each side
MEMBRANOUS - through external urethral sphincter and perineal membrane
PENILE (SPONGY) - within bulb and corpus spongiosum of penis
Opens at tip of glans of penis
Benign prostatic hyperplasia
BPH
Commonest urinary tract pathology in men
Enlarged prostate obstructs urine outflow, residual urine predisposes to infection, back pressure can lead to hydronephrosis and post renal failure
May be palpable as smooth mass felt on rectal examination
Treat with intermediate catheterisation, alpha blockers, surgery (TURP or radical prostatectomy)
Autonomic fibres controlling continence and micturition
- parasympathetic efferents, motor to detrusor and inhibitory to internal sphincter -> micturition
- parasympathetic afferents convey information about distension, involved in parasympathetic reflex where distension-> emptying - cortical inhibition learned in potty training, micturition becomes voluntary action
- sympathetic efferents are antagonistic and vasomotor, enable continence by inhibiting detrusor contraction and strengthening internal urethral sphincter
External urethral sphincter
Striated muscle controlled by pudendal nerve
Mid-flow stop achieved by contraction of external urethral sphincter and delayed reflex relaxation of detrusor muscle
-> active continence, assisted by pelvic floor (levator ani) contraction
Incontinence
Stress incontinence - weakness of external urinary sphincter and pelvic floor, urination when raised intra-abdominal pressure, common after childbirth
Urge incontinence - overactive detrusor muscle leads to frequent urination, but passing little urine
Overflow incontinence - bladder overexpanded, due to prostatic hypertrophy or loss of communication, when bladder is distended
Urethral catheterisation
To facilitate flow of urine through urethra
Catheter inserted into external urethral meatus and gently advanced
Will angle superiorly in bulb of penis as it pierces perineal membrane above, prostatic urethra curves forward
Balloon inflated once in place
Supra-pubic catheterisation
To drain urinary bladder in patients who cannot be catheterised via urethra, or who need long-term catheterisation
As bladder fills, enters abdomen, and peels peritoneum form lower abdominal wall
Suprapubic catheter therefore does not pierce peritoneum and enter peritoneal cavity
