2. Renal embryology (Kidney, Bladder, Suprarenal Gland) Flashcards
What is the first structure to produce urine in an early fetus?
The mesonephros
From where is the collecting duct derived?
The collecting duct is derived from the ureteric bud.
Why does a fetus need to have a well-developed suprarenal gland?
Because of the requirement of DHEA to continue the pregnancy
What gives rise to the ureteric bud?
The caudal end of the mesonephric duct
What gives rise to the trigone?
The mesonephric duct growing downwards
What gives rise to the ureter, renal pelvis, and major and minor calyxes?
The ureteric bud
When do we see the appearance of the pronephros?
When do we see it degenerate?
Early week four
It degenerates by day 24 or 25
When do we expect to see the mesonephros producing urine?
From weeks 6 to 10
From where is the nephron derived?
The nephron is derived from the metanephrogenic blastema, which forms metanephric tubules, which become the nephron.
What gives rise to Bowman’s capsule?
The metanephric blastema
What is the pathway of structures leading to the formation of what will become the adult kidney?
(Hint: 5 structures)
Urogenital ridge
Nephrogenic cord
Pronephros
Mesonephros
Metanephros
What is derived from the pelvic part of the urogenital sinus?
The neck of the bladder, as well as:
in males, the prostatic urethra
in females, the entire urethra
What gives rise to the cortex of the suprarenal glands?
Epithelial cells from the intraembryonic coelom
What gives rise to the suprarenal medulla?
Neural crest cells
What forms the efferent ductules in men?
The mesonephric tubules, which produce some urine in early fetal life
What does the intermediate mesoderm form?
kidney and gonads
starts lateral to each somite and forms cylindrical structures
urinary system forms first
First thing to form from the intermediate mesoderm is what?
What does the urogenital ridge form?
urogenital ridge which is a longitudinal band of mesoderm on each side of the dorsal aorta
nephrogenic cord which makes the nephric structures:
- pronephros
- mesonephros
- metanephros
What is the order and function of the nephric structures?
pronephros (rudimentary)
mesonephros (functions in early fetal life)
metanephros (permanent kidneys)
Pronephros appears when?
Pronephros degenerates when?
What does the pronephric duct do?
bilaterally early in 4th week in cervical region
by day 24-25
run caudally and open into cloaca and persist after pronephros degrades to be used by mesonephros
When does the mesonephros appear?
What are the components of the mesonephros?
bilaterally in late 4th week caudal to pronephros
mesonephric ducts and tubules (ducts develop 1st and induce tubules from intermediate mesoderm)
The mesonphric tubules form renal corpuscles which have two components:
- medial end of tubules is cup shaped, glomerular capsule
- tubule wraps around glomerulus (knot of capillaries)
When are the mesonephric tubules functioning?
act as intermittent kidneys from 6-10 weeks, producing small amounts of urine
stop working after ten weeks and will regress in females
form efferent ductules in males
degenerate by 12wks
The metanephros arises when?
during the 5th week, the ureteric bud is induced by the caudal end of each mesonephric duct
the metanephros consists of the ureteric bud and the blastema
What is the ureteric bud?
What is the metanephric blastema?
When do these form a functional and definitive kindey?
outgrowth of mesonephric duct
form nephrogenic cord
9-10th week
will have excretory and collecting portions
How does the ureteric bud morph into the collecting system?
ureteric bud elongates and penetrates the blastema to form the renal pelvis
the stalk of the ureteric bud becomes the ureter
cranial part of the ureteric bud branches into collecting tubules to first make the major calices and then the minor calices
What are the five steps of nephron development?
- collecting tubules induce metanephrogenic blastema to form metanephric vesicles
- Metanephric vesicle will elongate to form metanephric tubules
- proxomal end of tubules will form glomerular capsule and is invaded by glomeruli
- distal end of tubule will lengthen and differentiate into PCT, DCT, and nephron loop
- Each DCT contacts an arched collecting tubule and is now connected!
Explain the blood supply to the kidneys
Kidneys start in pelvis and move up into abdomen
first branch form from common iliacs (will undergo involution and disappear)
definitive renal arteries are from abdomdinal aorta
Unilateral renal agenesis
1:1000, males more affected
typically asymptomatic
suspected in infants with 1 umbilical A.
bilateral renal agenesis
1: 3000
oligohydramnios
non-viable, pulmonary hypoplasia, potter’s sequence
Renal Duplications
abnormal division of ureteric bud
incomplete: divided/bifed kidney
complete: double kidney and bifid ureter or separate ureters
Horseshoe Kidney
1:1000
fusion of inferior poles
asymptomatic
ascent prevented by IMA (what is IMA)
Accessory Renal Vessels
multiple renal arteries (2-4)
25% of adult kidneys affected
2x common as accessory veins
can obstruct ureter and cause hydronephrosis
“end arteries” so if damaged can cause ischemia
Polycystic Kidney Disease
Autosomal recessive mutation in PKHD1
cysts present in both kidneys
renal insuffiency
25% assx with pulmonary hypoplasia
Multicystic dysplastic kidney disease
abnormal development of renal system
cysts are probably dilations in loop of henle
one kidney affected 75% of the time
How is the urogenital sinus formed (the pee hole)
ventral cloaca contains the urogenital sinus and anorectal canal separated by the urorectal septum
- vesicle part: forms most of bladder
- pelvic part: forms neck of bladder, prostatic urethra (m) and urethra (f)
- phallic part: spongy urethra (m), lining of vagina (f)
How is the trigone formed?
at 4-6 weeks, mesonephric duct is incorporated into posterior wall of bladder
ureteric bud is attached then and will connect openings of ureteric buds into bladder wall
openings of mesonephric duct are carried inferiorly to the pelvic urethra
this forms the trigone
What is the trigone?
triangular region of the mesonephric and ureteric ducts blending into posterior bladder
What develops from the vesicle part of the urogenital sinus?
epithelium comes from
submucosa nad muscularis comes from
tigone comes from
bladder!
urogenital sinus
splanchnic mesoderm
intermediate mesoderm
the bladder is continuous with what structure?
what forms the median umbilical ligament?
Allantois
allantois constricts and forms the urachus
extends from the apex of the bladder to the umbilicus
this forms the median umbilical ligament
Exstrophy of the bladder
1:10-40,000, typically males
arises during body folding in 4th wk
defective closure of ventral abdominal wall
exposure of musosa of the posterior wall of the bladder
Epispadias
1:30,000 males
urethral opening is on the dorsum of the genital tubercle rather than on its ventral side
Exostrophy of the bladder with epispadias occurs 1:40,000
- Urachal cysts
- Urachal sinus
- Urachal fistula
- remnants of the epithelial lining of the urachus that can become enlarged and infected
- end of the urachus remains open into bladder or umbilicus
- entire urachus remains patent and allows urine to escape from umbilical orifice
sx: leaking urine or other discharge, peritonitis, infection
remeber the Zones and their hormones of the suprarenal gland?
Medulla:
Salt, Sugar, Sex, the deeper you go the sweeter it gets.
ZG: mineralcorticoids
ZF: glucocorticoids
ZR: sex hormones
Medulla: chromaffin cells (Ne/Epi)
What are the four steps in the development of the suprarenal glands?
- 5ht week, coelomic epithelium delaminates and enters mesoderm making fetal cortical cells
- Neural Crest Cells migrate into medulla and diff. into chromaffin cells. Contain postganglionic sym. neurons (epi/ne)
- Fetal cortex regresses and final cortical cells reorganize into the three zones
- fetal cortex secretes DHEA and is converted to estradiol to maintain pregnancy, along with ACTH and glucocorticoids
