Embryology Flashcards
What germ layer do the kidneys originate from?
Mesoderm
When do the pronephros form?
In the 4th week of gestation
Where do the pronephros form?
Cervical region
What part of the pronephros persists?
Duct
How many mesonephros are produced and in what direction?
40 tubules produced craniocaudally
When do the mesonephros regress?
By the end of the 5th week of gestation
When the mesonephros regress, what is left and what do they do?
Leave 20 pairs (L1-L3):
- Differentiate in excretory units
- > Function weeks 6-10 then regress
When do the metanephros appear?
~5 weeks gestation
When do the metanephros begin to function?
~9-11 weeks gestation
What do the metanephros form?
The permanent kidney
What two structures form the metanephros and where do they originate from?
Ureteric bud:
- Protrusion from mesonephric duct
Metanephric blastama:
-From the mesonephric duct
In regards to the metanephros, when do the ureteric buds sprout and where from?
Day 28 of gestation
From distal mesonephric ducts
In regards to the metanephros, when does the metanephric blastema sprout and where from?
Day 32 of gestation
Ureteric buds penetrate sacral intermediate mesoderm
What is the process of development from the ureteric bud?
Ureteric bud -> Ureter -> Renal pelvis -> Major calyces -> Minor calyces -> Collecting ducts
What part of development of the ureteric bud is a dichotomous division?
Renal pelvis -> Major calyces
What does the metanephric blastema form?
Metanephric blastema -> Metanephric cap -> Metanephric vesicle -> Bowman’s capsule:
- > PCT - > Loop of Henle - > DCT
Where do the kidneys initially develop? When do they reach their end position?
In pelvis
Reach end position by week 9
In what direction do the hila of the kidneys point during weeks 5 and 6?
Anteriorly (in pelvis)
When do the kidneys reach the abdomen and what direction do the hila face then?
~Week 7
Hila face medially
What happens to the kidneys as the embryo grows caudally?
Kidneys start to lie:
- Retoperitoneally - At L1 level
How can the general blood supply of the kidney be described?
By closest aortic branches
What vessels initially supply the kidney?
Median sacral nerve and temporary aortic branches
What happens to the temporary aortic branches when kidney reaches final position?
Tend to regress (can persist -> Accessory renal arteries)
What is a pelvic kidney?
When one kidney fails to ascend
What is the process by which a horseshoe kidney forms?
Inferior poles of metanephroi meet and fuse before ascent:
- Trapped beneath inferior mesenteric artery
What is the cloaca?
Hindgut endoderm
What forms the cloaca?
Rectum
Primitive urogenital sinus:
- Bladder
- Pelvic urethra
- Definitive urogenital sinusWhere do the mesonephric ducts incorporate into and what do they form?
Into posterior bladder wall
Form:
- Epididymis
- Vas deferens
- Seminal vesicleWhat is the urachus?
The closed remnant of the allantois, a duct between the bladder and the yolk sac
What is a urachal sinus?
Urachal lumen persists at upper part:
- Opens at umbilicus
What is a urachal fistula?
Urachal lumen persists along entire length:
- One end open in the bladder
- One end open at umbilicus
- > Urine discharged through umbilicus
What is a urachal cyst?
Small part of lumen remains patent:
- Each end closed
-> Forming median umbilical ligament
Secretory activity of epithelium remains active:
- Cystic dilatation
What is the normal remnant of the urachus?
Median umbilical ligament
