Embryo! Flashcards
Main contributor to kidney formation?
intermediate mesoderm/ urogenital mesoderm
- will divide into two regions: gonadal ridge (forms repro system), and nephrogenic ridge (forms urinary system)
- nephrogenic ridge extends throughout the body
gut tube ends in the cloaca
What are the three kidney stages?
- Pronephros: forms in thorax: gone by week 4
- Mesonephros: lower thoracic/upper lumbar region
- interim kidney until month 3
- mesonephric tubules develop and drain to mesonephric duct (Wolffian Duct)
- Mesonephric duct drains to cloaca
- Metanephros (permanent kidney)
- functional at end of 3rd month
- Two parts: metanephric blastema and ureteric bud
What are the two parts of the metanephros? what do they form?
Metanephric blastema: forms nephrons
- bowman’s capsule
- PCT
- Loops of Henle
- DCTs
Ureteric Bud: forms duct system
- an evagination of mesonephric duct, that penetrates the metanephric bastema
- CT’s
- minor/major calyces
- renal pelvis
- ureter
Kidneys form in the pelvis… How do the ascend?
- occurs week 6-9
- kidneys form in pelvis: and rotate about 90 degrees medially so that in the abdomen the hilum region faces anteriomedially
- normally when an organ migrates, they take their original innervation with them
but as the kidneys ascend they receive new lymphatics/nerves/vessels
- original supply is from common iliac aa…. but in adult they receive blood from renal aa. and the branches of the aorta
How does Urinary bladder and urethra form? What does urogenital sinus form?
- both form from the Cloaca: Cloaca must be divided by urorectal septum to divide the cloca into anterior (urogenital sinus) and posterior (analrectal canal)
Urogenital sinus:
- Cranial (vesical) portion: forms bladder; continuous with allantois ( allantois becomes the urachus which will form the median umbilical region)
- Middle (pelvic) region: forms **urethra in females and prostatic/membranous urethra in males **
- Caudal (phallic) portion: males only, forms penile urethra
Accessory renal arteries
- most common : 25% of population
Cause: arise from persistence of caudal renal aa. during devleopment - lower vessels don’t regress
Usually asymptomatic, in some cases can compress ureter and cause hydronephrosis (back up of urine)
- in this case - the aa. need to be surgically transposed, either anterior or posterior to the ureter
Renal Hypoplasia
underdevelopment of kidney
cause: inadequate branching of ureteric bud and lack of differentiation of nephrons
Functional nephrons are present, but are very limited
Persistent fetal lobulation is a type of renal hypoplasia
Renal dysplasia
a cystic disease: present at birth
- entire nephrons are replaced with fluid filled cysts
i. e. multicystic dysplastic kidney
Autosomal cystic kdiney disease
- cystic disease that is also congenital: cysts are wide dilations of parts of the nephrons
- results in unfunctional kidney
Autosomal recessive: cysts form from collecting ducts; renal insufficiency
Autosomal dominant: cysts form from collecting ducts and nephron
Renal Agenesis
Cause: ureteric bud fails to form and / or doesn’t induce differentiation of the metanephric blastema
- can be unilateral (individual is fine)
- if bilateral, results in potter’s sequence
Potter’s sequence (step-by-step progression….)
Primary cuase- resulting from bilateral renal agenesis:
- renal agenesis results in oligohydramnios due to fetus not producing urine
Oligohydramnios: results in….LL: lungs and limbs
- hypoplastic lungs
- Potter facies: broad, flat nose; wide-set eyes, low-set ears
- Limb malformation (club foot)
Horseshoe kidney
- asymptomatic
- inferior poles of kidneys fuse while it is in pelvis - when kidney starts to ascend it is stuck by the mesenteric aa. andn it is thus stuck in the pelvis
completely functional, just located in a different place
Ectopic (pelvic) kidneys
- asymptomatic: functional kidney
- kidney fails to ascend: reults in pelvic kidney
Wilm’s tumor
- most common malignant tumor of kidneys in children: usually presents before age 5
- due to mutation in WT1 gene: transcription factor expressed in metanephric blastema
- metanephric blastema stays undifferentiated, but is rapidly dividing
- often also results in malformation of gonad (seen in Denys-Drash syndrome)
WAGR syndrom: both WT1 and PAX6 genes are mutated]
- W:wilms tumor
- A: Aniridia: no iris in eye
- G: gonadal malformation
- R: mental retardation
Duplication of ureter
Cause: splitting of ureteric bud - resulting in Y shaped ureter
- can sometimes lead to duplication of kidney as well
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