congenital defect in which the renal cortex is replaced by numerous cysts in various sizes - [image]no functional renal tissue can be identified

classic type, (less common) hydronephrotic type

From what structure does the urogenital system develop?

What structures do those derivatives give rise to?

Intermediate mesoderm

--> urogenital ridge --> urinary, genital systems

nephrogenic cord (part of urogenital ridge) --> urinary system

the first set of kidneys - rudimentary, nonfunctional, appears in early 4th week, soon degenerates

develop in the cervical intermediate mesoderm; serves as orientation for mesonephric kidney

Mesonephros kidney

how do they begin?

what structures do they form?

what is their function?

what structures do they give rise to?

Second set, appears late 4th wk, function for 4 wks until permanent kidneys develop (end of first 3 months)

begin as nephrogenic cords that extend from 1st thoracic level to upper lumbar region of the embryo

forms urogenital ridges (6th wk) bilaterally that project into abdominal cavity; within each one the mesonephric duct forms (a collecting component of the kidney)

produce urine from 6-10 wks, drain via mesonephric ducts into the cloaca

Male: tubules --> efferent ductules of testes

         ducts --> epididymis, vans deferens, ejaculatory ducts, seminal gland

Female: these structures regress

[image]Metanephros kidney

when/where does it develop?

what structures does the metanephric diverticulum give rise to? what's another name for this structure

[image]

early 5th wk (functional 9th wk), sacral region

MD (aka ureteric bud) --> permanent kidneys

kidneys also form from a metanephric mass of mesoderm (aka metanephric blastema)

The MD is the primordium of the ureter, renal pelvis, calyces, and collecting tubules

  - Stalk of the MD --> ureter

  - cranial end --> renal pelvis

  - collecting tubules divide, --> major calcyes, minor calcyes

How do the nephrons develop?

How does this process begin?

5 steps

what factors are secreted that are essential to this process? What happens if someone is deficient in them?

Collecting tubules secrete factors* that induce the metanephric cap to form the nephrons (renal corpuscles, loops of Henle, PCT, DCT) - beginning of 8th wk

1. lobulation at kidney surface

2. aggregations of metanephric mesenchyme

3. basement membrane forms on outer surface of epithelial cells

4. polarization of cells

5. final functional nephron

basic fibroblast growth factor (FGF-2)

bone morphogenetic protein 7 (BMP-7)

you won't have a nephron w/o these growth factors!

Positional changes of the kidneys

where do the kidneys form?

what changes occur during the ascent of the kidneys?

what structures half the ascent of the kidneys (normally)

kidneys form within the pelvis, anterior to the sacrum, with the hilum positioned anterior

kidneys ascend to their adult position by 9th week/adrenal gland (due to caudal growth), while rotating medially 90 degrees so hilum faces anteromedially

  - kidneys become retroperitoneal

  - ascent can be arrested if they contact the IMA

  - blood supply changes during ascent

form when temporary renal arteries that form during ascent of the kidneys fail to degenerate

25% of adults have 2-4 renal aa (75% have just one)

problematic only if an accessory artery supplies the inferior pole that obstructs a ureter --> hydronephrosis

these are end aa; if damaged, the region they supply becomes ischemic

2x more prevalent than accessory veins

10% of chronic renal failures

usually an acquired developmental defect arising during gestation

Wilm's tumor 1

Potter's syndrome

a defect in this development gene can cause urogenital defects

renal agensis, hypoplastic lungs, neonatal respiratory distress, edema, acidosis, cyanosis

Renal agenesis

unilateral vs. bilateral

unilateral: usually not a problem, other kidney hypertrophies

bilateral: usually deadly; results from failure of development of metanephric diverticula or primorida of the ureters

Caused by failure of one or both kidneys to ascend; most commonly the kidney remains in the pelvis

sometimes assoc with malrotation

crossed renal ectopia - when one kidney crosses to the other side

Discoid (pancake) kidney

Horseshoe kidney

caused by fusion of kidneys within the pelvis

usually formed when inferior poles become fused in pelvis

most common renal fusion

ascent may be stopped by IMA

7% have Turner's syndrome

children at greater risk of developing Wilms tumor

when kidney doesn't develop to normal size

usually unilateral

usually occurs from scarring, not a development failure

true hypoplastic kidney has no scars and reduced number of renal lobes or fewer (< 6)

has two ureters and renal pelves

formed by the incomplete division of the metanephric diverticulum (ureteric bud)

2 forms: autosomal dominant (ADPKD), symptoms in adulthood

             recessive (ARPKD), symptoms in early infancy/childhood

common: 600,000; 4th leading cause of renal failure

ARPKD less common than ADPKD (90%)

In ARPKD both kidneys have hundreds of small cysts (infantile PKD; gene = PKDH1); survival dependent on transplants/dialysis

cysts form by wide dilations of parts of the continuous nephrons, usually the loops of Henle

opens anywhere except posterosuperior bladder (bladder neck, prostatic urethra, vagina, vaginal vestibule)