Embriologi Ginjal

dr. Rohmania Setiarini

O The nephrogenic cord develops into three sets of nephric structures: the pronephros, mesonephros, and metanephros.

O3 embryonic kidneys (from intermediate mesoderm)- O Pronephros- transient (week 3-5),

nonfunctional, 5-7 paired segments.

Pronephros

Develops by the differentiation of mesoderm within the nephrogenic cord to form pronephric tubules and the pronephric duct.*

Pronephros

The pronephros is the cranialmost nephric structure and is a transitory structure that regresses completely by week 5.

The pronephros is not functional in humans.

O Mesonephros- transient (week 4- month 4), excretory organ while metanephros begins development. O Formation of nephric ducts/wolffian

ducts precedes development of mesonephric tubules.

O Small number of elements from mesonephros persist to form reproductive tract.

O Males- efferent ductules of testes, epididymis and vas- wolfian origin.

O Females- nonfunctional mesosalpingeal structures.

Mesonephros

Mesonephros

Develops by differentiation of mesoderm within the nephrogenic cord to form mesonephric tubules and the mesonephric duct (wolffian duct).*

Mesonephros Most of the mesonephric tubules regress, but the

mesonephric duct persists and opens into the urogenital sinus. *

The mesonephros is functional for a short period.

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Develops from an outgrowth of the mesonephric duct (called the ureteric bud) and from a condensation of mesoderm within the nephrogenic cord called the metanephric mesoderm.

Metanephros

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O Metanephros- definitive kidneysO Form as ureteric buds (from distal end of nephric

duct)O Penetrates metanephric mesenchyme at 28 days to

begin nephron formation- lobulated appearance.O Metanephric mesoderm forms nephron or excretory

unit (glomerulus, proximal tubule, loop of Henle, distal tubule)- form from metanephric mesenchyme.

O Older nephrons on inner part of kidney, newer at periphery.

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The metanephros begins to form at week 5 and is functional in the fetus at about week 10.

It develops into the definitive adult kidney.

Metanephros

The fetal kidney is divided into lobes in contrast to the definitive adult kidney, which has a smooth contour.

Metanephros

Two Systems:*

Development of the Metanephros

Collecting System* Excretory (Nephron)

System*

Development of the Collecting System

The ureteric bud initially penetrates the metanephric mesoderm, and then undergoes repeated branching to form the ureters, renal pelvis, major calyces, minor calyces, and collecting ducts.

Development of the Collecting System

The ureteric bud initially penetrates the metanephric mesoderm, and then undergoes repeated branching to form the ureters, renal pelvis, major calyces, minor calyces, and collecting ducts.

Development of the Excretory System The inductive influence of the collecting ducts

causes the metanephric mesoderm to differentiate into metanephric vesicles which later give rise to primitive S-shaped renal tubules, which arecritical to nephron formation.

Development of the Excretory System

The S-shaped renal tubules differentiate into the distal convoluted tubule, loop of Henle, proximal convoluted tubule, and Bowman's capsule.

Development of the Excretory System

Tufts of capillaries called glomeruli protrude into Bowman's capsule.

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Development of the Excretory System

Nephron formation is complete at birth, but functional maturation of nephrons continues throughout infancy.

Ascent of the Kidneys The fetal metanephros is located at vertebral level

S1-S2, whereas the definitive adult kidney is located at vertebral level T12-L3.

The change in location results from a disproportionate growth of the embryo caudal to the metanephros.

Ascent of the Kidneys

During the ascent, the kidneys rotate 90°causing the hilum, which initially faces ventrally, to finally face medially.

Blood Supply of the Kidneys

During the ascent of the kidneys, the kidneys receive their blood supply from arteries at progressively higher levels until the definitive renal arteries develop at L2.

Arteries formed during the ascent may persist and are called supernumerary arteries.

Supernumerary arteries are end arteries. Therefore, any damage to them results in necrosis of kidney parenchyma.

Congenital Malformations

O Renal agenesisO UnilateralO Bilateral

O Renal hypoplasiaO Congenital cystic kidneys

O Types 1 -5O Horseshoe (fused) kidneysO Wilms tumor

Renal AgenesisO Absence of kidneys

O Unilateral (compatible with life)O Affects 1 in every 800-1500 peopleO May occasionally present with genitalia anomoliesO Trisomy of 18O Addition or partial trisomy of 13O Prenatal rubella infection

O Bilateral (incompatible with life)O 40% stillborn O Of those born alive 95% die within 24 hours of birthO Potter syndrome and associated oligohydramnios

Renal agenesis occurs when the ureteric bud fails to develop, thereby eliminating the induction of metanephric vesicles and nephron formation.

Renal Agenesis Unilateral renal agenesis is more common in males.

This situation is asymptomatic and compatible with life because the remaining kidney hypertrophies.

Bilateral Renal Agenesis

Causes oligohydramnios, which results in compression of the fetus, Potter syndrome, (deformed limbs, wrinkly skin, abnormal facial appearance [flattened nose, wide interpupillary space low set ears] and tapering fingers).

Infants with bilateral renal agenesis are usually stillborn or die shortly after birth.

Renal hypoplasiaO Incomplete development of kidneys

O Unilateral (compatible with life)O Bilateral (incompatible with life) if

condition is severeO Kidneys are small

O Decreased functional parenchyma

Congenital cystic kidneys

O Type 1O Polycystic kidneys found in infants

O Bilateral and results in early deathO Large renal pelvis and calyces

O Type 2O Cysts are variable in size and shapeO Usually unilateralO Affected kidney non functional

Congenital cystic kidneys (cont.)

O Type 3O Affected kidneys contain both normal

and abnormal tissueO Both kidneys involvedO Autosomal dominant gene

O Trisomy of 13-15, 18, 21, 22O Type 4

O Caused by urethral obstructionO If severe early death

O Type 5O Manifests during adult life, death by 50.O Autosomal dominant

Horseshoe (fused) kidney

O Fusion of two kidneys at their lower endO Tissue that connects kidneys =

isthmusO 1:400O Trisomy 13-15; 18, 21, Turner’s

syndrome, mosaicism

Renal Fusion

The most common type of renal fusion is the horseshoe kidney.

Renal Fusion A horseshoe kidney occurs when the inferior poles of

the kidneys fuse across the midline.

Normal ascent of the kidneys is arrested because the fused portion gets trapped beneath the inferior mesenteric artery.

Kidney rotation is also arrested so that the hilum faces ventrally.

Wilms TumorO Renal tumor of childrenO Characterized by rapid growth and

early metastasisO Mesodermal origin

O Metanephric tissue that have failed to differentiate into normal kidney tissue

Embryonic developmentO Urinary system, internal

reproductive organs and external genitaliaO Develop synchronously

at an early embryologic age(table 5.6)