EMBRYOLOGY OF KIDNEY

By: Gan Quan Fu, PT,

MSc Human Anatomy (Batch 3)

Contents

1. Introduction

2. Development of Kidneys

Introduction

Urogenital system developed from:

1. Intermediate mesoderm

2. Cloacal Membrane

Morula

Blastocyst

Two germ layers:1) Ectoderm2) Endoderm

Cavity Appear:Amniotic Cavity

Yolk Sac

Extra-embryonic Mesoderm

Appear

Primitive Streak

Intra-embryonic Mesoderm

Form 3 Subdivision:1) Paraxial2) Intermediate3) Lateral Plate

Ectodermal View

Introduction

After folding of embryonic disc

Intermediate Mesoderm form bulging (Nephrogenic Cord) on posterior abdominal wall.

Structures formed in relation to the nephrogenic cord are:

1. Excretory tubules associated with the development of kidney.

2. The nephric duct which is formed in relation to the developing excretory tubules which becomes mesonephric duct.

3. The paramesonephric duct formed lateral to nephric duct.

4. The gonad(testis and ovary).

Development of Kidney

kidneys arises from 2 distinct sources:

1. Excretory tubules(nephrons)

Derived from the lower part of nephrogenic cord.

Metanephros, the cells of which form the metanephric blastema.

2. Collecting part

Derived from a diverticulum (ureteric bud), arises from the lower part of the mesonephric duct.

3 different kidney system appear in the 4th week of intrauterine life in the nephrogenic cord extending from the cervical to the sacral region:

1. Pronephros

2. Mesonephros

3. Metanephros

Development of Kidney Human PRONEPHROS

First to form, appears in the cervical region

Non-functional and regress completely by the end of 4th week

A nephric duct formed in relation to this persist.

MESONEPHROS

Second to form, consist of a series of excretory tubules that develop in the thoracolumbar region.

These tubules drain into the nephric (mesonephric or Wolffian duct).

Begins to regress after 8 weeks (Most mesonephric tubules disappear but some are modified and take part in forming duct system of testis.)

METANEPHROS

Final formation, in the sacral region

Definitive nephric structure which contributes to the complete formation of adult kidneys and the ureters.

Note that the mesonephric duct opens into the endodermal cloaca

and gives off the ureteric bud.

1. Pronephros and Pronephric duct degenerate soon after formation.

2. Proximal part of mesonephros shows segmentation (in craniocaudal sequence).

3. Segments contain functional excretory tubules that drain into mesonephric duct.

4. Most of these tubules disappear by time the metanephros forms definitive kidney

DEVELOPMENT OF METANEPHROS Last nephric organ to develop.

Definitive kidney and functional with respect to urine production in both fetus and adult.

It arises from 2 separate rudiments:

1. Metanephric blastema

Condensation of mesoderm arises from the caudal portion of the nephrogenic cord and gives rise to excretory components which includes :

1. Bowman’s capsule or Glomerular capsule

2. Proximal convoluted tubule

3. Loop of Henle

4. Distal convoluted tubule

2. Ureteric bud.

DEVELOPMENT OF METANEPHROS

Ureteric bud grows cranially towards metanephric

blastema.

Growing tip of ureteric bud dilated to form an

ampulla.

Ampulla divides repeatedly form Renal Pelvis, Major

and minor calyces.

Collecting tubules formed vary in number (1 to 3

million).

Cells of metanephric blastema undergo

differentiation (Nephrogenesis) to form nephron.

Development of Renal Pelvis

1 . Metanephric mesoderm2 . Ureteric bud

1. Metanephric mesoderm2. Ureteric bud3. Pelvis4. Major calyx

1. Metanephric mesoderm2. Ureteric bud3. Collecting tubules4. Pelvis

Formation of Nephrons

Loosely arranged cells of metanephric blastema form solid clumps in relation to ampulla.

Solid clumps converted into circular metanephric vesicle which soon becomes pear shaped and opens into the ampulla.

Pear shaper metanephric vesicle later becomes “S” shaped tube.

Distal end of the tube is invaginated by capillaries forms glomerulus.

The rest of the tube differentiates into:

Proximal convoluted tubule

Loop of Henle

Distal convoluted tubule

1. Metanephric tissue cups

2. Cell clusters3. Renal vesicle4. Collecting tubule

1. Metanephric tissue cups2. Ampulla3. Collecting tubule4. Metanephric mesoderm

Development of Nephron

1. Nephron2. Bowman's capsule3. Metanephric mesoderm4. Collecting tubule

1. Bowman's capsule2. Distal convoluted tubule3. Collecting tubules

Development of Nephron

1. Distal convoluted tubule2. Glomerulus3. Collecting tubules4. Proximal convoluted tubule5. Henle's loop6. Bowman's capsule

Development of Nephron

Rotation of Kidney

Hilum of Kidney at first face anteriorly

Rotation occurs gradually (90 degrees medially), Hilum face medially.

Ascent of Kidney

Ascent of Kidney

1. Urogenital ridge2. Genital ridge3. Mesonephric duct4. Mesonephros5. Gonad6. Metanephric tissue7. Ureter8. Cloacal membrane9. Cloaca10. Allantois11. Urorectal septum12. Tail

Ascent of Kidney

1. Mesonephric duct2. Mesonephros3. Gonad4. Metanephros5. Ureter6. Cloacal membrane7. Cloaca8. Urorectal septum9. Urogenital sinus10. Anorectal canal11. Tail

Ascent of Kidney

1. Ureter2. Metanephros3. Gonad4. Mesonephric duct5. Anal membrane6. Urogenital membrane7. Perineal body8. Bladder9. Rectum