Test 1 (Renal Embryology, Dr. Cole) Flashcards
Intermediate Mesoderm
- Urinary (and genital) system develops from Intermediate Mesoderm of TRILAMINAR DISC
- Intermediate Mesoderm separated from later and Paraxial Mesoderm during Folding
**NEPHROGENIC Cord (Nephrons) + UROGENITAL Ridge (Kidneys and Gonads) gives rise to Urogenital System!!!
Nephrongenic Cord
1) Pronephric System:
- Segmented Intermediate Mesoderm
2) Mesonephric System:
- Unsegmented Intermediated Mesoderm
3) Metanephric System:
- Unsegmented Mesoderm
Cervical Nephrotomes
- In the 4th week, 5 to 7 paired Nephrotomes appear in CERVICAL REGION
- Their development is Abortive
- Remain Nonfunction until disappearance (Day 24/25)
Mesonephros
- During 4th week a SECOND primitive Kidney develops
- Mesopnephvic Tubules form within Nephrogenic Cords
- About 40 Tubules develop in Craniocaudal Succession
Mesonepheric Tubules
- Veyr primitive Nephrons
- Regression of Cranial Tubules occurs with formation of Distal Ones
- By 5th week, 20 pair of Tubules are found in Lunbar Region
- Differentiate into function Nephric Units with GLOMERULI!!!!
Mesonephric Ducts
- Form at 24 days rom cords DORSOLATERAL to Mesonephric Tubules
- Run CAUDALLY to empty into Ventrolateral portion of CLOACA
- Fusion of Tubule Tip with duct provides passage from EXCRETORY UNIT —-> CLOACA
Mesonephros Development
- Present and functional from the 6th to the 10th weeks
- After week 10, it degenerates
- In the Male, its duct System will contribute to part of the Genital System
- Also contributes to VESTIGIAL STRUCTURES in the Female
Metanephros: Steps in Renogenesis
1) Cranial- caudal patterning establishes a “RENOGENIC” region within the Intermediate Mesoderm in the Tail of the Embryo
2) This Renogenic Mesoderm is the METANEPHRIC BLASTEMA
3) The METANPEHRIC BLASTEMA secretes growth factors that induce growth of the URETERIC BUD from the Caudal Portion of the Mesonephric Duct
4) URETERIC BUD secreted PAX2 which promotes condensation of the Mesenchyme preparatory to Tubule promotion and WNT4 which causes the condensed Mesenchyme to Epithelialize and form tubules
5) Modifications in the Extracellular Matrix also occur with change to LAMININ and Type IV Collagen, characteristic of an epithelial Basal Lamina
6) Cell Adhesion molecules SYNDICAL and E-Cadherin, which are essential for condensation of the Mesenchyme into an Epithelium
Molecular Regulation of Kidney Development
***WT1, expressed by the Mesenchyme, enables this tissue to respond to Induction by the URETERIC BUD!!!!!
In Utero Function of Metanephros
- Blood Plasma from Glomerular Capillaries begins to be filtered by 10th week
- Urine is produce but the Primary Function is not clear waste (placenta) but to SUPPLEMENT PRODUCTION of AMNIOTIC FLUID
**OLIGOHYDRAMNIOS (Insufficient amount of Amniotic Fluid) may indicate BILATERAL RENAL ANAGENESIS or URETHRA OBSTRUCTION
Changes in Kidney Position
- Kidneys are formed in PELVIS but ascend to LUMBAR REGION with progressive REVASCULARIZATION from COMMON ILIAC and AORTA
- **ACCESSORY RENAL ARTERIES ARE COMMON!!!!
- Supernumerary Renal Arteries
Renal Fusion
- Prevents Normal Rotation
- Abnormal Blood Supply, usually from MIDDLE SACRAL or COMMON ILIAC ARTERIES
Ectopic Kidney: May also be crossed with/ without Fusion
- *****HORSHOE KIDNEY!!!!!!!
- Supplied by INFERIOR MESENTERIC ARTERY (Found Inferior to these Arteries)
- Most Common
Development of the Urinary Bladder
- The Cloaca is then divided by the URORECTAL SEPTUM
- The DORSAL (Inferior) portion develops into the RECTUM and ANAL CANAL
- The VENTRAL (Superior) portion develops into the BLADDER and UROGENITAL SINUS, which will give rise to the Bladder and Lower Urogenital Tracts (Prostatic and Penile Urethrae in Males; Urethra and Lower Vagina in Females)
Development of Urinary Bladder Cont
- Between week 4 to 6, MESOSPHERIC DUCT and URETERIC BUD incorporation into POSTERIOR WALL of Urinary Bladder
- URETERIC BUDS open into Bladder Wall, while the MESONEPHRIC DUCTS open more Inferiorly into the Pelvic Urethra (Ductus Deferens doesn’t open into the Bladder)
- The Triangular Region of the Incorporated Mesospheric Duct incorporated in the Bladder wall forms the TRIGONE!!!!!
Exstrophy
- Failure of midline close of Inferior Abdominal Musculature of Anterior wall fails to form. Interior of Bladder open to external Environment
- Bifid Clitoris
- Bifid Penis
Defects of the Urinary Bladder
1) PATENT URACHUS:
- An entirely Tubular Urachus connects the Bladder to the Umbilicus
2) URACHAL SINUS:
- The Caudal Urachus partially obliterates
3) BLADDER DIVERTICULUM:
- The Proximal Urachus partially Obliterates
4) URACHAL CYST:
- Caudally and Proximally the Urachus partially Obliterates
Congenital Malformation of the Ureter and Kidney
- About 10% of newborns have a developmental abnormality of Urinary Tract
- Most do not cause Clinical Problems
- Because of Inductive dependence, abnormalities of one structure often causes abnormalities in the other
Bifid Ureter
- Ureter Branches early and then connects to form one main tube to the Bladder
Duplicate of Ectopic Ureter
1) Results from Growth of TWO URETERIC BUDS —–>
2) Problems arise with Bladder Development original. Caudal Ureter opens Normally —–>
3) Cranial Ureter follows Mesonephric Duct
Ectopic Ureter
- Found in Females more often than Males (6:1)
- In FEMALES, the Ectopic Orifice may open into: Vestibule (38%), Urethra (32%), Vagina (27%), pr Uterus (3%)
- In MALES, Orifice may occur in Prostatic Urethra, Seminal Vesicle, Ejaculatory Duct or Ductus Deferens
- Ureters draining into Bladder neck or Prostatic Urethra usually present as UTI/ Flank pain
- When Ectopic Ureters enter the Male Genital Tract. EPIDIDYMORCHITIS is COMMON…….
(URINE GETS INTO THE TESTIS!!!!!!)
Unilateral Renal Angenesis
- Incidence is 1/ 450 to 1/ 1800
- Clincal detection of UNILATERAL ABSENCE of DUCTUS DEFERENS in Males should suggest possibility of Unilateral Renal Anagenesis. Both could result from Abdence/ Abnormality of Mesonephric Duct
- Remaining kidney is more prone to Abnormality of Position and Rotation
- “Normal” life Expectancy
Bilateral Renal Angenesis
- Incompatable with life
- OLIGOHYDRAMNIOS Secondary to Absence of Intrauterine production
- Associated HYPOPLASTIC LUNGS are usually responsible for Death
- ***POTTER FACIES- Increased width between eyes, Flattening of Nose, Large Low-set ears!!!!!!
1) Pulmonary Hypoplasia
2) Positioning defects of Feet, Hands
3) Breech Presentation
Renal Dyspasia and Angenesis
- Failure of the Kidney to develop uni or bilaterally (Anagenesis) is due to the absence of Inductive Signals from the Ureteric Bud
- Mutations in the gene(s) that regulate GDNF Signaling, which controls Branching and Growth of the Ureteric Bud
Congenital (Infantile) Polycystic Kidney Disease
- AUTOSOMAL RECESSIVE
- Present in 1/ 10,000 live births but higher incidence in Prenatal and Stillborn Deaths
- Characterized by Multifocal Lesions of the Proximal Convoluted Tubule, Loop of Henle
- Result in dilation and Cyst formation and destruction of the surrounding tissue
Adult Polycystic Kidney
- AUTOSOMAL DOMINANT
- Nephron development is grossly disturbed
- RENAL FAILURE is usually presented by MIDDLE AGE
Wilm’s Tumor
- Cancer of the Kidney
- This usually affects Children under the age of 5
- Wulm’s Tumor is caused by MUTATIONS in the WT1 Gene!!!!!!!
Partitioning of the Cloaca
1) Rathke Fold
2) Tourney Fold
FAILRE of RATHKE FOLD to Develop:
- Resulting in a Rectourethral Fistula
- In Males, results in a RECTOPROSTATIC FISTULA
- In Females, it results in either a RECTOCLOACAL CANAL or a RECTOVAGINAL FISTULA!!!
