1. Renal System Development
10th week
~12 weeks

2. Development of Three Nephric Systems Cervical Nephrotomes & Mesonephroi
Upper thoracic
region to the
third lumbar
region

3. Development of Three Nephric Systems Cervical Nephrotomes & Mesonephroi
6-10weeks-func
>10-regress.
Mesonephric
ducts in females
regress and in
males they persist
to form parts of
male genital duct
system.
Renal Corpuscle:
Glomerulus &
Bowman’s capsule
Mesonephric
excretory unit:
Renal corpuscle &
Nephric tubule
26 Days
~22 days

4. Development of Three Nephric Systems. Mesonephroi & Metanephroi
Regress to
the 1st three
lumbar levels
Mesonephric
duct forming
Sacral
Region
Reciprocal
induction
~22 days

5. Collecting Duct System of the Metanephroi Sequence of bifurcations.

6. Sequence of bifurcations
~22 days

7. Sequence of bifurcations.
11 additional
generations of
bifurcations-->
1-3 mil branches.
~22 days
32nd Week
8 months

8. Nephron Development
Contains neural crest derived neurons. They play a role in
nephron induction. The neurons regulate blood flow and
secretory function.
9th week
~22 days

9. Nephron Development 10weeks+-->func: gl. filtrate to urine,
but main func to produce amniotic fl.
10th week

10. Definitive Kidney Architecture
Minor calyx
Major calyx
Pelvis
Contains the nephrons.
Contains the loops of Henle
and collecting ducts .
5th-15th weeks
Renal Pyramid (inner medulla)

11. Kidneys ascend from a sacral to lumbar location
~22 days

12. Movement of the Kidneys
~22 days
Figure 8-6

13. Anomalies during kidney ascent
Inferior
mesenteric
artery
~22 days

14. The remainder of the urinary tract develops from the hingut endoderm Cloacal expansion and partition
4th week
Female Male
Vestibule of Penile
vagina urethra
Membranous membranous
urethra & prostatic
urethra
6th week

15. Exstrophy of the mesonephric ducts and ureteric buds.
4-6 weeks * * * * * * * *
-Endoderm grows over trigone
-Splanchnopleuric mesoderm associated
with the hindgut forms the smooth
muscle of the bladder wall.

16. Ureteric bud or metanephros induction defects Renal agenesis
A. Defects in the inductive interaction between the ureteric bud and
metanephric blastema may cause renal agenesis.
B. Bilateral renal agenesis results in death. Unilateral renal agenesis
results in hypertrophic kidney.
C. 75% of the cases involving renal agenesis occur in males.
D. Bilateral renal agenesis can also result in oligohydramnios, causing
Potter’s syndrome (deformed limbs and facial defects.
E. Unilateral renal agenesis is usually associated with heart defects
and constrictions of the gastrointestinal tract.

17. Genital System Development
4-6 weeks
~12 weeks

18. The genital and urinary systems develop in close conjunction Primitive sex cord & Paramesonephric duct development
(mullerian)
Third thoracic segment
caudally to the posterior
wall of the urogenital sinus
5-6 weeks

19. Virtually identical male and female genital systems.
6th week
At this point the sex
cords have both a
cortical and medullary
region. After the
6th week these regions
pursue different fates in
the male and female.

20. Basis of sex differentiation Autosomes and Sex Chromosomes
1. There is a total complement of 46 chromosomes, 22 pairs consist of matching
homologous chromosomes called autosomes. The 23rd pair are called the sex
chromosomes because they determine the sex of the individual.
2. XX individuals are genetically female.
XY individuals are genetically male.
Subsequent phases of sexual development are controlled by both the sex
chromosome genes and by the hormones and factors encoded by the
autosomes.
3. The sex-determining region of the Y chromosome (SRY) encodes a
transcription factor that controls the choice between the male and female
developmental paths.

21. Basis of sex differentiation Autosomes and Sex Chromosomes
4. Male development is triggered when SRY is expressed in the sex cords
during the indifferent phase.
5. Thus the male pathway is actively
induced.

22. Figure 10-13

23. Male genital (internal) Development Sertoli cell differentiation in the medullary sex cords
~7th week

24. Male genital (internal) Development Anti-Mullerian hormone (AMH) secretion by Sertoli cells
(reminant of
cranial end
of mesonephric duct)
~8-12th week
Sertoli
Cells
Ductuli efferentes
(reminant of inferior
mesonephric tubules)

25. Male genital (internal) Development Differentiation of the mesonephric ducts of the male
~10th-12th week

26. Male genital (internal) Development Differentiation of the accessory glands of the male urethra
~10th-12th weeks

27. Female genital (internal) development Absence of a Y chromosome

28. Female genital (internal) development Absence of AMH in the female embryo

29. Female genital (internal) development Absence of AMH in the female embryo

30. Female genital (internal) development Absence of AMH in the female embryo

31. External genitalia development Male and Female external genitalia develop from the same primordia
or urethral fold
External genitalia is
similar in male and
female embryos
through the
12th week.

32. External genitalia development. Male external genitalia.
12 weeks 14
weeks

33. External genitalia development Female external genitalia
7th week
3rd month

34. The gubernaculum controls the descent of the testes and ovaries The descent of the testes

35. The gubernaculum controls the descent of the testes and ovaries The descent of the testes

36. The gubernaculum controls the descent of the testes and ovaries The descent of the testes

37. The gubernaculum controls the descent of the testes and ovarie The descent of the ovaries

38. Abnormal dev of the genital system
Testicular Feminization Syndrome--> the androgen
receptors are abnormal or lacking, resulting in the formation
of a blind-ending vagina (Male genotype, Female external
phenotype, no ovaries). Since the testes are still present and
AMH is produced, the paramesonephric ducts regress (Thus
no superior vagina, uterus, or fallopian tubes).

39. Abnormal dev of the genital system
True hermaphrodites--> have both ovarian and testicular
tissue. The gonads are usually a composite ovotestes
containing both seminiferous tubules and follicles.
Or an individual may have an ovary on one side and a testes
on the other side.
Most true hermaphrodites are reared as
males since a phallus is usually present at birth.