1. Development of Hindgut
Dr. Rania Gabr

2. Objectives Enlist the derivatives of hindgut.
Discuss the development of Hindgut.
Describe Hindgut abnormalities.

3. Derivatives of Hindgut
Distal 1/3rd of the transverse colon
Descending colon
Sigmoid colon
Rectum
Upper part of the anal canal
The endoderm of the hindgut also forms the internal lining of the urinary bladder and urethra.
In 5th week midgut is suspended from the posterior abdominal wall by a short mesentery.
The Midgut is connected with yolk sac by vitelline duct or yolk stalk.

4. Development of Hindgut
The terminal portion of the hindgut enters into the posterior region of cloaca, the anorectal canal.
The Developing hindgut is supplied by the inferior mesenteric artery.
The junction between the segment of transverse colon derived from the midgut and that originated from the hindgut is indicated by the change in blood supply

6. Cloaca
The Cloaca is the dilatation of hind gut closed by The cloacal membrane
The Cloaca receives three openings:
The Alantois ventrally
2 Mesonephric ducts one on each side

7. Partitioning of the cloaca
-Occurs during 4th to 7th weeks
- Urorectal septum , which is a mesodermal septum, divides cloaca into:
1-Primitive urogenital sinus anteriorly
2- Anorectal canal posteriorly

9. After division of the cloaca, the anorectal canal becomes continuous with the hindgut to form the Rectum and Anal canal

12. Formation of primitive urogenital sinus & anorectal canal

14. Cloaca
The Primitive urogenital sinus is divided by the the opening of mesonephric duct into:
1. Vesico-uretheral canal
2. Definitive urogenital sinus.
This septum divides also cloacal membrane into ventral urogenital membrane and dorsal anal membrane.

16. Partitioning of Cloaca
By the seventh week, the urorectal septum has fused with the cloacal membrane
Dividing it into a dorsal anal membrane and a larger ventral urogenital membrane
The area of fusion of the urorectal septum with the cloacal membrane is represented in the adult by the perineal body

17. Cloacal membrane urogenital membrane (anteriorly) anal membrane
(posteriorly)

18. Urogenital membrane
Urorectal septum
Anal membrane

19. Rectum and Anal Canal
The Dorsal part of cloaca (anorectal canal) forms the mucosa of rectum and upper ½ of anal canal.
While their muscles are develop from the surrounding mesoderm.
The Lower ½ of anal canal develops from proctodeum (ectodermal depression below anal membrane).

20. Rectum and Anal Canal
The Anal membrane ruptures at the 9th week to allow continuity between the 2 parts of anal canal.
The Upper ½ of the anal mucosa is endodermal while lower ½ is ectodermal.
The Pectinate line separates between 2 parts in adult.

21. Congenital Anomalies 1- Imperforate Anus:
Failure of rupture of the anal membrane.

22. 2- Rectovaginal fistula

23. 3- Urorectal fistula
Dr. Sherif Fahmy

24. 4- Rectoperianeal fistula