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Development of Hindgut. Dr. Rania Gabr. Objectives. Enlist the derivatives of hindgut. Discuss the development of Hindgut. Describe Hindgut abnormalities. Derivatives of Hindgut. Distal 1/3 rd of the transverse colon Descending colon Sigmoid colon Rectum Upper part of the anal canal - PowerPoint PPT Presentation
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Development of Hindgut
Dr. Rania Gabr
Objectives• Enlist the derivatives of hindgut.
• Discuss the development of Hindgut.
• Describe Hindgut abnormalities.
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.
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
• 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
Cloaca
Partitioning of the cloaca-Occurs during 4th to 7th weeks- Urorectal septum , which is a mesodermal septum, divides cloaca into:1-Primitive urogenital sinus anteriorly2- Anorectal canal posteriorly
• After division of the cloaca, the anorectal canal becomes continuous with the hindgut to form the Rectum and Anal canal
Formation of primitive urogenital sinus & anorectal
canal
Cloaca• The Primitive urogenital sinus is divided by the the
opening of mesonephric duct into:1. Vesico-uretheral canal2. Definitive urogenital sinus.
• This septum divides also cloacal membrane into ventral urogenital membrane and dorsal anal membrane.
Partitioning of CloacaBy 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
Cloacal membrane
urogenital membrane (anteriorly) anal
membrane
(posteriorly)
Urogenital membrane
Anal membrane
Urorectal septum
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).
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.
Congenital Anomalies
• 1- Imperforate Anus:
• Failure of rupture of the anal membrane.
2- Rectovaginal fistula
3- Urorectal fistula
4- Rectoperianeal fistula