Development Of Gut (4) Flashcards
What does the hindgut go on to form?
Lower GI tract
Distal 1/3 transverse colon, descending colon, sigmoid colon, rectum, superior part of anal canal and urinary bladder
What is the origin of the hindgut during embryological development?
Originates from the cloaca which is a common cavity at the end of the digestive and urinary tracts
What is the cloaca ?
A common cavity at the end of the digestive and urinary tracts
How is the cloaca divided?
Into 2 separate spaces by thee descending Urorectal septum
What is the urorectal septum?
Wedge of mesoderm separating the cloaca into 2 separate spaces
What time period does the descending urorectal septum form?
Between 4th and 7th week of development
What are the 2 spaces created by the descending urorectal septum?
Anterior urogential sinus
Posterior anorectal space
What does the urogenital sinus develop into?
Bladder
Urethra
How is the anorectal canal related to the amniotic fluid?
Open to the amniotic fluid since at 7th week cloacal membrane ruptures
What is the terminal part of the GI tract where the anus will form called?
What covers it?
Proctodeum
Covered by ectoderm
How does the anus form at the proctodeum?
Anal/cloacal membrane ruptures allowing ectoderm to invaginate inwards to the distal anus
What is the pectinate line?
The junction between the ectoderm and endoderm at the distal anus
How do the types of cell differ above and below the pectinate line in the distal anus?
And what are these cells derived from?
Below the line = stratified squamous epithelia derived from ectoderm
Above the line = columnar epithelia derived from endoderm
What is the white line?
A line in the anal canal marking the upper anal canal and rectum
What type of cells are above and below this white line in the anal canal?
Above line = non-keratinised
Below line = keratinised (skin)
How is pain experienced above and below the pectinate line?
Below the line = localised pain since its somatic derived pain
Above the line = more vague pain since gut doesn’t have good pain receptors, responds to stretch and chemical injury
How is blood supply different above and below the pectinate line?
Below pectinate line = systemic blood supply
Above pectinate line = gut blood supply
What are some hindgut development abnormalities that can happen with a blood supply abnormality?
Imperforate anus
Anorectal agenesis
Fistulae
What is an imperforate anus?
When anal membrane fails to rupture
What is anorectal agenesis?
When the hindgut fails to form completely
What fistulae can form in the hindgut development?
Between the rectum and bladder or vagina
What is a fistula?
An abnormal connection between hollow epithelial lined cavities
