Embryology Of Hind Gut

Question 1

▪ Derivatives of the hindgut are;
▪ The hindgut derivatives are supplied by the ———artery

Answer 1

▪ Derivatives of the hindgut are; The,
▪ Left 1/3-1/2 of the transverse colon
▪ Descending colon, Sigmoid colon, Rectum
▪ Superior part of the anal canal
▪ Epithelium of the urinary bladder and most of the urethra
▪ The hindgut derivatives are supplied by the Inferior mesenteric artery (IMA)

Question 2

▪ The terminal portion of the hindgut is enlarged as the ——

Answer 2

▪ The terminal portion of the hindgut is enlarged as the cloaca.

Question 3

CLOACA
▪ An endoderm-lined structure in contact with the surface ectoderm at the —— membrane without any intervening mesoderm
▪ The cloacal membrane- endoderm of the cloaca and ectoderm of the ——- (anal pit)
▪ The cloaca receives the —— (a finger-like diverticulum)

Answer 3

CLOACA
▪ An endoderm-lined structure in contact with the surface ectoderm at the cloacal membrane without any intervening mesoderm
▪ The cloacal membrane- endoderm of the cloaca and ectoderm of the proctodeum (anal pit)
▪ The cloaca receives the allantois (a finger-like diverticulum)

Question 4

Partitioning of the cloaca
▪ The cloaca is divided into dorsal and ventral parts by a wedge of mesenchyme- the ——- septum (btw allantois and hindgut)
▪ The urorectal septum pushes forward and forms a partition that divides the cloaca into;

Answer 4

Partitioning of the cloaca
▪ The cloaca is divided into dorsal and ventral parts by a wedge of mesenchyme- the urorectal septum (btw allantois and hindgut)
▪ The urorectal septum pushes forward and forms a partition that divides the cloaca into;
􏰀 The rectum and cranial part of the anal canal (dorsally)
􏰀 Urogenital sinus ventrally

Question 5

By the —th week, the urorectal septum fuses with the cloacal membrane and divides it into:
􏰀 Dorsal anal membrane
􏰀 Larger ventral urogenital membrane
▪ The area fusion of the urorectal septum and cloacal membrane is the —— in the adult

Answer 5

By the 7th week, the urorectal septum fuses with the cloacal membrane and divides it into:
􏰀 Dorsal anal membrane
􏰀 Larger ventral urogenital membrane
▪ The area fusion of the urorectal septum and cloacal membrane is the perineal body in the adult

Question 6

▪ The urorectal septum also divides the cloacal sphincter into ant and post parts.
▪ Post part becomes- ——
▪ Ant part- ——
▪ The anal membrane usually ruptures at the end of the —-th week.

Answer 6

▪ The urorectal septum also divides the cloacal sphincter into ant and post parts.
▪ Post part becomes- ext anal sphincter
▪ Ant part- the superficial transverse perineal, bulbospongiosus and ischicarvernous muscles
▪ The anal membrane usually ruptures at the end of the 8th week.

Question 7

Failure of rupture of the anal membrane will lead to—-

Answer 7

Imperforate anus

Question 8

The Anal Canal
▪ Sup 2/3 of adult anal canal is from—
▪ Inf 1/3 is from—
▪ Jnx of the two epithelia is indicated by the irregular ——
▪ Approx —cm sup to the anus is a/an —— line (what is the color of the line?)- approx where the composition of the anal epithelium changes from columnar to stratified squamous (keratinized)

Answer 8

The Anal Canal
▪ Sup 2/3 of adult anal canal- hindgut
▪ Inf 1/3 is from proctodeum
▪ Jnx of the two epithelia is indicated by the irregular pectinate line
▪ Approx 2cm sup to the anus is an anocutaneous line (white line)- approx where the composition of the anal epithelium changes from columnar to stratified squamous (keratinized)

Question 9

▪ Approx 2cm sup to the anus is an anocutaneous line (white line)- approx where the composition of the anal epithelium changes from —- to—-

Answer 9

▪ Approx 2cm sup to the anus is an anocutaneous line (white line)- approx where the composition of the anal epithelium changes from columnar to stratified squamous (keratinized)

Question 10

Anomalies of the hindgut
Hirschsprung’s Disease
▪ Results from the failure of neural crest cells to migrate and form the —- plexus in the —- colon and —- during —th to —th week of gestation.
▪ The resulting lack of innervation results in loss of ——, ——, and ——.

Answer 10

Anomalies of the hindgut
Hirschsprung’s Disease
▪ Results from the failure of neural crest cells to migrate and form the myenteric plexus in the sigmoid colon and rectum during 5th-7th week of gestation.
▪ The resulting lack of innervation results in loss of peristalsis, fecal retention, and abdominal distention.

Question 11

Anomalies of the hindgut
—— Disease
▪ Results from the failure of neural crest cells to migrate and form the myenteric plexus in the sigmoid colon and rectum during 5th-7th week of gestation.
.

Answer 11

Anomalies of the hindgut
Hirschsprung’s Disease
▪ Results from the failure of neural crest cells to migrate and form the myenteric plexus in the sigmoid colon and rectum during 5th-7th week of gestation.
.

Question 12

Hirschsprung’s Disease
▪ —- in —- live births; most common cause of neonatal colonic obstruction, resulting in congenital ——
▪ Affects mostly —- and —- colon
▪ which gender is more affected

Answer 12

Hirschsprung’s Disease
▪ 1 in 5000 live births; most common cause of neonatal colonic obstruction, resulting in congenital megacolon
▪ Affects mostly rectum and sigmoid colon
▪ Males more affected

Question 13

List other anomalies of the hind gut

Answer 13

▪ Imperforate anus
▪ Anorectal anomalies
􏰀 Rectovesical fistula (abnormal opening to the bladder)
􏰀 Rectourethral fistula
􏰀 Rectovaginal fistula
▪ Rectal atresia- anal canal and rectum
presented but separated
▪ Anal stenosis (narrowing)

Question 14

List the different anorectal anomalies

Answer 14

Rectovesicular fistula
Rectourethral fistula
Rectovaginal fistula

Question 15

Imperforate anus occurs — in —- infants
Mostly in which gender

Answer 15

1:5000
Males