GI development pt 2

Question 1

What does the midgut give rise to?

Answer 1

o Small intestine, including most of the duodenum (post bile duct entry)
o Caecum and appendix
o Ascending colon
o Proximal 2/3rds of the transverse colon

Question 2

How is the primary intestinal loop formed?

Answer 2

As a result of the rapid elongation of the midgut and the large size of the developing liver

Question 3

Describe the midgut loop - What are its two parts, what is its axis and where does it connect?

Answer 3

• Cranial and caudal limbs
• Superior mesenteric artery at ais
• Connected to vitelline duct

Question 4

What does the cranial limb of the midgut loop become?

Answer 4

Distal duodenum
Jejunum
Proximal ileum

Question 5

What does the caudal limb become?

Answer 5

Distal Ileum
Cecum
Appendix 
Ascending Colon
Proximal 2/3 transverse colon

Question 6

What process occurs to make room for developing midgut?

Answer 6

Physiological herniation

Question 7

What is physiological herniation?

Answer 7

Intestines herniate into the proximal umbilical cord

Question 8

What is rotation of the midgut?

Answer 8

Midgut rotates in a counterclockwise direction until we get the shape of the normal Gi. 270* counterclockwise rotation

Question 9

In what order do parts of the midgut return to the abdominal cavity?

Answer 9

Cranial limb return first, moving to left hand side

Cecal bud returns last

Question 10

What happens to the cecal bud once it has returned to the abdomen

Answer 10

Descends, moving caecum to right lower quadrant

Question 11

Give two types of malrotation

Answer 11

Incomplete rotation

Reversed rotation

Question 12

What does malrotation result in?

Answer 12

Gut hypermobility and volvulus

Question 13

What is incomplete rotation?

Answer 13

Midgut makes only one 90* rotation

Results in left sided colon

Question 14

What is reversed rotation?

Answer 14

Midgut makes one 90* rotation clockwise

Transverse colon passes posterior to the duodenum

Question 15

What is a volvulus?

Answer 15

A bowel obstruction where a loop of bowel abnormally twists in on itself
More likely with hypermobile (malrotates) guts

Question 16

What can volvulus lead to/

Answer 16

Strangulation and herniation

Question 17

What does the hind gut give rise to?

Answer 17

o	Distal 1/3 Transverse Colon
o	Descending colon
o	Rectum
o	Superior part of anal canal
o	Epithelium of the urinary bladder

Question 18

What is the cloaca?

Answer 18

The end of the hind gut

Question 19

What is the cloaca separated from the outside world by?

Answer 19

Cloacal membrane

Question 20

What happens at 6 weeks to the cloaca?

Answer 20

Partioning by the urorectal septum

Question 21

What does partioning by the urorectal septum create in the cloaca?

Answer 21

Urogenital sinus

Anorectal sinus

Question 22

What are the two parts of the anal canal derived from?

Answer 22

Superior derived from hindgut

Inferior from ectoderm

Question 23

What is the line at which the two parts of the anal canal separate?

Answer 23

Pectinate line

Question 24

What is the 
Blood Supply
Innervation
Epithelia
Lymph Drainage
above the pectinate line

Answer 24

Blood Supply - IMA
Innervation - S2-S4 PS
Epithelia - Columnar
Lymph Drainage - Internal iliac nodes

Question 25

``` What is the Blood Supply Innervation Epithelia Lymph Drainage below the Pectinate line ```

Answer 25

Blood Supply - Pudendal A Innervation - S2-S4 Pudendal nerve Epithelia - Stratified squamous (non K) Lymph Drainage - Superficial inguinal nodes

Question 26

What is the only sensation possible aboe pectinate line?

Answer 26

Stretch

Question 27

What is the sensation possible below pectinate line and why?

Answer 27

Temperature, touch and pain due to somatic innervation from pudendal nerve

Question 28

What is the white line?

Answer 28

A portion of ectodermal anal canal which separates Non-K Strat squamous from K Strat Squamous

Question 29

What is meckel's diverticulum?

Answer 29

Ileal diverticulum. Cul-de-sack as the result of failure of closure of vitelline duct

Question 30

What is the rule of 2's for meckel's diverticulum? (6)

Answer 30

``` o 2% of the population affected o 2 feet from the ileocecal valve o 2 inches long o Usually detected in under 2’s  Can be asymptomatic o 2:1 Male:Female - 2 types of tissue, gastric or pancreatic ```

Question 31

What is a vitelline cyst?

Answer 31

Vitelline duct frorm fibrous strands at either end

Question 32

What is a vitelline fistula?

Answer 32

Direct communication between the umbilicus and intestinal tract. This results in faecal matter coming out of the umbilicus.

Question 33

What is atresia and stenosis of intestines?

Answer 33

Complete loss or narrowing of lumen

Question 34

Give two reasons for lumen atresia

Answer 34

Unsuccesful recanalisation | Vascular accidents due to a loss of blood supply and dead gut

Question 35

Where does most atresia occur?

Answer 35

Duodenum

Question 36

Where is loss of blood supply causing atresia most common?

Answer 36

Duodenum, but not the most common cause >Jejunum = Ileum > Colon

Question 37

What is most common cause of atresia in upper duodenum?

Answer 37

Failure of recanalisation

Question 38

What is most common cause of atresia in lower duodenum?

Answer 38

Vascular accident (malrotation and volvulus)

Question 39

What is pyloric stenosis?

Answer 39

Narrowing of pyloric sphincter resulting in projecile vomiting

Question 40

Give two defects of abdominal wall

Answer 40

Gastroschisis | Omphalocoele

Question 41

What is gastrochisis?

Answer 41

Failure of closure of abdominal wall during embryo folding leaving gut tube and its derivatives outside the body NO COVERING

Question 42

What is omphaocoele?

Answer 42

Persisence of physiological herniation Umbilical cord covered by reflection of the amnion COVERING PRESENT

Question 43

Give three hindgut abnormalities

Answer 43

Imperforate anus - Failure of anal membrane rupture Anal agenesis - Failure of development Hindgut fistula - Abnormal connection to bladder

Question 44

What five structures retain their mesentery?

Answer 44

``` o Jejunum o Ileum o Appendix o Transverse colon o Sigmoid colon ```

Question 45

What four structures have fused mesenteries?

Answer 45

o Duodenum o Ascending colon o Descending colon o Rectum (no peritoneal covering in distal 1/3)