GI anatomy

Question 1

What is the oropharyngeal membrane?

Answer 1

Cranial end of embryonic disc, small region of tightly adherent ectoderm and endoderm cells, no mesoderm. Represents future opening of oral cavity.

Question 2

What is the cloacal membrane?

Answer 2

Caudal end of embryonic disc, small region of tightly adherent ectoderm and endoderm cells, no mesoderm.

Question 3

What constitutes the foregut?

Answer 3

Foregut = oesophagus, 2/3 duodenum, liver, gall bladder, pancreas, spleen = coeliac trunk

Question 4

What is the blood supply to the foregut?

Answer 4

Celiac trunk

Question 5

What constitutes the midgut?

Answer 5

1/3 dudodenum, jujenum, lleum, caecum, appendix, ascending colon, 2/3 transverse = superior mesenteric atery

Question 6

What is the blood supply to the midgut?

Answer 6

Superior mesenteric artery

Question 7

What constitutes the hindgut?

Answer 7

1/3 transverse, rectum, upper anal canal = inferior mesenteric artery

Question 8

What is the blood supply to the hindgut?

Answer 8

Inferior mesenteric artery

Question 9

In the 4th and 5th week of development the pharynx develops through the formation of pharyngeal arches, pharyngeal pouches and pharyngeal clefts. How many are there of each?

Answer 9

5 pharyngeal arches
4 pharyngeal pouches
4 pharyngeal clefts

Question 10

What are the pharyngeal arches called?

Answer 10

1,2,3,4,6 - THERE IS NO NUMBER 5. Dunno why..

Question 11

What does the 1st pharyngeal arch give rise to?

Answer 11

Muscular- muscles of mastication, anterior belly of the digastric, mylohyoid, tensor tympani, tensor veli palatini

Skeletal - maxilla, mandible, incus, malleus, meckel’s cartilage

Question 12

What does the 2nd pharyngeal arch give rise to?

Answer 12

Muscular - muscles of facial expression, buccinator, platysma, stapedius, stylohyoid, posterior belly of digrastric

Skeletal - stapes, styloid process, hyoid (lesser horn)

Question 13

What does the 3rd pharyngeal arch give rise to?

Answer 13

Muscular - Stylopharyngeus

Skeletal - Hyoid (greater horn and body), thymus

Question 14

What does the 4th pharyngeal arch give rise to?

Answer 14

Muscular - Cricothyroid muscle, all intrinsic muscles of soft palate (including levator veli palatini)

Skeletal - Thyroid cartilage, superior parathyroids, epiglottic cartilage

Question 15

What does the 6th pharyngeal arch give rise to? culate cartilages

Answer 15

Muscular - All intrinsic muscles of the larynx except the cricothyoid muscle

Skeletal - Cricoid cartilage, arytenoid cartilages, corni

Question 16

What does the 1st pharyngeal pouch give rise to?

Answer 16

Middle ear cavity

Auditory tube

Question 17

What does the 2nd pharyngeal pouch give rise to?

Answer 17

Palatine tonsils

Tonsillar fossa

Question 18

What does the 3rd pharyngeal pouch give rise to?

Answer 18

Inferior parathyroid gland

Question 19

What does the 4th pharyngeal pouch give rise to?

Answer 19

Superior thyroid gland

Question 20

When does the stomach appear as a fusiform dilatation in the foregut?

Answer 20

4th week

Question 21

How does the stomach rotate?

Answer 21

90 degrees in a clockwise direction (left side becomes anterior)

Question 22

How are the greater and lesser curvatures formed?

Answer 22

The originallly posterior wall grows faster and the anterior wall and so this gives rise to the greater and lesser curvatures

Question 23

5 stages of midgut formation

Answer 23

Elongation, herniation, rotation, retraction and fixation

Question 24

Describe midgut elongation

Answer 24

Rapid elongation of the midgut forms the primary intestinal loop
Cephalic limb develops into the distal part of the duodenum, jejunum and part of the ileum
The caudal limb develops into the lower portion of ileum, caecum, appendix, ascending colon, right 2/3 of transverse colon

Question 25

Describe midgut herniation

Answer 25

6th week of development, midgut enlarges further, becomes too big for abdominal cavity, is pushed out and passes into the extraembryonic cavity in the umbilical cord

Question 26

Describe midgut rotation

Answer 26

Total = 27o degress anticlockwise (from the front)
It rotates 90 degrees during herniation and 180% during return into the abdominal cavity
Elongation continues during rotation

Question 27

Describe midgut retraction

Answer 27

10th week it returns to the abdominal cavity

Jejunum returns first and settles on the left side, the following intestinal loops gradually more and more to the right

Question 28

Describe midgut fixation

Answer 28

Some regions of the gut lose their dorsal mesentery and become retroperitoneal - duodenum, ascending colon and descending colon

Question 29

Parietal and chief cells are found in a biopsy. What part(s) of the stomach may this biopsy be from?

Answer 29

Fundus/Body

Question 30

What do these cells secrete? No abbreviations (4 marks)
Chief Cells
Parietal cells (2 things):

Answer 30

Parietal cells (2 things) = Intrinsic Factor- Hydrochloric Acid 
Chief Cells = Pepsinogen

Question 31

What two substances cause the release of gastric acid by stimulating Histamine

Answer 31

Acetylecholine

Gastrin