GI anatomy Flashcards
What is the oropharyngeal membrane?
Cranial end of embryonic disc, small region of tightly adherent ectoderm and endoderm cells, no mesoderm. Represents future opening of oral cavity.
What is the cloacal membrane?
Caudal end of embryonic disc, small region of tightly adherent ectoderm and endoderm cells, no mesoderm.
What constitutes the foregut?
Foregut = oesophagus, 2/3 duodenum, liver, gall bladder, pancreas, spleen = coeliac trunk
What is the blood supply to the foregut?
Celiac trunk
What constitutes the midgut?
1/3 dudodenum, jujenum, lleum, caecum, appendix, ascending colon, 2/3 transverse = superior mesenteric atery
What is the blood supply to the midgut?
Superior mesenteric artery
What constitutes the hindgut?
1/3 transverse, rectum, upper anal canal = inferior mesenteric artery
What is the blood supply to the hindgut?
Inferior mesenteric artery
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?
5 pharyngeal arches
4 pharyngeal pouches
4 pharyngeal clefts
What are the pharyngeal arches called?
1,2,3,4,6 - THERE IS NO NUMBER 5. Dunno why..
What does the 1st pharyngeal arch give rise to?
Muscular- muscles of mastication, anterior belly of the digastric, mylohyoid, tensor tympani, tensor veli palatini
Skeletal - maxilla, mandible, incus, malleus, meckel’s cartilage
What does the 2nd pharyngeal arch give rise to?
Muscular - muscles of facial expression, buccinator, platysma, stapedius, stylohyoid, posterior belly of digrastric
Skeletal - stapes, styloid process, hyoid (lesser horn)
What does the 3rd pharyngeal arch give rise to?
Muscular - Stylopharyngeus
Skeletal - Hyoid (greater horn and body), thymus
What does the 4th pharyngeal arch give rise to?
Muscular - Cricothyroid muscle, all intrinsic muscles of soft palate (including levator veli palatini)
Skeletal - Thyroid cartilage, superior parathyroids, epiglottic cartilage
What does the 6th pharyngeal arch give rise to? culate cartilages
Muscular - All intrinsic muscles of the larynx except the cricothyoid muscle
Skeletal - Cricoid cartilage, arytenoid cartilages, corni
What does the 1st pharyngeal pouch give rise to?
Middle ear cavity
Auditory tube
What does the 2nd pharyngeal pouch give rise to?
Palatine tonsils
Tonsillar fossa
What does the 3rd pharyngeal pouch give rise to?
Inferior parathyroid gland
What does the 4th pharyngeal pouch give rise to?
Superior thyroid gland
When does the stomach appear as a fusiform dilatation in the foregut?
4th week
How does the stomach rotate?
90 degrees in a clockwise direction (left side becomes anterior)
How are the greater and lesser curvatures formed?
The originallly posterior wall grows faster and the anterior wall and so this gives rise to the greater and lesser curvatures
5 stages of midgut formation
Elongation, herniation, rotation, retraction and fixation
Describe midgut elongation
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
Describe midgut herniation
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
Describe midgut rotation
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
Describe midgut retraction
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
Describe midgut fixation
Some regions of the gut lose their dorsal mesentery and become retroperitoneal - duodenum, ascending colon and descending colon
Parietal and chief cells are found in a biopsy. What part(s) of the stomach may this biopsy be from?
Fundus/Body
What do these cells secrete? No abbreviations (4 marks) Chief Cells Parietal cells (2 things):
Parietal cells (2 things) = Intrinsic Factor- Hydrochloric Acid Chief Cells = Pepsinogen
What two substances cause the release of gastric acid by stimulating Histamine
Acetylecholine
Gastrin
