Lecture 24: Abdomen I Flashcards
Digestive Tube components, from top to bottom
Mouth, pharnynx, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum/appendix, colon, rectum, anal canal, anus)
Accesory organs to digestive tract
teeth, salivary glands, liver, pancreas
Signals for induction of endoderm
Fibroblast Growth Factor-4 (FGF-4), Activins
When does primordial gut tube form, what is it made of?
Beginning of fourth week, head, caudal, and lateral fold incorporate dorsal part of the yolk sac into the body. The gut tube/yolk sac is made of endoderm that gives rise to most of the digestive tract.
Stomodeum
pre-cursor of the mouth
proctodeum
pre-cursor of anal pit
What is the epithelium near the stomodeum and proctodeum made of?
ectoderm of those areas
What encloses the gut tube at either end
Cranially by the oropharyngeal membrane, caudally by the cloacal membrane
What are the derivatives of the primordial pharynx
oral cavity, pharynx, tongue, tonsils, salivary glands, upper respiratory system
What are the derivatives of the foregut?
It includes the primordial pharynx and all of its derivatives (oral cavity, pharynx, tongue, tonsils, salivary glands, upper respiratory system), the lower respiratory system (bronchi and lungs), esophagus and stomach, liver, pancreas, biliary apparatus, duodenum proximal to the bile duct
Where does the esophagus develop, what is it derived from?
From the fore-gut immediately caudal to the pharynx. The glands and epithelia are derived from the endoderm of the foregut. The striated muscle in the superior 1/3 are derived from the mesenchyme in the caudalpharyngeal arches, and the smooth muscle in the inferior 2/3 are derived from the surrounding splanchnic mesoderm
What separates the esophagus from the foregut during development.
The T-E septum, which eventually separates the esophagus from the trachea
How does the esophagus lumen change during development?
The canal is obliterated by proliferating epithelium, re-canalizes by the end of the eighth week. Can incompletely recanalize leading to a thin lumen, called esophageal stenosis.
The two causes of esophageal stenosis
Incomplete re-canalization at the end of the eight weeks or the failure of esophageal blood vessels to develop leading to atrophy of the esophagus.
Where does the stomach develop?
Distal part of the foregut, first develops as slight dilation in the median plane (which is the sagittal plane that goes right down the naval)
What attaches the stomach to the posterior abdominal wall
The dorsal mesentary, or the dorsal mesogastrium
What creates the greater curvature of the stomach, and where does it point towards initially?
While broadening dorsally and ventrally, the stomach (oriented in the medial plane) widens faster dorsally, creating the greater curvature pointing towards the vertebral column. The lesser curvature is then initially ventral, and points towards the anterior abdominal wall.
How does the stomach rotate?
It rotates 90 degrees clockwise, so the ventral lesser curvature moves right and the dorsal greater curvature moves left. Now lesser –> body right, and greater –> body left.
How does stomach rotation affect stomach innervation?
The original left side is now ventral and the original right side is now dorsal. The left vagus nerve supplies the anterior wall and the right vagus nerve supplies the posterior wall. The left vagus nerve is now renamed the anterior vagal trunk, and the right vagus nerve the posterior vagal trunk.
What happens to the dorsal mesentary during stomach rotation
Is carried to the left, creating the omental bursa, or the lesser sac of the peritoneum to the right of the dorsal mesentary
Ventral mesogastrium attaches to?
Suspends the stomach and duodenum to liver and ventral abdominal wall.
The purpose of the omental bursa, and it’s other name
Facilitates movement of the stomach. Also called lesser sac
Position of the omental bursa
Sits between the stomach and the posterior abdominal wall.
What makes up the greater omentum
the anterior and posterior fold layers of an elongated dorsal mesogastrium that fuse together by folding in on itself. There was an inferior recess within the fold, but that disappears during the fusing process.