Embryology Flashcards
When does formation of the tongue start?
4th week
Which pharyngeal arch is the mucous membrane derived from?
1st Arch
How many swellings do the anterior 2/3 of the tongue have?
2 lateral swellings
1 median swelling
-hypobranchial eminence (from mesoderm of 2nd, 3rd, and part of 4th arch)
What does the 2nd arch contribute to the tongue?
Facial nerve: contributes taste to anterior 2/3rd of the tongue
What does the 3rd branchial arch contribute to the tongue?
Overgrows: Glossopharyngeal nerve-posterior 1/3rd of the tongue
What does the 4th branchial arch contribute to the tongue?
Third swelling: superior laryngeal nerve-posterior most part of the tongue (epiglottis)
What contributes to the sensations of the anterior 2/3rd of the tongue?
- lingual (general) (branch of mandibular division of 5th nerve, 1st arch)
- chorda tympani (special) (branch of facial nerve, 2nd arch)
What are the muscles of the tongue derived from?
Derived from occipital myotomes (somites) innervated by-Hypoglossal nerve
What germ layers are the GIT derived from?
Endoderm-epithelial lining and glands of digestive and respiratory tracts
Mesoderm-wall of digestive and respiratory tracts; visceral serosa
What happens during the 3rd-4th week?
- Neural tube elevates and closes dorsally
- Gut tube rolls and closes ventrally
- Flat trilaminar embryonic disc becomes cylindrical
What are the head fold, tail fold, and lateral folds that occur during the 3rd-4th week?
- Head and tail fold: caused by growth of neural tube
- Lateral folds: caused by growth of somites
- Margins of four folds-bound the primitive umbilical opening
Ventral body wall defects involve one/both …
Lateral body wall folds fail to progress ventrally to fuse in midline
What are the ventral body wall defects in the thorax, abdomen, and pelvis?
Thorax: ectopia cordis
Abdomen: gastroschisis
Pelvis: bladder/cloacal exstrophy
What are the characteristics of gastroschisis?
- Due to abnormal closure of the body walls around the connecting stalk
- Abdominal viscera herniate through the body wall directly into the amniotic cavity
- Detected prenatally through ultrasonography and by elevated alpha-fetoprotein
- The defect occurs usually on the right side of the umbilicus
How is the primitive gut tube formed?
As a result of craniocaudal (cephalocaudal) and lateral folding
-portion of the yolk sac is incorporated into the embryo to form primitive gut tube
What do the endoderm, mesoderm, and neural crest contribute to the primitive gut tube?
Endoderm: epithelial lining of the GI
Mesoderm: lamina propria, muscularis mucosa, submucosa, muscularis externa, and adventitia/serosa
Neural Crest: neurons and nerves of the submucosal and myenteric plexus
For molecular regulation of GIT, specification is initiated by what?
Retinoic Acid gradient
The retinoic acid gradient causes which transcription to the expressed and what do they regulate?
SOX2-esophagus and stomach
PDX1-duodenum
CDXC-small intestine
CDXA-large intestine and rectum
Epithelial-mesenchymal interactions is initiated by what gene?This gene expression establos nested expression of what gene?
Sonic Hedgehog gene (SHH)
HOX genes in mesoderm
What are the adult structures derived from the foregut?
Celiac artery, esophagus, stomach, duodenum (first and upper half of 2nd part), liver, pancreas, biliary apparatus, gallbladder
What are the parasympathetic and sympathetic nerves for the foregut?
Parasympathetic-vagus
Sympathetic:
-preganglionic T5-T9 thoracic splanchnic nerves
-postganglianic cell bodies: celiac ganglion
What are the adult structures derived from the midgut?
Superior mesenteric artery, duodenum (lower half of second part, third and fourth part), jejunum, ileum, cecum, appendix, ascending colon, transverse colon (right two-thirds)
What are the parasympathetic and sympathetic nerves from the midgut?
Parasympathetic: vagus
Sympathetic:
-preganglionic T8-T11 thoracic splanchnic nerves
-postganglionic cell bodies: superior mesenteric ganglion
What are the adult structures derived from the hindgut?
Inferior mesenteric artery, transverse colon (left one-third), descending colon, sigmoid colon, rectum, anal canal (above pectinate line)
What are the parasympathetic and sympathetic nerves derived from the hindgut?
Parasympathetic: pelvis splanchnic
Sympathetic:
-preganglionic L1-L2 lumbar splanchnic nerves
-postganglionic cell bodies: inferior mesenteric ganglion