Embryology Flashcards
What happens in the third week of embryonic development?
Gastrulation.
what does gastrulation involve?
The embryoblast develops into three distinct germ layers: Ectoderm, Mesoderm and Endoderm.
Give some examples of what the ectoderm forms:
- Epidermis of skin, hair and nails
- Mammary, sweat, sebaceous and pituitary glands
- Central + peripheral nervous system
- enamel of teeth
- sensory epithelium of nose, ear and eye
- some of eye (lens + inner parts)
Give some examples of what the mesoderm forms:
- Musculoskeletal system
- Deep layers of skin
- Abdominal and chest walls + lining
- walls (not lining) of bowl
- Urogenital system
Give some examples of what the endoderm forms:
- Epithelial lining of GI tract, respiratory tract and urinary bladder
- Parenchyma of (para)thyroid gland, liver and pancreas
- Epithelial lining of tympanic cavity and auditory tube
$. Plays a part in development of notochord
What are the three main layers of the mesoderm:
- Paraxial plate
- Intermediate plate
- Lateral plate
When and how does the primitive heart tube form?
Days 19-21, from the fusion of the two endocardial tubes.
What are the five parts/bulges the primitive heart develops?
- Aortic sac
- Bulbus cordis
- Primordial ventricle
- Primordial atrium
- Sinus Venosus
What does the bulbos cordis go on to form?
The right ventricle, the smooth outflow portions of the ventricles and the proximal aorta and pulmonary trunk.
What has side of the heart has greater pressure in the developing fetus?
The right side as the lungs and pulmonary circulation are not fully functional.
What are the two foramen that occur before foramen ovale.
Foramen primum -> foramen secundum.
Which out of atria and ventricles are the first to have a left and a right?
Atria.
At what time does the ventricular septum grow?
The end of the fourth week.
What are conotruncal ridges (truncoconal swellings)?
Ridges of tissue on the sides of the truncus arterioses that will grow in a spiral and fuse to form a septum to divide the aorta and pulmonary trunk (aorticapulmonary septum).
Which aortic arch develops into the actual aortic arch?
The 4th arch (left one - right one forms right subclavian).
Which aortic arch disappears completely?
The 5th.
Which arches form:
a. the stapedial?
b. the carotid?
c. the maxillary?
a. 2
b. 3
c. 1
What period of development is when the aortic arches develop?
4-7 weeks.
Which aortic arch forms a pulmonary artery and the ductus arterioses?
The 6th arch (left).
Which vessel carries oxygenated blood from the placenta to the fetus?
The umbilical VEIN.
How does blood bypass the liver?
With the ductus venosus.
What shunts blood from the pulmonary trunk to the aorta?
The ductus arteriosus.
What does the umbilical vein eventually become?
Ligamentum teres.
What causes the foramen ovalis to close?
Lungs open up at birth decreasing pressure, so pressure is now greater in left side. Thus blood tries to flow back through the foramen ovali which pushes it shut.
