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WEEK 9 OF GESTATION |
- CRL = 20mm.
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Amnion and Yolk
sac – normal video at 9.5 weeks of gestation.
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- Rapid changes occur in embryo.
- Spinal canal can be seen as two parallel lines.
- Very early embryonic movement.
- Sites of definitive placenta and attachment of umbilical cord can be identified.
- Amnion clearly seen.
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Developing fetal spine |
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- Limb buds are well seen projecting 90° to the fetal body.
- Anterior and posterior contours can be well seen and derivations from the normal can be identified e.g. nuchal thickening or translucencies.
- CNS:
- Diencephalon and its cavity, third ventricle, hemispheres and their cavity, lateral ventricle and aqueduct become visible.
- Cerebellum can be demonstrated for the first time (visible in all embryo's after 10 weeks 3 days).
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Three primary brain vesicles (5-6 wks menstrual age) |
Five secondary brain vesicles (6-7 wks menstrual age) |
Developed brain |
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Forebrain (Pronsencephalon) |
Telencephalon (craniad to
optic vesicles) Diencephalon
(caudad to optic vesicles) |
Cerebral hemispheres (lateral ventricles) Pineal gland, thalamus, hypothalamus,
pituitary stalk, third ventricle. |
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Midbrain (Mesencephalon) |
Mesencephalon |
Superior and inferior colliculi,
aqueduct of sylvius (connecting third and fourth
ventricle) |
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Hindbrain (Rhombencephalon) |
Metencephalon Myelencephalon |
Cerebellum, pons,
superior part of fourth ventricle Medulla oblongata, inferior part of
fourth ventricle, central canal of medulla. |
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