Embryology Flashcards
What is the term for the fertilised egg?
Oocyte
What does the morula turn into?
The cells of the morula reorganise to form a cavity, known as the blastocyst cavity (blastocoel).
From this point, the morula is known as the blastocyst.
Development of a human
Pre-embryonic phase 0-3 weeks
Embryonic phase 4-8 weeks
Foetal phase 9-40 weeks
Postnatal, childhood and adolescence
What are gametes and where are they formed?
Sperm (formed in the testis) and ovum (formed in the ovaries)
What can be found in the testis and what is their role?
Little cells called spermatogonia which are going to divide to form the sperms
What can be found in the ovaries
In the ovaries, there are follicles and within these follicles, you have the oogonia which is the parent cell going to divide to form the ovum.
When does the morula transform into a zygote?
End of day 5
What does the morula form?
Blastocyte
At 7 days, the blastocyst begins to burrow into the uterine wall (endometrium)
What hormone is used to detect pregnancy?
HCG
What does the inner cell mass flatten and form?
Two layers (bilaminar disc)
The top is called the epiblast and the bottom is called the hypoblast.
What does the bilaminar disc divide?
Divide the cavity with the cavity above the epiblast, the amniotic cavity and the cavity below the hypoblast, the yolk sac.
What does the bilaminar disc form?
Embryo
How does the embryo fold?
The embryo folds such that the amniotic cavity now covers the entire embryo
The yolk sac becomes smaller and smaller
What does the hypoblast become?
Yolk sac
What does the epiblast become?
Ectoderm, definitive endoderm, and mesoderm
What is the placenta formed from?
Chorionic villi
What type of twins always have 2 different placentas?
Non-identical twins (dizygotic)
What type of twins can have either one or two placentas?
Identical twins (monozygotic)
Where does the primitive streak form and what happens when it is formed?
In the midline of the epiblast by the dipping in of cells (invagination).
Once the primitive streak is formed, the axis of the embryo is formed.
What is gastrulation?
Formation of 3 germ layers
What are the three germ layers and what do they each form?
Ectoderm – forms skin, nervous system, sympathetic trunk, dorsal root ganglia
Mesoderm – forms muscle tissue, skeletal tissue, urinary and reproductive system
Endoderm – forms gut tube, respiratory tube
So, the bilaminar disk has become a trilaminar disk and the cells have become specialised.
What layers form the skin, muscles, spinal cord and nucleus pulposus of the vertebrae?
The skin is formed from the ectoderm
The muscles, the vertebrae and the vertebral arches are formed from the mesoderm
The neural tube forms the spinal cord
The notochord mostly disintegrates but some of it remains as the nucleus pulposus of the vertebrae
What forms the pleura and gut tube?
The lateral plate mesoderm will form the coverings of the respiratory tube (pleura) and the gut tube (peritoneum).
What buds out of the ventral wall of the primitive foregut in week 4?
Trachea and lung buds
