Embrio 1.3: Third Week Flashcards
Where do the mesoblast cells come from?
They are a product of the ectoblast cells that push down to form the ligne medianne
Membrane cloacale what it is an clinical relevance?
It is a plate on the caudal pole formed by the ectoblast and hypoblast.
In this region, these layers are so tightly connected that the mesoblast cannot separate them
this is important because this is where the anus will be !!
What is Entoblaste?
The old Hypoblaste that have been replaced by mesoblast cells give tou the Entoblaste
What is the canal chordal? What is special, why is this needed?
The chordal canal is a cavity that originates at the Noeud de Hensen and extends throughout the entire length of the notochord. This canal is formed through apoptosis. The lower part of the canal interacts with the entoblaste, triggering the cells it contacts to undergo apoptosis, or programmed cell death.
This interaction results in the creation of an opening (referenced on page 55, B) that gradually closes over time. Eventually, the cavity becomes completely filled, culminating in the formation of the definitive notochord.
The purpose of this entire process is to ensure synchronization, much like James Bond aligning his clock before a mission. The opening in the canal allows for the exchange of molecules from the top to the bottom and vice versa, facilitating communication about timing. Despite seeming like a return to the starting point, this process is crucial for maintaining the precise timing required for these complex processes.
In summary, the chordal canal is a key structure in the notochord’s formation, facilitating cellular communication and ensuring the precise timing of developmental processes.
True or False,
We can plant a spermatozoid into a ovocyte directly without having it wait for 5 days in the ismthe.
FALSE,
The sperm cell needs to undergo capacitation (acrosome maturation etc) in otrder for it to be able to fertilize
Chemical gradient and relation to plaque neurale?
The notochord releases SHH (sonic hedge hog) at a given gradient. All of the ectoblast that is in proximity with the gradient becomes the neural plate which will be the future neural tissue instead of skin tissue.
The cells of the crete neural are cells that have been exposed to enough SHH to not make skin, but not enough to make tube neural.
Those are te cells that will eventually close together in order to close the neural tube and let the top be covered with epiderme (future skin).
**Finally, the Séparation et migration des crêtes neurales forme les ganglions spinaux. **
See page 58
What is a tératome?
les cellules totipotentes de la** ligne primitive** et du noeud de Hensen se résorbent par apoptose (elles sont dites totipotentes méme si elles ne peuvent pas générer les tissus placentaires). **Cette absence d’involution peut évoluer en tératome **
ll arrive rarement que des enfants naissent avec une tumeur volumineuse dans le dos, au
niveau de la colonne vertébrale** sacro-coccygienne**. Il s’agit de «tératomes
sacro-coccygiens»; le terme «tératome» signifie que ces tumeurs sont composées d’éléments
provenant des **3 feuillets embryonnaires (ectoderme, mésoderme et endoderme). **
While these tumors are benign in utero, they will almost always become malignant in birth. As such, you need a QUICK surgery in birth to remove.
What are the structures that are responsible for the development of les cellules du tissu sous-cutané, de la colonne vertébrale et de toute la musculature du tronc et des extrémités.
les somites.
Les somites formeront les hémivertébres qui fusionneront pour former les vertébres qui entourent la moelle épiniére.
A person with a colone vertebrale that is not closed properly would likely have an issue with?
Les somites formeront les hémivertébres qui fusionneront pour former les vertébres qui entourent la moelle épiniére (Fig. 23). Une anomalie de fermeture de neuropore(s) cause un rachischisis ouvert. Les spina bifida occulta sont causés par une anomalie de fusion des hémivertèbres.
What is rachischisis ouvert?
Une anomalie de fermeture de neuropore(s) qui resulte au destruction des cellules nerveses du au contact avec le liquid amniotique
What is rachischisis ferme?
neuropore(s) sont fermees mais les hémivertébres ne sont pas
Une anomalie de fusion des vertébres cause un rachischisis fermé
can lead to a cyst with disorganized nervous tissue
day 21 and relevance to heart?
Day 21 is the day where the aorte gauche and aorte droite are going to fuse with one other and start spontanous contraction.
Le coeur primitif est initialement formé de la même manière: pendant la 3° semaine, les
angioblastes du pôle crânien élaborent deux vaisseaux dans l’axe longitudinal de l’embryon.
Ces deux vaisseaux fusionnent pour former le «tube cardiaque primitif» (Fig. 30). À la fin de
la 3° semaine (jour 21), ce tube est en continuité avec les autres vaisseaux embryonnaires et
extra-embryonnairesetilse contracte, établissant ainsi la circulation.
