The types of headaches can be considered in two categories, headache due to causes of outside the brain and the other inside the brain.
1. HEADACHE DUE TO CAUSES OF OUTSIDE THE BRAIN-
As the blastocyst develops further it gives rise not only to the tissues and organs of the embryo but also to a number of structure that support the embryo and helps to aquire nutrition at very early stage in development. The embryo proper aquires the form of a three layered disc. This is called the [...]
Blastocyst is a spherical cyst lined by flattened trophoblastic cells and inside it there is a mass of cells, the INNER CELL MASS, attached eccentrically to the trophoblast. Further changes are as follows:-
a) Some cells of the inner cell mass diffrentiate into flattened cells that to line its free surface. These constitute the ENDODERM- [...]
At one circular area near the margin of the disc the cubical cells of the endoderm become columnar. This area is called “PROCHARDAL PLATE.” The appearance of the prochardal plate determines the central axis of the embryo and also enables us to distinguish its head and tail ends.
DEFINITION:- These are the layers of the cells which are developed from zygote but, do not give rise to any part of embryo proper. These are shed after the birth of the foetus. These are CHORION, AMNION, PLACENTA, UMBLICAL CORD, to know about chorion, placenta and umblical cord you are requested to view other posts.AMNION:- [...]
1) The trophoblast is at first made up of a single layer of cells. As these cells multiply two distinct layers are formed. The cells that are nearest to the decidua loose their cell boundaries. Thus one continous sheet of cytoplasm containing many nuclei is formed. Such a tissue is called “SYNCYTIUM”.
Hence this [...]
a) The cells of the trophoblast gives origin to a mass of cells called the extra embryonic mesoderm or primary mesoderm. These cells come to lie between the trophoblast and the flattened endodermal cells lining the yolk sac. Thus separating them from each other. These cells also separate the wall of amniotic cavity from the [...]
It is a tube of amnion which connects the foetus with the placenta. It is about one and half metres in length.
a) WHARTON’S JEELY- It is a thick extraembryonic mesoderm.
b) RIGHT and LEFT UMBLICAL ARTERIES- these carries the deoxygenated blood from the foetus to the placenta. After birth the two umbilical arteris are converted into [...]
Pancreas develops from endoderm by 2 diverticulum called- Ventral pancreatic bud
Dorsal pancreatic bud
VENTRAL PANCREATIC BUD- It develops on the ventral side caudal to the hepatic bud and communicates with it.
DORSAL PANCREATIC BUD- It develops on the dorsal side and grows dorsally into the dorsal mesentry.
It is endodermal in origin. It develops as a diverticulum at the junction of foregut and midgut called HEPATIC BUD. This grows cranially and forwards into the mesoderm and septum transversum. A second diverticulum called cystic bud grows from its lower end.
