Download Dear all

Dear all…
Allah says in SORAT AL-Mumenon –translated-".12.And indeed We created
man(Adam) out of an extract of clay (water and earth
13.Thereafter We made him (the offspring of Adam) as a NUTFAH in a safe
lodging (womb of the woman) 14. Then we made the Nutfah into a clot, thenWe
made the clot into a little lump of flesh, then We made out that little lump of
flesh bones, then we clothed the bones with flesh, and then We brought it forth as
.another creation. So Blessed is Allah, the best of creators
15 .After that, surely, you will die.
16 Then (again), surely, you will be resurrected on the Day of Resurrection. .
‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
"‫"أفال يتدبرون القرآن ولو كان من عند غير هللا لوجدوا فيه اختالفا كثيرا‬
Sorat al-Nesa : 82.Do they not then consider the Qur'an carefully? Had it been
from other than Allah, they would surely have found there in many
contradiction
‫ـــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
- Don't hesitate to read this sheet because of its size, this is only due to figures in it.
- You should notice that this sheet only contains extra- and clarifying notes as almost
all what was mentioned in the lecture is written down in our professor's slides.
‫ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ‬
-Before we start with the embryology of the cardiovascular system, we will snapshot
the early developmental stages…
* In the 2nd week, the embryo used to be a bilaminar disk consisting only of
ectoderm and endoderm.
* Then at the beginning of the 3rd week , a process called Gastrulation occurs :
*Gastrulation is the process by which the bilaminar embryonic disc is converted into a
trilaminar embryonic disc. This process is the beginning of morphogenesis (development of
the form and structure of various organs and parts of the body). Gastrulation begins with the
formation of the primitive streak.Each of the three germ layers (ectoderm, endoderm, and
mesoderm) of the embryonic disc gives rise to specific tissues and organs.
* notice also that the trilaminar disk has the yolk sac anterior to it and the amniotic
cavity posterior.
*The yolk sac is lined with endodermal layer which will give later on the endothelial
lining of the gut and other cavities.
* At the beginning of the third week, a thickened, linear band of epiblast, the primitive
streak, appears caudally in the median plane of the dorsal aspect of the embryonic disc
andThe primitive streak results from the proliferation and migration of cells of the epiblast to
the median plane of the embryonic disc. The primitive streak actively forms mesoderm until
the early part of the fourth week; thereafter, its production slows down.
now let us imagine with each other,just try in your mind to cut the amniotic cavity and
the ectoderm to see the embryonic disk as a whole(look at the next 2 figures)
Dorsal views of the embryonic disc, showing how it lengthens and changes shape during the third week. The
primitive streak lengthens by the addition of cells at its caudal end; the notochordal process lengthens by the
migration of cells from the primitive node. The notochordal process and the adjacent mesoderm induce the
overlying embryonic ectoderm to form the neural plate, the primordium of the central nervous system.
Observe that, as the notochordal process elongates, the primitive streak shortens. At the end of the third
week, the notochordal process is transformed into the notochord.
- you can notice the changes occurring in the ectoderm producing the notochord and
the neural tube which is a bria and spinal cord to be.
-Also notice that there are 2 loci in the disk that consist only af firmly adherent 2
layers without the mesoderm ,thet will "break" later on :
+ Prochordal plate = Buccopharyngeal membrane = mouth to be.
+ Cloacal membrane= Anus to be.
As the notochord and the neural tube form, the intra-embryonic mesoderm on each side of
them proliferates to form a thick, longitudinal column of paraxial mesoderm and Each
column is continuous laterally with the intermediate mesoderm, which gradually thins into a
layer of lateral mesoderm. The lateral mesoderm is continuous with the extraembryonic
mesoderm that covers the umbilical vesicle and amnion. Toward the end of the third week,
the paraxial mesoderm differentiates and begins to divide into paired cuboidal bodies-called
somites-on each side of the developing neural tube
1-Paraxial mesoderm.=it will give myotoms(muscles of the back) and dermatoms.
2-Intermediate mesoderm= it forms most of the urogenital system.
3-Lateral mesoderm = it is what we are concerned with here, as scattered cavities are
formed on both sides that will join giving the intraembryonic coelom which will form
body cavities; i.e the pericardium, pleural cavity and the peretonial cavity.
-The intraembryonic coelom is horse-shoe shaped.
-Notice that before lateral folding(see below) we have bilateral cavities(on both sides)
-First stage of CVS development is the formation of Mesodermal blood islands in
wall of yolk sac,chorion and body stalk (placenta to be)
- The heart was first 2 bilateral blood islands that develop into capillaries then larger
tubes on both sides.
-They are located in the cardiogenic areas just ventral to the pericardium(try to
imagine the disk) and this is before folding.
A, A presomite embryo of approximately 18 days. C, An embryo of approximately 20 days,
showing the first pair of somites. A portion of the somatopleure on the right has been removed
to show the isolated coelomic spaces in the lateral mesoderm. E, A three-somite embryo
(approximately 21 days old), showing the horseshoe-shaped intraembryonic coelom, exposed
on the right by removal of part of the somatopleure.
Now about the folding :
A significant event in the establishment of body form is folding of the flat trilaminar embryonic
disc into a somewhat cylindric embryo. Folding results from rapid growth of the embryo,
particularly the brain and the spinal cord. Folding at the cranial and caudal ends and at the
sides of the embryo occurs simultaneously. Concurrently, a relative constriction occurs at the
junction of the embryo and the umbilical vesicle. Folding of the ends of the embryo ventrally
produces head and tail folds that cause the cranial and caudal regions to move ventrally as
the embryo elongates cranially and caudally
-Due to lateral folding,the heart tubes unit partially giving the primitive heart tube.
-you should also consider the following :
* the relations before craniocaudal folding :
- The Transverse septum (liver to be) is most cranially (it is a mesodermal mass)
- The buccopharyngeal membrane is most caudally.
- The yolk sac (umbilical vesicle) is ventral to the disk.
- The heart tubes are ventral to the pericardium.
*After the folding :
- The septum tranversum is most caudal.
- The buccopharyngeal membrane is most cranial.
- the primitive heart tube is dorsal to the pericardium but ventral to the foregut that
has formed along with other parts of the gut due to "sequestration" of the yolk sac.
And this can explain the relation of the heart with the esophagus.
* Notice that the neural crest will give the autonomic and sympathetic ganglia,
adrenal medulla and other neural structures,also some cells of it just migrate to the
heart and some participate in formation of facial structures.
Now look at this figure and concentrate with me :
* Once the heart "sinks" partially in the pericardium, it is still held by dorsal
mesocardium that will disappear leaving the transverse sinus of the pericardium
* now the deferential growth of the heart starts, and as it is held on both sides of the
cavity a loop is formed ……etc
* Note :
Don't be deceived by the figure on page 5 of the slides, only the bulbus cordis and
the ventricle are in.
- Always remember that variation in the shape or structure nature, may reflect
variation in origin ( smooth vs rough)
- the posterior smooth part of the right atrium is called sinus venarum.
-Notice each horn receives blood from 3 veins (not as written 2) (just add common
cardinal to them).
- also notice that the atrium, sinus venosus and veins draining into it are sunk in the
septum transversum at this stage.
* Due to the deferential growth and looping the heart finally gains it definitive shape
and there are many things to consider here :
1- The arterial end is getting closer to the venus end.
2- The trunkus arteriosus covers the upper border which is formed by atria.
3- Notice the atrial expansion.
4-Very important to consider the anterior location of the right atrium and ventricle
and this is due to the septa orientation ( the I.V septum is not sagital but it is between
coronal and sagital; i.e if it was sagital the right will be at right and the left at left.
*Notice that in the wall of pericardium there is a splanchnic mesoderm called
Myoepicardial mantle or cardiac gelly that will give the myocardium and the
epicardium while the heart tube gives only the endocardium.
- Notice also that the loop is to the right, if it was to the left = dextrocardia meaning
that the apex would be to the right.
* Now for the story of left horn obliteration and right enlargement just I will show
you an extra figure and say : "he left is left , considering vetelline veins"
Dorsal views of the developing heart. A, During the fourth week (approximately 24 days), the
primordial atrium and the sinus venosus, as well as the veins draining into them, are evident.
B, At 7 weeks, the right sinual horn is enlarged and the venous circulation through the liver is
established. (The organs are not drawn to scale.) C, At 8 weeks, showing the adult
derivatives of the cardinal veins. Arrows indicate the flow of blood
‫‪Finally , I would like to thank you all and give this poem to our best professor FARAJ‬‬
‫‪ALBUSTAMI :‬‬
‫ماااااااااااااالح لتاااااااااااااا‬
‫مهج اااااح ماااااه اااااب‬
‫لااااااااااة‬
‫لاااااااااااااا‬
‫اااااااااااااا‬
‫لتهااااااااام لاااااااااح‬
‫ااااااااا‬
‫ل تااااااااا‬
‫ل اااااااااا‬
‫لااااا ب ااااا‬
‫اااااب‬
‫لم هاااااااااا ماااااااااه‬
‫ااااااااام ل ااااااااا‬
‫اااااااااا‬
‫لااااااااااه‬
‫اااااااااا لالااااااااااا لال هااااااااااا‬
‫ااااااااابث لاااااااااا‬
‫ااااااااام لاااااااااح مب هاااااااااا‬
‫ل هااااااااااا‬
‫لجتااااااااااا‬
‫ل اااااااااه ااااااااااب‬
‫للااااااااه فاااااااا‬
‫اااااااااب‬
‫لاااااااا‬
‫********‬
‫فااااااااااااااا لجاااااااااااااا‬
‫ااااااااااااااااا‬
‫ااااااااااا ا‬
‫لااااااااااه‬
‫اااااااااااب‬
‫لااااااااب‬
‫*******‬
‫اااااااااااااا‬
‫لاااااااااااااااب‬
‫ا ناااااااااااااااااا ااااااااااااااااام‬
‫اااااااااااااااااا ب‬
‫ماااااااااه ب اااااااااح ااااااااا ا لاااااااااا‬
‫لاااااااابل تاااااااال الاااااااا لت اااااااا‬
‫ااااااااا‬
‫**********‬
‫لااااااااااااااااااااال م ال جتاااااااااااااااااااام ال تاااااااااااااااااااا‬
‫ااااااااااااااا خب اااااااااااااام‬
‫ن اااااااااااااااا لاااااااااااااااح له اااااااااااااااا ن ااااااااااااااا‬
‫ااااااااااااا ف اااااااااااا‬
‫لااااااااااااااااااااا ن ا هج هاااااااااااااااااااااا‬
‫ف ااااااااااااااااال اناااااااااااااااااا ااااااااااااااااا ا لاااااااااااااااااب‬
‫لت تااااااااااااااااااااااا‬
‫اااااااااااام‬
‫ااااااااام‬
‫أن ااااااااااااااا ختاااااااااااااام‬
‫نهااااااااااااااااااااااااا ف اااااااااااااااااااااااااا ها ااااااااااااااااااااااااا‬
‫تااااااااااااااااااااامن‬
‫اااااااااااام‬
‫ال نااااااااااااااا لاااااااااااااا م ل اااااااااااااا ه اااااااااااااا ا‬
‫لااااااااااا م اااااااااا ه‬
‫لااااااااح اااااااا‬
‫اااااااااا ب لالااااااااااا‬
‫خااااااااااااا ب لااااااااااااا‬
‫لااااااااااا‬
‫لال اااااااااااااااااااا‬
‫ل ااااااااااااااااااب‬
‫لااااااااااااااااااااااا ن ا ل مااااااااااااااااااااااا‬
‫‪THE END‬‬
‫مااااااااااااه ااااااااااااه اااااااااااا‬
‫ل ااااااااااااااااااااب‬
‫اااااااااااااااااااا ه‬
‫ناااااااااااااااااام‬
‫لتااااااااااااااااااب‬