Flashcards
Embryology-CVS
Cards in this deck (79)
- 1How does nutrients reach the fetus before three weeks?the nutrient materials
reach the fetus by simple diffusion. After that age the blood vessels begin to develop and nourish the embryo - 2What happens after 3 weeks?groups of cells called
angioblastic cells are collected together to from islands
of cells. - 3What is the origin of the angioblastic cells-Intraembryonic mesoderm.
- Fetal membranes: including the chorion, connecting
stalk and wall of yolk sac - 4explain DEVELOPMENT OF BLOOD VESSELS-The central cells of these islands are separated from the peripheral one and will from the blood cells (W.B.Cs and R.B.Cs).
¨- The peripheral cells from the blood vessels. - 5During fetal life what is the oxygenated blood from the placenta carried by?-left umbilical vein to the (left
branch of the portal vein)
- Part of this blood is carried via
the ductus venosus to the (inferior vena cava)
-The other part enters the liver by means of the portal vein and leaves it by means of the hepatic veins to (inferior vena cava) - 6Blood passes from the inferior vena cava to the ?right atrium
- 7where does the blood go from the right atrium now??1- there is a major pathway
-and a minor pathway - 8Explain the major pathwayblood passes through the foramen ovale then to the left atrium, passes to the left ventricle and then to the aorta. Most of it supplies the heart itself, the head and neck, the brain and the upper limbs.
- 9Explain the minor pathwayThe blood reaching the right atrium via the inferior vena cava, enter into the
right ventricle and then into the pulmonary trunk. Since the lungs of the fetus are not functioning, a small amount of this blood enters the pulmonary vascular bed while most of the blood passes through the ductus arteriosus into the descending aorta to join the blood coming to this part of aorta from the left ventricle. It supplies the lower limbs, the trunk and the viscera. - 10How is most of the blood returned to the placenta again?by means of two umbilical arteries.
- 11What happens when the placental circulation stops at birth?1. The left umbilical vein become obliterated and form the ligamentum teres of the liver
2. The ductus venosus become obliterated and form the ligamentum venosum of the liver.
3. The distal part of the umbilical arteries become also
obliterated and from the medial umbilical ligaments and the proximal parts remain open as superior vesical arteries - 12How is the closure of the umbilical arteries accomplished?by contraction of the smooth
musculature in their walls, is probably caused by thermal and mechanical
stimuli and a change in oxygen tension. - 13When do these arteries close?Functionally the arteries close a
few minutes after birth, although the actual obliteration of the lumen by fibrous proliferation may take 2 to 3 months - 14When does The pulmonary circulation starts?1-The ductus arteriosus become obliterated and form the ligamentum arteriosum.
- 15How does this obliteration happen?-By contraction of its muscular wall occurs almost immediately after birth; it is mediated by bradykinin, a substance released from the lungs during initial inflation.
- Complete anatomical obliteration by proliferation of the intima is thought to take 1 to 3 months. - 16What is the second cause for pulmonary circulation to start?2. The foramen ovale becomes obliterated. The septum primum forms the fossa ovalis and the edge of septum secondum forms the annulus ovalis
- 17How is this obliteration caused?caused by an increased pressure in the left atrium, combined with a
decrease in pressure on the right side. The first breath presses the septum
primum against the septum secundum. During the first days of life,
however, this closure is reversible. Crying by the baby creates a shunt
from right to left, which accounts for cyanotic periods in the
newborn. Constant apposition gradually leads to fusion of the two septa
in about 1 year. In 20% of individuals, however, perfect anatomical
closure may never be obtained (probe patent foramen ovale) - 18DEVELOPMENT OF THE HEART the cardiogenic area-Initially, the central portion of the cardiogenic area is anterior to the buccopharyngeal membrane and the neural plate
- 19What does the cranial folding do?Cranial folding rotates cardiogenic area, moving it ventrally and caudally,orients heart tube and pericardial cavity.
REFER to slide for pics - 20What does the heart begin as?1) Begins as two
endothelial heart tubes.
2) The two heart-tubes fuse
with each other giving
single heart tube.
3) One end of the tube is arterial (for
the exit of the blood), while the
other end is venous (where the
blood enters the heart tube). - 21What happens after the tube fuses?A constriction appears in the heart
tube and divided it into:
i. Cephalic part: Gives primitive
ventricle.
ii. Caudal part:Gives primitive
atrium - 22What happens then in the primitive ventricle?In the primitive ventricle, 2 additional
constriction appear differentiating it
into three chambers (from caudal to
cephalic ends):
i. Primitive ventricle.
ii. Bulbus cordis.
iii. Truncus arteriosus which is
continuous distally with the aortic
sac - 23What happens in the primitive atrium?the region where the veins drain become dilated and forms the sinus venosus.
- 24The heart tube now consists of?1) Sinus venosus
2) Primitive atrium
3) Primitive ventricle
4) Bulbus cordis and;
5) Truncus arteriosus
-The heart tube, at this stage, is connected to the oesophagus by a mesentery called dorsal
mesocardium and is fixed at its two
ends. - 25REFER TO SLIDE 13 for pics.
- 26what happens at 21-22 days?-The developing heart tube
bulges more and more into the pericardial cavity. Initially, however, the tube remains attached to the dorsal side of the pericardial cavity by a fold of
mesodermal tissue, the dorsal mesocardium and No ventral mesocardium is ever formed. - 27What happens to the dorsal mesocardium later?The dorsal mesocardium is
breaking down, creating the
transverse pericardial sinus,
which connects both sides of
the pericardial cavity. The
heart is now suspended in
the cavity by blood vessels at
its cranial and caudal poles
LOOK AT SLIDE 15 for pics - 28What does Further growth and elongation of the tube result in-U-Shaped loop. One
limb of this loop is arterial,
while the other is the venous
limb - 29What happens at day 23?The heart tube continues to
elongate and bend on day 23.
The cephalic portion of the
tube bends ventrally, caudally,
and to the right and the atrial
(caudal) portion shifts
dorsocranially and to the left.
This bending, which may be due
to cell shape changes, creates the
cardiac loop. - 30what happens at day 28the cardiac loop It is complete by day 28 and finally it becomes S – shaped.
- 31Explain how does the heart appear as S shaped?-The heart appears as S-shape, with the first bend in the S between bulbus cordis and ventricle and the second bend between the atrium and sinus venosus.
-¨ The Atrioventricular canal (AVC) between the primitive
common atrium and the primitive ventricle; and the outflow
tract (OFT) is continuous cranially. - 32Development of the sinus venosusIs the dilatation of the primitive atrium where the veins
of the body, intestine and placenta opens. - 33At early stage: The sinus venosus is composed of:- Body (the central part).
- Right and left horns. Each horn receives the following veins :
1. Vitelline vein: carries unoxygenated blood from the yolk sac.
2. Umbilical vein: carries oxygenated blood from the placenta
3. Common cardinal vein: carries unoxygenated blood from the body wall. It is formed by the union of anterior and posterior cardinal veins - 34What happens later on?Later on:- The blood reaches the right horn becomes
more than that of left horn due to:
1. The development of the liver on the right side.
2. The presence of transverse anastomoses between the
left and right cardinal veins, shifting the blood from left to right side - 35What happens as a result of this?The right horn increases in size,
while the left horn becomes reduced in size - 36What happens to the body/right and left horn?-The body: becomes
reduced in size to form the
coronary sinus.
¨ The right horn: is enlarged
and absorbed into the right
atrium to form the smooth
posterior part of the right
atrium.
¨ The left horn: is reduced
in size to form the oblique
vein of left atrium. - 37How is septum intermedium formed in the atriventricular canal divison?-Dorsal & ventral atrioventricular
endocardial cushions appear at the
dorsal and ventral wall of the
atrioventricular canal.
-The ventral and dorsal cushions,
project further into the lumen and
fuse, resulting in formation of
Septum Intermedium and complete
division of the canal into right and
left atrioventricular orifices by the
end of the 5th week. - 38what is the FATE OF ATRIOVENTRICULAR CANAL1. The upper part of the atrioventricular canals: will be
absorbed into the corresponding atrium (right and left).
2. The lower part of the atrioventricular canals: will be into
the corresponding ventricles (right and left).
3. The septum intermedium, itself: shares in the formation of
interatrial septum and the membranous part of the interventricular
septum.
REFER to slide for pics - 39Explain the DEVELOPMENT OF SEPTUM PRIMUMA sickle shaped septum (septum
primum) grows from the roof of
the primitive atrium towards the
septum intermedium.
• The lower rim of the septum
primum is separated from the
septum intermedium by opening
called the foramen primum
REFER FOR PIC SLIDE 22 - 40What happens after that?Before complete closure of the
foramen primum, the upper part of
septum primum will breaks down to
form the foramen secondum (between
the upper margin of septum primum
and the roof of primitive atrium),
allowing a free passage of blood flow
from right to left side.
REFER SLIDE 23 for pics - 41explain DEVELOPMENT OF SEPTUM SECONDUMA crescentic fold from the cephalic
wall of the primitive atrium grows
downward towards the septum
intermedium, but not fused with it. this is the septum secondum
REFER 23 for pic - 42explain the development of the foramen ovaleThe septum secondum lies to the
right side of septum primum. The
free concave edge of the septum
secondum begins to overlap the
foramen secondum.
• The new passage formed between
the right and left atrium is called
the foramen ovale
REFER 24 for pic - 43is the foramen ovale a simple orifice?The foramen ovale is NOT A
SIMPLE ORIFICE, but AN OBLIQUE PASSAGE - 44Before birth the pressure in the right atrium is higher because?1-The lungs are not
functioning
2-More oxygenated blood
reaches the right atrium
from the placenta via the
IVC. This allows the blood
stream to pass from right
atrium to left atrium
through the foramen ovale - 45What happens after birth?The pressure inside the left atrium
increases and exceeds that of the
right atrium because:
1-Stoppage of the placental
circulation
2- Exposure to cold, which
stimulates the respiration and
lung functions, more blood
reaches the left atrium (from
the lungs)
REFER 25 for pic - 46How are the annulus ovalis and foramen ovale formed?After birth The difference in the pressure
between the two atria presses the
septum primum against the
septum secondum and the two
septa become fused together, and
as a result of this:
• The lower edge of septum
secondum will form the annulus
ovalis .
• The septum primum will form the
fossa ovalis (the depression below
the annulus ovalis). - 47What does the interventricular septum consist of?Anatomically the IVS consists of:
1. Large muscular part and
2. Small membranous part - 48explain the Development of muscular part-A crescentic ridge arises from the
endocardium of the floor of
primitive ventricle. The ridge
increases in depth due to the force
of blood stream on its either side.
- An interventricular foramen
persist at the upper edge of the
muscular part
REFER 28 for pics - 49explain the development of the membranous part1. Dorsal & ventral atrioventricular
endocardial cushions (septum
intermedium).
2. Right and left bulbar ridges.
-This membranous part will close the
interventricular foramen
REFER 28 for pics - 50explain the DEVELOPMENT OF TRABECULAE CARNAE, PAPILLARY MUSCLES & CHORDA TENDINAE-Small cavities appear in the
myocardium, unite together to form
larger cavities, separated from
each other by ridges variable in
size that project into the interior
of the ventricle.
• These ridges will differentiate
into trabecullae carnae, papillary
muscles and chorda tendinae
REFER 29 for pics - 51explain DEVELOPMENT OF BULBUS CORDIS the caudal part near the primitive ventricle-Two bulbar ridges appear along the right dorsal and left ventral walls of the
bulbus cordis. These ridges grow toward
each other and unite together to form septum. This septum will divide the
bulbus cordis into: Anterior portion and posterior portion - 52what will the anterior portion form?forms the infandibulum of
right ventricle (smooth outflowing
part), gives origin to the
pulmonary trunk. - 53What about posterior portion?forms the aortic vestibule, the
part of left ventricle (smooth
outflowing part) just inferior to the
aortic valve. - 54The bulbar ridges are continuous cranially or cephalically with what?-with similar ridges in the truncus arterious.
-causes the development of the aortic and
pulmonary valves - 55HOW?Four endocardial cushions; right, left, anterior and posterior bulbar ridges are developed in the walls of the cephalic part of the bulbus cordis at its junction with truncus arteriosus.
- The right and left bulbar ridges grow and fused together to divide the orifice into :
• Anterior ( pulmonary ) orifice
• Posterior (aortic) orifice. - 56CONTINUATIONThe anterior and posterior bulbar ridges remain separated.
• Each of the aortic and pulmonary orifices has three cushions, which will develop into cusps of the corresponding orifice.
• At first, the cusps of the pulmonary valve are one anterior and two posterior and the cusps of the aortic orifice are two anterior and one posterior - 57what happens that this flips later?-As a result of rotation of the pulmonary trunk 45°, 2 cusps become anterior and one cusp posterior.
¨- As a result of rotation of the aorta 45° will lead to rearrangement of the cusps and become 2 posterior and one anterior cusps. - 58Explain development of the truncus arteriosusTwo bulbar ridges appear in the cephalic part of the truncus arteriosus. These ridges are located on the right superior
wall (right ridge) and on the left inferior wall (left bulbar ridge). The right ridge grows distally and to the left, while the left bulbar ridge grows distally and
to the right. - 59what happens to the two bulbar ridges then?undergo 180 spiraling, fuse together to
form spiral aorticopulmonary septum. - 60What happens at the caudal end of the truncus arteriosus?the spiral septum lies transversely & divides it into:
- Anterior part (pulmonary trunk)
- Posterior part (ascending aorta) - 61what happens At the middle part of truncus arteriosus?the spiral septum lies antero-posterior & divides it into:
-Left part (pulmonary trunk)
- Right part (ascending aorta) - 62what happens at the cranial part of the truncus arteriosus?the spiral septum lies transversely & divides it into:
- Anterior part (ascending aorta)
- A posterior part (pulmonary trunk)
REFER 34 for pics - 63BRSMF
- 64The arterial system develops from the?aortic arches and branches of the dorsal aorta
- 65What are aortic arch derivatives?-aortic arch 1,2 and 5 have no derivatives.
- AA1 because it disappears soon after development.
-AA2 because it stays only for the early development.
-AA3 gives rise to common carotid arteries and proximal part of the internal carotid arteries.
-AA4 gives rise to the aortic arch on the left and brachiocephalic artery and proximal part of the subclavian artery on the right.
-AA6 gives rise to proximal pulmonary arteries and ductus arteriosus. - 66How many branches does the dorsal aorta have?-3 branches
-Posterolateral branches
-Lateral branches
-Ventral branches - 67what do the posterolateral branches form?-forms the intercostal, lumbar,vertebral,ceervical,internal thoracic and epigastric arteries and the arteries to the upper and lower limbs.
- 68What do the lateral branches form?-renal,suprarenal and gonadal arteries.
- 69What do the ventral branches form?-vitelline artieries form the celiac (foregut), superior mesentric (midgut),inferior mesentric (hindgut) arteries
-umbilical arteries form a part of the internal iliac and superior visceral arteries. - 70Development of the venous systemthe venous system develops from the vitelline, umbilical and cardinal veins which drains into the sinus venosus.
- 71vitelline veins-return poorly oxygenated blood from the yolk sac
-right vein forms the hepatic vein, hepatic portal, sinusoids, ductus venosus,superior mesentric and inferior mesentric and splenic vein and part of the IVC.
-Left vein forms the hepatic veins and sinusoids and ductus venosus. - 72umbilical veins-carry well oxygenated blood from the placenta
-right vein degenerate during early development
-left vein forms the ligamentum teres hepatis - 73cardinal veins-return poorly oxygenated blood from the body of the embryo.
-anterior cardinal vein forms the internal jugular veins and SVC.
-Posterior cardinal vein forms a part of the IVC and common iliac veins.
-Subcardinal vein forms a part of the IVC,renal veins and gonadal veins.
-Supracardinal veins forma a part of the IVC, intercostal, azygos and hemiazygos veins. - 74Where does the fetus have oxygenated blood?in the placenta rather than lungs
and has three shunts to bypass lungs and liver partially:
1)Foramen ovale
2)Ductus arteriosus
3)Ductus venosus - 75Foramen ovale-opening in the septum secundum
-usually closes functionally at birth but anatomically later.
-Blood here flow from right atrium to left bypassing the lungs (pulmonary circulation) - 76Ductus arteriosus-derived from the 6th aortic arch
-it connect the bifurication of the pulmonary trunk with the aorta.
-Closes functionally soon after birth and anatomically requires several weeks.
-it then becomes the ligamentum arteriosum which connects the left pulmonary artery at its origin the pulmonary trunk to the concavity of the arch of the aorta
-shunts blood from pulmonary trunk to aorta, partially bypsassing pulmonary circulation - 77Ductus venosus-Shunts oxygenated blood from the umbilical vein (returning from placenta) to the IVC partially bypassing the liver (portal circulation)
-joins the left branch of the portal vein to the IVC and is obliterated to become the ligamentum venosum after birth. - 78Umbilical arteries-carry blood to the placenta for reoxygenation before birth.
-become medial umbilical ligaments after birth, after their distal parts have atrophied. - 79Umbilical veins-carry highly oxygenated blood from the placenta to the fetus.
-consists of the right vein, which is obliterated during embryonic period and the left vein which is obliterated to form the ligamentum teres hepatis after birth.
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- Flashcards on Embryology-CVS, created by Dana Ali on 07/10/2018.
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