Lec.12 DEV'T OF CARDIOVASCULAR SYSTEM Flashcards
During the early phases of development, the embryo is nourished through diffusion from the fluid secreted by the ____ into the uterine cavity.
However, as the size and complexity of the embryo increases, it soon needs a circulatory system to distribute nutrients and oxygen and to remove carbon dioxide and metabolites.
uterine glands
The circulatory system, including the heart, arteries, veins and blood, begins to develop as early as the ____ week of gestation to meet the embryo’s needs.
The circulatory system is the first functional organ system.
third week
*Blood Cells
The formation of blood cells, ____, occurs in three overlapping periods.
The first, or mesoblastic period of blood- formation, occurs in the ____.
hematopoiesis’
yolk sac
*Mesoblastic Period
The first blood cells appear in the _____ of the yolk-sac wall very early in development.
At first, blood islands are formed, these are spaces in the mesoderm occupied with clusters of ____.
Outer cells differentiate into ____, forming endothelial cells, and the inner cells into ____.
visceral mesoderm
haemangioblasts
angioblasts
primitive blood cells
*Blood Cells
In the second period of hematopoiesis, ____, the liver and the spleen become the major blood-forming organs.
In the third period, ____, the bone marrow takes over as the major blood-forming organ.
hepato-lineal period
medullary period
*Mesoblastic Period
The blood islands coalesce and the endothelial cells form tubes establishing the first vessels.
This process of spontaneous blood- vessel formation is referred to as ____.
Vessels forms new vessels by sprouting – a process referred to as ____.
vasculogenesis
angiogenesis
*Mesoblastic Period
The first blood cells to be formed are ____.
Primitive erythropoiesis evolves within a few days into mature erythropoiesis resulting in erythrocytes without nuclei.
primitive nucleated erythrocytes
*Hepato-lineal Period
This period starts at a crown-rump length of 8 mm in what animal?.
In the liver, erythropoietic stem cells as well as megakaryocytes can be seen.
By 12 mm, _____ are also formed.
The liver becomes the most prominent hematopoietic organ in cattle embryos up to the ____ month of pregnancy.
cattle
neutrophils
5th month
*Hepato-lineal Period
During the ____ month, the liver’s blood-forming activity declines and at birth it has ceased.
The ____ is active in hematopoiesis from the third to the seventh month of pregnancy in cattle.
sixth month
spleen
*Medullary Period
The bone marrow begins its hematopoietic activity at a crown-rump length of about 18 cm during the month ____ of pregnancy in cattle.
This will be the main source of blood cells in adult animals.
4th month
*Heart
The heart develops from the ____ shaped cardiac tube after embryonic folding has repositioned it within the pericardial cavity ventral to the embryonic disc.
Embryonic heart beats begin at:
Day __ of pregnancy in the pig
Day __ in the dog and cattle
Day __ in the horse
horseshoe-shaped
Day 22 of pregnancy in the pig
Day 23 in the dog and cattle
Day 24 in the horse
*Loop Formation
To develop into the four-chambered mammalian heart, the cardiac tube undergoes first a loop formation and then an internal division.
The cardiac tube will become U-shaped with the loop of pointing ____.
ventrally
*Loop Formation
Throughout this process, the developing heart is beating at a rhythm set by pacemakers in the ____.
At first, this and the atrium are not enclosed within the pericardial cavity, but they gradually become enveloped by the ____.
sinus venosus
pericardium
*Loop Formation
During the enclosure, the atrium becomes positioned dorsal to the ventricle, and the loop takes on the shape of an S.
The curved portion of the ventricle develops into the ____ whereas the curved portion of the bulbus cordis develops into the ____.
future left ventricle
future right ventricle
Steps for formation of heart chamber:
Incorporation of the____ into the atrium
Division of the ____
Division of the ____
Division of the ____ and the ____
Division of the ____ and ____
sinus venosus
atrioventricular channel
atrium
ventricle and the bulbus cordis
conus cordis and truncus arteriosus
*Heart Chambers
At the atrioventricular channel, the inner cardiac wall develops anterior and posterior thickenings, the ____.
The cushions will grow until they meet and fuse in the midline of the canal, forming the ____.
This divides the channel into right and left _____.
endocardial cushions
septum intermedium
atrioventricular channels
*Heart Chambers
As the septum intermedium develops, a crescent-shaped fold, the ____ begins to form.
This separates the atrium into right and left components connected through a minor opening, the ostium primum
septum primum
*Heart Chambers
As the endocardial cushions grow towards the midline, the septum primum also grows, gradually closing the ____.
Before this closure, however, programmed cell death in the septum primum results in formation of the ____.
This allows continued blood flow from the developing right atrium to the left.
A second crescent-shaped fold, the ____, develops to the left of the ____.
ostium primum
ostium secundum
septum secundum
septum primum
*Heart Chambers
The transition between the ventricle and the bulbus cordis is marked externally by a ____ and internally by a muscular fold that develops into the muscular part of the interventricular septum, which grows towards the septum intermedium.
groove
*Heart Chambers
The primitive ventricles expels its blood into the conus cordis which forwards it to the ventral aortae through the ____.
To complete the division of the cardiac tube into right and left halves, the bulbus cordis and the truncus arteriosus also need to be divided into two channels.
truncus arteriosus
*Heart Chambers
Formation of two opposing cushions in the wall of these compartments will separate the flow of blood.
The cushions in the conus cordis fuse with those of the truncus arteriosus to form ____.
As they grow, the cushions fuse in the midline to form the ____ dividing the blood flow into two separate channels.
conu-truncal cushions
aorticopulmonary septum
*Arterial System
When the pharyngeal or branchial arches form, each arch receives its own cranial nerve and its own artery.
This results in the formation of six ____ between the dorsal and ventral aortae on each side.
arterial arches (aortic arches)
*Arterial System
All six aortic arches remain functional in fishes, while the ____ arches are largely rudimentary in mammals.
The ____ arch either remains rudimentary (as in the horse and pig) or never develops at all (as in cattle).
Only the ____ aortic arches form components of the developing circulatory system.
first and second arches
fifth arch
third, fourth and sixth aortic arches
*Arterial System
The ventral aortae develop into the ____ and, in the cranial region, into the external carotid arteries.
The cranial portions of the dorsal aortae develop into the ____.
The first aortic arch largely degenerates, but a small portion remains and forms the ____.
common carotid arteries
internal carotid arteries
maxillary artery
