lesson 12 Flashcards
During the early phases of development, the embryo is nourished through ___ ___ _ ___ secreted by the uterine glands into the uterine cavity.
diffusion from the fluid ;
However, as the size and complexity of the
embryo increases it soon needs a ____ ____
it soon needs a circulatory
system
The __ __ including the heart, arteries, veins, and blood begins to
develop as early as the __ ___ to meet the embryo’s needs.
The circulatory system ; third week of
gestation
the first functional organ system.
circulatory system
The formation of blood cells, called _____ ,
occurs in ____ overlapping periods.
hematopoiesis: three overlapping periods
First period is called in formation of blood cells?
mesoblastic period
Mesoblastic period occurs where?
The Yolk sac
Second period is called ____ in blood formation and these 2 organs in this period are the major blood-forming organs. What are those?
hepato-lienal period; liver and the spleen
Third period is called ____ in blood formation and the major organ in blood formation here is what?
medullary period; bone marrow
In the mesoblastic period, the first blood cells appear in the ___ ___ ___ ___ very early in development.
visceral
mesoderm of the yolk-sac wall
At first in mesoblastic period, __ __ are formed, these are spaces in the mesoderm occupied
with clusters of haemangioblasts.
blood islands
In the mesoblastic period, Outer cells
differentiate
into ____, forming endothelial cells,
and the inner cells into primitive __ __
angioblasts; primitive blood cells
In the mesoblastic period, Blood islands are spaces in the mesoderm occupied by clusters of _____?
Haemangioblasts
The blood islands coalesce (come together) and the
____ ____ form ___ establishing
the first vessels.
endothelial cells; tubes
In the mesoblastic period, what is established when coalesce of blood islands happen along with endothelial cells creating tubes?
The first vessels
vasculogenesis is the process of spontaneous ____ ____ formation.
blood
vessel formation
This process of spontaneous blood
vessel formation is referred to as
vasculogenesis
Vessels form new vessels by sprouting
a process referred to as
angiogenesis
In mesoblastic period, The first blood cells to be formed are ?
primitive nucleated erythrocytes
In mesoblastic period, Primitive _____ evolves within a few days into ____ ____ resulting in erythrocytes without nuclei.
Primitive erythropoiesis; mature erythropoiesis
Erythrocytes without nuclei is made or created when primitive erythropoiesis is evolved into ____ ____
mature erythropoiesis
In hepatolineal period, this specific period in blood formation starts at a crown rump length of __ mm in cattle
8 mm
In the liver, in hepato lineal period, these two are seen.
erythropoietic stem cells as well as megakaryocytes
In the ___, erythropoietic stem cells and megakaryocytes can be seen.
By __ mm, neutrophils are also formed.
liver; 12 mm
neutrophils are seen to be formed in what period?
hepato-lineal period
In hepato-lineal period, the ___ becomes the most prominent hematopoietic organ in cattle embryos, up to the 5th month of pregnancy.
liver
In hepato-lineal period, what month does the liver’s blood forming activity declines and at birth it has ceased?
6 month
The liver is the most prominent hematopoietic organ in what animal embryo? And in up to how many months in pregnancy does this occur?
cattle embryos, 5th month of pregnancy/gestation
In hepato-lineal period, this organ is active in hematopoiesis from the third to ___ month of cattle pregnancy.
spleen; seventh (7th)
During the sixth month, in hepato-lineal period, the liver’s blood
forming activity _____ and at birth what will happens?
declines, ceased (stop)
In the medullary period, __ __ begins its
hematopoietic activity at a crown-rump
length of about __cm during the 4th
month of pregnancy in cattle.
bone marrow; 18 cm
In the heart, it develops from the horseshoe shaped ___ ___ after embryonic folding.
cardiac tube
Moreover, within what cavity of the embryonic disc did the cardiac tube got repositioned?
within the pericardial
cavity
Embryonic heart beats begin at:
Day 22 of pregnancy in the –
Day 23 in the – and –
Day 24 in the —
pig;
dog & cattle;
horse
In loop formation, the cardiac tube will become this type of shape, with the loop of pointing what way?
U-shaped; pointing ventrally
The cardiac tube
undergoes first a __ ___and then an internal division.
Loop formation
In the developing heart, the sinus venosus and atrium are initially not enclosed within the _________ but gradually become enveloped by it.
pericardium
The curved portion of the _________ develops into the future left ventricle.
ventricle
The curved portion of the _________ develops into the future right ventricle.
bulbus cordis
