Transcript Circulatory System - Auburn University

DEVELOPMENT OF THE
CIRCULATORY SYSTEM
and the structures that carry it
I. Develops relative to embryo’s needs
A. During early development diffusion of oxygen, wastes,
nutrients, etc. suffices
B. As embryo grows larger, metabolic needs increase,
diffusion no longer sufficient.
C. Circulatory system begins to develop
II. First evidence of
circulatory structures seen in
yolk sac, extraembryonic
splanchnic mesoderm - area
opaca vasculosa - blood
islands
(primitive blood cells
and blood stem cells)
III. Blood stem cells - where do they come from?
A. Sites of production from stem cells change as the human
embryo develops.
1. At 4 weeks after fertilization - stem cells are located
in the extraembryonic splanchnic mesoderm of
the yolk sac.
2. At 5 weeks - in body mesenchyme of embryo.
3. At 6 weeks - in developing liver.
4. At 8-16 weeks - in developing spleen, thymus and
lymph nodes.
5. At 16 weeks and beyond - in bone marrow
B. Evidence suggests there are two different sources for blood
stem cells.
1. Initially from the extraembryonic splanchnic mesoderm of
the yolk sac, and then migrate into the embryo.
a. “Primitive stem cells”
b. Produce mature erythrocytes that have a nucleus.
2. Later in development a new population of stem cells arises.
Recent research suggests that these stem cells arise from
endothelial cells that line the aorta.
a. By 16 weeks of development these stem cells populate the
bone marrow
b. These cells are the blood stem cells that give rise to enucleate
erythrocytes (red blood cells).
IV. Circulatory system in mammals
A. Basic circulatory loop
arterioles
arteries
capillaries
ventricle
venules
atrium
veins
There are 3 major arcs (or loops) associated with the developing
embryo. 1. Embryonic, 2. Vitelline (yolk sac), 3. Allantoic
B. Basic adult mammalian circulation
C. Early embryonic circulation
D. How is the adult circulatory pattern established?
If we look at adult vertebrate species from primitive fish, to reptiles, to birds, to
mammals, there are gross structural differences in the pattern of circulation.
These differences are there to accommodate the specific adult needs (e.g. fish
have gills, mammals don’t).
These differences are so great, that if only the adult
circulatory system was used to establish taxonomic
classification, in some cases we would probably say that,
for example, fish and mammals are not related.
If we look at the embryonic circulatory systems of all
vertebrates, we find that they are basically the same.
The adult systems are derived from the basic embryonic
system such that they meet the needs of the adult.
Conversion of the early embryonic
circulatory system to the adult
configuration.
Involves:
A. Degeneration of some embryonic vessels or of
parts of embryonic vessels.
B. Hypertrophy of parts of some vessels.
C. Anastomosis (fusion) of some vessels.
D. Separations of single embryonic vessels into two.
E. Loss of connection between some vessels and in
some cases reconnection somewhere else.
F. Formation of new vessels.
Views from the ventral side of the animal
Right
Left
Right
Left
From Carlson, B.M. 1996. Patten’s Foundations of
Embryology. McGraw-Hill, Inc. New York. 6th
edition. p. 618
Right
Left
human
in the embryo
Right
Left
trunku
trunkus
truncus
4
4th
s
brachiocephalic
artery and
pulmonary trunk
pulmonary
trunk
trunkus
truncus
systemic trunk and ascending aorta
The conotruncus
Fate of the Truncus Arteriosus
Contributes to the systemic trunk and a portion of the pulmonary trunk.
Conus
Divided into the bases of the pulmonary and systemic trunks
green - dorsal aortic roots
purple - 3rd aortic arches
red - 4th aortic arches
Modified from Carlson, B.M. 1996.
Patten’s Foundations of Embryology.
McGraw-Hill, Inc. New York. 6th
edition. p. 618
black - ventral aortic roots and trunkus arteriosus
orange - 6th aortic arches
yellow - conotruncus
blue - intersegmental arteries
These figures present a ventral view
Adult vessels
Right
Left
Right
Left
Color indicates
embryonic
derivation
green - dorsal aortic
roots
purple - 3rd aortic
arches
red - 4th aortic
arches
Brachiocephalic
artery
black - ventral aortic
roots and trunkus
orange - 6th aortic
arches
yellow - conotruncus
blue - intersegmental arteries
Vertebral artery
Subclavian artery
These figures present
a ventral view
Modified from Carlson, B.M. 1996.
Patten’s Foundations of Embryology.
McGraw-Hill, Inc. New York. 6th
edition. p. 618
Venous Circulation
Four Major Systems
1. Systemic (other than hepatic)
2. Hepatic
3. Pulmonary
4. Placental (Umbilical)
Conversion of the early embryonic circulatory
system to the adult configuration.
Involves:
A. Degeneration of some embryonic vessels or
their parts.
B. Hypertrophy of parts of some vessels.
C. Anastomosis (fusion) of some vessels.
D. Loss of connection between some vessels and
in some cases reconnection to another vessel.
E. Formation of new vessels.
Posterior Systemic circulation
Formation of the inferior vena cava
anterior
posterior
anterior
posterior
Adapted from Hopper, A.F. and N.H. Hart, 1985. Foundations of animal development. Oxford University press. New York, p. 434
Components of the inferior
vena cava
These figures present a ventral view
Green - anterior cardinal veins
Yellow - vitelline veins
Purple - common cardinal veins
Blue, blue - posterior cardinal veins
Olive - sinus venosus
Red, red - subcardinal veins
Orange - supracardinal veins
Hepatic segment
Mesenteric segment
Renal segment
Sub-/Supra-cardinal anastomosis
Adapted from Hopper, A.F. and N.H. Hart, 1985. Foundations of animal development. Oxford University press. New York, p. 434
These figures present a ventral view
Green - anterior cardinal veins
Yellow - vitelline veins
Purple - common cardinal veins
Blue, blue - posterior cardinal veins
Olive - sinus venosus
Red, red - subcardinal veins
Orange - supracardinal veins
(Mesenteric segment)
Internal iliac
Adapted from Hopper, A.F. and N.H. Hart, 1985. Foundations of animal development. Oxford University press. New York, p. 434
These figures present a ventral view
Green - anterior cardinal veins
Yellow - vitelline veins
Purple - common cardinal veins
Blue, blue - posterior cardinal veins
Olive - sinus venosus
Red, red - subcardinal veins
Orange - supracardinal veins
Adapted from Hopper, A.F. and N.H. Hart, 1985. Foundations of animal development. Oxford University press. New York, p. 434
portion between the right subclavian
and the left brachiocephalic vein
forms the right brachiocephalic
(innominate) vein.
Right
Left
Right
Left
http://education.yahoo.com/reference/gray/subjects/subject?id=135
(brachiocephalic)
anterior cardinal
veins
Common cardinal vein
Right
Left
Right
http://education.yahoo.com/reference/gray/subjects/subject?id=135
Left
(brachiocephalic)
anterior cardinal
veins
Common cardinal vein
Right
Left
Right
Left
Right
Right
brachiocephalic
Left
Right
Left
Right
Left
Right
Left
Right vitelline
vein
These figures present a ventral view
Green - anterior cardinal vein
Purple - common cardinal veins
Blue - posterior cardinal veins
Future Inferior
vena cava
Brown - sinus venosus
Orange - umbilical veins
Red - right vitelline vein
Yellow - left vitelline vein
Red/yellow speckles - anastomoses between
right and left vitelline veins
Right
Left
Adapted from Hopper, A.F. and N.H. Hart, 1985. Foundations of animal
development. Oxford University press. New York, p. 431
Ductus venosus:
Present at birth, but looses functionality within minutes.
Structurally closed 3-7 days after birth
Leaves a fibrous remnant in the liver called the ligamentum
venosum
Pulmonary venous system
The 4 pulmonary veins are not derived from pre-existing
embryonic veins.
They form de novo as the lungs develop and drain the capillary
beds of the lung tissue into the left atrium.
Initially the 4 pulmonary veins connect to a single trunk that
connects to the left atrium; however, as the embryo develops,
this trunk is incorporated into the wall of the left atrium.
By 8-9 weeks, this results in the 4 pulmonary veins that
originally connected to the common trunk, emptying separately
into the left atrium.
Umbilical Arteries
Develop as branches off the posterior dorsal aorta that extend
along the allantoic stalk out to the placenta.
Umbilical Veins
As the placental circulation develops, two umbilical veins
initially return blood from the placenta to the sinus venosus.
As development continues, the right umbilical vein degenerates
within the embryo and the placental blood ends up being returned
to the heart by the left umbilical vein via the ductus venosus.
This blood flow ceases at birth when the umbilical cord is cut.
Subsequently, the lumen within the left umbilical vein is
obliterated by cell growth from the walls and the remnant of this
vessel becomes the ligamentum teres hepatis = round ligament of
the liver.