Transcript These figures present a ventral view

DEVELOPMENT OF THE
CIRCULATORY SYSTEM
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 derived from extraembryonic splanchnic mesoderm of
the yolk sac.
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
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 2
or more species of vertebrates were 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.
Conversion of the early embryonic circulatory system to the adult
configuration.
Involves:
A. Degeneration of parts of some embryonic
vessels or their parts.
B. Hypertrophy of parts of some vessels.
C. Anastomosis (fusion) of some vessels.
D. Separation of one embryonic vessel into two.
E. Loss of connection between some vessels.
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
In the embryo
Right
Left
trunkus
44
4th
trunkus
pulmonarytrunk
trunk
pulmonary
systemic trunk
Right
Fate of the Trunkus Arteriosus
Contributes to the systemic trunk and a portion of the pulmonary
trunk.
Divided into the bases of the pulmonary and systemic trunks
Left
green - dorsal aortic roots
purple - 3rd aortic arches
red - 4th aortic arches
black - ventral aortic roots and trunkus arteriosus
orange - 6th aortic arches
yellow - bulbus arteriosus
blue - intersegmental arteries
RIGHT
(Seventh intersegmental)
Modified from Carlson, B.M. 1996.
Patten’s Foundations of Embryology.
McGraw-Hill, Inc. New York. 6th edition.
p. 618
These figures present a ventral view
LEFT
(Seventh intersegmental)
Adult vessels
Right
Left
Right
Color indicates
embryonic
derivation
green - dorsal aortic
roots
purple - 3rd aortic
arches
red - 4th aortic
arches
black - ventral aortic
roots and trunkus
orange - 6th aortic
arches
yellow - bulbus
arteriosus
blue - interseg-mental
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
Left
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.*
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
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.
http://education.yahoo.com/reference/gray/subjects/subject?id=135
anterior cardinal
veins
(brachiocephalic)
Common cardinal vein
http://education.yahoo.com/reference/gray/subjects/subject?id=135
28
anterior cardinal
veins
(brachiocephalic)
Common cardinal vein
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 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 this drainage is via a single trunk; 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 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 round ligament of the liver.