Download Embryology Vasculature 2008

Embryology vasculature - notes 2008
Describe the development of the vasculature
All arteries form from mesoderm.
Aortic Arches: During the 4th and 5th weeks of development pharyngeal arches from at the cranial end of the
embryo and each of the arches receives a blood vessel. The aortic arches are shown in the picture below on the
left they form 6 loops that are all connected to the dorsal aorta, these eventually fuse. Sometimes arch five does
not form at all, other times it is reabsorbed. Arch I and II give the vessels in the head and neck. III give the
common carotids, external carotids. IV on the right gives the subclavian IV on the left gives the segment of the
arch of aorta. VI on the right gives the pulmonary artery, VI on the left gives the pulmonary artery and ductus
arteriosus.
The picture on the right shows the circulation further along in development. The arch system loses its original
symmetrical form. Table 12.1 page 183 in the book lists the arches and arterial derivatives.
Arch
Arterial Derivatives
1
Maxillary arteries
2
Hyoid and stapedial arteries
3
Common carotid and first part of internal carotid arteries
4 Left side
Arch of the aorta from the left common carotid to the left
subclavian arteries
4 Right side
Right subclavian artery (proximal portion)
6 Left side
Left pulmonary artery and ductus arteriosus
6 Right side
Right pulmonary artery
Vitelline and umbilical arteries: The vitelline arteries are paired vessels supplying the yolk sac. In the adult
these are the celiac, superior mesenteric and inferior mesenteric arteres. These vessels supply the foregut,
midgut, and hindgut. Blood travels from the heart to the placenta from the umbilical arteries.
Venous system: During the 5th week of development three systems of veins are present the vitelline, umbilical
and cardinal veins. These are symmetric. See slides 10-12. The Right umbilical vein shifts and connects to the
snus venosus then completely disappears. The left umbilical vein becomes the main channel from the placent to
the embryo. The network around the duodenum develops into a single velles the portal vein. The superior
mesenteric vein which drains the primary intestinal loop derives from the right vitelline vein. The umbilical
veins pass on each side of the liver, then some of the proximal part of both umbilical veins and the remainder of
the right umbilical vein disapper so the the left vein is the only one to carry blood from the placent a to the liver.
The ductous venosus forms between the left umbilical vein and the right hepatocardiac channel bypassing the
sinusoidal plexus of the liver. After birth this closes and becomes the ligamentum venosum.
Cardinal Veins
Symmetric system to start that provides drainage for most of the embryo. During the 5th to 7th weeks additional
veins such as subcardinal veins (drain kidneys), sacrocardinal veins (lower extremities) and supracardinal veins
(body wall and interal costal veins) are formed. The brachiocephalic vein develosps from the anterior cardinal
veins. The superior vena cava is formed by the right common cardinal vein and the proximal portion of the right
anterior cardinal vein. See page 188 for more details.
Describe circulation before and after birth. Before birth blood from the placenta returns to the fetus by way
of the umbilical vein, most of it bypassing the liver and flowing through the ductus venosus. Blood then goes to
the IVC then the right atrium, next it passes through the oval foramen and into the left atrium, blood then flows
to the left ventricle and ascending aorta ant this O2 rich blood flows to the heart and brain. Desaturated blood
from the superior vena cava flows through the right ventricle to the ductus arteriosus and into the descending
aorta and then to the umbilical arteries. At birth the umbilical arteries close forming the umbilical ligaments,
the foramen ovale closes forming the fossa ovale, the ductus arteriosus closes forming the ligamentum
arteriosum. Blood then flows as it does in adult circulation.
Case studies from class.
Newborn male with cyanosis has enlarged ventricles, aorta is shifted (over riding), pulmonary stenosis,
ventricle septal defect. This is the tetralogy of fallot.
Machinery sounding murmur on left side 2nd intercostal space (pulmonary valve). Here blood is flowing
between the pulmonary valve and aorta, there is a patent ductus arteriosus.
2 month old with congestive heart failure, rib notching on cxr, decreased pulses in lower extremities,
intercostals arteries are large. This is Coarctation of of the aorta.
Which structure is the O2% lowest in? The ductus arteriosus
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