Anatomy of the cardiovascular system

1. Development of blood vessels
Dr.Mohammed Mahmoud mosaed

2. VASCULAR DEVELOPMENT
• Bloodvessel development occurs by two
mechanisms:
• (a) Vasculogenesis in which vessels arise by
coalescence of angioblasts
• (b) Angiogenesis whereby vessels sprout
from existing vessels.
• The major vessels, including the dorsal aorta
and cardinal veins, are formed by
vasculogenesis. The remainder of the
vascular system then forms by angiogenesis

3. Arterial System
• Aortic Arches
• the aortic arches are six pairs and arise from the aortic
sac (the most distal part of the truncus arteriosus)
• Each arch enters to the corresponding pharyngeal arch
which develop during the fourth and fifth weeks of
development
• The aortic arches are embedded in mesenchyme of the
pharyngeal arches on each side and terminate in the right
and left dorsal aortae. (In the region of the arches, the
dorsal aortae remain paired, but caudal to this region, they
fuse to form a single vessel.)
• The aortic sac then forms right and left horns, which
subsequently give rise to the brachiocephalic artery and
the proximal segment of the aortic arch, respectively

7. Development of aortic arches
• By day 27;
• Most of the first aortic arch has disappeared,
although a small portion persists to form the
maxillary artery.
• Most of the second aortic arch soon
disappears. The remaining portions of this arch
are the hyoid and stapedial arteries.
• The third arch is large
• The fourth and sixth arches are in the process
of formation.

8. • With further development,
• The third aortic arch forms the common carotid artery
and the first part of the internal carotid artery. The
remainder of the internal carotid is formed by the cranial
portion of the dorsal aorta. The external carotid artery is a
sprout of the third aortic arch.
• The fourth aortic arch is different on the right and left
sides.
• On the left, it forms part of the arch of the aorta,
between the left common carotid and the left subclavian
arteries.
• On the right, it forms the most proximal segment of
the right subclavian artery, the distal part of which is
formed by a portion of the right dorsal aorta and the
seventh intersegmental artery

9. • The fifth aortic arch either never forms or
forms incompletely and then regresses.
• The sixth aortic arch, (the pulmonary arch),
On the right side, the proximal part
becomes the proximal segment of the right
pulmonary artery. The distal portion of this
arch disappears.
• On the left side, the proximal part becomes
the proximal segment of the left pulmonary
artery, the distal part persists during
intrauterine life as the ductus arteriosus.

15. changes occur along with
alterations in the aortic arch system
• A number of other changes occur along with alterations in the
aortic arch system:
• (a) the dorsal aorta between the entrance of the third and
fourth arches is obliterated
• (b) the right dorsal aorta disappears between the origin of the
seventh intersegmental artery and the junction with the left
dorsal aorta
• (c) cephalic folding, growth of the forebrain, and elongation of
the neck push the heart into the thoracic cavity. Hence, the
carotid and brachiocephalic arteries elongate considerably,
the left subclavian artery shifts its point of origin from the
aorta at the level of the seventh intersegmental artery to an
increasingly higher point until it comes close to the origin of
the left common carotid artery

16. changes occur along with
alterations in the aortic arch system
• (d) The course of the recurrent laryngeal nerves
becomes different on the right and left sides. Initially, these
nerves, branches of the vagus, supply the sixth pharyngeal
arches. When the heart descends, they hook around the
sixth aortic arches and ascend again to the larynx, which
accounts for their recurrent course.
• On the right, when the distal part of the sixth aortic arch
and the fifth aortic arch disappear, the recurrent laryngeal
nerve moves up and hooks around the right subclavian
artery.
• On the left, the nerve does not move up, since the distal
part of the sixth aortic arch persists as the ductus arteriosus,
which later forms the ligamentum arteriosum

18. Vitelline and Umbilical Arteries
• The vitelline arteries, initially a number of paired vessels
supplying the yolk sac, gradually fuse and form the arteries in
the dorsal mesentery of the gut. In the adult, they are
represented by the celiac, superior mesenteric, and inferior
mesenteric arteries. These vessels supply derivatives of the
foregut, midgut, and hindgut, respectively.
• The umbilical arteries, initially paired ventral branches of
the dorsal aorta, course to the placenta in close association
with the allantois. During the fourth week, however, each
artery acquires a secondary connection with the dorsal branch
of the aorta, the common iliac artery, and loses its earliest
origin.
• After birth, the proximal portions of the umbilical arteries
persist as the internal iliac and superior vesical arteries, and
the distal parts are obliterated to form the medial umbilical
ligaments.

19. Coronary Arteries
• Coronary arteries are derived from two sources:
• (a) Angioblasts distributed over the heart surface by
migration of the proepicardial cells .
• (b) The epicardium itself. Some epicardial cells
undergo an epithelial-to-mesenchymal transition
induced by the underlying myocardium.
• The newly formed mesenchymal cells then
contribute to endothelial and smooth muscle cells of
the coronary arteries. Neural crest cells also
contribute smooth muscle cells along the proximal
segments of these arteries.
• Connection of the coronary arteries to the aorta
occurs by ingrowth of arterial endothelial cells from
the arteries into the aorta. By this mechanism, the
coronary arteries “invade” the aorta.