Embryo 9 - Vasculature

What are the two processes of vascular development?

Vasculogenesis and angiogenesis

What is vasculogenesis?

Angioblasts coalesce to form major vessels

What is angiogenesis?

Sprouting of new vessels from existing vessels

What regulates angiogenesis?

Vascular Endothelial Growth Factor (VEGF)

Where do extraembryonic vessels initially form?

From the yolk sac during the 3rd week

What cells form blood islands?

Hemangioblasts

Where do hemangioblasts form blood vessels?

Within the yolk sac and lateral plate mesoderm

When do blood islands appear?

Week 3

Where do blood islands appear?

Mesoderm surrounding the yolk sac

How do the dorsal aortae form?

From blood islands bilaterally

What major structures are associated with the dorsal aortae?

Primitive heart tube and foregut

The dorsal aortae form by which process?

Vasculogenesis

What is the most likely diagnosis for a 14-month-old with a scalp mass?

Hemangioma

How many paired aortic arches initially form?

Six paired aortic arches

Where do the aortic arches arise from?

Aortic sac

Where do the aortic arches terminate?

Dorsal aortae

What happens to the 1st and 2nd arches by the end of week 4?

Large portions regress

What does Arch 1 form?

Maxillary artery (think 1st is max)

What does Arch 2 form?

Hyoid and stapedial arteries (think second for stapedial)

What does Arch 3 form?

Common carotid and internal carotid arteries (Think the 3rd letter in the alphabet is C for carotid)

Where do cranial portions of carotids come from?

Dorsal aortae

What are the external carotids?

Branches of the common carotid arteries

What does Arch 4 form on the right?

Right subclavian artery

What does Arch 4 form on the left?

Segment of the aortic arch

What happens to Arch 5?

Regresses / fizzles

Why does the right recurrent laryngeal nerve loop higher?

Right distal 6th arch regresses; nerve recurs around right subclavian artery

Where does the left recurrent laryngeal nerve loop?

Around the aortic arch

What is the 6th aortic arch called?

Pulmonary arch

Right proximal portion of Arch 6 forms what?

Right pulmonary artery (think RP RP)

Right distal portion of Arch 6 does what?

Regresses

Left proximal portion of Arch 6 forms what?

Left pulmonary artery (think LP LP)

Left distal portion of Arch 6 persists as what?

Ductus arteriosus

Know the development of the aortic arches figure

What is the ductus arteriosus?

A structure in embryo connecting the pulmonary trunk to the aorta.

Acts as a shunt - prevents blood from going back to lungs and instead dumps it back into aorta.

What does a machine-like murmur at the left 2nd intercostal space suggest?

Patent ductus arteriosus

Dysphagia with aberrant vessel—most likely cause?

Aberrant right subclavian artery

Where do the vitelline arteries arise from?

arise from abdominal aorta and supply derivatives of the yolk sac

Vitelline arteries give rise to which vessels?

Celiac and superior mesenteric arteries

What do umbilical arteries form via secondary connections?

Common iliac arteries, internal iliac (proximal), superior vesical arteries (proximal)

Basically vessels in the pelvis

What do regressed umbilical arteries become?

Medial umbilical ligaments

By week 5, what three paired veins exist?

Umbilical, vitelline, cardinal veins

Where will vitelline veins carry blood from?

yolk sac (GI tract) to the sinus venosus

Where will umbilical veins carry blood?

carry oxygenated blood from the placenta to the embryo (through umbilical cord)

Where will cardinal veins drain blood from?

Cardinal veins: principle veins of the embryo, drains body wall, trunk, limbs, head and neck

drain blood from the embryo and deliver it to the R. side of the heart

What does the left horn eventually develop?

coronary sinus

What does the right common cardinal vein become?

superior vena cava (SVC)

What does the right vitelline vein form?

Inferior vena cava (IVC)

What happens to the umbilical veins?

Right regresses; left carries blood from placenta to liver

What does the left vitelline vein form?

Portal vein

What is the sinus venosus?

bottom of the embryonic heart, collects all the venous blood from the embryo (send it to right atrium)

What is the function of the ductus venosus?

A shunt at the end of the umbilical cord which allows blood coming from the placenta to bypass the liver and empty directly into the IVC

allows nutrient rich blood to reach the brain and face

How is the portal vein formed?

Vitelline vein network around the duodenum coalesces into a single portal vein

Superior mesenteric vein derives from which embryologic vessel?

Right vitelline vein

Which structures arise from vitelline veins?

i. small region of the IVC (see below)

ii. portal vein

iii. ductus venosus

iv. hepatic

v. superior mesenteric

vi. inferior mesenteric

vii. splenic

Think Stressed People Don’t Have Sex In School

What do cardinal veins do?

Main venous drainage of embryo

What do anterior cardinal veins drain?

Cephalic portion

What do posterior cardinal veins drain?

Rest of embryo

Anterior cardinal veins form which adult vessels?

Internal jugular veins (drain the head)

Which veins form between weeks 5-7?

Subcardinal, sacrocardinal, supracardinal veins

What do subcardinal veins drain?

Kidneys

What do sacrocardinal veins drain?

Lower extremities

What do supracardinal veins drain?

Body wall

What veins drain the embryonic kidney and what will they become?

the posterior cardinal veins play a major role in draining the embryonic kidney

as the embryonic kidney regresses so does the blood supply; the vast majority of the posterior cardinal veins disappear

as a result the supracardinal veins take on the role of draining the body wall and become the azygos system of veins

What segments make up the IVC?

Hepatic, renal, sacrocardinal

How is the left common iliac vein formed?

anastamosis between sacrocardinal veins

What are the five components of fetal circulation?

Umbilical vein, ductus venosus, oval foramen, ductus arteriosus, umbilical arteries

What does closure of umbilical arteries form?

Medial umbilical ligaments

Closure of umbilical vein forms what?

Ligamentum teres hepatis

Closure of ductus venosus forms what?

Ligamentum venosum

Closure of ductus arteriosus forms what?

Ligamentum arteriosum

Closure of oval foramen forms what?

Fossa ovale

When does the lymphatic system begin forming?

Around week 6

Lymphatics are derived from what germ layer?

Mesoderm

How many lymphatic sacs form?

Six sacs

What are the six lymphatic sacs?

2 jugular, 2 iliac, 1 retroperitoneal, 1 cisterna chyli

Where does lymph ultimately drain?

Thoracic duct -> left jugulovenous angle

What is patent ductus arteriosus (PDA)?

Persistent connection between the pulmonary artery and aorta after birth.

What is coarctation of the aorta?

Congenital narrowing of the aorta.

What are the key features of infantile coarctation of the aorta?

Symptomatic in early childhood, tubular hypoplasia of the aortic arch, occurs proximal to a PDA.

What are the key features of adult coarctation of the aorta?

Narrowing opposite a closed ductus arteriosus, distal to the great vessels from the aortic arch.

What is the chest radiograph finding in coarctation of the aorta?

Figure 3 sign.

What causes dysphagia lusoria?

Abnormal origin of the right subclavian artery results in compression of the esophagus -impairment of swallowing

What is a double aortic arch?

Persistence of both right and left aortic arches forming a vascular ring.

What is congenital lymphedema?

Dilation or congenital hypoplasia of lymphatic channels.

What is a cystic hygroma?

Large fluid-filled swellings involving jugular lymph sacs that fail to connect to lymphatic vessels.