9- Heart Development Flashcards
These are the most common life-threatening birth defects. They comprise 20% of all congenital defects in live births. Causes include:
- 4% single gene mutations
- 6% chromosomal anomalies
- 5% teratogens
- 85% multifactorial
Heart Defects
This is the process of making blood vessels directly from mesenchyme.
Vasculogenesis
***Remember, mesenchyme is embryonic CT derived from neural crest and mesoderm!
At day 17, vasculogenesis starts at the mesoderm that is adjacent to the endoderm of the yolk sac wall and is coupled with ________, which is blood cell formation
hematopoiesis
Describe how a blood island is formed
Hemangioblasts will differentiate and give rise to hematopoietic progenitor cells and endothelial precursor cells
These cells all organize together to form a blood island
How do blood islands form an initial vascular network?
They coalesce, lengthen, and interconnect
By the end of the ____ week, you have a vascularized yolk sac wall, connecting stalk, and chorionic villi
3rd
What are the sites of hematopoiesis?
Blood islands of the yolk sac
liver
aortic-gonadal-mesonephric region
lymph organs
bone marrow
Embryonic hematopoietic cells appear about day ____ and go on to populate and reside in the developing liver primordia by day _____.
17
populate liver by 23
What do embryonic hematopoietic stem cells go on to be?
embryonic erythrocytes
macrophages
megakaryocytes
Where are the definitive hematopoietic stem cells programmed?
hemogenic endothelial cells of the dorsal aorta in the aortic-gonadal-mesonephric region (AGM)
Describe hematopoietic stem cells…
- When do they “seed” the liver
- What do they do when they get there?
- day 30
- They give rise to the myeloid and the lymphoid stem cell lineages that are able to go and populate the lymph nodes and the bone marrow
The AGM regions appears on day ____ and disappears by ____
27
40
T/F: blood vessel formation in the embryo is NOT coupled with hematopoiesis
TRUE
Where does the initial blood vessel formation occur (in what embryonic layer)?
What is another place that intraembryonic vasculogeneis can occur? (migrate to form vessels outside the splanchnic mesoderm)
Intraembryonic splanchnopleure mesoderm
Paraxial mesoderm
Describe the overall process of intraembryonic vasculogenesis
- intraembryonic splanchnic mesoderm differentiates into endothelial precursor cells
- these can proliferate and differentiate into endothelial cells
- endothelial cells organize into small cords and coalesce to form long tubes
- angiogenic plexus continues to grow
What are the steps that an angioplasties plexus is able to grow and spread?
- continued proliferation of the endothelial precursor cells
- angiogenesis (forming new vessels)
- intusseption
- recruiting new mesodermal cells into the wall of existing vessels
_______ is the splitting of a blood vessel
intussusception
_______ is the budding and sprouting of new vessels from existing ones
angiogenesis
________ are caused by abnormal blood vessel and lymphatic growth
Angiomas
What are angiomas stimulated by?
abnormal levels of angiogenic factors
_______ is the excessive growth of a small capillary network
Capillary hemangioma
______ is the excessive growth of the venous sinus
Cavernous hemangioma
the ______ ______ ______ is the EPC clusters that are arranged in a horseshoe shape within the cariogenic area of the intraembryonic splanchnic mesoderm and the adjacent mesoderm
first heart field
Where does the intraembryonic coelom lie in relation to the first heart field?
Dorsal
As the anterior/posterior body folding occurs, the _______ _______ ______ and _____ become folded beneath the embryo, pulling some endoderm inside to form the foregut.
Primary heart field
coelom
After the anterior/posterior folding, where do the limbs of the heart field lie?
Ventral to the foregut and dorsal to the coelom
Describe the formation of the simple tubular heart
During anterior/posterior folding, the EPCs differentiate into endothelial cells and produce two primitive endocardial tubes
While this is happening, the lateral sides of the embryo start to move together and the two tubes will merge and fuse midline and also fuse with the cardiogenic mesoderm
** tubes–> merge–>fuse to cardiogenic–> boom tubular heart
What are the three pairs of vessels that allow the inflow of blood into the primitive heart?
- common cardinal veins
- Vitelline veins
- umbilical veins
Primary heart tube wall consists of:
1.
2.
3.
- Endocardium–inner epithelium continuous with blood vessels.
- Myocardium.
- Cardiac jelly– concentration of extracellular matrix between endocardium and
myocardium.
First rhythmic contraction begins about day ____
22
blood flow starts about day ____
24
What are the 5 things that make up the heart tube?
- Sinus venous
- Primitive atrium
3 AV region - Primitive ventricle
- Aortic sac or root
________ is made of partially confluent right & left sinus horns. Draining into each horn is an umbilical vein (placental blood–O2 enriched), vitelline vein (blood from gut area– venous blood), and common cardinal vein (venous blood from head and trunk) in the tubular heart.
Sinus venous
________ is region between sinus venosus and ventricle. Receives blood from sinus venous in the tubular heart.
Primitive atrium
_____________ is the region of heart separating the primitive atrium from primitive ventricle. Lumen of this region is called the atrioventricular canal or foramen in the tubular heart.
AV region
the _____ ______ is the portion between primitive ventricle and aortic sac in the tubular heart.
outflow tract
______ _____ is the common confluens of pharyngeal arch blood vessels. These will contribute to the great vessels. Present in the heart tube
Aortic sac or root
________ ________suspends the heart tube but eventually ruptures forming the transverse sinus seen in the adult
Dorsal mesocardium
What do the caudal remnants of the dorsal mesocardium form?
The proepicardial organ
Proepicardial cells eventual migrate over the surface of the myocardium forming the______
epicardium
epicardium is also known as the future ______
Visceral pericardium
_____ _____ is the first major step required for cardiac septation
cardiac looping
Prior to cardiac looping, describe the positioning of the atria and the ventricles
The ventricles are above the atria; the looping reverses these positions
Atrium moves _______ and ______ so it becomes located between outflow tract and dorsal pericardial wall while it enlarges.
cranially and dorsally
The initial outflow tract forms the future ____ ______
right ventricle
The outflow tract initially bends to ______, _______, and _______ during cardiac looping
right
ventrally and inferiorly