Cardiorespiratory Embryology Flashcards
When does the heart tube form?
In the third week of development 18-22 days
How is the heart tube formed?
Endocardial cells (angioblasts) differentiate from mesoderm and join to form a heart tube surrounded by myoblasts
As the heart tube expands how does the ventricular region move?
Ventrally, caudally and to the right
As the heart tube expands how does the atrial region move?
Dorsally, cranial and to the left
How do veins and aortic arches carry blood to the embryonic around 3.5 weeks?
A series of veins carry blood from the yolk sac (Vitelline veins), placenta (umbilical veins), and embryo (cardinal veins) to the heart
A series of aortic arches carry
blood from the heart to the paired dorsal aortae and then to the embryo
Some of the vessels degenerate, resulting in the normal anatomy of the great vessels
What are the single primitive atrium, ventricle, and outflow tract (truncus arteriosus) separated by and when does this happen?
Septa or walls between 27-37 days
What do the sinus venosus become?
What do pulmonary veins become?
Part become The sinus venarum of the right atrium while the proximal parts of the pulmonary veins become the smooth left atrium
When does the foramen primum form and how does it form?
At the end of the 4th week a septum grows from roof of the common atrium down toward the atrioventricular canal but it doesn’t form completely
How does separation of the atrioventricular canal occur?
It occurs when proliferating endocardial cells (called endocardial cushions) on the dorsal and ventral walls grow towards each other and fuse, separating the single opening into two
What tissue do the artioventricular valves form from?
Endocardial cushion tissue
How does septation of a ventricle occur?
By formation of a muscular and membranous septum.
How does the muscular part of the ventricular septum develop?
From myoblasts in the midline on the floor of the primitive ventricle and grows towards the fused endocardial cushions
What does the membranous part of the ventricular septum form from?
The fused endocardial cushions and the septum that separates the outflow tract
What is the most common congenital defect?
Membranous ventricular septal defect
When does septation of the outflow tract into the aorta and pulmonary tract occur?
Beginning in the 5th week when neural crest cells migrate into the endocardium of the truncus arteriosus
What do proliferating endochondral cells form?
They migrate to form the conotruncal (truncoconal) ridges
What is spiraling necessary for?
For the aorta to connect to the left ventricle and the pulmonary trunk to the right ventricle
What are the deficits in formation of the aorticopulmonary septum?
Persistent truncus arteriosus (no septum forms), transposition of the great vessels (the septum doesn’t spiral), and tetralogy of fallot (the septum form asymmetrically)
What are the three shunts that deliver oxygenated blood from placenta to embryo?
Ductus venosus, foramen ovals, and ductus arteriosus
What is the ductus venosus?
Shunts blood from the umbilical vein to the IVC, bypassing the liver
What is the foramen ovale?
Shunts blood entering the right atrium from IVC to left atrium
What is the ductus arteriosus?
Shunts blood from pulmonary trunk to descending aorta, bypassing the lungs where the pressure is high due to amniotic fluid in the lungs
Why do the shunts close after birth?
Partially due to pressure changes
How does the pressure change on the left heart following birth?
It increases because the lungs fill with air, blood flows to the lungs, and returns to the left atrium
How does pressure change on right side of heart following birth?
It decreases because the umbilical vein constricts
How does the foramen ovale close?
It closes due to the septum primium and secundum being pushed together by increased pressure in the left atrium
What does prostaglandin E2 from the placenta do?
It keeps the ductus arteriosus open
What does the hormone bradykinin do?
It constricts the ductus arteriosus
What replaces the ductus venosus after birth?
The ligamentun venosum
What replaces the foramen ovale after birth?
The fossa ovale
What replaces the ductus arteriosus after birth?
The ligamentum arteriosum
What structural developments occur during week 3-6?
Lung bud from the foregut branches to form tertiary (segmental) bronchi
What structural developments occur weeks 6-16?
This is the pseudogandular when bronchi branch to form terminal bronchioles
What happens in the canalicular period? In what weeks?
Weeks 16-26. Terminal bronchioles divide into respiratory bronchioles and alveolar ducts;surrounded by capillaries
When do pneumocystis develop?
Starting at 20 weeks
What structural developments occur during the saccular? During what weeks does this happen?
26-36 weeks. Alveolar ducts divide into terminal sacs (primitive alveoli) with type I and II pneumocytes
What structural developments occur in the alveolar? When does this occur?
Week 36-8 years. Alveoli increase, nature and have well-developed epithelial-endothelial contacts
What components of the airway gave endodermal origin?
The larynx, trachea, bronchi, and lungs
What is tracheoesophageal fistula?
Food and drink can enter the lungs from esophagus (abnormal connection)
What is esophageal atresia?
The esophagus ends and a blind-ended tube
What is respiratory distress syndrome?
It occurs when not enough surfactant in the lungs. Baby needs to work harder to breathe
What is surfacant made by?
Type II pneumocytes starting around 26 weeks of development and keeps alveoli from collapsing by decreasing surface tension
What is the path of the blood from the aortic arches in the embryo?
they carry blood from the heart to the paired dorsal aortae and then to the embryo.
How does the foamen secundum form?
Cell death in the septum primum
A second septum forms in embryology and gives rise to an opening called what?
The foramen ovale
How does septation of the ventricle occur?
By formation of a muscular and membranous septum.
How does the muscular part of the ventricular septum develop?
From myoblasts in the midline on the floor of the primitive ventricle and grows toward the fused endocardial cushions.
What is the most common congenital cardiac defect?
Membranous ventricular septal defect.
What two things does the truncus arteriosus become?
The proximal aorta and pulmonary trunk
What three things does the bulbus cordis become?
The conus arteriosus (RV), aortic vesitubule (LV), trabecularted right ventricle
What does the primitive ventricle become
The trabeculated left ventricle.
What two things does the primitive atrium become?
the trabeculated right and left atrium.
What does two things does the sinus venosus become?
smooth right atrium and coronary sinus.
What two things does loooping require?
cilia and dynein.
