Lecture 20: Embryology of the Heart, Lungs, and Diaphragm Flashcards
What forms the right and left endocardial tubes and adjacent myocardial plates of the heart?
lateral plate mesoderm
What happens with the two endocardial tubes and myocardial plates
they come together to form one heart tube
What are the two layers of the heart tube?
endocardial layer surrounded by a myocardial layer
Describe the movement (looping) of the heart tube during the first few weeks of embryogenesis
structures forming the right side of the heart (right atrium and ventricle) swing anteriorly and the left swings to the posterior
What is septation
The creation of two atria and ventricles and divides the AV canal and ventricular outflow from aorta and pulmonary trunk
What is created first the atrium or ventricles?
They are made simultaneously
What forms the AV valves (tricuspid and mitral)
endocardial cushion
What forms the aortic and pulmonic semilunar valves?
Endocardial cushion
Embryological derivative of the medial wall of left atrium
septum primum
Embryological derivative of the medial wall of right atrium
septum secundum
Ostium primum
hole in the septum premum that leads into the AV canal
What closes the ostium primum
endocardial cushion
Ostium secundum
Forms in the septum premium as osmium primum closes
What closes ostium secundum
septum secundum
What happens to the growth of the septum secundum once the ostium secundum closes
It stops growth
When septum secundum stops growing, what forms
foramen ovale
Role of foramen ovale
Shunts blood from the right atrium to the left atrium
Left heart hypoplasia
premature closing of foramen ovale
What forms the membranous portion of the inter ventricular septum
endocardial cushion
Ostium primum atrial spetal defect
inadequate development of the cushions can cause failure of final closure of the atrial septum
Membranous ventricular septal defect
inadequate development of the cushions can cause failure of final closure of the ventricular septum
Persistent AV canal
most severe defect involving the endocardial cushion
Ventricular septal disease (VSD)
When the muscular and membranous inerventricular septa do no fuse together
Defects in septation are often accompanied by…Why?
Defects in the heart because anything that alters blood flow will affect the path or volume of flow
Example of how defects in aorticopulmonary septation results in ventricular septal defects underlying one or both great vessels
Tetralogy Fallot
Describe the 4 defects from Tetralogy Fallot
(OVEN). Overriding aorta, Ventricular spetal defect, Pulmonary stenosis (narrow right ventricular outflow tract), Right ventricular hypertrophy (due to higher pressures on the right side of the heart)
What do the aortic arches arise from
aortic sac
Right and Left aortic arch IV
Right: Right subclavian a.
Left: Arch of aorta
Connection between the recurrent laryngeal branches and aortic arch IV
The recurrent branches recur around aortic arch IV
Aortic Arch VI
Right and left pulmonary arteries and ductus arteriosum on the left side
Structures in the respiratory tract that derive from endoderm?
Epithelial linings of
- larynx
- trachea
- bronchi
- bronchioles
- terminal alveoli
what structures in the respiratory tract derive from splanchnic mesoderm?
The cartilage, muscle, and CT components of:
- trachea
- lungs
- pulmonary blood vessels
Where is there open communication between the respiratory divritiulum and forget in the embryo
Trachea (respiratory divriticulum) and the esophagus (forgut)
Which is located more anterior the esophagus or trachea
trachea
Tracheoesophageal fistula
esophagus ends in a blind pouch (baby throws up food)
What does the main stem of the lung bud (respiratory divriticulum) form
trachea
Where do the bronchial buds come from?
lateral outpocketings of the lung buds
What do the bronchial buds form
mainstem (or primary) bronchi
How many secondary bronchus are formed by the right mainstream bronchi? left?
Right: 3 (one per lobe)
Left: 2 (one per lobe)
Type II pneumocyte
type of cells derived from endoderm in the alveolar ducts and alveoli. Produces surfactant
What is the role of surfactant
prevents lungs from collapsing during expiration
Respirtory Distress Syndrome (RDS)
happens in some premature infants due to inadequate levels of surfactant in lung airways
What structures of the diaphragm derived from somatic lateral plate mesoderm
- Septum transverum
- Pleuroperitoneal membranes
What structures of the diaphragm derived from myoblasts
skeletal muscle cells
What structures of the diaphragm derived from mesenchyme surrounding the forgut
dorsal mesentery of esophagus
What did the crura of the diaphragm arise from
dorsal mesentery of esophagus
Which portions of the respirator system derived from the forgut?
Trachea, bronchi, alveoli, alveolar ducts
How does splanchnic mesoderm contribute to the formation of the lungs
All cartilage, muscle, and CT in the trachea and lungs developed from splanchnic mesoderm
How can the esophageotrachea fistula form
An abnormal separation between the trachea and the esophagus uses the esophagus to end in a “blind pouch”
What are the cellular derivatives of endoderm in the bronchial tree/lung
Epithelial singing of larynx, trachea, bronchi, brochioles, terminal alveoli
How is the diaphragm formed?
Septum transversum, pleuroperitoneal folds, mesoesophagus, myoblasts (skeletal muscle)
Where are defects in the diaphragm normally found and why?
In the pleuroperitoneal folds because the pleura and peritoneum fail to fuse
Basic formation of the heart
Lateral plate mesoderm forms two endocardial tubes and two adjacent myocardial plates. These come together to form one heart tube with and endocardial and myocardial layer.
What is the endocardial cushion? What is its clinical significance?
Forms the tricuspid, mitral, pulmonic, and aortic valve. When there is a deficiency in the endocardial cushion many clinical issues arise (i.e osmium premum atrial septal defect or membranous ventricular septal defect).
How is the intertribal septum formed
endocardial cushion
What is a common defect of the interatrial septum
Persistent AV canal
What is the Tetrology of Fallot
Septum dividing the aorta and pulmonary artery is displaces resulting in the 4 defects: Over-riding aorta, ventricular septal defect, pulmonary stenosis, and right ventricular hypertrophy
What are the aortic arches
IV and VI left and right
What is derived from the 4th aortic arch on the right and left side
Right: Subclavian a.
Left: Arch of aorta
What is derived from the 6th aortic arch
Pulmonary arteries (ductus venosum on the left)
