Embroyology Flashcards
What is the first major system to develop in the embryo?
The cardiovascular system (CVS)
The early formation of the CVS is correlated with the urgent need for oxygen and nourishment.
During which week does primordial uteroplacental circulation develop?
3rd week
This development is critical for oxygen and nutrient supply to the embryo.
What structures appear during the 3rd week of heart development?
Angioblastic cords
These cords canalize to form endocardiac heart tubes.
What forms the tubular heart during the late 3rd week?
Fusion of two endocardiac heart tubes
This single primitive heart tube has a cranial (arterial) end and a caudal (venous) end.
When does the heart begin to beat?
Day 22-23
This marks the beginning of functional circulation in the embryo.
What separates the layers of the heart tube?
Cardiac jelly
The heart tube consists of myocardium, epicardium, and endocardium.
What are the five chambers of the primitive heart?
- Truncus arteriosus
- Bulbus cordis
- Primitive ventricle
- Primitive atrium
- Sinus venosus
These structures form the initial layout of the heart.
What is the function of the sinus venosus?
Receives blood from umbilical vein, vitelline vein, and common cardinal vein
It plays a key role in venous return to the primitive heart.
What is the bulboventricular loop?
A U-shaped bend formed due to faster growth of the bulbus cordis and ventricle
This configuration aids in the proper positioning of the heart structures.
What forms the AV canal?
The junction between the primitive atrium and ventricle
This structure is crucial for future separation of the atria and ventricles.
What are endocardial cushions?
Masses of tissue that form on the dorsal and ventral walls of the AV canal
They are essential for partitioning the AV canal into right and left AV canals.
What is septum primum?
A thin, crescentic shaped membrane that grows from the roof of the primordial atrium
It contributes to the formation of the right and left atria.
What is foramen ovale?
An opening that allows right to left shunt of blood before birth
Closure occurs due to increased left atrial pressure at birth.
What does the left horn of the sinus venosus become?
Coronary sinus
The right horn is incorporated into the wall of the right atrium.
What is an Atrial Septal Defect (ASD)?
A congenital heart anomaly present in 10-15% of patients
It is more commonly observed in females than males.
What is the interventricular septum?
A muscular ridge growing from the floor of the ventricle
It partitions the left and right ventricles.
What is a Ventricular Septal Defect (VSD)?
The most common type of congenital heart defect
Occurs more frequently in males and can be small or large.
What is Tetralogy of Fallot?
An abnormality resulting from unequal division within the conotruncal region
It consists of four cardiovascular alterations.
What is Persistent Truncus Arteriosus?
A condition where conotruncal ridges fail to form
This results in no division of the outflow tract.
What is the respiratory diverticulum?
A pouch-like structure formed from the laryngotracheal groove
It is the precursor to the lower respiratory organs.
What occurs during the canalicular period?
Terminal bronchioles divide into respiratory bronchioles and alveolar ducts
This phase occurs between 17-26 weeks of gestation.
What is the significance of the terminal sac period?
Intimate contact between epithelial and endothelial cells establishes the blood-air barrier
This allows for adequate gas exchange if the fetus is born prematurely.
What is tracheoesophageal fistula?
An abnormal connection between the lower esophagus and the trachea
It results from improper division of the foregut.
What terminates in a cluster of thin-walled terminal sacs?
Bronchiole
When do about 95% of alveoli develop?
Postnatally
What is a tracheoesophageal fistula?
An abnormal connection between the lower oesophagus and the trachea
What causes a tracheoesophageal fistula?
Improper division of the foregut by the tracheoesophageal septum
What is unilateral pulmonary agenesis?
Agenesis of lungs compatible with life
Where is an accessory lung typically located?
At the base of the left lung
What separates the thoracic from the abdominal cavities?
Diaphragm
From how many embryonic components does the diaphragm develop?
Four
What are the embryonic components that contribute to diaphragm development?
- Septum transversum
- Pleuroperitoneal membrane
- Dorsal mesentery of esophagus
- Body wall
What part of the diaphragm does the septum transversum form?
Central tendon
What does the dorsal mesentery of the esophagus form?
Right & left crus
What part of the diaphragm is formed by muscular ingrowth from the lateral body wall?
Posterolateral part (costal part)
What does the pleuroperitoneal membranes form in the diaphragm?
Small portion of diaphragm
At what week does the septum transversum appear as a mass of mesodermal tissue?
3rd week
What happens to the septum transversum at the 4th week?
Moves ventrocaudally forming a thick incomplete partition between thoracic & abdominal cavities
What connects to the diaphragm at the 6th week?
Dorsal mesentery of esophagus, pleuroperitoneal membranes, and body wall
Which somites contribute myoblasts to the diaphragm?
3rd, 4th, & 5th somites
What nerve is formed from the nerve fibers of the 3rd, 4th, & 5th cervical nerves?
Phrenic nerve
What type of supply does the diaphragm receive from the phrenic nerve?
Both motor & sensory supply
Which nerves provide sensory fibers to the part of the diaphragm derived from the lateral body wall?
Lower intercostal nerves
What is a congenital diaphragmatic hernia?
A posterolateral defect of diaphragm (foramen of Bochdalek)
What causes a congenital diaphragmatic hernia?
Defective formation and/or fusion of pleuroperitoneal membrane with other parts of diaphragm
What is the effect of a congenital diaphragmatic hernia?
Herniation of abdominal contents into thoracic cavity
What is eventration of diaphragm?
Half of diaphragm has defective muscles and balloons up into chest cavity
What occurs as a result of eventration of diaphragm?
Superior displacement of abdominal viscera
What is a congenital hiatal hernia?
Rare; abdominal viscera herniate through a large esophageal hiatus
What happens if the esophagus is shorter than normal?
Part of stomach may appear in the thorax and be constricted
What is a retrosternal or parasternals hernia?
A rare defect between sternum and sternocostal parts of diaphragm
