Embryology of the Respiratory and Cardiovascular Systems Flashcards
Early phase of lung development
Positioning of lung primordial and primary lung bud formation
Late phase of lung development
Mechanism of bronchial branching and cytodifferentiation
Lung development begins in week ___ with formation of ______
4th, with formation of laryngeotracheal (respiratory) diverticulum
The lungs develop as an outgrowth of _____ (____) into the surrounding splanchnic mesoderm
Foregut (future esophagus)
Laryngeotracheal diverticulum grows distally. Separated form esophagus (dorsally) by _______
tracheoesophageal septum
What is the most common malformation of the lung development
Tracheoesophageal fistula
Abnormal communication between trachea and esophagus
Tracheoesophageal Fistula
What causes tracheoesophageal fistula
improper formation of tracheoesophageal septum
What is the most common form of Tracheoesophageal fistula
esophageal atresia with distal tracheoesophageal fistula (87% of cases)
Polyhydramnios are associated with
CNS anomalies and esophageal atresia (including TEF)
Esophageal atresia and Tracheoesophageal fistula are suspected with the presence of
- an infant with excessive drooling that is frequently accompanied by choking, coughing, and sneezing.
- When fed, these infants swallow normally but begin to cough and struggle as the fluid is regurgitated
- The infant may become cyanotic and may stop breathing as the overflow of fluid form the blind pouch is aspirated the trachea and lungs
In week ____, the the left and right lung buds divide into
2 bronchial buds, these will become the main or primary bronchi
The splanchnic mesoderm differentiates into the ____, ___, and ____ of the lungs
smooth muscle, nerves, and blood vessels of the lungs
Stages in lung development
- Embryonic- 4-7 weeks
- (Pseudo)Glandular- weeks 8-16 weeks
- Canalicular- weeks 17-26
- Terminal sac- week 26 —> birth
- postnatal (alveolar)
when is the embryonic stage of lung development
weeks 4-7
When is the Pseudoglandular stage of lung development
weeks 8-16
When is the Canalicular stage of lung development
weeks 17-26
When is the Terminal sac stage of lung development
week 26 to birth
When is the alveolar stage of lung development
postnatal (after birth)
what happens in the embryonic stage of lung development
- initial formation of respiratory diverticulum up to formation of all major bronchopulmonary segments
- lungs grow into pleural cavities
- differentiation of pleura
What happens in the (Pseudo) Glandular Stage (weeks 8-16) of lung development
- Major formation and growth of duct system within bronchopulmonary segments
- No respiratory components, no gas exchange
- histological structure resembles a gland
what occurs in the canalicular stage (weeks 17-26) of lung development
- Formation of respiratory bronchioles and terminal sacs (primitive alveoli)
- Vascularization increases
- Capillaries found in walls
what are terminal sacs
- Alveoli- or terminal sacs- develop from respiratory bronchioles
- epithelium lining alveoli differentiates into two cell types
Function of Type I pneumoncytes
form part of blood-air barrier
What is the function of Type II pneumocyte
- secretory cells that produce surfactant
- Reduces surface tension
- Facilitates alveolar expansion
up to ___ % of alveoli formed after birth
90%
What is the primary mechanism of postnatal (alveolar) phase
alveoli are formed by separation of pre-existing alveoli
when is the viability period of the lungs
middle of the canalicular period
___% of Infant respiratory distress syndrome occur in infants born at less than 28 weeks gestation
60%
___% of cases of infant respiratory distress syndrome occur in infants born at less than 37 weeks gestation.
5%
Infant respiratory distress syndrome occurs primarily in the _____ lung
immature
Low surfactant can lead
lung collapse—> hypoxia—-> alveolar lining cell damage —-> pulmonary vasoconstriction —-> endothelial damage—–> fibrin hyaline membranes
What is pulmonary agenesis
- complete absence of lungs, bronchi and vasculature
- bilateral or unilateral
- bronchial buds do not develop
What is pulmonary hypoplasia
- poorly developed bronchial tree
- Partial (small segment) or Total (entire lung)
Congential diaphragmatic hernia
- abdominal contents herniated into thoracic cavity
- caused by failure of pleuroperitoneal membranes to fuse with other components
- can cause pulmonary hypoplasia
- clinical signs: usually flat abdomen, breathless and cyanosis
- most common on the left posterolateral side
Primitive vertebrate cardiovascular plan present by week ___
4
What is the first system in the human body to function
cardiovascular system
Why is early development of the cardiovascular system necessary for rapid growth
embryo can no longer meet nutritional or oxygen needs by diffusion
The heart is converted into a ____ chambered and then a ______
2 chambered and then 4-chambered structure
embryonic vascular system separates into ____ and ____ portions
systemic and pulmonary portions
(intra) embryonic circuit
- Series of aortic arches that connect to dorsal aortae
- D. Aortae subdivide into smaller vessels to supply embryo
- Blood drained by anterior and posterior cardinal veins
- Common cardinal vein
umbilical vein carries
oxygenated blood form the placenta
Vitelline circuit
supply and drain yolk sac - “nursery for blood cells”
extraembryonic vascular circuits
- nutritional circuits
- vitelline
- Umbilical
- Umbilical vein
Embryonic Dilation (Truncus Arteriosus) becomes what adult structures
- Aorta and pulmonary trunk
Embryonic dilation, Bulbus cords becomes what structures
- Smooth part of the right ventricle (conus cords), smooth part of left ventricle (aortic vestibule)
The embryonic dilation, primitive ventricle, becomes what structures
- Trabeculated part of right and left ventricles
The embryonic dilation, primitive atrium, become what adult structures
Trabeculated part of right and left atria (auricles)
The embryonic dilation, Sinus Venosus, becomes what adult structures
Smooth part of right atrium (sinus venarum), coronary sinus, oblique vein of left atrium
At day 22 the heart has
Truncus arteriosus and bulbus cordis, ventricle and atrium ,
(note that the Truncus arteriosus and bulbus cordis, ventricle grow faster than other regions)
around day 23 the bulbs cords and ventricle create a
bend
what is dextrocardia
the heart bends to the left instead of right. heart is displaced to the right with transposition of heart and great vessels. most common positional abnormality
after folding, atrium and ventricle are separated by ______
narrow AV canal
Dorsal and ventral blocks of cardiac tissue grow together known as
endocardial tissue
Primordial arterial and venous ends are brought together to form ______
transverse pericardial sinus
After folding, atrium and ventricle are separated by
narrow AV canal
The formation and fusion of the ____ is the critical first step in the development of the 4-chambered heart
endocardial cushions
Large communication between chambers occurs when
endocardial cushions fail to fuse
Formation of the interventricular septum
- Two parts
- Muscular portion develops in the midline on the floor of the primitive ventricle
- grows upward towards endocardial cushions and downgrading bulbar ridges
- it is then closed by a membranous portion that divides AV canals
Ventricular septal defects (VSDs)
- 25% of all congenital heart defects
- Most VSDs that require surgical correction occur in membranous portion
- Opening between L and R ventricles, associated shunting of blood
Formation of Atrial septum
- septum primum grows toward the endocardial cushions. There is then apoptosis that forms foramen secundum (note that foramen premium is still present but soon closes when septum primum grows into endocardial cushions. Septum secundum then forms from the top and endocardial cushions and does not come all the way together but instead ends when it meets the head of the seputm premium thus forming the valve of the foramen oval (before birth the right atrium has higher pressure and pushes this open but then after birth the left has more and closes it forming the fossa ovalis)
Atrial Septal Defects
- is fairly common , present in 10-15% of patients with congenital cardiac anomalies
- ostium (foramen) primum defects- similar to endocardial cushion defects
- secundum type- involve foramen ovale and septum primum
- Sinus venosus- usually near opening of SVC
- Common atrium
Major trends of heart development
- The heart is converted into a 2-chambered and then a 4-chambered structure
- Embryonic vascular circuit separates into systemic and pulmonary portions
- Systemic arterial outlow—> left
- Systemic venous return–> right
Liver develops in septum _____
Transversum
Vitelline veins become incorporated into liver as _____, ____, ____, part of ____ and some of the veins that ______
hepatic sinusoids, hepatic veins, part of IVC and some of the veins that drain the GI tract
- The umbilical vein is able to bypass the ___ and diverts oxygenated blood into the heart
liver
The umbilical vein joins the ______, which connects umbilical vein to IVC
large venous shunt ductus venosus
_____ connects umbilical vein with IVC
ductus venosus
The ductus venosus bypasses the ____ and diverse oxygenated blood into the heart
liver
What happens to the cardinal veins after fetal life
- anterior cardinal veins become connected
- anastomosis becomes left brachiocephalic vein
- Right anterior cardinal and common cardinal become SVC
_____ cells invade ridges that form in the bulbus cords and truncus arteriosus
Neural crest cells
What is the tetralogy of fallot
- associated with: pulmonary stenosis, VSD, Overriding aorta, right ventricular hypertrophy
Patent ductus arteriosus
- an abnormal connection between the aorta and the pulmonary artery in the heart. About 3,000 newborns are diagnosed with PDA each year in the U.S.
