Flashcards in Embryo DSA Deck (23):
Produced by mesoderm?
-The cartilaginous, muscular, and connective tissue components of the trachea and lungs are derived from splanchnic mesoderm surrounding the foregut
Produced by endoderm of the gut tube?
Describe the separation of the respiratory and GI systems. What is the most common congenital abnormality associated with improper separation of the esophagus and trachea?
Esophageal atresia with or without tracheoesophageal fistulas (TEFs)
-Upper esophagus ends in a blind pouch and the lower segment forms a fistula with the trachea
What abnormality of the amniotic fluid, may be an indicator of esophageal atresia and how it is usually detected?
Polyhydramnios-in some types of TEF the amniotic fluid when swallowed does not pass to the stomach and intestines
-Often detected via an ultrasound
Describe the branching pattern of the lung buds to primary, secondary, and tertiary segmental bronchi (when does each division occur?)
Primary (Main bronchi)-5 weeks
Secondary (Lobar)-6 weeks
Tertiary (segmental)-8 weeks
Compare and contrast the stages of lung development.
-At which stage is viability possible?
Canalicular stage (17-26 weeks)
What are the functional requirements that must be met for preterm infants to survive?
Need sufficient numbers of mature alveolar sacs and capillaries are present to guarantee adequate gas exchange
Explain the function of type I alveolar cells/pneumocytes
Thin cells that line alveolar sacs so surrounding capillaries can protrude into the sacs causing intimate contact between the epithelial and endothelial cells-***makes up blood-air barrier***
Explain the function of type II alveolar cells/pneumocytes
Produce surfactant-a phospholipid-rich fluid capable of lowering surface tension at the air-alveolar interface
Explain the role of surfactant and macrophages in preparation for labor and delivery (clinical correlate!)
As the concentration of surfactant increases some enters the amniotic fluid and acts on macrophages causing these macrophages to migrate across the chorion into the uterus where they begin to produce immune system proteins (IL-1b)-->prostaglandin production-->uterine contractions
Explain why the fetus engages in breathing movements in utero
-They cause aspiration of amniotic fluid
-Surfactant coat prevents development of an air-water (blood) interface with high surface tension that would cause the alveoli to collapse during expiration (atelectasis)
-These movements are also important for stimulating lung development
Explain the development of the tracheoesophageal (respiratory) diverticulum
-Which signaling molecules and transcription factors specify its position, growth, and development?
Appearance and location of the lung bud are dependent on retinoic acid
Retinoic acid causes an upregulation in TBX4
Explain how ectopic lung buds form
-Arise from the trachea or esophagus
-Formed from additional respiratory buds of the foregut that develop independent of the main respiratory system
Describe the primitive body cavity
-Located in between?
-Located in between the somatopleure and the splanchnopleure layers of lateral plate mesoderm
Describe how the primitive body cavity is subdivided into pleural, pericardial, and peritoneal cavities
-Intraembryonic coelom is a continuous space
-Divide into thoracic cavity and abdominopelvic cavity
-Further divided thoracic cavity into 1 pericardial cavity and 2 pleural cavities
-***Pleuropericardial membranes and diaphragm***
Explain the role of surfactant in preparation for labor and delivery (clinical correlate!)
-When surfactant is insufficient?
Surfactant is particularly important for survival of the premature infant
When surfactant is insufficient, high tension results causing alveoli to collapse-->respiratory distress syndrome
Treatment for respiratory distress syndrome?
Treatment of preterm babies with artificial surfactant as well as treating the mother with premature labor with glucocorticoids to stimulate surfactant production
-Low volume of amniotic fluid
-Renal agenesis and obstructive uropathy
-Complications-pulmonary hypoplasia and limb defects
Congenital Diaphragmatic Hernias
-Most common on which side?
-Herniation of abdominal contents into pleural cavity
-Caused by failure of pleuroperitoneal membranes to fuse with other components
-Most common on the left posterolateral side
-Clinical signs-unusually flat abdomen, breathlessness, and cyanosis
How are esophageal atresia and tracheoesophageal fistula diagnosed?
When fed, these infants swallow normally but begin to cough and struggle as the fluid returns through the nose and mouth