Lecture 5 - Respiratory Embryology Flashcards
what does the endoderm of the laryngotracheal groove form
pulmonary epithelium, glands of larynx, trachea, and bronchi
what does the splanchnic mesoderm of the lateral plate form
CT, cartilage, smooth muscles; these surround the foregut
what does the laryngotracheal groove grow from
median outgrowth from the floor of the primitive pharynx
what does the laryngotracheal groove end up forming
laryngotracheal diverticulum aka lung bud
what does the lung bud or laryngotreacheal diverticulum form
respiratory bud
when does the respiratory bud birfurcate
days 26-28
what regulates the branching pattern of the lung endoderm
surrounding mesoderm
what do the primary bronchial buds form
early lungs and primary bronchi
when do the secondary bronchial buds form
beginning week 5
when do we see segmental bronchioles
week 7
what week do the bronchopulmonary segments form
24
about how many divisions have formed at the time of the bronchopulmonary segments
17 orders of branching
how many orders of branching airways happen after birth
7
what are the stages of maturation of the lungs
- pseudoglandular (5-17 wks)
- canalicular (16-25 wks)
- terminal sac (24 -birth)
- alveolar (32 weeks-8 years)
what are the characteristics of pseudglandular stage
- looks like exocrine glands
- all major elements have formed except those associated with gas exchange
- fetus cannot survive
when is the stage at which survival from then on is possible
canalicular (16-25 wks)
what are the characteristics of the canalicular stage
- overlap with pseudoglandular
- vascularization
- respiratory bronchioles
- primitive alveoli present
- survival possible
- membrane is thicker than mature
what is a major cause of survival rate to increase in fetuses
increased with number of alveoli
what are the characteristics of the terminal sac
- numerous alveoli
- thin epithelium w/ increased vascularization
- type 1 and 2 pneumocytes and lymphatic capillaries
- gas exchange can occur
- survivable
what are the characteristics of the alveolar stage
- alveolocapillary membrane
- primitive alveoli
- form more primitive alveoli
- mature alveoli
- membrane is final thickness
how many of the mature alveoli develop postnatally
95%
when is alveolar development largely completed
3 yrs
until about what age are new alveoli added
8 yrs
during development of the brconchi what does the splanchnic mesoderm do
cartilaginous plates
bronchial SM and CT
pulmonary CT and capillaries
where does the visceral pleura come from
splanchnic mesenchyme
what is the parietal pleura derived from
somatic mesoderm
what is the space between the parietal and visceral pleura called
pleural cavity
what forms the trachea and larnyx
proximal end of the laryngotracheal diverticulum
what are the two components of the trachea and what are their origins
splanchnic mesoderm -cartilage -CT -SM endoderm -glands -epithelium
what is esophageal atresia
when the esophagus just ends and doesn’t connect to the stomach
what is tracheoesophageal fistula
abnormal connection between the esophagus and the trachea
what is a symptom of tracheoesophageal fistula
air in the GI on Xray
what is one cause of tracheoesophageal fistula
polyhydramnios or excess amniotic fluid
-not as much is taken up by the body and it accumulates since placenta can’t get rid of it
what are the characteristics of pulmonary agenesis
complete absence of a lung or a lobe and corresponding bronchi
how can you describe fetal breathing movements
muscle memory of the respiratory muscles to allow proper breathing upon birth
how is amniotic fluid cleared from the lungs
mouth and nose from vaginal pressure on chest on delivery; pulmonary capillaries arteries and veins; lymphatics
what does oligohydramnios cause
too little fluid delays lung development and causes pulmonary hypolsasia
risk increases with oligohydromanios before 26 wks
what is a primary cause of respiratory distress syndrome
surfactant deficiency from type 2 pneumocytes
what are the symptoms of RDS
rapid, labored breathing shortly after birth
- tachypnea
- nasal flaring
- retractions of skin in an effort to breath
- grunting
- cyanosis
how is RDS treated
pure 02 to allow body to compensate
what are congenital lung cysts
fluid or air filled
thought to be dilation of the terminal bronchi late in development
during what week does the intraembryonic coelom develop
4
what does the cranial/caudal portion of hte intraembryonic coelom develop into
cranial - future pericardial cavity
caudal - future pleural and peritoneal cavity
what is a congenital diaphragmatic hernia
viscera bulge into pleural cavity, and stunt ipsilateral lung growth, left side typically impacted; can be corrected at birth
after head folding the primitive pericardial cavity is located _________ to the septum transversum
cranially; heart now bulges into pericardial cavity
What is a prenatal complication of tracheoesophageal ridge abnormalities
Polyhydramnios since the fetus can’t swallow
The epithelial lining and glands of larynx are derived from __________
Endoderm
When does the reopening of the larnyx occur to reopen this airway
10 weeks
Laryngeal atresia is also known as
CHAOS or congenital high airway obstruction syndrome
Laryngeal web is what
Partial occlusion of the airway
At what week does the lung have the correct number of tertiary bronchi
10 on R and 8 on L starting at 7th week
A 35 year-old woman delivers an infant at 40 weeks of gestation (based on the last time of menstruation). While in the neonatal care unit, the infant develops cyanosis and very rapid labored breathing and requires admission to the neonatal intensive care unit. Imaging studies of the thoracic cavity show congestion in the lungs but they appear to be of normal size and there is no apparent abnormality in the diaphragm. The woman reports no family history of lung disease and denies alcohol use, smoking, or taking medications during her pregnancy, and review of the mother’s medical records regarding prenatal care and ultrasound imaging is unremarkable.
- A biopsy of the infant’s lung tissue would most likely show:
A) an eosinophilic, hyaline “membrane” on the alveolar surfaces
B) complete absence of type II pneumocytes
C) significantly reduced branching of the
bronchiolar tree compared to other infants of the same age
D) bacterial infection and inflammation of the lung tissue (pneumonitis)
A, the symptoms are describing RDS, which is also known as hyaline membrane disease, the infant is also a recent delivery, labored breathing, cyanosis and no apparent abnormalities
A 35 year-old woman delivers an infant at 40 weeks of gestation (based on the last time of menstruation). While in the neonatal care unit, the infant develops cyanosis and very rapid labored breathing and requires admission to the neonatal intensive care unit. Imaging studies of the thoracic cavity show congestion in the lungs but they appear to be of normal size and there is no apparent abnormality in the diaphragm. The woman reports no family history of lung disease and denies alcohol use, smoking, or taking medications during her pregnancy, and review of the mother’s medical records regarding prenatal care and ultrasound imaging is unremarkable.
- A possible cause of the infant’s condition is:
A) spontaneous mutation in the surfactant protein B gene
B) presence of a tracheoesophageal fistula
C) overproduction of mesoderm during gastrulation
D) congenital diaphragmatic hernia and lung hypoplasia.
A, RDS is caused by issues with surfactant production. It is either deficient or absent in these children
The period of lung development in which no respiratory brochioles or alveoli have yet formed is known as
- Pseudoglandular
- Canalicular
- Terminal sac
- Alveolar period
1
The period of lung development in which surfactant production begins (but is not necessarily sufficient to prevent airway collapse) is known as the:
- pseudoglandular period
- canalicular period
- terminal sac period
- alveolar period
2
The skeletal muscle of the diaphragm is derived primarily from
- Myoblasts from thoracic somites
- Myoblasts from cervical somites
- Vagal neural crest cells
- Cervical neural crest cells
- Thoracic neural crest cells
The smooth muscle in the wall of the respiratory tract is derived from
- Foregut endoderm
- Splanchnic mesoderm
- Somatic mesoderm
- Intermediate mesoderm
- Neural crest
2
Congenital diaphragmatic hernias
- Arise due to a failure of the pleuropericardial folds to completely separate the pleural and pericardial cavities
- Tend to occur more frequently on the right side of affected individuals
- Can cause lung hypoplasia
- Are due to a failure of neural crest cells to migrate and/or differentiate properly
- All of the above
3, happens more on the left side and causes pressure on the developing lung which doesn’t allow it to grow to full size
What stage of lung development have the alveoli not formed and survival is not possible
Pseudoglandular
Premature infants born at this stage have a good prognosis although they will require respiratory support and treatment with exogenous surfactant
Terminal sac
Stage in lung development in which there is the most surfactant production
alveolar
