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38 Cards in this Set

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What comprises the lower respiratory system?
from the pharynx down
When does the lower respiratory system develop?
Week 4
What does the lower respiratory system begin as?
median laryngotracheal groove of the primitive pharynx
The endoderm lining the median laryngotracheal groove gives rise to what?
the epithelium and glands of:
1. the larynx
2. trachea
3. bronchi
4. and the pulmonary epithelium
What arises from the splanchnic mesenchyme and where is it?
1.connective tissue
2. cartilage
3. smooth muscle of structures in the area
1. found surrounding the foregut
The laryngotracheal groove deepens into a diverticulum ventrally which enlarges distally to form what?
a lung bud (2 total)
What separates the forming diverticulum from the primitive pharynx?
longitudinal tracheoesophageal folds
What do the longitudinal tracheoesophageal folds fuse to form and what does this structure do?
1.tracheoesophageal septum
2. divides the forgut into:
-ventral laryngotracheal tube
-dorsal esophagus
What is a fistula between the esophagus and the trachae and what disorder is associated with this?
1. abnormal connection/communication between the esophagus and trachea
2. superior esophageal atresia
What is polyhydramnios?What is it associated with? Why?
1.excess of amniotic fluid
2. esophageal atresia and tracheoesophageal fistula
3. these problems do not allow amniotic fluid to pass to the stomach and intestines for absorption and transfer to the placenta for disposal
The lung bud develops into 2 what?
2 endodermal buds
What space do the endodermal buds grow in? What does this space become?
1. pericardioperitoneal cavities
2. pleural cavities
What happens early in week 5 in regards to respiratory development?
each bronchial bud enlarges into the primordium of a primary bronchus
What do the bronchial buds enlarge into?
primordium of a primary bronchus
Which primary bronchus is larger and orientated more vertically?
right
What happens by week 7 in regards to respiratory development?
The primary bronchi divide into secondary bronchi and then into tertiary bronchi
What happens by week 24 in regards to respiratory development?
the tertiary bronchi divide another 14 more times and the respiratory bronchioles have developed. They will divide another 7 times before birth.
As the bronchi develop, what does the surrounding mesenchyme do?
It synthesizes the surrounding cartilages, smooth muscle, connective tissue, and capillaries.
The lungs acquire a layer of visceral pleura from what?
splanchnic mesenchyme
The thoracic body wall becomes lined by a layer of parietal pleura derived from?
somatic mesoderm
What are the three periods of development of the lungs and what are their weeks?
1. pseudoglandular period (5-17 weeks)
2. canalicular period (16-25 weeks)
3. terminal sac period (24 weeks to birth)
4. alveolar period (later fetal period to 8 years)
What weeks is the pseudoglandular period?
5-17 weeks
What happens during the pseudoglandular period?
1. by week 17 all major elements of the lungs have developed, except for those involved in gas exchange.
2. the lungs look like an endocrine organ
What period of development of the lungs is respiration not possible?
pseudoglandular period
What weeks is canalicular period?
16-25 weeks
What happens during the canalicular period?
1. lumen of bronchi and terminal bronchioles become larger and lungs become vascularized
2. by week 24, respiratory bronchioles have developed and respiration is possible(chances of survival are slim)
What happens in respiratory development by week 24?
respiratory bronchioles have developed and respiration becomes possible.
What weeks is the terminal sac period?
24 weeks to birth
What happens during the terminal sac period?
1. more terminal sacs develop and capillaries enter into close relationship with them.
What types of cells are the terminal sacs lined with and what does each cell do?
1. Type 1 alveolar cells (pneumocytes)
2. Type 2 pneumocytes- secrete surfactant
What is the purpose of surfactant?
1. counteracts the surface tension forces
2. facilitates expansion of terminal sacs
When does surfactant reach adequate levels?
2 weeks before birth
What 2 things are critical to the survival of premature infants in relation to breathing?
1. adequate pulmonary vasculature
2. sufficient surfactant
What weeks is the alveolar period?
late fetal period to 8 years
What percentage of mature alveoli develop after birth?
95%
How do lungs of an adult look in comparison to those of a newborn on xray?
adult lungs look denser
What is the state of developing lungs at birth in relation to amniotic fluid?
lungs are half-filled with amniotic fluid at birth
How do the lungs at birth clear the amniotic fluid in them?
1. through mouth and nose by pressure on the thorax during delivery
2. into the pulmonary capillaries
3. into the lymphatics and pulmonary arteries and veins