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27 Cards in this Set
- Front
- Back
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what is the lower respiratory system?
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pharynx down
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when does the lower respiratory system develop?
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week 4 (days 26-27)
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as what does the lower respiratory system start?
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median laryngotracheal groove in caudo-ventral wall of primitive pharynx
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what does the endoderm of the median laryngotracheal groove give rise to?
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epithelium and glands of the larynx, trachea, bronchi, and pulmonary epithelium
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what does the splanchnic mesenchyme surrounding the foregut give rise to?
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connective tissue
cartilage smooth muscle |
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what happens to the laryngotracheal groove?
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deepens into a diverticulum ventrally which enlarges into a lung bud distally
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what happens to the diverticulum of the laryngotracheal groove?
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becomes separated from the primitive pharynx by longitudinal tracheoesophageal folds which fuse to form trachoesophageal septum
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what is the function of the trachoesophageal septum?
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divides foregut into ventral laryngotracheal tube and dorsal esophagus
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what fuses to form the trachoesophageal septum?
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longitudinal trachoesophageal folds
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what is a fistula?
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abnormal connection
(e.g. between trachea and esophagus) |
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what is usually associated with a trachoesophageal fistula?
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superior esophageal atresia
coughing and choking on swallowing pneumonia or pneumonitis (reflux of gastric contents into trachea and lungs) |
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what is polyhydramnios?
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excess of amniotic fluid
associated with esophageal atresia and trachoesophageal fistula |
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into what does a lung bud develop?
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2 endodermal bronchial buds which grow into pericardioperitoneal cavities (primordia of pleural cavities)
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when does each bronchial bud develop into the primordium of a primary bronchus?
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early in week 5
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by when have primary bronchi divided into secondary and subsequently tertiary bronchi?
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week 7
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how many times have the bronchi divided by week 24?
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16 times
(respiratory bronchioles have developed) |
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how many times with respiratory bronchioles divide between week 24 and birth?
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7 times
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from where do the lungs acquire the pleura?
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visceral - splanchnic mesenchyme
parietal - somatic mesoderm |
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what are the periods of lung development?
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fetal period
pseudoglandular period (5-17 weeks) canalicular period (16-25 weeks) terminal sac period (24 weeks - birth) alveolar period (late fetal to 8 years) |
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by when have all of the major elements of the lungs formed (except those involved in gas exchange)?
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week 17
lungs look like endocrine organ no respiration possible |
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by when have respiratory bronchioles developed?
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week 24
respiration is possible, but chances of survival are slim |
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what happens in the canalicular period of lung development (16-25 weeks)?
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lumen of bronchi and terminal bronchioles become larger and lungs become vascularized
respiratory bronchioles form |
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what happens during the terminal sac period of lung development (24 weeks to birth)?
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more terminal sacs develop
capillaries enter into close relationship with terminal sacs terminal sacs are lined with type 1 alveolar cells (pneumocytes) |
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when does surfactant reach adequate levels?
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2 weeks prior to birth
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what cells secrete surfactant?
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type II pneumocytes
(surfactant counteracts the surface tension forces and facilitates expansions of terminal sacs) |
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when do 95% of mature alveoli develop?
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after birth
newborn has 1/6 or 1/8 of adult number of alveoli (lungs look denser in x-ray) |
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what happens to the amniotic fluid from the developing lungs at birth?
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cleared:
through mouth and nose by pressure on thorax during delivery into pulmonary capillaries into lymphatics and pulmonary arteries and veins |
