Respiratory Embryology, Development, and Defects
- after folding, the digestion tube is divided into foregut, midgut, and hindgut
- The respiratory diverticulum begins as an outgrowth of the foregut(this appears day 22)
- has splanchnopleuric covering
- lower respiratory forms from endoderm and splanchnopleuric mesoderm
- There’s a pharyngeal fold that forms out as a diverticulum
- two buds grow out-dichotomous branching-forms the tracheobronchial tree
- each division divides-right result in two major buds on left and three major buds on the right
- by 30 days, you have secondary bronchial buds and by 38 days you have tertiary bronchial buds
Lung Formation: four phases
1) Primitive (pseudo) gland-(6-16weeks)-everything somewhat solid as respiratory tree undergoes branching
2) Canalicular-openings grow out in it-terminal bronchioles divides into 2-3 more respiratory bronchioles
3) Terminal Sac(saccular)-canal ends
4) Alveolar-continued growth and division-there’s an end in an alveolus
- At birth, there’s only about 1/8 normal amount of alveoli
- alveolar period goes to about age 8
- Endodermal lining is derived from endoderm
- The cartilage and all the other stuffs is derived from splanchnopleuric mesoderm
- Type II-produce surfactant-that’s type II pneumocytes
- By 32 weeks, there’s enough surfactant
- there’s such a thing as artificial surfactant used-however, its better if mixed amniotic fluid
- surfactant V-gene mutation
- if artificial is used, the infant might make it to maturity, or a point where they make own stuff
Respiratory Distress Syndrome-Hyaline Membrane disease
- not enough surfactant produced
- the tissue-the alveoli would appear as if it were hyaline cartilage-it would have a glassy appearance, like hyaline
- if infant has enough surfactant, there may also be problems with pulmonary vasculature
- most common cause is the lack of surfactant
- to judge whether baby has enough surfactant-you can see if eyelids are open(at about 28-32 wk)-then you can tell whether or not the baby is going to make it
Pulmonary Hypoplasia-this is caused by the failure of the left pleuroperitoneal membrane to completely span the left pericardioperitoneal canal and evagination of abdominal contents into the pleural cavity
- this is more common on RIGHT SIDE
Diaphragmatic Hernias-result from the fact that the left pericardioperitoneal canal is larger and that it normally closes later than the canal on the right
- thoracic or pulmonary hypoplasia also result from oligohydramnios
Tracheoesophageal Fistula-occurs with polyhydramnios, which occurs with esophageal atresia
- this may be caused by an anomaly of the endodermal proliferation in the thoracic foregut
Laryngeal Web-
Broncholaryngeal Malacia-something to do with the degeneration of elastic and CT of broncholaryngeal
Azygos lobe of lung
Tags: alveoli, alveolus, broncholarygeal malacia, gene_mutation, hyaline_cartilage, hyaline_membrane_disease, pharygeal fold, pneumocytes, pulmonary hypoplasia, respiratory_distress_syndrome, respiratory_tree, terminal_bronchioles, tracheobronchial_tree
