- two primary components of the lung

Endoderm (primitive gut)

 Visceral Lateral Plate Mesoderm

- end of the foregut

- at pharyngeal arch 4

Epiglottis

- most important genetic factor in relation to the primitive gut formation endometrium

Shh

- primary genetic factor on the lung bud (Lateral Plate Mesoderm)

RA/tbx

- betwen the 4th and 6th branchial arches this structures begins to widen and expand the arytenoid swellings formed from rapid mesodermal proliferation

- formed into a T as the arytenoid swellings grow

Laryngeal groove

Between the 5th and 10th weeks what happens to the laryngeal groove?

It opens, expands, is occluded, and recanalizes

- the (slit-like) structure that remains as an outpocket of the laryngeal groove on the external surface

- becomes the lung bud

Respiratory diverticulum

- innervation of the larynx via the 4th and 6th branchial arches

CN X (Superior Laryngeal and Recurrent Laryngeal)

- tracheoesophageal fistulas usually affect this structure more than its counterpart

- most common creates a superior pouch and inferior tracheoesophageal fistula

esophagus

- most common tracheoesophageal fistula allows this amount of food to get to the stomach and causes severe gas in the stomach

zero

- this gives rise to the epithelium and glands of the lung

endoderm

- this gives rise to the musculature, connective tissue, cartilage, and blood vessels of the lung

splanchnic/visceral mesoder,

- responsible for the dichotomous branching that occurs with the lungs

- produced by mesoderm

FGF

- time period in which we get the 2nd lung branching

(3 L, 2 R)

5th week

- these two layers of mesoderm create the pleura surrounding the pleura cavity that is formed as the lung buds expand into the pericardioperitoneal canals until they fuse to form the diaphragm

Outer visceral mesoderm (visceral pleura [on lung])

&

Somatic or parietal mesoderm (parietal pleura)

- conducting airways are formed during this stage the lasts from the 5th - 17th week

Pseudoglandular period

- respiratory bronchioles and type II pneumocytes are differentiated during this stage

- at the end of this stage 17 orders of branching have occurred (7 more to follow later)

- 15th-26th weeks

Canalicular period

- blood vessels become associated with respiratory bronchioles and induce flattening of type II pneumocytes to type I in this stage

- cranial-->caudal development of lungs

- 24th week till birth

Terminal Sac period

- additional 7 orders of branching occur with an increase in respiratory bronchioles, primitive alveoli and subsequent alveolar maturation

- late fetal - 7-10 y/o

Alveolar period

- induces contractions of labor through prostaglandins

Surfactant

- three requirements for lung maturation and viability

degree of vascularization

thinning of alveolar epithelium

adequate production of surfactant

20 weeks

- occurs with inadequate surfactant production

- alveoli collapse during expiration and must be reinflated with great effort

- respiratory failure ensues

Respiratory Distress Syndrome (RDS)

- babies who take their first breath will have cleared their lungs of fluid and their lungs will float in water

- this means they died...

Perinatal (rather than prenatal)