( ( ( ( RESPIRATORY EMBRYOLOGY ) ( ( ( The ( lower ( respiratory system ) ) ) ( -LRB- ( ( from ( ( the pharynx ) down ) ) -RRB- ) ) ) ( develops ( during ( week 4 ) ) ) ) ) ( -LRB- ( ( 26-27 days ) -RRB- ) ) ) ( ( starts ( as ( ( a ( median laryngotracheal ) ) ( groove ( ( ( ( ( -LRB- ( The ( Developing ( Human ( , ( 6th ed. ) ) ) ) ) ) , ) ( p. 260 ) ) , ) fig ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP RESPIRATORY) (NNP EMBRYOLOGY)) (SBAR (S (NP (NP (DT The) (JJR lower) (NN respiratory) (NN system)) (PRN (-LRB- -LRB-) (PP (IN from) (ADVP (NP (DT the) (NN pharynx)) (RB down))) (-RRB- -RRB-))) (VP (VBZ develops) (PP (IN during) (NP (NN week) (CD 4)))))) (PRN (-LRB- -LRB-) (NP (CD 26-27) (NNS days)) (-RRB- -RRB-))) (VP (VBZ starts) (SBAR (IN as) (S (NP (DT a) (JJ median) (NN laryngotracheal)) (VP (VBP groove) (SBAR (S (NP (NP (-LRB- -LRB-) (DT The) (JJ Developing) (JJ Human) (, ,) (JJ 6th) (NN ed.)) (, ,) (NP (NN p.) (CD 260)) (, ,)) (VP (VBP fig)))))))) (. .)))
RESPIRATORY EMBRYOLOGY The lower respiratory system (from the pharynx down) develops during week 4 (26-27 days) starts as a median laryngotracheal groove (The Developing Human, 6th ed., p. 260, fig.
(ROOT (S (NP (NP (DT The) (NN development)) (PP (IN of) (NP (NP (DT the) (JJ respiratory) (NN system)) (PP (IN in) (NP (DT the) (NN fetus)))))) (VP (VBZ begins) (PP (IN at) (NP (QP (RB about) (CD 4)) (NNS weeks)))) (. .)))
The development of the respiratory system in the fetus begins at about 4 weeks.