fetal circulation

…fill most of the thoracic cavity

lungs

…serves as the lateral borders of the heart

lungs

…forms the floor of the chest

diaphragm

other structures in the thoracic cavity

• heart

• thymus

• trachea

• vessels

• ribs/spine

normal thoracic cavity is what shape?

bell shaped

describe the bell shape of the thoracic cavity

• ribs form lateral margins

• clavicles form upper margins

• diaphragm forms lower margin

…forms the lateral margins of the heart and are superior to the diaphragm

lungs

how does fetus breath in utero

fetus does not breath air in utero. amniotic fluid enters lungs

what is the most important marker for fetal viability?

lung development

describe the size of thorax

typically smaller than the abdominal cavity

large variations in size could be indicative of?

pathology

presence of oligohydramnios; resultant pulmonary hypoplasiacna lead to

a reduction in thoracic size

chest circumference measurements made in…

TRANS, level of the 4 CH view

the apex of the heart is directed towards

left (spleen)

abnormal positioning of the heart may indicate the presence of?

• chest mass

• pleural effusion

• cardiac malformation

normal or abnormal

normal

normal or abnormal

abnormal: CCAM/CPAM

fetal lungs appear?

homogenous and slightly echogenic

how does pregnancy progression affect lung echogenicity?

increases

describe the diaphragm

• muscle that separates the thorax and the abdomen

• hypoechoic curvilinear structure between the liver and lung

• coronal abdominal view best for visualizing

what is this?

diaphragmatic hernia

describe FB on US

• seesaw movement of fetal chest or abdomen sustained for at least 20 seconds

• absent if no activity during a 20 minute observation period

how can FB be documented?

color doppler and obtain a profile view

fetal circulation…the fetal lungs

bypasses

blood flow in the fetus differs in three ways…

• ductus venosus

• foramen ovale

• ductus arteriosus

ductus venosus

• connects the umbilical vein to the IVC

• blood bypasses the liver

• after birth forms the ligamentum venosum

connection between the RA and LA

forament ovale

describe foramen ovale

• connection between the RA and LA

• allows for oxygenated blood to pass from RA supplied by the IVC to the LA

• blood bypasses the lungs

what happens to the foramen ovale after birth?

usually closes after birth

describe the walls in the foramen ovale

flap in the 2 walls separating the RA and the LA

wall 1: septum primum

wall 2: septum scundum

connection between the pulmonary artery and the aorta

ductus arteriosus

ductus arteriosus allows for…

blood to be directed out of the RV and PA and into the aorta, blood bypasses the lungs

what happens to the ductus arteriosus after birth?

forms the ligamentum arteriosus