Webster's New World Medical Dictionary

thighbone
See 
femur.
third and fourth pharyngeal pouch syndrome
See 
DiGeorge syndrome.
thalidomide baby
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third stage of labor
See 
placental stage of
labor.
third ventricle
One cavity in a system of four
communicating cavities within the brain that are
continuous with the central canal that contains the
spinal cord. The third ventricle is a median (mid-
line) cavity in the brain and is bounded by the thal-
amus and hypothalamus on either side. It
communicates anteriorly (in front) with the lateral
ventricles, and posteriorly (in back) with the aque-
duct of the midbrain, also known as the aqueduct of
Sylvius. All the ventricles are filled with cere-
brospinal fluid, which is formed by choroid
plexuses, structures that are located in the walls and
roofs of the ventricles.
thoracentesis
Removal of fluid from the space
between the lungs and the chest wall (the pleural
cavity) for diagnostic or therapeutic purposes using
a needle inserted between the ribs.
thoracic
Pertaining to the chest. For example, the
thoracic aorta is the part of the aorta that lies within
the chest.
thoracic aneurysm
See 
aneurysm, thoracic.
thoracic aorta
The part of the aorta that lies
within the chest. The thoracic aorta starts after the
arch of the aorta and runs down to the diaphragm,
the great muscle that separates the chest from the
abdomen. The thoracic aorta gives off numerous
branches that supply oxygenated blood to the chest
cage and the organs within the chest. Also known as
aorta thoracica, aorta thoracalis, and pars thora-
calis aortae. See also 
aorta.
thoracic duct
A vascular structure that recircu-
lates lymph from the lymphatic circulation into the
bloodstream. The thoracic duct begins in the
abdomen, tracks alongside the aorta and esopha-
gus, and eventually joins with the left brachio-
cephalic vein.