ostium

Opening in wall of heart through which blood is drawn from the pericardial sinus [Holdich and Jones, 1983].

Valve of heart [Moore and McCormick, 1969].

Valved opening in heart for retum of blood. (Pl. ostia) [McLaughlin, 1980].

(Order Cladocera):

One of two lateral openings in heart. Blood enters heart through ostia and is pumped anteriorly [Stachowitsch, 1992].

(Order Notostraca):

One of 11 pairs of segmentally arranged openings of heart in thorax; blood enters through ostia [Stachowitsch, 1992].

(Order Diplostraca):

One of typically four pairs of lateral openings in heart (one pair on head region, three in first three trunk somites) [Stachowitsch, 1992].

(Order Anostraca):

One of 14 to 18 pairs of segmentally arranged openings of heart; blood from precardial sinus enters heart through ostia [Stachowitsch, 1992].

(Class Cephalocarida):

One of two openings of heart in each thoracic segment (thoracomere) [Stachowitsch, 1992].

(Order Cumacea):

Pair of muscular openings in posterior region of heart. Blood in pericardial sinus enters heart through ostia [Stachowitsch, 1992].

(Order Tanaidacea):

One of typically two pairs of muscular openings in anterior region of heart. Blood from pericardial sinus enters heart through ostia [Stachowitsch, 1992].

(Order Decapoda):

One of typically three pairs of muscular openings in heart. Blood from pericardial sinus enters heart through ostia. According to position one may distinguish dorsal, lateral, and ventral pairs of ostia [Stachowitsch, 1992].

(Order Amphipoda):

One of basically three pairs of muscular openings in heart at level of second, third, and fourth segments of pereon. Blood in pericardial sinus enters heart through ostia. (Syn. brood plate) [Stachowitsch, 1992].

(Order Isopoda):

One of one or two pairs of muscular openings of heart. Blood from pericardial sinus enters heart through ostia [Stachowitsch, 1992].

(Order Mysida):

Muscular opening in heart, either two pairs at level of third and fourth thoracomeres or three pairs at level of second through fourth thoracomeres. Blood from pericardial sinus enters heart via ostia [Stachowitsch, 1992].

(Order Stomatopoda):

One of 13 pairs of openings of longitudinal heart (six pairs in thorax, seven in abdomen). Each ostium is equipped with a valve and serves to return blood into heart [Stachowitsch, 1992].

(Order Leptostraca):

One of 11 muscular openings in heart (three pairs of lateral ostia followed by three unpaired dorsal and one pair of lateral ostia). Blood in pericardium enters heart through ostia [Stachowitsch, 1992].

(Subclass Branchiura):

Opening at each posterolateral angle of heart. Blood enters heart through ostia and is pumped anteriorly through aorta, ventrally and posteriorly through additional openings [Stachowitsch, 1992].

(Class Ostracoda):

One of three openings (two lateral, one posteroventral) in heart. Blood from pericardium enters heart through ostia and is pumped anteriorly via aorta [Stachowitsch, 1992].

(Class Ostracoda):

One of two posterodorsal openings in heart. Blood from pericardium enters heart through ostia and is pumped through anteroventral aortic valve and aorta as well as posteroventrally through hepatic valves [Stachowitsch, 1992].

(Superorder Syncarida):

Pair of muscular openings in heart of anaspidacean. Located at level of third thoracic somite (thoracomere) [Stachowitsch, 1992].

(Order Thermosbaenacea):

One of two muscular openings of heart. Blood from carapace sinus enters heart via ostia [Stachowitsch, 1992].

(Order Euphausiacea):

One of two pairs of muscular openings in heart. Blood from pericardial sinus enters heart through ostia [Stachowitsch, 1992].