ostium

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ostium

anatomy

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Last updated

July 1, 2026

Quick Summary

The term "ostium" (plural: ostia) refers to a mouthlike opening in a bodily part. This term is used in various anatomical contexts.1

In crustaceans, ostia are valvular openings in the heart that allow blood to enter from the pericardium. In some species, the heart may have multiple pairs of ostia, while in others, the number is reduced.2

The term "ostomy" is derived from the Latin word for "mouth" and describes a surgical procedure creating an artificial opening, or stoma, in the body. This is often done to allow the discharge of bodily wastes when normal excretory channels are compromised. Common types include colostomy, ileostomy, and urostomy.3

Additionally, "gastric ostium" specifically refers to the opening into a gastric pouch in certain marine invertebrates called scyphozoans.4

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human cardiovascular system
Blood supply to the heart
The ostium, or opening, of the right coronary artery is in the right aortic sinus and that of the left coronary artery is in the left aortic sinus, just above the aortic valve ring. There is also a non-coronary sinus of Valsalva, which lies to the…
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The ostium, or opening, of the right coronary artery is in the right aortic sinus and that of the left coronary artery is in the left aortic sinus, just above the aortic valve ring. There is also a non-coronary sinus of Valsalva, which lies to the…
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sinus
Paranasal air sinuses
…means of drainage openings, or ostia. Consequently, their lining is mucous membrane similar to that found in the nose. The mucus secretion formed is propelled by small, hairlike processes called cilia through the ostia of the sinuses to the nasal cavity. From there it is eventually swallowed or expelled. All…
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…means of drainage openings, or ostia. Consequently, their lining is mucous membrane similar to that found in the nose. The mucus secretion formed is propelled by small, hairlike processes called cilia through the ostia of the sinuses to the nasal cavity. From there it is eventually swallowed or expelled. All…
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insect
Circulatory system
…pair of lateral openings called ostia, to the aorta and is discharged in the front of the head. Accessory pumps carry the hemolymph through the wings and along the antennae and legs before it flows backward again to the abdomen.
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…pair of lateral openings called ostia, to the aorta and is discharged in the front of the head. Accessory pumps carry the hemolymph through the wings and along the antennae and legs before it flows backward again to the abdomen.
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circulatory system
Hearts
…pairs of lateral openings (ostia) that allow blood to flow into the heart from a large surrounding sinus, the pericardium. The heart may be suspended by alary muscles, contraction of which expands the heart and increases blood flow into it. The direction of flow is controlled by valves arranged…
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…pairs of lateral openings (ostia) that allow blood to flow into the heart from a large surrounding sinus, the pericardium. The heart may be suspended by alary muscles, contraction of which expands the heart and increases blood flow into it. The direction of flow is controlled by valves arranged…
Read More