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Heart valve histology
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The heart valves fall into two groups. The atrioventricular valves are the tricuspid and the mitral. And the semilunar valves are the aortic and the pulmonary.
Each flap of the valve, or leaflet, is anchored to the fibrous skeleton of the heart, a framework of tough tissue. Seen under the microscope, the mitral leaflet is not a smooth sheet: it is a stack of layers. The fibrosa, stiff, with thick fibers of collagen, a connective tissue protein. The spongiosa, made mostly of glycosaminoglycans and proteoglycans, two families of molecules that make up the packing material of the tissue. And the atrialis, thinner, with elastic fibers. It is a tarp of several fabrics sewn together: one stiff, one spongy, one elastic.
The atrioventricular valves also carry chordae tendineae, cords that tie them to the papillary muscles, just like the lines of a parachute.
In brief
The heart has two atrioventricular valves, the tricuspid and mitral, and two semilunar valves, the aortic and pulmonary.
Their leaflets are anchored to the heart's fibrous skeleton, its framework of tough tissue.
Under the microscope, the mitral leaflet is arranged in layers: the fibrosa, stiff with thick collagen; the spongiosa, made of glycosaminoglycans and proteoglycans; and the atrialis, thin and elastic.
It is a tarp of several fabrics sewn together: one stiff, one spongy, one elastic.
The atrioventricular valves are also tethered to the papillary muscles by the chordae tendineae.
Sources (2)
- StatPearls PublishingHistology, Heart
- National Center for Biotechnology Information, StatPearls PublishingAnatomy, Thorax, Mitral Valve, StatPearlsPublished
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