Explanation:
The tricuspid valve (right atrioventricular valve) has three cusps and closes during ventricular systole to prevent regurgitation into the right atrium. The bicuspid (mitral) is on the left side. Aortic and pulmonary valves are semilunar valves at the ventricular outlets.
Explanation:
The pollen tube typically enters the ovule through the micropyle, a small opening in the integuments. This is called porogamy. Occasionally, entry through the chalaza (chalazogamy) or integuments (mesogamy) occurs. The micropyle also allows water entry during seed germination.
Explanation:
Lutein and zeaxanthin are carotenoids concentrated in the macula lutea of the retina, filtering blue light and acting as antioxidants, protecting photoreceptors.
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