EVERYDAY SCIENCE

Detailed explanation-1: -lumen are cavities present inside the cell, cells of sclerenchyma tissue have narrow lumen because sclerenchyma are strongly lignified which lead to compressing the cell and thus only narrow cavity is left.

Detailed explanation-2: -A lumen (plural: lumina) is a term that describes the cavity within the tubular structure. It usually refers to the space inside digestive, respiratory, and urogenital organs or vessels of the body. For example, the blood flows towards the heart through the lumen of the superior vena cava.

Detailed explanation-3: -Sclereids are specialized cells formed in a variety of shapes. They have lignified secondary cell walls and are non-living at maturity. Their primary function is for mechanical support and protection.

Detailed explanation-4: -No, parenchyma cells do not have a lumen. It is present in sclerenchyma.