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Sclerenchyma is the tissue which makes the plant hard and stiff. Sclerenchyma is the supporting tissue in plants. Two types of sclerenchyma cells exist: fibers cellular and sclereids. Their cell walls consist of cellulose, hemicellulose, and lignin. Sclerenchyma cells are the principal supporting cells in plant tissues that have ceased elongation.
Although sclereids are variable in shape, the cells are generally isodiametric, prosenchymatic, forked, or elaborately branched. They can be grouped into bundles, can form complete tubes located at the periphery, or can occur as single cells or small groups of cells within parenchyma tissues. An isolated sclereid cell is known as an idioblast.
Aerenchyma in stem cross section of a typical wetland plant. Aerenchyma or aeriferous parenchyma [1] or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. [2]
These are sclerenchyma cells which generally fall into two categories: fibres and sclereids. Both cell types have a secondary cell wall and are dead at maturity. The secondary cell wall increases their rigidity and tensile strength, especially because they contain lignin. [citation needed]
The epidermis is the outermost cell layer of the primary plant body. In some older works the cells of the leaf epidermis have been regarded as specialized parenchyma cells, [1] but the established modern preference has long been to classify the epidermis as dermal tissue, [2] whereas parenchyma is classified as ground tissue. [3]
A fresh pig carcass. At this stage the remains are usually intact and free of insects. The corpse progresses through algor mortis (a reduction in body temperature until ambient temperature is reached), rigor mortis (the temporary stiffening of the limbs due to chemical changes in the muscles), and livor mortis (pooling of the blood on the side of the body that is closest to the ground).
Simplified control circuit of human thermoregulation. [8]The core temperature of a human is regulated and stabilized primarily by the hypothalamus, a region of the brain linking the endocrine system to the nervous system, [9] and more specifically by the anterior hypothalamic nucleus and the adjacent preoptic area regions of the hypothalamus.
In cell biology, the meristem is a structure composed of specialized tissue found in plants, consisting of stem cells, known as meristematic cells, which are undifferentiated cells capable of continuous cell division.