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Cutaneous squamous-cell carcinoma is the second-most common cancer of the skin (after basal-cell carcinoma, but more common than melanoma). It usually occurs in areas exposed to the sun. Sunlight exposure and immunosuppression are risk factors for SCC of the skin, with chronic sun exposure being the strongest environmental risk factor. [26]
Bast fibres are soft and flexible, as opposed to leaf fibres from monocotyledonous plants, which are hard and stiff. [2] Since the valuable fibres are located in the phloem, they must often be separated from the woody core, the xylem, and sometimes also from the epidermis.
Dicotyledon plantlet Young castor oil plant showing its prominent two embryonic leaves (), which differ from the adult leaves. The dicotyledons, also known as dicots (or, more rarely, dicotyls), [2] are one of the two groups into which all the flowering plants (angiosperms) were formerly divided.
Skin cancer is the most commonly diagnosed form of cancer in humans. [11] [12] [13] There are three main types of skin cancers: basal-cell skin cancer (BCC), squamous-cell skin cancer (SCC) and melanoma. [1] The first two, along with a number of less common skin cancers, are known as nonmelanoma skin cancer (NMSC).
Diagram of fine scale leaf internal anatomy. The epidermal tissue includes several differentiated cell types: epidermal cells, guard cells, subsidiary cells, and epidermal hairs . The epidermal cells are the most numerous, largest, and least specialized. These are typically more elongated in the leaves of monocots than in those of dicots.
Anatomy of a eudicot leaf The plant cuticle is a layer of lipid polymers impregnated with waxes that is present on the outer surfaces of the primary organs of all vascular land plants. It is also present in the sporophyte generation of hornworts , and in both sporophyte and gametophyte generations of mosses . [ 2 ]
A leaf (pl.: leaves) is a principal appendage of the stem of a vascular plant, [1] usually borne laterally above ground and specialized for photosynthesis.Leaves are collectively called foliage, as in "autumn foliage", [2] [3] while the leaves, stem, flower, and fruit collectively form the shoot system. [4]
The leaf arrangement is opposite and decussate or alternate and spiral, and they are frequently aggregated into rosettes. The leaf shape is simple (rarely pinnate) and usually entire, or crenate to broadly lobed, sometimes dentate or more deeply incised, glabrous (smooth) or tomentose. In cross section the leaf blades are flat or round.