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In biology, tissue is an assembly of similar cells and their extracellular matrix from the same embryonic origin that together carry out a specific function. [1] [2] Tissues occupy a biological organizational level between cells and a complete organ. Accordingly, organs are formed by the functional grouping together of multiple tissues. [3]
In the Class 7 textbook topic titled “Our Pasts-2”, pages 48 and 49 have been excluded. These pages mentioned “Mughal Emperors: Major campaigns and events.” The deletions also affected Biology and Chemistry textbooks as the theory of evolution and the periodic table were also purged from class 10 NCERT textbooks. [35] [36]
There are four basic types of animal tissues: muscle tissue, nervous tissue, connective tissue, and epithelial tissue. [5] [9] All animal tissues are considered to be subtypes of these four principal tissue types (for example, blood is classified as connective tissue, since the blood cells are suspended in an extracellular matrix, the plasma). [9]
This tissue is thus the initial site where pathogenic agents, such as bacteria that have breached an epithelial surface, are challenged and destroyed by cells of the immune system. [1] In the past, the designations areolar tissue, adipose tissue, and reticular tissue have been listed as subsets of loose connective tissue. However, they are no ...
Primary mesenchyme is the first embryonic mesenchymal tissue to emerge, and it is produced from EMT in epiblast cells. In the epiblast, it is induced by the primitive streak through Wnt signaling, and produces endoderm and mesoderm from a transitory tissue called mesendoderm during the process of gastrulation. [17]
Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. [ 1 ] [ 2 ] It also contains the stromal vascular fraction ( SVF ) of cells including preadipocytes , fibroblasts , vascular endothelial cells and a variety of immune cells such as adipose tissue macrophages .
This type of connective tissue is found mostly in the reticular layer (or deep layer) of the dermis. [3] It is also in the sclera and in the deeper skin layers. Due to high portions of collagenous fibers, dense irregular connective tissue provides strength, making the skin resistant to tearing by stretching forces from different directions.
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts of the plants such as stems and leaves, but it also transports nutrients .