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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]
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]
For promotion from Secondary level (Class IX-X) to Senior Secondary level (Class XI-XII), a student must obtain, for all subjects (or best 5 if 6 subjects are taken), 33% overall, without any minimum theory mark requirement. Originally, the passing criteria were set such that a student had to get 33% in both the theory and practical components.
Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial (mesothelial) tissues line the outer surfaces of many internal organs, the corresponding inner surfaces of body cavities, and the inner surfaces of blood vessels.
The ground tissue of plants includes all tissues that are neither dermal nor vascular. It can be divided into three types based on the nature of the cell walls. This tissue system is present between the dermal tissue and forms the main bulk of the plant body. Parenchyma cells have thin primary walls and usually remain alive after they become ...
Simple squamous epithelium falls under the physiological category of exchange epithelium due to its ability to rapidly transport molecules across the tissue layer. To facilitate this movement, some types of simple squamous epithelium may have pores between cells to allow molecules to move through it, creating a leaky epithelium.
Dense connective tissue also known as fibrous tissue [8] is subdivided into dense regular and dense irregular connective tissue. [9] Dense regular connective tissue, found in structures such as tendons and ligaments , is characterized by collagen fibers arranged in an orderly parallel fashion, giving it tensile strength in one direction.
Soft tissue connects and surrounds or supports internal organs and bones, and includes muscle, tendons, ligaments, fat, fibrous tissue, lymph and blood vessels, fasciae, and synovial membranes. [ 1 ] [ 2 ] Soft tissue is tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth .