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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]
The cell is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function. The term comes from the Latin word cellula meaning 'small room'. Most cells are only visible under a microscope.
A cell structure specialized for cell-to-cell adhesion. developmental biology The branch of biology that studies the processes by which living organisms grow and develop over time. The field may also encompass the study of reproduction, regeneration, metamorphosis, and the growth and differentiation of stem cells in mature tissues. disease
In a multicellular organism, an organ is a collection of tissues joined in a structural unit to serve a common function. [1] In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a function. Tissues of different types combine to form an organ which has a specific ...
Epithelial tissue is composed of closely packed cells, bound to each other by cell adhesion molecules, with little intercellular space. Epithelial cells can be squamous (flat), cuboidal or columnar and rest on a basal lamina , the upper layer of the basement membrane , [ 18 ] the lower layer is the reticular lamina lying next to the connective ...
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 .
Metaplasia occurs when a cell of a certain type is replaced by another cell type, which may be less differentiated. It is a reversible process thought to be caused by stem cell reprogramming. Stem cells are found in epithelia and embryonic mesenchyme of connective tissue. A prominent example of metaplasia involves the changes associated with ...
The chemistry of the cell also depends upon the reactions of small molecules and ions. These can be inorganic (for example, water and metal ions) or organic (for example, the amino acids, which are used to synthesize proteins). [7] The mechanisms used by cells to harness energy from their environment via chemical reactions are known as metabolism.