What are the four main types of tissues in the human body and what are their key characteristics?

Answer 1

1. Epithelial tissues undergo rapid mitosis, have specialized sensory receptors, do not have blood supply (avascular), form a protective barrier between regions, and have many nerves running through them (innervated). They have three surfaces. Their basal (lower-most surface) is the basement membrane. The apical (upper-most surface can have one of many features including lumen, microvilli, and cilia. Their lateral (side surfaces) are specialized to do specific jobs based on the type of epithelial cell. These specializations are adhering junctions (keep the cell in place), tight junctions (keep the cells pulled together and tightly packed), desmosomes (a type of junction that connects two cells together), and gap junctions (allows cells to exchange material with one another). There are three shapes of epithelial cells: squamous (a flat plate-like cell), cuboidal (cells that are wider than they are tall), and columnar (cells that are taller than they are wide). There are also layer types simple (single layer), stratified (two or more layers), and pseudostratified (a single layer that appears to be stratified)
2. Connective tissue consist of cells and their extracellular matrix, or the substance the cells are suspended in. The function of the connective tissue determines what makes up the extracellular matrix. The extracellular matrix is made up of a ground substance and one of three fibers: collagen, reticulin, or elastin. Connective tissue is classified into three main categories: proper connective tissue (further divided into dense and loose connective tissue), embryonic (further divided into mesenchyme and mucous), and specialized connective tissues (cartilage, adipose, bone, and blood).
3. Muscle tissues can be stretched, extended, and contracted. There are three types of muscle tissue: skeletal muscle, cardiac muscles, and smooth muscles.
4. Nervous tissues are located throughout the nervous system and consist of neurons and gilia. Neurons are specialized cells that transmit electrical signals between the brain and the rest of the body. Gilia are cells specialized cells too. There are several types of gilia cells, each with their own function. Astrocytes support neurons with nutrition and other support duties such as cleaning up debris. Oligodendrocytes make myelin in the central nervous system which lines the neurons allowing them to transmit impulses faster and more efficiently. Schwann cells do the same thing as the oligodendrocytes, only in the peripheral nervous system. Microglia patrol the nervous system and destroy foreign invaders.