Animal organs are composed of various types of tissues. In their turn, tissues are composed of cells. This paper explores different types of animal tissues and discusses a variety of cell types that make up these tissues.
The four basic types of tissues in animals are: epithelium, nervous, connective, and muscle tissues (Starr, Evers, & Starr 389). Each of them performs its unique function in the animal body and includes cells of different structure.
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"Animal Cells and Tissues".
Epithelium covers animal body surfaces. Also, it lines internal cavities. Other specific characteristics of epithelium are: it lies on a basement membrane (performs the role of cell secretion and holds all cells together), the cells are closely junked together owing to adhesive intercellular substance; it has a secretary or protective function. Epithelium that covers the outer surface of the animal body is epidermis. As for the epithelium that forms the inner lining of tubes and cavities inside the animal body, it is known as endothelium. Epithelium can be one cell thick (known as simple epithelium) or more than just one cell thick (compound epithelium) (Toole & Toole 22). Simple epithelium can be of five basic types given the shape and other characteristics of its constituent cells: squamous epithelium (is made of cells flattened “like paving stones”; e.g. alveoli in lungs or blood capillaries), cuboidal epithelium (made of cells that appear square in shape; cells fit together as if they were a honeycomb; this tissue lines ducts and glands); columnar epithelium (made of elongated cells that appear column-shaped; this type of epithelium lines the small intestine); ciliated epithelium (made of cells of cuboidal shape and has cilia on the cells’ free surface; lines tubes and cavities, e.g. bronchial tubes or the trachea); glandular epithelium (is made of secretory cells; mainly consists of cells secreting mucus) (Roberts, Reiss, & Monger 63). As for the epithelial tissue consisting of many kinds of cells, it is known as stratified epithelium. This ticker type of epithelium is more protective, so it makes up the epidermis of the skin and certain cavities’ lining. The multi-layered structure of the stratified epithelium is the result of the cell division.
The nervous tissue detects various stimuli and relays information. This type of tissue is made of the two cell types. These are neurons and glial cells. The functional units of the nervous tissue and of the nervous system are neurons. They are signaling cells that transmit all nerve messages. Every neuron is composed of a cell body and cytoplasmic extensions axons (long fibers carrying signals from the cell body in a neuron) and dendrites (short fibers carrying signals toward the cell body). As for neuroglial cells, also known as neuroglia, their role is to keep all neurons positioned where they are and supply them with nutrients (Starr, Taggart, & Starr 531).
The muscle tissue is responsible for moving the animal body and its parts. Its basic types are skeletal muscle tissue, cardiac muscle tissue, and smooth muscle tissue. The skeletal muscle tissue is known to interact with the bones in order to move the parts of the body. It consists of muscle fibers – long, cylindrical cells that are multinucleated and get formed by fusion in the process of the embryonic development. The cardiac muscle tissue is found in the heart wall. It is made of branching cells, with one nucleus each, attached by adhering junctions end to end. The smooth muscle tissue consists of unbranched cells, with one nucleus each, and with tapered ends. It is found in tubular organs such as the bladder, the uterus, and the stomach Starr, Taggart, Evers, & Starr 530).
The connective tissue holds together various body parts as well as provides the structural support. This type of tissue binds organs. It holds tissue together and it fills the spaces between these organs. It comprises a jelly-like matrix of cells. In this matrix, the different types of cells are found (e.g. collagen fibers, blood cells, fibroblasts that store fats, etc ) along with protein fibers. The matrix may be liquid (e.g. in blood), solid (e.g. in bone), and soft (e.g. in loose connective tissue). Connective tissues are classified into fibrous (loose, dense, and elastic) connective tissues and special connective tissues (bone, cartilage, blood, and adipose tissue) (Starr & McMillan 70).
In summary, this paper has discussed the four types of tissues found in the animal body. It has also highlighted the types of cells that make up these tissues.
- Roberts, Michael, Reiss, Michael, & Monger, Grace. Advanced Biology. Nelson Thornes, 2000.
- Starr, Cecie & McMillan, Beverly. Human Biology. Cengage Learning, 2011. Print.
- Starr, Cecie, Taggart, Ralph, Evers, Christine, & Starr, Lisa. Volume 5: Animal Structure and
Function. Cengage Learning, 2012. Print. - Toole, Glenn & Toole, Susan. Essential AS Biology for OCR. Nelson Thornes, 2004. Print.
