P2: Outline the structure of the main tissues of the body.
In this assignment I’m going to talk about the structure of the main tissues which are found within the body as well as what their role is in the terms of two named organs of the body. Tissues are a collection of similar cells that group together to carry out a specific function within the body. There are four different types of tissue found in the human body which include; epithelial tissue; connective tissue; muscle tissue and nerve tissue. The first type of tissue found in the human body is epithelial tissue. These types of tissue are found covering the whole surface of the body, lining of cavities, hollow organs and tubes. The cells a very closely packed and are arranged in one or more layers, they are composed of several layers called Compound Epithelial or a single layer called Simple. Epithelial cells are packed together with hardly any intercellular spaces with a small amount of intercellular substance known as matrix. The bottom layer of the cells are usually attached to connective tissue called the basement membrane which provides structural support and is used to bind the cells to neighbouring structures. The structure of epithelial tissue is related to the function it carries out which include; protection; secretion and absorption. Simple epithelium consists of a single layer of identical cells, which are divided into three main types. The types are named depending on their shape which alters according to the functions they carry out. The more the tissue gets used, the taller the cells. Simple epithelium is usually found on absorptive or secretory surfaces, where it helps to speed up these processes due to the single layer of cells. Simple Epithelium can be squamous, cuboidal, columnar or ciliated. Squamous cells are a single layer of flat cells which contain a nucleus that forms a lump in the centre. They fit closely together forming a thin and smooth layer of membrane across which allows materials to pass through easily via diffusion and osmosis. Squamous cells are found lining the walls of lung alveoli, the heart and blood vessels, where it is known as endocardium. Cuboidal epithelium is made up of cube shaped cells that fit closely together, which have spherical nuclei in the centre of the cell. They are found lying on the basement membrane for support. Cuboidal epithelium is actively involved in secretion, absorption and excretion. They can be found in glands such as the thyroid gland and sweat ducts as well as forming kidney tubules. Columnar epithelium is a single layer of tall and rectangular cells with slightly oval nuclei which are attached on a basement membrane. Sometimes they can contain microscopic filaments known as cilia, which look like little hairs on top of the epithelium. These cells are then called Ciliated Epithelia. Ciliated epithelium cells often contain goblet cells which secrete mucus. The cilia move in a wave like motion movement, this direction of movement causes the mucus to move in that direction. This means that inhaled particles that stick to the mucus are moved to the throat by the cilia. Cilia provide a large surface area for absorption of nutrients. This usually happens in the small intestines where nutrients are passed through. Stratified epithelia are constructed of several layers of cells in various shapes. Unlike simple epithelium there is no basement membrane, the continual cell division in the lower layers pushes cells nearer and nearer the surface. This is where they are shredded. The main function of stratified epithelia is to protect deeper structures from wear and tear. There are two main types, these are stratified squamous and transitional. Stratified squamous epithelia are composed of different layer of cells. The deepest layers of the tissue are mainly formed from columnar but as they grow towards the surface they become flattened and shred to make way for newer cells deeper down. They are usually...
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