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Human Biology Assignment One Tissues by Victoria Jackson Tissues are defined as a group of associated, similarly structured cells that with their ground substance act together in the performance of a specialised function for the survival of the multicellular organism. The tissues are classified into four main groups which are epithelial, connective, muscle and nervous. (http://encarta.msn.com/encyclopedia accessed 08 October 2004) Epithelial Tissues Epithelial tissues form the covering of all body surfaces with the functions being to provide protective covering, absorption, secretion, diffusion, sensation and contractility. They are tightly packed together with little intercellular matrix and can be squamous (flattened or scale like), cuboidal (cube), or columnar (cylindrical or column like) in shape and may be arranged in single or multiple layers. I have chosen to look more into Ciliated Columnar Epithelium; This is a tall column like cell with a nucleus at the bottom near the basement membrane, with cilia and lots of cytoplasm above the nucleus.
It collects in large numbers and is shaped to be large round or oval cells. Adipose has a similar function to that of fibrous tissue, which throughout the body connects by irregular network of strands to form a cushion layer to support blood vessels, nerves and other organs. Adipose is essential for insulation due to its low thermal capacity which allows the body to retain heat, thus functioning normally. Its other vital function is that of protection of delicate organs such as the eyes and kidneys. Fat cells offer this by forming liquid and being excellent at absorbing pressure as they cannot be flattened. Adipose tissue is needed for the body to turn to in times of need due to it being able to form a food reserve. Excess carbohydrates are made into glycogen and turned into fat and stored within adipose tissue which when energy is required by the body converts back.
(HALE, W.G and MARGHAM, J.P and SAUNDERS, V.A. (1995) Biology Dictionary) I have chosen to look more closely at cardiac muscle; Cardiac muscle is specially striated muscle only found in the heart walls and has branching fibres. Cardiac muscle has striations but the fibres are linked laterally between the muscle fibres. Its contractions propel blood through blood vessels to every part of the body. One centrally located nucleus is found per cell the nucleus is positioned centrally due to the nature of the contractions. Intercalated discs strengthen the fibres which enable contractions to occur and a bridge in between intercalated discs give strength and gap junctions will help to spread contractions. Its contractions are not under voluntary control. There are also many more mitochondria present in cardiac cells. It has to be able to contract without getting tired throughout the living life of the person or animal. Microfibrils are linked in order for electric impulses to be passed from cell to cell to ensure contractions are maintained to be rapid, smooth and rhythmic. The contractile proteins causing the contractions are actin and myocin.
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