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Anatony and Physiology - cells in the human body.

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´╗┐Page of The four basic human body structures and their units are cells, tissues, organs and systems. Cells ? these are the smallest independent unit in the human body and can only be seen with a microscope. There are many different types, shapes and sizes. Each type is specialised and carries out a particular function in the body. The types of cells include epithelial cells (the skin), muscle cells, nerve cells, bone cells and blood cells. Every cell has a nucleus, (except red blood cells), a cell membrane and cytoplasm. The nucleus contains the body?s genetic material; this directs all the metabolic activities of the cell. The cell membrane is semi-permeable and surrounds the cytoplasm. Its function is to protect the interior of the cell by allowing certain substances in and keeping others out. The cytoplasm is a gel like substance in which organelles are suspended. These include ribosomes, lysosomes, endoplasmic reticulum, golgi apparatus, mitochondria, and centrioles. The organelles each have different functions within the cell. Tissues ? a group of cells is known as a tissue. Different types of tissues are found in different organs. Humans have four different types of tissue: Epithelial tissue ? this covers the body surface. ...read more.


Respiratory system ? this includes the lungs, nose, trachea, bronchi and bronchioles. The function is gaseous exchange (enable input of oxygen and output of carbon dioxide). There are other systems in the body covering digestion (digestive system), protection (lymphatic system), reproduction (male and female reproduction systems). 1.2 Homeostasis is the maintenance of a stable internal environment in the human body, without this the body would not operate correctly and we would die. There are 6 things that are essential for health need to be controlled: Carbon dioxide ? too much carbon dioxide and the body becomes too acidic. This is mainly lost through the air that is breathed but a little is lost in the urine that is past. The amount of carbon dioxide is controlled by the hypothalamus in the brain and the lungs help to get rid of excess. Urea ? is the waste chemical produced when amino acids are digested in the liver. This is removed via urine and some lost by sweat. Ions ? including sodium, potassium and phosphate need to be kept at the right balance or the integrity of the cells could be compromised. These are controlled by the amount of water we drink and through the urine we pass. ...read more.


The nucleus is the brain of the cell and control all active in the cell much like the human brain controlling the body. The cell membrane holds in the contents of the cell and allows certain elements in and out of the cell, much like the skin on a human which lets substances in and out e.g. sweat. Like the human body having various organs inside the body, the cell is the same having organelles with different functions. The ribosomes are the workhorse of the cell; they carry out protein synthesis for the nucleus. The proteins produced are essential to the function of the cell. The lysosomes are digestive sacs which breakdown macromolecules in the cell; it could be thought of as like the digestive system in the human body. The aerobic respiration of the cell takes place in the mitochondria similar to the respiratory system. The endoplasmic reticulum (ER) acts in a similar function to the blood vessels in the body; they transport substances from one part of the cell to another. The ER is also the site of membrane and protein synthesis. So from a single cell (zygote) the millions of cell divisions produce millions of cells each with the same genetic makeup. The cells coming together to form tissues then into organs but knitted all together into a human body. ...read more.

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