Below drawing shows simple columnar epithelium from the stomach. They are longer than they are wide and have the characteristic of their nucleus being near the base of the cell.
Muscle Fibres
Muscle fibres enable all movements, from movement of bones and limbs, to the pumping blood throughout the body. Like no other tissues in the body, muscle fibres have the ability to contact and possess a great deal of elasticity; when stretched they are able to go back into their original shape. There are three major types of muscle tissue in the body; these are smooth, skeletal, and cardiac muscle fibres.
- Smooth Muscle Fibre
Smooth muscles fibres are predominantly located in walls of organs such as the stomach and intestines. The fibres slowly and involuntarily contract to help move food through the digestive system.
The fibres appear elongated with the nucleus in the middle. Smooth muscle fibres are considered smooth as they do not have striations like skeletal and cardiac fibres.
- Skeletal Muscle Fibres
Skeletal muscle fibres make up muscle tissue that is responsible for the movement of bones. These tissues facilitate the movement of the skeleton. Humans have direct control over them through nervous impulses from the brain. Contractions of the cells can produce very fast, powerful and precise movements.
The fibres are the same thickness throughout their length and are stripy (striated) in appearance. Noticeable is that the nuclei are all out on the periphery of each fibre.
- Cardiac Muscle Fibres
Cardiac muscle fibres are shorter and thinner than skeletal muscle and found solely in the protective wall of the heart. They continuously contract, involuntarily to pump blood around the body from the heart. The large presence of mitochondria in the fibres make the muscle highly resistant to fatigue allowing the heart to constantly function.
The cardiac fibres feature a nucleus in the centre of each fibre. The fibres are tube/ cylinder shapes that branch and attach on to other cardiac fibres. This branching and bonding creates a network of interconnected fibres which form strong muscle tissue that will be able to contract in sync.
Connective tissue
Connective tissues generally serve to connect bone to bone, bone to muscle, and muscle to muscle. However blood cells are also recognised as a connective tissue as they connect the body systems together by circulating oxygen, nutrients, and proteins.
- Bone Cell (Osteocytes)
An osteocyte is a mature bone cell. The cells can sense pressures and cracks in the bone caused by muscular activity. They help direct other types of bone cells to where the bone needs to be dissolved. This on-going remodelling helps the bone as an organ adapt to the body’s mechanical needs.
As pointed out in the picture above, the cells connect to one another through narrow channels in the bone known as canaliculi. The canaliculi are also used for the transport of nutrients and waste. The main body of the cell consists of a nucleus, cell membrane, glycogen, calcified bone, mitochondria and other components that sustain the function of the cell.
- Cartilage Cells (Hyaline)
Cartilage cells in adults are found mainly in the joints where they surround the end of the bone. The cells form tissue that is very smooth and has low friction, allowing the bones in a joint to glide over one another when moving. Cartilage also helps cushion and absorb shocks to the joint.
The cells are blue in colour and connect with each other, arranging in groups of two or more. Where they connect they usually have straight outlines with rest of their circumference being rounded. The cells rely on blood vessels in the surrounding tissue to provide the necessary nutrients and remove waste.
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Red Blood Cells/ Erythrocytes
Red blood cells are specialised to carry oxygen to tissues around the body and partly for recovering waste carbon dioxide. In all mammals, red blood cells do not have a nucleus. The absence of a nucleus allows the cell to have biconcave shape which gives them a large surface area to carry oxygen and other gases. This unique shape also enable to cells to stack on top of one another when flowing through very narrow vessels.
The image on the left shows the blood cell viewed from a side point of view; the biconcave/ increased surface area on both sides is apparent. The picture on the right shows how the red blood cell would look if viewed from directly above.
- White Blood Cells/ Leukocytes
White blood cells protect the body against disease and are a major part of the immune system. Unlike red blood cells, they have a nucleus and are larger in size. When an infection in the body occurs, the cells are carried along in the blood to the area(s) in danger. The cells have several ways in which they can attack, one way is by surrounding and destroying the bacteria another is by producing protective antibodies that overwhelm the offending germ.
There are five different types of white blood cell which can be split into two categories; granulocytes and agranulocytes. The above cell resembles a granulocyte cell which is characterised by the granules and contents of the in the cytoplasm. These granules are absent in the agranulocyte type cell.
Neurons
Nervous tissue makes up the central nervous system and the peripheral nervous system. The central nervous system makes the brain spinal cord, the peripheral makes the nerves outside this area. Nervous tissue consists of neurons; the cells function to communicate between different parts of the body by sending and receiving electrochemical signals. Nerve cells are responsible for the five senses; hearing, seeing, smelling, feeling and tasting.
In the below diagram of a nerve cell , visible are the dendrites (part A.), a cell body (B.), and a long axon that is coated in a layer of fat and protein (C.). The branch-like dendrites carry information towards the cell body whereas the long axon carries information away. The cell body contains the nucleus and other components that maintain the function of the cell.
Sperm Cell
Sperm is a male cell used for reproduction. In human reproduction the sperm is transferred to the female ovum via sexual intercourse where it fuses with, and fertilises the egg.
Sperm cells are the smallest human cells. The head of the sperm (labelled A. in the above drawing) is used to penetrate the ovum. Inside the head is where the nucleus can be found. The nucleus carries hereditary information of the male in the form chromosomes and DNA. Part B. of the above is the mid piece/ energy store of the sperm. This contains mitochondria which helps the sperm to survive on its journey to the female egg. Part C. represents the tail which propels the sperm at speed to reach the egg.
Ovum Cell
The ovum is a female reproductive cell. Its function is to provide half the genetic material required for reproduction. In order to fertilise it needs male sperm.
The perfectly round ovum cell is the largest human cell and is visible to the naked eye; this makes it easy for the sperm to get to it. The cell mainly consists of cytoplasm in which it uses to survive whilst waiting for the sperm. The nucleus is not visible until conception. The membrane of the ovum allows only one male sperm to enter for fertilisation.
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Other materials used