The structure and functions of body tissues.

Stratified columnar epithelium

Again these particular types of cells are quite rare in the body however they do provide protection along the epiglottis, urethra and the anus. They are usually made up of two layers or multiple layers as this will add more protection when the chemical reactions are taking place.

Ciliated columnar epithelium

This type of tissue is made up of a single layer of cells which are attached to the basement membrane with tiny hairs protruding from the membrane. These tiny hairs are known as cilia. The function of the cilia is to assist with the movement in the passages. This helps to remove mucus, foreign matter and debris as it pushes it along the tract and helps to keep the passage way clear. In the fallopian tubes it helps to push the egg along into the uterus. This type of epithelium can be found in the respiratory tract, trachea, large bronchi and the fallopian tubes.

Compound transitional epithelium

Compound transitional epithelium tissue consists of several layers of cells which can slide over each other. Within these cells the capillaries are situated in the epithelium, as there is no basement membrane and the large superficial cells often have 2 nuclei. In a relaxed state they can be 4-5 cells thick but when they become stretched they appear 2-3 cells thick as the cells become flattened. This type of tissue can be found in the bladder. When the bladder becomes full the cells can expand and withstand a large amount of stretching. The thickness of the tissue therefore plays a big part in preventing any urine escaping into the surrounding tissues.

Glandular Epithelium

Columnar epithelium tissue which contains goblet cells is known as glandular epithelium. This glandular epithelium also consists of cilia which helps to move along the mucus that is secreted by the goblet cells. Glandular epithelium may be found in the form of single cells within another type of epithelium or they may be grouped together to form glands such as the salivary glands. This type of tissue is capable of synthesising and secreting certain substances such as enzymes, hormones, milk, mucus, sweat and saliva all of which are needed by the body.

The next type of tissue to look at is Connective Tissue.

The main function of connective tissue is to support, protect and bind other parts of the body to keep them in place. It is usually supplied with blood and nerves. There are 7 different types of connective tissue. The first one to look at is:

Areolar Tissue

The areolar tissue contains minute spaces with loose moist connective tissue. The matrix is semi fluid and jelly like. Its main function is to support vessels, muscles and nerves. The tissue also carries oxygen and nutrients and removes carbon dioxide and waste products. This type of tissue contains elastin fibres and collagen ones which helps the tissue to be more resilient. The areolar tissue can be found in the thymus gland which is connected by the tissue.

Adipose Tissue

Adipose tissue is similar to areolar tissue but the cells here are specialised for storing fat, and it protects organs and acts as a food reserve. It contains collagen type fibres which are a great shock absorber especially on the soles of your feet and around the kidneys. Adipose tissue is also effective in protecting the body's structures by cushioning and insulating, as the tissue found in adipose is much thicker. Adipose tissue needs to be much thicker as its main function is to protect and absorb and this couldn't be done if the tissue was very thin. Adipose tissue is made up of fatty cells, elastin fibres and collagen fibres. The bloated tissues bulge out between the thickened fibres giving the characteristic "orange peel" look.

White fibrous tissue

White fibrous tissue is a very strong connective tissue but is not very elastic. It contains bundles of collagen fibres all of which are running in the same direction. This type of tissue can be found in tendons, ligaments and intervertebral discs and can even help form parts of the outer protection of other organs.

Yellow elastic tissue

Yellow elastic tissue is made up of mainly elastin fibres and contains very few cells. These elastin fibres allow the tissue to expand and spring back forming the shape there were originally in. Yellow elastic looks like of mesh of elastin fibres all inter weaving between each other. This type of tissue can be found in elastic cartilage for example the ear and here it maintains the shape and is very flexible and supportive.

Cartilage

Cartilage is known as a connective tissue as it provides a strong framework which supports the rest of the body. It is more flexible than bone and the matrix contains a dense network of collagen and elastic fibres.

Hyaline cartilage

The matrix of hyaline cartilage contains closely packed collagen fibres which make this type of cartilage very tough however it can still be flexible. Hyaline cartilage is found on the ends of bones, supporting the larynx, trachea and bronchi and also forms the nasal septum. Its main function is to reduce any friction that may occur between the bones by providing a sliding area which does this facilitating bone movement It also joins bones firmly together in such a way that a certain amount of movement is still possible between them.

Fibrocartilage

The fibrocartilage mainly contains collagen fibres. These collagen fibres are very much interwoven making the tissue extremely strong and rigid. This type of cartilage forms the intervertebral discs here it absorbs and resists compression shocks. The cartilage between adjacent vertebra absorbs the shocks that will otherwise damage and jar the bones while we run or walk. It also deepens sockets in articular cavities which deepen the sockets to make dislocation of the bones less possible (eg the ball and socket of the hip)

Elastic Cartilage

Elastic cartilage contains lots of elastic fibres which make it extremely more flexible than fibrocartilage. The elastic cartilage can be found in the larynx, the earlobes and the tip of the nose. Its main function is to provide support for these structures however it can also tolerate distortion without damage and can return to its original shape when and if required to do so.

Bone

Bone is the hardest tissue in the body, and it is hardened by mineral salts such as calcium phosphate and calcium carbonate. The living cells and the blood vessels and nerves are distributed along with the collagen fibres which are distributed throughout the matrix to make it flexible and not brittle. The structure of the bone is specially designed to withstand the compression strains that may occur on it and also to resist tension. The bones protect the body and all organs especially delicate ones such as the skull which protects the brain. This is made possible as bone is extremely hard and resistant, it also makes up the skeleton which needs to be extremely tough and needs to be able to withstand lots of knocks and bumps without breaking easily.

Blood

Blood is part of the connective tissue family as the living cells are distributed within a matrix. Blood contains 45% cells and 55% plasma. The main function of the blood is transportation. The plasma in the blood transports various blood types throughout the body. It transports food and nutrients from the digestive system to various tissues in the body. It also transports waste tissues to excretory organs it transports hormones by the plasma to targeted organs where they bring about a specific function. Blood is found throughout all of your body and is made up of red blood cells white blood cells plasma and platelets. These platelets help the blood to clot when needing to do some for example when you cut yourself these platelets are responsible for you not to bleed to death. The white blood cells are important components in the immune system which protects the body form infection and disease without these white blood cells are immune system would be practically non existent and we would be prone to infections and disease.

Muscle Tissue

Muscle tissue is made up of long thin cells containing filaments of protein which have the ability to contract.

There are 3 types of muscle tissue the first one being:

Skeletal Muscle

Skeletal muscle contains very large muscle cells tissue is attached to the bones. The skeletal muscle fibres are tied together by loose connective tissue, the collagen and elastic fibres surrounding each cell may blend into those of a tendon that conducts the force of contraction usually to a bone and when the tissue contracts it pulls on the attached bone. Skeletal muscle is under voluntary, conscious control and is capable of doing a lot of work. Skeletal muscle doesn't usually contract unless it is stimulated by nerves, and the nervous system will then provide voluntary control over their activities, it does however become fatigued easily. Skeletal muscle covers your skeleton giving your body its shape. Another function skeletal muscle has is that it prevents joints from dislocating by holding them in place.

Smooth muscle

Smooth muscle is located in the walls of blood vessels, around hollow organs such as the urinary bladder and in layers around the respiratory, circulatory, digestive and reproductive tracts. We have no conscience control over it as it works automatically. It is capable of smooth, slow, steady contractions and it does not become fatigued. It is found in the digestive systems muscular walls of the intestine and it will contract to push the food through your body. It also allows the bladder wall to contract in order for the bladder to expel urine.

Cardiac Muscle

This is a specialised muscle and is only found in the heart. This type of muscle never get tired and it works on auto pilot without ever taking a pause. The muscle will contract to squeeze the blood out of the heart and will relax to fill the heart with blood again.This is a constant process that will carry on for as long as you live.

Nervous Tissue

The nervous system is very complex but it only really consists of 2 basic kinds of cells they are Neurones and Neuroglia.

The first ones to look at are:

Neurones

These have the ability to transmit electrical impulses around the body. They also have a variety of different shapes. The first type of neurone to look at is:

Sensory neurone

Sensory neurones carry impulses from the sense organs to the brain. They therefore convey sensory information into the central nervous system. The primary sensory neurones receive their information directly through the sense receptors rather than dendrites. Sensory neurones are known as unipolar neurones because of their structure. The single process or fibres which divide close to the cell body into 2 main branches the axon and the dendrites. Sensory neurones collect information concerning the external or internal environment and then relay this back to the brain.

Motor Neurones

Motor neurones carry impulses from the brain to the muscles and glands. They are sending messages to respond. A motor neurone stimulates or modifies the activity of a peripheral tissue, or organ. The lower motor is located in the ventral horn of the spinal cord or in motor nuclei of the brainstem this sends motor axons out to the peripheral. Motor neurones can sometimes be known as multipolar. These tend to have a large cell body with a long axon carrying an impulse away from the cell body. They also contain several shorter dendritic processes carrying impulses towards the cell body. Motor neurones are arranged relative to the CNS in the opposite direction. .

Relay Neurones

Relay neurones are located entirely within the brain and the spinal cord. These neurones are responsible for the distribution of sensory information and the coordination of motor activity. The more complex the response to a stimuli the greater the number of relay neurones involved.

Neuroglia

Neurogila is a collective name given to a series of highly specialised cells which have a supportive function to neurones. They support cells found only in the brain and the spinal cord. They also provide mechanical and metabolic support for neurones. They therefore have a very protective function. However they do not generate or conduct nerve impulses.