The that are muscular tubes, they carry the oxygenated

The cardiovascular system is an essential organ system in the body which supplies nutrients and oxygen to every cell in the human body. It consists of 3 main parts; the heart is the main organ, the blood carries the nutrients and the blood is the connective tissue.  System: a group of organs working together to provide a certain function in the human body. An organ: a group of tissues that work together to perform a specific function A tissue: a group of specialized cells that have similar structure and function. The heart:The main organ of this system is the heart, it pumps blood around the body, so it can be supplied with nutrients. It is a muscle consisting cardiac muscle tissue.

The tissue of the heart is striated and consist of t-tubules which extends into the muscle cells. It is highly branched, and their cells are connected by overlapping sarcolemma named intercalated discs. The heart is made up of 4 chambers called the left atrium, right atrium, left ventricle and right ventricle. The atriums are the weakest muscles as they push the blood into the ventricles to be pumped to the rest of the body or the lungs. The heart contains valves which prevents backflow of blood, so it goes one way. The heart is split half way this is called the septum. The right side of the heart is responsible for pumping deoxygenated blood towards the lungs to collect oxygen, the left side of the heart is responsible for pumping blood around the whole body.

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Cardiac output=heart rate x stroke volume  Blood vessels: In the cardiovascular system their blood vessels that are muscular tubes, they carry the oxygenated blood and deoxygenated blood as well as glucose and nutrients around the body. The pulmonary artery carries the deoxygenated blood towards the lungs and once oxygenated the pulmonary vein carries the blood around the rest of the body. The arteries and veins are the largest blood vessels which contain a thick, tough wall of connective tissue also have many layers of smooth muscle. The walls of the blood vessel has a single sheet of endothelial cells and separated from the surroundings by a basal lamina. They have smooth muscle so that when the body becomes too warm they can go closer to the skin and vasodilate to get rid of some heat to the surroundings.

Also vasoconstriction can occur so less blood flows through the blood vessels so less blood flows through. By vasodilating during exercise they can hold more blood which then can be transported to the muscles in larger volumes. Capillaries are very small, they are one cell thick and hold blood at low pressure.

They are very good for gas diffusion as they are so thin so gas can pass into to easily. They are located in the lungs and muscles. blood has 4 main parts; the plasma, red blood cells, white blood cells, blood platelets. It is considered a connective tissue, it carries; oxygen, glucose and nutrients.

Blood mainly consists of a straw-coloured plasma called the matrix. Plasma is mainly water it includes dissolved gasses like oxygen, carbon dioxide and nutrients like glucose and amino acids, salts, enzymes and hormones.Lots of proteins known as plasma proteins, which have roles in blood clotting, defences, transport and defence against invading organisms.Red blood cells have a physical form of disc shaped cells they contain no nuclei. Red blood cells contain an iron compound named haemoglobin which gives blood its dark red colour.

The haem combines with oxygen to form oxyhaemoglobin. The most important function for red blood cells is transporting oxygen around the body. These cells are quite large opaque cells meaning they appear to be solid rather than transparent. They play a major role in the immune system fighting off invading bacteria. They are made in the bone marrow.

They fight diseases in 3 different ways;·         Ingest pathogens and destroy them. ·         Make  antibodies to destroy particular pathogens·         Produce antitoxins that counteract the toxins given off by pathogens.Blood platelets are very tiny disc-shaped cells that do not contain a nuclei.

They play a major role in blood clotting and gather at locations of injury as they help prevent loss of fluids and also prevent any foreign unwanted bodies getting inside the body. They are made in the bone marrow and survive in the circulatory system.Epithelial tissue:The squamous is found in the alveoli and capillaries of lungs where gas exchange happens. Single layer of flat cells touching the basal lamina of the epithelium. They are on a basement membrane that they rest on. muscle:Cardiac muscle is striated, the size of cardiac muscle is around 3 cm long and the diameter is 10 to 100 µm. they contain T-tubules and extensions of the muscle cell membrane that go into the centre of the cardiac muscle cells. the cardiac muscle is highly branched, and their cells are connected by overlapping sarcolemma called intercalated discs.

As cardiac muscles needs to contract a lot as it is always beating so it needs lots of mitochondria as it needs a lot of energy. Every myocardial cell has myofibrils. Cardiac muscle has a single nucleus it has many mitochondria to prevent fatigue as we need the heart to always be pumping blood around the body.

     Pacemaker cells:The pacemaker cells form the atrioventricular node which is placed within the left atrium and the right ventricle. They produce electricity in the body by rapidly changing the electrical charge from positive to negative and the switch back again. When the heart is relaxed the cells are electrically polarized which is when the inside of the cell has a negative charge. The outside of the cell is positive. The depolarization causes electricity in the heart. When it repolarizes then then the process repeats itself. The most prevalent organelle in the pacemaker is the mitochondria as it needs a lot of energy to polarize and depolarize and then repolarize after every heartbeat. This requires a lot of energy so it must not run out of energy.