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report 代写 The Cardiovascular System Description Biology Essay

Explain the structure and function of erythrocytes.

Erythrocytes are red blood cells. They are a biconcave disc shaped often described as “doughnut” shaped. They are approximately 7µm in diameter and 2 µm thick. During Erythropoiesis a reticulocyte is formed from the stem cell in the marrow. These Reticulocytes have a nucleus which upon maturity to a fully formed Erythrocyte, the nucleus is expelled to allow for more haemoglobin and oxygen to be carried during the cell lifespan. Haemoglobin is the clotting function of blood and is the reason for the red colour. The disc shape is to give the cell more surface area to allow diffusion of the oxygen into the cells more quickly. Although the erythrocyte is larger than some capillaries, the cell is able to distort and enter the narrow passages returning to its original shape afterwards. Erythrocyte cells main function is to transport oxygen through body but they also release carbonic anhydrase that allows H2O in the blood to carry CO2 back to the lungs for expulsion. They also play a part in controlling the bodies Ph balance and homeostasis.

Explain the function of haemoglobin.

When the compound Haem and Globin synthesise it forms haemoglobin. Haemoglobin allows Oxygen and Carbon dioxide to be transported by the Erythrocytes. Oxyhaemoglobin is haemoglobin saturated with oxygen molecules that have attached to the Haem molecule attracted by the Iron (Fe) in the compound, allowing the oxygen to be carried around the blood to be diffused where required.

De-saturated haemoglobin (DeoxyHaemoglobin) occurs when the oxygen molecules have left the protein and this is what gives the Haemoglobin its bluish tint. CO2 also bonds with the Haemoglobin molecule allowing the blood returning to the lungs to transport this for expulsion through exhaling.


Explain the function of leucocytes in relation to the body’s defences and immune responses.

Produce a two-sided leaflet explaining the above to a group of young mothers – clearly explain what leucocytes are and the importance they play. Describe clearly and concisely and use visual images where applicable


Explain platelet function.

You are working for the Red Cross and explaining to “new recruits” what platelets are and their function. Briefly explain how platelets ensure clotting takes place.

Platelets are small fragments megakaryocyte Cells. These cells are found in the bone marrow. These small platelets are essential in the function of Haemostasis which is the function of stopping blood loss, (Blood clotting). They secrete vasoconstrictors that close the openings of blood vessels during vascular spasm, form platelet plugs to stem the flow of blood, secrete clotting factors (proteins), to assist in the clotting of blood. These functions are the important factors of haemostasis which platelets are vital for during bleeding and the catalysts for vascular spasms, platelet plug creation and blood clotting (coagulation).