Fact: There are around 5 litres of blood in the average human adult body, though this can vary depending on various factors. During pregnancy for example, a woman may have 30 to 50% more blood than women who are not pregnant. Blood accounts for approximately 7/8% of the total weight of the human body.
We all are well acquainted with the sight of blood: it’s a crimson fluid that flows from your body after a cut or a significant injury. Blood’s composition is incredibly complicated, furthermore, as we further progress with this article, you will realize the reason blood is essential to our survival. Blood is actually the delivery medium for dissolved gases, nutrients, hormones, and more.
Blood plasma is a yellow fluid component of blood that suspends the entire blood cells. The liquid element of blood transports cells and proteins throughout the body. Blood plasma accounts for approximately half of the body’s total blood volume and the intravascular quantity of extracellular fluid, primarily water.
The body’s circulatory system comprises blood, the heart, and blood vessels (such as veins and arteries). The circulatory system contributes to the body’s overall equilibrium (i.e. homeostasis). The blood picks up oxygen as it travels through the lungs and it flows via relatively narrow blood vessels (from arteries to arterioles and capillaries) so that the oxygen-rich blood is able to provide oxygen to the cells.
Oxygen needs have influenced both the blood composition and the design of the circulatory system. Transported oxygen is dissolved in the plasma protein in particular elemental creatures, such as tiny worms and molluscs. Pigments capable of carrying relatively significant quantities of oxygen are found in animals with higher oxygen demands.
At the same time, all vertebrates and certain invertebrates possess the red pigment haemoglobin, including iron. Haemoglobin is found only in the red cells of practically all vertebrates, including humans (erythrocytes).
Lower vertebrates’ red cells (such as birds’) have a nucleus, while mammalian red cells do not. The size of red cells varies greatly amongst species; goat red cells being significantly smaller than human red cells for example. All blood types are a mixture of erythrocytes, leukocytes, and platelets suspended in blood plasma.
Composition of Blood
From an evolutionary point of view, blood was thought to have evolved from a type of cell responsible for phagocytosis and feeding. Blood and the circulatory system have aided the evolution of increasingly sophisticated lifeforms over billions of years. Centrifugal force can separate blood components from the blood plasma of blood constituents (erythrocytes, leukocytes, and platelets).
The Critical components of blood
- Erythrocytes/ Plasma: Plasma combines water, sugar, fat, protein, and salt that make up blood’s liquid component. Plasma’s primary function is to carry blood cells and nutrients, waste products, antibodies, clotting proteins, chemical messengers such as hormones, and blood proteins also known as plasma proteins assist in regulating the body’s fluid balance.
- Hematocrit/ Red blood cells: The hematocrit is the volume of erythrocytes in a blood sample. Hematocrit values vary by gender; men’s values range from 44 to 45 per cent of blood volume, while women’s values range from 39 to 44 per cent of blood volume. Blood appears red because of the considerable quantity of red blood cells, which acquire their colour from haemoglobin.
The absence of a nucleus makes a red blood cell more pliable but also shortens the cell’s life. Red blood cells include a protein called haemoglobin, which helps deliver oxygen from the lungs to the rest of the body and later returns carbon dioxide from the body to the lungs. The hematocrit is a standard measure of red blood cell levels defined as the proportion of entire blood volume composed of red blood cells.
- Leukocytes/White blood cells (WBCs): White blood cells, often known as leukocytes, account for less than 1% of total blood volume and play an important role in illness and fighting infection. The number of white blood cells in one ml of blood is typically between 3,700 and 10,500.
White blood cell counts higher or lower than average might suggest illness. The white non-transparent layer of leukocytes and thrombocytes is above the erythrocyte layer. A buffy coat is a name for this layer (forms about 1 per cent of blood volume).
- Platelets/ thrombocytes: Platelets, also known as thrombocytes, work with clotting proteins to prevent or minimize bleeding. Platelets should range between 150,000 and 400,000 per microliter of blood. Red blood cells, white blood cells, and platelets are produced in the bone marrow and then enter circulation.
Plasma cells are mainly water, which the intestines absorb from ingested food and drink. The heart circulates them as blood throughout the body via the blood arteries.
Functions of Blood
The role of the blood, in broad terms, is to keep the internal environment stable. The ability to adjust to changing life conditions—the endurance of broad fluctuations in climate and air pressure; the ability to change the amount of physical activity—is made possible by the blood circulating within the veins; tolerance to dietary and fluid changes; resistance to physical harm, chemical toxins, and infectious pathogens.
The structure of blood is highly complicated, and numerous components contribute to its operational functions. Sensors that detect changes in temperature, pH, oxygen tension, and blood component concentrations are among the regulatory systems the blood is engaged in. In some instances, the effects of these stimuli are mediated by the neurological system or by the hormone release (chemical mediators).
The paragraphs that follow highlight some of the critical functions of the blood.
Blood’s primary functions include:
- 1. Fluid Connective Tissue: Blood is a fluid plasma connective tissue of 55% plasma and 45% formed components such as WBCs, RBCs, and platelets. Because these live cells are floating in plasma, blood is a fluid connective tissue rather than merely fluid.
- 2. It gives oxygen to the cells: The blood collects oxygen from the lungs and delivers it to various cells throughout the body. Waste carbon dioxide travels from the bloodstream to the lungs and is expelled.
- 3. Transports Nutrients and Hormones: Glucose, vitamins, minerals, and proteins are taken into the bloodstream via the capillaries in the villi lining the intestinal tract. Hormones released by the endocrine glands are also delivered to other organs by the blood and tissues.
- 4. Homeostasis: Blood keeps the internal body temperature stable by absorbing and releasing heat.
- 5. Clotting of the Blood at the Site of Injury: Platelets aid in blood clotting factors at the site of damage. Platelets and fibrin combine to create a clot at the wound site.
- 6. Waste transport to the Kidney and Liver: Blood flows into the kidney, where it is filtered to eliminate nitrogenous waste from the blood plasma. The liver also removes poisons from the blood.
- 7. Body defence against infections: Infections are combated by types of white blood cells during an infection, they tend to multiply fast.
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