Blood (The Circulating Fluid ) | Chapter Circulation | Video 5

Blood
Blood is a constantly circulating fluid providing the body with nutrition, oxygen, and waste removal.
It brings oxygen and nutrients to all the parts of the body so they can keep working. Blood carries carbon dioxide and other waste materials to the lungs, kidneys, and digestive system to be removed from the body. Blood also fights infections, and carries hormones around the body.
Blood Components
There are four basic components that comprise human blood: plasma, red blood cells, white blood cells and platelets.

Platelets
Platelets are the smallest of our blood cells and literally look like small plates in their non-active form. Platelets control bleeding. Wherever a wound occurs, the blood vessel will send out a signal. Platelets receive that signal and travel to the area and transform into their “active” formation, growing long tentacles to make contact with the vessel and form clusters to plug the wound until it heals. Platelets survive only about 9 days in the bloodstream and are constantly being replaced by new platelets made by the bone marrow.

White Blood Cells
Although white blood cells (leukocytes) only account for about 1% of your blood, they are very important. White blood cells are essential for good health and protection against illness and disease.. They flow through the bloodstream and attack foreign bodies, like viruses and bacteria. They can even leave the bloodstream to extend the fight into tissue. Some types of WBCs make antibodies, which are special proteins that recognize foreign materials and help the body get rid of them. New cells are constantly being formed — some in the bone marrow and some in other parts of the body such as the spleen, thymus, and lymph nodes.
They are highly differentiated for their specialized functions, they do not undergo cell division (mitosis) in the bloodstream, but some retain the capability of mitosis.

Red Blood Cells
The red blood cells (erythrocytes) constitute about 45 percent of the volume of the blood, and the remaining cells (white blood cells, or leukocytes, and platelets, or thrombocytes) less than 1 percent.
Red blood cells shaped like slightly indented, flattened disks. They have a lifecycle of about 120 days in the body.
RBCs contain hemoglobin a protein that carries oxygen. Blood gets its bright red color when hemoglobin picks up oxygen in the lungs. As the blood travels through the body, the hemoglobin releases oxygen to the different body parts.
Within the bone marrow the red cell is derived from a primitive precursor, or erythroblast, a nucleated cell.
The spleen is where red blood cells are destroyed. And also in liver.

Plasma
Plasma is the liquid portion of your blood. The plasma, is a complex solution containing more than 90 percent water. Plasma is yellowish in color and is made up mostly of water, but it also contains proteins like (clotting factors, fibrinogen, antibodies) sugars, lipids, amino acids, hormones, enzymes, vitamins, salts and waste products like urea. It transports water and nutrients to your body’s tissues.
Plasma protein exerts an osmotic effect by which water tends to move from other extracellular fluid to the plasma. The major plasma protein is serum albumin, a relatively small molecule, the principal function of which is to retain water in the bloodstream by its osmotic effect.
Functions of Blood
Respiration
Blood carry oxygen to all parts of the body for respiration.
Nutrition
Each substance required for the nutrition of every cell in the body is transported by the blood: the precursors of carbohydrates, proteins, and fats; minerals and salts; vitamins and other accessory food factors.
Excretion
The blood carries the waste products of cellular metabolism to the excretory organs. Urea, creatinine, and uric acid are nitrogen-containing products of metabolism that are transported by the blood and rapidly eliminated by the kidneys. The liver is in part an excretory organ. Bilirubin (bile pigment) produced by the destruction of hemoglobin is conveyed by the plasma to the liver and is excreted through the biliary ducts into the gastrointestinal tract. Other substances, including certain drugs, also are removed from the plasma by the liver.
Immunity
The white blood cells (leukocytes) have a primary role in the immunity.
Temperature regulation
Heat is produced in large amounts by physiological oxidative reactions, and the blood is essential for its distributing and disposing of this heat.
Hemostasis
The process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel. The platelets contribute to the resistance of capillaries,

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