Topic 12. Blood components. Plasma. Physiological functions of plasma proteins.
Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). Anatomically, blood is considered a connective tissue, due to its origin in the bones and its function. Blood is the means and transport system of the body used in carrying elements (e.g. nutrition, waste, heat) from one location in the body to another, by way of blood vessels.
Blood is made of two parts:
Plasma which makes up 55% of blood volume. Formed cellular elements, which combine to make the remaining 45% of blood volume.
- Rbc's (Erythrocytes)
- WBC's(Leukocytes)
- Platelets (Thrombocytes)
Plasma is made up of 90% water, 7-8% soluble proteins (albumin maintains bloods osmotic integrity, others clot, etc), 1% carbon-dioxide, and 1% elements in transit. One percent of the plasma is salt, which helps with the pH of the blood. The largest group of solutes in plasma contains three important proteins to be discussed. There are: albumins,globulins, and clotting proteins.
Albumins are the most common group of proteins in plasma and consist of nearly two-thirds of them (60-80%). They are produced in the liver. The main function of albumins is to maintain the osmotic balance between the blood and tissue fluids and is called colloid osmotic pressure. In addition, albumins assist in transport of different materials, such as vitamins and certain molecules and drugs (e.g. bilirubin, fatty acids, and penicillin).
Globulins are a diverse group of proteins, designated into three groups: gamma, alpha, and beta. Their main function is to transport various substances in the blood. Gamma globulins assist the body's immune system in defense against infections and illness.
Clotting proteins are mainly produced in the liver as well. There are at least 12 substances, known as "clotting factors" that participate in the clotting process. One important clotting protein that is part of this group is fibrinogen, one of the main components in the formation of blood clots. In response to tissue damage, fibrinogen makes fibrin threads, which serve as adhesive in binding platelets, red blood cells, and other molecules together, to stop the blood flow. (This will be discussed in more detail later on in the chapter.)
Plasma also carries Respiratory gases; CO2 in large amounts(about 97%) and O2 in small amounts(about 3%), various nutrients(glucose, fats), wastes of metabolic exchange(urea, ammonia), hormones, and vitamins.