Saturday, September 12, 2020

Blood: Blood-cells, Plasma, Function and Conditions

Blood: (a means of transport and defense)

Unlike the heart and blood vessels, which are organs in the circulatory system, blood is a complex tissue. It is one of the connective tissues depending on its derivation, from the mesenchymal cells and its structure, which contains the intracellular matrix known as plasma. Blood supplements the tissues and organs and provides a special means of communication

The study of blood:

The average human adult has more than 5 liters of blood in his body. The liquid connective tissue which is the means of transport of the circulatory system, the blood is a liquid which supplies the necessary substances. The two main functions of blood are the transport of nutrients and oxygen to cells and the transport of CO2, urea and other waste away from cells. It also releases immune cells to fight infections and contains platelets that can connect from a plug to a damaged blood vessel to prevent blood loss

Through the circulatory system, the blood adapts to the needs of the body. When you train, your heart pumps faster and stronger to deliver more oxygen-rich blood to your muscles. During an infection, blood transports multiple immune cells to the infection site, where they accumulate to ward off harmful invaders

All these functions make blood a precious fluid. Every year in the United States, 30 million units of blood components are transferred to the patients who need them. Blood is considered so precious that it is sometimes called red gold

Blood contains cells, proteins and sugars:

If you leave a tube to stand for half an hour, the blood separates into three layers while the denser components sink to the bottom of the tube and the liquid remains on top.

Blood is made up of 55% liquid -plasma- and 45% -cells-, almost all red blood cells, white blood cells and platelets (PLT). Plasma is mostly water, but it also includes many essential substances such as proteins (albumin, clotting factors, antibodies, enzymes and hormones), sugars (glucose) and fat particles. All the cells found in the blood come from the bone marrow. They begin their life as stem cells and mature into three main types of cells: red blood cells, white blood cells and PLT. Plazma and cells carry all the material around our body that every cell needs to function and the hormones that are an important part of coordination

Physical properties of blood:

  • Specific gravity: total blood: 1.055 - 1.065
  • Plasma :1.024 - 1.028
  • Viscosity: 5 - 6 times higher than that of water
  • Mass: 6-8% of body weight
  • Blood volume: 8% of body weight, 86% ml / kg of body weight, 5 - 6 L in adults. Children have a greater volume of blood in proportion to body weight than adults
  • Osmotic pressure: 7 - 8 atmospheres at body temperature

Blood Function

Blood is a vital fluid in our bodies and serves many essential functions. Some of these features include:

• Supply of nutrients from food to body cells

• Disposal, including carbon dioxide

• Defense against disease and detection of foreign material (by WBC)

• Coagulation and prevention of blood loss (platelets and coagulation proteins)

• Messenger works by transporting hormones to various systems, allowing them to interact (for example, insulin is created by the digestive system and circulates in the blood, allowing cells to absorb sugars from the food we eat)

• It helps regulate and maintain body temperature, pH and electrolytes, making it important in homeostasis

• Tissue oxygen supply (carried by red blood cells)

Blood Composition

Blood: Blood-cells, Plasma, Function and Conditions

Blood is made up of cells and cell fragments that float in an aqueous liquid, plasma. Red blood cells are of two types: red blood cells (erythrocytes) and white blood cells (leukocytes). Few, the latter take various forms: neutrophils, lymphocytes, monocytes, eosinophils and basophils. Finally, platelets are not real cells but massive cell fragments

Blood cells

Blood: Blood-cells, Plasma, Function and Conditions

Red blood cells, platelets and white blood cells, like neutrophils, come from the same type of cells, hemocytoblasts, produced by the red bone marrow. Lymphocytes and monocytes, derived from the same cells, complete their differentiation in lymphoid tissues Cells, platelets and white blood cells, such as neutrophils, come from the same type of cells, hemocytoblasts, produced by the red bone marrow. Lymphocytes and monocytes, derived from the same cells, complete their differentiation in lymphoid tissues. The red bone marrow is found in the flat bones (skull, sternum) and in the epiphyses of long bones

Bone marrow stem cells, hemocytoblasts can be transformed into various types of blood cells: 

  • Paletlet
  • Red globule
  • Neutrophils

• Neutrophils are white blood cells that participate in immune defense by ingesting bacteria

• Lymphocytes play multiple roles in the immune system. Only a few are present in the blood

Red blood cells (RBC)

Our body contains an average of 25 billion red blood cells (or erythrocytes), nucleus-free cells capable of elongating and deforming to pass into the narrower blood vessels. Each red blood cell has around 250 million hemoglobin molecules. This substance, composed of a protein (globin) and four pigments (heme), plays a vital role in the exchange of gas in the body which carries oxygen and carbon dioxide gas into the blood. It is the iron ion contained in each heme which, when oxidized, gives oxygenated blood its red color

• Red blood cells are by the most numerous. A cubic millimeter (one microliter or 1 µl) contains about 5 million red blood cells. This number can reach over 8 million as an adaptation to life at high altitudes, the reason why endurance athletes train at altitude. The liver destroys excess red blood cells upon returning to sea level, so training should continue until just before the event, if possible

• Red blood cells are biconcave disks about 8 µm wide, offering them a larger surface area (Fick's Law) and allowing them to bend and pass through smaller capillaries

• They are produced by stem cells in the bone marrow; they are full of hemoglobin; They do not have a nucleus or mitochondria and their function is to transport respiratory gases. A mature blood cell becomes little more than a hemoglobin-containing membrane bag, giving the blood its red color

• The red blood cells remain in circulation for about 120 days before being destroyed in the liver and spleen, with a turnover rate of around 2 million per second!

White blood cells (WBC)

• These are more numerous than the approximately 500 to 1 red blood cells and their number fluctuates, increases during infection and decreases on other occasions. Like red blood cells, they form from stem cells in the bone marrow, but they can also reproduce in the lymph nodes, thymus and spleen. They are larger than red blood cells, almost colorless and do not contain hemoglobin. Red blood cells from granulocytes to monocyte lymphocytes 

• White blood cells have a nucleus and although most live for a few days, others can live for many months or years, giving us permanent immunity against repeated infections (memory cells) 

• White blood cells protect us from infections and invasions of cells or foreign substances. While lymphocytes make antibodies, the other two types of white blood cells can also swallow bacteria, in a process called phagocytosis (an active form of transport!). Granulocytes also produce histamine, which is important in allergies  

Lymphocytes (cell A):

  • Description: Large round nucleus. Clear cytoplasm
  • Production site:  lymph nodes and spleen
  • Mode of action:  Make antibodies or kill infected cells

Granulocytes (cell B):

  • Description: Lobed nucleus. Granular cytoplasm
  • Production site: bone marrow
  • Mode of action: destroy bacteria by ingestion (phagocytosis)

Monocytes (cell C):

  • Description: oval or renal nucleus. Clear cytoplasm
  • Production site: lymph node 
  • Mode of action: ingest foreign particles

Platelets and blood clotting

Blood platelets (or thrombocytes) are fragments of megakaryocytes, giant bone marrow cells. Short-lived (five to ten days), they are used for blood clotting and promote healing

 Platelets are not real cells; they are small fragments of other cells, megakaryocytes, which formed in the bone marrow; Its duration is 7-11 days

 Platelets play an important role in blood clotting, binding to the wound site and releasing clotting factors known as prothrombin

 Clotting factors are part of a cascade reaction that starts with the chemicals released from the injured cells and ends with a sticky fibrin network that stops bleeding causing a clot

 A genetic factor VII disorder is called hemophilia, you suffer (all men, why?) It can bleed widely even from a small cut or scrape

• Unwanted blood clotting inside the blood vessels can block blood flow, a thrombosis. If this happens in the brain, brain cells can die, causing a stroke; in the coronary artery, it can cause heart cell death, coronary thrombosis

Blood plasma

Blood: Blood-cells, Plasma, Function and Conditions

Plasma is a yellowish liquid made up of 90% water. It also contains proteins, vitamins and other solutes. These can be divided into three types:

• Albumins: help regulate water potential while maintaining normal pressure and volume. They are the most common plasma proteins

• Immunoglobins (antibodies): they are very large proteins that affect the infection and, therefore, cause the attack of white or infected cells by white blood cells (WBC). Together with the white blood cells they form the immune system

• Fibrinogen: they are tightly rolled proteins that unwind to form a blood clot

Blood Conditions



 Deep venous thrombosis (DVT)

 Disseminated intravascular coagulation (DIC)

 Hemolytic anemia

 Hemorrhage (bleeding)






 Multiple myeloma

 Myocardial infarction (MI)



 Sickle cell disease


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