Human Anatomy - Lecture Notes - Savchuk O.I. 2017

Blood

Lecture Outline

1. Characteristics of Blood

2. Blood Plasma

3. Formed Elements of Blood

4. Hematopoiesis (Homeostasis)

5. Blood Groups

6. Blood Transfusion

Blood is a liquid body tissue that circulates through a closed system of vessels. Its Extracellular matrix is in a liquid state and is called plasma. It contains formed elements: erythrocytes, leukocytes, and platelets. By volume, plasma accounts for 55-60% of all circulating blood, while formed elements make up 40-45%. In adults, blood constitutes 6-8% of body weight. For instance, a young person weighing 70 kg has 5-6 L of circulating blood. In children, the relative volume of blood is greater than in adults, making up 15% of body weight in newborns and 11% in infants under one year of age. About 75% of all blood circulates in the vessels, while 25% is stored in blood reservoirs (Spleen, Liver, Skin). Blood plasma contains 91% Water and 9% dry residue, which consists of Organic compounds (Proteins, glucose, Amino Acids, uric acid, etc.). Blood plasma also contains mineral salts, mainly Na, K, Cl—about 0.9% of the plasma mass.

Blood

BLOOD AND Lymph are Tissues that form the body's internal environment. They have a liquid consistency.

Blood consists of Cells (formed elements) and extracellular matrix (plasma).

The primary Functions OF BLOOD are transport, protection, and homeostasis.

Blood plasma is a colloidal system containing 90 to 93% water and 7-10% dry matter. Proteins account for about 6.6-8.5% of the dry matter, while other organic and mineral compounds make up 1.5-3.5%.

Plasma contains proteins, Lipids, CARBOHYDRATES, and other organic compounds, as well as metabolic end products—such as urea, uric acid, and others—which enter the blood from tissues and are transported via the bloodstream to the Kidneys and, to some extent, the skin. Plasma Proteins include albumins, globulins, and fibrinogen, whose composition and quantity in the blood remain constant. Most plasma proteins are synthesized by liver cells. Fibrinogen holds a special place among blood proteins because, under certain conditions, it can become insoluble and form a fibrous Structure, converting into fibrin. This process is known as blood clotting. Plasma also contains minerals—sodium, potassium, calcium, magnesium, chlorine, phosphorus, iodine, zinc, etc.—which are mostly bound to proteins or other organic compounds.

Formed Elements of Blood

The formed elements of blood include erythrocytes, platelets, and leukocytes. Of these, only leukocytes are true cells. Erythrocytes and platelets are non-cellular structures of living matter.

Erythrocytes (red Blood Cells) are the most numerous formed elements of blood. In humans, they are post-cellular structures that have lost their Nucleus and almost all Organelles during development.

Erythrocytes are produced in the Cytology/practical/86.html">Red Bone Marrow, and their lifespan is 100-120 days. They are cleared by macrophages in the spleen and, to a lesser extent, The Liver and red bone marrow. Erythrocytes function within the vascular bed. Their functions include:

1) Respiratory function, which is mediated by Hemoglobin.

2) Transport function—erythrocytes adsorb A number of BIOLOGICALLY ACTIVE SUBSTANCES (amino acids, IMMUNOGLOBULINS) On the surface of their Plasmalemma.

Normally, the majority of erythrocytes (80%) are biconcave discs, known as discocytes.

The average diameter of an erythrocyte is 7.1-7.9 µm. As erythrocytes age, their size decreases. Individual erythrocytes may have a diameter of 6 µm or less (microcytes), and conversely, when the diameter exceeds 8 µm, they are called macrocytes. If the proportion of macro- and microcytes exceeds 25%, this phenomenon is known as anisocytosis.

Atypical forms of erythrocytes (poikilocytes), such as spherical ones, can also be found.

Platelets (thrombocytes) are small, non-nucleated, round, oval, or spindle-shaped bodies. They are the smallest formed elements of blood (2-3 µm) that function both inside and outside the vascular bed. Platelets participate in blood clotting, forming a clot when a blood vessel is damaged. They reduce the permeability of the vessel wall and contain substances that constrict Blood Vessels upon injury.

The lifespan of platelets is 5-8 days. Due to their tendency to aggregate, platelets are found in clumps in blood smears.

The Classification of leukocytes is based on several features, the primary one being the presence of specific granules in their Cytoplasm. Based on this feature, all leukocytes are divided into granulocytes and agranulocytes.

Granulocytes (granular leukocytes) are characterized by the presence of specific granules in their cytoplasm, which exhibit different staining properties (basophilic, oxyphilic). Consequently, granulocytes are divided into basophils, eosinophils, and neutrophils.

Agranulocytes (nongranular leukocytes) lack specific granules in their cytoplasm; only certain cells contain nonspecific (azurophilic) granules. Their nucleus is typically round or Kidney-shaped. Agranulocytes include monocytes and lymphocytes.

Monocytes are the largest of all leukocytes and are spherical in shape. They are formed in the red bone marrow, from where they enter the bloodstream, remaining there as immature cells for 36 hours to 3–4 days. In tissues, under the Influence of the microenvironment and stimulating factors, monocytes differentiate into various types of macrophages.

Functions of monocytes:

1) Defense and intracellular Digestion of various dead and senescent cells.

2) Providing nonspecific defense Reactions of the body against microbes, tumor cells, and virus-infected cells.

3) Participation in specific (immune) defense reactions.

Lymphocytes are one of the MAIN TYPES OF leukocytes. They are found not only in the blood; they are particularly abundant in the lymph. The sources of lymphocyte development are the red bone marrow and Lymphoid Organs, from which they enter the blood and lymph. The lifespan of different lymphocytes varies significantly, ranging from a few hours to many years.

Functions of lymphocytes:

1. Providing immune responses—specific defense against foreign and altered self-Antigens.

2. Regulation of the activity of other Cell types in immune reactions, growth processes, and tissue regeneration.

The size of lymphocytes varies widely. They are classified into three groups based on their morphological and functional characteristics: small, medium, and large lymphocytes.

Small lymphocytes are the most numerous group and are considered small cells. The Nucleus of small lymphocytes is round, oval, or kidney-shaped, occupying up to 90% of The Cell area.

Medium lymphocytes account for about 10% of all lymphocytes in human blood. Morphologically, they are similar to small lymphocytes, but their nucleus is lighter.

Large lymphocytes are found in significant numbers only in lymphoid tissue and are absent from the blood. They are characterized by a relatively light nucleus of a round or kidney-shaped form.

Depending on the type of immune reactions, T-lymphocytes and B-lymphocytes are distinguished.

T-lymphocytes develop in the Thymus and participate in cell-mediated Immunity, destroying genetically foreign cells.

B-lymphocytes provide humoral immunity and are capable of differentiating into effector cells—plasma cells. When foreign substances, or antigens, enter the body, plasma cells produce specific proteins—immunoglobulins (Antibodies)—which destroy these foreign antigens. B-lymphocytes have a short lifespan (weeks to months) and constitute about 20% of all blood lymphocytes.

Hematopoiesis (Hemopoiesis)

Hemopoiesis refers to The Development of blood. A distinction is made between embryonic hemopoiesis, which leads to the development of blood as a tissue, and postembryonic hemopoiesis, which is The process of physiological blood regeneration. The organs where hematopoiesis occurs are called Hematopoietic organs. These include the red bone marrow of flat bones and the epiphyses of long bones, the spleen, Lymph Nodes, and the thymus.

The hematopoietic tissue of the red bone marrow is called myeloid tissue, and the process of formation of erythrocytes, granulocytes, monocytes, and platelets is termed myelopoiesis. The hematopoietic tissue located in the spleen, lymph nodes, and thymus (as well as The system of these organs) is called lymphoid tissue, and the process of lymphocyte and plasma Cell Formation within them is called lymphopoiesis.

All used elements of blood originate from a single progenitor cell called the hematopoietic stem cell. The hematopoietic stem cell is a pluripotent progenitor of all blood cells and belongs to a self-renewing cell population.

The following types of hemopoiesis exist:

✵ Erythropoiesis - the development of erythrocytes;

✵ Granulocytopoiesis - the development of granulocytes (neutrophils, eosinophils, basophils);

✵ Lymphopoiesis - the development of T- and B-lymphocytes;

✵ Monocytopoiesis - the development of monocytes;

✵ Thrombocytopoiesis - the development of Blood Platelets (thrombocytes).

Blood groups

Antigens are located on the membrane of erythrocytes. More than 400 antigens are known. The most important of these are the antigens of the ABO system.

It is this antigenic Specificity that determines blood groups. In the ABO system, three antigens are distinguished: A, B, and H. They are called agglutinogens. The ABO system contains two antibodies: a (alpha) and b (beta). They are called agglutinins.

Since ancient times, attempts have been made to transfuse blood from animals to humans, or from human to human. However, this almost always led to the patient's death. The cause of death after such blood transfusions was the clumping of erythrocytes in the vessels (agglutination), followed by hemolysis and blockage of 30

capillaries and, as a consequence, so-called hemotransfusion Shock developed (hemo - blood, transfusion - transfusion).

What causes erythrocyte agglutination? Agglutination occurs due to the agglutinogen-agglutinin reaction. Agglutination followed by hemolysis is observed only when matching agglutinins and agglutinogens meet - a and A, b and B. There is no agglutinin for the H agglutinogen in blood serum.

Matching agglutinogens and agglutinins are never found in the blood of the same individual.

Based on the presence of certain agglutinogens and agglutinins, human blood in the ABO system is divided into 4 groups (with "O" retained instead of "H" out of respect for Landsteiner, the discoverer of agglutinogens):

I (O) - the erythrocytes contain "O" agglutinogens, and the plasma contains a and b agglutinins.

II (A) - the erythrocytes contain "A" agglutinogens, and the plasma contains b agglutinin.

III (B) — the erythrocytes contain B agglutinogens, and the plasma contains a agglutinin.

IV (AB) - the erythrocytes contain A and B agglutinogens, and there are no agglutinins in the plasma.

Rh factor, Rh incompatibility

In 80% of people, The erythrocyte membrane contains the so-called Rh factor. It is determined by the presence of C, D, and E antigens in the erythrocyte membrane. The D-agglutinogen is dominant: if it is present in erythrocytes, such blood is considered Rh-positive (Rh+), and in its absence, Rh-negative (Rh-). 15% of people are Rh-.

Unlike the agglutinogens of the ABO system, blood plasma does not naturally contain agglutinins or anti-Rh antibodies. However, if an Rh-negative patient is repeatedly transfused with Rh-positive blood, specific anti-Rh agglutinins are produced in response to the introduced Rh-agglutinogen. This leads to an agglutinogen-agglutinin interaction and, consequently, the agglutination and hemolysis of erythrocytes, resulting in the development of hemotransfusion shock.

The Rh factor is of great importance for the normal course of Pregnancy. If an Rh-negative mother carries an Rh-positive fetus, the fetal Rh-agglutinogens penetrate the mother's blood, leading to The formation of anti-Rh agglutinins in her blood. During subsequent pregnancies, these antibodies can cross into the fetus, causing hemolysis and agglutination; the fetus may be born with hemolytic jaundice or may even die.

Blood transfusion

People who donate blood are called Donors, and people who receive blood are called recipients. During blood transfusion, it is crucial that the donor's erythrocyte agglutinogens are not agglutinated by the recipient's blood agglutinins, which would lead to hemolysis, capillary blockage, hemotransfusion shock, and death. The donor's blood agglutinins are of less concern because they are diluted in the recipient's blood and lose their ability to agglutinate the recipient's erythrocytes.

Universal donor - group I. Universal recipient - group IV.

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Blood typing Procedure using group I, II, and III sera, with the donor's blood drop being 10 times smaller. Additional testing with standard group IV serum.

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