Lecture 31: Cells Of The Blood Flashcards
The general functions of blood include transportation, regulation and protection.
Describe each of these functions
Transportation functions:
-Carries O2 and nutrients to the cells
-transports CO2 and wastes from from the tissues to the lungs and the kidneys where wastes can be removed from the body
-carries hormones to target tissues
Regulation functions:
-helps to regulate body temperature by removing heat from active areas and transporting it to other areas, such as the skin, so heat can be dissipated
-plays a significant role in fluid and electrolyte balance
-function in pH regulation through the action of buffers in blood
Protective functions:
-Clotting mechanisms prevent blood loss through hemorrhage
-white blood cells engulf and destroy infectious agents
What is the composition of blood?
Plasma is the liquid portion of the blood
-plasma is about 90% water and the remaining 10% consists of different organic and inorganic solutes.
Plasma proteins are the most abundant solutes in the plasma:
-these proteins remain in the blood and interstitial fluid and aren’t used for energy. The three major classes if plasma proteins ate albumins, globulins, and fibrinogen
What are the three major classes if plasma proteins?
Albumins: most abundant type plasma proteins. They contribute to the osmotic pressure of the blood and play an important role in maintaining fluid balance between blood and interstitial fluid
Globulin: there are three types of globulins: alpha, beta and gamma. Alpha and beta globulins are produced in the liver and function in transporting lipids and fat-soluble vitamins in the blood. Gamma globulins are the antibodies that function in immunity.
Fibrinogen-is necessary for blood clotting.
What are the minor constituents of plasma?
Nutrients include: glucose, lipids and amino acids
- metabolic end products include: uric acid, urea, lactic acid and creatinine
- dissolved gases: oxygen and carbon dioxide
- other proteins including: hormones, enzymes, antibodies
What are the cellular components of blood?
The three classes of cells and cell fragments are:
Erythrocytes or red blood cells
Leukocytes or white blood cells
Thrombocytes or platelets
What is the function of erythrocytes or red blood cells?
- Red blood cells are primarily responsible for tissue oxygenation
- the flattened bi concave shape provides for a surface area that is optimal for diffusion.
- reversible deformity enables the erythrocyte to change shape and be able to squeeze through small tubes
- red blood cells contain haemoglobin a carrier protein that easily and reversible binds oxygen. Each cell contains about 250 million haemoglobin which can carry 4 O2 molecules each
- red blood cells can’t undergo mitosis, and lasts for about 120 days then are replaced
What is the function of Leukocytes or white blood cells.
- defend body against infection and remove debris
- much less in the blood than red blood cells
- Leukocytes have nuclei
- named for their structure as being either granulocytes (with granules) or agranulocytes (without granules)
- the granulocytes which include neutrophil, basophils and eosinophils are all phagocytes.
- of the agranulocytes, the monocytes and macrophages are phagocytes whereas the lymphocytes are immunocytes (cells that create immunity)
Name and describe the functions of the different types of Leukocytes
- Neutrophils: active in ingesting bacteria, many found in pus wounds. They are the more common Leukocytes
- Basophils: secrete substances that mediate the hypersensitivity reactions such as histamines and serotonin.
- Eosinophils: attack parasites and phagocytose antigen-antibody complexes
- Lymphocytes: main constituents of the immune system that defend against the attack of pathogenic micro organisms such as viruses, bacteria and fungi.
- Macrophages and monocytes: active in immune and inflammatory response because they are powerful phagocytes.
- ingest dead or defective host cells, in particular blood cells.
- monocytes are essentially immature macrophages.
- after monocytes are formed and released by bone marrow, they enter the blood stream and circulate for about 36 hrs while they mature into macrophages.
How does phagocytosis by macrophages and neutrophils occur?
- macrophages and neutrophils are professional “phagocytes” or cell eaters. They use their internal cytoskeleton to envelop the enemy cells
- to ensure that the organisms not grow and divide within them they have an oxidative burst-phagocytes generate toxic concentration of hydrogen peroxide and other oxidants.
Each type of white blood cell is present in the blood in different proportions:
Neutrophil- 50-70% Eosinophil- 2-4% Basophil- 0.5-1% Lymphocyte -20-40% Monocytes- 3-8%
Platelets
- not cells but cytoplasmic fragments formed from megakaryocytes.
- platelets are essential for coagulation and control of bleeding
- lack nucleus
- form “platelet plug” to help stop blood flow
Formation of blood cells:
The red, white and clotting cells enter bloodstream after maturation process called hematopoiesis, which begins with the production of immature cells in the blood forming tissue of the bone marrow.
-cell division and differentiation during hematopoiesis are balanced by aptosis (must be steady state of differentiation and cell death)
-the original cells involved in blood cell productions are called pluripotent stem cells, meaning that they contain the potential to develop the characteristics of all different cell types which make up the major blood cell lines
The myeloid line- produces the white cells
The lymphoid line- produces lymphocytes
What are hematopoitic stem cells?
- in bone marrow
- continuously generate terminally differentiated blood cells of all different lineages eg erythrocytes, granulocytes or macrophages.
- sustain own maintenance- a condition called cell self-renewal
Major characteristic of hematopoietic stem cells:
- they are parent cells to all cells that circulate in blood
- they are morphologically indistinguishable from small to medium sized lymphocytes
- they reside primarily in the bone marrow but migrate freely in the peripheral blood
- these stem cells may do one of 3 things
1. Rest for long intervals without dividing in a so-called prolonged intermitotic interval
2. Divide without differentiating further
3. Differentiate down any one of the myeloid or lymphoid pathways of development - hematopoietic stem cells in the bone marrow can either self-renew or give rise to progenitor cells that generate precursors of the myeloid or the lymphoid lineage.
- cell become more committed with each hormonal signal and cell division to become distinct cell lineages and achieve cell differentiation for each type of blood cell
Hormonal control of red blood cell production
Erythropoietin (EPO) is the hormone that fine-tunes red blood cell production, it is produced primarily by cells in the kidney when oxygen delivered to these cells diminishes.
-they produce erythropoietin that then circulates in the blood to the bone marrow, were it binds to receptors on the surface of erythroid precursor cells, causing them to divide and mature
