Blood - Chapter 17

What are the 3 main functions of blood?

1. Transportation

2. Regulation

3. Protection

What does the function Transportation do with blood?

Blood helps to carry oxygen, nutrients, hormones, and waste products throughout the body.

What does Regulation mean according to blood?

Blood helps to regulate body temperature, pH levels and fluid balance.

How does blood help protect?

Blood provides immune defence (via leukocytes and antibodies) and aids in blood clotting (through platelets and clotting factors)

What is the composition and physical characteristics of whole blood?

• 55% is plasma

• 45% is formed elements such as red, white blood cells and platelets)

• Whole blood is a red, viscous liquid. Usually with pH level of 7.35 to 7.45, temperature of aprox 38 degrees.

• Whole blood is usually in high volumes of 5 to 6 litres in an adult human

Describe the structure of Erythrocytes?

• small bi-concave discs, lacking organelles and nucleus to make more room for haemoglobin, the oxygen carrying molecule.

• erythrocytes also have a flexible plasma membrane.

Describe the function of Erythrocytes?

• Primarily transport oxygen from the lungs to the rest of the body while also transporting carbon dioxide from the body to the lungs for exhalation.

Describe the production of Erythrocytes?

• Bone marrow makes most of your red blood cells. Once they're fully mature, they're released into your bloodstream, where they transport oxygen throughout your body.

What are the first 4 stages of erythrocyte production?

• Hematopoietic Stem Cell (HSC): The process begins with a multipotent HSC in the bone marrow. 

• Myeloid Progenitor: The HSC differentiates into a myeloid progenitor cell. 

• Erythroid Progenitor: The myeloid progenitor further differentiates into an erythroid progenitor cell. 

• Proerythroblast: The erythroid progenitor develops into a proerythroblast, the first recognizable erythroid precursor. 

What are the last 4 stages of Erythrocytes production?

• Erythroblast: The proerythroblast matures into an erythroblast, characterized by the synthesis of hemoglobin. 

• Normoblast: The erythroblast further develops into a normoblast, which undergoes nuclear condensation and eventual expulsion. 

• Reticulocyte: With the nucleus expelled, the cell becomes a reticulocyte, an immature red blood cell. 

• Erythrocyte: The reticulocyte matures into a fully functional, mature erythrocyte, or red blood cell.

Describe the composition of Haemoglobin?

• Is a protein composed of four polypeptide globin chains, each attached to a heme group containing an iron atom

• Heme Structure:

  The heme group consists of an organic protoporphyrin ring with a central iron ion in the ferrous state (Fe2+

• Quaternary Structure:

  The arrangement of the four globin chains and heme groups is known as the quaternary structure. This structure is crucial for the protein's function and its ability to bind oxygen cooperatively. 

The main classes of Leukocytes?

• Granulocytes (presence of granules)

  (- contain Neutrophils, Eosinophils, Basophils)

• Agranulocytes (absence of granules)

  ( - contains Lymphocytes, Monocytes)

What are the functions of Leukocytes?

• Neutrophils: The most abundant type, they are the first responders to infection and engulf bacteria and fungi. 

• Eosinophils: Primarily involved in combating parasitic infections and allergic reactions. 

• Basophils: Release histamine and other chemicals involved in allergic and inflammatory responses. 

• Lymphocytes: Include T cells, B cells, and natural killer cells, which play crucial roles in adaptive immunity, targeting specific pathogens and cancer cells. 

• Monocytes: Mature into macrophages, which engulf pathogens, cellular debris, and activate other immune cells. 

What are the structural characteristics of Granulocytes Leukocytes?

• Granules in Cytoplasm:

  Granulocytes contain granules or sacs in their cytoplasm, which are filled with substances that aid in fighting infection. 

• Neutrophils:

  The most abundant granulocyte, characterized by a multi-lobed nucleus and granules containing degradative enzymes. They are rapid responders to infection and are efficient phagocytes. 

• Eosinophils:

  Involved in allergic reactions and parasitic infections. They contain granules with substances that can neutralize harmful substances. 

• Basophils:

  The least common granulocyte. They play a role in inflammation and allergic reactions, releasing histamine and heparin. 

What are the structural characteristics of Agranulocytes Leukocytes?

• No Granules: Agranulocytes lack granules in their cytoplasm. 

• Lymphocytes: Involved in specific immune responses, including antibody production and cell-mediated immunity. They have a large, round nucleus and a small amount of cytoplasm. 

• Monocytes: The largest leukocyte, with an ellipsoidal, often lobulated nucleus. They can differentiate into macrophages, which are phagocytic cells that engulf pathogens and cellular debris. 

How are leukocytes produced?

they originate from hematopoietic stem cells, which are multipotent cells in the bone marrow. These stem cells differentiate into various types of leukocytes, each with unique roles in the immune system.

What are the main stages of leukocyte production?

• Bone Marrow: The primary site for leukocyte production. 

• Hematopoietic Stem Cells: These are the precursor cells in the bone marrow from which all blood cells, including leukocytes, are derived. 

• Differentiation: Hematopoietic stem cells can differentiate into various leukocyte lineages, including myeloid and lymphoid cells. 

• Myeloid Lineage: This lineage gives rise to neutrophils, eosinophils, basophils, monocytes, and macrophages. 

• Lymphoid Lineage: This lineage gives rise to lymphocytes, such as T cells and B cells. 

• Regulation: The production and maturation of leukocytes are regulated by various factors, including colony-stimulating factors (CSFs) and interleukins. 

• Secondary Maturation: Lymphocytes also undergo further maturation in specific lymphatic tissues like the thymus and lymph nodes. 

What is the structure of platelet cells?

• Cell Fragments:

  Unlike red and white blood cells, platelets are not complete cells but rather fragments of larger cells called megakaryocytes. 

• Disk-like Shape:

  When inactive, platelets have a biconvex, discoid shape, resembling small lenses. 

• Surface Features:

  Activated platelets exhibit numerous membrane projections and express specific proteins like glycoprotein IIb/IIIa, which is crucial for platelet aggregation. 

• Internal Components:

  They contain granules filled with various substances (e.g., ADP, thromboxane A2, serotonin, calcium ions) that are released upon activation to promote clotting. 

• Membrane Composition:

  The platelet membrane contains phospholipids like phosphatidylserine and phosphatidylethanolamine, which play a vital role in the coagulation cascade by providing a surface for clotting factors. 

What is the function of platelet cells?

1. Haemostasis (Stopping Bleeding):

The main function of platelets is to initiate and participate in haemostasis, the process of stopping bleeding. 

2. Adhesion:

Upon injury to a blood vessel, platelets adhere to the exposed subendothelial collagen and von Willebrand factor at the site of injury. 

3. Activation:

Adhesion triggers platelet activation, causing them to change shape, express new surface proteins, and release granular contents. 

4. Aggregation:

Activated platelets stick to each other (aggregation) via fibrinogen and other molecules, forming a platelet plug at the injury site. 

5. Fibrin Clot Formation:

The platelet plug is reinforced by the formation of a fibrin clot, which is the final stage of haemostasis and seals the wound. 

6. Wound Healing:

Fibrin also provides a scaffold for tissue repair and wound healing. 

7. Immune Response:

Platelets can also participate in immune responses by interacting with leukocytes and contributing to inflammation. 

8. Biomarkers:

Platelet indices like MPV, PDW, and PCT can be used as non-invasive biomarkers for assessing disease states. 

How are platelets formed?

1. Megakaryocytes:

   These large cells reside in the bone marrow and are responsible for platelet production. 

   2. Proplatelet Formation:

   Mature megakaryocytes extend long, branching protrusions called proplatelets into the bloodstream. 

   3. Platelet Release:

   These proplatelets break off from the megakaryocyte, forming individual platelets. 

   4. Thrombopoietin (TPO):

   This hormone, primarily produced in the liver, is the main regulator of megakaryocyte development and platelet production. 

   5. Regulation: The process is also influenced by various other factors, including growth factors and cytokines. 

What is the process for haemostasis?

1. Vascular Spasm:

   When a blood vessel is injured, the smooth muscle in its walls constricts, reducing blood flow to the area. This is a temporary mechanism that buys time for the next steps in hemostasis. 

2. 2. Platelet Plug Formation:

   Platelets, small cell fragments in the blood, are activated by exposure to collagen and other molecules in the damaged vessel wall. They adhere to the site of injury, aggregate (stick together), and release chemicals that attract more platelets, forming a temporary plug to seal the leak. 

3. 3. Coagulation (Blood Clotting):

   A cascade of enzymatic reactions, involving clotting factors, is triggered to create a stable fibrin clot. This process strengthens the platelet plug, forming a more durable barrier against blood loss. 

4. 4. Clot Retraction and Fibrinolysis:

   Once the tissue has started to heal, the clot retracts, squeezing out serum and further stabilizing the wound. Eventually, the clot dissolves through a process called fibrinolysis, restoring the vessel to its normal state. 

What is the process of blood oxygen haemostasis?

What is the name of the process for leukocyte production?

leukopoiesis

What is the name of the process for erythrocytes production?

erythropoiesis

What is the name of the process for platelet production?

thrombopoiesis

What is the name of the process for new blood cells production?

haematopoiesis

What is the process of haematopoiesis?

1. Hematopoietic Stem Cells (HSCs): 

• HSCs are the starting point of hematopoiesis and reside in the bone marrow.

• They have the ability to both self-renew (create more HSCs) and differentiate into progenitor cells.

2. Progenitor Cells: 

• HSCs differentiate into two main types of progenitor cells: common myeloid progenitors and common lymphoid progenitors.

• These progenitor cells are committed to specific cell lineages but cannot self-renew.

3. Myeloid Progenitors: 

• Myeloid progenitors develop into various blood cell types, including red blood cells (erythrocytes), platelets (thrombocytes), and several types of white blood cells (granulocytes like neutrophils, eosinophils, and basophils, as well as monocytes).

4. Lymphoid Progenitors: 

• Lymphoid progenitors develop into lymphocytes, which include B cells, T cells, and Natural Killer (NK) cells.

5. Mature Blood Cells: 

• Through a series of further divisions and differentiations, the progenitor cells give rise to the mature blood cells that circulate in the bloodstream.

6. Regulation: 

• Hematopoiesis is a highly regulated process, with growth factors called cytokines playing a crucial role in controlling the survival, self-renewal, and differentiation of HSCs and their progeny.

7. Sites of Hematopoiesis:

• In adults, the bone marrow is the primary site of hematopoiesis. 

• During embryonic development, hematopoiesis occurs in different locations, such as the yolk sac, liver, and spleen, before shifting to the bone marrow.