Lecture 2 Flashcards
What is a differential white blood cell count?
What is the total differentiated wbc count?
What are the two main types of wbcs? And give examples under each as well as the percentage of the examples in the wbcs.
A count that looks at the different components of the WBCS.
What is do the wbcs under granulocytes plus monocytes have in common?
They are all from the mixed myeloid progenitor.
The unit of WBCS is per litre of blood. So the normal differentiated wbc count in total is 4800-10,800/litre
The two main types of wbcs are granulocytes (neutrophils (50-70%),eosinophils(2-4%),basophils(0.5-1%)) and agranulocytes(lyphocytes(25-45%),monocytes(3-8%)
What is do the wbcs under granulocytes plus monocytes have in common?
Which cell is differentiated into t and b lymphocytes which are agranulocytes?
They are all from the mixed myeloid progenitor lineage
Lymphoid progenitor differentiates into T and B lymphocytes
Which part of granulocytes stain specifically with weights stain?
State three other characteristics of granulocytes
Cytoplasmic granules of the granulocytes stain with wrights stain. Cytoplasmic granules of granulocytes (neutrophils, eosinophils, and basophils) stain with Wright’s stain due to their specific chemical composition and affinity for the stain components. Wright’s stain is a combination of eosin (an acidic dye) and methylene blue (a basic dye), which allows it to differentiate various cellular components based on their chemical properties.
Here’s why the granules stain as they do:
- Neutrophils: Their granules contain neutral substances that take up both eosin and methylene blue, resulting in a lilac or light pink color.
- Eosinophils: Their granules are rich in proteins that have a high affinity for eosin, an acidic dye. As a result, the granules stain a bright red or orange color.
- Basophils: Their granules contain heparin and histamine, which have a high affinity for methylene blue, a basic dye. Consequently, the granules stain dark purple or blue.
Wright’s stain exploits these affinities, allowing for the clear differentiation of granulocytes based on the color of their cytoplasmic granules. This differential staining is essential for identifying and studying different types of blood cells under a microscope.
Other characteristics: they are larger and shorter lived than RBCS
THEY have a lobed nuclei
They are phagocytic
What is the wrights stain?
How are rbcs,wbcs and platelets viewed under the microscope when they are stained using the weights stain?
Wright’s stain is a type of histologic stain used primarily in hematology to differentiate blood cell types and to diagnose various blood disorders. It is a modification of the Romanowsky stain and contains a combination of eosin (an acidic dye) and methylene blue (a basic dye), which together help to visualize different components of blood cells.
- Red Blood Cells (RBCs): Appear pink to orange.
- White Blood Cells (WBCs): Nuclei stain purple to blue, while the cytoplasm varies depending on the cell type (e.g., eosinophils stain pink-red due to eosinophilic granules).
- Platelets: Appear as small purple granules.
Wright’s stain is crucial for routine blood examination and plays an essential role in clinical pathology and hematological studies.
- Components: The stain typically contains eosin Y (which stains cytoplasm and other acidic components pink to red) and methylene blue (which stains nuclei and other basic components blue to purple).
- Applications: Wright’s stain is commonly used to stain peripheral blood smears and bone marrow aspirates. It helps in identifying and differentiating various blood cell types, including red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
- Diagnostic Use: It is widely used in the diagnosis of blood disorders such as anemia, leukemia, infections, and other hematological abnormalities.
- Sample Preparation: A drop of blood is spread on a glass slide to create a thin smear.
- Fixation: The smear is usually air-dried and then fixed with methanol.
- Staining: The slide is stained with Wright’s stain for a specific duration, allowing the dyes to interact with the cellular components.
- Rinsing and Drying: The slide is then rinsed with distilled water or buffer solution and allowed to air dry.
- Microscopy: The stained slide is examined under a microscope for detailed cellular analysis.
Which of the WBCS is the most abundant or numerous?
What are they sometimes referred to as?
The fine granules of this type of wbcs take up both acidic and basic dyes true or false?
What do the granules of this type contain?
This type of wbcs give the cytoplasm a lilac color and are very very phagocytic “bacteria slayers” true or false
Neutrophils.
They are sometimes called polymorphonuclear leukocytes (PMN). The neutrophils have 3-5lobes usually that’s why they are called polymorphonuclear . Poly for many, morpho for their morphology and nuclear as in their nucleus
You are correct in noting that the different components of neutrophils pick up different stains. Here’s a more precise explanation:
- Granules: The fine granules of neutrophils take up both acidic (eosin) and basic (methylene blue) dyes, which combine to give the granules a neutral lilac or light pink color. This dual affinity is why they appear lilac when stained with Wright’s stain.
- Nucleus: The nucleus of neutrophils picks up the basic dye (methylene blue), which stains the nucleus a dark blue or purple color.
So, while the granules of neutrophils are neutral and take up both dyes, the nucleus specifically picks up the basic dye, resulting in a darker color. This staining pattern helps differentiate the cellular components under the microscope.
Neutrophils are the most abundant type of white blood cells (WBCs).
-
What are they sometimes referred to as?
They are sometimes referred to as polymorphonuclear leukocytes (PMNs) or polys due to their multi-lobed nucleus. -
The fine granules of this type of WBCs take up both acidic and basic dyes: true or false?
True. The fine granules of neutrophils take up both acidic (eosin) and basic (methylene blue) dyes, giving them a lilac or light pink color. -
What do the granules of this type contain?
The granules of neutrophils contain enzymes and antimicrobial proteins, such as:- Myeloperoxidase
- Lysozyme
- Defensins
- Lactoferrin
-
This type of WBCs gives the cytoplasm a lilac color and is very phagocytic “bacteria slayers”: true or false?
True. Neutrophils give the cytoplasm a lilac color due to their granules taking up both acidic and basic dyes, and they are very phagocytic, often referred to as “bacteria slayers” due to their role in engulfing and destroying bacteria.
Eosinophils digest which type of organisms? And why? What type of granules do they have?
What type of nuclei do they have? What color do they pick up when they are stained?
Digest parasitic worms that are too large to be phagocytized.
They have a bilobed nuclei
Are stained red in H and E staining. The eo in the eosinophils is for the red color. (Hematoxylins and eosin (H&E) staining is one of the most widely used techniques in histology and pathology for examining the detailed structure and morphology of tissues. This staining method provides excellent contrast, making it easier to differentiate between various tissue components.)
They have lysosome like granules(like neutrophils do but basophils don’t have such granules )
They are red to crimson(acidophilic) coarse
They are modulators of the immune response
Eosinophils can be stained with both Wright’s stain (which includes methylene blue and eosin) and H&E stain (hematoxylin and eosin). Here’s why and how they stain differently with each:
-
Wright’s Stain (Methylene Blue and Eosin):
- Methylene Blue: This is a basic dye that stains acidic components, such as nucleic acids, blue.
- Eosin: This is an acidic dye that stains basic components, such as proteins in the granules, red or pink.
- Eosinophils: The granules in eosinophils have a strong affinity for eosin because they are basic (contain proteins that are positively charged). Therefore, when stained with Wright’s stain, the granules take up eosin and appear bright red or orange. The nucleus, being acidic, takes up the methylene blue and stains dark blue or purple.
-
H&E Stain (Hematoxylin and Eosin):
- Hematoxylin: This is a basic dye that binds to acidic structures, staining them blue to purple.
- Eosin: This is the same acidic dye used in Wright’s stain and stains basic structures pink to red.
- Eosinophils: The same principle applies here: the granules in eosinophils have an affinity for eosin and thus stain bright red or orange, while the nucleus stains blue to purple with hematoxylin.
Why Eosinophils Aren’t Exclusively Stained with One Type:
- Wright’s Stain: It is commonly used in blood smears and differentially stains all types of blood cells, including eosinophils, allowing for identification and differentiation based on the staining characteristics of their granules and nuclei.
- H&E Stain: It is widely used in histology for tissue sections, providing clear differentiation between different tissue structures and cell types, including eosinophils.
Both staining methods can effectively highlight eosinophils, but they are used in different contexts (blood smears vs. tissue sections) and leverage different dye combinations to achieve similar results for these particular cells.
Explain the parts of the cell that the H and E stain in H and E staining
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Hematoxylin:
- Function: Stains cell nuclei.
- Color: Blue to purple.
- Mechanism: Hematoxylin is a basic dye that binds to acidic components of the cell, particularly nucleic acids in the cell nucleus, resulting in blue or purple staining.
-
Eosin:
- Function: Stains the cytoplasm and extracellular matrix.
- Color: Pink to red.
- Mechanism: Eosin is an acidic dye that binds to basic components of the cell, such as proteins in the cytoplasm and extracellular matrix, resulting in pink to red staining.
Which of the WBCS are the rarest?
Basophils
Which of the Wbcs are functionally similar to mast cells
Basophils.
Mast cells release histamine for vasodilation. So example of cells that release histamine for vasodilation are basophils and mast cells
Mast cells have many many granules about 1000s and are usually found in tissues. They also contain heparin. Are involved in formation of blood vessels or angiogenesis and are involved in hypersensitivity reactions
Basophils are found in circulating blood cells and have lower granules number and also contain heparin plus histamine but are not involved in angiogenesis. Just inflammation
Basophils also contain granules, but their composition and function are distinct from those of neutrophils and eosinophils. The granules in basophils are:
-
Large Basophilic Granules: These granules stain dark blue to purple with basic dyes (such as methylene blue in Wright’s stain) due to their high content of acidic substances. The main components of these granules include:
- Histamine: A vasoactive amine that plays a key role in inflammatory responses, particularly in allergic reactions. It causes vasodilation and increased vascular permeability.
- Heparin: An anticoagulant that helps to prevent blood clotting.
- Various Enzymes: Such as proteases that contribute to the breakdown of proteins and other substrates during immune responses.
These granules do not have the same lysosome-like properties as the granules in neutrophils or eosinophils, but they are crucial for basophils’ role in mediating allergic reactions and inflammation. Basophils are less involved in direct pathogen destruction and more in the regulation of immune responses through the release of their granule contents.
Both basophils and eosinophils are involved in hypersensitivity reactions, but they play different roles:
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Basophils:
- Basophils are closely associated with Type I hypersensitivity reactions (immediate hypersensitivity), which include allergic reactions such as asthma, hay fever, and anaphylaxis.
- They release histamine and other mediators from their granules in response to the binding of allergens to IgE antibodies on their surface. This release contributes to the symptoms of allergic reactions, such as vasodilation, increased vascular permeability, and smooth muscle contraction.
-
Eosinophils:
- Eosinophils are involved in late-phase reactions of Type I hypersensitivity and are also important in Type II hypersensitivity reactions (antibody-dependent cellular cytotoxicity) and Type IV hypersensitivity reactions (delayed-type hypersensitivity).
- They play a key role in responding to parasitic infections and are recruited to sites of allergic inflammation. Eosinophils release cytotoxic granule proteins, such as major basic protein and eosinophil cationic protein, which can damage tissues and contribute to inflammation.
- Eosinophils help modulate the immune response by releasing cytokines and chemokines that can influence other immune cells.
In summary, basophils are primarily associated with the immediate phase of hypersensitivity reactions, particularly in allergies, while eosinophils are involved in the later stages of allergic reactions and play a broader role in various types of hypersensitivity reactions and in defense against parasitic infections.
Which of the wbcs have large,purplish black or blue or deep purple granules that contain histamine
Basophils
Histamine is an inflammatory chemical that acts as a vasodilator and attracts other wbcs to inflamed sites
Platelets granules are smallish and purple but not deep purple
Which type of cell has two lobed nuclei with cytoplasmic granules staining red?
Which type is a multilobed nucleus?
Which type has a bilobed nucleus with purplish black cytoplasm granules
Eosinophils
Neutrophils
Basophils
Band cells are also bilobed
Bilobed nucleus you can think of landline telephone. One side of it is a lobe of the nucleus and the other is another lobe
Why are agranulocytes called so?
What is the shape of their nuclei?
Called so because they lack visible cytoplasmic granules.
They have spherical or kidney shaped nuclei
Spherical for lymphocytes and kidney for monocytes
Which cells have a large dark purple circular nuclei with a thin rim of blue cytoplasm?
Lymphocytes
In an MCQ setting, you should pick lymphocytes.
Lymphocytes are characterized by their large, dark purple circular nucleus that occupies most of the cell, with only a thin rim of blue cytoplasm visible.
Basophils, on the other hand, have a bilobed or S-shaped nucleus that is often obscured by their large, dark purple granules in the cytoplasm, giving them a more granular appearance rather than the distinct large nucleus with a thin cytoplasmic rim seen in lymphocytes.
While eosinophils have red cytoplasm
Where are lymphocytes usually found?
What are the two types of lymphocytes and state their functions
Which are cytotoxic and what MHC class does this type of lymphocyte interact with?
In the lymphoid tissue. Few circulate in the blood.
That’s correct:
- Basophils: These are primarily found in the circulation (bloodstream). They make up a very small percentage of circulating white blood cells (less than 1%). Basophils play a role in allergic reactions and inflammatory responses, but they are not as commonly found in tissues.
- Lymphocytes: These are more commonly found in lymphoid tissues such as the lymph nodes, spleen, tonsils, and mucosa-associated lymphoid tissues (MALT). However, they do circulate in the blood as well. Lymphocytes are crucial for adaptive immunity, including the production of antibodies and cell-mediated immunity.
So, in the context of where they are most commonly found, basophils are more prevalent in the circulation, while lymphocytes are more abundant in lymphoid tissues.
Two types
•T cells act against virus-infected cells and tumor cells. (We have cd8 T cells which are cytotoxic and then cd4 cells which are helper cells. CD8 T cells are cytotoxic and directly kill infected or malignant cells by recognizing MHC Class I molecules.
• CD4 T cells are helper cells that orchestrate the immune response by interacting with MHC Class II molecules on antigen-presenting cells and assisting other immune cells like B cells, CD8 T cells, and macrophages.)
•B cells give rise to plasma cells, which produce antibodies
Which cells are the largest leukocytes?
Monocytes
Which cells have dark purple standing in with U or B or kidney shaped or horseshoe nuclei?
Monocytes
Small lymphocytes generally have large spherical nucleus
The shape of the monocytes nucleus can also be used as a unique identifier for mature monocytes
Which cells have abundant pale blue cytoplasms
Monocytes
Correct, no part of the monocytes typically stains red with standard stains like Wright’s or Giemsa stain.
Monocytes are a type of white blood cell characterized by:
- Nucleus: The nucleus of a monocyte is large, often kidney-shaped or horseshoe-shaped, and stains a bluish or purple color with basic dyes (like methylene blue).
- Cytoplasm: The cytoplasm of monocytes typically stains pale blue or gray and may contain fine azurophilic granules, which are lysosomes, but these do not stain red. The granules can sometimes give the cytoplasm a slightly grainy appearance.
Red staining is usually associated with acidic dyes like eosin, which stains eosinophilic structures (like eosinophil granules) a red or pink color. Monocytes, however, do not have components that take up the acidic stain to appear red.
Which cells leave circulation,enter tissues and differentiate into macrophages?
Monocytes
Macrophages in circulation are monocytes. Once the monocytes enter tissues and differentiate, they become macrophages. So macrophages are differentiated monocytes
What are the functions of monocytes?
Actively phagocytic cells; crucial against viruses, intracellular bacterial parasites, and chronic infections(so neutrophils,eosinophils and monocytes(and macrophages which are differentiated monocytes) are phagocytic)
•they Activate lymphocytes to mount an immune response
What is leukopoiesis?
What stimulates this process?
Which interleukins play a role in this process?
What stem cells do leukocytes originate from?
Production of WBCs
•Stimulated by chemical messengers from bone marrow and mature WBCs:
-Interleukins (e.g., IL-5,IL-3)
-Colony-stimulating factors (CSFs) named for the WBC type they stimulate (e.g., granulocyte-CSF stimulates granulocytes)
•All leukocytes originate from Hemocytoblasts or hematopoietic stem cells
Or
Granulocyte-Colony Stimulating Factor (G-CSF)
• Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF)
• Interleukin-3 (IL-3)
• Interleukin-5 (IL-5)
What is leukopenia?
What is leukemia?
What are the two types of leukemia?
Which group of people does acute leukemia usually affect?
Which group does chronic leukemia usually affect?
Leukopenia
• Abnormally low WBC count—drug induced
•Leukemias:
Cancerous conditions involving WBCs
•Named according to the abnormal WBC clone involved
•Myelocytic leukemia involves myeloblasts
•Lymphocytic leukemia involves lymphocytes
•Acute leukemia involves blast-type cells and primarily affects children
•Chronic leukemia is more prevalent in older people
Leukemias are indeed cancers of the white blood cells (WBCs) and are named based on the specific type of WBC that is abnormally proliferating. While leukemias primarily involve WBCs, they can also affect red blood cells (RBCs) and platelets indirectly due to the impact on bone marrow function.
Leukemias and Their Naming:
Leukemias are classified based on two main criteria:
1. Cell Lineage (Myeloid or Lymphoid): Leukemias are named based on whether the cancer originates from the myeloid or lymphoid cell lines. • Myeloid Leukemias: Arise from myeloid precursors, which can differentiate into RBCs, platelets, neutrophils, eosinophils, basophils, or monocytes. • Lymphoid Leukemias: Arise from lymphoid precursors, which can differentiate into B cells, T cells, or natural killer (NK) cells
Explain the process of leukopoiesis
Which of the following is the correct pathway for the differentiation of a monocyte?
• A) Myeloid progenitor → Monoblast → Promonocyte → Monocyte
• B) Lymphoid progenitor → Monoblast → Promonocyte → Monocyte
• C) Myeloid progenitor → Myeloblast → Monoblast → Monocyte
• D) Myeloid progenitor → Lymphoblast → Promonocyte → Monocyte
Which of the following is the correct pathway for the differentiation of a granulocyte?
- A) Myeloid progenitor → Myeloblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
- B) Lymphoid progenitor → Myeloblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
- C) Myeloid progenitor → Monoblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
- D) Lymphoid progenitor → Monoblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
**
### MCQ for Lymphocytes
Which of the following is the correct pathway for the differentiation of a lymphocyte?
- A) Lymphoid progenitor → Lymphoblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
- B) Myeloid progenitor → Lymphoblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
- C) Lymphoid progenitor → Monoblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
- D) Lymphoid progenitor → Myeloblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
Leukopoiesis is the process by which white blood cells (leukocytes) are produced from hematopoietic stem cells (HSCs) in the bone marrow.
Which of the following is the correct pathway for the differentiation of a monocyte?
• A) Myeloid progenitor → Monoblast → Promonocyte → Monocyte
• B) Lymphoid progenitor → Monoblast → Promonocyte → Monocyte
• C) Myeloid progenitor → Myeloblast → Monoblast → Monocyte
• D) Myeloid progenitor → Lymphoblast → Promonocyte → Monocyte
• Answer: A) Myeloid progenitor → Monoblast → Promonocyte → Monocyte
Here are similar MCQs for granulocytes and lymphocytes:
Which of the following is the correct pathway for the differentiation of a granulocyte?
- A) Myeloid progenitor → Myeloblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
- B) Lymphoid progenitor → Myeloblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
- C) Myeloid progenitor → Monoblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
- D) Lymphoid progenitor → Monoblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
Answer: A) Myeloid progenitor → Myeloblast → Promyelocyte → Myelocyte → Metamyelocyte → Granulocyte (e.g., Neutrophil)
Which of the following is the correct pathway for the differentiation of a lymphocyte?
- A) Lymphoid progenitor → Lymphoblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
- B) Myeloid progenitor → Lymphoblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
- C) Lymphoid progenitor → Monoblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
- D) Lymphoid progenitor → Myeloblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
Answer: A) Lymphoid progenitor → Lymphoblast → Prolymphocyte → Lymphocyte (e.g., T cell, B cell)
This process involves several stages of differentiation and maturation, leading to the formation of various types of leukocytes, including granulocytes, monocytes, lymphocytes, and others. Here’s a brief overview of leukopoiesis:
- Origin: All blood cells originate from multipotent hematopoietic stem cells in the bone marrow.
- Differentiation: HSCs have the potential to differentiate into all blood cell lineages through a series of intermediate progenitor cells.
- Common Myeloid Progenitor (CMP): Differentiates into myeloid cells, giving rise to granulocytes (neutrophils, eosinophils, basophils), monocytes, erythrocytes, and megakaryocytes (platelet precursors).
- Common Lymphoid Progenitor (CLP): Differentiates into lymphoid cells, giving rise to B cells, T cells, and natural killer (NK) cells.
- Myeloblast: The first committed myeloid precursor cell that differentiates into granulocytes.
- Promyelocyte: Develops from the myeloblast and begins to accumulate granules.
- Myelocyte: Further differentiation with more specific granule formation.
- Metamyelocyte: Immature granulocyte with a kidney-shaped nucleus.
- Band Cell: Precursor to mature granulocytes with a horseshoe-shaped nucleus.
- Mature Granulocytes: Fully differentiated neutrophils, eosinophils, and basophils.
- Monoblast: The first committed precursor in the monocyte lineage.
- Promonocyte: Develops from the monoblast and undergoes further differentiation.
- Monocyte: Mature monocytes are released into the bloodstream, where they can migrate into tissues and differentiate into macrophages or dendritic cells.
- Lymphoblast: The first committed precursor in the lymphoid lineage.
- Prolymphocyte: Intermediate stage of lymphocyte development.
- B Lymphocytes (B Cells): Mature in the bone marrow and migrate to peripheral lymphoid organs (e.g., spleen, lymph nodes) where they can differentiate into plasma cells and produce antibodies.
- T Lymphocytes (T Cells): Mature in the thymus and migrate to peripheral lymphoid organs, where they participate in cell-mediated immunity.
- Natural Killer (NK) Cells: Develop from CLPs and play a role in innate immunity by targeting infected or cancerous cells.
Leukopoiesis is a complex process involving the differentiation of hematopoietic stem cells into various types of white blood cells through distinct myeloid and lymphoid lineages. This process ensures the continuous production of leukocytes required for immune defense and homeostasis.
So in summary:
Hematopoietic stem cells differentiate into myeloid and lymphoid stem cells. The myeloid go on to form myeloblasts and lymphoid go to form lymphoblasts. At this point, they are both committed to becoming the cells that they have to become.
The myeloblasts become promyelocytes and promonocytes. The promyelocytes go on to form neutrophils,basophils and eosinophils while the promonocytes go on to form the monocytes.
The promyelocytes become neutrophilic myelocytes ,basophilic myelocytes and eosinophilia myelocytes then they become neutrophilic band cells ,basophilic band cells and eosinophilia band cells before they finally become neutrophils basophils and eosinophils.
Promonocytes just go straight to be monocytes.
For lymphoblasts, they move on to become pro lymphocytes and then to become lymphocytes
What are platelets?
What regulates its formation?
Platelets
•Small fragments of megakaryocytes
•Formation is regulated by thrombopoietin
•
Which cells have blue staining in their outer region and have purple granules
Platelets
Platelet granules contain what components
Blue-staining outer region, purple granules
•Granules contain serotonin, Ca2+, enzymes, ADP, and platelet-derived growth factor (PDGF)
What is the use of platelets
What comes to stabilize the platelets after it has come to do its initial work?
Circulating platelets are kept inactive and mobile by what two things?
Form a temporary mechanical platelet plug that helps seal breaks in blood vessels during the hemostatic response to vascular injury.
fibrin forms a more stable and permanent clot following the initial platelet plug. Here’s how it works:
1. Platelet Plug: When a blood vessel is injured, platelets quickly adhere to the site and to each other, forming a temporary “platelet plug” that helps stop initial bleeding. 2. Fibrin Clot: The coagulation cascade is then activated, leading to the conversion of fibrinogen into fibrin. Fibrin strands weave through the platelet plug, reinforcing and stabilizing it. This creates a stronger, Durable clot that effectively seals the wound until the vessel can be repaired •Circulating platelets are kept inactive and mobile by NO and prostacyclin from endothelial cells of blood vessels Nitric oxide and prostacyclin are vasodilators
