BLOOD

Question 1

Composition of the peripheral blood

Answer 1

General

• Fluid CT that circulates in cardiovascular system
  
  • consits of cells and extracellular componets
• cells are suspended in extracellular fliuf called plasma
• Within a closed circularoty system
  
  • 5L in male and 4.5 L in women, 7-8% of body weight
• Examination of blood cells required special prepriation and staining

Function:

• deliver nutrients
• remove metabolic by products
• transport and exhcange blood gasses
• transport hormoned to targeted tissue
• particiapte in the bodies immune responses
• participation in coagulation and thermoregulation

Composition

• Cells and their derivatives: (45%)
  
  • Erythrocytes= RNC
    
    • volume fo packed erthocytes in a blood sample=hematocrit
      
      • 35-45% of total blood volume
  • Usually contained in a “buffy coat” in a blood sample that has been centrifuged
    
    • Leukocytes= WBC
    • Thrombocytes= blood platletes
• Blood plasma: (55%)
  
  • ​the liquid extracellular materials that imparts fluid propterites to blood
  • Blood serum = plasma without clotting factors
  • Water: 91- 92 %
  • Blood gases (O2, CO2, N2, NO, H2S)
  • Electrolytes
    
    • (Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, PO43-, SO42-)
  • Nutrients (glucose, lipids, aminoacids)
  • Proteins
    
    • Albumin: main protien, made in liver, maintaing osmotic pressure on blood vessle wall- the correct porportion of blood to tissue fluid
    • Globulins
      
      • α-, β- antibodies, immune syste,m molecules secreted by plsama cells
      • γ- secreted by liver, help maintain osmostic pressure
    • Fibrinogen
      
      • made in liver
      • cascade of reaction for coagulation factors
      • forms fibrin fiber for clotting…
    • Nonprotein nitrogen substances (urea, uric acid, creatine, creatinine)
    • Regulatory substances (hormones, enzymes, vitamines)

Blood element: blood cell count (number per μL or L)

• Erythrocytes -
  
  • Male: 4.5-6.0 x 106 / μL
  • Female: 4.0-5.2 x 106 / μL
• Thrombocytes
  
  • 150.000 - 400.000 per μL
• Leukocytes - 4.000 - 10.000 per μL
• LEUKOGRAM (differential leukocyte count)
  
  • Neutrophils: 60-70 % (band form: 2-5 %) Eosinophils: 3-10 %
  • Basophils: 0-1 %
  • Lymphocytes: 20-40 % Monocytes: 2-10 %

Hematocrit – volume percentage (vol%) of red blood cells (RBC) in blood, measured as part of a blood test.

• Male: 42% - 52%
• Female: 37% - 47%

Question 2

Preparation and evaluation of the blood smear

Answer 2

General

• Fluid CT that circulates in cardiovascular system
  
  • consits of cells and extracellular componets
  • cells are suspended in extracellular fliuf called plasma
  • Within a closed circularoty system
• 5L in male and 4.5 L in women, 7-8% of body weight
• Examination of blood cells required special prepriation and staining
• Function:
  
  • deliver nutrients
  • remove metabolic by products
  • transport and exhcange blood gasses
  • transport hormoned to targeted tissue
  • particiapte in the bodies immune responses
  • participation in coagulation and thermoregulation

Blood cells are studied in smears prepared by spreading of a drop of peripheral blood in a thin layer on the microscopic slide.

Procedure:

1. Disinfection of the skin of the fingertip of the left fourth or third finger (at right-handers)
2. Puncture into the ball of fingertip with sterile lancet or single-use needle
3. The first drop of blood is wiped off because blood is diluted by tissue fluid
4. The second drop of blood is placed near an end of a glass (microscopic) slide and spread using another slide (called “spreader” slide)
5. Spreading: spreader slide is moved over the glass slide at an angle of 45, when slide edge touches the blood drop, the blood spreads by capillary forces along its edge. A thin film of blood is obtained by a smooth quick motion of the spreader slide across a glass slide.
6. The air dried blood smear is fixed and stained.
   * Blood smears are stained with mixtures of acidic (eosin) and basic dyes (methylene blue and its oxidation products – methylene violet and azure)

Meathods

• Staining by Pappenheim´s method:
  
  • acidic (eosin)
  • basic dyes (methylene blue and its oxidation products – methyleneviolet and azure)
• Staining of peripheral blood and bone marrow smears​
  
  • Fixation
    
    • May-Grünwald solution
    • (eosinate of methylene blue in methanol) 3 min
  • Staining
    
    • diluted May-Grünwald solution
    • (the same amount of distilled water was added) 1 – 2 min.
    • Pour off mixture
  • Staining
    
    • Giemsa-Romanowsky solution
    • (eosinate of the methylene azure, blue and violet) 15 min
  • Washing
    
    • distilled water, air-drying
• Results of staining:
  
  • red blood cells – pink/red,
  • nuclei – purple/blue,
  • neutrophilic granules – salmon pink or violet,
  • eosinophilic granules – brick-red,
  • basophilic granules – blue/violet,
  • cytoplasm of lymphocyte – sky blue,
  • cytoplasm of monocyte – pale blue (grayish or greenish),
  • azurophilic granules - purple red

​Evaluation

• light microscope: highmagnification immersion objective (100x) and immersion oil.
• RBC evaluation: size, shape, structure
  
  • Anisocytosis (microcytosis, macrocytosis)
  • Poikilocytosis - variation in RBC shape:
    
    • spherocytes, ovalocytes, sicle cells
    • (Howell-Jolly bodies, Cabott´s rings, basophilic stippling in erythrocyte)
• WBC evaluation: size and morphology
• Leukogram (differential leukocyte count) - proportional incidence (%)
  
  • Neutrophils: 60-70 % (band form: 2-5 %)
  • Eosinophils: 3-10 %
  • Basophils: 0-1 %
  • Lymphocytes: 20-40 %
  • Monocytes: 2-10 %
• Arneth formula -
  
  • determines the percentage of neutrophils with one, two, three, four, and five or more lobes.
  • larger percentage of neutrophils with fewer lobes have a left shift: can be indicative of disease
  • larger percentage of neutrophils with more lobes have a right shift and most commonly have diseases such as vitamin B12 or folate deficiency, chronic uremia, liver disease, etc.

Question 3

Erythrocytes, structure and function

Answer 3

Opening:

• Blood is specialized fluid connective tissue that tavels through the circulatory system
  
  • Function of blood
    
    • Transports oxygen, nutrients, metabolic waste products
    • Regulation of body temperature, signal transmission, acid-base homeostasis, and immune response
• Blood is made up of two main components:
  
  • Blood cells and plasma.
    
    • Plasma:
      
      • Aqueous solution: mostly made up of water but contains some important solutes.
    • Blood cells
    • Classified as either erythrocytes or leukocytes.
      
      • Erythrocytes:
        
        • Red blood cells
      • Leukocytes
        
        • White blood cells,
      • A smaller third cellular constituent are the thrombocytes (platelets).
• Production of blood
  
  • Location:
    
    • Bone marrow
    • The spleen and liver are the primary sites before birth

Red blood cells

Function: Bind oxygen for dilivery to tissues

Shape: anucleate biconcave disc;

Size:

• diameter = 7.5 μm,
• 2.6 μm thick at rim and 0.8 μm in the center (normocyte)

Lifespan:

• survives 120 days
• and then phagocytosed by macrophages in spleen, bone barrow and liver

Nucleus: not pressent

Cytoplasm staining: Eosinophilic (high intensity)

Characteristics

• Only structure is membrane skeleton, contains no organelles or inclusions, only 33% hemoglobin solution
• Cytoskeleton/Organells
  
  • ​​no organells
  • elastic and flexible, structire maintained by membrane protiens
  • defect in genes coding for these cytoskeleton protiens can result in abnomalities in cell shape
• Integral mebrane protiens: in lipid bilayer
  
  • Glycophorins
    
    • transmembrane protiens
    • attachign cytoskeleton protien netweork to cell membrane
  • Band 3 protiens
    
    • bind hemoglobin, and aniton transporter?????
    • extracellular glycosylated domain express specific blood group antigens
• Peripheral membrane protiens
  
  • inner surface
  • account for elastic properties, undergoes continuous rearrangment
  • 2D hexagonal lattice network composed of cytoskeleton protiens
    
    • spectrin: form a lattice bound to underlying actin filaments
    • actin
    • band 4.2 protein
    • adductin
    • band 4.9 protein
    • tropomyosin​
  • Anchored to lipid bilayer with ankyrin which interacts with band 4.2

Hemoglobin= Protien specilized for transport of oxygen anf carbon dioxide

• accounts for the uniform cell acidophilia
• 4 polypeptide globin chains + heme (Fe2+) IORN
  
  • in normochromic RBC 35 ± 2 vol.%, 32 ± 2 pg
• Oxyhemoglobin: Hemoglobin with oxygen
• Carbaminohemoglobin: with CO2.
  
  • Reversibility
• Carboxyhemoglobin (Hb-CO),
  
  • combination of hemoglobin with carbon monoxide CO is irreversible

Inherited alteration of Hb – (HbS) sickle cell disease

Reticulocytes

• running in the vessels and diameter, like an erythrocyte pushed from the bone marrow in to the blood.
• Inside the reticulocytes
  
  • small dots (rest of the DNA).
  • Substantia reticulofiamentosa – the rest of the ribosomal RNA in the cytoplasm
  • Howell – Jolly Bodies and Cabot rings – Rest of DNA in the cytoplasm (nuclear fragments)
• In about 24 hours it turns into a mature erythrocyte – living up to 120 days.

Anisocytosis - microcytes (less than 6 μm) and macrocytes (more than 9 μm) Poikilocytosis (shape abnormalities)
Anemia - decrease in the concentration of hemoglobin in the blood (most of them caused by a reduction in the number of RBCs = erythrocytopenia); caused e.g. by hemorrhage, insufficient production or accelerated destruction of RBCs, insufficient dietary iron, vitamin B 12, folic acid, insufficient secretion of the intrinsic factor in parietal cells of gastric epithelium (pernicious anemia), mutation of gene encoding β-globin chain (sickle cell anemia)

Polycythemia (erythrocytosis) - increased number of RBCs

Question 4

Leukocytes, classification, structure and function, leukogram

Answer 4

Opening:

• Blood is specialized fluid connective tissue that tavels through the circulatory system
  
  • Function of blood
    
    • Transports oxygen, nutrients, metabolic waste products
    • Regulation of body temperature, signal transmission, acid-base homeostasis, and immune response
• Blood is made up of two main components:
  
  • Blood cells and plasma.
    
    • Plasma:
      
      • Aqueous solution: mostly made up of water but contains some important solutes.
    • Blood cells
      
      • Classified as either erythrocytes or leukocytes.
      • Erythrocytes:
        
        • Red blood cells
      • Leukocytes
        
        • White blood cells,
      • A smaller third cellular constituent are the thrombocytes (platelets).
• Production of blood
  
  • Location:
    
    • Bone marrow
    • The spleen and liver are the primary sites before birth
  • EXTRA:
    
    • Hematopoietic stem cells can differentiate into any type of blood cell and give rise to all blood cells through the following two precursor cells:
      
      • Lymphoid precursor cells:
        
        • origin of lymphocytes and natural killer cells
      • Myeloid precursor cells:
        
        • origin of erythrocytes, granulocytes, and megakaryocytes
  • Left shift (or blood shift):
    
    • an increase in immature precursor cells (e.g., increase in band neutrophils with rod-shaped nuclei in response to acute inflammation) in the blood.
    • In most cases, infection is the cause of a left shift.

White cell line - leukocytes

• Leukocytes are classified as either:
  
  • Granulocytes - from the myeloid cell line
  • Agranulocytes - from the lymphoid cell line

******Granulocytes******

• Neutrophils, basophils, and eosinophils
• Cells that have nuclei with multiple lobes.

1- Neutrophils

• Most numerous, 50–65% of all leukocytes in the blood
• Function:
  
  • Migration to sites of inflammation→ identification, destruction, and phagocytosis of extracellular infectious agents (bacteria, fungi)
  • They can be considered the first responders of the (innate) immune system as they are often the first leukocytes to be activated in response to a pathogen
• Size: 10-12 μm in diameter, shpereical
• Lifespan: short-lived cells
• Staining: slightly eosinophilic cytoplasm
• Nucleus: lobed nucleus (chromatin in coarse clumps)~ 3 lobules
• Granules:
  
  • Specific granules: neutrophilic granules
    
    • 0.2 μm
    • salmon like color, not very visable
    • Contain enzymes nessisary for elimination of harmful substances:
      
      • alkaline phosphatase
      • collagenase
      • lactoferrin
      • complement activators
  • Azurophilic granules - lysosomes: ​
    
    • lysozyme defensins
    • myeloperoxidase
    • acid phosphatase and other lysosomal enzymes

2- Eosinophils

• 2-10% of all leukocytes
• Function:
  
  • Immune response against parasites
    
    • parasite cytoxic effect: helmith worms and protozoa
  • Associated with allergic reactions
    
    • Migration to the site of inflammation (chemotaxis) → release of immunoglobulins (IgE)
• Histamine attracts eosinophils to the site of inflammation.
• Limited phagocytic abilities
• General characteristics:
  
  • Size: diameter 12-15 μm
  • Lifespan: 1-2 weeks
  • Staining: high eosinophilic cytoplasm
    
    • Eosinophilic (= acidophile) granules → stained pink/red on H&E stain
  • Nucleus: bilobed nucleus
• Granules:
  
  • Azurophilic granules…
  • Eosinophilic specific granules;
    
    • Crystalline core
      
      • (major basic protein – corresponds for staining with acidic dyes)
      • Which is surrounded by a less dense matrix containing enzymes:
        
        • Acid phosphatase
        • Eosinophil peroxidase
        • Histaminase
        • Arylsulfatase
        • Cathepsins
        • Collagenase

3- Basophils

• 0-1% of all leukocytes
  
  • Function:
    
    • Remain in the bloodstream for minutes before migrating into tissue
    • Production of leukotrienes → inflammation and allergic reaction
    • Release of histamine and heparin
    • Almost no phagocytic abilities
  • Functionally related to mast cells, bind IgE (their plasma membrane possesses Fc receptors) and are capable of generating leucotrienes.
• General characteristics:
  
  • Size: diameter 10 μm
  • Lifespan:
  • Staining: lightly basophillic cytoplasm
  • Nucleus: irregular lobed nucleus, 2 irregular shapes
• Granules:
  
  • Azurophilic granules…
  • Basophilic granules (dark violet beads)
    
    • Containing histamine and heparin often obscure the nucleus
    • Peroxidase
    • Eosinophilic chemotactic factor.

******Agranulocytes (mononuclears)******

• General characteristics:
  
  • Don’t contain specific granules
  • Nucleus is not segmented
  • Retain capacity to undergo cellular division (unlike granulocytes)
  • After entering tissue they can diffrenciate further
  • Contain aurophillic granules (cytoplasm is always basophillic)
• Monocytes and lymphocytes
• Cells that have a single nucleus
• true cells
• participate in immune response
• blood is sued as transport to target tissues
• divided into grounds accroding to shape and presence of granules

1- Monocyte

• Around 3–7% of all leukocytes
• General characterisitcs:
  
  • Diameter: around 5–20 μm (largest leukocytes)
  • Remain in the bloodstream for only around 8 hours before migrating to tissue
  • Nucleus: oval, horseshoe or kidney shaped (eccentrically placed),
  • Slightly basophilic cytoplasm,
  • A lot of fine azurophilic granules
• Function:
  
  • Connects the innate and the acquired immune system
  • Phagocytosis and antigen presentation
    
    • Via MHC-I and MHC-II receptors
  • After migrating into tissue, they differentiate into:
    
    • Macrophages
    • Dendritic cells
    • Osteoclasts
    • Kuffer cells in liver
    • Alveolar macrophages are found in the lung.
    • The red pulp of the spleen contains splenic macrophages.
    • Microglial cells are specialized macrophages found in the nervous system.
    • …

2- Lymphocytes:

• General characteristics:
  
  • Nucleus:
    
    • Round or indented, takes up most of the volume of the cell
      
      • Heterchromatic (reason its dark)
      • In activated from it will be lighter (euchromatin)
  • Cytoplasm:
    
    • Narrow, lightly stained rim around the large nucleus where it does not contain granules.
      
      • Activated contain more azurophilic granules in basophilic cytoplasm
  • Size:
    
    • Small lymphocytes (diameter 6-8 μm);
    • Medium (10-12 μm)
    • And large lymphocytes (up to 30 μm).
• Main cells of the lymphatic or immune system
  
  • Contain three functionally specific types:
  • B cells
    
    • Bone marrow origin
    • Part of the acquired immune system
    • Involved in the production of circulating antibodies
      
      • humoral immunity
  • NK (natural killers)
    
    • Are programmed to kill certain virus-infected cells and some types of tumor cells.
  • T cells
    
    • Involved in cell-mediated immunity
      
      • Long life span, immunocompetency acquired in thymus
    • T- helpers (CD4+ – 70 %) are critical for induction of an immune response; interleukins)
    • T-supressors (regulatory) - supress the immune response
    • T-cytotoxic (killers) - lysis of the infected or neoplastic cells (lymphokines, perforins)

Leukogram (plural leukograms)

• A tabulation of the type and quantity of leukocytes present in a blood sample.

NEED TO KNOW FUCKING VALULES BAHHHHHHH

EXTRA:

B cell:

• Part of the acquired immune system
• Important surface marker: CD20
• The surface of B lymphocytes contains B-cell receptors that are highly specific to certain antigens.
• Function
  
  • If a naive B-cell receptor is presented with an antigen, the B cell is activated and migrates to the germinal center of a lymph node or the spleen.
    
    • Further development
      
      • Plasma cell: secretes monoclonal immunoglobulins, predominately IgM, but also IgA, IgE, IgG, that target a specific antigen
      • Memory B cell: persists in secondary lymphoid organs
        
        • Reactivation by second exposure to same antigen → develops into plasma cell → secretes predominantly IgG or IgA
  • Activation is triggered.
    
    • T-cell dependent (main mechanism) by antigen presentation via MCH-II
    • T-cell independent (rare; e.g., triggered by polysaccharides)

T-lymphocytes (T cells)

• Part of the acquired immune system
• T-cell receptor: a complex of proteins of the immunoglobulin superfamily, which binds antigen bound to major histocompatibility complexes on other cells
  
  • Each cell expresses a T-cell receptor variant that binds one specific antigen
  • T-cell activation requires both antigen binding and interaction between co-receptors (CD4 and CD8) and MHC receptors.
• Cytotoxic T cells (T-killer cells)
  
  • CD8 positive
  • Recognize foreign (mostly viral) antigens presented via MHC-I and, depending on the scenario, trigger apoptosis or cell lysis of the presenting cell
• T-helper cells
  
  • They require antigen presenting cells equipped with MHC-II receptors → recognize presented antigens → cytokine release
  • CD4 positive
  • Functions:
    
    • Initiate the cellular immune response → macrophage stimulation
    • Initiate humoral immune response in cooperation with B lymphocytes → immunoglobulin production
    • Tissue inflammation, both pro- and anti-inflammatory
• Regulatory T cells (Tregs, suppressor T cells)
  
  • CD4 positive
  • Limit and protect against excessive immune response
• Memory T cells
  
  • CD4 & CD8 positive
  • Conservation/memory of a specific acquired immune response

Question 5

Platelets- differentiation, structure and function

​

Answer 5

Opening:

• Blood is specialized fluid connective tissue that tavels through the circulatory system
  
  • Function of blood
    
    • Transports oxygen, nutrients, metabolic waste products
    • Regulation of body temperature, signal transmission, acid-base homeostasis, and immune response
  • Blood is made up of two main components:
    
    • Blood cells and plasma.
      
      • Plasma:
        
        • Aqueous solution: mostly made up of water but contains some important solutes.
      • Blood cells
        
        • Classified as either erythrocytes or leukocytes.
        • Erythrocytes:
          
          • Red blood cells
        • Leukocytes
          
          • White blood cells,
        • A smaller third cellular constituent are the thrombocytes (platelets).
• Production of blood
  
  • Location:
    
    • Bone marrow
    • The spleen and liver are the primary sites before birth

Thrombocytes

• Thrombocytes= platelets
• General:
  
  • Are small, formed elements found throughout the blood.
    
    • Because they do not contain a nucleus or organelles, they are not considered to be true cells.
    • Cell fragments
      
      • Derived from megakaryocytes, polyploid cells found in bone marrow.
  • 2-4 micrometers in diameter
    
    • Significantly smaller than any other cellular structures in blood
  • Function:
    
    • platelets are essential for forming clots in response to tears in blood vessels.
• Platelet Production
  
  • Location: bone marrow
  • Duration:
    
    • Production and maturation of platelets takes about 1 week.
  • Regulation:
    
    • Thrombopoietin (secreted by the liver and kidneys)
    • Stimulates megakaryocyte proliferation and maturation in the bone marrow.
  • Stages of thrombopoiesis:
    
    • myeloid precursor cell →
    • megakaryoblasts →
    • megakaryocytes →
    • platelets

Structure:

• Peripheral zone:
  
  • Cell membrane covered with thick glycocalyx coat
  • Integral membrane protiens: act as receprots
• Structural zone:
  
  • Microtubules, actin, mysoin, actin binding protiens- form a a network supporting plasma membrane
  • Circumferly arranged
• Organelle zone
  
  • Organelles and 3 types of granules
  • Alpha granules
    
    • Largest
    • Role in inital phase of vessel repair, blood coagulation and platelet aggregation
    • Platelet factor 4, transforming growth factor-beta1, platelet-derived-growth factor, fibronectin, von Willebrand factor, beta-tromboglobulin, fibrinogen, and coagulation factors V and XIII)
  • Delta granules
    
    • Facilliate platlet adhesion and vasoconstiction of injured vessel
    • Nessisary for removal of blood clot in later stages
    • ​ADP or ATP, Ca2+, serotonin, hitamine
  • Lambda granules
    
    • Dense granueles
    • Similar to lysosomes (several hydrolytic enzymes).
• Membrane zone
  
  • Open canalicular system
    
    • open canaliculi are invaginations into cytoplasm
  • Dense tubular system
    
    • electron dense material originating from RER of megakryocyte- storage site for calcium ions
    • dont connect with the surface of platlet

Activated platelets excrete the contents of these granules into their canalicular systems and into surrounding blood.

• Granulomere: central dark luminous area with purple grains
• Hylomere: pheripheral light homogenous basophillic area

EXTRA_______________________

Blood clot formation

• Blood clots are formed in response to injury/trauma of a blood vessel.
• The four basic steps to coagulation are:
  
  • Platelets are activated by the exposed collagen
  • Platelet factors are released
  • More platelets are attracted by the platelet factors
  • Platelets come together to form a plug
• In more detail:
  
  • A tear in a blood vessel exposes collagen.
  • Platelets bind to the exposed collagen through membrane proteins called integrins.
    
    • This binding activates the platelets and they release serotonin, ADP, and platelets-activating factor.
    • More platelets are recruited to the site of injury by the platelets-activating factor.
  • Platelets-activating factor simultaneously activates pathways to convert phospholipids in the membranes: thromboxane A2.
    
    • Thromboxane A2 and serotonin act as vasoconstrictors and contribute to platelet accumulation.
    • Ultimately, the recruited platelets form a platelet plug that will be converted to a clot through the coagulation cascade.
  • The coagulation cascade is a series of reactions that results in the conversion of fibrinogen to fibrin and the formation of a cross-linked fibrin mesh that traps erythrocytes.

Question 6

Hematopoiesis, periods, stem cells, growth factors, structure of the bone marrow

NOT FINISHED!!!!

Answer 6

Opening:

• Blood is specialized fluid connective tissue that tavels through the circulatory system
  
  • Function of blood
    
    • Transports oxygen, nutrients, metabolic waste products
    • Regulation of body temperature, signal transmission, acid-base homeostasis, and immune response
• Blood is made up of two main components:
  
  • Blood cells and plasma.
    
    • Plasma:
      
      • Aqueous solution: mostly made up of water but contains some important solutes.
    • Blood cells
    • Classified as either erythrocytes or leukocytes.
      
      • Erythrocytes:
        
        • Red blood cells
      • Leukocytes
        
        • White blood cells,
      • A smaller third cellular constituent are the thrombocytes (platelets).
• Production of blood
  
  • Location:
    
    • Bone marrow
    • The spleen and liver are the primary sites before birth
• EXTRA: Hematopoietic stem cells can differentiate into any type of blood cell and give rise to all blood cells through the following two precursor cells:Lymphoid precursor cells:
• origin of lymphocytes and natural killer cells
• Myeloid precursor cells:
• origin of erythrocytes, granulocytes, and megakaryocytes

Periods of Hemopoiesis: Prenatal Hemopoiesis

• Mesoblastic Period, “Yolk sac phase”
  
  • Peek of period in 2 month of developmentm then quickly dissapears
  • In the wall of the yolk sac, later in the body stalk
  • Foundation:
    
    • Form from undiffrentiated mesenchyme of yold sac and partially from the mesenchyme of the chorion and allantoids
  • Mesenchymal cells form clusters and blood islets →
    
    • Cells on surface diffrentiate into angioblasts and form endothelium of primative blood vessels
    • Central cells: (hemoblasts), erythroblasts
      
      • Which move in the primative blood circulation
• Hepatolienal period
  
  • 2-9 month of development
  • Hemopoietic centers appear in the liver
    
    • Is the first intra-embryonic site of haematopoiesis.
  • The liver is the major blood-forming organ in the fetus during the second trimester
    
    • Spleen also helping to a lesser extent
• Medullary Period“Bone marrow phase”
  
  • From the 4th month
  • Red bone marrow beggins to develop
• Structure: hematopoietic cords, sinusoidal capillaries, stroma (reticular connective tissue), macrophages, adipocytes

Monophyletic theory:

• Blood cells are derived from a common stem cell HSC
  
  • Hematopoietic stem cells
    
    • multipotent, self renewal, diffrentiation
  • Gives rise to multiple colonies of progenitor stem cells
    
    • Myeloid proginator cells
    • Lymphoid proginator cells
• Surface receptors of progenitor cells:
  
  • Bind specific cytokines and growth factors
    
    • Example: colony- stimulating factors (CSFc)
  • Those factors influence cell proliferation and maturation into a specific lineage

Hematopoietic stem cells

• Myeloid proginator cells
  
  • Erythrocyte: red linage
  • White linage:
    
    • Granulocyte proginator
    • Monocyte proginator
  • Megakaryocyte/thrombocyte linage
• Lymphoid linage

1- Erythropoiesis

• CMP (common myeloid progenitor)
• Erythropoietin: IL-3, IL-4— to MEP (megakaryocyte- erythrocyte progenitor)
• Transforms into erythropoietin-sensitive progenitor giving rise to the proerythroblast.
  
  • around 20 μm, large spherical nucleus, nucleoli,basophilic cytoplasm
• Basophillic erythoblast: arrises from mitotic division, synthisise hemoglobin (high bassophillia)
  
  • 10-16 μm, spherical nucleus, nucleoli not visible, basophilic cytoplasm
• Polychromatophillic erythroblast
  
  • accumilation of hemoglobin gradually changes the staining of the cell, prsends both acidophillia snd basophillia
    
    • around 10-12 μm, smaller nucleus –condensed chromatin (clock face), baso- and eosinophilia in the cytoplasm
• Orthochromatiphilic erythroblast
  
  • increased acidophillic cytoplasm and dense nucleus
  • increasing hemogobin, cytoplasm eosiniphillic
  • at this stage cell is no longer capable of division
• Reticulocyte
  
  • losses nucelus- then ready to pass into vlood sinusoids of bone marrow
• Erythrocyte

The life span od erythrocyte is cca 120 days, then they are degraded by macrophages of spleen, bone marrow and liver.

2- Granulopoiesis

• CMP (common myeloid progenitor) →
  
  • Myeloblast is first recognizable cell of granulopoiesis; its mitotic phase stops at late myelocyte stage, then it differentiate into mature forms.
• GMPs- granulocyte/monocyte progenitor (GM-CSF, G-CSF, IL-3) →
• monopotent progenitors →
• precursors
  
  • neutrophil: 6 changes
  • eosinophil
• myeloblast
• promyleocyte
  
  • produce ezurophillic granules
• myleocyte
  
  • begin with spherical nucelus and become increasinglly heterochormatic- specific granule formation
• metamyleocyte
  
  • stage to identify diffrences between cells due to specific granules
• band cell
  
  • elongated nueclus, horseshoe apperance
  • eary formation of lobes
• mature neutrophill
  
  • finished lobe formation

3. Thrombopoiesis

• Megakaryocyte proginator cell
  
  • its formation starts as unipotent megakaryocyte progenitor MKP(CFU-Meg),
  • which proliferates to precursor cell-megakaryoblast.
• It differentiates in megakaryocyte (successive endomitoses – thrombopoietin).

megakaryoblast

15 - 20μm

megakaryocyte

50 - 150 μm, polyploidy of nucleus, 64 n

Regulatory mechanisms of hematopoiesis

initiate the formation of new blood cells, regulate the number of newly formed elements, control the formation of blood cells by the induction or blockage of cell maturation and apoptosis

Regulatory factors are circulating in blood, acting in low concentrations as hormons, are bound to specific receptors of the surface of target cells (progenitor cells, erythrocytes, granulocytes, lymphocytes, macrophages, megakaryocytes, …).

e.g.

Colony stimulating factors (e.g. GM-CSF, G-CSF) produced by T cell, endothelial cells, monocytes, macrophages
Erythropoietin - kidney, liver
Thrombopoietin - bone marrow

Interleukins - endothelial cells, CD4+T cells, neutrophils, macrophages

Megakaryocyte – about 100 µm, lobed nucleus, azurophilic granulesin the cytoplasm