blood & its functions
DESCRIPTION
Blood & its functionsTRANSCRIPT
The average human has 5 litres of blood(Average Blood Volume is 4 to 6 liters).
It is a transporting fluid It carries vital substances to all parts of the
body Blood is the only fluid tissue. Blood is a complex connective tissue in which
living cells, the formed elements, are suspended in the nonliving fluid called plasma.
Composition of BloodFormed Elements : Erythrocytes, Leukocytes , Platelets &
Plasma.
BloodBlood
Blood composition55% Plasma (fluid matrix of water, salts, proteins, etc.)45% Cellular elements: Red Blood Cells (RBCs): 5-6 million RBCs/ml of blood.
Contain hemoglobin which transport oxygen and CO2.
White Blood Cells (WBCs): 5,000-10,000 WBCs/ml of blood. Play an essential role in immunity and defense. Include:
Lymphocytes: T cells and B cells Macrophages: (phagocytes) Granulocytes: Neutrophils, basophils, and eosinophils.
Platelets: Cellular fragments, 250,000- 400,000/ml of blood. Important in blood clotting.
HUMAN BLOOD SMEARHUMAN BLOOD SMEAR
Physical Characteristics and Volume
Sticky and metallic tasting…Color: Scarlet = O2 rich; Dull red = O2 poor
Heavier than H2O; 5X thicker
pH = 7.35 - 7.45Temp = 38ºC or 100.4ºF (higher than normal)8% body weight; 5 - 6 liters
Centrifuged blood
45% Red blood cells (erythrocytes)Hematocrit: RBC volume = ~45%
(leukocytes)<1% Buffy Coat: White blood cells
55% Plasma: Serum and fibrinogen
plasma (55%)
red blood cells(5-6-million /ml)
white blood cells(5000/ml)
platelets
PlasmaStraw-colored liquid.Consists of H20 and dissolved solutes.Ions, metabolites, hormones, antibodies.Na+ is the major solute of the plasma.liquid part of blood
Plasma transportssoluble food moleculeswaste productshormones antibodies
90% of plasma is water: >100 other substances in plasma: salts
(electrolytes), nutrients, gases, hormones, plasma proteins, various wastes and products of cell metabolism.
Plasma proteins: Constitute 7-9% of plasma. Provide the colloid osmotic pressure needed to draw H20 from
interstitial fluid to capillaries. Maintain blood pressure. Albumin:. Maintains osmotic pressure of blood. Clotting proteins Antibodies
Constitute 7-9% of plasma Three types of plasma proteins: albumins, globulins, &
fibrinogen Albumin accounts for 60-80, plasma protein made by
the liver, Creates colloid osmotic pressure that draws H20 from interstitial fluid into capillaries to maintain blood volume & pressure
Globulins carry lipids globulin: Transport lipids and fat soluble vitamins. globulin: Transport lipids and fat soluble vitamins. globulin: Antibodies that function in immunity.
Gamma globulins are antibodies Fibrinogen Constitutes 4% of plasma proteins. Important clotting
factor. Converted into fibrin during the clotting process. Serum is fluid left when blood clots
Composition of plasma is kept relatively constant: Liver replenishes blood proteins… Respiratory system and kidneys maintain pH
(acidosis = too acid; alkalosis = too basic)
Plasma helps maintain body heat.
Erythrocytes or RBCs Anucleate - they lack a nucleus Filled with hemoglobin which carries oxygen Biconcave discs = greater surface area for
gas exchange. 5X106 cells/mm3 of Half-life ~ 120 days. Contain 280 million hemoglobin with 4 heme chains
(contain iron).
RED BLOOD CELLS SPECIALISATIONSRED BLOOD CELLS SPECIALISATIONS
2) no nucleus extra space inside
3) contain haemoglobin
the oxygen carrying molecule
250million molecules / cell
1) biconcave shape
increases the surface area so more oxygen can be carried
Are erythrocytes (RBCs) & leukocytes (WBCs)
RBCs are flattened biconcave discs Shape provides increased
surface area for diffusion Lack nuclei & mitochondria Each RBC contains 280
million hemoglobins
HAEMOGLOBINHAEMOGLOBIN
gives red blood cells gives red blood cells their colour their colour
can carry up to 4 can carry up to 4 molecules of Omolecules of O22
associates and associates and dissociates with Odissociates with O22
contains ironcontains iron
Red blood cells (RBCs)
transport oxygen specialised to do this Also carry some CO2
Erythrocytes or RBCsWhile number of RBCs in the blood is
important….hemoglobin is the key.The more hemoglobin molecules the
RBCs contain, the more oxygen they can carry.
1RBC - 250 million molecules of hemoglobin, each binding 4 molecules of oxygen.
When there is a high concentration of oxygen e.g in the alveoli haemoglobin combines with oxygen to form oxyhaemoglobin. When the blood reaches the tissue which have a low concentration of oxygen the haemoglobin dissociates with the oxygen and the oxygen is released into body tissues
FUNCTION OF HAEMOGLOBINFUNCTION OF HAEMOGLOBIN
Anemia results from: Lower # RBCs Deficient hemoglobin
Hemorrhagic anemia: sudden hemorrhage Hemolytic anemia: lysis of RBCs from bact.
infection Pernicious anemia: lack of B12 Aplastic anemia: depression/destruction of
bone marrow by cancer, radiation, meds.
Sickle Cell Anemia: Deficient hemoglobin - a point mutation
changes a single amino acid.
Polycythemia - abnormal increase in erythrocytes, caused by: Bone marrow cancer High altitudes
Thickens and slows blood, impairs circulation
Complete cells (nuclei, mitochondria and organelles) Move in amoeboid fashion. Can squeeze (leave the blood vessels
through) capillary walls (diapedesis), respond to chemicals Almost invisible, so named after stains. Neutrophils are the most abundant WBC, accounts for 50 – 70% of
WBCs. Involved in immune function. Crucial for defense. Positive chemotaxis: they respond to chemical signals and move toward
damage or threats. Body increases amount in response to infection Leukocytosis: more than 11,000 cells/mm3 indicates
infection Leukopenia: abnormally low, usually due to
corticosteroids and chemotherapy.
White blood cells
the bodies “defence” part of the immune
system much larger than RBCs far fewer have a nucleus 4000-13000 per mm3
2 types: phagocytes and lymphocytes
Have nucleus, mitochondria, & amoeboid ability Can squeeze through capillary walls
(diapedesis) Granular leukocytes help detoxify foreign
substances & release heparin Include eosinophils, basophils, & neutrophils
Agranular leukocytes are phagocytic & produce antibodies
Include lymphocytes & monocytes
Granulocytes Granules in their cytoplasm can be stained Include neutrophils, eosinophils, and basophils
Agranulocytes Lack visible cytoplasmic granules Include lymphocytes and monocytes
Neutrophils Multi-lobed nucleus with fine granules Act as phagocytes at active sites of infection
Eosinophils Large brick-red cytoplasmic granules Found in response to allergies and parasitic worms
Basophils Have histamine-containing granules Initiate inflammation
Lymphocytes Nucleus fills most of the cell Play an important role in the immune
response Monocytes
Largest of the white blood cells Function as macrophages Important in fighting chronic infection
Provide a specific immune response toinfectious diseases.There are 2 types: -
- T-cells & B-cellsThey produce antibodies.
MONOCYTESMONOCYTES
Also called thrombocytes. Derived from ruptured multinucleate cells
(megakaryocytes) Smallest of formed elements.
Are fragments of megakaryocytes. Lack nuclei.
Normal platelet count = 300,000/mm3
Survive 5-9 days Have amoeboid movement. Important in blood clotting: Constitute most of the mass of the clot.
Release serotonin to reduce blood flow to area. Secrete growth factors
Maintain the integrity of blood vessel wall.
PHAGOCYTESPHAGOCYTES
Monocytes and macrophages
Provide a non-specific response to infection
HEMATOPOIESISHEMATOPOIESIS
Is formation of blood cells from stem cells in marrow (myeloid tissue) & lymphoid tissue
Erythropoiesis is formation of RBCs Stimulated by erythropoietin (EPO) from
kidney Leukopoiesis is formation of WBCs
Stimulated by variety of cytokines= autocrine regulators secreted by immune
system
Formation of blood cells2 types of hematopoiesis:Erythropoiesis:
Formation of RBCs.Leukopoiesis:
Formation of WBCs.Occurs in myeloid tissue (bone marrow of long bones) and lymphoid tissue.Stem cells differentiate into blood cells.
Active process. 2.5 million RBCs are produced every second. Regulated by erythropoietin.
Erythropoietin binds to membrane receptors, stimulating cell division.
Old cells are destroyed in spleen and liver. Iron recycled back to myeloid tissue to be
reused in RBC synthesis. Need iron, vitamin B12 and folic acid for
synthesis.
Cytokines stimulate different types and stages of WBCs production
Multi potent growth factor-1 , interleukin-1 , and interleukin-3:
Stimulate development of different types of WBC cells.
Granulocyte-colony stimulating factor: Stimulates development of neutrophils.
Granulocyte-monocyte colony stimulating factor: Simulates development of monocytes and
eosinophil's.
2.5 million RBCs are produced/sec
Lifespan of 120 days
Old RBCs removed from blood by phagocytic cells in liver, spleen, & bone marrow Iron recycled back
into hemoglobin production
Types of Blood VesselsArteries and Arterioles
Carry blood away from heart to body. Have high pressure.Have thick muscular walls, which make them elastic and contractile.
Vasoconstriction: Arteries contract: Reducing flow of blood into capillaries. Increasing blood pressure.
Vasodilation: Arteries relax: Increasing blood flow into capillaries. Decreasing blood pressure.
Capillaries Only blood vessels whose walls are thin enough to
permit gas exchange. Blood flows through capillaries relatively slowly,
allowing sufficient time for diffusion or active transport of substances across walls.
Only about 5 to 10% of capillaries have blood flowing through them. Only a few organs (brain and heart) always carry full load of blood.
Blood flow to different organs is controlled by pre capillary sphincters of smooth muscle.
Veins and Venules
Collect blood from all tissues and organs and carry it back towards heart.
Have low pressure and thin walls.
Veins have small valves that prevent backflow of blood towards capillaries, especially when standing. If the valves cease to work properly, may result in:
Varicose veins: Distended veins in thighs and legs.
Hemorrhoids: Distended veins and inflammation of the rectal and anal areas.
Lymphatic and Immune System
Components: Lymph, lymphatic vessels, bone marrow, thymus, spleen, and lymph nodes.Functions:
Defends against infection: bacteria, fungi, viruses, etc.
Destruction of cancer and foreign cells. Synthesis of antibodies and other immune
molecules. Synthesis of white blood cells.
Homeostatic Role: Returns fluid and proteins that have leaked from
blood capillaries into tissues. Up to 4 liters of fluid every day. Fluid returned near heart/venae cavae.
RBC Antigens & Blood Typing
The most well known and medically important blood types are in the ABO group. They were discovered in 1900 and 1901 at the University of Vienna by Karl Landsteiner in the process of trying to learn why blood transfusions sometimes cause death and at other times save a patient. In 1930, he belatedly received the Nobel Prize for this discovery.
All humans and many other primates can be typed for the ABO blood group. There are four principal types: A, B, AB, and O. There are two antigens and two antibodies that are mostly responsible for the ABO types. The specific combination of these four components determines an individual's type in most cases.
ABOBlood Type
Antigen A
Antigen B
Antibody anti-A
Antibody Anti-B
A yes no no yes
B no yes yes no
O no no yes yes
AB yes yes no no
People with type A blood will have the A antigen on the surface of their red cells . As a result, anti-A antibodies will not be produced by them because they would cause the destruction of their own blood. However, if B type blood is injected into their systems, anti-B antibodies in their plasma will recognize it as alien and burst or agglutinate the introduced red cells in order to cleanse the blood of alien protein.
Individuals with type O blood do not produce ABO antigens. Therefore, their blood normally will not be rejected when it is given to others with different ABO types. As a result, type O people are universal donors for transfusions, but they can receive only type O blood themselves. Those who have type AB blood do not make any ABO antibodies. Their blood does not discriminate against any other ABO type. Consequently, they are universal receivers for transfusions, but their blood will be agglutinated when given to people with every other type because they produce both kinds of antigens.
It is easy and inexpensive to determine an individual's ABO type from a few drops of blood. A serum containing anti-A antibodies is mixed with some of the blood. Another serum with anti-B antibodies is mixed with the remaining sample. Whether or not agglutination occurs in either sample indicates the ABO type. It is a simple process of elimination of the possibilities. For instance, if an individual's blood sample is agglutinated by the anti-A antibody, but not the anti-B antibody, it means that the A antigen is present but not the B antigen. Therefore, the blood type is A.
ABO system: Major group of antigens of RBCs.
Type A: Only A antigens present.
Type B: Only B antigens present.
Type AB: Both A and B antigens present.
Type O: Neither A or B antigens
present.
Each person inherits 2 genes that control the production of ABO groups.
Type A: May have inherited A gene from each
parent. May have inherited A gene from 1 parent
and O gene from the other.
Type B: May have inherited B gene from each
parent. May have inherited B gene from 1 parent
and O gene from the other parent. Type AB:
Inherited the A gene from one parent and the B gene from the other parent.
Type O: Inherited O gene from each parent.
People with blood group 0 Rh - are called "universal donors" and people with blood group AB Rh+ are called "universal receivers."
Rh+ blood can never be given to someone with Rh - blood, but the other way around works. For example, 0 Rh+ blood can not be given to someone with the blood type AB Rh -.
People with Type A blood make antibodies to Type B RBCs, but not to Type A
Type B blood has antibodies to Type A RBCs but not to Type B
Type AB blood doesn’t have antibodies to A or B
Type O has antibodies to both Type A & B
If different blood types are mixed, antibodies will cause mixture to agglutinate
If blood types do not match, the recipient’s antibodies attach to donor’s RBCs and agglutinate.
Type O Universal donor. Recipient’s antibodies cannot agglutinate
the donor’s RBCs. Type AB Universal recipient
Lack the anti-A and anti-B antibodies. Cannot agglutinate donor’s RBCs.
Another group of antigens found on RBCs. Rh positive:
Have these antigens. Rh negative:
Do not have these antigens. Significant when Rh negative mother give
birth to Rh positive baby. At birth, mother may become exposed to Rh
positive blood of fetus. Mother at subsequent pregnancies may
produce antibodies against the Rh factor.
If blood types don't match, recipient’s antibodies agglutinate donor’s RBCs
Type O is “universal donor” because lacks A & B antigens Recipient’s antibodies
won’t agglutinate donor’s Type O RBCs
Type AB is “universal recipient” because doesn’t make anti-A or anti-B antibodies Won’t agglutinate donor’s
RBCs
Insert fig. 13.6
Is cessation of bleeding Promoted by reactions initiated by vessel
injury Breakage of endothelial lining exposes collagen
proteins causing: Vasoconstriction. Platelet plug. Web of fibrin.
Platelets don't stick to intact endothelium because of presence of prostacyclin (PGI2--a prostaglandin) & NO Keep clots from forming & are vasodilators
Damage to endothelium allows platelets to bind to exposed collagen von Willebrand factor increases bond by binding to
both collagen & platelets Platelets stick to collagen & release ADP,
serotonin, & thromboxane A2 = platelet release reaction
Serotonin & thromboxane A2 stimulate vasoconstriction, reducing blood flow to wound
ADP & thromboxane A2 cause other platelets to become sticky & attach & undergo platelet release reaction This continues until platelet plug is formed
Platelets normally repelled away from endothelial lining by prostacyclin (prostaglandin).
Do not want to clot normal vessels.
Exposes sub endothelial tissue to blood. Platelet release reaction:
Endothelial cells secrete von Willebrand factor to cause platelets to adhere to collagen.
Platelet secretory granules release ADP, serotonin and thromboxane A2.
Serotonin and thromboxane A2 stimulate vasoconstriction.
ADP and thromboxane A2 make other platelets “sticky”.
Platelets adhere to collagen. Produce platelet plug. Strengthened by activation of plasma
clotting factors.
Platelet plug strengthened by fibrin. Clot reaction:
Contraction of the platelet mass forms a more compact plug.
Conversion of fibrinogen to fibrin occurs. Fluid squeezed from the clot is called
serum (plasma without fibrin).
Intrinsic Pathway Initiated by exposure of blood to a
negatively charged surface (collagen). This activates Factor XII (protease), which
activates other clotting factors. Ca++ and phospholipids convert prothrombin
to thrombin. Thrombin converts fibrinogen to fibrin. Produces meshwork of insoluble fibrin
polymers.
Thromboplastin is not a part of the blood, so called extrinsic pathway.
Damaged tissue release a thromboplastin.
Thromboplastin initiates a short cut to formation of fibrin.
Activated factor XII converts an inactive molecule into the active form (kallikrein).
Kallikrein converts plasminogen to plasmin.
Plasmin is an enzyme that digests the fibrin.
Clot dissolution occurs.
When damage is repaired, activated factor XII causes activation of kallikrein Kallikrein converts plasminogen to plasmin
Plasmin digests fibrin, dissolving clot
Clotting can be prevented by Ca+2 chelators (e.g. sodium citrate or EDTA) or heparin which activates antithrombin
III (blocks thrombin) Coumarin blocks clotting by
inhibiting activation of Vit K Vit K works indirectly by reducing Ca+2
availability