Chapter 19: Blood
Hematocrit
- % of blood sample that consists of formed elements (most of which are red blood cells (RBCs)) - Normal hematocrit or packed cell volume (PCV) in adult males is 46 & in adult females is 42 - Sex differences in hematocrit primarily reflects that androgens (male hormones) stimulate RBC production , whereas estrogens (female hormones) do not
Globulins
- 2nd most abundant proteins in plasma (account for about 35%) - E.g. antibodies (immunoglobulins) that aid body defence & transport globulins
Fibrinogen
- 3rd major type of plasma protein (accounts for about 4%), functions in clotting. - Is a soluble protein until clotting occurs & it is then converted into the insoluble protein fibrin - This conversion removes clotting proteins, leaving behind a fluid known as serum
Blood
- A specialized fluid connective tissue (of the cardiovascular system) that contains cells suspended in a fluid matrix.
Blood volume in males & females
- Adult males typically have more blood than do adult females (reflects difference in average body size) - E.g. males = 5-6 liters, vs females = 4-5 liters - Can estimate blood volume in litres for a person of either sex by calculating 7% of body weight in kg
White blood cell (WBC) functional characteristic: All are capable of amoeboid movement
- Amoeboid movement is gliding motion made possible by flow of cytoplasm into slender cellular processes extended in the direction of movement - Mechanism isn't fully understood, but involves continuous rearrangement of bonds between actin filaments in cytoskeleton, & also requires calcium ions & ATP - This mobility allows WBCs to move through the endothelial lining into peripheral tissues
Agglutinins
- Antibodies contained in the plasma, that will attack the antigens on foreign RBCs. - When these antibodies attack, the foreign cells agglutinate or clump together
Importance of iron and health problems that relate to it
- Any impairment to iron intake or metabolism can cause serious clinical problems, because RBC formation will be affected - E.g. iron-deficiency anemia results from lack of iron in diet or from problems with iron absorption - Too much iron can also cause problems, due to excessive build up in secondary storage sites e.g. liver & cardiac muscle tissues - Excessive iron deposition in cardiac muscle cells has been linked to heart disease
White blood cells AKA leukocytes
- Are less numerous than RBCs (as account for < 0.1 % of formed elements) - Participate in the body's defense mechanisms - There are 5 classes, each with slightly different functions
Platelets
- Are small, membrane-bound cell fragments that contain enzymes & other substances important to the process of clotting. - Account for < 0.1 % of formed elements
Antigens
- Are substances that can trigger a protective defence mechanism which is the immune response - Most are proteins, but some are other types of organic molecules - Plasma membranes contain surface antigens that the immune system recognises as "normal" / "self", so doesn't attack them (unlike foreign antigens)
ABO blood group
- Based on presence or absence of A & B surface antigens - According to this group, there are 4 blood types: (1) Type A blood has RBCs with surface antigen A only, (2) type B has surface antigens B only, (3) type AB has both A & B, & (4) type O has neither A or B antigens - Individuals with these blood types aren't evenly distributed throughout the world (differs by ethic group & by region)
Rh blood group
- Based on the presence or absence of the Rh surface antigen - Rh positive (Rh+) indicates presence of Rh surface antigen, commonly called the Rh factor - Absence of this antigen is indicated by Rh negative (Rh-) - When complete blood type is recorded, the term Rh is usually omitted, & positive or negative sign is used e.g. type O+ (which is most common blood type) - Rh type differs by ethic group & by region
Transport globulins
- Bind small ions, hormones, & compounds that might otherwise be removed by kidneys or that have very low water solubility. - Include hormone-binding proteins, metalloproteins, apolipoproteins, & steroid-binding proteins
Function of blood: Stabalizing body temperature
- Blood absorbs heat generated by active skeletal muscles & redistributes it to other tissues (or organs) - If body temp already high then heat will be lost across the skin surface - If body temp too low, warm blood is directed to brain & to other temperature-sensitive organs
Function of blood: Restricting fluid loss at injury sites
- Blood contains enzymes & other substances that responds to breaks in vessel walls by initiating clotting - Blood clot acts as a temporary patch that prevents further blood loss
Function of blood: Defending agains toxins & pathogens
- Blood transports white blood cells (specialized) that migrate into other tissues to fight infections or remove debris - Blood also delivers antibodies, proteins that specifically attack invading pathogens
Apolipoproteins
- Carry triglycerides & other lipids in the blood. - When bound to lipids, an apolipoprotein becomes a lipoprotein
Blood type
- Classification determined by the presence or absence of specific surface antigens in RBC plasma membranes.
Fetal hemoglobin (Hg)
- Contained in RBCs of embryo or fetus - Binds oxygen more readily than adult hemoglobin - Thus developing fetus can "steal" oxygen from maternal blood stream at the placenta - Conversion to adult form begins shortly before birth & continues over the next year - Drugs (e.g. butyrate) that stimulate the production of fetal Hg can be used to treat sickle cell disease
Reasons for cross-match testing
- Cross-reactions can occur, even to type O- blood, because at least 48 other surface antigens are present - Thus, whenever time & facilities permit, further testing is performed to ensure complete compatibility between donor blood & recipient blood
Stages of red blood cell (RBC) maturation in red bone marrow via erythropoiesis
- Day 1: Cells destined to become RBCs first differentiate into proerythroblasts - Day 2-3: Proceed through various erythroblast stages (day 2 = basophilic, day 3 = polychromatophilic), which actively make hemoglobin (Hb) & are named based on total size, Hb amount, & size & appearance of nucleus - Day 4: Erythroblast now called a normoblast, sheds its nucleus - Day 5-7: Due to nucleus loss becomes a reticulocyte, (contains 80% of Hb of a mature RBC) & Hb production continues - When reticulocyte enters blood stream & has day of circulation it becomes a mature RBC
Surface antigens on RBCs
- Determine blood type - Integral membrane glycoproteins whose characteristics are genetically determined - RBCs have at least 50 kinds, but the 3 surface antigens A, B, & Rh (or D) are of particular importance
Hematocrit process
- Determined by spinning blood sample in a centrifuge so that all formed elements come out of suspension - Whole blood contains about 1000 RBCs for each white blood cell - After centrifugation, the white blood cells & platelets form a very thin buffy coat above a thick layer of RBCs
Function of blood: regulating pH & ion composition of interstitial fluids
- Diffusion between interstitial fluids & blood eliminates local deficiencies or excesses of ions e.g. calcium or potassium - Blood also absorbs & neutralises acids (e.g. lactic acid, generated by active skeletal muscles)
Staining processes to distinguish types of white blood cells (WBCs)
- Distinguished microscopically in a blood smear by using either of two standard stains: (1) Wright's stain, or (2) Giemsa stain - Traditionally WBCs divided into two groups based on appearance after staining: (1) granular leukocytes / granulocytes (abundance of stained granules) - the neutrophils, eosinophils, & basophils, & (2) agranular leukocytes / agranulocytes (with few stained granules) - the monocytes & lymphocytes
Regulation of erythropoiesis by hormone erythropoietin (EPO)
- EPO, is glycoprotein formed by kidneys & liver - EPO released by the kidneys in response to hypoxia (low oxygen concentration / levels in tissues) - EPO is released (1) during anemia; (2) when blood flow to kidney declines; (3) when oxygen content of air in lungs declines, due to disease or high altitude; & (4) when respiratory surfaces of lungs are damaged - Once in bloodstream, EPO travels to red bone marrow & it stimulates stem cells & developing RBCs - EPO has two major effects: (1) it stimulates cell divison rates in erythroblasts & in stem cells that produce erythroblasts, & (2) it speeds up maturation of RBCs, mainly by accelerating hemoglobin synthesis - Important in a person recovering from severe blood loss
Fate of Heme
- Each heme unit is stripped of its iron & converted to biliverdin, a green-coloured organic compound - Biliverdin is then converted to bilirubin, an orange-yellow pigment, & released from the macrophages into the bloodstream - In bloodstream bilirubin bind to albumin & is transported to liver for excretion in bile - In large intestines, bacteria convert bilirubin to related pigments called urobilinogens & stercobilinogens - Some urobilinogens are absorbed into bloodstream & are then excreted into urine (via kidney) - When exposed to oxygen, some urobilinogens & stercobilinogens are converted to urobilins & stercobilins which are eliminated in feces
Erythropoiesis in fetal period
- Embryonic blood cells appear in bloodstream during third week of development - These cells divide repeatedly, rapidly increasing no. - Blood forms mainly in vessels of embryonic yolk sac during first 8 weeks of development - As other organs appear some embryonic blood cells enter liver, spleen, thymus, & bone marrow - These embryonic cells differentiate into stem cells that divide to produce blood cells - Liver & spleen are primary sites of hemopoiesis from 2nd to 5th months of development, but as skeleton enlarges bone marrow becomes more important
Enzymatic removal of blood antigens (a more recent technique)
- Enzymes can be used to strip off A or B surface antigens from RBCs & create type O blood in the laboratory - Procedure is expensive & time consuming, & has limited use in emergency treatment
Process prior to stages of red blood cell (RBC) maturation
- For RBCs to be produced, first hematopoietic stems cells (AKA hemocytoblasts) in the red none marrow must divide - These stem cells produce two types of cells: (1) myeloid stem cells, which in turn divide to produce RBCs & several classes of white blood cells, & (2) lymphoid cells, which divide to produce white blood cells called lymphocytes
urobilins and stercobilins
- Found in feces & thus causes poo to be yellow-brown or brown
urobilins
- Found in urine & thus causes urine to be yellow
Describe why the categorisation of granular leukocytes & agranular leukocytes (although convenient) is somewhat misleading
- Granules in "granular leukocytes" are secretory vesicles & lysosomes - While the "agranular leukocytes" also contain these secretory vesicles & lysosomes, but they are just smaller & difficult to see ender a light microscope
Hemoglobin (Hb or Hgb) structure
- Have a complex quaternary structure - Each Hb molecule has two alpha (α) chains & two beta (β) chains of polypeptides - Each chain is a globular protein subunit (resembles the myoglobin in skeletal & cardiac muscle cells) - Each Hb chain contains a single molecule of heme, a nonprotein pigment that forms a ring - Each heme unit holds an iron ion that can bind to oxygen, as well as reversibly unbinding to oxygen - Each Hb contains 4 heme units
White blood cells (WBCs) AKA leukocytes
- Have nuclei & other organelles, & they lack hemoglobin - Help defend the body against invasion by pathogens - They also remove toxins, wastes, & abnormal or damaged cells - Most of the WBCs in body at any moment are in the connective tissue proper or in organs of the lymphatic system - Circulating WBCs are only a small fraction of total WBC population
Examples of conditions that affect hematocrit
- Hematocrit increases during dehydration, due to decrease in plasma volume, or after stimulation with the hormone erythropoietin - Hematocrit decreases as a result of internal bleeding or problems with RBC formation - So hematocrit doesn't provide specific diagnostic info, but does indicate that more specific tests are needed
Blood conditions related to hemoglobin (Hb) recycling
- Hemoglobinuria condition occurs when abnormally large numbers of RBCs break down in bloodstream, so urine may turn red or brown - Presence of intact RBCs in urine, a sign called hematuria, occurs only after kidney damage or damage to vessels along urinary tract
Types of white blood cells (WBCs) that are part of the body's nonspecific defences
- Include neutrophils, eosinophils, basophils, & monocytes - A variety of stimuli activate such defences, which don't discriminate between one type of threat & another - Neutrophils & eosinophils are sometimes called microphages, to distinguish them from larger macrophages in connective tissues - Macrophages are monocytes that have moved out of the bloodstream & have become actively phagocytic
Cardiovascular system
- Includes a pump (heart) that circulates the fluid & series of conducting hoses (blood vessels) that carry it throughout the body
Cross-match testing
- Involves exposing the donor's RBCs to a sample of the recipient's plasma under controlled conditions - Procedure reveals significant cross-reactions involving surface antigens other than A, B, or Rh
Recycling of iron
- Iron ions extracted from heme molecules may be bound & stored in phagocytic cell or released into bloodstream, where they bind to transferrin, a plasma protein - RBCs developing in red bone marrow absorb amino acids & transferrins from bloodstream & use them to make new hemoglobin molecules - Excess transferrins are removed in liver & spleen, & iron is stored in two special iron-protein complexes which are ferritin & hemosiderin
Hemoglobin (Hb or Hgb)
- Is responsible for the RBC's ability to transport oxygen & carbon dioxide. - Its molecules account for more than 95% of a RBCs intracellular proteins. - Hemoglobin content of whole blood is reported in grams of Hb per deciliter (100 mL) of whole blood - Normal ranges are 14 - 18 g/dL in males & 12 - 16 g/dL in females
Neutrophils
- Its name reflects fact that its granules are chemically neutral & thus difficult to see with either acid or basic (alkaline) dyes - Make up 50 to 70% of circulating WBCs (most numerous) - Have a short lifespan as survive in bloodstream for only 10 hours, while only live max 30 minutes when actively engulfing debris or pathogens - Its breakdown / death releases chemicals that attracts other neutrophils to site
Origins of plasma proteins & implications of this in terms of health
- Liver synthesizes & releases more than 90% of the plasma proteins, including all albumins & fibrinogen, most globulins, & various pro-enzymes - Liver disorders can alter composition & functional properties of blood - E.g. some forms of liver disease can lead to uncontrolled bleeding due to inadequate synthesis of fibrinogen & other proteins involved in clotting
Types of white blood cell (WBC) important for specific defences
- Lymphocytes are responsible for specific defences - They mount a counterattack against specific types of invading pathogens or foreign proteins
Importance of macrophages in hemoglobin (Hb) recycling
- Macrophages of liver, spleen, & red bone marrow play a central role in recycling RBC components - These phagocytes engulf aged RBCs & also detect & remove Hb molecules from hemolyzed or ruptured RBCs - If Hb released by hemolysis isn't phagocytized, its components won't be recycled
Formed elements of blood
- Made up primarily of red blood cells (AKA erythrocytes), white blood cells (AKA leukocytes), & platelets (cell fragments) - Make up about 45% of whole blood volume
Albumins
- Make up majority of plasma proteins (accounts for roughly 60%) - Major contributors to plasma osmolarity & osmotic pressure - Transport fatty acids, thyroid hormones, some steroid hormones & other substances
Abundance of red blood cells (RBCs)
- Make up roughly one-third of all cells in human body - Standard blood test reports no. of RBCs per microliter of whole blood as red blood cell count, with adult males having a higher count than adult females - A single drop of whole blood contains about 260 million RBCs, while the blood pf an average adult has 25 trillion RBCs
Structure of Neutrophils
- Mature ones have a very dense, segmented nucleus with two to five lobes (resemble beads on a string) - Thus neutrophils have another name, which is polymorphonuclear leukocytes (PMNs) - Are roughly 12 μm in diameter, & their cytoplasm is packed with pale granules containing lysosomal enzymes & bactericidal (bacteria-killing) compounds
Giving blood in an emergency situation (e.g. person with sever gunshot wound may require 5 litres of blood before damage can be repaired)
- May not be enough time for preliminary blood testing - In this situation type O blood (preferably O-) would be administered as donor's type O lacks both A & B surface antigens so won't trigger cross-reaction by anti-A &/or anti-B antibodies in recipient - As cross-reactions with type O blood are very unlikely, it is sometimes referred to as universal donor
Fate of hemoglobin (Hb) during recycling
- Once a phagocyte has engulfed & broken down an RBC, each part of Hb molecule has a different fate - Alpha & beta chains of Hb are filtered by kidneys & eliminated in urine - Globular proteins are broken apart into their component amino acids, which are either metabolized by cell or released into bloodstream for use by other cells - Only iron of each heme unit is recycled, & the remaining portion is processed separately
Interactions of heme unit (of hemoglobin (Hb)) with oxygen
- Oxygen molecules can interact / bind to iron of heme unit to form oxyhemoglobin (HbO2) - Blood that contains RBCs filled with oxyhemoglobin is bright red - Iron-oxygen interaction is very weak, so can easily dissociate from each other without damaging oxygen molecule or heme unit - Hb molecule whose iron isn't bound to oxygen is called deoxyhemoglobin - Blood that contains RBCs filled with deoxyhemoglobin is dark red
Compatibility testing
- Performed in advance to any transfusion, in order to avoid cross-reactions - Process normally involves two steps: (1) a determination of blood type, & (2) a cross-match test
Plasma proteins
- Plasma contains significant quantities of dissolved proteins, which are albumins, globulins, & fibrinogen - These 3 types make up more than 99% of plasma proteins (remaining 1% is composed of enzymes & hormones whose levels vary widely)
Lack of agglutinins (antibodies) present in Rh-negative individuals
- Plasma of Rh-negative individuals doesn't contain anti-Rh antibodies - These antibodies are present only if individual has been sensitized by previous exposure to Rh+ RBCs - Such exposure can occur accidentally during a transfusion, but can also accompany a seemingly normal pregnancy with a Rh- mother & Rh+ fetus
Agglutination
- Process in which the foreign RBCs agglutinate or clump together due to attack by agglutinins (antibodies)
Transfusions
- Process of transferring whole blood or blood plasma from one person to another - Used when blood loss is substantial - Blood types of donor & recipient should be compatible (so won't cross-react) - Transfusion of incompatible blood can be life threatening as a cross-reaction can occur
Hormone Binding Proteins
- Provide a reserve of hormones in the bloodstream. - E.g. thyroid-binding glonulin & transthyretin, which transport thyroid hormones - E.g. transcortin, which transports adrenocorticotropic hormone (ACTH)
Erythropoiesis in adult period
- RBC formation takes place only in red bone marrow, or myeloid tissue - Myeloid tissue is located in portions of vertebrae, sturnum, ribs, skull, scapulae, pelvis & proximal limb bones - Other marrow areas contain a fatty tissue known as yellow bone marrow - Under extreme conditions e.g. severe & sustained blood loss, areas of yellow marrow can convert to red marrow, increasing the rate of RBC formation
Hemolytic disease of the newborn (HDN) AKA erythroblastosis fetalis
- RBC-related disorder caused by a cross-reaction between fetal & maternal blood types - During pregnancy, when fetal & maternal vascular systems are closely intertwined, mother's antibodies may cross placenta, attaching & destroying fetal RBCs - Condition has many forms, some quite dangerous (e.g. causes anemia, jaundice, can result in fetus death), while others so mild that remain undetected - Most common when mother's blood type is Rh-negative & baby's blood is Rh-positive, especially during 2nd pregnancy - Can be treated / prevented by administering antibodies (RhoGAM) to mother in 26-28 weeks of pregnancy & during & after delivery
Red blood cell (RBC) structure
- RBCs are among the most specialized cells of body - Each RBC is a biconcave disc with a thin central region & thicker outer margin - Average RBC has 7.8 μm diameter & 2.85 μm maximum thickness, although center thins to 0.8 μm - Cytoplasmic surface of an RBC plasma membrane is a meshwork of flexible proteins
Red blood cell (RBC) turnover
- RBCs are exposed to severe physical stresses - During a single trip from heart, through peripheral tissues, & back to heart again, RBCs will be bumped against walls, squeeze through capillaries, & bang into each other etc - Lots of ware & tear & no repair mechanism means RBCs are short lived - After ~120 days its plasma membrane ruptures or damage detected by phagocytes which engulf it - New RBCs enter at a comparable rate to those removed, with 1% being replaced each day
Red blood cells (RBCs) bend and flex when entering small capillaries
- RBCs are very flexible - By changing shape, individual RBCs can squeeze through capillaries as narrow as 4 μm
Red blood cells (RBCs) have a large surface area to volume ratio
- RBCs carry oxygen bound to intracellular proteins - Oxygen must be absorbed or released quickly as RBC passes through capillaries of lungs or peripheral tissues - Greater the surface area per unit volume, the faster the exchange between RBBC's interior & the surrounding plasma - Total surface area of all RBCs in blood of typical adult is about 3800 square meters
Function of blood: transporting dissolved gases, nutrients, hormones, & metabolic wastes
- Red blood cells (RBCs) carry oxygen from lungs to peripheral tissues & carries CO2 back to the lungs - Distributes nutrients absorbed by digestive tract or released from storage in adipose tissue or in liver - Carries hormones from endocrine glands towards their target cells - Absorbs waste produced by tissue cells & carries them to kidneys for excretion
Whole blood
- Refers to the mixture of both plasma & formed elements (red blood cells, white blood cells & platelets) - Components of whole blood can be fractionated, or separated, for analytical or clinical purposes
Alternative method to avoid compatibility problems
- Replace the lost blood with synthetic blood substitutes, which do not contain surface antigens (so can't trigger a cross-reaction)
Anemia
- Results due to the hematocrit being low or the hemoglobin content of RBCs being reduced - Interferes with oxygen delivery to peripheral tissues - Every system is affected as organ function deteriorates due to oxygen starvation - Anemic individuals become weak, lethargic, & may also become confused as brain is affected too
Sickle Cell Disease (SCD)
- Results from a mutation affecting the amino acid sequence of the beta chains in hemoglobin molecule. - Often develop anemia as a result
Hemoglobin (Hb) function: binding & releasing oxygen & carbon dioxide
- Roughly 98.5% of oxygen carried by blood is bound to Hb molecules inside RBCs - Amount of oxygen bound to Hb depends mostly on oxygen concentration of plasma, as when plasma oxygen levels low then Hb releases oxygen - When carbon dioxide levels in plasma are elevated, the alpha & beta chains of Hb bind to carbon dioxide to form carbaminohemoglobin - For plasma in lung capillaries high oxygen level & low carbon dioxide level, so RBCs absorb oxygen & release carbon dioxide when in the capillaries
Similarity between plasma & interstitial fluid
- Similar composition because water, ions, & small solutes are constantly exchanged between plasma & interstitial fluid across walls of capillaries
Additional characteristic feature of some white blood cells (WBCs)
- Some types of WBCs are capable of phagocytosis - These WBCs may engulf pathogens, cell debris, or other materials
Red blood cells (RBCs) form stacks that smooth blood flow through narrow blood vessels
- Stacks of RBCs are called rouleaux & are like stacks of dinner plates - Rouleaux (stacks) form & dissociate repeatedly, without affecting the cells involved - An entire stack can pass along a blood vessel that is only slightly larger than the single diameter of a RBC - In contrast, individual RBCs would bump walls, bang together, & could restrict or prevent blood flow
Blood type testing
- Standard test for blood type considers only 3 surface antigens most likely to produce dangerous cross-reactions: A, B, & Rh - Test involves taking drops of blood & mixing them separately with solutions containing anti-A, anti-B, & ant-Rh (anti-D) antibodies - Any cross-reactions (RBCs clumping) are then recorded - E.g. if RBCs clump when exposed to anti-A & anti-B antibodies then blood type of individual is AB, but if no reaction occurs then blood type is O - Presence or absence of Rh surface antigen also noted, & is classified as Rh positive or Rh negative - Blood typing can be completed in a matter of minutes
Regulation of Erythropoiesis
- Stimulated directly by hormone erythropoietin (EPO) & indirectly by several hormones e.g. thyroxine, androgens, & growth hormone - RBC formation can also be limited by inadequate supplies of amino acids, iron, & vitamins (including B vitamins & folic acid) to red bone marrow in order to manufacture hemoglobin (via protein synthesis)
Agglutinogens
- Surface antigens on your own RBCs which the immune system ignores (recognises it as "self")
Physical characteristics of blood
- Temperature is about 38˚C, slightly above normal body temperature - Is 5 times as viscous as water, (so 5 X sticky, 5 X cohesive, & 5 X resistant to flow), due to interactions among dissolved proteins, formed elements, & water molecules in plasma - Is slightly alkaline with a pH between 7.35 & 7.45
Relationship of red blood cell (RBC) structure to red blood cell function (i.e. important effects on RBC function)
- The biconcave shape & flexible plasma membrane have 3 important effects on RBC function: 1. Gives each RBC a large surface area to volume ratio 2. Enables RBCs to form stacks that smooth blood flow through narrow blood vessels 3. Enables RBCs to bend & flex when entering small capillaries
Plasma
- The fluid matrix of blood, makes up about 55% of volume of whole blood - Its components include various plasma proteins, other solutes (primarily nutrients, electrolytes, & wastes) & water - Water makes up 92%, while plasma proteins make up 7%, & other solutes make up 1%
Hematuria
- The presence of intact RBCs in urine - Occurs only after kidney damage or damage to vessels along the urinary tract.
Erythropoiesis
- The process of RBC formation or production - In red bone marrow hematopoietic stems cells (AKA hemocytoblasts) divide to produce myeloid stem cells, which in turn divide to produce RBCs (in adults) - Occurs throughout life - Many factors stimulate this process, such as a decreased oxygen level or increased erythropoietin
Hemopoiesis (AKA hematopoiesis)
- The process through which formed elements are produced - Two populations of stem cells, which are myeloid stem cells & lymphoid stem cells, are responsible for the production of formed elements
Red blood cells (RBCs) AKA erythrocytes
- These are the most abundant blood cells & make up about 99.9% of formed elements - Are essential for the transport of oxygen in the blood - Are biconcave disc shaped, & contains the red pigment, hemoglobin - Hemoglobin binds & transports the respiratory gases oxygen & carbon dioxide
White blood cell (WBC) functional characteristic: All are attracted to specific chemical stimuli
- This characteristic, called positive chemotaxis, guides WBCs to invading pathogens, damaged tissues, & other active WBCs
Method to increase blood's oxygen-carrying capacity (rather than its plasma volume) via transfusion
- Transfuse packed RBCs with a minimal amount of plasma
Steroid-binding proteins
- Transport steroid hormones in the blood. - E.g. testosterone-binding globulin (TeBG) binds & transports testosterone
Metalloproteins
- Transports metal ions. - E.g. transferrin, which transports iron (Fe2+)
Types of agglutinins (antibodies) present in the different blood types
- Type A blood: plasma contains anti-B antibodies, which will attack type B surface antigens - Type B blood: plasma contains anti-A antibodies, which will attack type A surface antigens - Type O blood: plasma contains both anti-A & anti-B antibodies, which will attack both type A & type B surface antigens - Type AB blood: plasma contains neither anti-A nor anti-B antibodies
Reason why surface antigens on donor's cells are more important in determining compatibility than antibodies in donor's plasma
- Unless large volumes of whole blood or plasma are transferred, cross-reactions between donor's plasma & recipient's blood won't produce significant agglutination - Due to donated plasma being diluted quickly through mixing with larger plasma volume of recipient
White blood cell (WBC) characteristics
- Unlike RBCs, WBCs circulate for only a short time during their life span - WBCs migrate through the loose & dense connective tissues of the body - They use bloodstream to travel from one organ to another & for rapid transportation to areas of infection or injury - Can detect chemical signals of damage to surrounding tissues & will enter damaged area
White blood cell (WBC) functional characteristic: All can migrate out of the bloodstream
- When WBCs in bloodstream are activated, they contract & adhere to vessels walls in a process called margination - After further interaction with endothelial cells, the activated WBCs squeeze between adjacent endothelial cells & enter surrounding tissue via process called emigration or diapedesis
Hemoglobinuria
- When abnormally large numbers of RBCs break down in the bloodstream, urine may turn red or brown
Cross reaction (AKA transfusion reaction)
- When an antibody meets its specific surface antigen, the RBCs agglutinate / clump & may also hemolyze RBCs so they break up into bits - Occurs if donor & recipient blood types are not compatible - Clumps & fragments of RBCs under attack form drifting masses that can plug small blood vessels in kidneys, lungs, heart, or brain, thus damaging or destroying affected tissues
Other features of red blood cells (RBCs) and reasons for this
- When developing RBC differentiates, it loses any organelle not directly associated with the transport of respiratory gases (its primary function) - Mature RBCs are anucleate (without nuclei) & they only retain the cytoskeleton - Lack nuclei, ribosomes, & mitochondria - Few organelles & no ability to make proteins or repair self means RBC energy demands are low, while lifespan is relatively short (last less than 120 days) - RBCs obtain energy via anaerobic metabolism of glucose that is absorbed from surrounding plasma - No mitochondria ensure absorbed oxygen is carried to peripheral tissues & not stolen by mitochondria
Jaundice and its cause
- Yellowing of the skin & the whites of the eyes - Bile ducts are blocked or liver cannot absorb or excrete bilirubin, so circulating levels of the compound climbs rapidly - Bilirubin then diffuses into peripheral tissues, giving them a yellow colour that is most apparent in skin & over sclera of the eyes
3 functional characteristics of circulating white blood cells (WBCs)
1. All can migrate out of the bloodstream 2. All are capable of amoeboid movement 3. All are attracted to specific chemical stimuli
Differences between plasma & interstitial fluid
1. Levels of respiratory gases (oxygen & carbon dioxide, due to the respiratory activities of tissue cells), 2. Concentrations & types of dissolved proteins (because plasma proteins cannot cross capillary walls).
Functions of blood
1. Transports dissolved gases, nutrients, hormones & metabolic waste. 2: Regulation of pH & ion composition of intersitial fluid 3: Restriction of fluid losses at injury sites. 4: Defense against toxins & pathogens. 5: The stabilization of body temperature