Term 2 Lecture 3: Blood- RBC And Other Components Flashcards
Primary fluids of the body
Intracellular fluid
Extracellular fluid:
Blood, interstitial fluid, lymph
Circulatory system
Blood, blood vessels, lymph, lymph vessels and heart
Functions of blood
Transportation- gases, nutrients, hormones and waste
Regulation - pH (7.35-7.45), acts as a buffer, body temp, water balance
Protection - from microorganisms and cancer cells also aids in clotting and would repair
CAR : T cell therapy for cancer treatment
1)Collect blood sample from patient to harvest T-cells
2) make CAR T-cells in lab by inserting CAR genes into patients T cells
CAR= chimeric antigen receptor
3) grow millions of CAR T cells in lab
4) infuse CAR T cells into patients circulatory system
5) the CAR T cells bind to cancer cells and kill them
General facts about blood
Blood is a specialised connective tissue
Makes up 1/4 of all extracellular fluid
Adult human blood vol is 7% of total body weight e.g.
in a 58kg female ~4litres
In a 70kg male ~5litres (2 plasma 3 blood cells)
Plasma
Is ECM
92% water
7% proteins (Albumin ~60% Globulins ~35% Fibrinogen ~4%)
~1% enzymes/proenzymes/hormones
All plasma proteins except gamma globulins are produced by the liver
1% is organic molecules (aa, glucose, lipids, nitrogenous waste), ions (Na+, K+, Cl-, H+, Ca²+ & HCO3-), trace elements, vitamins, dissolved O2 & CO2
Blood vessels
Mean diameter/wall thickness
Artery: 4.0 / 1.0mm
Endothelium, elastic tissue, smooth muscle and fibrous tissue (all)
Arteriole: 30.0/ 6.0 micrometre
Endo and smooth
Capillary: 3.0/ 0.5 micrometres
Just endo
Venule: 20.0/ 1.0 micrometre
Endo and fibrous
Vein: 5.0/0.5mm
All
Capillaries
On average 10 billion in the adult human body and therefore cover the largest total cross sectional area of all vessels and have the lowest velocity due to being the narrowest type of vessel
Capillaries are exchange vessels between blood and interstitial fluid
- in systemic capillaries net pressure = hydrostatic pressure - colloid osmotic pressure
- colloid osmotic pressure within the capillary pulls fluid into the capillary
-excess water and solutes that filter out of the capillary are picked up by the lymph vessels and returned to the circulation - plasma proteins are responsible for colloid pressure
- colloid osmotic pressure is constant
-hydrostatic pressure drops from arterial to venous side
Capillary exchange takes place by diffusion, bulk flow and transcytosis
Diffusion - directly through endothelium
Transcytosis- vesicle transport through endothelium
Bulk flow: through channel in endothelium, between cells of endothelium*
- Endothelium normally forms continuous flat membrane but some have holes aka fenestrations or pores these are referred to as fenestrated or discontinuous epithelium
Cellular elements of blood
RBC (erythrocytes)
Platelets
WBC: lymphocytes, monocytes, neutrophils, eosinophils and basophils
Blood count: % of each component
Measured using a hematocrit tube (centrifuged)
RBC~ 42% WBC ~<1% Plasma ~58%
Read by a micro-capillary reader
The hematocrit (hct) is the % of total blood volume occupied by packed RBC (after centrifuge)
The hemoglobin (Hb) content of RBC is measured as total Hb content of blood (gHb/dl)
Mean RBC vol (MVC) in some disease states may be abnormally large or small e.g. abnormally small in those w/anaemia
RBC count in millions per microlitre a machine counts the cells as they stream through a beam of light
Morphology of RBC can give clues to diseases - sometimes cells lose their flat disc shape and become spherical (spherocytosis) or sickle shaped (sickle cell anaemia)
Total WBC count tells total no. of all types
Differential WBC count estimates rel no. of all 5 types of white cell, carried out by medical technologists using a blood smear
Platelet count- suggestive of bloods ability to clot
Hematocrit average result:
Male/ female
Hematocrit: 40-54% / 37-47%
Hemoglobin (gHb/dl): 14-17% / 12-16%
RBC count (cells/microlitre):
4.5-6.5x10⁶ / 3.9-5.6x10⁶
Total WBC count (cells/microlitre)
4-11x10³ / 4-11x10³
Differential WBC count same proportions in males and females
Neutrophils 50-70%
Eosinophils 1-4%
Basophils <1%
Lymphocytes 20-40%
Monocytes (per microlitre) 15-45x10⁴
Plasma Vs serum
Plasma: ~ 52% contains albumins, immunoglobulins, lipids (lipoproteins), hormones, vitamins and salts
Buffy coat: leukocytes and platelets (1%)
Hematocrit: RBC 42-47% blood collected and centrifuged in presence of an anticoagulant (heparin or sodium citrate)
Serum
Majority, protein rich fluid lacking fibrinogen but containing albumin, immunoglobulins and other components
Blood collected w/out anticoagulant and left to coagulate
Blood components: cells
RBC- O2 & CO2 transport, most abundant cell in the body
WBC - 5 types, immune defence and phagocytosis
Platelets - clotting
Wright’s stain is used to reveal nuclear shape and cytoplasmic colour
Methods of RBC analysis
Blood smear
Cross section
Super resolution imaging
Electron microscopy (SEM)
In blood vessel imaging
RBC notes
- most abundant cell type in blood
- lose their nuclei in maturation stage
- lack mitochondria and ER so are unable to renew plasma membrane components, carry out protein synth or aerobic metabolism, also cannot renew enzymes therefore RBCs are short-lived usually lasting 4 months
- have an elaborate cytoskeleton
- mature cells are biconcave discs
- remarkably flexible
- contain haemoglobin
- bind O2 in heme group
- bind some CO2 on globulin
- generate ATP by glycolysis
Old RBCs are broken down and bilirubin is detoxified
Old RBCs lose their flexibility so become more fragile and likely to rupture
They are engulfed by scavenging macrophages in the spleen, liver, lymph nodes and bone marrow
Senescent RBC engulfed by phagocyte
Broken down to globulin, bilirubin, heme and iron
Bilirubin is released and binds to albumin
Bilirubin is detached from albumin and taken into a hepatocyte as free bilirubin where it is conjugated to glucuronic acid to form conjugated bilirubin a soluble detoxified form that is released into bile.
Bilirubin: yellow byproduct of haemoglobin metabolism
Not water soluble - toxic and causes brain damage
Cannot be directly removed from the body
Hepatocytes bind bilirubin to glucuronic acid using UDP-glucoronyl transferase to form bilirubin diglucoronide
^aka conjugated bilirubin
Which is water soluble and expelled into the intestine where it is further metabolised to stercobilin, urobilinogen and urobilin (uros make plasma yellow)
Bilirubin build up results in jaundice (icterus) it also causes gall stones, alcoholic liver disease, pancreatitis, hepatitis and sickle cell anaemia
Lifecycle of erythrocytes (RBCs)
Bone marrow: RBCs are generated (erythropoiesis) in the bone marrow then enter the blood stream
Spleen: When they become senescent the spleen digests them to AAs and haemoglobin which is then split into iron and bilirubin
Liver: Bilirubin is converted to bile in the liver and excreted in faeces. The liver also converts Ferritin (F-iron) is converted to transferrin (T - Iron) which returns to the bone marrow through the circulatory system.
Kidneys: Circulating bile is excreted by kidneys in urine. EPO (erythroprotein) returned to bone marrow.
RBC cytoskeleton
Anion transporter channel allows HCO3- to exit through the plasma membrane in exchange for intake of Cl-. This exchange facilitates release of CO2 in the lungs.
Junctional complex - spectrin* tetramers are linked to a 3 protein complex: a short actin filament of actin monomers linked to tropomyosin and protein 4.1. binding
between actin and spectrin is stimulated by adducin (a calmodulin binding protein)
*Spectrin- large dimeric protein consisting of 2 polypeptide chains alpha spectrin (240kd) and beta spectrin (220kd). The 2 polypeptides associate in antiparallel pairs to form a rod 100nm long. Two chains join head to head to form a tetramer found in the cortical region of the RBC.
Erythrocyte pathology: Hereditary spherocytosis (HS)
RBCs are spheroidal, less rigid, of variable diameters and subject to destruction in the spleen. This alteration is caused by cytoskeletal abnormalities involving site interactions between spectrin alpha/beta and protein 4.1
Erythrocyte pathology: membrane/metabolic/haemoglobin defects
Membrane cytoskeletal defects
Elliptocytosis: AD, EPB41, SPTA1 or SPTB genes (EPB41 codes protein 4.1)
SPTA1 & SPTB encode alpha/beta spectrins
Spherocytosis occurs due to AD spectrin deficiency.
Clinical features: jaundice, anaemia, splenogematic
Metabolic defects:
Glucose 6 phosphate dehydrogenase (G6PD) or pyruvate kinase deficiency
Haemoglobin defects:
Alpha or beta globin chain defects
Erythrocyte pathology: sickle cell anaemia
Sickle cell anaemia:
Hemoglobins HbA (alpha 2, beta 2 96%) HBA2(alpha 2 and delta 2 3%) fetal Hb, HBF(alpha 2 gamma 2 1%)
Incidence: 8% afro Americans - heterozygous mutation up to 30% in parts of Africa where malaria is endemic
Cause: beta globulin chain carries a E6V point mutation causing a glutamine to be substituted with valine. Therefore RBCs have a lifespan of only 20 days as their membranes are more susceptible to damage and dehydration with more rigidity and sickled form.
Leads to:
-extravascular chronic anaemia - sickled cells are broken down by spleen
-microvascular obstructions
-hemolysis - on deoxygenation Hb aggregates affecting RBC cell shape which can damage plasma membrane causing hemolysis
Infarction- Cells may regain normal shape with O2 but repeated rounds of deformation lead to aggregation causing an infarction - death of an area of tissue e.g. in lung or bone marrow
Erythrocyte pathology: Beta- Thalassemia
(treated by bone marrow transplant at an early age)
Cause: a defect in transcription/RNA splicing/translation
More than 100 diff mutations - most are single base substitutions
Effect: reduced beta globulin synthesis and in some cases complete absence of beta globulin
Summary of defects:
-inadequate HbA formation
-RBCs hypochromic and microcytic
- unpaired alpha chains aggregate and damage the membrane
- extravascular hemolysis
- growth retardation
- skeletal deformities
- cardiac failure due to iron overload
Summary: mutation in Hb peptide chain leads to lack of beta globulin and aggregation of alpha globulin. This leads to erythrocyte deformation resulting in destruction in the spleen. As less RBCs are present in the circulation this leads to anaemia. Expansion of bone marrow to produce enough erythrocytes to compensate for losses leads to skeletal deformation
