The Blood - Lecture 1 PDF

THE BLOOD - lecture 1 Friday, September 29, 2023 10:11 AM INTRODUCTION → Blood represents about 8% of total body weight → Average volume: ○ 5 liters in women with packed cell volume (hematocrit) of 42% ○ 5.5 liters in men with hematocrit of 45% ADDTIOINAL NOTES - Venou...

THE BLOOD - lecture 1 Friday, September 29, 2023 10:11 AM INTRODUCTION → Blood represents about 8% of total body weight → Average volume: ○ 5 liters in women with packed cell volume (hematocrit) of 42% ○ 5.5 liters in men with hematocrit of 45% ADDTIOINAL NOTES - Venous blood is blood found in the veins ○ Dark red, darker than blood found in the arteries - Artery blood is bright red Picture description: Formed elements: - Gravity makes dense elements sit at the bottom ( formed elements) - Red due to RBC bc it makes up most of the formed elements Plasma: - Clear / yellow portions = plasma ○ Made mostly of water ○ Will not be clear in colour if a person has a lot of lipids in their system - Hematocrit = 45% formed elements divided by 100% total blood volume → Consists of three types of specialized cellular elements suspended in plasma (liquid portion of blood) ○ Erythrocytes § Red blood cells: important in O2 transport § Latin: erythro-cytes = red-cells § Doughnut-shaped ○ Leukocytes § White blood cells; immune system's mobile defense units § Latin: leuko-cytes = white-cells § Actually colourless ○ Platelets (thrombocytes) § Cell fragments; important in hemostasis § Blood clotting → The think layer separating the two blood components is called the buffy coat ○ White-ish coat ○ Where all the WBC / immune cells are PHYSIOLOGICAL ROLE: → Carrying: oxygen, nutrient's, hormones, metabolic wastes, heat → Regulation: (body temperature, pH) ○ Humans are warm blooded so when its cold the vessels contract to maintain temp. and when its hot they relax → Protection: clotting, immunoglobulins ○ Protects from injury, closes open wounds PLASMA CONSTITUENT FUNCTIONS Plasma Water - Acts as a transport medium, caries heat Electrolytes - Are important in membrane excitability; distribute fluid by osmosis ECF and ICF; buffer pH charges most abundant electrolytes are sodium (NA+) and chloride (Cl-) Nutrients, waste, - Are transported in blood; blood CO2, plays a role in acid-base balance gases, hormones PLASMA PROTEINS → Functions ○ In general, exert an osmotic effect important in the distribution of the ECT b/w the vascular and interstitial compartments ○ Is the primary force that prevents excessive loss of plasma from the capillaries into the interstitial fluid ○ Responsible for plasma's capacity to buffer changes in pH → All synthesized in the liver except for gamma globulins Albumins → Transport many substances, contributes most to colloid osmotic pressure ○ Creates pressure to prevent leaks of fluid from the blood vessels to the interstitial space through the extravascular space → Most abundant in BLOOD ○ Makes half of proteins → Carry other substances that can't swim / interact in water → Is NON-SPECFIFC Globulins → Alpha and beta ○ Transport many water-insoluble substances § SPECIFIC - cholesterol, iron, complement ○ Involved in blood-clotting process → Gamma ○ Are antibodies / immunoglobulins § Not made in the blood but by immune cells in other tissue → Fibrinogen ○ Is an inactive precursor for a clot's fibrin meshwork ○ Becomes active when blood clotting in needed ○ In a lab, red cap: forms a clot on purpose bc there is no additive ○ Serum Is plasma minus the fibrinogen → These proteins stay in the plasma, where they preform many valuable functions: ○ Dispersed as a colloid ○ b/c of size, do not diffuse through capillary wall which creates osmotic pressure ○ Partially responsible for plasma's capacity to buffer changes in pH ○ All synthesized by the liver except the Gamma globulins (produced by lymphocytes) ERYTHROCYTES → Also called red blood cells → 5 billion RBCs / 1 ml of blood! (5x106 / mm3) → Flat in the middle to increase surface area of the membrane → Bilayer is thinner to increase hydrogen transport ○ Shape and content ideally suited to carry out their primary function: transporting O2, H2 and CO2 → Thinness of cell enables O2 to diffuse rapidly between the exterior and innermost regions of the cell → Great flexibility of the plasma membrane (diameter 8 µm = into 3 µm capillaries ERYTHROYTES: IN THE PRESENCE OF HEMOGLOBIN (Hb) → Found only in red blood cells → Pigment containing iron ○ Appears reddish when oxygenated ○ Appears bluish when deoxygenated Picture description: → 1 haemoglobin → 4 protein subunits ○ 2 alpha 2 beta → Each subunit contains its own heme group (yellow) ○ 4 iron-containing non-protein groups ○ Each is bound to one of the polypeptides ○ Each iron atom can bind to one O2 molecule ○ Iron is what carries the oxygen → Binding of iron and oxygen is reversible ( can bind and release) → Each Hb molecule can transport 4 O2 molecules → O2 is poorly soluble in water -> 98.5% of O2 is carried in the blood bound to Hb → A single RBC is stuffed wit more than 250 billion Hb molecules, so it can carry >100 million O2 molecules ERYTHTOCYTES: HAEMOGLOBIN ALSO COMBINES WITH: → Carbon dioxide - CO2 ○ Although that's not the main way through which co2 is carried back from the tissue to the lungs → Acidic hydrogen ion portion (H+) ○ Of ionized carbonic acid; generated at the tissue level from CO2 (buffering capacity) → Carbon monoxide -CO ○ Not normally in the blood, but if inhaled -> CO poisoning - binding is irreversibly → Nitric acid - NO2 ○ vasodilator ( in lungs, NO relaxes and dilates the local arterioles -> O2 - rich blood can make it's vital rounds; stabilizes blood pressure MORE ERTHROCYTES STUFF → Mature erythrocytes contain no nucleus, organelles or ribosomes, got rid of them to carry more O2 → Contains key enzymes: ○ Glycolysis enzymes : § Necessary for generating energy needed to fuel active transport mechanisms involved in maintaining proper ionic concentrations within the cell § Rely entirely on glycolysis for ATP formation (no mitochondria) ○ Carbonic anhydrase § Critical in CO2 transport § Catalyzes reaction that ultimately leads to conversion of metabolically produced CO2 into bicarbonate ion (HCO-3 □ Primary form in which CO2 is transported in blood ( in addition to being bound into Hb) □ NOT TRANSPORTED AS A GAS → Cost / benefit with having no organelles ○ Benefit - more hemoglobin molecules ○ Cost = short life span → RBC have thin membranes = fragile ERYTHTOPOIESIS → No nucleus / organelles -> RBCs survive an average of only 120 days (nerve and muscle cells last a person's entire life) → At a given time, we have about 23-30 trillion RBC travelling in our vessels -> turn over of 2-3 million cells per second → Spleen removes most of the old erythrocytes from circulation ○ Dead RBC are recycles in the spleen, and gets replaces, phagocytes eat them → A major process is needed to regenerate trillions of red blood cells ○ Loss of RBC = low on oxygen PICTURE DESCRIPTION: ○ Need a robust system → The pluripotent stem cell has a nucleus → Erythroblast ○ last step that has a nucleus ○ Still in the bone marrow ○ Not mature yet → Reticulocyte ○ Don't leave the bone marrow ○ Organelles are degrading by digestive enzymes / lysosomes → Erythrocyte ○ Leaves the bone marrow ○ Lots of hemoglobin → RBCs cannot divide bc there is no nucleus -> new cells are produced to replenish dying ones. This is known as erythropoiesis: ○ occurs in red bone marrow - where there is no fat § Pluripotent stem cells in red bone marrow differentiate into the different types of blood cells, including RBCs and WBCs □ Only different types of BLOOD cells → Two important places: ○ Bone marrow = make RBC ERYTHROPOIESIS: CYCLE ○ Kidney = important endocrine hormones → EPO = erythropoietin ○ Acts in bone arrow ○ Made by the kidney ○ Knows when its needed, when oxygen levels drop § Kidney will sense it and increase EPO = which increases rate of RBC