Physiology of Blood Flashcards
What makes up the blood plasma?
It makes up about 4% (3L) body weight. 95% water & various substances in solution and suspension: ions, small organic molecules, and plasma proteins. Also sometimes enzymes, hormones, vitamins and products of digestion.
What are the components of blood?
Plasma and the formed elements: erythrocytes, leukocytes and thrombocytes.
What are the three categories of plasma protein?
Globulins, Albumins and clotting factors (fibrinogen and prothrombin)
Describe the albumins
smallest and most abundant (60%) plasma proteins. Import for lipid and liver-produced steroid hormone transport and oncotic pressure.
Describe the globulins
About 40% of total plasma protein. Alpha and Beta made in liver and transport lipids and fat-soluble vitamins. Gamma are antibodies.
What is a haematocrit?
The haematocrit or packed cell volume is found by centrifuging a small sample of blood until the cellular contents are packed at the bottom. Ratio of red cells to total. About 0.4-0.52:1L, after correcting for plasma trapped between cells. Lower in larger blood vessels because of axial streaming.
What makes up the buffy coat of a haematocrit?
Leukocytes and platelets. White layer that moves around when swilled and is bigger following infection.
Describe red blood cells
small biconcave disks, diameter 7-8micrometers. No nucleus. Thin and flexible to squeeze through capillaries. Large SA:V ratio. Haemoglobin synthesised by red cell precursors in the bone marrow.
Describe white blood cells in general
larger than RBCs and have a nucleus. Involved in immunity, able to pass though capillary walls - diapedesis. Able to then move through tissues by an amoeboid motion.
Describe the granulocytes
AKA polymorphonuclear leukocytes with lobes nuclei. neutrophils, eosinophils and basophils. Their function is to destroy invading pathogens. They are motile and are attracted to injury sites by chemicals released from injured
tissue or foreign organisms - chemotaxis. The cells engulf these organisms and destroy them by enzymes stored within lysosomes - phagocytosis.
Describe the monocytes
AKA Macrophages. Larger with kidney shaped nuclei. Migrate from bone marrow to spleen, liver, lungs, lymph nodes and more. Antigen presenting phagocytes. Recognised by T cells to stimulate B cell production.
Describe the lymphocytes
B & T lymphocytes. Producing antibodies and carrying out cell mediated immune response respectively.
Describe Thrombocytes
Platelets aren’t really cells but membrane bound cell fragments which bud off from megakaryocytes in the bone marrow. No nucleus, life span of ~10 days. Help control bleeding and maintain endothelium.
What is the Starling equilibrium?
Hydrostatic pressure (about 25 mm Hg) forces water through the leaky capillary fenestrations, but this is offset by the colloid osmotic, or oncotic absorption pressure due to the plasma proteins.
What is the Starling equation?
Jᵥ = Kf [(Pc - Pi) - σ(πc - πi)]
Where:
Jᵥ = Net fluid flux
Kf = Filtration coefficient
Pc = Capillary hydrostatic pressure
Pi = Interstitial hydrostatic pressure
σ = Reflection coefficient
πc = Capillary oncotic pressure
πi = Interstitial oncotic pressure
Note:
[(Pc - Pi) - σ(πc - πi)] is the net driving pressure.
What is the importance of the filtration coefficient?
Describes the leakiness of the capillary walls - larger = more fluid can be filtered across. Can be changed for example by histamine release of mechanical damage.
What is the reflection coefficient?
Reflects how some plasma proteins are able to diffuse across the capillary walls, which would bring down oncotic pressure in the capillaries. 1 in Glomerular capillaries and about 0 in hepatic sinusoids.
What is Oedema and what are its causes?
When filtration forces significantly exceed absorption forces an accumulation of extravascular fluid occurs called an oedema. Can be caused by decreased oncotic pressure: e.g. loss of plasma proteins due to liver failure or starvation. OR increased hydrostatic pressure e.g. due to congestive heart failure.
Describe the A(O) blood group
These individuals have agglutinogen A antigens on their RBCs, and as such don’t have anti-A antibodies in their plasma, but do have anti-B
Describe the B(O) blood group
These individuals have agglutinogen B antigens on their RBCs, and as such don’t have anti-B antibodies in their plasma, but do have anti-A
Describe the AB Blood group (least common)
These individuals have agglutinogen A&B antigens on their RBCs, and as such don’t have any agglutinins in their plasma
Describe the O Blood group (most common)
Also known as universal donors, these individuals have no agglutinogen antigens on their RBCs, and as such their blood doesn’t clump when donated to anyone, but they can only receive transfusions from other O individuals as they have both anti-A and anti-B agglutinins.
What is the Rhesus blood group system?
Rh positive individuals have the D-antigen, or Rhesus factor, on their RBCs. Heritable in the same way as ABO groups.
What causes hemolytic disease of the newborn (HDN)?
HDN happens when an Rh-negative mother produces anti-Rh antibodies after exposure to Rh-positive fetal blood. This often occurs during birth or in later pregnancies, leading to immune attacks on the fetus’s red blood cells. It affects ~1 in 160 births.
