Fluids and Blood Functions

Fluids of the body

• Cells are serviced by blood, composed of plasma and blood cells, circulating in vessels
• Blood transports oxygen, nutrients, and wastes, including C02
• Interstitial fluid is around the cells, formed from blood filtration, giving rise to lymph after entering lymphatic vessels
• Nutrients and oxygen diffuse from the blood into the interstitial fluid and then into the cells
• Wastes move in the reverse direction

Functions of blood

• Blood transports oxygen, carbon dioxide, metabolic wastes, nutrients, heat, hormones, and medications
• Blood regulates pH, body temperature, helps regulates intracellular fluid composition
• Blood provides protection from disease via immunity and inflammation

Physical characteristics of blood

• Blood is thicker than water, flowing slower due to blood cell count, especially RBCs
• Blood thinners reduce the clotting ability
• Blood temperature is 38°C
• Blood pH is around 7.4, with a range of 7.35-7.45
• Blood constitutes 8% of total body weight
• Blood volume in males is 5 to 6 litres, and 4 to 5 litres in females

Blood composition

• Blood consists of 55% plasma and 45% formed elements like RBCs, WBCs and platelets
• Haematocrit measures red blood cell volume, with normal values at 47% ± 5% for males and 42% ± 5% for females

Blood plasma

• Blood plasma is over 90% water
• Proteins form 7% of plasma. They're produced in the liver and don't leave blood vessels
• Albumin maintains osmotic pressure and transports substances, globulins are alpha, beta, and gamma types, and fibrinogen is part of blood clotting
• Electrolytes, nutrients, hormones, gases, and waste products make up 2% of plasma

Blood cells

• Red blood cells are erythrocytes
• White blood cells are leukocytes including granular and agranular ones
• Granular leukocytes contains small granules:
  • Eosinophils stain orange-red
  • Basophils stain dark blue
  • Neutrophils remain pale lilac
• Agranular leukocytes no granules:
  • Lymphocytes include T cells, B cells and natural killer cells
  • Monocytes are phagocytic cells that transform into macrophages
• Platelets are thrombocytes, cell fragments from megakaryocytes in bone marrow
• Mnemonic to remember leukocytes(most to least abundant): Never Let Monkeys Eat Bananas

Red Blood Cells

• RBCs contain haemoglobin which is an oxygen-carrying protein
• Hemoglobin equals 1/3 of an erythrocyte's weight
• Biconcave shape increases the surface area/volume ratio and allows flexibility in capillaries
• RBCs lack a nucleus/organelles, energy production is limited
• Normal RBC count equals 5.4 x 1012/L for males and 4.8 x 1012/L for females as 2 million new enter into circulation per second
• Cell descriptions are based on the normal RBC's appearance, described as follows:
  • Normocytic is normal size, from 7-8μm
  • Normochromic is normal red coloured Changes to RBCs in anemia:
  • Macrocytic are larger sized
  • Microcytic are smaller sized
  • Hypochromic are decreased red colour
  • Hyperchromic are a deeper hue of red

Platelet physiology

• Platelets are disc-shaped cell fragments without a nucleus,from 2-4 mm in size
• Platelet plugs can block blood loss in small vessels, but their effectiveness is less apparent in larger vessels
• Normal platelet count is 150-400 x 109/L
• Platelets are responsible in haemostasis or the stopping of bleeding which consists of:
  • Vascular spasm of the damaged blood vessel
  • Platelet plug formation where platelets activate when contacting the damaged tissue and release chemical mediators to speed up other platelets
  • Blood clotting also known as coagulation through arrangement in a meshwork
• Platelets don't normally stick to the blood vessels' lining, but damage to the endothelium exposes collagen so platelets stick to it
• The glycoprotein von Willebrand factor stabilises platelet adhesion and activates them
• Activated platelets attract more and further aggregation from chemical signals called (ADP, serotonin & thromboxane A2) which promote vasoconstriction

Blood clotting

• Needed are Ca2+, clotting proteins as clotting factors 1-13 and substances released by platelets from the liver
• Clotting is a cascade reactions in which each clotting factor activates the next in a fixed sequence resulting in fibrin meshwork formation
• Clotting cascade can be activated :
  • By extrinsic pathways during tissue trauma from thromboplastin known as mix of cell membrane phospholipids
  • Or by the intrinsic pathways: platelets contacting with endothelium damaged through atherosclerosis or plastic surface, platelet activation is a crucial event
• Both pathways yield prothrombin activator(2) and converge where it's converted into thrombin
• Thrombin cuts protein called fibrinogen creating small strands of fibrin. They binds together to form the meshwork, becoming the blood clot
• Fibrin stabilising factor (XIII) reinforces the clot
• If it occurs without any bleeding it's a thrombosis which can occur everywhere in arteries or veins

Haematopoiesis

• Haematopoiesis is the making of RBC's
• In adults occurs in in bone marrow of flat bones: sternum, ribs, skull & pelvis and ends of long bones like humerus and femur and in lymphoid organs
• It depends on stem cells that are the same for all formed elements
• They are pleuripotent haemocytoblast cells:
  • Around 100 billion are made a day,(~28g)
  • At 2 million per second
  • Only live for around 120 days
• Most all need to be continually replaced, and can die in hours/days/weeks
• Reticulocytes mature in the bloodstream in 1-2 days, as an indicator of level of erythropoiesis

Erythrocyte production regulation

• Production requires iron to store in the liver, spleen and bone marrow as well as division DNA, B12, & folic acid
• Influenced by tissue hypoxia, high altitudes reduce oxygen intake and is a key factor
• Also anemia and problems reduced delivery of blood in the circulatory system
• The kidney will respond by releasing erythropoietin(EPO), speeding up production of new RBC

RBC oxygen

• A Hemoglobin is a protein that has 2 main molecules. The subunits are known as globin and haeme
• It can be denoted at "Hb."
• The globin is a protein with 4 polypeptides. Normally Alpha/Beta and there's 2 of each
• Haeme is coloured and will attach to each polypeptide chain
  • Will need Fe2 to combine reversibly with 1x Oxygen molecule
  • After oxygen is bound becomes oxyhaemoglobin
• A red blood cell has 25 x 10^6Hb per cell
• Each hemoglobin can carry 4 oxygen molecules attached to iron from the lungs to tissue cells
• Around 98.5% of oxygen comes from oxyhaemoglobin
• Almost all will be arterial with a 99% saturation
• Transports 23% of C02 for elimination
• C02 combines reversibly combining with aminos to form carbaminohaemoglobin

RBC destruction

• RBC’s don’t have nucleus , so they have limited repair and ability
• After 120 days, they are captured and engulfed in spleen, liver, and bone marrow
• Macrophages engulf and cause hemolysis.
  • So hemoglobin is broken into haeme and globin
  • Globin is recycled for aminos while the Fe recycled for RBCs. The haeme turns to bilirubin

Blood Groups

• Karl Landsteiner discovered why some blood transfusions in 1900 worked after observing agglutination of blood samples
• Blood groups are named A, B, and the renamed C to O which also relates to "Ohne" to suggest "without"
• This states that it has no surface antigens
• They bond with antibodies also know as an ANTIbody GENerator (ANTIbody GENerator)."
• All these can be minor types, including ABO, Rhesus, Duffy and MNS with the total almost over 300.
• Mismatched ABo and Rhesus ones leads to "vigorous transfusion reactions
• This means they are particular interests

Antigens

• ABO blood types have specific antigens. Can be A or B
• Will be coded by gene for antigens and can be be inherited as well
• Genes encode an enzymes as Glycosltransferase
• Its will adds sugarr molecules to the the surface
• Genotypes include AO/AA BO/BB AA/AB
• Blood A/B antigen. complex carbohydrates/ known as glycoproteins
• has a protein back bone. with attached sugars for blood-type

Patterns of blood types

• A/B are codominance: meaning when present together it show
• In an AB both A&B exist and show
• Incomplete dominance means A/B are dominant over the O allele
• O does not have anti gens

Agglutination

• If you possess A/B and all
• You ill create that antigen as army
• The are rh+ which is created by and D factor

Rhesus factor

• • Positive is common, it means have have the containing antigens
• AntiRH antibodies show with expsosre

Haemolytic disease of newborn

• HDN is with both
• If rh- mom get rht with child it will produce anti D
• NEUTRAL is the stop sensataion
• if it occurs during pregnany
• all blood D anit body come form 200 donores