Intro to Blood Flashcards
What are the functions of blood ?
- transport
- regulation of pH, osmosis, body temp
- maintenance of homeostasis
Define Hematocrit
the ratio of the volume of red blood cells to the total volume of bold
(packed cell volume)
What are the main components of blood ?
- Plasma - 55%
- Erythrocytes - 45% (formed elements)
- Buffy coat = <1% ( formed elements)
What are the 3 major categories of plasma proteins ?
- albumins - smallest and most abundant
- globulins
- fibrinogen
Describe albumins
- most abundant - 3.5 - 5.0 g/dL blood
- contributes to viscosity & osmolarity
- influences blood pressure, flow and fluid balance
Describe Globulins
- antibodies
- 1.0 -1.5 g/dL blood
- provide immune system function
- alpha, beta and gamme globulins
Describe Fibrinogen
- 0.2-0.45 g/dL blood
- precursors of fibrin threads that help form blood clots
What are some functions of plasma proteins ?
- blood viscosity
- provide 1/6th of the total buffering power of the blood
- transport substances circulating in the blood
- essential for blood clotting mechanisms
What are some of the sub types of granulocytes ?
- neutrophils
- eosinophils
- basophils
What are the sub-types of granulocytes ?
- lymphocytes
- monocytes
What’s another word for platelets ?
thrombocytes
What is haematopoiesis stimulated by?
erythropoietin, thrombopoietin & colony-stimulating factors
How are erythrocytes formed ?
- haemotopoietic stem cells
- committed stem cells
- early erythroblast
- late erythroblast
- normoblast
- reticulocyte
- erythrocyte
Describe the structure of haemoglobin
- each Hb molecule consists of 4 protein chains (globins) and 4 heme groups
Describe heme groups
non-protein moeity that binds oxygen to ferrous ion (Fe2+) at its centre
Describe Globins
- 2 alpha & 2 beta chains
- 5% carbon dioxide in blood is bound to global moiety
What is the haemoglobin concentration of whole blood?
females = 12-16 g/dL
males = 13-18 g/dL
What is the red blood cell count in men and women?
men = 4.6-6.2 million/uL
women = 4.2-5.4 million/uL
Why are RBC counts lower in women ?
- androgens stimulate RBC production
- women have periodic menstrual loss
Define Erythropoiesis
production of red blood cells
Describe the negative feedback control involved in erythrocyte homeostasis
- drop in RBC count causes kidney hypoxemia
- kidney production of erythropoietin stimulates bone marrow
- RBC count increases in 3/4 days
What are some examples of stimuli which increases erythropoiesis ?
- low levels of oxygen (hypoxemia)
- high altitude
- increase in exercise
How long do blood cells circulate for ?
120 days
Where are expired erythrocytes broken down ?
- in the liver and spleen
- the freed haemoglobin is degraded into heme and globin
- cell fragments are phagocytised
What are some examples of erythrocyte disorders ?
- polycythemia = an excess of RBCs
- anaemia = deficiency of RBCs or Hb
What are the effects on anaemia?
- tissue hypoxia and necrosis
- low blood osmolarity
- low blood viscosity
Define antigen
substances that can induce an immune response
Define antibody
proteins that recognise and bind to antigens
What is the origin of antigens ?
within the body or externally
What is the origin of antibodies ?
within the body
What are neutrophils, eosinophils, basophils ?
Granulocytes
Describe Neutrophils
- polymorphonuclear leukocytes
- 60-70% of WBCs
- barely visible granules in cytoplasm
- 3-5 lobed nucleus
- phagocytosis of bacteria & release antimicrobial chemicals
Describe Eosinophils
- 2-4% of WBCs
- large rosy-orange granules
- bi-lobed nucleus
- phagocytosis of antigen-antibody complexes, allergens and release enzymes to destroy parasites
Describe Basophils
- <1% WBCs
- large, abundant, violet granules
- large S-shaped nucleus
- secrete histamine & heparin
Define granules
contain enzymes and other chemicals employed in defence against pathogens
Describe Lymphocytes
- 25-33%
- variable amounts of bluish cytoplasm
- ovoid/round
- uniform dark violet nucleus
Describe monocytes
- 3-8%
- largest WBC
- Ovoid, kidney/horseshoe shaped nucleus
What are the properties of white blood cells ?
phagocytosis, diapedesis, ameboid motion, chemotaxis
What are the 4 key features of acute inflammation ?
- redness
- heat
- swelling
- pain
Describe platelets
- colourless
- 2-4 um diameter
- no nucleus
- life span = 8-12 days
What are the functions of platelets ?
- secrete vasoconstricors to help reduce blood loss
- initiate formation of clot-dissolving enzyme
- chemically attract neutrophils & monocytes to sites of inflammation
- phagocytise and destroy bacteria
What are some mechanisms to prevent blood loss ?
- formation of platelet plug
- formation of blood clot
- clot retraction
- growth of fibrous tissue
How are Platelet Plugs formed ?
- damaged blood vessels
- chemicals released from platelets
- inhibitors
Define coagulation
- last & most effective defence against bleeding
- conversion of plasma protein fibrinogen into insoluble fibrin threads to from a framework clot
What are substances that promote coagulation called ?
procoagulants
What are substances that inhibit coagulation called ?
anticoagulants
Where procoagulants produced ?
in the liver
Describe the process of coagulation
- procoagulants activate 1 factor and it will activate the next to form a reaction cascade
What are the 2 coagulation pathways ?
extrinsic & intrinsic
Describe the extrinsic pathway
- initiated by release of tissue thromboplastin (factor III) from damaged tissue
- cascade to factor VII, V & X (fewer steps)
- calcium required
Describe the intrinsic pathway
- initiated by platelets releasing Hageman factor (factors XII)
- Cascade to factor XI -> IX -> VIII -> X
- calcium required
What processes prevent inappropriate clotting?
- platelet repulsion
- thrombin dilution
- natural anticoagulants
- blood clot dissolution
Describe platelet repulsion
- platelets don’t adhere to prostacyclin-coating
Describe natural anticoagulants
- heparine (from basophils & mast cells) interferes with formation of prothrombin activators
- antithrombin (from liver) deactivates thrombin before it can act on fibrinogen
Describe Blood Clot Dissolution
- fibrinolysis = dissolution of a clot
- factor XII speeds up the formation of kallikrein enzyme
- kallikrein converts plasminogen into plasmin, a fibrin-dissolving enzyme that breaks up the clot
