3-blood And Blood Cells

Question 1

What is the function of blood?

Answer 1

Connective tissue
•Transport (connects every part of body)
•Heat distribution
•Immunity
•Haemostasis
•MAINTAIN HOMEOSTASIS (constant internal environment)
•Blood volume (5l male; 3.5l female)

Question 2

Describe erythropoiesis

Answer 2

Produced in bone marrow from precursors which produce haemoglobin then lose organelles
Erythropoietin causes stem cell to turn into erythrocytes
•Immature erythrocytes contain ribosomes: reticulocytes.
•High circulating reticulocytes diagnostic (e.g. anaemia, chemotherapy)
•Removed through reticulo-endothelial system (phagocytic macrophages in spleen)
•Lifespan = 120 days (short, no nuclei; 1% or 250 billion cells per day)
•Dependent on dietary iron (meat, egg yolk, nuts), iron deficiency causes anaemia

Question 3

Describe haemoglobin

Answer 3

4 subunits: each a polypeptide with a haem group
•Haem contains Ferrous iron (Fe2+)
•Each Fe2+ binds one O2 molecule
•Oxidized form (methaemoglobin – Fe3+) cannot carry O2
•Different form in foetus with higher O2 affinity
•100ml blood: 15.8g (male)
13.7g (female)

Question 4

Describe o2 binding to Hb

Answer 4

Haemoglobin low affinity for oxygen due to conformational shape of globin molecules
• Oxygen binding beaks conformation and opens up structure
• Second oxygen molecule binds more easily and so on
• This is cooperative binding
• Allows more oxygen to be carried

Question 5

What are the 3 types of anaemia?

Answer 5

Microcytic (small MCV): Failure of haemoglobin synthesis
Fe deficiency: menstruation (daily loss 1mg M; 2mg F)
GIT lesions or cancers
parasitic infection

Normocytic (normal MCV)
Acute blood loss

Macrocytic (large MCV)
DNA synthesis and cell division fail and reduced division of progenitor cells so fewer but larger erythrocytes.
Folic acid (required for thymine synthesis) deficiency : pregnancy
Vit B12 (needed for folic acids actions) deficiency: autoimmune disease, destroys B12 uptake in gut: pernicious anaemia; vegetarians, vegans

Question 6

What are the leukocyte types

Answer 6

Polymorphonuclear granulocytes:
   Multilobed nuclei, many granules                        neutrophils (phagocytic, abundant)
           eosinophils (allergy)
           basophils (produce histamine)
•Lymphocytes (antibody producing)
•Monocytes (phagocytic)

Question 7

Describe platelets

Answer 7

Derive from megakaryocytes
• 2 - 3 µm diameter (small)
• Normal platelet count 25 x 104/ml
• Life span 8 - 10 days
• Granules
• Many organelles, no nucleus

Question 8

How are platelets involved in haemostasis

Answer 8

Express surface receptors for platelet activators (e.g. collagen in vessels or thrombin from coagulation cascade)
•Adhesion to exposed collagen in wound or atherosclerosis
•Release of granules promotes platelet aggregation
•Platelets produce thromboxane A2 from cycloxygenase enzyme
•Aspirin inhibits cycloxygenase and is anti-platelet
•Involved in clot or thrombus formation
•The vascular endothelium produces e.g. prostacyclin and nitric oxide which inhibit platelet activation