Lecture notes
Lecture notes Year 1 MBChB: Introduction to Medical Sciences (IMS)
Concise lecture notes from the blood strand of the IMS module taught in the first year of the MBChB course at the University of Leeds!
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BLOODINTRODUCTION TO BLOOD
Blood
Viscous fluid pumped around the body by the heart and the vascular system
Contains RBC’s, white cells (immunology), platelets (anucleate; clotting)
Contains plasma (liquid fraction; clotting and complement systems)
Blood is not involved in paracrine signalling
Circulatory system
Arteries: heart to organs and tissues (generally oxygenated)
Veins: returns blood from the organs and tissues to the heart, followed by the lungs for re-oxygenation (generally
de-oxygenated)
Pulmonary artery – deoxygenated blood to lungs to be oxygenated
Pulmonary vein – oxygenated blood from lungs to heart to be pumped around body
Arterioles, venules, capillaries: small blood vessels which have a small diameter and therefore maximise blood-
tissue interaction
The heart
The human heart consists of 2 atria and 2 ventricles and pumps around 5 L blood per
minute
De-oxygenated blood in vena cava into the right atrium right ventricle pumps
blood into pulmonary artery reoxygenation in lungs pulmonary vein left
atrium left ventricle aorta
Valves prevent “backflow”
Functions of the blood
Hydration of tissues and organs
Delivery of oxygen to tissues and organs
Provision of nutrients to tissues and organs
To fight infection: Innate and adaptive immune responses
Regulation of body temperature and pH
Distribution of (endocrine) hormones
To prevent its own (blood) loss
, Oxygen delivery RBC’s contain haemoglobin which is regulates oxygen transport
Fight infection White blood cells contribute to the immune response against infection (all white cells) and to
allergic reactions (eosinophils and basophils)
In the blood plasma, the complement system is activated to fight infection by pathogens
Hormone Endocrine hormones are secreted by specific endocrine glands into the blood to be circulated to
distribution remote target tissues.
Insulin (beta cells in pancreas)
Thyroid stimulating hormone (anterior pituitary lobe)
Oestrogen, progesterone, testosterone (ovary/testes)
Vasopressin (posterior pituitary lobe)
Adrenaline (adrenal medulla)
Preventing blood Platelets – small anucleate blood cells that clump together
loss Blood Coagulation Pathway – Through the formation of thrombin a fibrin clot is formed
Blood cells
Blood cells are derived from one progenitor cell in the bone marrow: the multipotential haematopoietic stem cell
Two major lineages: myeloid (other types of blood cells) and lymphoid (lymphocytes and natural killer cell)
These two lineages produce 11 different types of blood cell
Blood plasma
55% of the blood volume is plasma (liquid fraction of the blood)
Most abundant blood plasma proteins are:
1. Albumin (35-50 g/L), “filler”
2. Immunoglobulins (15 g/L), involved in fighting infection
3. Fibrinogen (3-5 g/L), involved in clotting
Serum and plasma
Serum = Plasma – Clotting Factors (blood is allowed to clot before it is centrifuged)
Plasma = Serum + Clotting Factors (+ clotting inhibitor)
45% of blood volume is taken up by blood cells
Blood incompatibility
If blood of incompatible blood groups are mixed, antibodies react with antigens on the red blood cell (RBC)
membrane, causing haemolysis (RBC rupture)
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