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Blood (IMS)
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Introduction rot Medical Sciences TOPIC 3 - Blood
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Medic_Summaries (IMS) Topic 3Blood
Blood consists of:
- Red blood cells (RBCs)
- White blood cells (WBCs) (immunology, platelets, anucleate and clotting)
- Plasma (liquid fraction, clotting and complement systems)
There is ca. 5L of blood in an adult human.
Circulatory system: system that blood travels through
- Arteries: take blood, generally oxygenated, from the heart to the organs and tissues
- Veins: return blood, generally deoxygenated, from the organs and tissues to the heart
- Arterioles, venules and capillaries: small blood vessels in the organs/tissues that have
small diameters and therefore maximum blood-tissue interaction
Schematic circulatory system: arteries and veins
- Vena cava -> right atrium -> right ventricle -> pulmonary artery into lungs -> pulmonary
veins -> left atrium -> left ventricle -> aorta -> vital organs
- Pulmonary arteries and veins: opposite to other arteries and veins for oxygenation
The heart:
- Pumps ca. 5L of blood per minute (entire adult body’s worth of blood)
- Deoxygenated blood from tissues/organs is collected through VENA CAVA into right atrium
- Right ventricle pumps blood through pulmonary arteries to lungs
- Valves prevent ‘back-flow’:
- Tricuspid: right
- Bicuspid: left (aka MITRAL valve)
- After re-oxygenation, blood is collected through pulmonary veins into left atrium
- Left ventricle pumps blood, via aorta, back to tissues/organs
Functions of blood:
- Hydration of tissues/organs
- Delivery of oxygen to tissues/organs
- Provision of nutrients to tissues/organs
- Fight infection (innate/adaptive immune response)
- Regulation of body temperature
- Regulation of body pH
- Distribution of (endocrine) hormones
- Prevent its own loss (coagulation and clotting)
1 Adapted from Lectures at the University of Leeds Medical School
, Medic_Summaries (IMS) Topic 3
Oxygen delivery: most abundant blood cell (RBC/erythrocyte)
- RBCs contain haemoglobin
- Haemoglobin ‘carries’ oxygen
Fighting infection:
- WBCs contribute to immune response (EOSINOPHILS and BASOPHILS)
- WBCs: lymphocytes, monocytes, eosinophils, basophils, and neutrophils
- In blood plasma, complement system is activated to fight infection by pathogens
Hormone distribution:
- Endocrine hormones are secreted by specific endocrine glands into the blood
- Examples of endocrine hormones and respective endocrine glands:
- Insulin: beta cells in pancreas
- Thyroid stimulating hormone (TSH): anterior pituitary lobe
- Oestrogen, progesterone and testosterone: ovary/testes
- Vasopressin: posterior pituitary lobe
- Adrenaline: adrenal medulla
Paracrine: release hormone locally
Endocrine: release hormone into blood
Preventing blood loss:
- Platelets: very small anuclear blood cells that clump together
- Coagulation: through thrombin formation, a fibrin clot is formed (holds platelets together)
Multi-potential haematopoietic stem cells:
- All blood cells come from this one common progenitor cell in the bone marrow
- There are two major lineages:
- Myeloid
- Lymphoid
- Together these produce eleven different types of blood cell
Megakaryocytes: very large cells that make thrombocytes (platelets)
Erythrocytes: RBCs
Myeloblast: differentiate into all WBCs
Mast cells: found in connective tissue, releases histamine during allergic reaction
Monocytes: largest type of leukocyte, can differentiate into macrophage
T lymphocyte: recognition of antigens
B lymphocyte: production of antibodies
Blood plasma:
- Plasma is easy to separate from other cells by centrifugation
- Over half of blood volume is plasma (liquid fraction of blood = 55%)
- Blood volume taken by blood cells (red, white and platelets = 45%)
- Blood plasma contains many important components of coagulation and immune systems
- Most abundant blood plasma proteins are:
- Albumin (35-50g/L) - FILLER
- Immunoglobulins (15g/L) - FIGHTING INFECTION
- Fibrinogen (3-5g/L) - CLOTTING
- Blood serum is similar to plasma, only the blood is allowed to clot before it is centrifuged
2 Adapted from Lectures at the University of Leeds Medical School
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