Blood Flashcards
What is the average circulating volume of blood in the typical adult male?
5 litres
What is the distribution of blood in the typical adult male?
- 1 litre in lungs
- 3 litres in systemic venous circulation
- 1 litre in the heart and arterial circulation
What are the functions of blood?
- carriage of physiologically active compounds
- clotting
- defence
- carriage of gas
- thermoregulation
- maintenance of ECF pH
What physiologically active compounds are carried in the blood?
- hormones
- enzymes
- nutrients
What constituents of the blood facilitate clotting?
- prothrombin
- fibrinogen
What constituent of the blood is involved in defence?
Leukocytes
Explain the basic mechanisms of thermoregulation
- vasodilation when hot
- vasoconstriction when cold
What percentage of plasma is water?
95%
What is the function of plasma?
Used to circulate biologically active molecules and compounds
What can small changes in protein composition be indicative of?
Problems elsewhere
What three subcategories can plasma proteins be divided into?
- albumin
- globulins
- fibrinogen and other clotting factors
What is the function of albumin in the plasma?
- transports lipid and steroid hormones
- helps create colloid oncotic pressure
What is the function of globulins in the plasma?
- alpha/beta transport of lipids and fat-soluble vitamins
- gamma globulins are antibodies
What is oncotic pressure?
Pressure that can pull water from the interstitial space into the lumen
Plasma proteins do not readily cross the capillary wall, they ___
displace water and create and osmotic potential
What happens when water is moved from interstitial space into the lumen?
Chemicals and nutrients also move, however this only changes the volume, not the concentration
What is the function of RBCs?
Carry oxygen around the body using haemoglobin
Describe RBCs
- most abundant
- 120 day life span
- highly flexible
- bi-concave
- non-nucleated
What controls and accelerates Erythropoiesis?
Erythropoietin
Where is Erythropoietin mainly secreted?
By the peritubular capillary cells (85%) found in the kidneys and hepatocytes of the liver (15%)
What is the function of Erythropoietin?
Speeds up differentiation of pluripotent stem cells into erythroblasts
Secretion of Erythropoietin is increased when
oxygen supply to the kidneys is reduced
Give four factors which might cause reduced oxygen supply to the kidneys
- hypoxia
- haemorrhage
- anaemia
- lung disease
Name the five main types of white blood cells
- neutrophils
- eosinophils
- basophils
- monocytes
- lymphocytes
What percentage of WBC population are neutrophils?
68%
Give the functions of neutrophils
- half life of around 6 hours
- phagocytic and mainly deal with bacterial infection
- can trap bacteria in NETS
Give the functions of eosinophils
- attack pathogens too large for other leukocytes e.g. parasites
- number rapidly increases in allergic reactions
Give the functions of basophils
- release histamine and heparin
- promote inflammation
Give the functions of monocytes
- largest leukocyte
- 72 hour life span in circulation
- migrate to tissues and become macrophages (phagocytic)
Give the functions of lymphocytes
- key components of immune system
- T and B cell variants
What controls Leukopoiesis?
- growth stimulating factors
- interleukins
Where are growth stimulating factors and interleukins released?
By endothelial cells, fibroblasts and mature white cells
What do growth stimulating factors and interleukins stimulate?
Mitosis and maturation of leukocytes
Leukopoiesis is controlled by a cocktail of cytokines which is dynamic and
changes its composition to suit which specific cell type is needed and any given moment
Describe platelets
- unique membrane bound fragments of megakaryocytes
- formation governed by thrombopoietin
Give the functions of platelets
- adhere to damaged capillary walls and expose connective tissue to mediate blood clotting
- do not adhere to healthy epithelium
What is haematocrit?
The percentage of blood made up of red blood cells
What is the usual percentage of haematocrit in males and females respectively?
males - 40-54%
females - 37-47%
What might increase haematocrit?
Living at altitude due to the need for more haemoglobin to bind lower conc. of oxygen
What is blood viscosity?
The thickness of blood in comparison to water
- plasma is 1.8x thicker
- whole blood is 3-4x thicker
- can change with haematocrit, temperature and flow rate
