Blood Flashcards
what is blood
Blood is a connective tissue that circulates constantly around the body, allowing constant communication between tissues distant from each other. It transports the following components;
- oxygen
- nutrients
- heat
- hormones
- protective substances, e.g. WBCs
- clotting factors, e.g. platelets
Components of blood
Blood is composed of a clear, straw-coloured, watery fluid called blood plasma. Several cells are suspended within this making up the following;
- 55%plasma
- 45% blood cells & platelets
- 1% wbcs and platelets
Blood makes up around 7% of an adult’s body weight, more in children 8-9% , and even more in infants; 9-10% (the percentage decreasing until adulthood is reached).
Blood and heat conversion/loss & transportation
The heat produced by metabolically active organs such as the liver and working muscuoskeletal muscles is distributed around the body via the bloodstream which contributes to the maintenance of core body temperature (CBT).
Homeostasis and blood;
- When too hot
- heat loss is allowed by vasodilation of blood vessels from the skin to the external environment
- When too cold
- heat conservation is allowed by vasoconstriction which helps to prevent heat loss from the skin to the external environment
Blood Plasma
The components of blood plasma are 90-92% water and dissolved substances are the rest;
- plasma protiens, e.g.
- inorganic salts
- nutrients, mainly from digested foods
- waste materials, e.g. CO2, urea, etc.
- hormones, which travel to their target organs/cells via the blood
- gases, e.g. O2 & CO2
Plasma protiens
these make up about 7% of plasma and are normally retained within the blood because they are too big to escape through capillary pores and into the tissues.
These are largely responsible for creating osmotic pressure of blood.
If levels of plasma proteins fall, due to either reduced production or loss from the blood vessels (e.g. within a bleed), osmotic pressure will also reduce and and fluid will move into the tissues (oedema) and body cavities.
Examples;
Albumin
- the smallest of plasma proteins but largest in quantity.
- they maintain colloid pressure of the blood; maintaining water within the blood and (ECF)
- deficiency of these results in oedema (excess ECF due to leaked ICF)
- helps to transport substances; drugs, hormones, fatty acids
Globulins;
- three types; alpha, beta, gamma, smallest to largest respectively
- gamma; antibodies
- alpha; carry fats to cells for energy metabolism
- beta; transport fat to cells for steroid and cell membrane synthesis
Fibrinogen
- an important soluble plasma clotting factor which is converted to fibrin to help in the clotting action to prevent further bleeding
Waste products found in blood
Urea
creatinine (left over from energy-producing actions in the body)
uric acid
CO2
Cellular content of blood
Erythrocytes (rbcs)
Thrombocytes (platelets; not a cell, fragments of cells)
Leukocytes (wbcs)
Blood cells are synthesised mainly in the red bone marrow, whilst some lymphocytes (wbcs) are produced by the lymphoid tissue.
The name of the process of blood cells
haematopoiesis
Red Blood Cells
- 99% of blood cells are RBCs, (erythrocytes).
- biconcave discs & no nucleus gives a large surface area
- no nucleus means they cannot divide and therefore need to be continually replaced
- lifespan of 120 days
- 30 trillion RBCs in average human body, 25% of total blood cell count
- development of RBCs is 7days; erythropoiesis
- vitamin B12 & folic acid are required for synthesis of RBCs
RBCs & haemoglobin
haemoglobin is a protein with an iron-containing protein which gives blood its red pigment. each Hb molecule has 4 binding sites which allows 4 O2 molecules to attach (forming oxyhemoglobin), allowing O2 to be transported around the body via the blood. - this binding is known as ‘saturated’ and is a reversible process.
An average RBC carries 280million Hb molecules; over 1billion O2 molecules transported.
Hypoxia
This term relates to inadequate tissue perfusion (not enough O2 supplying the tissues). Tissues are constantly in need of O2 and constantly producing CO2.
Hypoxemia (low O2 circulating in the blood) can cause hyoxia (low O2 in the tissues).
Platelets (thrombocytes)
these are very small fragments of cells. they lack a nucleus and their cytoplasm is packed with granules containing a variety of substances that promote blood clotting. this causes haemostasis (cessation of bleeding).
lifespan of platelets is between 8-11 days and those not used for clotting are destroyed by macrophages (wbcs) in the spleen.
about a third of platelets are stored in the spleen 9as oppose to circulation) and these act as emergency storage for excessive bleeding.
Haemostasis (3 stages)
Coagulation (clotting) can start as quickly as 15 seconds after injury (depending in severity of bleed/damaged blood vessel);
1- vasoconstriction; platelets become sticky, adhere to damaged blood vessel wall, release serotonin to constrict vessel and therefore reduce more blood passing and leaking out
2- platelet plug formation; platelets clump together forming a plug to the bleed, release ADP to attract other platelets, this is usually complete with 6 minutes- positive feedback mechanism.
3- coagulation; blood clotting.
heat distribution
the blood can carry and transfer heat and excessive heat, away from organs that are metabolically active, e..g the liver, to prevent the organ from over-heating and distribute this excess heat around the body, maintaining warmth throughout the body to other less metabolically-active organs and maintain the organ/liver’s functionality.
what is an anti-coagulant and what would it do to blood (composition) ?
if blood was taken as a sample and treated wth an anti-coagulant (substances like blood thinners that prevent clots; opposite of blood clotting agents), it would separate into two layers;
- upper layer; plasma fluid (55% of blood sample)
- lower layer; suspended cellular components (overall 45%, in-depth; 99% rbcs & 1% wbcs and platelets).
