Blood Vascular System
 Made up of 4 Parts:
Blood – a fluid connective tissue that transports oxygen and nutrients
around the body and collects waste products produced by the tissues
2.
The Heart – a hollow, muscular, four-chambered organ responsible for
pumping blood around the body
3.
The Circulatory System – a network of arteries, veins, and capillaries
in which the blood flows around the body
4.
They Lymphatic System – a network of lymphatic vessels that
transports lymph or excess tissue fluid around the body and is
responsible for returning it to the circulation
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Consists of several types of cell suspending in a liquid medium called
Plasma.
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It makes up for 7% of the total body weight and has a pH of about 7.4
1.
Blood Functions:
Transport
 Gases in solution – blood carries oxygenated blood from the
lungs and delivers the oxygen to the tissues where it used. It then
collects deoxygenated blood containing carbon dioxide produced
by the tissues during their metabolic processes, and carries it
back to the lungs, where the carbon dioxide is exchanged for
oxygen in the inspired air.
 Nutrients – blood transports nutrients, e.g. amino acids, fatty
acids and glucose, which result from the process of digestion,
from the digestive system to the liver and to the tissues where
they are needed.
 Waste Products – blood collects the waste products resulting
from metabolism in the tissues and transports them to the
kidney and liver where they are excreted from the body.
 Hormones and Enzymes – blood transports enzymes and
hormones from the endocrine glands to their target tissues
Blood Functions:
Regulation
Blood plays a vital role in homeostasis by regulating:
 Volume and constituents of the body fluids – blood carries water in the form of
plasma to the tissues and is responsible for maintaining the osmotic balance of
the fluids and the cells. The presence of plasma proteins, particularly albumin
in the blood, controls the flow of fluid between the fluid compartments and is
responsible for maintaining blood volume and blood pressure.
 Body Temperature – blood conducts heat around the body to the body surface
where if necessary it is lost by peripheral vasodilation.
 Acid-base balance – blood maintains a constant internal pH in the body by the
presence of buffers, e.g. bicarbonate, which are able o absorb H+ ions when the
blood is acid and give out H+ ions when the blood is alkaline. In his way, all he
processes of the body are able to function effectively.
 Defense against infection – blood helps to prevent infection through the action of
the white blood cells, which are part of the body’s immune system. It also carries
antibodies and antitoxins produced by the immune system around the body.
 Blood Clotting – the clotting mechanism prevents excessive blood loss from
wounds and other injuries and prevents the entry of infection.
Blood Functions:
Problems with Oedema
 Oedema is an abnormal accumulation of fluid in the
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cavities and intercellular spaces of the body.
When oedematous fluid accumulates in the peritoneal
cavity it is described as ascites.
Oedema occurs when there is an imbalance between
osmotic pressure and hydrostatic pressure.
It can be caused by a number of factors, e.g. anything that
increases osmotic pressure outside the blood vessels, such
as inflammation , or reduces osmotic pressure in the blood,
such as hypoproteinaemia.
Increased hydrostatic pressure inside blood vessels
resulting from heart failure may also cause oedema.
Composition of Blood
 Blood is a red fluid that is carried by the blood vessels
of the circulatory system.
 It is composed of a fluid part, the plasma, and a solid
part, the blood cells.
 Plasma forms part of extracellular fluid.
 Each constituent of the blood plays a specific part in
the overall function of blood.
Composition of Blood:
Plasma
 Plasma is the liquid part of the blood that separates
out when a blood sample is spun in a centrifuge
 The main constituent is water (about 90%) in which
are a number of dissolved substances being
transported from one part of the body to another
 These include carbon dioxide in solution, nutrients
such as amino acids, glucose and fatty acids, waste
materials such as urea, hormones, enzymes, antibodies
and antigens.
Composition of Blood:
Plasma Contents
Plasma contains:
 Mineral Salts – the main mineral salts found in extracellular fluid are sodium and chloride, but
potassium, calcium, magnesium, and bicarbonate are also present. The functions of these
mineral salts include maintaining osmotic balance and maintaining pH by acting as buffers.
Calcium has a number of essential roles in the body, e.g. in blood clotting, muscle contraction
and nerve function.
 Plasma Proteins – these help to maintain the osmotic pressure of the blood because they are
too large to pass out of the circulation. This has the effect of retaining fluid in the blood by
osmosis, i.e. it prevents too much water from ‘leaking’ out into the extracellular spaces. If this
did occur then the volume of the blood would decrease and the blood pressure would fall with
serious consequences. The most important Proteins are:
 Albumin: helps to maintain the osmotic concentration of blood, i.e. holds the water in the
blood
 Fibrinogen and Prothrombin: involved in the clotting mechanism of the blood
 Immunoglobulin's: these are the antibodies produced by the immune system of the body
Albumin, Fibrinogen and Prothrombin are produced by the liver, but the immunoglobulin’s
are produced by the cells of the immune system
Composition of Blood:
Blood Cells
 The blood cells make up the solid component of blood and can be
divided into three types:
 Erythrocytes – the red blood cells
 Leucocytes – the white blood cells
 Thrombocytes – the platelets, which are cell fragments
 Terms to understand:
 Haemopoiesis – the formation of all types of blood cell
 Erythropoiesis – the formation of red blood cells or erythrocytes
 Lymphoid tissue – found in the lymph nodes and spleen and produces
agranular leucocytes, i.e. lymphocytes and monocytes
 Myeloid tissue – found in the red bone marrow and responsible for the
formation of erythrocytes and granular leucocytes, i.e. neutrophils
eosinophils and basophils
 Serum – plasma minus the clotting factors fibrinogen and
Prothrombin. It can be obtained by allowing a blood sample to clot
naturally.
Composition of Blood:
Erythrocytes (Red blood cells)
 Erythrocytes are the most numerous blood cell – there
are about 6-8 million per cubic millitre of blood.
 Their function is to transport oxygen and a small
proportion of carbon dioxide around the body (most
carbon dioxide is carried in solution in the plasma).
 Mature erythrocytes are biconcave circular discs about
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