Biologyf5 09 Blood Circulatory System

8/3/2019 Biologyf5 09 Blood Circulatory System

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1.2 The Circulatory System

The circulatory system:-

(a) Delivers nutrients and oxygen to

cells(b) Carries waste products away from

the cells

(c) Protects the body from infections


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The Circulatory System has three

major components:-

The blood

The heart

Blood vessels- arteries, capillariesand veins


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Blood and Haemolymph

Blood is the medium of transport in

humans and animals

In many invertebrates such as theinsects, the medium of transport is

called the haemolymph

Haemolymph is a blood-like nutritive

fluid which fills the entire body cavity

(haemocoel) and surrounds all cells


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The Functions ofBlood

Transportation, regulation and protection

Blood transports:-

(a) Oxygen from the lungs to the cells of the

whole body, and carbon dioxide from the

cells to the lungs

(b) Nutrients, hormones and antibodies

throughout the body(c) Waste products away from the cells to

the organs of the excretory system


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The Functions ofBlood in

Regulation

Blood regulates:-

(a) The pH of body fluids

(b) The body temperature(c) The water content of cells


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The Function of Blood in protection

The blood protects us

(a) From excessive blood loss in aninjury through the mechanism ofblood clotting. It helps to healwounds

(b) From diseases and helps to fight

against infections, for example,white blood cells carry outphagocytosis


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The Functions of Haemolymph

Transports water, inorganic salts

and organic compounds throughout

the hoemocoel

Unlike blood, haemolymph does not

transport respiratory gases

In insects, respiratory gases are

transported via the tracheal system


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The Composition of Human Blood

Human blood is made up of 55% plasmaand 45% cellular components

Plasma is the main transport medium in the

bodyPlasma contains water, ions (sodium,potassium, magnesium, calcium, chlorideand bicarbonate), plasma proteins

(albumin, fibrinogen and immunoglobulins),hormones and dissolved substances(nutrients and wastes)


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Cellular Components

Red blood cells or erythrocytes

White blood cells (leucocytes)

Platelets


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Erythrocytes (red blood cells)

Shaped like a biconcave disc

Does not have a nucleus

Has an elastic membrane which enables it tosqueeze easily into the tiniest blood capillaries

A single erythrocyte contains about 250 millionmolecules ofhaemoglobin

Haemoglobin is an oxygen-carrying proteinpigment that gives the erythrocyte its red colour

Haemoglobin contains a haem group.The haem group contains an iron atom and is siteof oxygen binding


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Picture shows the red blood cells

and some leucocytes and

platelets


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Drawing shows the types of blood

cells in the human blood


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Another drawing that shows the

types of human blood cells


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Erythrocyte: Characteristics

The normal lifespan of an erythrocyte is

about 120 days, after which it is destroyed

in the liver and spleen

Erythrocytes are continuouslymanufactured in the bone marrow of long

bones, the ribs, the skull and vertebrae

As erythrocytes mature, they lose their

nuclei and mitochondria, giving them the

distinctive biconcave-disc shape


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Leucocytes

Colourless and have nuclei and mitochondria

Irregularin shape

Make up less than 1% of the volume of blood

Made by the stem cells in the bone marrowTheir collective function is to fight infections invarious ways

Most activities of leucocytes take place in theinterstitial fluid outside the blood vessel


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Leucocytes: Classes

Classified either as granular or agranular

Granulocytes:-

(a) Have granular cytoplasm and lobed nuclei

(b) Neutrophils- phagocytic granulocytes thatengulf and digest bacteria and dead cells

(c) Eosinophils- release enzymes to combatinflammation in allergic reactions; also killparasitic worms

(d) Basophils- involved in combating inflammatoryand allergic reactions, secrete heparin toprevent blood from clotting


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Types ofLeucocytes:

Agranulocytes

Have clear cytoplasm and their

nuclei are not lobed

Lymphocytes- produce the immuneresponse against foreign

substances

Monocytes- engulf and digest

bacteria and dead cells


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Human Blood Vessels

Three types of human blood vessels:arteries, veins and capillaries

Walls of arteries and veins consist of

epithelial tissues surrounded by smoothmuscles and connective tissues

The thick, muscular and elastic walls of thearteries enable them to withstand the high

pressure of blood flowing through themThe aorta is the main artery leaving theheart


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The Pulmonary Artery and Vein

The pulmonary artery is the only

artery that carries deoxygenated

blood from heart to the lungs

The pulmonary vein is the only vein

that carries oxygenated blood from

the lungs to the heart


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Arterioles and capillaries

Arterioles are smaller arteries that branchinto a network of capillaries which reachinto the tissues

Capillaries are tiny, thin-walled bloodvessels

Respiratory gases, nutrients, wasteproducts and hormones are exchanged by

diffusion between the blood and theinterstitial fluid surrounding the cells acrossthe thin walls of the capillaries


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Revision Exercise 1 (10 mins)

Explain the importance of thehuman blood circulatory system.

There are different compositions in

the human blood. Explain thefunction of the cellular component

of the human blood.

The Human Immunodeficiency Virus

(HIV) attacks the human body

defense system. An HIV patient lacks

the T-cells, which is a type of

lymphocyte. Explain the effects of


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Revision Exercise 2 (10 mins)

Arteries have small lumen and a verythick, muscularized wall. Explain the

importance of this feature in the

blood circulatory system.A deep-vein thrombosis (DVT)

which is also known as the long-flight

syndrome occurs when a person sits

or stands for a long period. Explain

how this condition occurs by

referring to the human blood vessels

involved.

Biologyf5 09 Blood Circulatory System

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