transport - secondary two science website€¦ · the cell is in direct contact with the external...

transport

in humans

learningOBJECTIVES

At the end of the lesson, you should be able to:

- Humans

• Explain the need for a transport system in multi-

cellular organisms

• Identify the parts of the human circulatory system

and their respective functions

o Identify 4 heart chambers

o Identify 3 main blood vessels and explain their

functions

o Identify and explain function of blood components

• State how diffusion facilitates the transport of

substances in animals (e.g. diffusion of digested

food molecules and oxygen from blood to tissues)

funFACT

It would take about

1,200,000 mosquito bites

to completely drain the

average human of blood.

(Discover magazine,

August 2007)

whyTRANSPORT?

If you stay within 500 m – 1 km of the school,

you probably would not mind walking to school…

whyTRANSPORT?

whyTRANSPORT?

BUT if you stayed at Bedok, Woodlands, or even Boon

Lay…

You would probably take a form of public transport.

(or go to a school within walking distance…)

WHY?

whyTRANSPORT?

whyTRANSPORT?

Likewise, in unicellular organisms,

The cell is in direct contact with the external

environment.

Diffusion alone is enough to:

- transport essential materials such as oxygen

and nutrients to the cell

- remove waste such as carbon dioxide rapidly

whyTRANSPORT?

In multicellular (complex) organisms,

Cells are far from the external environment.

Diffusion alone is too slow to:

- transport essential materials such as food to

the various organs

- remove waste products efficiently

whyTRANSPORT?

Thus, a transport system is developed to move these

substances eg. Blood system in humans

This will ensure

- a continual supply of nutrients, oxygen and other

useful materials for metabolism

- the removal of toxic waste products produced by

metabolism

whyTRANSPORT?

circulatorySYSTEM

heart

blood

vessels

blood

The human circulatory

system consists of three

parts:

• heart (pumps blood

around the body)

• blood (liquid which

carries materials)

• blood vessels (tubes

which carry blood around

the body)

theHEART

right atrium

left atrium

right ventricle

left ventricle

theHEART

theHEART

• pumps blood around the body

• all mammals have hearts that are

similar in structure

• human heart is about the size of our

fists

• made up of cardiac muscles

• comprises 4 chambers 2 upper chambers called atria

(left and right) 2 lower chambers called

ventricles (left and right)

theHEART

• right side of heart pumps blood to

lungs only (which are a short

distance from the heart)

• left side of heart pumps blood

around the body (which are further

away from the heart)

• hence left ventricle has thicker

muscular walls than the right

ventricle

theHEART

Oxygenated blood

from the lungs enter

the left atrium and

flow into the left

ventricle

The blood is then

pumped from the

left ventricle out of

the heart to the rest of the body

De-oxygenated

blood from the body enters the right atrium

and then into the

right ventricle

This blood passes

from the right ventricle then out into

the lungs

Left atrium

Left ventricle

Right atrium

Right ventricle

theHEART

Oxygenated blood

from the lungs enter

the left atrium and

flow into the left

ventricle

The blood is then

pumped from the

left ventricle out of

the heart to the rest

of the body

De-oxygenated

blood from the body

enters the right

atrium and then into

the right ventricle

This blood passes

from the right

ventricle then out

into the lungs

Left atrium

Left ventricle

Right atrium

Right ventricle

bloodCIRCULATION

• In mammals, blood flows through the heart

twice in one complete circuit. This is known as

double circulation.

bloodCIRCULATION

From the heart to the lungs and

back to the heart,

• In the lungs, the blood collects

oxygen and releases carbon

dioxide.

• Blood that returns to the heart

is now rich in oxygen, called

oxygenated blood.

bloodCIRCULATION

From the heart to the rest of the

body and back to the heart,

• As blood passes the small

intestine, it collects digested

food.

• The blood supplies all the cells

of the body with this digested

food together with oxygen

picked up in the lungs.

• After oxygen is deposited in

body tissues, the blood now has

little oxygen, called

deoxygenated blood.

circulatorySYSTEM

heart

blood

vessels

blood



parts:

• heart (pumps blood

around the body)

• blood (liquid which

carries materials)

• blood vessels (tubes

which carry blood around

the body)

bloodCOMPONENTS

BLOOD

plasma red blood cells white blood cells platelets

BLOOD

Has two main functions:

To carry materials round the body. These

materials include nutrients, oxygen, carbon

dioxide and other waste substances.

To protect us against diseases.

bloodCOMPONENTS

BLOOD

plasma red blood cells (erythrocytes)

white blood cells (leukocytes)

Platelets

(thrombocytes)

PLASMA

•Pale yellowish liquid

•Contains mainly water (90%)

•Contains mainly dissolved substances like nutrients (digested food), hormones,

antibodies and waste products (carbon

dioxide and urea).

bloodCOMPONENTS

BLOOD



Platelets

(thrombocytes)

•Contains haemoglobin

gives RBC red colour when

combined with oxygen; or

purplish colour when

combined with carbon dioxide

combines reversibly with

oxygen so RBC can transport

oxygen around the body

bloodCOMPONENTS

BLOOD



Platelets

(thrombocytes)

•Does not contain nuclei

More space to contain

haemoglobin for oxygen

transport

bloodCOMPONENTS

BLOOD



Platelets

(thrombocytes)

WHITE BLOOD CELLS

bloodCOMPONENTS

BLOOD



Platelets

(thrombocytes)

WHITE BLOOD CELLS

•Much bigger in size than RBC

•Fewer in number than RBC

•Colourless (no haemoglobin)

•Contains a nucleus

bloodCOMPONENTS

BLOOD



Platelets

(thrombocytes)

WHITE BLOOD CELLS

•Two types:

Phagocytes Ingests foreign

particles by phagocytosis

Lymphocytes Produces antibodies

that neutralise bacteria and viruses

bloodCOMPONENTS

BLOOD



Platelets (thrombocytes)

PLATELETS

•Cell fragments (not complete cells)

•No nucleus

•Involved in the process of blood clotting



parts:

• blood

• heart

• blood vessels

circulatorySYSTEM

heart

blood

vessels

blood

• The blood vessels are a network of tubes to carry

blood around the body.

• Namely the artery, vein & capillary

bloodVESSELS

Artery Vein Capillary

Thick muscular wall

to withstand high

pressure in artery.

Elasticity allows

artery wall to stretch

and recoil to push

the blood in spurts

along the artery.

Thin muscular wall

as blood moves

more slowly and

smoothly in the vein

at low pressure.

One-cell thick wall

to allow rapid

diffusion to take

place between the

blood and

surrounding tissues.

(Note: Capillary wall

is one-cell thick;

capillary is NOT

one-cell thick)


Valves are absent. Valves are present

to prevent backflow

of blood.

Valves are absent.


Small lumen Larger lumen Small lumen

(thinnest wall)


Always transports

blood away from

heart to the rest of

the body.

Transports mainly

oxygenated blood

(except pulmonary

artery and umbilical

artery).

Always transports

blood from body

towards the heart.

Transports mainly

deoxygenated blood

(except pulmonary

vein and umbilical

vein).

Always carry blood

from small arteries

(arterioles) to small

veins (venules).

Allow exchange of

materials between

blood and body

tissues via diffusion.

bloodVESSELS - summary


Structure Thick, elastic,

muscular walls

Thinner, less

elastic, less

muscular walls

One-cell thick

endothelium

Functions Transports

blood away

from the heart

Transports

blood towards

the heart

Transports

nutrients &

waste

materials

Blood

Pressure

High blood

pressure from

heart

Lowest blood

pressure

Low blood

pressure

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