1. Part 1 Grade 8 Semester 1 Year 2011-2012
Circulatory System
Part 1
Grade 8 Semester 1
Year

2. Blood as the Transport Medium
To supply oxygen and glucose, as well as other substances, large organisms have a specialised transport system.
This system has 4 parts:
A medium-blood
A system of tubes-arteries and veins
A pump-heart
Sites of exchange-capillaries

3. Blood Content

4. Types of Blood Cells Cell Type Appearance Function Structure
Red blood Cells
(erythrocytes)
Transport O2 from lungs
Contain haemoglobin
Have no nucleus
Cells are smalls and flexible
White Blood Cells
(Phagocytes)
Remove microorganisms that invade the body and might cause infection by engulfing them.
Irregular shaped nucleus
Enzymes in cytoplasm digest microorganisms once engulfed
Sensitive cell surface membrane
(Lymphocytes)
Produce antibodies-as defense against diseases
Large nucleus contains may copies of genes for antibody production
Platelets
Involved in blood clotting
Can release blood clotting enzyme

5. Blood Clotting
Platelet plug
Collagen fibers
Platelet releases chemicals that make nearby platelets sticky
Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K)
Prothrombin
Thrombin
Fibrinogen
Fibrin
5 µm
Fibrin clot
Red blood cell

6. Blood Plasma
Our transport medium has watery liquid part that is called plasma.
Plasma has transport function which carries dissolved food molecules, waste materials, and hormones.
Plasma is also able to distribute heat around the various part of the body.

7. The Heart It is a double pump
It contracts (systole) and relaxes (diastole)
It has 4 chambers
Each chamber pumps the same volume of blood
Heart rate/pulse: 72 beats/min

8. Blood Vessels
The blood flows away from the heart in vessels called arteries.
The blood flows back towards the heart in vessels called veins.
Joining the arteries and veins are the capillaries.
Main artery: aorta
Main veins: vena cava

9. Transverse Section of Vessels
Narrow central tube (lumen)
Wide central tube (lumen)
Artery: Blood is rich in oxygen (except in the pulmonary artery); High pressure.
Vein: Blood is low in oxygen (except in the pulmonary vein); Low pressure; has pocket valve.
Capillary: One cell thick; large surface area

10. Arterial end of capillary
Capillaries
At the arterial end of a
capillary, blood pressure is
greater than osmotic pressure,
and fluid flows out of the
capillary into the interstitial fluid.
Capillary
Red
blood
cell
15 m
Tissue cell
INTERSTITIAL FLUID
Net fluid
movement out
movement in
Direction of
blood flow
Blood pressure
Osmotic pressure
Inward flow
Outward flow
Pressure
Arterial end of capillary
Venule end
At the venule end of a capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary.

11. The mammalian cardiovascular system
Pulmonary
vein
Right atrium
Right ventricle
Posterior
vena cava
Capillaries of
abdominal organs
and hind limbs
Aorta
Left ventricle
Left atrium
artery
Capillaries
of left lung
head and
forelimbs
Anterior
of right lung 1 10 11 5 4 6 2 9 3 7 8