CIRCULATORY SYSTEMPart 1

Grade 8 Semester 1

Year 2011-2012

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

Blood Content

Types of Blood CellsCell Type Appearanc

eFunction Structure

Red blood Cells(erythrocytes)

Transport O2 from lungs

Contain haemoglobinHave no nucleusCells are smalls and flexible

White Blood Cells(Phagocytes)

Remove microorganisms that invade the body and might cause infection by engulfing them.

Irregular shaped nucleusEnzymes in cytoplasm digest microorganisms once engulfedSensitive cell surface membrane

White Blood Cells(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

Blood Clotting

Plateletplug

Collagen fibers

Platelet releases chemicalsthat make nearby platelets sticky

Clotting factors from:PlateletsDamaged cellsPlasma (factors include calcium, vitamin K)

Prothrombin Thrombin

Fibrinogen Fibrin5 µm

Fibrin clotRed blood cell

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.

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

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

Transverse Section of Vessels

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

Narrow central tube (lumen)

Wide central tube (lumen)

Capillaries

At the arterial end of acapillary, blood pressure is

greater than osmotic pressure,and fluid flows out of the

capillary into the interstitial fluid.

Capillary Redbloodcell

15 m

Tissue cell INTERSTITIAL FLUID

Capillary

Net fluidmovement out

Net fluidmovement in

Direction of blood flow

Blood pressure

Osmotic pressure

Inward flow

Outward flow

Pre

ssur

e

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.

The mammalian cardiovascular system

Pulmonary vein

Right atrium

Right ventricle

Posteriorvena cava Capillaries of

abdominal organsand hind limbs

Aorta

Left ventricle

Left atriumPulmonary vein

Pulmonaryartery

Capillariesof left lung

Capillaries ofhead and forelimbs

Anteriorvena cava

Pulmonaryartery

Capillariesof right lung

Aorta

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