CIRCULATORY SYSTEMS IN ANIMALSBiology ATAR Unit2

Chapter 11

Pages 266-274

Heinemann Chapter 9, pages 150-152 (handout)

Gastrovascular cavityOpen circulatory system Tubular heart Ostia Open-ended vessels Interstitial fluidClosed circulatory system Heart Arteries Arterioles Capillaries Venules Veins Blood

Multicellular organisms need a circulatory system to deliver nutrients and O2 and remove waste products and CO2

Organisms have different types of systems because of their size, their environment and their activity or metabolic rate

Keywords Making connections

CIRCULATORY SYSTEMSTypes of structures1. Gastrovascular cavity2. Open system3. Closed systemFunction The circulatory system moves O2 from the respiratory

surface to the body tissues and removes CO2 from the body tissue to the respiratory surface.

It also transports nutrients, hormones and waste around the body where necessary.

GASTROVASCULAR CAVITY:CNIDARIANS

The gastrovascular cavity is responsible for both the digestion of food and the transport of nutrients throughout the body.

The cavity has only one opening to the environment. Food goes in and waste comes out that same opening.

OPEN CIRCULATORY SYSTEM:INSECTS An open circulatory system

consists of a dorsal tubular heart(s) that, when it contracts, forces the fluid out of open-ended blood vessels

This fluid flows through the spaces in the body and bathes the tissues and organs before returning through holes (ostia) to the heart.

The fluid moves at low pressures and slow circulation speeds

The fluid is not like blood, but like interstitial fluid

Example: insects, snails

OPEN CIRCULATORY SYSTEM:INSECTS

These body fluids contain nutrients which are obtained from the digestive system

They also contain metabolic wastes, which are disposed of by the excretory system.

The insect has a separate respiratory system to exchange gases (O2 and CO2).

In most insects, O2 is delivered directly to the muscles through the tracheal system.

CLOSED CIRCULATORY SYSTEMS:LARGE AQUATIC & TERRESTRIAL ORGANISMS

A closed circulatory system carries fluid within a network of arteries, capillaries and veins

The fluid (blood) has the capacity to deliver nutrients and O2 to cells and remove waste products and CO2 from cells

Blood does not leave the capillaries and does not come into direct contact with other body tissues

Blood is oxygenated as it flows through the lungs

Blood is moved through the system by a muscular heart

The heart has 3 or 4 chambers separated by valves

Example: reptiles, mammals, fish

CLOSED CIRCULATORY SYSTEMS

SUMMARY:OPEN & CLOSED CIRCULATORY SYSTEMS

OPEN CLOSED

Transport fluid

No specialised transport fluid (interstitial fluid)

Blood

Heart Simple one or two chambered heart

Three or four chambers with valves

Vessels Open-ended, of different lengths

Arteries, arterioles, capillaries, venules, veins

Pressure Very low pressures Arteries – high pressureVeins – low pressure

Time taken to circulate

Long circuit time Short circuit time

Examples Snails, arthropods Birds, fish, mammals