Topic 6.2 The Transport System

What is the Circulatory System?

• Circulatory System is a system of internal transport that transports:

(i) Oxygen and Carbon dioxide(ii) Nutrients to body cells(iii) Waste products to specific sites for disposal.

Basic Mammal Blood Flow

Closed Circulatory System

What is an open circulatory system?

How do simple organisms circulate?

Open CirculationSimple Diffusion

6.2 (U1) Arteries convey blood at high pressure from the ventricles to the tissues of the body.

• Arteries are one of three types of blood vessels. They carry oxygen rich blood away from the heart to the tissues of the body.

• The lumen is the opening in a blood vessel through which the blood flows. The lumen in arteries is narrow to help maintain blood pressure.

• Arteries receive blood from the ventricles, very thick muscular chambers in the heart.

6.2 (U1) Arteries convey blood at high pressure from the ventricles to the tissues of the body.

• The artery walls contain elastic tissues and smooth muscles which allow them to stretch and contract in response to increased blood volume. The contractions propel blood through the arteries.

• The walls of the arteries are designed to withstand the fluctuating pressure without bulging (aneurysm) or rupturing.

• Arteries supply blood to each organ in the body.

6.2 (U2) Arteries have muscle and elastic fibres in their walls

• Arteries are very thick walled blood vessels. They have a strong outer covering called the tunica externa (adventitia) which is made of collagen and elastic fibres (connective tissue). This allows the walls of the arteries to expand in response to pressure created by blood flow.

• The middle layer, tunica media consists of smooth muscle and elastic tissue composed of the protein elastin which allow the arteries to help pump the blood through the body.

• The inner layer of the arteries is known as the tunica intima and it is composed of an elastic membrane lining and smooth tissues covered by elastic tissues.

6.2 (U3) The muscle and elastic fibres assist in maintaining blood pressure between pump cycles.

• Blood pressure is measured when the ventricles contract and relax.

• Pressure is highest (systolic pressure) when the ventricles contract and push blood into the arteries.

• Pressure is lowest (diastolic pressure) when the ventricles relax and fill with blood.

• When the lumen stretches and the walls of the artery push outward there is potential energy stored. Pressure decreases at the end of the heartbeat and the arteries squeeze propelling blood forward.

6.2 (U3) The muscle and elastic fibres assist in maintaining blood pressure between pump cycles.

• Blood vessels will experience vasoconstriction (lumen decreases) and vasodilation (lumen increases) when the circular muscles in the wall contract and relax.

• These processes increase and decrease blood flow and blood pressure. It controls blood flow through smaller branching arteries known as arterioles.

6.2 (U4) Blood flows through tissues in capillaries with permeable walls that allow exchange of materials between

cells in the tissue and the blood in the capillary

• Capillaries are the smallest and thinnest (10 μm) blood vessels. They are designed this way to allow them to fit into tiny spaces and so that exchange of materials between the blood and all body cells can be efficient.

• They are composed of one thin layer of endothelium cells with spaces between the cells and are coated in a protein gel.

• Blood plasma (liquid portion of blood) can leak out through spaces and form tissue fluid which provides an exchange medium for gases and nutrients.

• The permeability of the capillary walls are different depending on the surrounding tissues and what particles it needs to be permeable to. Capillaries also have the ability to adapt to new roles over time in response to the needs of the tissues.

6.1 (U5) Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.

• Veins carry blood towards the heart and into the atria.

• Pressure is much lower/walls are thinner.

• Less muscle and elastic fibres so they can dilate more.

• At rest 80% of blood volume is in veins

• Blood flow assisted by muscle contractions and gravity.

• Veins are found all over the body and like arteries serve each organ.

Major Arteries & Veins

6.2 U6 Valves in veins and the heart ensure circulation of blood by preventing backflow

http://www.youtube.com/watch?v=HNuPWdfjDoc

Take notes on animation

Valves in the heart work in a similar manner…pressure inside the chambers causes the valves to close

6.2 (S1) Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.

• Complete handout given in class

6.2 (U7) There is a separate circulation for the lungs.

• Two main pathways:• Pulmonary includes the right side of the

heart and to & from the lungs. Blood is pumped under low pressure, is deoxygenated on the way to the lungs and oxygenated on the way back to the heart.

• Systemic includes the left side of the heart and to & from all other organs & tissues. Blood is under higher pressure, oxygenated on the way out and deoxygenated on the way back.

• Valves in the heart and veins ensure blood flows in one direction only (arteries to capillaries to veins).

6.2 (S2) Recognition of the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure.

Chambers in the Human Heart• Right Atrium• Left Atrium• Right Ventricle • Left Ventricle• Atria collect blood

from veins and pass it to the ventricles.

• Ventricles collect blood from the atria and pump it to the arteries.

Valves in the Human Heart• Atrioventricular

(tricuspid) Valve • Pulmonary Valve

• Atrioventricular (bicuspid) Valve

• Aortic Valve

Blood Vessels of the Human Heart• Inferior Vena Cava• Superior Vena Cava• Pulmonary Vein

• Pulmonary Artery• Aorta

Coronary Arteries

• The coronary arteries branch off the aorta, the largest artery in the human body.

• Coronary arteries branch out and into the muscle tissue of the heart and they supply the heart with much needed oxygen and nutrients.