Circulation and Gas Exchange Intermediate 2 Biology Unit 3 ANIMAL PHYSIOLOGY

Learning Objectives Circulation Describe the structure of the heart in relation to its function as a muscular pump. (to include the four chambers, valves, wall thickness and blood supply) State that the heart receives its blood supply from the coronary artery and describe what affect a blockage in this artery would have.

The Heart The function of the heart is to pump blood round the body. 3

The Heart The heart consists of four chambers. – Atria – two upper chambers – Ventricles – two lower chambers

The Heart Right atrium Left atrium Left ventricle Cardiac muscle Right ventricle

The Heart The ventricles pump the blood – Left Ventricle Round the body – Right ventricle To the lungs The atria receive blood valves in the heart prevent the backflow of blood 6

The heart semi-lunar valve atrio-ventricular valve atrio-ventricular valve

The Heart Vena cava Pulmonary artery Aorta Pulmonary vein

The Heart All blood must pass through the heart twice in each circulation. Deoxygenated blood from the body enters the heart through the vena cava into the right atrium. Complete the stages of circulation until the blood is back in the vena cava again. Complete the stages of circulation until the blood is back in the vena cava again.

The Heart Deoxygenated blood passes through the right AV valve into the right ventricle. Right ventricle contracts and blood is pumped into the pulmonary arteries through the semi-lunar valve In the lungs the blood loses its carbon dioxide and gains fresh oxygen before entering the pulmonary veins.

The Heart This oxygenated blood now returns to the heart and enters the left atrium. Oxygenated blood moves through the left AV valve into the left ventricle. The left ventricle then pumps the blood through the SL valve into the aorta which takes it around the body.

The Heart The wall of the left ventricle is very thick since it has to pump blood all round the body. The wall of the right ventricle is less thick since it pumps blood only to the lungs.

The Heart The heart wall is made of cardiac muscle and also requires its own blood supply. The blood vessels which do this are called the coronary arteries.

Coronary Arteries Coronary artery

Coronary arteries Coronary arteries supply oxygen and glucose to the cardiac muscle Coronary veins return the blood to the vena cava. If the coronary arteries narrow or become blocked in any way, this can result in angina, a heart attack or in severe cases heart failure.

Learning Objectives Circulation Circulation Describe the path of blood flow through the heart and its associated vessels. Describe the functions of arteries, capillaries and veins; give structural adaptations of these blood vessels in relation to their function.

Blood Vessels There are three main types of blood vessel – arteries, veins and capillaries. Arteries carry blood away from the heart. Veins carry blood back to the heart. Capillaries connect arteries to veins and this is where the exchange of essential materials takes place.

Arteries Arteries have thick muscular walls. This allows them to withstand the pressure created by the heart.

Arteries Pulse – Each time the heart beats, blood is forced along the arteries 19

Veins Veins have thinner walls than arteries but a wider cavity. This is because the blood is now at a much lower pressure.

Veins Veins contain valves – prevent the backflow of blood.

Capillaries Capillaries are microscopic blood vessels

Capillaries Walls are only one cell thick. – allows for the exchange of materials between the blood and body cells – Examples - glucose, oxygen, carbon dioxide

Learning Objectives Circulation Circulation Give the names and positions of; pulmonary artery and vein, aorta and vena cava, hepatic artery, hepatic vein, mesenteric artery, hepatic portal vein, renal artery and renal vein.

Colour in the key and the diagram using – Blue deoxygenated blood – Red Oxygenated blood

Circulatory System Pulmonary artery Pulmonary vein Aorta Hepatic artery Mesenteric artery Hepatic vein Hepatic portal vein Renal artery Renal vein Vena cava

Pulmonary artery Pulmonary vein Aorta Hepatic artery Mesenteric artery Hepatic vein Hepatic portal vein Renal artery Renal vein Vena cava

In Summary – the bare minimum Blood leaves heart in arteries, flows through capillaries and returns to heart in veins The pulse indicates that blood is pumped through arteries; Structural adaptations of arteries, veins and capillaries related to function. The heart obtains its blood supply from the coronary arteries.

Learning Objectives Gas Exchange Gas Exchange Describe the internal structure of the lungs (to include trachea, bronchi, bronchioles, and alveoli). Describe the features of the alveoli which allow efficient gas exchange Describe the role of diffusion in the exchange of oxygen and carbon dioxide. Describe the features of the capillary network which allow efficient gas exchange in tissues.

Gas Exchange Gas exchange occurs in the lungs. Stages – Inhalation – Gas Exchange oxygen from the air passes from the lungs into the blood and carbon dioxide passes from the blood into the lungs. – Exhalation

Structure of the Lungs Air passes down the – trachea (windpipe) which splits into 2 bronchi – Bronchi split into smaller tubes called bronchioles. – bronchioles terminate in tiny air sacs called alveoli. The trachea and bronchi are kept open by rings of cartilage – The cartilage stops the airways from collapsing when the pressure changes

Alveoli Bronchiole Alveolus Blood Capillary

Gas Exchange Alveoli provide a large surface area for the gas exchange The lining of each alveolus – very thin – Moist – Surrounded by a capillary network

Gas Exchange Blood arriving in the lungs from the body is deoxygenated. Oxygen diffuses through the thin lining of the alveolus into the blood capillary – Diffusion takes place because the concentration of oxygen in the alveolus is higher than the oxygen concentration in the blood.

Gas exchange Carbon dioxide diffuses in the opposite direction. – the concentration of CO 2 in the blood from the body is higher than the concentration of CO 2 in the alveoli. The blood now leaving the lungs is oxygenated.

Features which make gas exchange more efficient. FeatureFunction Thin liningTo allow rapid diffusion Lining moist Allows oxygen to dissolve Large surface areaTo absorb oxygen Dense network of capillaries To absorb and transport oxygen