Presentation on theme: "Chpt. 27: Heart and Blood Vessels (The Circulatory System)"— Presentation transcript:
1 Chpt. 27: Heart and Blood Vessels (The Circulatory System)
2 Circulatory SystemsCirculatory system : provides cells in organisms with all the materials they require.Unicellular organisms have no need for a circulatory system. In these diffusion is sufficient for transport of materials.Two types of circulatory system:- Open circulatory system: blood is not always enclosed in blood vessels e.g. Crayfish- Closed circulatory system: blood remains enclosed in blood vessels e.g. Humans
3 Circulatory Systems Closed Circulatory System More efficient than an open system because:There is a faster transport of O2 and nutrients.It maintains sufficient blood pressure for larger organs.
4 Circulatory Systems 3. The Heart 1. Blood 2. Blood Vessels Components of the closed circulatory system of humans:3. The Heart1. Blood2. Blood Vessels
6 Blood Vessels Arteries: carry blood Away from the heart. - divide into smaller vessels called arterioles.Veins: carry blood to the heart.- small veins are called venules.Capillaries: are tiny vessels that link arteries and veins.
7 Arteries and VeinsArteries and veins have three similar walls in their layers:- outer layer of rough – inelastic protein (collagen)- middle layer of muscle and elastic fibres.- Endothelium – inner single layer of living cells.
12 Capillaries thin walled blood vessels allow exchange of materials between blood and body tissuehave no valvescarry oxygenated and deoxygenated bloodallow diffusion of dissolved substances e.g. Gases, wastes etc.have no pulse
17 The Heartthe heart is located between the two lungs and just above the diaphragmit is under involuntary controlmade of cardiac musclesurrounded by a membrane called the pericardium which prevents friction with nearby organs
18 Structure of the Heartdivided into two sides by a wall called the septumfour chambers:two upper chambers - atriatwo lower chambers - ventriclesLeft atriumRight AtriumLeft VentricleRight VentriclePumps blood to the lungsPumps blood to the head and body
19 Structure of the heart Valves - prevent the backflow of blood - held in place by tendons- tendons held to walls of heart via papillary muscles- Tricuspid valve – has three flaps located on right hand side of heart- Bicuspid valve – has two flaps located on left hand side of heart- Semilunar valves – allow blood to flow out of heart into two main arteries
20 The heart has four major blood vessels AortaPulmonary ArteryPulmonary VeinVena CavaThe heart has four major blood vessels
21 Blood flow through the heart Deoxygenated Blood enters right atrium from the superior vena cava and the inferior vena cavaRight atrium contracts forcing blood down through the tricuspid valves into the right ventricleRight ventricle contracts forcing blood out of the heart to the lungs through the semilunar valve in the pulmonary artery.
22 Blood flow through the heart Oxygentated Blood returning to the heart from the lungs enters the left atrium via the pulmonary veinsIt is pumped through the bicuspid valves to the left ventricleThe left ventricle contracts pumping blood out to the body through the semilunar valve in the aorta.LORD: Left Oxygenated Right Deoxygenated
24 Double CirculationDouble Circulation: refers to the fact that the blood passes through the heart at least twice before reaching the same point.Double circulation humans:Two sides of the heart are separated by the septum.Septum necessary to separate deoxygenated and oxygenated bloodThis separation is an important part of the two – circuit circulatory system in humans:- pulmonary circuit- systemic circuit
26 Double CirculationPulmonary Circuit:right ventricle pumps blood around the pulmonary circuit.in pulmonary circuit blood is pumped from heart to lungs back to heart.blood is oxygenated and loses carbon dioxide in the lungs.
27 Double Circulation Systemic Circuit: left ventricle pumps blood around the systemic circuit.in systemic circuit oxygenated blood is pumped to the head, arms, trunk and legs.
28 Double Vs Single Circulation Double Circulation:allows oxygen-rich and oxygen-poor blood to be kept separate.ensures blood pressure is high enough to reach all parts of the body.Single Circulation:Blood is pumped from the heart around the body and back to the heart again in a single circuit e.g. Earthworms, fish.can only produce low blood pressure around most of the body.
30 Portal SystemPortal System: is a blood pathway that begins and ends in capillaries.Vessels in portal system do not connect directly to the heart.Example of a portal system:Hepatic Portal Vein: connects the stomach and intestines to the liver.
31 Blood Supply to the Heart Coronary (cardiac) arteries: supply blood to the muscle of the heart.Coronary (cardiac) veins: drain blood from the muscle of the heart.Blockage of the coronary arteries is a cause of heart attacks and warning chest pains prior to this are commonly known as angina.
32 Control of Heartbeat (Higher Level Only) Heartbeat can occur independently of the brain.Pacemaker (Sino-atrial node/SA)- is a small bundle of specialised tissueresponsible for controlling heartbeat- located in the wall at the top of right atrium- pacemaker sends out regular electrical impulses causing atria to contract and subsequently ventriclesBrain can control the frequency of these impulses(brain - nerves and hormones)
33 Control of Heartbeat – Detail: Atrial Systole – pacemaker pulses causing atria to contract.Electrical impulse from pacemaker stimulates the atrio-ventricular (AV) node.(AV node similar to pacemaker located furtherdown in right atrium)AV node sends impulse down special muscle fibres located in septum.Ventricular Systole – this impulse is passed out to the walls of the ventricles by thin fibres. The impulses from these fibres cause the ventricles to contract.
35 Some important points: Electrocardiogram (ECG) – uses electrodes placed onthe chest to measure electrical activity of the heart.Factors that increase the rate of heartbeat:- exercise- temperature- emotions- shockFactors that decrease the rate of heartbeat:- relaxation- sleep- alcohol
36 Stages of Heartbeat – Cardiac Cycle (Higher Level only)Stages of heartbeat refer to the events which occurduring one heartbeat.*Diastole – is when heart chambers relax*Systole – is when heart chambers contract
37 Stages of Heartbeat – Cardiac Cycle Stage 1 - Atrial Diastole:- diastole – the atria and ventricles are both relaxed- all valves are closed as blood enters atriaStage 2 – Atrial Systole:- systole – electrical impulses from pacemaker cause atria to contract- this causes blood to be pumped to ventricles- Tricuspid & bicuspid valves open,venae cavae & pulmonary veins close,semi – lunar valves remain closed.
38 Stage 3 – Ventricular Systole: - Ventricular Systole – atria relax and electrical impulses from AV node cause ventricles to contract- this forces blood out of heart into pulmonary artery and aorta- the pressure forces open semi lunar valves and closes tricuspid and bicuspid valves – ‘lub’ sound- ventricles relax again, semi lunar valves close preventing backflow and causing ‘dub’ sound- venae cavae and pulmonary veins open and cycle starts again
39 Sounds of HeartbeatThe double sound (‘lub-dub’ sound) of the heartbeat is caused by valves being forced shut.‘Lub’ – low pitched, quieter, long lasting, due to the bicuspid and tricuspid valves being forced shut when the ventricles contract.‘Dub’ – higher pitched, louder, shorter, due to the semilunar valves snapping shut.Heart Murmur: is any abnormal sound associated with heartbeat and may indicate damage to one or more valves.
40 Pulse and Blood Pressure The Pulse: is a wave of vibrations through the arteries following the expansion of the aorta.Pulse can be felt easily in the wrist and neck.Pulse rate indicates the rate of heartbeat.Average adult pulse rate is 72 beats per minute.
41 Pulse and Blood Pressure Blood pressure: is the force exerted by the blood against the walls of the blood vessels (mainly the arteries).blood pressure is recorded by measuring the pressure needed to stop the flow of blood in the arteries of the upper arm.normal blood pressure – 120/80 mm mercury.Upper value – Systolic PressureLower value – Diastolic PressureHigh blood pressure occurs when lower value is over 95 mm of mercury. It indicates the heart has to pump harder to get enough blood around the body which can lead to heart attacks if not treated.
42 Lifestyle and the Heart Effects of Smoking:Nicotine increases the heart rate and raises blood pressure.Carbon Monoxide reduces the ability of the blood to carry oxygen.chemicals in smoke increase the risk of blood clots.Effects of Diet:Diet may affect the heart in three ways:A fat rich diet increases the chance of the arteries becoming blocked - heart attacks, strokes.Too much salt raises blood pressure.Being severely overweight increases blood pressure and results in heart attacks.
43 Lifestyle and the Heart Effects of Exercise:enlarges and strengthens the heart.improves blood circulation.causes loss of weight.
44 What else effects Heart Rate? CaffeineCigarettesDrugsStressFever / illness
45 Steps to a Healthy Heart Avoid fatty foods/ cholesterolWatch your blood pressureAvoid StressReduce Salt IntakeDo 30 minutes exercise