Transcript The Circulatory System

Chpt. 27: Heart and Blood Vessels
(The Circulatory System)
Circulatory Systems
Circulatory 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
Circulatory Systems
Closed Circulatory System
More efficient than an open system because:
1. There is a faster transport of O2 and nutrients.
1. It maintains sufficient blood pressure for larger
organs.
Circulatory Systems
Components of the closed circulatory system of
humans:
3. The Heart
1. Blood
2. Blood
Vessels
Blood Vessels
Arteries
Capillaries
Veins
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.
Arteries and Veins
Arteries 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.
Arteries and Veins
Arteries
• blood is under high pressure
• have thick walls and a small lumen
• have no valves
• carry mostly oxygenated blood
• blood flows in pulses
Veins
• blood is under low pressure
• have thin walls and large lumens
• have valves to prevent back flow of blood
• carry mostly deoxygenated blood
• blood flows smoothly i.e. no pulse
Veins
Capillaries
• thin walled blood vessels
• allow exchange of materials between blood and body
tissue
• have no valves
• carry oxygenated and deoxygenated blood
• allow diffusion of dissolved substances e.g. Gases,
wastes etc.
• have no pulse
Capillaries
Differences in Blood Vessels
Arteries
Veins
Capillaries
Thick walls
Thin walls
One cell thick
High Pressure
Low Pressure
Low Pressure
Away from
heart
No valves
To heart
Valves
Link arteries to
veins
No valves
Fast flow
Slower flow
V. Slow flow
The Heart
The Heart
• the heart is located between the two lungs and just
above the diaphragm
• it is under involuntary control
• made of cardiac muscle
• surrounded by a membrane called the pericardium
which prevents friction with nearby organs
Structure of the Heart
• divided into two sides by a wall called the septum
• four chambers:
two upper chambers - atria
Left atrium
Right Atrium
two lower chambers - ventricles
Left Ventricle
Right Ventricle
Pumps blood to the
head and body
Pumps blood to
the lungs
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
Pulmonary
Artery
Aorta
The heart has four
major blood vessels
Blood flow through the heart
• Deoxygenated Blood enters right atrium from the
superior vena cava and the inferior vena cava
• Right atrium contracts forcing blood down through the
tricuspid valves into the right ventricle
• Right ventricle contracts forcing blood out of the heart to
the lungs through the semilunar valve in the pulmonary
artery.
Blood flow through the heart
• Oxygentated Blood returning to the heart from the
lungs enters the left atrium via the pulmonary veins
• It is pumped through the bicuspid valves to the left
ventricle
• The left ventricle contracts pumping blood out to the
body through the semilunar valve in the aorta.
LORD: Left Oxygenated Right Deoxygenated
Double Circulation
Double 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 blood
• This separation is an important part of the two – circuit
circulatory system in humans:
- pulmonary circuit
- systemic circuit
Double Circulation
Pulmonary 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.
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.
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.
Portal System
Portal 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.
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.
Control of Heartbeat
(Higher Level Only)
• Heartbeat can occur independently of the brain.
• Pacemaker (Sino-atrial node/SA)
- is a small bundle of specialised tissue
responsible 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 ventricles
• Brain can control the frequency of these impulses
(brain - nerves and hormones)
Control of Heartbeat – Detail:
1. Atrial Systole – pacemaker pulses causing atria
to contract.
1. Electrical impulse from pacemaker stimulates
the atrio-ventricular (AV) node.
(AV node similar to pacemaker located further
down in right atrium)
3. AV node sends impulse down special muscle
fibres located in septum.
4. 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.
Some important points:
• Electrocardiogram (ECG) – uses electrodes placed on
the chest to measure electrical activity of the heart.
• Factors that increase the rate of heartbeat:
- exercise
- temperature
- emotions
- shock
• Factors that decrease the rate of heartbeat:
- relaxation
- sleep
- alcohol
Stages of Heartbeat – Cardiac Cycle
(Higher Level only)
• Stages of heartbeat refer to the events which occur
during one heartbeat.
• *Diastole – is when heart chambers relax
• *Systole – is when heart chambers contract
Stages of Heartbeat – Cardiac Cycle
Stage 1 - Atrial Diastole:
- diastole – the atria and ventricles are both relaxed
- all valves are closed as blood enters atria
Stage 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.
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
Sounds of Heartbeat
• The 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.
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.
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 Pressure
Lower value – Diastolic Pressure
• High 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.
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:
1. A fat rich diet increases the chance of the arteries
becoming blocked - heart attacks, strokes.
2. Too much salt raises blood pressure.
3. Being severely overweight increases blood pressure
and results in heart attacks.
Lifestyle and the Heart
Effects of Exercise:
• enlarges and strengthens the heart.
• improves blood circulation.
• causes loss of weight.
What else effects Heart Rate?
•Caffeine
•Cigarettes
•Drugs
•Stress
•Fever / illness
Steps to a Healthy Heart
•Avoid fatty foods/ cholesterol
•Watch your blood pressure
•Avoid Stress
•Reduce Salt Intake
•Do 30 minutes exercise