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Heart and Blood Vessels
Miss Rochford
Fifth Year Biology
In this Topic
• Open & closed circulatory systems
• Human circulatory system
• Heart dissection
• Cardiac cycle
• Effect of smoking, diet
and exercise
Open & Closed Circulatory Systems
Open Circulatory System
• Blood flows out of its vessels and surrounds tissue cells
• Blood returns to the heart via pores in the heart called ostia
• There are no veins
Open Circulatory System
Organisms with open circulatory systems:
Spiders Insects Worms Beetles
Closed Circulatory System
• Blood flows continuously in a network of totally enclosed vessels
• Blood does not leave the blood vessels
• An adaptation to an increase in body size
• All vertebrates and some invertebrates have closed circulatory systems
Closed Circulatory System
Characteristics of a closed circulatory system:
• Oxygen delivered to tissues without blood leaving the vessels
• Allows for longer periods of activity because: Faster delivery of oxygen and nutrients Faster removal of wastes
• Body can control what areas receive blood E.g. Increase blood flow to muscles
HUMAN CIRCULATORY SYSTEM
Human Circulatory System
Made of 3 components:
1. Blood Vessels
2. Blood (Chapter 25)
3. Heart
Blood vessels
3 main types of blood vessels:
1. Arteries
2. Veins
3. Capillaries
Blood vessels
Arteries
• Carry blood away from the heart
(A for Artery = Away from heart)
• Strong blood flow
• High pressure of blood in arteries
• Thick strong walls to protect from pressure
Veins
• Carry blood to the heart
• Low blood pressure
• Thin, weak walls
• Have valves to stop blood going backwards
Arteries and Veins
• Both have 3 similar layers in their walls
• Veins have a thinner middle layer
Arteries and Veins
Collagen layer: • Tough and inelastic • Prevents over-expansion of the walls
Muscle & elastic fibre: • Muscle is involuntary • Elastic fibres keep the shape
Endothelium:
• Surrounds the lumen
Capillaries
• Tiny blood vessels
• Found between arteries and veins
• Very thin walls
– Allows materials to pass in and out
RED BLOOD CELLS
THIN CELL WALL
BODY CELLS
useful substances
waste products
Summary of blood vessels
Blood vessel Function
Arteries
Veins
Capillaries
Carry blood away from the heart
Carry blood to the heart
Allow materials to pass in and out of the blood
The Heart and Blood
Circulation
The Heart: the central organ
Function of Heart Pump blood around the body
The Heart: the central organ
Cardiac muscle:
• Special type of involuntary muscle
• Slow to fatigue
• Contractile tissue (capable of shortening)
Function of Heart Pump blood around the body
Made of: Cardiac muscle
The Heart: the central organ
Function of Heart Pump blood around the body
Made of: Cardiac muscle
Surrounded by: Double membrane called the pericardium
Pericardium fluid:
• Layer between the pericardium double membrane
• Reduces friction when the heart beats
carbon dioxide
oxygen
Oxygen is needed for respiration and is carried to the body’s cells.
Carbon dioxide is the waste gas produced by respiration and must be carried away from the body’s cells.
Which gases are transported by the circulatory system?
The circulatory system carries 2 types of blood:
Two types of blood
Oxygen-poor blood
• blood going away from the body’s cells
• low oxygen • high carbon dioxide
• blood going to the body’s cells
• high oxygen • low carbon dioxide
Oxygen-rich blood
Heart Structure
• Divided into 2 sections by the SEPTUM
• Each side is also divided into 2 sections
• 4 chambers in total
Right side Oxygen-poor
blood
Left side
Oxygen-rich blood
• A lower chamber is called a ventricle
• An upper chamber is called an atrium (plural = atria)
Right ventricle
Right atrium
Left ventricle
Left atrium
Heart Chambers
Heart Chambers
Blood to body
Blood from lungs
Blood to lungs
Blood from body
• Atria take blood in
• Ventricles pump blood out
Heart Valves
Semilunar valve
Tricuspid valve
Semilunar valve
Bicuspid valve
• Heart chambers are separated by valves
• These stop blood going in the wrong direction
How are the valves kept in place?
• Tough tendons hold the valves in place
• They also stop the valves from flipping up and turning inside out
valve open
How do the valves work?
• A valve is like a door that only opens in one direction
Blood vessels attached to the heart
Double circulation
• Both circuits begin and end at the heart
• Known as DOUBLE CIRCULATION
Systemic circuit
• Does NOT pump blood to the lungs
• Pumps blood to all other major organs and tissues
Pulmonary circuit
• Carries blood to the lungs
Double Circulation
1. Blood is pumped from heart to lungs and back again
2. Blood is pumped from heart to body cells and back again
body’s
cells
lungs
The ventricles look different
body’s
cells
lungs Right Ventricle
• Pumps to the lungs • Short distance • Thin muscle walls
Left Ventricle
• Pumps to the body • Long distance • Thick muscle walls
Portal System
• Does not connect directly to the heart
Portal system: a blood pathway that begins and ends in capillaries
Hepatic portal system
• Connects the stomach and intestines to the liver
Blood supply to the heart
Coronary arteries
• Supply blood to the heart
• Branch from the aorta where it leaves the heart
Coronary veins
• Drain blood from the heart
• Return blood directly to the right atrium
Heart Dissection
Cardiac Cycle
Pacemaker • Located in the wall of
the right atrium
• Controls heartbeat
• Produces electrical impulses
• Causes atria and ventricles to contract
• The brain can increase or slow down the impulses
Control of the heartbeat
1. Pacemaker pulses, causing the atria to contract
2. The electrical impulse stimulates the AV node
3. AV node sends an impulse down special fibres in the septum
4. Ventricles contract
Two main stages of the heartbeat
Diastole
When heart chambers relax
Systole
When heart chambers contract
Heartbeat: one complete sequence of contraction and relaxation in the heart
Stages of heartbeat (Cardiac cycle)
There are 3 stages
1. Blood enters the heart
2. Blood pumped from atria to ventricles
3. Blood leaves the heart
Stages of heartbeat (Cardiac cycle)
1. Blood enters the heart
• Atria and ventricles are relaxed
• Blood enters the atria • All valves are closed
Stages of heartbeat (Cardiac cycle)
• Pacemaker impulses cause the atria to contract
• Blood is pumped to the ventricles
• Tricuspid and Bicuspid valves open
• Semilunar valves stay closed
2. Blood is pumped from atria to ventricles
Stages of heartbeat (Cardiac cycle)
• Atria relax • AV node impulses:
ventricles contract • Blood is forced out of heart • Semilunar valves open • Ventricles relax again • Semilunar valves close • Cycle starts again
3. Blood leaves the heart
Pulse rate
• Average adult heart rate = 72 times per min
• Depends on age, health and fitness
• Blood is pumped down arteries and causes a wave of expansion and contraction.
• This is the pulse.
Pulse rate
• Can be felt in areas of the body where arteries are close to the surface (e.g. neck and wrist)
Pulse rate Rate of
heartbeat
Can you find your pulse rate?
• Press 2 fingers firmly on your wrist
• Count the beats in 1 minute
• This is your pulse rate
BLOOD PRESSURE
Blood Pressure
• Blood pressure varies throughout the body
• It is highest in arteries
• It is lowest in veins
Blood pressure: the force exerted by blood on the walls of blood vessels
Measuring blood pressure
• Expressed as two numbers blood pressure changes as the heart contracts
and relaxes
• Pressure is highest when the heart contracts (systole)
• It is at its lowest when the heart relaxes (diastole)
• Young person’s blood pressure ~ 120
80 mm Hg
Measuring blood pressure
• Strap put around the upper arm
• How much pressure is required to stop blood flow in major artery?
Effect of Smoking, Diet and Exercise
Smoking
Ingredient Effect on the Circulatory System
• Increased heart rate • Increased blood pressure
Nicotine
Carbon monoxide • Reduces oxygen in the blood
Lower energy production in the body
Other chemicals
• Increased likelihood of blood clots in blood vessels (thrombosis)
• Lung cancer • Bronchitis
Diet 3 main dietary factors affect the circulatory system:
Factor Effect on the Circulatory System
Obesity
Fats (animal fats) • Cholesterol increases risk of
blockages by plaques heart attack Stroke
Salt • High blood pressure
• High blood pressure • Heart attacks
Exercise
• Increases muscle strength (including heart)
• Stronger heartbeat
• Improves blood circulation
• Reduces weight
Heart Disease
• Major cause of illness and death in Ireland
• What causes it?
• Mainly by clogging of arteries that supply blood to the heart
A Heart Experiment!
1. Get pulse rate per minute 3 times
2. Calculate average (add 3 results together and
divide by 3)
3. Record results
4. Try these different exercise types for 5 mins:
– Gentle walking
– Brisk walking
– Running
5. Stop and count pulse rate for 1 min after each excercise
6. Try next type of exercise and compare
Chapter 26: Heart and Blood Vessels
DONE!!