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!!