The Circulatory System

Functions of the Circulatory System

• Brings blood containing

oxygen, nutrients, and hormones to cells

• Transports CO2 and

other wastes away

from cells

Functions Continued • Fights infection

• Regulates body

temperature

• Helps stabilize pH and ionic concentration of body

fluids.

Functions Continued • Nutrients from the gut to the body

• Urea from the liver to the kidneys

The Need for an Exchange Surface

• In small organisms diffusion across their body

surface is sufficient:

o distances are short (less than 0.5 mm)

o surface area is relatively large.

• The body/cell surface acts as the exchange

surface.

Single Cell Organisms • No circulatory system

• Obtain O2 through the surface membrane

The Need for an Exchange Surface

• Large active organisms cannot rely upon their body

surface:

o surface area relative to volume is insufficient for

exchange

o distances are too great.

Single Cell Organisms • The ratio of supply and demand is:

Surface area

Volume

This is affected by the size

of the organism

This is called the surface area to volume ratio

Single Cell Organisms • Single Cell Organisms have a high surface to

volume ratio

• Cell surface membrane has a large enough area to

supply all the oxygen that their volume demands.

• Imagine an animal composed of a ball of cells

• What is the relationship between size, surface area,

volume and s.a.:volume ratio?

1 2 3

Diameter

/ mm

4

Surface

area / mm2

Volume

/ mm3

s.a. :

volume ratio

5

Surface area sphere = 4πr2

Volume of sphere = 4/3πr3

Surface area sphere = 4πr2

Volume of sphere = 4/3πr3

1 2 3

Diameter

/ mm

4

Surface

area / mm2

Volume

/ mm3

s.a. :

volume

ratio

5

12.6 50.3 113.1 201.1 314.2

4.2 33.5 113.1 268.1 523.6

3 1.5 1 0.75 0.60

Meeting the Demand • Thus there is a need for the following:

• Specialised exchange surface to meet the

demands of high activity levels in multi-cellular

organisms

• Efficient transport system to deliver materials to

and from the exchange surface

What Effect does an Increase in Size have on

the need for a Specialist Exchange Surface in

Larger Animals?

• As size increases, volume increases

disproportionately compared to volume.

• Demands of cells for nutrients and waste removal

also increased disproportionately:

o the surface does not increase sufficiently to

accommodate these extra demands

o must be met by a specialist exchange surface

with enhanced surface area.

General Features of Exchange Surfaces

Permeable

Thin

Moist

Mechanism to maintain diffusion gradients

The large surface can be provided by the body surface in small organisms or by folding of the exchange surface.

This speaks for itself.

Diffusion is only efficient over short distances (< 1mm). Rate is inversely proportional to square of the distance.

O2, CO2 and nutrients diffuse in solution.

Transport system, ventilation mechanism or creation of currents across surface.

Large surface area

relative to volume

Circulatory System

Circulatory System • Types

• Single – heart, gas exchange, body (fish)

• Double – heart, gas exchange, heart,

body

Circulatory System • Two distinct part of the Double System

o Pulmonary (lungs)

o Systemic (body)

o Animation

Circulatory System • Components

• Heart

• Blood

• Vessels

o Arteries

o Veins

o Capillaries

The Heart • A muscular pump

• Moves blood through

the body

• Is suspended in the

pericardial sac

• Composed of

four chambers

• Divided into right and

left halves

Aorta

Left pulmonary artery

Left atrium

Left pulmonary

veins

Left ventricle

Superior vena

cava

Right pulmonary

veins

Right atrium

Right ventricle

Inferior vena cava

The Heart • Made up of cardiac

muscle cells

• Do not fatigue like

skeletal muscle

• Contract over two

billion times in a lifetime

Pericardium • Protective sac of

connective tissue

• Surrounds the

heart

• Filled with

• fluid

Myocardium • The muscle of the heart

• Strong and thick

• Composed of

spontaneously

contracting cardiac

muscle fibers

• Conducts electricity

• Blood supply from the

coronary arteries

Structures of the Heart • Chambers

o Atria- (2) upper chambers

• Thin walled

• Receive blood from veins

• Send blood to ventricles

o Ventricles- (2) lower chambers

• Thick walled

• Receive blood from atria

• Pump blood out through arteries

• Chambers

o Atria (2) upper chambers

• Thin walled

• Receives blood from veins

• Sends blood to ventricles

o Ventricles (2) lower chambers

• Thick walled

• Received blood from atria

• Pump blood out through arteries

• Septum

o Wall that divides heart into right and left halves

Septum

Pulmonary valve

Right atrium

Tricuspid valve

Right ventricle

Left atrium

Aortic valve

Mitral valve

Left ventricle

Structures of the Heart • Valves

o Prevent backflow of blood

o Keep blood moving in one direction

o Between the chambers

o At junctions of artery and chamber

Tricuspid valve

Pulmonary veins

Mitral valve

Left atrium

Pulmonary valve

Aortic valve

Right atrium

Valves seen from above

Chordea tendinea

Pulmonary

valve

Structures of the Heart • Bicuspid and Tricuspid Valve (Atrioventricular)

o Control passage of blood from atrium to ventricle

• Semi-lunar valves

o Controls passage of blood from ventricle to

arteries

Papilla

ry

muscl

e

Cardiac Cycle

• Events from the beginning of

one heart beat to the

beginning of the next heart

beat

• When cardiac muscle

contracts it does so as a single

unit, creating a heart beat

• One heartbeat - a cardiac

cycle - consists of two parts

called systole and diastole

Cardiac Cycle • Diastole is the period of

time when the heart

relaxes after

contraction

• Oxygenated blood

from the lungs fills the

left atrium

• Deoxygenated blood

from other parts of the

body fills the right

atrium.

Cardiac Cycle

• Atrial systole is the contraction

of the heart muscle of the left

and right atria.

• Both atria contract at the

same time, sending blood into

the corresponding ventricle

Ventricular systole is

the contraction of the

muscles of the left

and right ventricles,

which contract at the

same time.

The term systole is

synonymous with

contraction of a

muscle.

Cardiac Cycle • Two normal heart

sounds with each heart

beat o described as a…..

• Heart Sounds “Lub”- sound- due

to closure of the

atrioventricular

valves

“Dub”- sound- due

to closure of the

aortic valve and

pulmonary valve

Cardiac Cycle • Heart Rate - count of each heart beat

o On average, a heart beats 70 times a minute when at rest

o Calculated as "beats per minute" (bpm).

o The pulse is used measuring the heart rate

o Heart rate is controlled by the medulla in the brain

Cardiac Cycle

• Resting heart rate can be

significantly lower in athletes

o Heart rate increases

when more food and

oxygen are needed by

the cells, or when under

stress

Cardiac Cycle

An electrocardiogram abbreviated as EKG

or ECG is a test that measures the electrical

activity of the heartbeat or one cardiac cycle.

Cardiac Conduction System

• Includes:

o SA node

(pacemaker)

o AV node

Purkinje

fibers

Pathway of Circulation • Describe the pathway

of the blood through the heart

Coronary Circulation • The coronary circulation consists of the

blood vessels that supply blood to, and remove blood from the heart muscle itself.

Coronary Circulation

• The vessels that supply blood high in oxygen to the myocardium are known as coronary arteries.

Arteries, Veins and Capillaries

Blood Vessels

• Form a closed circuit of

tubes that carry blood

throughout the body

• Laid end to end, the

blood vessels in an

average human body

will stretch

approximately 62,000

miles……2.5 times

around the earth

Blood Vessels • Are distinguished by

size, tissue layers

and direction of blood

flow

Blood Vessels • Arteries

o Receive blood from

ventricles

o Take blood away

from the heart

o Usually carry

oxygenated blood

o Thickest vessel walls

o Withstand greater blood pressure

o Are very elastic

o Connect to capillaries

o Aorta is the largest artery

Blood Vessels • Veins

o Transport blood away from capillaries

o Carry blood toward heart

o Take blood to atria

o Have valves

o Thinner vessel walls with less smooth muscles

than arteries

o Can stretch a great deal

o Have larger diameters

o Usually carry de-oxygenated blood

o Vena cava is the largest vein

Blood Vessels • The contraction of muscles compressing veins helps

push blood up through the leg veins back to the

heart. The valves allow the blood to flow towards

the heart only.

Calf muscle

relaxed

Calf muscle

contracts

Muscle

squeezes veins

Veins constrict;

blood moves;

valves open

Veins dialated;

blood still;

valves closed

Valves

OPEN

Valves

CLOSED

Blood Vessels • Capillaries

o Smallest of blood vessels

o Only one cell thick (epithelial cell)

o Connect arteries to veins

o Bring oxygen and nutrients to cells

o Removes CO2, urea, and other wastes from cells

o Where blood is under low pressure and moving slowly

Blood Vessels • A network of capillaries

runs close to the cells.

• The capillaries have very thin walls.

Arteriole Venule

Tissue cells Vein Artery capillaries

Capillaries

C B

O L

M O

P O

A D

R

I V

S E

O S

N S

E

O L

F S

Blood

Blood • The life stream of the body, affecting

every cell and

system we have.

• The blood is an

accumulation of

many different

elements, each

working in a specific

way to keep us

alive.

Blood

• Several types of cells suspended in a fluid medium known as plasma.

Blood • Functions of blood:

o Supply oxygen to tissues

o Supply nutrients such as glucose, amino acids

and fatty acids to tissues

o Removal of wastes such as

CO2 , urea and lactic acid

from tissues

o White cells, and detection of

foreign material by antibodies

Blood • Functions of blood continued:

o Messenger functions, including transport of

hormones and signaling of tissue

o Coagulation,

part of body's

self-repair

mechanism

o Regulation of

core body temperature

o Regulation of body pH and ion concentrations

Blood • What percent of your body is blood?

• How much blood do we contain?

o On average 4-6 liters

o We contain about a pint of

blood for every 7 kg

of body weight

• Composition of Blood:

o What percent of your blood is

cellular?

o What percent of your blood is

plasma?

8%

45%

55%

Blood • What is plasma?

o A clear, straw colored fluid

o What percent of plasma is water?

o What’s in plasma?

Dissolved gasses

Vitamins

Minerals

Salts

Nutrients

Enzymes

Hormones

Waste products

Plasma proteins

90% Buffy coat leukocytes

and platelets

(<1% of whole blood)

Erythrocytes

(45% of whole blood)

Plasma

(55% of whole blood)

Formed

elements

Blood • The cellular components are:

o red blood cells

o white blood cells

o platelets

• Blood cells are

formed in bone

marrow

Blood • Red Blood Cell (RBC) Characteristics

o Biconcave disks

o No nucleus

o Contain the iron based pigment hemoglobin

which binds with oxygen to transport it

o Life span about 120 days

o 5 billion/1mL of blood = most numerous

o Are very small

Blood Hemoglobin .…the iron

containing pigment

Hemoglobin makes red blood cells red

Blood • White Blood Cell (WBC)

Characteristics oNo definite shape

oHave nucleus

o Protect body against infection

o Life span varies (3 days-a few months)

o 7,000/1mL of blood

oNumbers increase if

infection is present

o Larger than RBC’s

Blood • Types of white blood cells:

o Monocytes are the

largest

o Neutrophils are the

most numerous

o Lymphocytes are

produced by the

lymph tissue

o Basophils release

histamines

Blood • Types of white blood cells:

The role of monocytes and neutrophyllis are to

phagocytize (engulf and then digest) cellular debris

and pathogens.

Blood • Types of white blood cells:

When an antigen enters the

body it is labeled. Memory

cells are produced.

The role of a lymphocytes

are to produce antibodies.

Make up 25% of WBC

Blood • Production of Antibodies

Weakened or dead version

of the pathogen is injected Vaccinations can help

boost WBC

Blood • Vaccinations

Vaccination tricks the

lymphocytes to produce

memory cells and

antibodies

Blood • Vaccination

Delivery type

Illness

Autism

Controversy

Blood • Platelet Characteristics:

o RBC fragments

o Irregularly shaped

o No nucleus

o 150,000-400,000/1mL

o Life span about 7-11 days

o Have a sticky surface

o Responsible for blood clotting (injury healing)

Blood • This is an actual picture of White Blood Cells,

in with some red blood cells. The platelets are stained purple, a T-Lymphocyte white cell is stained green, and a Monocyte white cell is stained gold as seen through a scanning electron microscope.

Blood Clotting • Steps in Blood Clotting:

• platelets clump

• platelets release thromboblastin

• thromboblastin

produces thrombin

• thrombin converts

fibrinogen into fibrin

• fibrin causes a clot

Fibrin

Let’s simplify

this shall we?

Blood Clotting • Blood vessel is injured.

• Platelets clump at the site and produce a substance that produces strands of fibrin.

• Fibrin strands help

to clog the opening or hole in the vessel.

Circulatory System Disorders

• Risk factors

o Older age

o Male gender

o Cigarette smoking

o High cholesterol

o Diabetes

o Stress

o Obesity

o Heredity

o Physical inactivity

o High blood pressure

Heart Disease Quitting smoking, a healthy diet and exercise may

reduce your risk of heart disease

Plaque in

coronary

artery

Circulatory System Disorders

• Starts with damage or injury to the inner layer of an artery

• Fatty deposits called plaque build up in the arteries

• This causes:

o Blockage in artery

o Less flexible vessels

o High Blood Pressure

Atherosclerosis

Circulatory System Disorders

• High Blood Pressure

Hypertension

Makes the heart

and blood

vessels work

harder

Increases the

chance of heart

disease, heart

attack or stroke

Circulatory System Disorders

• acute myocardial infarction

• Interruption of oxygen supply to the heart

• Causes death of the heart muscle

• Leading cause of death in both men and women

Heart Attack

Coronary Blockage

Circulatory System Disorders

• Interruption of oxygen supply to the brain

• Caused by:

o A clot in an artery

in the brain

o Breakage of an

artery in the brain

• Causes brain cells

to be deprived

of oxygen and die

Stroke

Circulatory System Disorders

• Thrombosis is the formation of a clot (thrombus) inside a blood vessel, obstructing the flow of blood

Thrombosis/Embolism

Circulatory System Disorders

• The loss of blood from the body

• Hematoma- a collection of blood due to internal bleeding (burse)

Hemorrhage

Gingival Hemorrhage

Circulatory System Disorders

• A rare inherited bleeding disorder in which the blood does not clot normally

• The person is missing or has low levels of certain

proteins in the blood called clotting factors

• Usually occurs only in males

Hem philia

Swelling in left knee joint

due to spontaneous bleeding

Circulatory System Disorders

• Abnormally low number of red blood cells circulating in the body or when the blood does not have enough hemoglobin

• There are different kinds of anemia

o Iron Deficiency

o Vitamin Deficiency

o Hemolytic Anemias

o Sickle Cell Anemia

Anemia

Circulatory System Disorders

• Sickle cell trait- The person is carrying the defective gene, but also has some normal hemoglobin

• Sickle cell anemia- The person has most or all of the normal hemoglobin replaced with the sickle hemoglobin

Sickle Cell Disease

Circulatory System Disorders

• Valvular Regurgitation • Valvular stenosis

o A condition in which there

is a narrowing, stiffening,

thickening,

fusion or

blockage of

one or more

valves of

the heart.

Valve Disorders

Circulatory System Disorders

• A whooshing sound between the heart beats

• The whoosh is an extra noise that blood makes as it flows through any of the heart's chambers or valves or even through a hole within the heart

Heart Murmur

Normal Heart Valve

Closed Opened

Problems

Closing

Problems

Opening