CIRCULATION

BLOOD

What percent of the human body is blood?

How much blood do we contain?On average 4-6 liters

8%

COMPOSITION OF BLOOD

Blood consists of a :

Liquid component: PLASMA

Solid component:BLOOD CELLS

How much is there of each component?

Plasma can be separated from the blood cells. How?

Centrifugation

plasma

Plasma is a clear, yellow fluid

Percentage of water in plasma : Substances dissolved in plasma:

GlucoseAmino acidsVitaminsMineralsLactic acid

Layering of blood components in a

centrifuged blood sample.

90%

HormonesUreaRespiratory gasesAntibodies Proteins

Question: MAY, 2010

Name the liquid component of blood and list TWO substances dissolved in it. (3)

Amino acidsGlucose[any two from previous list. FOOD is wrong]

PLASMA

Function of plasma:

to provide a medium through which continual exchange between cells and blood takes place

Blood flow

Body cells

Three types of blood cells:

a) ERYTHROCYTES or red blood cells

b) LEUCOCYTES or white blood cells

c) PLATELETS or thrombocytes

Leucocytes& platelets

Erythrocytes

Plasma

Red blood cells (RBC) are formed in the red bone marrow of the:

RibsSternum Vertebrae

RBC are: very small and numerous disc-shaped (BICONCAVE)

without a nucleus

contain the red pigment HAEMOGLOBIN function of RBC:

to transport oxygen & some carbon dioxide

About 2 million RBC per second are made but

production is faster at high altitude. Why?

There is not so much oxygen in the air.

Average life span of a RBC: 120 days

the old and worn out RBC are broken down in the:

liver

spleen

What forms from the haemoglobin broken down?

IRON part: stored in liver The rest of the haemoglobin molecule forms

BILE PIGMENTS bile pigments are

excreted in bile

Gall bladder stores bile

Red blood cells are adapted to carry oxygen:

1. biconcave disc shape offers maximum surface area for oxygen uptake

2. haemoglobin has a high AFFINITY for oxygen and combines with it, forming OXYHAEMOGLOBIN

3. no nucleus = more space for haemoglobin4. being small makes it possible for oxygen to

enter and leave the RBC quickly

Deoxygenated blood:

Deep red-purple

Oxygenated blood: Bright red

Fig. 3 Role of haemoglobin.

Carbon monoxide combines more readily with

haemoglobin than oxygen does

RBC do not carry oxygen to the cells Result:

WHITE BLOOD CELLS (WBC)

are less numerous than RBC

some live for months

most just a few days

Two types of WBC:

function of WBC: to protect the body against microbes

LYMPHOCYTE PHAGOCYTE

Lobednucleus

Spherical nucleus

Question: SEP, 2011Draw a labelled diagram of:i) a red blood cell as seen in section; (2)ii) a white blood cell that engulfs and digests

harmful bacteria. (3)

Lobed nucleus

i) ii) Cell membrane

Cytoplasm Cell membraneCytoplasm

Phagocytes are adapted to engulf bacteria by having:

an irregular shape a lobed nucleus

Phagocytes can squeeze out of capillaries.

What is ‘inflammation’? phagocytes move to an infected area to attack the

microbes when this happens the area becomes:

red swollen hot

INFLAMMATION

pus may formPus = accumulation of WBC

+ microbes

Lymphocytes are produced in the bone marrow :

and then move into the lymph nodes

Lymphocytes produce antibodies in response to antigens

antibodies are : proteins specific

antigen: material foreign to the body e.g.

a bacterium or virus

Antibodies begin the process of destruction of the microbe and

phagocytes finish the job

Immunity is a natural resistance to infection due to

antibodies

Question: SEP, 2002

White blood cells fight microbes. The number of white blood cells increases to eliminate the pathogens. Phagocytes engulf and digest harmful bacteria while lymphocytes produce antibodies.

Briefly explain why the presence of a large number of white blood cells in a blood sample, is an indication of the presence of an infectious disease. (3)

Platelets are cell fragments without a nucleus

function : important in blood clotting

How does clotting take place?

A clot begins to form when platelets are damaged. Platelets release a

substance (thromboplastin / thrombokinase).

Skin is cut.

A series of chemical reactions occur that ends up by producing

a meshwork of FIBRIN.

1 2

3

Clot dries up to form a scab

Blood clotting

HAEMOPHILIA is an inherited disease where a person’s

blood takes a very long time to clot

Blood clot formation needs a clotting factor: missing in haemophiliacs.

FUNCTIONS OF THE BLOOD

TRANSPORTPROTECTIONHOMEOSTASIS

SUMMARY OF THE BLOOD FUNCTIONS

TRANSPORT1. Oxygen from the lungs to the tissues.2. Carbon dioxide from the tissues to the lungs.3. Urea from the liver to the kidney.4. Digested food from the small intestine to the

tissues.5. Hormones from endocrine glands to target

organs.6. Heat from tissues, especially the muscles to the

whole body.

PROTECTION AGAINST MICROBES1. By clotting it prevents fluid being lost from cuts

and wounds.2. It protects against disease by killing microbes.

Phagocytosis

HOMEOSTASIS - keeping a constant internal environment by:1. keeping a constant body temperature - by

spreading warmth evenly around the body2. regulating the amounts of various substances in

the tissues

TYPES OF BLOOD VESSELS

Artery

Vein

Capillary

Blood from the heart.

Blood to the heart.

Circulatory System

VeinsCarry blood towards the heart.

VenulesCapillaries join to form venules.

Blood CapillariesWalls are one cell thick.Partially permeable lining allows substances todiffuse quickly. Slow movement of blood.

HeartRelaxed state: heart is filled withblood. Contracting heart: blood isbeing pumped with great force outto lungs and to rest of body.

ArteriesArtery carries blood away.

ArteriolesBranching of arteries.

What happens to an artery when it enters an organ?

Branches into arterioles and finally into capillaries.

Comparison of blood vessels in structure

Arteries Veins Capillaries1) Walls have a

thick muscle and elastic layer

Walls have a thin muscle and elastic layer

Walls are one cell thick

Capillaries are so thin that RBC have to squeeze through

Arteries Veins Capillaries2) No valves

presentValves present to prevent backflow No valves

One-way flow

Explain the presence of valves in leg and arm veins. (2)

Question: MAY, 2010

Explain the presence of valves in leg and arm veins. (2)

Question: MAY, 2010

The contraction of muscles compressing veins helps push blood up through the leg and arm veins back to the heart. The valves allow the blood to flow towards the heart only.

Arteries Veins Capillaries3) Fluid and WBC

cannot pass through wall

Fluid and WBC cannot pass through wall

Fluid without proteins can pass through wall. WBC pass out between cells

artery vein

capillary

Veins act as blood reservoirs

Question: MAY, 2010Explain the wide lumen diameter and thin walls in veins. (2)Veins can store a large volume of blood inside their wide lumen. Thin walls can easily extend to contain the blood.

Comparison of blood vessels in blood composition and flow

Arteries Veins Capillaries1) Flow is away

from the heartFlow is towards the heart

Flow is from artery to vein

HEART

Arteries Veins Capillaries2) Oxygenated blood

except pulmonary artery

Deoxygenated blood except pulmonary vein

Mixed

Pulmonary artery

Vein Artery

Question: SEP, 2012

List ONE function of the arterial blood vessels (arteries). (2)To supply oxygen to the body cells.

Arteries Veins Capillaries

3) Rapid flow Slow flow Very slow flow

4) High pressure Low pressure Low pressure

5) Pulse strong No pulse No pulse

force exerted by circulating blood on the walls of blood vessels

The pressure of the circulating blood decreases as blood moves away from the heart

Blood Pressure refers to the:

TISSUE FLUID bathes the cells and keeps them in the right

condition forms from the blood HOW?

Tissue fluid forms at a capillary bed under high blood pressure

Arterial flow

Venous flow

Lymphatic flow

As blood flows into capillaries:

1. Tissue fluid forms.2. Some tissue fluid

returns to the blood.

EXCHANGE AT A CAPILLARY BED

capillaries form a dense network in such a way that every cell is close to a capillary

lymphatic vessel

tissue fluid

lymphatic vessel

Tissue fluid forms from plasma. Lymph forms from…………..

10% tissue fluid enters lymphatic system

lymph

tissue fluid

plasma

Two properties of the capillary network to allow efficient exchange between the bloodstream & the cells: 1. Large surface area of the capillary network

2. Being one cell thick

What happens to the lymph that enters the lymphatic system?

Lymph empties into subclavian veins.

The Lymphatic System

Question: SEP, 2010

Give a biological explanation for each of the following.

Tissue fluid forms from blood. (4)Small molecules are forced out of the capillary at the arterial end under high blood pressure from the heart.

Comparison of blood plasma, tissue fluid and lymph

Blood plasma Tissue fluid LymphLOCATION Inside blood vessels Bathing living cells Inside lymph

vessels

Arterial flow

Lymphatic flow

Venous flow

Blood plasma Tissue fluid Lymph

COMPOSITION

Water, proteins, glucose, salts, hormones , amino acids Oxygen present

Very little protein, otherwise similar Oxygen present

More protein than tissue fluid but less than plasma. More lipids, otherwise similar. No oxygen

CELLS RBC, WBC, platelets WBC WBC

TRANSPORT

Blood pressure forces fluid through capillary at the arterial end. Osmosis returns fluid at the venous end of the capillary

From capillary under pressure and return by osmosis to capillary (90%) and 10% to lymph

From tissue fluid by drainage under pressure

THE HEART the heart muscle:

is called CARDIAC MUSCLE works without getting tired contracts automatically

CORONARY ARTERIES supply the heart with

oxygenated blood.

Blocking of a blood vessel by cholesterol

Blocked coronary artery leads to a

heart attack

Dead muscle tissue due to

lack of oxygen

Question:Suggest TWO ways in which a person’s lifestyle might lead to a blockage of the coronary arteries.

1. Lack of exercise.2. Smoking.3. Eating food rich in fats.4. Excessive alcohol intake.

What happens to the blood pressure if a blood vessel is

blocked?

Normal blood flow

Abnormal blood flow

The heart has four chambers

atria Two upper chambers: atria / auricles

Two lower chambers: ventricles

ventricles

A wall / septum separates the two sides. Why?

To prevent mixing of deoxygenated blood on the right side from the

oxygenated blood on the left.RIGHT LEFT

Four valves in the heart

Tricuspid valve:Prevents backflow

to right atrium

Bicuspid valve:Prevents backflow

to left atrium

Semilunar valves:Prevent backflow

to ventricles

RIGHT LEFT

Bicuspid valveTricuspid valve

Semilunar valves

Parts of the heartAtria:

Receiving Chambers

Ventricles: Pumping Chambers

Valves: Control Flow

Septum Divides the Heart

Vertical section: the heart

Aorta

Pulmonary vein

Left atriumRight atrium

Vena cava

Tricuspid valve

Pulmonary artery

Right ventricle

Tendon Left ventricle

Semi-lunar valvesBicuspid valve

Superior vena cava brings blood from:

head & arms

The atria have thinner walls than the ventricles

Thin-walled atrium

No need to build a high pressure as atria pump blood to the ventricles just below them. Ventricles pump blood further away so must have thicker walls to pump blood

at high pressure.

Thick-walled ventricle

Right ventricle has thinner walls than left ventricle

Right ventricle pumps blood to lungs which are near to heart but left ventricle pumps to whole

body. Thus less pressure is needed.

Right ventricle

Left ventricle

Question: SEP, 2010

Give a biological explanation for each of the following.Blood pressure is highest in the arteries and lowest in the veins.

(4)Highest blood pressure in arteries: blood is pumped into them by heart.Lowest in veins: blood is far away from heart.

What is a ‘stroke’?

• Interruption of oxygen supply to the brain• Caused by:

A clot in an artery in the brain

Breakage of an artery in the brain

• Causes brain cells to be deprivedof oxygen and die

It takes about 1 min. for blood to make 1 complete cycle

Ventricles contract Atria relax

Ventricles relax Atria contract

When ventricles contract blood

moves:out of the heart

When atria contract blood

moves:into the

ventricles

Are the ventricles in systole or in

diastole?

Systole: contraction

Diastole: relaxation

Atria contract / Ventricles relax

Ventricles contract / atria relax

The events of the cardiac cycle

Question: SEP, 2011

During exercise the heart pumps out a greater volume of blood per minute than when the body is at rest. List TWO ways in which the heart can increase the volume of blood pumped out. (4)1. Increase in heart beat rate.2. Each beat becomes stronger.

Double circulation: blood passes twice through the heart for each circuit of the body

Pulmonary circulation:Heart-lungs-heart

Systemic circulation:Heart-body-heart

Double circulation is found in:

birds mammals

Pulmonary vein

Aorta

Hepatic artery

Renal arteryRenal vein

Hepatic portal vein

Vena cava

Pulmonary artery

Hepatic vein

The blood transport system in humans

Question: SEP, 2007A red blood cell is present in a vein. Describe how the red blood cell will reach the lungs. In your answer mention the blood vessels and the different chambers of the heart that the red blood cell must pass through.

(4)The red blood cell present in a vein, enters the vena cava. The vena cava takes blood to the right atrium. Blood is pumped into the right ventricle and to the lungs via the pulmonary artery.

Question: SEP, 2007Describe how a red blood cell in the lungs reaches a kidney. In your answer mention the blood vessels and the different chambers of the heart that the red blood cell must pass through.

(5)The red blood cell leaves the lungs via the pulmonary vein and enters the left atrium. The blood is pumped into the left ventricle and out of the heart via the aorta. The red blood cell enters the kidney via the renal artery.

Question: MAY, 1998Trace the path of a molecule of glucose from the capillaries of the small intestine to the brain. (5)

A molecule of glucose is absorbed by the blood in the small intestine. It moves into the liver via the hepatic portal vein and out of it through the hepatic vein. Glucose enters the vena cava which takes blood to the right atrium. Blood is pumped into the right ventricle and to the lungs via the pulmonary artery. Blood leaves the lungs via the pulmonary vein and enters the left atrium. The blood is pumped into the left ventricle and out of the heart via the aorta. The aorta branches into many arteries and one such artery takes glucose to the brain.

Question: SEP, 2010Give a biological explanation for each of the following.The hepatic portal vein links two organs. (4)The liver is connected to the gut by the hepatic portal vein. As soon as digested food is absorbed into the blood, it goes to the liver. The liver removes extra amino acids by deamination and stores excess glucose as glycogen. Thus the liver plays a role in homeostasis.

Explain why a baby born with a hole in its heart tires very easily.

Deoxygenated blood from the right atrium flows into the left atrium where it mixes with oxygenated blood. The aorta carries this mixture to the muscles. The muscles do not receive enough oxygen.

Adult heart Foetal heart

THE END