Body Plasma:

Blood is a special connective tissue consisting of a fluid matrix, the plasma and cells, the blood corpuscles.

It is slightly alkaline fluid having pH 7.4.

Plasma: Plasma is a straw coloured, viscous fluid constituting

Plasma without the clotting factors is called serum.

Albumins, globulins and fibrinogen are the important types of proteins present in the plasma.

Prothrombin help in blood clotting: Plasma also contain minerals like Na+, Ca2+, Mg2+,

HCO3–, Cl–

Functions of Blood Plasma.

• Transport

• Prevention of blood loss

• Retention of fluid in blood due to plasma proteins.

• Uniform distribution of heat all, over the body

Body Fluids

Intracellular Fluid (ICF) Extracellular Fluid (ECF)

Present within the cells Outside the cells of blood and lymph

BODY FLUIDS AND CIRCULATION:

Erythrocytes (Red Blood Corpuscles or RBCs)

Enucleated (non-nucleated), and lack cell organelles, they are biconcave, camel and

llama, rbcs are nucleated and oval in shape.

Abnormal rise in RBC count is termed as polycythaemia. Decrease in the number of RBCs is called erythrocytopenia.

Decrease in RBC stimulates release of erythropoietin from the kidney stimulates the

bone marrow to increase the production of RBCs.

RBCs contain a red coloured, iron containing complex protein called haemoglobin

A normal man contains 14-16 g of haemoglobin and a normal woman contains of 12-14 g haemoglobin.

Process of erythrocyte formation is called erythropoiesis

Vitamin B12 and folic acid stimulate the maturation of RBCs

RBCs have an average life span of 120 days after which they are destroyed in the

spleen. Therefore, spleen is called the graveyard of RBCs.

haemoglobin molecule is made of 2 alpha chains and 2 beta chains. Each alpha chain

consists of 141 amino acids while, each beta chain has 146 amino acids.

Haemoglobin of RBCs plays a significant role in transport of respiratory gases (i.e., oxygen and carbon dioxide).

Leucocytes: Granulocytes

ACIDOPHILS /

EOSINOPHILS

All granulocytes are amoeboid in shape.

Stain by acidic dye Eosin.

protect body against allergy & parasitic infection.

In allergy they synthesize histamine.

In parasitic infection they act as lysosome.

Increase in number of Acidophils occurs in Taeniasis,

Ascariasis, Hay fever (Parasitic infection).

BASOPHILS Smallest granulocytes.

Stain with basic dye methylene blue.

Main function is to secrete & transport heparin, histamine &

serotonin.

NEUTROPHILS /

HETEROPHILS

Stain by any dye (acidic, neutral, basic).

They can squeeze & comes out from the wall of blood capillaries

in tissue. This phenomenon is called Diapedesis.

Phagocytic in nature called as Micro police man.

In female neutrophils barr body is attached with lobe of nucleus

which is formed by the modification of X chromosomes.

Barr body is absent in male.

Leucocytes: Agranulocytes

MONOCYTES : Nucleus kidney shaped/bean shaped.

Phagocytic nature called as Macro police man.

Scavenger of blood because they engulf damaged or dead

& minute bits of blood corpuscles.

LYMPHOCYTES : Large nucleus is present.

Lymphocytes

T – lymphocytes B – lymphocytes

T – killer/Cytotoxic : Direct kill bacteria or viruses

T – lymphocytes : T – Helper : Stimulate B – lymphocytes to

produce antibody

T –Suppressor: Suppress T – killer and protect

immune system

B – lymphocytes : Its function is to produce, synthesize & transport antibodies.

Blood Corpuscles Diagram

Platelets or Thrombocytes

They are non-nucleated and derived from megakaryocyte cells of bone marrow.

Critical count of thrombocytes is 40,000/mm3. If number is less than critical count then

red spot or rashes appears on the skin called Purpura disease.

Their Count is 1.5 - 4.5 lakh/mm3.

Decrease in number of blood platelets is

called Thrombocytopenia.

In their cytoplasm basophilic granules are present which can be stained by methylene

blue.

Cytoplasm is composed of contractile protein Thrombasthenia.

Platelets are formed from the megakaryocytes by Thrombopoiesis from haemopoietic

tissues.

Platelets can release platelet factors (e.g., thromboplastin)involved in the

coagulation of blood.

In mammals, yolk sac (one of the embryonic membrane), liver, bone marrow, lymph

nodes, spleen and thymus are the haemopoietic organs

In adult most of the blood corpuscles are

formed in the red bone marrow of long

bones

Blood Clotting

Clotting time: 2 – 8 mins.

Static clots which grow bigger & bigger & ultimately

block the blood vessels.

If this clot is formed in the coronary vessels then

called as coronary thrombosis.

If found in brain, then called as cephalic thrombus

Moving clots.

Mechanism of blood clotting

proposed by Macfarlane &

Co-workers.

Blood Clotting

Thrombus Clot Embolus Clot

Releasing of

Thromboplastin

Injured tissue synthesizes exothromboplastin and platelets

synthesize endothromboplastin.

These react with plasma proteins in the presence of Ca++ ions

to form Prothrombinase enzymes. (Thrombokinase)

Conversion of Prothrombin

into Thrombin

Prothrombinase enzyme convert inactive

prothrombin into active thrombin in the presence

of Ca++ ion.

Conversion of

fibrinogen into fibrin

Thrombin protein polymerise monomers of fibrinogen

to form insoluble fibrous protein fibrin in which blood

corpuscles got trapped.

Blood – Corpuscles = Plasma

Plasma –fibrinogen and large proteins = Serum

Clotting Process - Diagram

Clotting Factors

I — Fibrinogen

II — Prothrombin

III — Thromboplastin

IV — Ca+2 (cofactor in each step of blood clotting)

V — Proaccelerin

VI — Accelerin (Rejected)

VII — Proconvertein

VIII — AHG (Anti Haemophilic Globin)

(Absent in haemophilia-A)

IX — Christmas factor

X — Stuart factor

XI — PTA (Plasma thromboplastin antecedent)

XII — Hagman factor (become active by friction)

XIII — FSF factor (Fibrin stabilising factor) (Laki lowand factor).

Vitamin K is

necessary for

the synthesis of

prothrombin in

the liver, helps in clotting.

Cascade Theory of Blood Clotting: 13 factors are required for blood clotting. The factors operate in a cascade manner

Blood Group

Antigen on the surface of RBC also called as agglutinogen.

Blood

groups

Antigen Antibody Receive Donate

A

B

AB

O

A

B

A , B

-

b

a

-

ab

A , O

B , O

A , B , AB , O

O

A , AB

B , AB

AB

A , B , AB ,

O O is universal donor

& AB is universal

acceptor.

Antibody for antigen is present in serum (plasma) called agglutinin.

A, B, O discovered by Landsteiner.

AB discovered by Adriano Sturli and Alfred von Decastello.

IA and IB – Dominant allele

IO – Recessive allele

O will gives its expression in homozygous condition.

IO IO O

Blood group AB is an example of co-dominance.

IA IB AB

Rh Factor

Discovered by Landsteiner &

wiener in Rhesus monkey.

In India % ratio of Rh is –

Rh+ — 97%

Rh– — 3%

In World –

Rh+ — 80%

Rh– — 20%

If Rh+ blood is transfused to Rh- then 1st blood transfusion is complete successfully but

during Ist blood transfusion Rh antibodies are formed in receiver's blood so in next blood

transfusion, agglutination of blood takes place.

Rh antigen is due to dominant gene.

If antigen is present then Rh+.

If antigen is absent then Rh–.

O- → universal donar.

AB+ → universal acceptor.

If mother is Rh- & father is Rh+ then offspring is also Rh+. In this case 1st pregnancy is

completely successful, in next pregnancy death of foetus will occur due to agglutination

of blood called erythroblastosis foetalies.

Functions of Blood

Blood transports O2 from the respiratory organs to the tissues and CO2

Blood transports the digested food from the alimentary canal to the different body cells.

Hormones are carried by blood

Blood transports excretory matter to the kidneys

Blood maintains the body temperature

Blood also provide immunity to the body

The blood prevent loss of blood from the site of injury by the formation of clot.

Lymph -

From blood water soluble substances and some leucocytes (WBCs) between the cells

of tissues called the interstitial fluid or tissue fluid.

Tissue fluid enters into lymph capillaries called as lymph. Lymph is a colourless

mobile connective tissue present in the lymphatic system

1.It is red in colour due to the presence of

haemoglobin in red cells.1. It is colourless as red blood cells are absent.

2.It moves away from the heart and towards the

heart. 2.

It moves in one direction i.e. , from tissues to sub-

clavians.

3. It consists of plasma, RBC, WBC, and plastelets. 3.It consists of plasma and WBC (maximum

lymphocytes)

4.Its plasma has more proteins, calcium and

phosphorus. 4.

Its plasma has less protein, calcium and

phosphorus.

5. Glucose concentration is low. 5. Glucose concentration is higher in lymph.

6. Flow of blood is fast. 6. Lymph flows very slowly.

Differences between Blood and Lymph

They are distributed in complete body between blood capillaries but absent. e.g. –

Epidermis, hairs, nails, claws, cornea of eye, brain, spinal cord, bones, cartilage, bone

marrow and spleen

Lymph capillaries of villi of intestine are called Lacteals

Lymph vessels: Lymph capillaries combine to form Lymph vessels.

Right thoracic lymph vessel: opens in right subclavian vein.

Left thoracic lymph vessel: It opens in left subclavian vein.

End of lymph vessels form nodes like structures called as lymph nodes.

Functions of Lymph

Fats are absorbed through

lymph in the lacteals present

in the intestinal villi.

maintain the blood volume in

the body.

Destroys microorganisms to

produce and secret

antibodies

Exchange of nutrients and gases between blood and cells.

Circulatory Pathways

Fishes have a 2-chambered heart with an atrium and a ventricle. In fishes, the heart

handles only deoxygenated blood called venous heart.

Amphibians and reptiles have a 3-chambered heart. In amphibians and reptiles, the

heart receives both deoxygenated and oxygenated blood and is called arteriovenous

heart.

Birds and mammals possess a 4-chambered heart. In crocodile, birds and

mammals two separate circulatory pathways are present in these organisms. It is

called double circulation.

Human circulatory system Structure - 1

Heart is protected by a double walled membranous sac called pericardium consists of a

fibrous layer called parietal pericardium, inner serous visceral pericardium,

enclosing the pericardial cavity filled with a pericardial fluid.

Human heart consists of four chambers: two relatively small upper chambers called atria

(sing atrium) and two larger lower chambers called ventricles.

Transverse groove is present between the atria and ventricles, called coronary sulcus.

Anterior interventricular sulcus and posterior interventricular sulcus. These sulci have

coronary arteries

Right and left atria are separated by inter-atrial septum called as have fossa ovalis.

Right atrium receives the openings of superior vena cava, inferior vena cava and

coronary sinus.

Inferior vena cava is guarded by eustachian valve.

Two ventricles are separated by interventricular septum.

Epicardium: Composed of simple squamous epithelium

Myocardium: Composed of cardiac muscles.

Endocardium: Composed by Simple Squamous Epithelium.

Atrium opens in ventricle by atria – ventricular foramen [A.V. Foramen]. On right by

tricuspid valve on left by bicuspid / mitral valve.

Cusps/flaps are attached with chorda Tendinae attached through papillary muscles.

From right ventricle pulmonary arch and from left ventricle carotid – system Arch

arise. Where these arch intersect, they are interconnected by fibrous strip called

ligamentous Arteriosus.

During embryonic development at the place of this ligament a narrow Ductus Arteriosus is present, which close before birth.

S.No. Neurogenic heart Myogenic heart

1

The heart beat is initiated by a

ganglion situated near the heart.

The heart beat is initiated by a

patch of modified heart muscle

2

The impulse of contraction orginates

from nervous system.

The impulse of contraction

orginates itself in the heart

3

The heart normally stops beating

immediately after removal from the

body. Therefore, heart transplantation

is not possible.

The heart removed from the body

continues to beat for some time.

Therefore, heart transplantation is

possible.

4

Examples: Hearts of some annelids

and most arthropods.

Examples: Hearts of molluscs and

vertebrates

Mechanism of Heart Pumping

Contraction of the heart is called a systole and its relaxation a diastole.

Sino-atrial node or SA node (SAN also called pace maker) is situated in the upper

lateral wall of the right atrium.

Atrioventricular node or AV node (AVN also called pace setter) lies in the wall

between the right atrium and right ventricle.

Atrioventricular bundle (AV bundle) arises from the AVN give rise to minute fibres

throughout the ventricular musculature of the respective sides and are called

Purkinje fibres.

SA & AV node are auto excitable auto excitable

SAN (SA node) can generate the maximum number of action potentials initiates a

wave of contraction which spreads over both the atria

This also stimulates the AVN which generates a fresh wave of contraction over

ventricles along the bundle of His and Purkinje fibres.

The human heart is myogenic, capable of generating a cardiac contraction independent of nervous input.

Firstly both Atria contract simultaneous followed by ventricular contraction.

Structure of Heart

External appearance of Heart

Internal Structure of Heart

Cardiac Cycle

Atrial Systole: atria contract due to wave of contraction stimulated by the SA node.

Atrial systole takes about 0.1 second, diastole phase for the next 0.7 second.

Ventricular Systole: ventricles begin to contract due to a wave of contraction,

stimulated by the AV node.

The bicuspid and tricuspid valves close immediately producing part of the first heart

sound.

The ventricular systole takes about

0.3 seconds.

ventricles undergo relaxation causes

second heart sound.

Ventricular diastole is of about 0.5

seconds.

Both the atria and ventricles are in

diastole called general pause.

The total duration of a cardiac cycle

is 0.8 seconds.

Heart Sound Heart beat and pulse:

The beating can be heard by stethoscope.

First heart sound-Lub is associated with the closure of the

bicuspid and tricuspid valves, low pitched and of long

duration (lasts for 0.15 seconds).

Heart Sounds:

Second sound-dup is associated with the closure of the

semilunar valves , highly pitched and shorter in duration

(lasts for 0.1 seconds).

When the semilunar valves are injured, a soft hissing noise

“lub shhh” is heard called a heart murmur, caused by the

syphilis, rheumatic fever or any other disease.

Heart Beat and Pulse:

The rhythmic contraction and relaxation of

the heart constitute the heart beat.

A wave of distention passes along the

arteries, immediately after a ventricular

systole called arterial pulse, can be felt by

(radial artery) near the wrist.

Regulation of Heartbeat:

Regulation of

Heartbeat

Neural Regulation: Cardiac Centre lies in medulla oblongata

from which the SA node receives nerve fibres.

Hormonal Regulation: adrenaline (epinephrine) and

noradrenaline (norepinephrine) regulate heart beat.

Noradrenaline accelerates the heart beat under normal conditions

while adrenaline does this at the time of emergency.

Thyroxine also increases heart rate.

Rate of

Heartbeat

Heart beats per minute is called heart rate.

Normal heart beat rate → Rhythmia

Abnormal heart rate → Arrhythmia

Decrease in heart rate → Bradycardia

Increase in heart rate → Tachycardia

Blood Pressure

Blood flows in Arteries and it exerts some pressure on their wall called Blood Pressure.

B.P. was first measured by → Stephan Halls in Horse

B.P. measured by → Sphygmomanometer

Instrument invented by → Riva Rocci

B.P. measured in → Brachial Artery

Pulse Pressure: It is difference of systolic and diastolic B.P.

Diastolic B.P.: During diastole of heart

pressure exerted by blood.

80 mm Hg [70 -90]

B.P. is of two types

Systolic B.P.: During systole

pressure exerted by blood. 120 mm

Hg [110 – 140]

Factors Affecting Blood Pressure and ECG

.

ECG is a graphical representation of the electrical activity of the heart during a cardiac

cycle.

P-wave represents the electrical excitation (depolarization) of the atria contraction of

both the atria.

QRS complex represents the depolarization of

the ventricles, ventricular contraction.

T-wave return of the ventricles from excited to

normal state (repolarisation).

By counting the number of QRS complexes one

can determine the heart beat of an individual.

Affecting factors:

Exercise → B.P. ↑Emotion → B.P. ↑Tension → B.P. ↑Excitement → B.P. ↑Age → B.P. increases with age

Obesity → B.P. ↑Just after taking food → B.P. ↑

Factors Affecting

Blood Pressure

Electro Cardio

Gram (ECG)

Blood Vessels

Arteries carry oxygenated blood (Except pulmonary artery) from the heart to different

body parts.

Veins bring deoxygenated blood (except pulmonary vein) from different body parts to

the heart.

Arteries and veins divide to form arterioles and venules respectively, Arterioles and

venules further divide into the thin walled vessels called capillary.

Nutrients, hormones, gases, etc. can diffuse into the tissue cells through the wall of

capillaries and vice versa.

Arteries Veins

1. Arteries carry blood from the heart to the

different parts of the body.

1. Veins bring back blood from different

parts of the body to the heart.

2. They are usually deep seated. 2. They are superficially situated.

3. The wall of arteries are thick and

muscular.

3. The wall of the veins are thin and non

muscular.

4. Arteries have no valves. 4. Veins have valves to prevent backflow of

the blood

5. In arteries the blood flows with jerks. 5. In veins blood flows smoothly.

6. The flow of the blood is fast as the blood

in arteries is under great pressure.

6. The flow of blood in veins is not so fast

because the blood in veins is under low

pressure.

7. Except the pulmonary arteries all the

arteries carry oxygenated blood.

7. Except pulmonary veins all the vein carry

deoxygenated blood.

Differences between Arteries and Veins

Arterial System in Human Body

Circulation

Double Circulation Single Circulation

Circulation

Systemic and Pulmonary Circulation

Systemic Circulation: involves flow of oxygenated blood from left ventricles to all parts

of the body and deoxygenated blood from various body parts to the right atrium.

Systemic circulation, is also called greater circulation or peripheral circulation.

Pulmonary Circulation: involve flow of deoxygenated blood from the right ventricles to

the lungs and the return of oxygenated blood from the lungs to the left atrium.

Pulmonary trunk divides into right and left pulmonary artery

Coronary and Portal Circulation

Coronary Circulation: Supply of blood to the heart muscles (myocardium).

Flow of oxygenated blood from the ascending aorta to the heart muscle and the return

of deoxygenated blood from the ascending aorta to the heart muscle and the return of

deoxygenated blood from the heart muscle to the right atrium is called coronary

(cardiac) circulation.

Vein which collects blood from one organ by one set of capillaries and distributes the

blood to some other organ by another set of capillaries is called a portal vein.

Portal Circulation

Hepatic Portal Selection Hypo physical Portal Circulation

Hepatic portal vein receives small veins from

the different regions of the digestive tract it

bifurcates and enter the corresponding liver

lobes and break up into capillaries

Absorbed food

Removes the waste

It carries blood proteins produced in the

liver

Hypo physical portal vein carry blood

from the hypothalamus of the brain to

the anterior lobe of the pituitary gland

(hypothesis) enables the hormones of

hypothalamus to reach the anterior lobe

of the pituitary gland.

DISEASES OF Circulatory System:

High Blood

Pressure

(Hypertension)

Increase in the blood pressure beyond 140mm Hg (systolic) and

90 mm Hg(diastolic), is referred as high blood pressure.

Sustained rise in the arterial blood pressure is known as

hypertension.

Atherosclerosis Deposition of lipids on the wall lining of large and medium size

arteries. This results into the reduction of the lumen size of the

artery, the flow of blood is also reduced.

Plaques may also completely block the artery. If formed in the

coronary artery, may result in heart attack or stroke.

Angina pectoris when no enough oxygen is reaching to the heart muscle cause acute

chest pain.

Heart Failure: When heart is not pumping blood effectively enough to meet the needs of

the body also called congestive heart failure.

Heart Attack: Heart muscles are suddenly damaged by an inadequate blood supply

called myocardial infarction.

Cardiac Arrest: sudden and complete loss of cardiac function.

Arteriosclerosis: Hardening and loss of elasticity of walls of arteries.

Important Points-1

Saphenous vein(from the leg) and the internal mammary artery(from the chest) are

mostly for this graft. Artificial pacemaker is a mechanical device operated by Lithium

battery used to replace damaged SA Node.

Angioplasty: Technique for unblocking coronary arteries that have atherosclerotic

plaque.

Coronary Artery Bypass Grafting(CABG). Surgical procedure, a blood vessel from

another part of the body is used to bypass the blocked region of a coronary artery.

Anticoagulant (substances which prevent blood clotting)

Natural – Heparin

Artificial – EDTA(Ethylene Diamine Tetra Acetic Acid) Na citrate, oxalate

Thrombus: Blood clot formed in blood vessels blocking the flow of blood

Cardiomegaly: Heart enlargement.

Angiology :Study of blood vascular and lymphatic systems.

William Harvey is regarded as the Father of Angiology

Important Points-2

The vasa vasorum is a network of small blood vessels that supply the walls of large blood

vessels, such as elastic arteries (e.g., the aorta) and large veins (e.g., the venae cavae).

• Largest vein in human body–inferior vena cava.

• Largest Artery—Aorta.

• Smallest blood vessel in the body—blood capillary.

The giraffe’s blood pressure may be the highest.

Renal vein carries the least amount of urea. However hepatic vein carries maximum amount

of urea.

On 3 December 1967, South African doctor, Dr Christiaan (Chris) Barnard, performed the

world's first human to human heart transplant at Groote Schuur Hospital, Cape Town.

The blue whale (Balaenoptera musculus) has the largest heart of any living creature.

The largest heart for a terrestrial animal is that of the African elephant, weighing 12–21

kilograms (26–46 pounds), while the human heart is on average 310 grams (11 ounces).

Regulation of Heart Beat-1

• This center is under the influence of hypothalamus which is the controller of autonomic

activities.

The cardiac center lies in the medulla oblongata of the brain.

Nervous control

The cardiac center is formed of cardio-inhibitor and cardio-accelerated parts.

• The former decreases the rate of heart beat and the latter accelerates it. The cardio-

inhibitor is connected with the heart through vagus nerve (it carries – parasympathetic nerve

fibers) and cardio accelerator through sympathetic nerve fibers.

• Sensory fibers extended from the receptors present in the superior vena cava aorta and

carotid sinuses to the cardiovascular center in the medulla oblongata.

This chemical regulation of heart beat on behalf of nerves was discovered by Otto

Loewi.

The impulses received from the aorta and carotid sinuses decrease the heart rate, whereas

the impulses from Vena Cava increase the heart rate.

Regulation of Heart Beat-2

Vagus escape : Stimulation of vagus nerve decreases the heart rate but its continuous

stimulation shows no further decrease. This phenomenon is called Vagus escape.

Hormonal control

Thyroxine hormone also increases the heart beat by increasing energy production.

Hormones from adrenal medulla adrenaline and nor adrenaline accelerate the heart beat, the

latter under normal conditions and the former at the time of emergency.

Factors affecting heart rate

Heart rate increases with increase in basal metabolic rate (BMR).

Heart beat rate increases as the size of the animals body decreases.

Decrease in pH also increases heart rate.

Heart rate increases with increase in temperature.

Increase in Na+ ions in blood or in cardiac muscles, decrease heart rate.

Increased inspiration, muscular exercise, low oxygen tension, injection of adrenaline, thyroxine,

sympathin - all increase heart rate.

Increased expiration, during sleep, injection of acetylcholine decrease heart rate.

Lymphatic Organs: Spleen

Secondary lymphatic organs are the lymph nodes and spleen.

• They are called primary lymphatic organs because they produce B and T cells the

lymphocytes that carry out immune response.

• Haemopoietic stem cells in red bone marrow gives rise to B Cell and pre-T cells. Pre-T

cells then migrate to thymus gland.

In human primary lymphatic (lymphoid) organs of the body are the Red bone marrow

and Thymus gland.

Spleen :

Spleen is the largest solid mass of

reticulo-endothelial tissue in the body.

Spleen is mesodermal in origin.

Histologically it is formed by following structure -

Capsule : It is the outer covering of

spleen formed of dense connective

tissue and smooth muscles.

Closed and Open Circulatory System

• Vertebrates, and a few invertebrates, have a closed circulatory system.

• Closed circulatory systems have the blood closed at all times within vessels of different

size and wall thickness.

• In this type of system, blood is pumped

by a heart through vessels, and does not

normally fill body cavities.

• The open circulatory

system is common to

molluscs and

arthropods.

• Open circulatory

systems (evolved in

crustaceans, insects,

mollusks and other

invertebrates) pump

blood into a hemocoel

with the blood diffusing

back to the circulatory

system between cells.

Blood is pumped by a heart into the body cavities, where tissues are surrounded by the

blood.

Cyanosis

Cyanosis is defined as a bluish discoloration, especially of the skin and mucous

membranes, due to excessive concentration of deoxyhemoglobin in the blood caused

by deoxygenation.

• Cyanosis is divided into two main types: central (around the core, lips, and tongue) and

peripheral (only the extremities or fingers).

Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor

blood oxygenation in the lungs. It develops when arterial oxygen saturation drops below 85%

or 75%.

Peripheral cyanosis is the blue tint in

fingers or extremities, due to an

inadequate or obstructed circulation.

The blood reaching the extremities is

not oxygen-rich