Download Body fluids and circulation Lecture Notes

18- Body Fluids and Circulation
 Simple organisms such as sponges and coelenterates circulate water
from their surroundings through their body cavities to facilitate
exchange of materials through these cells.
 Higher organisms such as humans use blood and lymph (tissue fluid)
for the exchange of materials.
Blood
 Blood is a fluid connective tissue consisting of fluid matrix, plasma and
formed elements.
Plasma
 Plasma is a straw colored, viscous fluid constituting about 55% of
blood.
 Plasma without clotting factors is called serum.
Formed Elements
 Red blood corpuscles (Erythrocytes), White blood corpuscles
(Leucocytes) and platelets (Thrombocytes) together constitute formed
elements.
Red Blood Corpuscles
 Formation of RBCs is called as hemopoiesis/haematocytosis
White Blood Corpuscles
Blood Coagulation
Blood coagulation/clotting is a type of hemostasis mechanism to prevent
the excessive loss of blood from the body during injury or trauma.
Steps of Blood Coagulation
Platelets in blood migrate to the site of injury and clump the dead tissues
Blood vessels in that area become constricted
Platelets clumped with dead tissues releases Thromboplastin
Thromboplastin forms Thrombokinase (Prothrombinase) enzyme
Prothrombin, which is already present in blood in inactive form gets
activated by Thrombokinase to Thrombin in the presence of calciumhydrolyses
Thrombin catalyses to facilitate the conversion of fibrinogen (soluble) to
fibrin (insoluble)
Fibrin acts on dead and damaged formed elements by forming a network
of threads
Fibrin and dead elements are plugged while fibrin network forms a clot and
prevents the oozing of blood.
Circulatory System and its Types
Open Circulatory System
 Blood pumped by the heart passes through large blood vessels into
open spaces or cavities called sinuses.
 Eg: Arthropods, Malluscs
Closed Circulatory System
 Blood pumped by the heart is circulated through blood vessels.
 It is more advantageous as the flow of blood can be precisely regulated.
 Eg: Annelids, Chordates
Heart of Vertebrates
Pattern of Circulation in Vertebrates
1. Single circulation
2. Incomplete double circulation
3. Double circulation
Single circulation
 Seen in fishes
 Heart receives impure blood only (Deoxygenated blood). The heart is
called as venous heart.
 There is a unidirectional flow of blood towards the heart.
Incomplete Double circulation
 Seen in amphibians and reptiles (except crocodiles).
 Left Atrium receives OB from lungs/skin/gills. Right Atrium receives
DOB from the body parts.
 They get mixed up in the single ventricle.
 The ventricle pumps out the mixed blood.
Double circulation
 Seen in birds and mammals.
 Left atrium receives OB from the lungs and passes it to left ventricle.
 Right atrium receives DOB from body parts and passes it to right
ventricle.
 Ventricles pump out the blood separately without mixing.
Blood Vessels
Arteries, Veins, Capillaries
Arteries
 Arteries carry OB away
from the heart except
Pulmonary Artery.
 Arteries narrow down to
form capillaries.
 Arterioles further join with
the next ventriole.
 The area where arteriole
meets ventriole is forms
capillaries.
Layers of Arteries
1. Tunica Interna/Intima: Inner layer. Squamous endothelium
2. Tunica Media: Middle layer. Smooth muscles and elastic fibers.
3. Tunica Externa/Adventitia: External layer. Fibrous connective tissue
with collagen fiber.
Veins

Veins carry DOB towards the heart
except Pulmonary Vein.

The smaller branches of veins are
called venules/ventriole.

Veins also have three layers but
tunica media is comparatively thin.

The lumen in veins is large. Hence
to prevent backflow of blood, and ensure
unidirectional flow, veins have valves.
Heart
 The heart is a mesodermally derived organ located in the mediastinum.
It is present between the two lungs in the thoracic cavity. It is the size
of a fist.
 Heart is protected by double layered pericardium.
 The pericardial fluid in the pericardial space (between the pericardial
membranes) reduces the fiction between the walls of the heart and
surrounding tissues.
 Pericardium has 2 layers:
1. Outer Fibrous Pericardium
2. Inner Serous Pericardium
Structure of the Heart Wall
Outer Fibrous Pericardium
 It is the outermost layer of the heart which imparts rigidity to the heart.
 It prevents the rapid overfilling of the heart with blood.
Inner Serous Pericardium
 It reduces the friction generated by the heart during contraction.
 It acts as a lubricant.
 It protects the heart from infections.
Myocardium
 It is the middle layer of the heart.
 It is a musculature structure made up of cardiac muscles.
 Shows an overlapping pattern of arrangement, which is an adaptation
of the heart such that if pressure is exerted it can resist the pressure
and any kind of jerks.
 The cardiac muscles that make up Myocardium are called as
cardiomyocytes/ cardiacmyocytes.
Endocardium
 It lines the chamber of the heart.
 Embryologically and biologically it is similar to the epithelial cells of
blood vessels.
 It protects the heart chambers and valves.
Structure of the Heart
 The heart has 4 chambers- 2 upper atria (auricles) and 2 lower
ventricles.
 The walls of the ventricle (cardiac muscles) are thicker than the walls
of the atria.
 Between the two atria there is interatrial septum. Between the two
ventricles there is interventricular septum.
 In between the atria and ventricles, atrio-ventricular septum is present.
 The tricuspid valve (3 muscular flaps or cusps) is present between right
atrium and right ventricle.
 The bicuspid valve (mitral valve) is present between left atrium and left
ventricle.
 The tricuspid and bicuspid valve ensure unidirectional flow of blood
from atria to ventricles.
 Right ventricle has an opening to pulmonary artery and left ventricle
has an opening to aorta. They are called semi-lunar valves. They
prevent the backflow of blood.
 Veins and arteries running outside the heart are called coronary vein
and coronary artery.
 Posterior part of the heart is narrowed down (apex of heart) and
anterior part of the heart is broad.
Nodal System (Conducting system of the heart)
Nodal Tissues/Patches
 Nodal tissues/patches are specialized cardiac musculature present in
the heart wall.
 SAN- Present in the upper right corner of the right atrium.
 AVN- Present in the lower left corner of the right atrium just above
the atrio-ventricular septum.
Bundles
 Bundles extend from AVN through interventricular septum and
branch into right AV bundle and left AV bundle at the apex of the
heart.
Nodal fibers
 Each bundle on either side further branches out into fine thin fibers
called Purkinje fibers.
Structure of Nodal System
Functions of SAN
1.
2.
3.
4.
Generates electrical impulse
Further stimulates to create action potential.
Maintains action potential across the heart wall.
Controls entire heart and is called natural pacemaker of heart.
Functions of Nodal System
1.
2.
3.
4.
Generates electrical impulse
Further stimulates to create action potential.
Action potential spreads across heart walls through Purkinje fibers
Helps in the formation of cardiac cycle.
Functioning of Nodal System
1. SAN generates action potential without any external stimulus. That is
why it is called auto-excitable in nature.
2. Action potential reaches AVN
AV Bundle
Purkinje fibers
Spreads across the entire heart wall.
3. SAN initiates and maintains contraction of the heart by generating
action potential (70-75/min)
4. That is why it is called as the pacemaker of the heart.
Action Potential
 When there is no crossing of charges, it is called Resting Potential.
 Due to impulse, positive charges from outside the cell migrate inside
and negative charges from inside the cell migrate outside. This process
is called depolarization and the cell is called depolarized.
 After contraction, the ions regain their normal state. This process is
called repolarization.
Functioning of Action Potential
 Action potential or membrane potential occurs across the cell
membrane of the heart due to depolarizing current.
 Some stimulus causes the resting potential to change into action
potential that leads to a difference in voltage.
 A sudden, fast, transitory and propagating change in the resting
potential is called action potential.
Cardiac Cycle
Joint Diastole
 It is the state in which all chambers of the heart are relaxed.
 Pulmonary vein brings oxygenated blood into the left atrium and vena
cava brings deoxygenated blood into the right atrium.
 When the atria are filled, the tricuspid and bicuspid valves open and
blood flows into the ventricles.
 70% blood flows to the ventricles while 30% remains in the atria as it
requires extra action potential to flow to atria.
Atrial Systole
 SAN generates action potential.
 Atria contract (Atrial systole) and ventricles relax (ventricular diastole)
 Semilunar valves remain closed but tricuspid and bicuspid valves open.
Ventricular Systole
 Action Potential is conducted through ventricular sides by AVN and
AV bundle and is transmitted by Bundle of His through ventricular
musculature.
 Ventricles contract (Ventricular systole) and atria relax (atrial diastole).
 Due to ventricular systole, ventricular pressure increases. This causes
the closure of tricuspid and bicuspid valves, preventing the backflow
of blood into the atria. The semilunar valves open and oxygenated
blood enters aorta and deoxygenated blood enters pulmonary artery.
 Now the ventricles relax. Due to ventricular diastole, ventricular
pressure decreases. This causes the closure of semilunar valves,
preventing the backflow of blood into the ventricles. The tricuspid and
bicuspid valves open due to pressure in the atria.
 The heart chambers undergo joint diastole and the process repeats.
This cycle is called cardiac cycle.
A cardiac cycle is completed in 0.8s.
1 heartbeat=1 cardiac cycle.
Normal heartbeat= 70-75 times/min
Avg heartbeat=72 times/min
Stroke Volume and Cardiac Output
 Each ventricle pumps 70ml of blood during each cardiac cycle.
 This blood pumped out is called stroke volume.
Cardiac output= Stroke Volume x heartbeats/heartrate
= 70ml x 72
= 5040 ml
Electrocardiograph (ECG)
 Electrocardiogram is an instrument used to obtain electrocardiograph.
 Electrocardiogram is a graphical representation of the electrical activity
of the heart.
 A patient is connected to a machine having 3 leads
- 1 on either wrist (positive and negative terminal)
- Left knee/leg (neutral terminal)
 For a more detailed analysis, several leads are connected to the patient’s
chest region.
Electrocardiogram
P-Wave: Represents excitation (depolarization) of atria which causes atrial
systole.
QRS-Complex: Represents depolarization of ventricles which causes
ventricular systole.
T-Wave: Represents repolarization of ventricles.
Double Circulation
It is the process in which blood flows through the heart twice during one
cardiac cycle for completing its circuit. It includes: Pulmonary circulation,
Systemic circulation
Pulmonary circulation (b/w heart and lungs)
DOB from right ventricle
Pulmonary vein
Pulmonary artery
Lungs
OB from lungs
Left atrium
Systemic circulation (b/w heart and body tissues)
OB from left ventricle
Tissues
atrium
Aorta
DOB from tissues
Arteries
Venules
Arterioles
Vein
Capillaries
Vena cava
Right
 Systemic circulation helps to carry nutrients, O2 and other important
substances to the body tissues and brings harmful substances away
from the tissues.
Hepatic Portal System
 It is a system which includes the hepatic/hepato portal vein that carries
blood from intestine to liver before it is delivered for systemic
circulation. It extends from intestine/digestive track to liver and back.
Coronary Circulation System
 It is a system of coronary vessels that circulate blood to and from
cardiac musculature.
Lymphatic System
 Lymphatic system (also called sub system of circulatory system)
consists of lymph, lymph vessels and lymph nodes.
 As blood passes through the capillaries in tissues, some water and
soluble substances enter into intercellular spaces to form interstitial
(tissue) fluid.
 Some of this tissue fluid enters the lymphatic system and is called
lymph. It drains back into major veins.
 Lymph is a colourless fluid containing lymphocytes.
Functions of Lymphatic System
 Transports lymph throughout the body.
 Maintains body fluids by collecting excess tissue fluid and particulate
matter that gets deposited in the bloodstream.
 Takes part in the defense mechanism of the body and fights against
diseases through lymphocytes.
Formation of Lymph
 Due to extracellular transport, water, nutrients and minerals flow to
interstitial space.
 When it reaches the blood stream, excess fluids flow into the interstitial
space.
 This forms interstitial fluid.
 When the interstitial fluid reaches the lymph vessels, the excess
materials flow into lymph vessels. This is called lymph.
Blood Groups
 They were found by Carl Land Steiner.
 They include ABO grouping and Rh grouping.
ABO Grouping
 It is based on the presence of 2 surface antigens (chemicals that induce
response) called A and B antigen.
 Similarly, the plasma has 2 antibodies (substances released in response
to antigens) called anti-A and anti-B.
 Antigen A reacts with anti-A. Antigen B reacts with anti-B.
 The crossing of interactive antigens or antibodies causes clumping
(agglutination) of RBCs.
 People with O group are called universal donors as they can donate
blood to people of any blood group.
 People with AB group are called universal recipients as they can accept
blood from people of any blood group.
Rhesus (Rf) factor
 Rhesus (Rh) factor is an antigen found on RBCs.
 Rh+ve means Rh factor is present and Rh-ve means Rh factor is
absent.
 Most humans are Rh+ve.
 Anti Rh- antibodies are not naturally found. An Rh-ve person can
accept Rh+ve blood only once as it results in the formation of anti Rhantibodies in the person’s blood. A second Rh+ve transfusion will
cause agglutination of blood.
Erythroblastosis Foetalis
 It is an Rh incompatibility between the Rh-ve blood of mother and
Rh+ve blood of foetus.
 Rh antigens do not get mixed in maternal blood during pregnancy as
placenta separates the two bloods.
 However, during the time of delivery there is a small chance of
exposure of maternal blood to small amounts of Rh+ve blood from
foetal blood.
 This induces the formation of anti Rh- antibodies in maternal blood.
 In the case of mother’s second delivery, anti Rh- antibodies from
maternal blood leaks into foetal blood (Rh+ve).
 This can result in severe jaundice or anemia for the foetus. This
condition is called Erythroblastosis Foetalis.
Graveyard of RBCs- Spleen
Soldier of the body- Neutrophils
Natural pacemaker- SAN
Gatekeeper-AVN