Introduction : This system is concerned with the circulation of body fluids to distribute various substances to various body parts.
Circulatory system in various groups of animals can be classified as follows :
Differences between open and closed circulatory system
Open circulatory system |
Closed circulatory system |
(1) In open circulatory system blood flows through large open spaces and channels called lacunae and sinuses among the tissues. |
(1) In closed circulatory system blood flows through a closed system of chambers called heart and blood vessels. |
(2) Tissues are in direct contact with the blood. |
(2) Blood does not come in direct contact with tissue. |
(3) Blood flow is very slow and blood has very low pressure. |
(3) Blood flow is quite rapid and blood has a high pressure. |
(4) Exchange of gases and nutrients takes place directly between blood and tissues. |
(4) Nutrients and gases pass through the capillary wall to the tissue fluid from where they are passed on to the tissues. |
(5) Less efficient as volume of blood flowing through a tissue cannot be controlled as blood flows out in open space. |
(5) More efficient as volume of blood can be regulated by the contraction and relaxation of the smooth muscles of the blood vessels. |
(6) Open circulatory system is found in higher invertebrates like most arthropods such as prawn, insects, etc., and in some molluscs. |
(6) closed circulatory system is found in echinoderms, some molluscs, annelids and all vertebrates. |
(7) Respiratory pigment, if present, is dissolved in plasma; RBCs are not present. |
(7) Respiratory pigment is present and may be dissolved in plasma but is usually held in RBCs. |
Route followed by water current in sponges :
Outside through
Dermal ostia
Incurrent canals
through prosopyles
Radial canals
through apopyles
through
Osculum
Spongocoel
through
gastric ostia
Excurrent canals
supra oesophageal vessel are called latero-oesophageal hearts. All hearts possess muscular pulsafile walls to pump blood into ventral vessel. Valves present to prevent back flow of blood.
Circulation in earthworm :
Behind 13th segment
Subneural vessel (from body wall)
Ist 13 segments Dorsal vessel
Lateral hearts
Lateral oesophageals
Anterior loops Supra oesophageal
Ventral vessel : Distributing vessel. Subneural vessel : Collecting vessel. Lateral oesophageal : Collecting vessel. Supra oesophageal : Collecting vessel.
Ventral vessel
Latero oesophageal hearts
Dorsal vessel : Distributing in 1st 13 segments and collecting in the region behind 13th segment.
Pumping of oxgenated blood by heart into arteries
Arteries open into blood sinuses and lacunae of haemocoel
Heart collects the oxygenated blood through a slit-like opening in its cardiac wall
Exchange of nutrients, gases and excretory wastes between blood in lacunae and sinuses and surrounding tissues
Oxygenated blood from gills returns to pericardial sinus
Oxygenation of blood in gills
CHAMBERS OF HEART
VALVES
DORSAL
DIAPHRAGM
Deoxygenated blood seeps out into ventral sinuses to be carried to the gills
OSTIA
ALARAY MUSCLES
ANTENNA
haemocoel filled with a fluid haemolymph. The heart lies in the pericardial sinus of haemocoel. The heart is 13 chambered, tubular dorsal vessel, pulsatile with an anterior aorta.
PERICARDIAL SINUS
VENTRAL DIAPHRAGM
PERIVISCERAL SINUS(HAEMOCOEL) PERINEURAL
SINUS
NERVE CORD
HEAD
NECK
PULSATORY AMPULLA
Each chamber is inverted funnel, shaped provided with valved
Fig. – Blood vascular system of cockroach (Diagrammatic)
lateral apertures called ostia. The heart is supported by 13 pairs of triangular fan like alary muscles. The blood sinuses are dorsal pericardial sinus, middle perivisceral sinus and the ventral perinural sinus or sternal sinus. These sinuses are separated from each other by dorsal diaphragm and ventral diaphragm. Blood or haemolymph is colourless contains haemcytes but is without respiratory pigment as it plays no role in respiration.
Circulation of blood in cockroach :
Heart Aorta Head sinuses
Pericardial sinus
Perivisceral sinus
Perineural sinus
(a) Single circulation (b) Double circulation
Differences between single and double circulation
Single circulation |
Double circulation |
(1) Blood flows only once through the heart in a complete |
(1) Blood flows in two circuit pulmonary and systemic.
Right auricle Left auricle Lungs Tissues Right ventricle Left ventricle |
cycle. Auricle Ventricle |
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Tissues Gills |
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(2) Heart pumps only deoxygenated blood, hence called |
(2) Heart pumps both deoxygenated and oxygenated |
Venous Heart. |
blood to lungs and body respectively, hence called |
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arteriovenous heart. |
(3) Blood is oxygenated in gills. |
(3) Blood is oxygenated in lungs. |
(4) Less efficient as gill capillaries slow down the blood flow. So, the body receives blood at a low pressure which decreases the rate of O2 supply to the cells i.e. keeps the metabolic rate low. |
(4) More efficient as blood flows at higher pressure, especially in birds and mammals, which increases the rate of food and O2 supply to the cell and also rapid removal of wastes from them i.e. provides a higher metabolic rate. |
(5) Found only in fishes. |
(5) Found in amphibians, reptiles, birds and mammals. |
Double circulation in mammals can be divided into three parts :
Arterial circulation – 15%
Capillary circulation – 5% Venous circulation – 64%
SUPERIOR VENA CAVA
SYSTEMIC CIRCULATIO
PULMONARY CIRCULATION –
AORTA
HEART –
7%
ARTERIES –13%
INFERIOR VENA CAVA
ARTTERIOLES AND
CAPILLARIES –7%
Heart : The form, structure and function of heart exhibits much variation. The characteristics of heart of fishes, amphibians, reptiles,
VEINS, VENULES AND VENOUS SINUSOIDES –64%
Fig. – Distribution of blood volume in different parts of circulatory system
birds and mammals is presented in the following table.
Class of vertebrates |
Characteristics |
Example |
Diagram |
(1) Pisces (= Branchial |
Thick, muscular, made of cardiac muscles, has |
Labeo |
CONUS ARTERIOSUS
VENTRICLE
AURICLE SINUS VENO SUS
Fig. – Bronchial heart of a fish ex. Labeo and scoliodon |
heart) |
two chambers (i) auricle and (ii) ventricle. The |
Scoliodon |
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heart is called venous heart since it pumps deoxygenated blood to gills for oxygenation. |
Neoceratodus |
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This blood goes directly from gills to visceral |
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organs (single circuit circulation). A sinus |
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venosus and conus arteriosus is present. Lung |
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fishes have 2 auricles and 1 ventricle. |
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(2) Amphibians |
Heart consists of |
Frog |
LEFT AURICLE RIGHT AURICLE VENTRICLE
Fig. – Amphibian heart |
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(a) Two auricles |
Toad |
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(b) Undivided ventricle |
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(c) Sinus venosus |
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(d) Truncus arteriosus |
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(conus + proximal part of aorta) Right auricle |
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receives blood from all the visceral organs |
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(deoxygenated) via precaval and post caval. |
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Pulmonary artery carries deoxygenated blood |
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to lungs for oxygenation. This blood returns to |
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left auricle via pulmonary vein (Double circuit |
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circulation) |
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(3) Reptiles |
Heart consists of :
(Ventricle in crocodiles gavialis and alligator is completely divided)
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Lizards Snakes Turtles |
Fig. – Reptilian heart |
(4) Aves |
Exhibit double circulation Heart consists of
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Pigeon |
PULMONARY ARCH |
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LEFT AURICLE |
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RIGHT |
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AURICLE |
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RIGHT LEFT |
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VENTRICLE VENTRICLE |
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Fig. – Pigeon heart |
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(5) Mammals |
Same as bird except that mammals have left systemic arch. |
Rabbit, man |
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Outer fibrous pericardium
Pericardium
Inner serous pericardium
Outer parietal layer Inner visceral layer
Between the parietal and visceral layers, occurs a
narrow potential space, the pericardial cavity which is derived from coelom and is filled with serous pericardial fluid for frictionless movement and protection from shock and mechanical injury.
DIAPHRAG
Fig. – Diagram to show the layers of the pericardium
BRACHIOCEPHALIC TRUNK
RIGHT BRACHIOCEPHALIC VEIN
RIGHT SUBCLAVIAN ARTERY AND VEIN
SUPERIOR VENA CAVA
RIGHT LUNG
RIGHT ATRIUM
TRACHEA
LEFT COMMON CAROTID ARTERY
LEFT INTERNAL JUGLAR VEIN
LEFT BRACHIOCEPHALIC VEIN
ARCH OF AORTA
PULMONARY TRUNK LEFT PULMONARY
ARTERY
LEFT ATRIUM LEFT LUNG
LEFT VENTRICLE
DIAPHRAGM
PERICARDIUM
CORONARY SULCUS
RIGHT
APEX
INTERVENTRICLAR SULCUS
VENTRICLE
Fig. – Position of heart in our chest cavity
BRACHIOCEPHALIC TRUNK
SUPERIOR VENA CAVA
ASCENDING AORTA
RIGHT PULMONARY VEINS
RIGHT ATRIUM
CORONARY SULCUS
RIGHT VENTRICLE
INTERVENTRICULAR SULCUS
LEFT COMMON CAROTID ARTERY
LEFT SUBCLAVIAN ARTERY
ARCH OF AORTA PULMONARY
TRUNK
LEFT PULMONARY VEINS
LEFT ATRIUM GREAT
CARDIAC VEIN
LEFT VENTRICLE
APEX
interventricular sulcus which contains coronary blood vessels. The right ventricle does not reach apex.
Fig. – External features of human heart
In frog, sinus venosus spreads upon most of the dorsal side of heart and conus arteriosus lies obliquely upon the ventral surface of right atrium.
LEFT ANTERIOR VENA CAVA
AOROTIC TRUNKS
RIGHT ANTERIOR VENA CAVA
RIGHT ATRIUM
SINUS VENOSUS PULMONARY VEINS
VENTRICLE
AORTIC TRUNKS
LEFT ANTERIOR VENA CAVA
LEFT ATRIUM
LEFT ATRIUM
CORONARY SULCUS
POSTERIOR
CONUS ARTERIOSUS
CORONARY SULCUS
DORSAL VIEW VENTRAL VIEW
Fig. – Dorsal and ventral of frog's heart
(a) Auricles : Atria are thin walled. They act as
SYNANGIUM
TO CAROTID
reserviors for blood entering the heart. Right auricle is bigger than left auricle and both are separated by a myomembranous partition called Interatrial or interauricular