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Carbonic anhydrase.

S.A. node being self excitatory, initiates a wave of contraction in the heart.

Pericardial fluid is present between the two layers of the pericardium.

Pericardium double layered membranous covering of the heart.

Crocodile has four chambered heart.

Noradrenalin.

The left atrium is the receiving chamber for the oxygenated blood brought to it by the four pulmonary veins (two from each lung). The blood leaves the left atrium to fill the left ventricle which pumps the blood into the aorta.

The aorta is the main artery of the systemic circulation. From it, blood is contributed to the other arteries, arterioles and capillaries to different organs of the body. Blood is collected from the organs and poured into the venae cavae which bring blood back to the right atrium. This route constitutes the systemic circulation.

In the pulmonary circulation (or route) the blood leaves the right ventricle of the heart through the pulmonary artery (trunk), carrying deoxygenated blood to the lungs through its left and right branches. After oxygenation of this blood in the lungs it is carried back into the left atrium or auricle through the left and right pulmonary veins.

The volume of blood pumped by a each ventricle during one cycle is called stroke volume. It is about 70 ml.

• Neutrophils, eosinophils and basophils are three types of granulocytes.
• Neutrophils constitute 60 – 65 % of the total leucocytes and are phagocytic cells which destroy foreign organisms entering the body.

Joint diastole → atrial systole → ventricular systole and atrial diastole → ventricular diastole.

Heart conducting system contains Sino-atrial node, Atrio-ventricular node, AV-bundle and Purkinje fibres.

• SA node is situated in the upper lateral wall of the right atrium. 
• AV node is located in the posterior part of the interatrial septum.
• The AV bundle branches into two and enter left and right ventricles.
• Purkinje fibres are located throughout the ventricular wall.

Hepatic portal system is a unique vascular connection that exists between the digestive tract and the liver.

The hepatic portal vein carries blood from intestine to the liver before it is delivered to the systemic circulation.

An injury or a trauma stimulates the plate- 195 lets in the blood to release certain factors which activate the mechanism of coagulation. Clot or coagulam informed mainly of a network threads called fibrins in which dead and damaged formed elements of blood are trapped. Fibrins are formed by the conversion of inactive fibrinogens in the plasma by the enzyme thrombin. 

Thrombins, in turn are formed from another inactive substance present in the plasma called prothrombin. An enzyme complex, thrombokinase, is required for the above reaction which is formed by a series of linked enzymic reactions involving a number of factors present in the plasma in an inactive state. Calcium ions play a very important role in clotting.

Platelets originate from the megakaryocytes in the bone marrow. They live for about seven days. They release thromboplastins, which help convert prothrombin of the plasma into thrombin and thus help in clotting of blood.

(a) Basophils: They secrete histamine, serotonin, heparin etc. and are involved in inflammatory reactions.

(b) Eosinophils: They resist infections and are also associated with allergic reactions.

(c) Monocytes: They are phagocytic which destray foreign organisms entering the body.

(a) → (iii)

(b) → (v)

(c) → (i)

(d) →(ii)

(e) → (iv)

Body fluids need to be circulated constantly to supply nutrients, oxygen and other essential substances and for simultaneous removal of the wastes, for the healthy functioning of a living organisms.

Types of blood vascular system :

Open circulatory system – The main blood vessels arising from the heart pour the blood into tissue spaces called sinuses.

The blood comes in direct contact with the tissue cells thus exchanging respiratory gases, food materials and waste products directly between blood and tissue cells. 

-Blood flows slowly through the open sinuses because of lack of enough blood pressure. 

-Respiratory pigment, if any, is dissolved in blood plasma and red corpuscles are absent. 

-Found in some arthropods and most molluscs. 

Haemolymph – No distinction between blood and tissue fluid in animals with open circulatory system. Hence, blood / body fluid is appropriately called haemolymph.

Closed circulatory system –blood remains in blood vessels while circulating through the body and never comes in direct contact with the tissue cells. 

-Blood is distinct from the body fluid. 

A regular sequence of three events 

(i) auricular systole (ii) ventricular systole and (iii) Joint diastole during the completion of one heart beat.

(i) ‘Lubb’ the first sound which is low pitched is caused by the closure of bicuspid and tricuspid valves. 

(ii) ‘Dup’ the second sound which is high pitched is caused by the closure of semilunar valves.

A lymph node is specialised structure in lymphatic vessel concerned with the filtration of foreign bodies by the lymphocytes.

ABO grouping: Father of blood Grouping Karl landsteiner

ABO grouping is based on the presence or absence of two surface antigens (chemicals that can induce immune response) on the RBCs namely A and B. 

Plasma of different individuals contains natural antibodies (proteins produced in response to antigens). 

Blood of a donor has to be carefully matched with the blood of a recipient before any blood transfusion to avoid severe problems of clumping (destruction of RBC). 

(a) – (iii) (b) – (v) (c) – (ii) (d) – (i) (e) – (iv)

Blood is pumped by the heart by rhythmic contractions and relaxation (heart beat) of the auricles and ventricles in a definite order.

The conducting system brings about the rhythmic and automatic working of the heart (i.e. contraction and relaxation of the heart) through the transmission of impulses generated within specialised cardiac muscles and its channels, thereby accomplishing continuous circulation (or pumping) of blood through the heart.

The impulses for initiation of heart beat starts in the SAN (Sino-atrial node) or Pacemaker of the heart and is transmitted to the AV node (Atrioventricular node) through 3 special tracts or pathways (composed of specialised cardiac muscle fibres) called internodal pathways. From here the stimulus is carried by a single tract of specialised muscle called the “Bundle of His” in the beginning and diverted to the left and right side of the heart by its branches, (i.e. left and right branches).

These branches later rebranch profusely into Purkinje fibres. The Purkinje’s fibres transmit the Impulses received from the branches of Bundle of His to all the parts of the Ventricles bringing about simultaneous contraction of Ventricle pumping blood from right ventricle into lungs through pulmonary artery and pumping blood from left ventricle into aorta to various parts of the body through its branches. In this way impulses are transmitted through the conducting system ensuring systematic working of heart and blood supply.

The circulation of blood in which blood passes through the heart twice during one complete circuit is called as double circulation.

The heart of man is four-chambered. The left side of the heart is made up of left atrium or auricle (receiving chamber anterior region) and the left ventricle (pumping chamber posterior region). These two chambers are guarded by a bicuspid valve, opening towards the ventricle. The right half of the heart is made up of right atrium or auricle (on the anterior region) and right ventricle (on posterior region) these two chambers are guarded by the tricuspid valves opening towards ventricle. The valves ensure unidirectional flow of blood and prevent its backflow. The right half of the heart receives deoxygenated blood from body and the left half receives oxygenated blood from the lungs. The two halves are separated by the atrioventricular septum ensuring absolutely no mixing up of the blood between these two halves.

The oxygenated blood leaves the left ventricle through the aorta (the great vessel) and reaches various parts of the body through its branches, arteries and capillaries. After this blood is deoxygenated in cells and takes up CO2, it is returned back into the right side of the heart by venules and veins forming larger veins, the superior and inferior vena cava into the right auricle.

From here it enters the right ventricle and is pumped into the lungs through the pulmonary artery. (Aorta & pulmonary artery are guarded by semilunar valves). Later the oxygenated blood from lungs is, carried back into the left auricle or atrium by pulmonary- veins. From the left auricle it enters the left ventricle and from here blood is pumped into the aorta for distribution.

Thus blood circulates (without mixing up) continuously in the human heart and passes it twice during one complete circuit keeping the impure or deoxygenated blood separate from the oxygenated or pure blood during the circulation. This is known as double circulation.

The double circulation refers to the separate systems of pulmonary circulation and systemic circulation. The deoxygenated blood pumped into the pulmonary artery is passed on to the lungs from where the oxygenated blood is carried by the pulmonary veins into the left atrium. This pathway constitutes the pulmonary circulation.

The oxygenated blood entering the aorta is carried by arteries and capillaries to the tissues from where the deoxygenated blood is collected by a system of venules, veins and vena cava and emptied to the right atrium. This is the systemic circulation.

The systemic circulation is responsible for providing nutrients, O₂ and other essential substances to the tissues and taking away CO₂ and other harmful substances for elimination.

(a) Blood is a fluid connective tissue that contains plasma, RBC, WBC and platelets. Lymph is a tissue fluid formed from blood. It contains only lymphocytes.

(b) Open circulatory system is present in arthropods and molluscs in which blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses. Closed circulatory system is present in annelids and chordates in which blood pumped by the heart is always circulated through a closed network of blood vessels. Closed system can be better regulated than open system.

(c) Systole is the contraction of heart muscle and diastole is the dilation of the heart muscle. Systole results in increased pressure in heart chambers, whereas diastole results in decreased pressure.

(d) The P – wave represents the electrical excitation (on depolarisation) of the atria, which leads to the contraction of both the arteria. The T – wave represents the return of the ventricles from excited state to normal state (repolarisation). The end of T – wave marks the end of systole.

All vertebrates possess a muscular chambered heart. Fishes have 2 – chambered heart with an atrium and a ventricle. They have single circulation in which heart pumps deoxygenated blood, which is oxygenated by gills and supplied to body parts. Amphibians and reptiles have a 3 – chambered heart with two atria and a single ventricle.

They possess incomplete double circulation with oxygenated and deoxygenated blood getting mixed up in a single ventricle. Crocodiles, birds and mammals possess a 4 chambered heart with two atria and two ventricles. Two separate circulatory pathways are present in these organisms and hence have double circulation.

Connective tissue usually are involved in structure and support and derived from mesoderm. Blood is considered as a connective tissue because:

1. It has the same origin (mesodermal) as do the other connective tissues.

2. blood connects the body systems together bringing the needed oxygen, nutrients, hormones and other important molecules and removing the waste.

Blood is mesodermally derived; as other connective tissues. Blood serves the purpose of connecting the body systems; by transporting substances. Moreover, blood too has a matric; like other connective tissues. Hence, blood is considered as a connective tissue.

In a cardiac cycle when both atria and ventricles are in a diastole and are relaxed simultaneously is called a joint diastole.

Conducting system constitutes : SA node → AV node → Bundle of His → Purkinje fibres

Erythrocytes, Lymphocytes, monocytes, neutrophils, eosinophils, basophils and platelets.

 Interestitial fluid and blood plasma.

Heart- Special contractile blood pumping organ. 

Blood vessels – Tubes associated with heart into which the blood is pumped and circulated. Artery, Veins and Blood capillaries.

Blood - Fluid connective tissue, consists of a fluid matrix, plasma and formed elements. 

• Blood is a safer circulating fluid than environmental water because it is not affected by external changes like temperature variation, pollution etc. 
• Blood contains carrier molecules (haemoglobin, haemocyanin, plasma proteins) that can transport much larger amounts of nutrients and gases than water.

(a) → 3, (b)→5, (c)→2, (d)→1, (e)→4.

The organs are directly bathed in blood in case of open circulatory system. In case of closed circulatory system, the blood is channelized through closed vessels.

Contraction of heart muscles is called systole, while dilatation is called diastole. 

 Complete double circulation is present in birds and mammals. In this case, the oxygenated blood is received by the left atrium and the deoxygenated blood is received by the right atrium. The oxygenated blood is pumped out through the left ventricle, while the deoxygenated blood is pumped out through the right ventricle. In complete double circulation, there are two separate pathways for oxygenated and deoxygenated bloods. There is complete separation of oxygenated and deoxygenated blood in case of complete double circulation. This provides better efficiency to the organism in terms of energy generation.

P-wave marks the depolarization of atria, while T-wave marks the return of ventricles to repolarised state.

The circulation of blood in which blood passes through the heart twice during one complete circuit is called double circulation. The types are pulmonary and systemic circulation.

Normal activities of the heart are regulated intrinsically i.e., auto regulated by specialised muscles, hence our heart is called myogenic.

 A muscular chambered heart is present in all vertebrates. The fishes have a 2-chambered heart; with an atrium and a ventricle. Amphibians and reptiles have a 3-chambered heart; with two atria and one ventricle. But crocodiles have 4-chambered heart. Birds and mammals have 4-chambered heart; with two atria and two ventricles.

Sino – atrial node generates the action potential and determines the rate of the heart.

The pacemaker is a compact mass of muscle fibers which initiates each cardiac cycle, thereby setting or establishing the rate of beating-(pace) of the heart.

Eg: The sinoatrial (Sinuatrial) node situated inferior to the opening of the superior vena cava.