Andhra Pradesh BIEAP AP Inter 2nd Year Zoology Study Material Lesson 2(a) Body Fluids and Circulation Textbook Questions and Answers.
AP Inter 2nd Year Zoology Study Material Lesson 2(a) Body Fluids and Circulation
Very Short Answer Questions
Write the differences between open and closed systems of circulation.
|Open circulation system||Closed circulation system|
|1. In this type, blood flows from the heart into the arteries and then into large spaces called sinuses.||1. In this type blood flows through a series of blood vessels.|
|2. Organs located in the space are bathed by blood.||2. Each organ has blood vessels that carry blood to it.|
|3. Blood flows slowly because there is no blood pressure after the blood leaves the blood vessels.||3. Blood flows at a high speed because there is high blood pressure after the blood leaves the heart.|
|4. It is found in Leeches, arthropods, and molluscs.||4. It is found in annelids and chordates.|
Sino-atrial node is called the pacemaker of our heart. Why?
Sino-atrial node consists of specialized cardio myocytes. It has the ability to generate action potentials without any external stimuli henc’e called pacemaker.
What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of the heart?
Atrio-ventricular node and atrio-ventricular bundle plays an important role in the contraction of ventricles.
Aricular contraction initiated by the wave of excitation from sino-atrial node (SAN) stimulate the atrio-ventricular node from where they are conducted through the bundle of His (atrio-ventricular bundle), its branches and Purkinje fibers to the entire ventricular musculature. This causes the stimulation ventricular systole. It lasts about 0.3 sec.
Name the valves that guard the left and right atrio-ventricular apertures in man.
Bicuspid valve (or) Mitral valve – Left atrio-ventricular aperture.
Tricuspid valve – Right atrio-venticular aperture.
Where is the valve of Thebesius in the heart of man.
Opening of coronary sinus into left precaval vein is bound by a crescentic fold known as valve of Thebesius.
Name the aortic arches arising from the ventricles of the heart of man.
- Pulmonary arch – arises from right ventricle.
- Left systemic arch – arises from left ventricle.
Name the heart sounds when they are produced.
The lub-dup sounds are produced by heart. The first sound ‘lub1 is caused by closure of the1 AV valves at the beginning of ventricular systole and preventing the back flow of blood. The second heart sound ‘dup’ results from the closure of the semilunar valves at the beginning of ventricle diastole and prevents the back flow of blood.
Define cardiac cycle and cardiac output.
Cardiac cycle :
Cardiac events that occur from the beginning of one heart beat to the beginning of the next is called cardiac cycle.
The volume of blood pumped out by the heart from each ventricle per minute is termed cardiac output. It is approximately 5 litres.
What is meant by double circulation? What is its significance?
The double circulation system of blood flow refers to the separate systems of pulmonary circulation and the systemic circulation. All animals with lungs have a double circulatory system.
In pulmonary circulation deoxygenated blood is pumped away from the heart, via pulmonary artery to the lungs and returns oxygenated blood to the heart via pulmonary vein.
In systemic circulation oxygenated blood away from heart to the rest of the body and returns deoxygenated blood back to the heart.
Why the arteries are more elastic than the vein?
Arteries are more elastic than vein because they are structurally designed to withstand tremendous blood pressures.
Veins on the other hand, contain blood at relatively low blood pressure.
Short Answer Questions
Describe the evolutionary change in the structural pattern of the heart among the vertebrates.
1) Fishes have the 2-chambered heart with an atrium and a ventricle. Blood passes through the heart only once in a complete circuit hence called single circulation. This means there is no separate circulation for oxygenated and deoxygenated blood.
2) Amphibians have a 3 – chambered heart with two atria and one ventricle, which further evolved in, reptiles, have two atria and an incompletely divided ventricle in which left atrium receives oxygenated blood from the gills / lungs / skin and right atriupi receives blood from the other parts of the body. The two types of, blood get’ mixed in the single ventricle, which pumps out mixed type of blood. Thus these animals show complete double circulation.
3) Birds and mammals possess 4-chambered heart with two atria and two ventricles. In these animals the oxygenated and the deoxygenated types of blood received by left and right atria, passes on to the left and right ventricles, respectively. The ventricles pump the blood out without any mixing of the oxygenated and deoxygenated types of blood. Hence these animals are said to be showing double circulation namely systemic arrd pulmonary circulations.
Describe atria of the. heart of man.
Atria are thin walled receiving chambers, form the anterior part of the heart. The right one is larger than the left, they are separated by inter-atrial septum. It has small pore in embryonic stage known as Foramen Ovale. Later it is closed and appears as a depression in the septum known as Fos&a ovalis. If the foramen ovale does not close properly, it is called a patent foramen ovale.
The right atrium receives deoxygenated blood from different parts of the body (except the lungs) through three caval veins like two precaval veins and one post caval vein. The right atrium also receives blood from the walls of the heart through the coronary sinus, whose opening into the right atrium is guarded by a crescentric fold, the valve of Thebesius. Opening of the post caval vein is guarded by the valve of inferior vena cavae or Eustachian valve. It directs the blood to the left atrium through the foramen ovale, in the fetal stage, but in the adults it becomes non functional.
The openings of the precaval veins into the right atrium have no valves. The left atrium receives oxygenated blood from lungs through a pair of pulmonary veins, which opens into the left atrium through a common pore. Atrio-ventricular septum separates atria and ventricles. It has right and left atrio-ventricular apertures.
Tricuspid valve guards the right atrio-ventricular aperture and bicuspid valve (mitral valve) guards the left atrio-ventricular aperture.
Describe the ventricles of the heart of man.
Two ventricles right and left form the posterior part of the heart. These are the thick walled blood pumping chambers, separated by inter-ventricular septum. The wall of the left ventricle is thicker than that of the right ventricle. The inner surface of ventricles is raised into muscular ridges or columns known as columnae carneae projecting from the inner walls of the ventricles. Some of them are large and conical and known as papillary muscles. Collagenous cords are known as chordae tendineae are present between atrio-ventricular valves and papillary muscles. They prevent the cusps of the antrio-ventricular valves from bulging too far into atria during ventricular systole.
Draw a labelled diagram of the L.S of the heart of man.
Describe the events in a cardiac cycle, briefly.
The cardiac events that occur from the beginning of one heart beat to the beginning of the next, is called cardiac cycle. Cardiac cycle consists of three phases namely atrial systole, ventricular systole and cardiac diastole.
i) Atrial systole: It lasts about 0.1 seconds.
→ The SAN generate an action potential which stimulate contraction of atria, which helps in the flow of blood into ventricles by about 30%. The remaining blood flows into the ventricles before the atrial systole.
ii) Ventricular systole : It lasts about 0.3 seconds
→ Ventricles contract and atria relax during this phase.
→ Contraction of ventricles raises the pressure in ventricles due to which AV valves are closed. It causes the first heart sound “Lub”.
→ When pressure in ventricles exceeds the pressure in aortic arches, semilunar valves open. It results the flow of blood from ventricles into aortic arches.
iii) Cardial diastole : It lasts about 0.4 seconds.
→ The ventricles now relax, atria are also in diastolic condition.
→ When pressure in ventricles falls below that in aortic arches, semilunar valves are closed.
→ It causes the second heart sound “dup”.
When pressure in ventricles falls below atrial pressure, AV valves open and ventricular filling begins. The total cycle takes about 0.8 seconds. This gives a heart rate of about 75 beats per minute.
Explain the mechanism of clotting of blood.
When a blood vessel is injured a number of physiological mechanisms Eire activated that promote hemostasis, and stops bleeding. Blood clots within 3-6 minutes after damage of a bloodvessel.
Mechanism of blood clotting: Blood clotting takes place in three essential steps, i) Formation of prothrombin activator : It is formed by two pathways.
a) Intrinsic pathway:
It occurs when the blood is exposed to collagen of injured wall of blood vessel. This activates factor XII, and in turn it activates another clotting factor, which activates yet another reaction, which results in the formation of prothrombin activator.
b) Extrinsic pathway:
It occurs when the damaged vascular wall or extra vascular tissue comes into contact with blood. This activates the release of tissue thromboplastin, from the damaged tissue. It activates the factor VII. As a result of these cascade reactions, the final product formed is the prothrombin activator.
ii) Activation of prothrombin:
The prothrombin activator, in the presence of sufficient amount of Ca2+, causes the convertion of inactive prothrombin to active thrombin.
iii) Convertion of soluble fibrinogen into fibrin:
Thrombin converts the soluble protein fibrinogen into soluble, fibrin monomers, which are held together by weak hydrogen bonds. The factor XIII replaces hydrogen bonds with covalent bonds and cross links the fibers to form a meshwork and prevent the blood bleeding.
Distinguish between SAN and AVN.
Sino-atrial node (SAN) :
It is present in the right upper comer of the right atrium. It is called pacemaker because it generates impulses for beating of heart. The action potential from SAN, stimulate, both atria which causes them to contract. Simultaneously causing the atrial systole. It lasts for 0.1 second.
Atrio ventricular node (AVN) :
It is seen in the lower left corner of the right atrium. AV node is a relay point that relays the action potential received from the SA node to the ventricular musculature through the bundle of His, its branches and Purkinje fibers. This causes the simultaneous ventricular systole. It lasts for about 0.3 seconds.
Distinguish between arteries and veins.
|1. Arteries carry oxygenated blood, away from the heart except pulmonary artery.||1. Veins carry deoxygenated blood towards the heart except the pulmonary veins.|
|2. These are bright red in colour.||2. These are dark red in colour.|
|3. These are mostly deeply seated in the body.||3. Veins are generally superficial.|
|4. Arteries are thick walled,with elastin and highly muscular.||4. Veins are thin walled and slightly muscular.|
|5. These possess narrow lumen.||5. These possess wide lumen.|
|6. Valves are absent.||6. Valves are present whiqh provide undirectional flow of blood.|
|7. Blood in the arteries flow with more pressure and by jerks.||7. Blood in the veins flow steadily with relatively low pressure.|
|8. Arteries end in capillaries.||8. Veins start with capillaries.|
|9. Arteries empty up at the time of death.||9. Veins get filled tip at the time of death.|
Long Answer Questions
Describe the structure of the heart of man with the help of neat labelled diagram.
Human heart is a hallow muscular, cone shaped, and pulsating organ situated between lungs. It is about the size of a closed fist.
The heart is covered by double walled pericardium, which consists of outer fibrous pericardium and inner serous pericardium. The serous pericardium is double layered, outer parietal layer and inner visceral layer. These two layers are separated by pericardial space, which is filled with pericardial fluid. This fluid reduces friction between the two membranes and allow free movement of the heart.
Human heart has four chambers with two smaller upper chambers called atria and two larger lower chambers called ventricles. Atria and ventricles are separated by a deep transverse groove called coronary sulcus.
i) Atria :
→ Atria are thin walled receiving chambers. The right one is larger than the left.
→ The two atria are separated by thin inter-atrial septum. It has a small pore known as Foramen Ovale in fetal stage Later it is closed and appears as depression (oval patch) known as ‘Fossa ovale’. If the foramen ovale does not close properly it is called a patent foramen ovale.
→ The right atrium receives deoxygenated blood from different parts of the body, through three caval veins like two precaval veins and one post caval vein.
→ The right atrium also receives blood from wall of the heart through coronary sinus, whose opening into the right‘atrium is guarded by the valve of Thebesius.
→ Opening of the post caval vein is guarded by the Eustachian valve. It is functional in fetal stage and directs the blood from post caval vein into left atrium thrdugh foramen ovale. But it is non-functional in adult.
→ The openings of the precaval veins into the right atrium have no valves.
→ Left atrium receives oxygenated blood from lungs through a pair of pulmonary veins, which open into the left atrium through a common pore.
→ Atrio-ventricular septum separates atria and ventricles. It has right and left atrio- venticular aperture’s.
→ Tricuspid valve guards the right atrio-ventricular aperture. Bicuspid valve guards the left atrio-ventricular aperture.
ii) Ventricles :
→ These are the thick walled blood pumping chambers, separated by an interventricular septum. The wall of the left ventricle is thicker than that of the right ventricle as the left ventricle must force the blood to all the parts of the body.
→ The inner surface of the ventricles is raised into muscular ridges called columnae cameae. Some of them are large and conical and known, as papillary muscles. Collagenous cords are known as chordae tendinae are present between atrio-ventricular valves and papillary muscles. They prevent the cusps of valves from bulging too far into atria during ventricular systole.
Nodal tissue :
A specialized cardiac musculature called the nodal tissue is also distributed in the heart.
- Sino-artrial node (SAN) – Present in the right upper corner of right atrium.
- Atrio-ventricular node (AVN) – Present in the lower left comer of right atrium.
iii) Aortic arches :
Human heart has two aortic arches.
1) Pulmonary arch :
Arises from the left anterior angle of the right ventricle. It carries deoxygenated blood to lungsf. It’s opening from right ventricle is guarded by pulmonary Valve made with 3 semiluminar valves.
2) Left systemic arch :
Arises from the left ventricle to distribute oxygenated blood tovarious pahs in the body. Its opening is also guarded by aortic valve made with a set of 3 semilunar valves.
A fibrous strand, known as ligamenturri arteriosm is present at the point of contact of the systemic and pulmonary arches. It is the remnant of the ductus arteriosus, which connects the systemic and pulmonary arches in the embryonic stage.