Questions - Answers
Very Short Answer Type Questions
1. Write differences between open and closed systems of circulation.
A: a) In open type, blood flows from heart to arteries. They open into large sinuses in tissues. From these sinuses, blood is returned to heart by veins.
e.g.: Leech
b) In closed type, blood flows only through blood vessels there are no sinuses. Arteries and veins are connected by capillaries.
e.g.: Vertebrates
2. Sinoatrial node is called the pacemaker of our heart. Why?
A: S.A. node is formed by cardiac muscle cells. It has ability to generate action potentials without external stimuli. Hence, it is called pacemaker.
3. What is the significance of atrio ventricular node and A.V. bundle in the functioning of heart?
A: A.V. node send the action potentials received from the S.A. node into muscles of ventricles through A.V. bundle (Hence, A.V. node is a relay point). Thus ventricles contract.
4. Name the valves that guard the left and right atrio ventricular apertures of man.
A: a) Left atrio ventricular aperture - bicuspid valve
b) Right atrio ventricular aperture - tricuspid valve
5. Where is the valve of Thebesius in the heart of man?
A: Right atrium receives blood from muscles of heart through a coronary sinus. Its opening into right atrium is guarded by the valve of Thebesius.
6. Name the aortic arches arising from the ventricles of heart of man.
A: a) Left ventricle - Left systemic arch.
b) Right ventricle - Pulmonary arch.
7. Name the heart sounds. When are they produced?
A: a) Lub and dub are the two heart sounds.
b) Lub sound is caused due to closure of atrio ventricular valves and the sound dub is formed due to closure of semi lunar valves at the bases of aortic arches.
8. Define cardiac cycle and cardiac output.
A: a) The cyclical events that occur from the beginning of one heart beat to the beginning of next constitute a cardiac cycle.
b) The volume of blood pumped out by the heart from each ventricle per minute is known as cardiac output.
9. What is meant by double circulation? What is its significance?
A: In one complete circuit in the body, the blood passes twice through the heart, once through right side and the other time through the left side. This type of circulation is called double circulation. In double circulation, oxygenated blood and deoxygenated blood remains separate.
10. Why arteries are more elastic than veins?
A: a) In arteries tunica media of its wall has elastic laminae on either side. But in veins only one elastic lamina is present.
b) Moreover, tunica media of arteries is formed by thick layer of smooth muscles. Whereas in veins, tunica media is thin.
11. Name the blood vessels that enter and exit the Kidney.
A: a) Blood vessel entering the Kidney - Renal artery.
b) Blood vessel that exits the Kidney - Renal vein.
12. What are renal pyramids and renal papillae?
A: a) Medulla of Kidney is formed into conical structures and project into the calyces. Those conical structures are called renal pyramids.
b) The pointed tips of renal pyramids are called renal papillae.
Short Answer Type Questions
1. Describe the evolutionary change in the structural pattern of the heart among vertebrates.
A: 
2. Describe atria of heart of man.
A: i. Atria (left and right) form the anterior part of the heart. Right atrium is larger than left one.
ii. The two atria are separated from each other by an inter atrial septum. In embryonic stage, it has a pore called foramen ovale. At the time of birth, when lungs become functional, it is closed leaving a small depression called fossa ovalis.
iii. Right atrium receives deoxygenated blood from different body parts through three major veins, namely, two precaval veins and a post caval vein. Right atrium also receives blood from wall of heart through a corononary sinus. Its opening is guarded by a valve of Thebesius.
iv. Near the opening of post caval vein, a rudimentary Eustachian valve is present. In embryonic stage it directs the blood from right atrium to left through foramen ovale.
v. Left atrium receives Oxygenated blood from the lungs by two pairs of pulmonary veins. They open into the left atrium through a common pore.
vi. In the right upper corner of right atrium, the pace maker called sinoatrial node (S.A. node) is present.
vii. Atria and ventricles are separated from each other by an atrio ventricular septum.
viii. In the lower left corner of the right atrium close to atrio ventricular septum, an atrio ventricular node is present.
3. Describe ventricles of heart of man.
A: i. Ventricles (left and right) form the posterior part of heart.
ii. Left Ventricle is large and has thick walls (than right ventricle) and the left and right ventricles are separated by an interventricular septum.
iii. The inner surface of ventricles is raised into ridges called columnae cornae (trabiculae cornae). Some of them are large and conical. They are called Papillary muscles.
iv. Right atrium opens into right ventricle through right atrio ventricular aperture. It is guarded by a Tricuspid valve.
v. Left atrium opens into left ventricle through left atrio ventricular aperture. It is guarded by a Bicuspid valve or Mitral valve.
vi. Tricuspid valve and Bicuspid valve allow the blood to flow from atria to respective ventricles only.
vii. Extending between tricuspid valve and bicuspid valve and papillary muscles, there are collagenous cords known as Chordae tendinae. They prevent the cusps of these valves to bulge into atria during ventricular systole.
viii. Arising from A.V. node, is a Bundle of His (A.V. Bundle). It extends into inter ventricular septum, divides into two branches and then, they divide further as Purkinje fibres. They extend into the muscular walls of ventricles.
4. Draw labelled diagram of L.S. of heart of man.
A:
5. Describe events in cardiac cycle.
A: The cyclical events that occur from the beginning of one heart beat to the beginning of next constitute a cardiac cycle. It is divisible into three phases, namely atrial systole, ventricular systole and cardiac diastole. The contraction of heart is known as systole and relaxation is known as diastole. A systole and its following diastole constitute a heart beat.
A. Atrial Systole (0.1 sec):
When the atria are filled with blood [right atrium with deoxygenated blood and left atrium with oxygenated blood], S.A. node (pace maker) generates an action potential which spreads over atria. Thus they contract. As a result, blood from right atrium flows into right ventricle and from the left atrium to left ventricle [during atrial systole 30% of blood reaches the ventricles and the 70% of blood flows into ventricles before atrial systole].
B. Ventricular Systole (0.3 sec):
i. The A.V. node receives the action potentials and conduct them to walls of ventricles through Bundle of His and Purkinje fibres. Thus ventricles contract (Now atria relaxes and are filled with blood).
ii. Thus blood flows into the aortic arches.
iii. Due to high pressure in ventricles, tricuspid valve and bicuspid valve are closed causing the first sound of heart beat - LUB.
C. Cardiac diastole (0.4 sec):
i. Now the ventricles relax and hence, pressure in ventricles falls. As a result, pulmonary valve and aortic valve are closed causing second sound of heart beat - DUB.
ii. Now blood that reached atria flows into ventricles by the pressure of blood in atria. At this stage all the four chambers are in relaxed state.
iii. Now another cardiac cycle sets in.
* In Man, the duration of Cardiac cycle is 0.8 sec, if heart beats at the rate of 72 times per minute.
6. Explain the mechanism of blood clotting.
A: Blood Clotting: As long as blood is in blood vessels, it is in fluid state. When a blood vessel is injured a number of physiological processes are initiated to promote hemostasis. Injured or broken blood vessel releases collagen into blood. They initiate vasoconstriction, formation of platelet plug and production of a web with fibrin. Vitamin K is necessary for blood clotting.
a. When blood vessel is damaged, the muscles in its wall contract and makes its lumen narrow.
b. The collagen released from the ruptured epithelial cells of blood vessel and platelets form a platelet plug.
c. The substances released by damaged tissue, plasma proteins and platelets start clotting process. Clot is a net of fibrin fibres in which blood cells entangle.
Mechanism of blood clotting:
1. The first step in the process of blood clotting is the formation of prothrombin activator. It is formed in either intrinsic pathway or extrinsic pathway.
a. In intrinsic pathway, when collagen (of damaged blood vessel) contacts the blood, factor XII is activated. It is turn activates the prothrombin activator.
b. In Extrinsic pathway, when collagen contacts the blood, tissue thromboplastin is released from the damaged tissue. It activates factor VII. It initiates the formation of prothrombin activator.
2. Now the prothrombin activator activates the prothrombin present in blood into active thrombin in presence of calcium ions.
3. Thrombin converts the soluble fibrinogen into soluble fibrin. Now the factor XIII (released by blood platelets) replaces the hydrogen bonds of soluble fibrin by covalent bonds. Thus insoluble fibrin threads are formed. They spread over the damaged part as a net. In the meshes, the blood cells entangle and thus blood clot is formed.
4. Then the blood clot begins to contract. So that the fluid is expelled out (It is called serum). This process is called clot reaction.
5. Serum is nothing but plasma without certain plasma proteins, such as prothrombin, fibrinogen etc.
7. Distinguish between S.A. node and A.V. node.
A: 1) S.A. node is formed by cardiac muscle cells (cardiomyocytes). It has ability to generate action potentials without external stimuli. Hence, it is called pace maker. As it is formed from muscle cells, it is described as myogenic pace maker.
2) A.V. node send the action potentials received from the S.A. node into ventricular muscles. Hence A.V. node is a relay point.
8. Distinguish between arteries and veins.
A:
Long Answer Type Questions
1. Describe structure of heart of man with neat labelled diagram.
A: Heart is the central pumping organ of blood. It is a muscular organ lies in the thoracic cavity in the mediastinum. Its posterior end slightly turned to left. Heart is mesodermal in origin and is covered by a double layered pericardium (outer fibrous layer and inner serus layer). The serus layer of pericardium is double layered- outer parietal layer and inner visceral layer. Parietal layer is fused with fibrous layer of pericardium. Visceral layer is attached to outer surface of heart and forms epicardium. Between these two layers, pericardial cavity is present and is filled with pericardial fluid. It reduces the friction and protects the heart from shocks.
The wall of heart has outer epicardium, middle myocardium (formed by cardiac muscles) and inner endocardium (formed by endothelial cells). Human heart is formed by four chambers. They are anterior atria (left and right) and posterior ventricles (left and right). Atria and Ventricles are separated by a deep groove called coronary sulcus. The two ventricles are separated by inter ventricular grooves. Posteriorly each atrium projects over the ventricle as auricular appendix.
a. Atria:
i. Atria (left and right) form the anterior part of the heart. Right atrium is larger than left one.
ii. The two atria are separated from each other by an inter atrial septum. In embryonic stage, it has a pore called foramen ovale. At the time of birth, when lungs become functional, it is closed leaving a small depression called fossa ovalis.
iii. Right atrium receives deoxygenated blood from different body parts through three major veins, namely, two precaval veins and a post caval vein. Right atrium also receives blood from wall of heart through a corononary sinus. Its opening is guarded by a valve of Thebesius.
iv. Near the opening of post caval vein, a rudimentary Eustachian valve is present. In embryonic stage it directs the blood from right atrium to left through foramen ovale.
v. Left atrium receives Oxygenated blood from the lungs by two pairs of pulmonary veins. They open into the left atrium through a common pore.
vi. In the right upper corner of right atrium, the pace maker called sinoatrial node (S.A. node) is present.
vii. Atria and ventricles are separated from each other by an atrio ventricular septum.
viii. In the lower left corner of the right atrium close to atrio ventricular septum an atrio ventricular node is present.
b. Ventricles:
i. Ventricles (left and right) form the posterior part of heart.
ii. Left ventricle is large and has thick walls (than right ventricle) and the left and right ventricles are separated by an interventricular septum.
iii. The inner surface of ventricles is raised into ridges called columnae cornae (trabiculae cornae). Some of them are large and conical. They are called Papillary muscles.
iv. Right atrium opens into right ventricle through right atrio ventricular aperture. It is guarded by a Tricuspid valve.
v. Left atrium opens into left ventricle through left atrio ventricular aperture. It is guarded by a Bicuspid valve or Mitral valve.
vi. Tricuspid Valve and Bicuspid Valve allow the blood to flow from atria to respective ventricles only.
vii. Extending between tricuspid valve and bicuspid valve and papillary muscles, there are collagenous cords known as Chordae tendineae. They prevent the cusps of these valves to bulge into atria during ventricular systole.
viii. Arising from A.V. node, is a Bundle of His (A.V. Bundle). It extends into inter ventricular septum, divides into two branches and then, they divide further as Purkinje fibres. They extend into the muscular walls of ventricles.
* S.A. node is formed by cardiac muscle cells (cardiomyocytes). It has ability to generate action potentials without external stimuli. Hence, it is called pace maker. As it is formed from muscle cells, it is described as myogenic pace maker.
* A.V. node send the action potentials received from the S.A. node into ventricular muscles. Hence A.V. node is a relay point.
c. Aortic arches: (Pulmonary arch and systemic arch)
i. Arising from the right ventricle, is a pulmonary arch. Its opening into right ventricle is guarded by a pulmonary valve. It allows the blood to flow into pulmonary arch only. Pulmonary arch transports the deoxygenated blood to lungs.
ii. Arising from the left ventricle, is a systemic arch. It turns to left side and supplies oxygenated blood to different body parts through its branches - called arteries. The opening of systemic arch into left ventricle is guarded by an aortic valve. It allows the blood to flow into systemic arch only.
iii. Pulmonary valve and aortic valve are formed by three semilunar valves each.
iv. At the point of contact, the systemic and pulmonary arches are connected by a fibrous strand called ligamentum arteriosum. It represents the remnant of ductus arteriosus [¤ In embryonic stage, systemic arch and pulmonary arch are connected by ductus arteriosus].
2. Write notes on working of heart of man.
A: The cyclical events that occur from the beginning of one heart beat to the beginning of next constitute a cardiac cycle. It is divisible into three phases, namely atrial systole, ventricular systole and cardiac diastole. The contraction of heart is known as systole and relaxation is known as diastole. A systole and its following diastole constitute a heart beat.
A. Atrial Systole (0.1 sec):
When the atria are filled with blood [right atrium with deoxygenated blood and left atrium with oxygenated blood], S.A. node (pace maker) generates an action potential which spreads over atria. Thus they contract. As a result, blood from right atrium flows into right ventricle and from the left atrium to left ventricle [during atrial systole 30% of blood reaches the ventricles and the 70% of blood flows into ventricles before atrial systole].
B. Ventricular Systole (0.3 sec):
i. The A.V. node receives the action potentials and conduct them to walls of ventricles through Bundle of His and Purkinje fibres. Thus ventricles contract (Now atria relaxes and are filled with blood).
ii. Thus blood flows into the aortic arches.
iii. Due to high pressure in ventricles, tricuspid valve and bicuspid valve are closed causing the first sound of heart beat - LUB.
C. Cardiac diastole (0.4 sec):
i. Now the ventricles relax and hence, pressure in ventricles fall. As a result, pulmonary valve and aortic valve are closed causing second sound of heart beat - DUB.
ii. Now blood that reached atria flows into ventricles by the pressure of blood in atria. At this stage all the four chambers are in relaxed state.
iii. Now another cardiac cycle sets in.
In Man, the duration of Cardiac cycle is 0.8 sec, if heart beats at the rate of 72 times per minute.
3. Cardiac Output:
a. The volume of blood pumped by each ventricle for each heart beat is known as stroke volume. It is about 70 ml.
b. The volume of blood pumped out by the heart from each ventricle per minute is known as cardiac output.
Cardiac output = Stroke volume × No. of beats per minute
= 70 ml × 72 times = 5,040 ml/min.
4. Double Circulation: In the heart of man, oxygenated and deoxygenated blood remain separate. Right side of the heart contains deoxygenated blood and left side contains oxygenated blood. In one complete circuit in the body, the blood passes twice through the heart, once through the right side and the other time through the left side. This type of circulation is called double circulation.
It includes systemic circulation and pulmonary circulation.
i. Systemic Circulation: The Oxygenated blood from left ventricle goes to all organs (except alveoli of lungs) through left systemic arch and its branches (arteries).
Deoxygenated blood from different organs (except from alveoli of lungs) enters the right atrium through the vena cavae. This circulation is called systemic circulation (greater circulation).
ii. Pulmonary circulation: Deoxygenated blood from right atrium flows into right ventricle and goes to alveoli of lungs through pulmonary arch. From the alveoli of lungs, oxygenated blood is collected and send it to left atrium by pulmonary veins. This circulation is called pulmonary circulation (lesser circulation).
3. Describe the excretory system of man giving structure of nephron.
A: 1. Kidneys: A pair of reddish brown, bean shape meta nephric kidneys is present in the abdominal cavity, one on each side of vertebral column at the level of last thoracic and third lumbar vertebrae. Kidneys are found attached to the inner surface of dorsal abdominal wall and are retroperitoneal organs. Right kidney is placed at a lower level than left one because of the presence of liver or right side (Each kidney of man weighs 120 g to 170 g). Each kidney is enclosed by a protective, tough fibrous capsule called renal capsule. The outer surface of the kidney is convex and inner surface is concave.
The concavity in the middle of inner surface of kidney is known as hilum. Renal artery enters the kidney and renal vein and ureter exit the kidney at hilum.
Internal structure: Vertical section of a kidney shows two distinct regions.. namely, outer cortex and inner medulla. Inside the kidney, ureter expands as a funnel like pelvis. The edges of pelvis have cup like concavities called calyces. Medulla is formed into cone like renal pyramids and fit into the calyces. Among the pyramids, cortex projects inward as columns of Bertin. Pointed tip of renal pyramid is called renal papilla.
Microscopic structure of Kidney: Each kidney is formed by about one million microscopic convoluted tubular structures called nephrons. In addition, kidneys contain a net work of blood capillaries, lymph sinuses, nerves and interstitial fluid (cortical fluid & medullary fluid).
Nephron: Nephron is the structural and functional unit of the kidney. A nephron has a Malpighian body (formed by Bowman's capsule and glomerulus) or renal corpuscle and a renal tubule. Malpighian body lies in cortex.
i. The proximal blind end of renal tubule forms the double layered Bowman's capsule. It is formed by simple squamous cells called podocytes.
ii. A branch of renal artery- called afferent arteriole enters the cavity of Bowman's capsule and splits into capillaries. They unite and form an efferent arteriole and comes out of Bowman's capsule.
iii. The diameter of efferent arteriole is lesser than that of afferent arteriole.
iv. The capillary net formed by afferent and efferent arterioles in Bowman's capsule is called glomerulus. Glomerular capillary walls are formed by endothelial cells (single layer) and have minute pores - fenestrae.
v. Podocytes wrap around glomerular capillaries leaving minute spaces called filtration slits or slit pores.
vi. Renal Tubule behind the Bowman's capsule is divisible into Proximal Convoluted Tubule (PCT), Loop Of Henle (LOH) and Distal Convoluted Tubule (DCT).
vii. PCT is long and convoluted that lies in cortex. It is formed by cuboidal epithelial cells. Their inner surfaces have numerous microvilli (Brush boarders).
viii. PCT is continued as a hair pin like loop of Henle, which lies in medulla. It has a descending limb and an ascending limb. The wall of descending limb and lower part of ascending limb is thin and remaining part of ascending limb is thick.
ix. Ascending limb is continued as DCT, which lies in cortex. It is formed by cuboidal epithelium.
x. DCT ends as an initial collecting duct. Initial collecting ducts of many nephrons unite to form a straight collecting duct. It extends through renal pyramid (medulla), becomes duct of Bellini and opens into the renal pelvis on renal papilla.
* In some nephrons, LOH is short and lies in cortex only. Such nephrons are called cortical nephrons.
* In some nephrons, LOH is long and extends deep into medulla. They are called juxta medullary nephrons.
* Urinary tract infections in women are more common and the urethral opening is close to anus.
xi. The efferent arteriole reaches the renal tubule (PCT, LOH and DCT) and splits into capillaries around it.
* The capillary net around PCT and DCT is known as peritubular net.
* The capillary net around LOH is known as vasarecta.
* Number of functional nephrons in each kidney decreases by 10% per year after the age of 40 years in man.
* Each kidney filters about 1100 ml - 1200 ml blood per minute.
2. Ureters: From each kidney, a white muscular tube emerges out at hilum, called ureter. Their walls are formed by transitional epithelium. Ureters extend posteriorly and opens into urinary bladder.
3. Urinary bladder: Ureters open into a muscular and distensible sac called urinary bladder. It is lined by transitional epithelium. The neck of urinary bladder contin- ues as urethra. It is encircled by internal urethral sphincter (smooth muscles) and an external urethral sphincter (striated muscles). Urethra opens at the tip of penis in males and in females near the vaginal opening.
4. Explain Physiology of Urine Formation.
A: Urine: Urine is an aqueous solution containing water (96%), urea (2%) and other dissolved substances (2%). The process of urine formation involves glomerular filtration, selective reabsorption and tubular secretion.
1. Glomerular filtration: Blood containing nitrogenous wastes flows into the glomerulus through afferent arteriole with a pressure of 60 mm Hg. It is opposed by Bowman's capsular hydrostatic pressure of 18 mm Hg and glomerular blood colloidal osmotic pressure of 32 mm Hg (18 + 32 = 50 mm Hg). The net filtration pressure is 10 mm Hg in the glomerular capillaries. It causes the filtration of blood through filtration membrane. This process of pressure filtration through glomerular capillaries in Bowman's capsule is known as glomerular filtration.
* Filtration membrane is formed by three layers, namely, endothelial cell layer of glomerular capillaries, basement membrane and layer of podocytes of Bowman's capsule.
* Blood is filtered through minute pores and fenestrae of filtration membrane due to net filtration pressure (NFP) and the process is also called ultra filtration which is a non energy consuming (i.e., passive) process.
* RBC, WBC and plasma proteins having high molecular weight are unable to pass out during glomerular filtration.
The resultant filtrate is called primary urine or glomerular filtrate. It is hypotonic to cortical fluid. Glomerular filtrate contains water, amino acids, glucose, salts of Na, K, Ca, Mg etc., urea creatinine, toxins etc., The glomerular filtrates passes through the renal tubule where selective reabsorption and tubular secretion takesplace.
2. Selective reabsorption:
The cells of renal tubule absorb the essential substances from the glomerular filtrate by active transport, passive transport etc. The process of this absorption is unregulated in PCT and LOH and is regulated in DCT.
a. In PCT: The cuboidal cells with brush boarders in PCT absorb about 70% - 80% electrolytes and water along with all nutrients (glucose, amino acids etc.,). Water is absorbed by osmosis (obligatory water absorption). Na+ ions, glucose, amino acids and other essential substances are absorbed by active transport. To maintain pH and ionic balance of body fluids, cells of PCT secretes H+ and ammonia into the glomerular filtrate. At the end of PCT, glomerular filtrate is isotonic to cortical fluid.
b. In LOH:
i. In descending limb: In this part about 15% of water is absorbed by osmosis. Little amount of urea diffuses into the descending limb and thus the concentration of glomerular filtrate increases and is isotonic to medullary fluid.
ii. In ascending limb: This part is impermeable to water Na+, Cl−, Mg++, Ca++, K+, HCO3− etc., are reabsorbed in this region and H+ ions are secreted. Hence the glomerular filtrate progressively diluted and at the end of ascending limb, it is isotonic to medullary fluid.
c. In DCT: In this region, water is absorbed under the influence of Vasopressin (Anti Diuretic Hormone - ADH) of pituitary gland (Facultative water absorption). Under the influence of aldosterone (adrenal hormone) Na+ ions are reabsorbed. Moreover, K+ and HCO3− are absorbed and H+ ions and K+ ions are secreted. As a result, glomerular filtrate becomes isotonic to cortical fluid.
d. In collecting duct: Little quantity water is absorbed in this part under the regulation of ADH. In addition Na+ ions are absorbed and H+ ions are secreted. As a result, at the end of collecting duct, the glomerular filtrate is hypertonic to blood and is called urine.
3. Tubular secretion (Augmentation): During urine formation cells of renal tubule secrete H+ ions, K+ ions, ammonia, hippuric acid etc., into the tubule. This process is called tubular secretion.
