Answer: Option A. -> Fibrin
:
A
Thrombin acts on fibrinogen in the plasma and cleaves it to form insoluble fibrin strands.The insoluble fibrin strands are then stabilized to form a clot by fibrin stabilizing factor which is also activated by thrombin.

Answer: Option B. -> Oxygenated blood can be mixed with deoxygenated blood before passing through the tissues of the body.
:
B
Oxygenated blood can be mixed with deoxygenated blood before passing through the tissues of the body. Having a pulmonary circulation and pump that are separate from the systemic circulation and pump allows the systemic pump to re-pressurize the blood flow as it leaves the heart for the body's tissues. This increases the rate at which oxygen can be delivered to the tissues.

Answer: Option B. -> Repolarisation of atria
:
B
Electrocardiography (ECG or EKG*) is the process of recording the electrical activity of the heart over a period of time using electrodes placed on the skin. One cannot observe the repolarisation of atria via an ECG.

Answer: Option D. ->  (i)  - b   (ii) -  d  (iii) - a  (iv) - c
:
D
The heart is covered by a three-layered fibroserous sac called the pericardium, similar to the pleura encasing the lungs. The outer layer of the pericardium is the fibrous pericardium, comprised of dense connective tissue, which protects the heart, anchors it to the surrounding walls, and prevents it from overfilling. The visceral pericardium is in direct contact with the heart and is also called the epicardium, and is considered as the first layer of the heart. It covers the cardiac muscle, protects it, and produces serous fluid along with the parietal pericardium. This serous fluid is called pericardial fluid which not only cushions the heart, but also decreases friction created during the beating of the heart. The middle layer is the muscular portion of the heart, and is called the myocardium. It is responsible for the contraction of the heart.

Answer: Option A. -> (i) increase,(ii) constrict, (iii)increased
:
A
A person suffering from blood loss experiences a drop in blood pressure. To increase the blood pressure, the cardiac output is to be increased which is acquired by an increase in heartbeat. Since blood pressure is a function of both rate of heartbeat and the resistance of blood on the walls of the vessels. Blood pressure is also increased by vasoconstriction.

Answer: Option C. -> (i)Hepatic portal vein,(ii)hepatic vein
:
C
The hepatic portal vein carries blood rich in nutrients such as amino acids and glucose from different parts of the digestive tract to the liver. These nutrients are subjected to various metabolic activities in the liver such as glycogen synthesis and urea formation. From the liver hepatic veins carries blood to the inferior vena cava.

Answer: Option B. -> (i)Bundle of His, (ii) Purkinjefibres, (iii) AV node, (iv) SA node
:
B
The labelled parts in the image in order are Bundle of HIS, Purkinjefibres, AV node and SA node respectively. Electrical impulse travels from the SA node to the AV node from which it is transmitted through the bundle of HIS to the Purkinjefibres.

Answer: Option B. -> (i)⇒d, (ii)⇒c, (iii)⇒b,(iv)⇒a
:
B
The synovial fluid acts as a lubricant in the joints of the bones. The intraocular fluid present in the eyes supplies nutrition and also maintains the pressure in the eye.
The cerebrospinal fluid acts primarily as a shock absorber but also supplies nutrition. The intracellular fluid, which is present inside the cell, maintains the shape and size of cell.

Answer: Option B. -> Increased contractility of the myocardial cells
:
B
If the blood pressure is too low, the cardiovascular control centre in the medulla oblongata attempts to compensate by causing an increased contractility of the myocardial cells.

Answer: Option D. -> It is seen mainly in females.
:
D
Hemophilia is an inherited bleeding disorder in which the blood does not clot properly. This can lead to spontaneous bleeding as well as severe bleeding following injuries or surgery. If the mother carries the gene for hemophilia in her X chromosome, each of her sons will have a 50% chance of developing hemophilia. Although girls rarely develop the symptoms of hemophilia itself, they can be carriers of the disease. In some cases, girls who are carriers can have mild bleeding symptoms. But it is mostly men who develop it.