i. Arteries have thick, elastic walls and narrow lumen while veins have thinner, scarcely elastic walls and wide lumen.

A. Arteries have thick, elastic walls and narrow lumen while veins have thinner, scarcely elastic walls and wide lumen.

Veins carry deoxygenated blood (with the exception of pulmonary veins and umbilical vein) from different parts of the body to the heart. They have thin, elastic muscle layer with semilunar valves that prevent the blood from flowing in the opposite direction. 

• The pulmonary vein opens directly into the left atrium while postcaval and precaval veins into the right atrium.
  
• The posterior mesenteric vein is a blood vessel that drains blood from the small intestine (jejunum and ileum). At its termination behind the neck of the pancreas, it combines with the splenic vein to form the hepatic portal vein and hence does not open into the heart.
  

Veins drain capillaries in the tissues and organs and return the blood to the heart. Veins have a unique structural feature which is not present in arteries. They are equipped with one way valves, that prevent the back flow of blood.

Arteries carry blood from the ventricles (pumping chambers) of the heart out to the capillaries in organs and tissue. The smallest arteries are called arterioles.Veins drain capillaries in the tissues and organs and return the blood to the heart. The smallest veins are the venules.
Veins have a unique structural feature not present in arteries. They are equipped with one-way valves that prevent the backflow of blood.

Veins have thin walls as compared to arteries and are superficially located. They carry deoxygenated blood towards the heart and have valves which prevent blood from going backward. Arteries are elastic and thick because they need to transport high-pressure blood while in veins blood flows in low pressure. 

Bicuspid valve is another name for mitral valve. This valve is the valve between the left atrium and the left ventricle of the heart. It is composed of two triangular flaps, that is located between the left atrium and left ventricle and regulates blood flow between these chambers. 
Therefore, the correct answer is option D.

During ventricular systole. The pressure increases in the ventricles, thus forcing the oxygenated blood from left ventricle into systemic aorta and deoxygenated blood from right ventricle into pulmonary aorta.

Arteries carry blood from the heart to various organs of the body under high pressure so they have thick and elastic walls. Veins collect the blood from different organs and bring it back to the heart. The blood is no longer under pressure so, the walls are thin with valves to ensure that blood flows only in one direction.

In arteries the tunica media contains smooth muscle cells & elastic tissue, is thicker than that of veins so it can control and maintain blood pressure.

Capillaries are the smallest of a body's blood vessels, measuring 5-10 μm in diameter, which connect arterioles and venules, and enable the interchange of water, oxygen, carbon dioxide, and many other nutrients and waste chemical substances between blood and surrounding tissues. 

Capillaries are any of the minute blood vessels that form networks throughout the bodily tissues; it is through the capillaries that oxygen, nutrients, and wastes are exchanged between the blood and the tissues. The velocity of blood is slowest as it reaches capillaries making the easy exchange of substances. Their minimal thickness because of their single layer of squamous cells also helps in this. 

Veins are flattened with thin walls and hence have a wide lumen. Arteries are round with relatively thick walls. So, they have a narrow lumen. 

The acromial vein is actually a part of a greater network of veins located in the shoulder, near the acromion process in the scapula (shoulder blade). So the correct option is ' Scapula'.

As blood is pumped by the heart directly into the aorta, the blood travels at 30 cm/sec. From the aorta, blood flows into the arteries and arterioles and, ultimately, to the capillary beds. As it reaches the capillary beds, the rate of flow is dramatically (one-thousand times) slower than the rate of flow in the aorta. 

The blood in the pulmonary artery is under less pressure since it is only being pumped a short distance to the lungs and so does not need a thick wall. The aorta (which transports the blood over greater distances) receives blood under greater pressure from the powerful left ventricle and so needs a thicker wall. The pulmonary valve (pulmonic valve) is the semilunar valve of the heart that lies between the right ventricle and the pulmonary artery. Valves are used to prevent backflow of blood. The pulmonary vein carries oxygenated blood from the lungs to the left side of the heart, from the pulmonary circulation. The heart contraction is enough to keep the blood flowing as the distance between the lungs and back to the heart is minimal compared to the systemic circulation. So, the pressure of the heart exerting is enough to keep the blood in one direction.

Arteries are blood vessels that carry blood away from the heart. While most arteries carry oxygenated blood, there are two exceptions to this, the pulmonary and the umbilical arteries. All veins carry blood towards the heart. 

Visceral pericardium receives blood from coronary artery while parietal and fibrous pericardium get blood supply from internal thoracic (mammary artery).

The systole is the rhythmic contraction of the chambers of the heart (Atria and Ventricles) and diastole is the rhythmic relaxation of the chambers of the heart. The events occurring during one heartbeat is known as the cardiac cycle. During this cycle, the auricles and the ventricles of the heart rhythmically contract and relax.

Pulmonary artery and the Pulmonary vein are a set of blood vessels that are related to the lungs. The Pulmonary artery carries deoxygenated blood from the right ventricle to the lungs for oxygenation, this oxygenated blood is carried back to the heart by the Pulmonary vein for systemic circulation i.e. for ​circulation to different parts of the body.

Veins are less muscular than arteries, contain valves to help keep blood flowing in the right direction, towards the heart. They carry deoxygenated blood from tissues back to the heart. 

• Materials, including oxygen, carbon dioxide, amino acids, sugars, and water, are exchanged between the blood and tissue fluid within blood vessels known as capillaries.
  
• Blood pressure and osmotic pressure control the pressure in a capillary. Blood pressure, caused by the heart’s beating, is higher at the arterial end of the capillary and causes water to exit at that point.
  
• On the other hand, blood pressure is weak by the time blood reaches the venous end of the capillary, and osmotic pressure becomes higher, causing water to enter at that end.
  

Aorta is the largest artery present in the body. It originates from the left ventricle and extends down to the abdomen. The aorta distributes oxygenated blood to all parts of the body.

The human heart allows the complete separation of the deoxygenated and oxygenated blood. It has four chambers, the upper two atria and the lower two ventricles. The right side chambers (right atrium and right ventricle) are concerned with the deoxygenated blood. The right atrium receives the deoxygenated blood from the body and the right ventricle pumps it to the lungs. This is the pulmonary circulation. It completes when the left side chamber of the left atrium receives it. So, the left side chambers are concerned with oxygenated blood. The left ventricle then transports it to the rest of the body in the systemic circulation. So, the pulmonary and the systemic circulation maintained by the human heart constitute the double circulation of the blood.

Circulatory system or cardiovascular system is the organ system that helps to transport oxygen, nutrients, hormones etc to all the cell of the body. It consists of heart, veins, arteries, capillaries. Thus, the correct answer is option D.

Vaso means vessels and constriction means narrowing, therefore, narrowing of blood vessels results in vasoconstriction. Normally, it is done due to the shrinking of smooth muscles of vessels to react according to the environment by raising blood pressure for stabilization, prevent loss of heat, control blood flow in body, transfer nutrients and prevent from blood and fluid loss but in some cases it can also be a severe health problem leading to hypertension or high bp.

The Human circulatory system consists of a muscular four-chambered heart, a network of closed branching blood vessels and blood, the fluid which is circulated. The heart is a  4 chambered muscular organ present in the thoracic cavity in between the lungs. it does not have any bones. The chambers(spaces) of blood are filled with blood.T he muscular action of heart walls pump blood throughout the body through blood vessels. Hence the pumping