Pulmonary veins

Veins are types of blood vessels which carry blood towards the heart. These carry deoxygenated blood from tissues back to the heart. Pulmonary veins are blood vessels that carry oxygen-rich blood from lungs to the left atrium where it is returned to the systemic circulation.

Pulmonary veins are the only veins in the adult human body, which contain a higher percentage of oxygenation of blood than their arterial counterpart, the pulmonary arteries. All other veins carry oxygen-poor blood.

Pulmonary veins are located between lungs and the heart. Pulmonary veins play an important role in respiration by receiving oxygenated blood in the alveoli and draining it into the left atrium.

Many smaller blood vessels converge in each of lungs (right and left) to form a pair of pulmonary veins. Each pair leaves its respective lung through a spot known as the hilum, or root. From there, pulmonary veins travel to the heart and connect with left atrium.

The pulmonary veins can become distended in congestive heart failure (left-sided heart failure), resulting in pulmonary edema. Damage to the pulmonary veins epithelial lining can cause pleural effusions as well.

There are typically four pulmonary veins, two draining each lung:
*Right superior: drains the right upper and middle lobes
*Right inferior: drains the right lower lobe
*Left superior: drains the left upper lobe
*Left inferior: drains the left lower lobe
Pulmonary veins

Hemoglobin as a carrier

Oxygen is carried in the blood mainly bound to hemoglobin; a minor fraction is dissolved in the plasma. Hemoglobin releases the oxygen that sustains every body cell.

There are about 2.5 billion red blood cells circulating at any one time. With some 280 million molecules of hemoglobin packed inside them – each of them capable of carrying four oxygen molecules.

The maximum oxygen that can be bound to the hemoglobin in the blood is the oxygen capacity. One gram of hemoglobin theoretically can carry up to 1.39 mL of oxygen. More commonly an oxygen binding capacity of 1.34 to 1.36 mL oxygen per gram hemoglobin is accepted.

Disturbances in oxygen uptake in the lungs, or in supply of adequate amounts of oxygen to the tissues, are common features of many congenital heart lesions.

Red blood cells can carry much larger quantities of carbon dioxide than they can carry oxygen. During rest 100 mL of blood carries an average of 4 mL of carbon dioxide from the tissue to the lungs.

While the oxygen-carrying hemoglobin imparts a red color to the blood, on its return to the lungs hemoglobin loaded with carbon dioxide loses its bright color and assumes a dark red-dish shade, akin to purple.
Hemoglobin as a carrier

What is meant by blood pressure?

Human body needs the nutrients and oxygen from blood. Blood is pumped from the heart and it travels around the body delivering oxygen and nutrients to the organs of the body and returns to the heart ready to be pumped back out again.

Blood pressure is needed so that the blood can travel from heart to other organs and muscles.

An adult has around five liters of blood that circulates around the body approximately once every minute. Blood pressure is the force of the blood pushing against the walls of those arteries.

Each times the heart beats (about 60-70 times a minute at rest), it pumps out blood into the arteries. Blood pressure monitoring is an important indicator of a wearer’s cardiovascular status.

Many devices allow blood pressure to be measured by manual or digital sphygmomanometer systems that utilize an inflatable cuff applied to a person’s arm.

The blood pressure is at its greatest when the heart contracts and is pumping the blood. This is called systolic pressure.

When the heart is at rest, in between beats, the blood pressure falls. This is the diastolic pressure.

When blood pressure stays too high for too long, it can damage the blood vessels. Organs such as kidneys, heart, brain and eyes can be affected.

High blood pressure is the leading risk factor for heart failure. It also increases the risk later for atherosclerosis or hardening of the arteries.
What is meant by blood pressure?