exam 2 discussions
What would happen if a person with type B blood were given a transfusion of type O blood (packed RBCs)? Explain.
Type B contains the B antigen on its red blood cells, and the A antibody in its plasma. Those with type B blood may safely be transfused with type O blood. Type O has neither A nor B antigens on its red blood cells, but both A and B antibodies in its plasma.
Does more blood flow through the coronary arteries during ventricular diastole or ventricular systole? Explain. How is this affected by tachycardia?
More blood flows through the coronary arteries during diastole because the vessels are relaxed. During systole, the vessels are compressed. Tachycardia can affect this however. When the heart rate increases, there is less blood available to the myocardium causing insufficient blood supply.
What causes blood to flow through the heart and the heart valves to open and close? Explain using a specific valve example.
A pressure gradient causes the flow of blood through the heart. Blood flows from high pressure to an area of low pressure. Valves are also forces open and closed by pressure. When blood flows into the RA, the pressure increases making the tricuspid valve to open and the blood flows into the RV. After the atria contracts and the pressure in the RA continues to increase. Meanwhile the pulmonary valve has been closed during its relaxed state. As the pressure increases in the RV, the tricuspid valve closes and the pulmonary valves open allowing blood to flow into the pulmonary trunk. Once the RV contracts, then the pulmonary valve closes.
Why is the velocity of blood flow slower in capillaries than in arteries and veins? Of what benefit is a slow blood flow through capillaries?
Arteries divide into many capillaries and veins are made of many capillaries fusing together. When liquid goes from an area of little surface area and high pressure to an area with more surface area then the pressure drops. Slow blood flow through the capillaries allows for proficient gas exchange and diffusion.
What is autoregulation, and how does it differ in the systemic and pulmonic circulations? Explain in detail, including WHY this makes sense
Autoregulation ensures that correct amount of blood is delivered to match tissue's level of activity. There are two main types of local autoregulatory controls: myogenic mechanism and metabolic controls.
Why are valves more important in the veins of the arms and legs than in neck veins ? Explain in detail, including the three mechanisms that help maintain venous return to the heart.
Blood flow has to overcome gravity in the arms and legs. Venous valves prevent back flow in some veins.Smooth muscle in vein walls can contract under sympathetic nervous system stimulation to increase rate of venous return. In the skeletal muscle pump, skeletal muscles surrounding deeper veins of upper and lower limbs squeeze blood in veins and propel it upward towards the heart as they contract and relax. The respiratory pump helps propel blood through the thoracic and abdominal cavity veins. Driven by the rhythmic changes in pressure in the thoracic and abdominopelvic cavity caused by breathing. As we inhale, pressure increases and causes the blood to be moved upward. Veins expand and collect blood as we exhale.
Why does significant tachycardia have such a negative impact on cardiac efficiency? How does this affect coronary artery perfusion and ventricular efficiency?
During tachycardia the heart beats more per minute and does not develop significant tension. Therefore, it reduces stroke volume and cardiac output. The heart also does not have enough time to fill and contract at a normal level. This causes less output. Because the heart is contracting more, less profusion is happening. If the heart muscles do not get the blood supply they need then it will become inefficient.
After RBCs die, how are the components of hemoglobin recycled or excreted? What does this have to do with jaundice?
Erythrocytes become trapped in sinusoids of the spleen. Spleen macrophages digest RBC.Hemoglobin is broken down into amino acids, iron ions, and heme. Heme is first converted to waste product biliverdin. Biliverdin is converted further to bilirubin. Bilirubin is sent to the liver for excretion. If bile ducts are blocked or liver cannot absorb, process, or excrete bilirubin into the gut, circulating levels of bilirubin rise. Bilirubin will then diffuses into peripheral tissues, giving them a yellow color that is most apparent in the skin and over the sclera of eyes.
Explain why the shape of a mature RBC and the absence of a nucleus is so important with respect to its function.
RBC shape increases surface area of cell which allows diffusion of gas exchange across the surface to happen very quickly. The absence of a nucleus and other organelles makes it more flexible, stackable, and allows more room to carry hemoglobin. It also lacks a mitochondria which consumes oxygen. The fact that it is stackable makes it easier for RBC to flow through small vessels.
Which chamber of the heart has the thickest wall? Why? Explain in detail.
The left ventricle is the thickest chamber of the heart. The left ventricle pumps blood to the systemic circuit which supplies the body with blood and nutrients. Because the blood has to travel far, the left ventricle has to pump a high amount of pressure.
How does a deficit of plasma proteins affect capillary filtration and reabsorption? What about lymphatic blockage? Hypertension? Explain each in terms of their impact on capillary dynamics.
When there is not enough plasma proteins then the COP will be too low. Because COP is low means that the net filtration pressure is higher. When the hydrostatic pressure is higher than COP there is more filtration at the capillary bed than reabsorption which means that more water gets pushed out to the interstitial fluid and is retained there because there is not enough COP to pull it back in. In lymphatic blockage, the fluid pushed out arteriolar capillaries and not picked up by venous capillaries is picked up by the lymphatic system. If the lymphatic system is blocked then the excess fluid is going to stay in the tissue because it is unable to go in venous circulation. This causes localized edema. In hypertension, there is an increase in hydrostatic pressure which causes an increase in the pressure gradients that affects all vessels including capillaries. This increases the rate of filtration and the amount of fluid that leaves the capillary. This fluid may not have a chance to be reabsorbed and can potentially stay outside the capillary.
