Question

1. Describe the capillary exchange of gases, nutrients and waste in both pulmonary and systemic capillaries.

2. Trace a drop of blood through the cardiovascular system using the appropriate terms, start and end at the same location.

Answer 1

1. Capillary exchange of nutrition, gases and waste occurs through three mechanism :

- Diffusion : diffusion allows small molecules to move across the capillary membrane such as glucose through pores in the capillary walls.

2. Transcytosis : movement of large molecules takes place through transcytosis.The lipid vesicles in the endothelial cells of capillaries endocytose the molecule and transports it through exocytosis.

3. Bulk transport : small lipid insoluble molecules transport across the capillary wall through bulk transport with the help of vesicles.
The capillaries exchange depends on four Starling forces : capillary hydrostatic pressure, interstitial hydrostatic pressure, capillary colloidal osmotic pressure and interstitial colloidal osmotic pressure.
2. Flow of blood through cardiovascular system :

inferior and superior vena cava drains the deoxblood into the the right atrium. The blood passes from right atrium to right ventricle through tricuspid valve. The blood then passes to pulmonary artery through pulmonary valve. The blood then enters the lungs where it is oxygenated. The blood is returned to the heart through pulmonary vein. The vein drains the blood into left atrium. Through the left atrium blood passes to the left ventricle through bicuspid valve. The blood from left ventricle is pumped into the aorta through aortic valve. The aorta pumps the blood to different arterial branches which takes the blood to different body parts and supply oxygen. The deoxygenated blood containing wastes and metabolites is collected by the venous system of body. All the veins from lower half of body drains into inferior vena cava while veins from upper half of body drains into superior vena cava.