Opercular Pump Essay

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Opercular pumping is a mechanism utilized by certain fish for gas exchange. An opercular pump is used to pump water through the gills in an almost continuous unidirectional flow (SHSU). A dual pump is used in tandem in order to drive the unidirectional flow, both a buccal cavity and opercular cavity work simultaneously. The oral valve along the buccal cavity opens, allowing an influx of water. This influx of water causes an expansion of the opercular cavity, dropping the pressure (Hall). Water then enters into the opercular cavity and flows out due to opercular cavity compression. This compression pumps water out which leaves fresh air in the buccal cavity to be brought to the lungs for respiration. Lungfish utilize a different method of…show more content…
π is equal to the osmotic pressure, V is equal to the cell volume and B is the intracellular solids (Hall). Ponder’s R value is the ratio of intracellular solvent volume to the water in its environment; R=(Vi -b)/W. These two equations are related because Ponder’s R value is a measure of how much of an osmometer a cell is while the van’t Hoff relation shows what the osmotic pressure is, both inside and outside the cell. Overall cell membrane permeability can be measured by Ponder’s R value while the osmotic pressure differentials between the external environment and the internal environment are seen with the van’t Hoff relation (Hall). Cells evolved to become great osmometers, but not perfect osmometers, in order to provide a way for solutes to move along permeable membranes. The van’t Hoff relation permits organisms to live in environments of varying osmolarity because regulating solute concentration within a cell can increase or decrease the cell’s affinity for osmosis (Darnell et al). Ponder’s R value, on the other hand, shows how a cell can never become a perfect osmometer. If a cell could become a perfect osmometer, it could cause cell lysis or shrinkage of the cell (Hall). The avoidance of perfect osmometry can be seen within the human erythrocyte as a small portion of cell water will not take part in an osmotic exchange due to tonicity within its…show more content…
Most reptiles have ventricles that are mostly separated, but still allow right to left shunting of the blood. Crocodiles have ventricles that are completely separated, but can still shunt blood between the pulmonary and systemic circuits (Axellson, Franklin). This shunting can be completed using the foramen of Panizza, which allows and regulates blood flow from either the left or right ventricle into the left or right aorta. Blood flows from the left ventricle to the right aorta, dorsal aorta, right subclavian artery and the common carotid artery. The right ventricle moves blood into the pulmonary trunk which then separates blood into the left and right pulmonary arteries (Axellson, Franklin). During diving, crocodiles develop a slight bradycardia and develop a right to left shunt once right ventricular pressure rises to a certain threshold. Resting rates of oxygen consumption are maintained and muscular lactate levels do not increase (Grigg). This ability to dive for extended periods of time is made possible by right to left shunting by way of the foramen of Panizza, in addition to the ability to maintain muscular lactate levels. Crocodilian hearts have the ability to keep oxygenated and deoxygenated blood within the heart. Blood pressures are also kept higher in the systemic circuit than the pulmonary circuit (Grigg). These heart adaptations are not seen in other reptiles, but rather in mammalian and avian
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