Lecture 8 Flashcards
What are the two major challenges with a single-circuit circulatory system?
The oxygen problem (oxygen delivery to tissues) and the pressure problem (maintaining blood flow without damaging gills).
How does compact myocardium receive oxygen?
Through coronary arteries, which are necessary for maintaining aerobic performance in low oxygen and high temperatures.
What is the function of the pericardium?
It protects and contains the heart; includes parietal pericardium, visceral pericardium (epicardium), and myocardium.
Why is pressure highest before the gills in fish circulation?
Gills contain capillaries that create high resistance, requiring strong ventricular pressure to push blood through.
What equation explains the relationship between pressure, flow, and resistance?
ΔP=Q×R (Pressure difference = Flow × Resistance).
How do bony fish manage pressure pulses in circulation?
The bulbus arteriosus absorbs ventricular contraction pressure to ensure smooth blood flow.
How do elasmobranchs (sharks, rays) regulate circulation pressure?
The conus arteriosus increases contraction pressure, and the ventral aorta dampens the pulse.
What mechanisms assist venous return in vertebrates?
Skeletal muscle contraction, smooth muscle in veins, and in some cases, supplemental hearts (e.g., hagfish).
What is vis-a-tergo vs. vis-a-fronte in circulation?
Vis-a-tergo: Blood flow driven by force from behind.
Vis-a-fronte: Blood flow facilitated by suction from ventricular contraction.
What is the main advantage of a double-circuit circulatory system?
It separates pulmonary and systemic circulation, ensuring efficient oxygenation and high systemic pressure.
How do amphibians’ 3-chambered hearts function?
They have two atria and one ventricle, allowing partial separation of oxygenated and deoxygenated blood.
How do reptiles (except crocodilians) differ in circulation?
They have 3-chambered hearts with shunting mechanisms to control blood flow based on metabolic needs.
What is unique about crocodilian circulation?
They have a 4-chambered heart but can shunt blood away from the lungs during diving.
How does the mammalian fetal circulatory system bypass the lungs?
Through the foramen ovale, which allows blood to move between the atria.
What is the significance of high systemic pressure in terrestrial vertebrates?
It increases oxygen delivery to tissues but also requires mechanisms (e.g., lymphatic system) to manage fluid loss.
How do lungfish adapt to their bimodal breathing?
They have partially divided ventricles and can switch between gill and lung respiration.
Why do some amphibians use pulmocutaneous circulation?
They extract oxygen through both lungs and skin for greater flexibility in different environments.
Why do gas exchange organs require low pressure?
To allow sufficient time for diffusion and prevent capillary damage.
How does oxygen transport in the body follow the oxygen cascade?
Oxygen moves from the atmosphere → lungs/gills → blood → tissues → mitochondria, driven by partial pressure gradients.
How does atmospheric oxygen availability change with altitude?
While the proportion of oxygen remains constant (20.95%), its partial pressure decreases with lower atmospheric pressure.
