Mass Transport in Animals Flashcards
What is mass transport?
The bulk movement of substances over large distances using a transport system, usually in a fluid medium.
Why do large organisms require a mass transport system?
Diffusion alone is too slow due to the small surface area to volume ratio, so an efficient transport system ensures a sufficient supply of oxygen and nutrients and removal of waste.
What are the main components of the mammalian circulatory system?
Heart, blood vessels (arteries, veins, capillaries), and blood.
Describe the structure of the human heart.
Four chambers: two atria (receive blood) and two ventricles (pump blood). Right side pumps deoxygenated blood to lungs, left side pumps oxygenated blood to body.
Why is the left ventricle thicker than the right?
The left ventricle needs to generate higher pressure to pump blood around the body, whereas the right ventricle only pumps blood to the lungs.
Describe the flow of blood through the heart.
Vena cava → right atrium → tricuspid valve → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → bicuspid (mitral) valve → left ventricle → aorta → body.
What are the four major blood vessels associated with the heart?
Vena cava (deoxygenated blood from body), pulmonary artery (deoxygenated blood to lungs), pulmonary vein (oxygenated blood from lungs), aorta (oxygenated blood to body).
How do atrioventricular (AV) valves function?
Prevent backflow of blood from ventricles to atria by closing when ventricular pressure is higher than atrial pressure.
How do semilunar valves function?
Prevent backflow of blood from arteries (aorta & pulmonary artery) into ventricles by closing when arterial pressure is higher than ventricular pressure.
What is the cardiac cycle?
The sequence of events in one complete heartbeat, consisting of atrial systole, ventricular systole, and diastole.
Describe atrial systole.
Atria contract, increasing pressure and forcing blood into the ventricles. AV valves open, semilunar valves closed.
Describe ventricular systole.
Ventricles contract, increasing pressure and forcing blood into arteries. AV valves close, semilunar valves open.
Describe diastole.
Heart relaxes, blood enters atria from veins, pressure drops, AV valves open, semilunar valves close.
What is cardiac output and how is it calculated?
The volume of blood pumped by the heart per minute. Cardiac output = heart rate × stroke volume.
What is the structure and function of arteries?
Thick muscular and elastic walls to withstand high pressure and maintain blood flow away from the heart. Small lumen, no valves.
What is the structure and function of veins?
Thin walls with valves to prevent backflow, carry blood at low pressure back to the heart. Large lumen reduces resistance.
What is the structure and function of capillaries?
One-cell thick walls for short diffusion distance, highly branched for large surface area, narrow diameter slows blood flow for exchange of substances.
What is tissue fluid and how is it formed?
Fluid surrounding cells, formed from plasma forced out of capillaries due to high hydrostatic pressure at the arterial end. Contains nutrients and oxygen.
How is tissue fluid returned to the blood?
At the venous end of the capillary, lower hydrostatic pressure and higher osmotic pressure cause tissue fluid to be reabsorbed. Excess is drained by the lymphatic system.
What is haemoglobin?
A quaternary protein in red blood cells that transports oxygen by binding to it in a reversible reaction.
What is the structure of haemoglobin?
Four polypeptide chains, each with a haem group containing an iron ion (Fe²⁺) that binds to oxygen.
What is oxygen dissociation?
The release of oxygen from haemoglobin when it reaches tissues with a low partial pressure of oxygen.
What is an oxygen dissociation curve?
A graph showing the relationship between oxygen saturation of haemoglobin and partial pressure of oxygen (pO₂).
Why is the oxygen dissociation curve sigmoidal (S-shaped)?
Cooperative binding: as the first oxygen molecule binds, haemoglobin changes shape, making it easier for subsequent oxygen molecules to bind.
What is the Bohr effect?
Increased CO₂ lowers blood pH, reducing haemoglobin’s affinity for oxygen, causing oxygen to be released more readily in actively respiring tissues.
How does haemoglobin differ in different organisms?
Organisms in low-oxygen environments have haemoglobin with a higher affinity for oxygen (left-shifted curve), while organisms with high metabolic rates have haemoglobin with a lower affinity (right-shifted curve).
What are the main factors affecting oxygen transport?
Partial pressure of oxygen, carbon dioxide concentration (Bohr effect), and pH.
What is myoglobin and its role?
A protein in muscle cells with a higher affinity for oxygen than haemoglobin, acting as an oxygen store for when oxygen levels are very low.
What is the role of the lymphatic system in mass transport?
Collects excess tissue fluid and returns it to the bloodstream via the subclavian vein. Also plays a role in immune response.
