Transport in Animals Flashcards
Why are specialised transport systems needed in animals?
Maintain metabolic demands, small SA:V, transport of necessary molecules like hormones, removal of waste products like carbon dioxide
What are the different types of circulatory systems?
Open circulatory systems and closed circulatory systems (single and double)
What are the features most circulatory systems have in common?
Liquid transport medium (blood), vessels that carry the transport medium, pumping mechanism to move the fluid around the system
What is an open circulatory system?
When there are very few vessels in a system that pumps blood directly into a body cavity of an organism
How do open circulatory systems work?
The blood in the body cavity is transported under a low pressure, comes into contact with cells and tissues for gas exchange etc, the blood returns to the heart through an open ended vessel
Name some organisms that may have an open circulatory system
Invertebrates, some insects, some molluscs, arthropods
What is a closed circulatory system?
Blood is enclosed in vessels and does not come into direct contact with cells and tissues. Blood is pumped under high pressure and exchanges substances via diffusion before returning to the heart
What are single closed circulatory systems?
Blood only travels through the heart once for a complete circulation of the body
How do single closed circulatory systems work?
Blood passes through 2 sets of capillaries before it enters the heart; the first set exchanges oxygen and carbon dioxide (from respiratory system) and the second substances are exchanged between all the other organs in the body. This happens at a low pressure so therefore is very slow
Name some examples of what organisms may have a single closed circulatory system
Fish and annelid worms
How is the single closed circulatory system different in fish?
They have an efficient respiratory system because they have countercurrent gas exchanged systems that allow the gills to absorb a lot of oxygen. They also do not have to maintain their body temperature or support their body against gravity, which decreases metabolic demand
What are double closed circulatory systems?
Blood travels through two separate circulations; to the lungs and to the rest of the body
How do double closed circulatory systems work?
Blood is pumped to the lungs to load oxygen and unload carbon dioxide, blood is the pumped back to the heart, then pumped to the rest of the body to transport oxygen and other substances to organs, tissues and cells, then pumped back to the heart for a complete circulation. Each circuit only passes through one capillary network at a high pressure to maintain a high blood flow
Name some examples of what organisms may have a double closed circulatory system
Birds and most mammals
What are the components present in blood vessels?
Elastic fibers, smooth muscle and collagen
What is the advantage of having elastic fibers in blood vessels?
Able to stretch and recoil for flexibility
What is the advantage of having smooth muscle in blood vessels?
Contraction and relaxation changes size of lumen
What is the advantage of having collagen in blood vessels?
Provides structural support to maintain volume/shape of the vessel
What are arteries?
Vessels that carry oxygenated blood away from the heart (A for Away), EXCEPT the pulmonary artery and the umbilical artery. Blood in the arteries is under a higher pressure than blood in the veins
What are arterioles?
Link arteries with capillaries. They have more smooth muscle and less elastic fibers, due to the decreased pressure but also controls the volume of blood going into the capillary bed
What are capillaries?
Microscopic blood vessels that link arterioles with venules. Lumen is so small that red blood cells have to travel single file slowly, which allows substances to be exchanged through capillary walls via diffusion
How are capillaries adapted to their functions?
Large surface area for substances to diffuse over, slow movement of blood allows more time for substances to diffuse, one cell thick wall decreases diffusion distance
What are veins?
Vessels that carry deoxygenated blood towards the heart EXCEPT the pulmonary vein and the umbilical vein
What are venules?
Small veins that transport blood that transports deoxygenated blood to larger veins then into the two main veins; the inferior and superior vena cava
What is the inferior vena cava?
Vessel that transports blood from the lower parts of the body
What is the superior vena cava?
Vessel that transports blood from the head and upper parts of the body
How do veins transport blood?
Lower pressure than arteries, no pulse, valves to prevent backflow, lots of collagen and a wide lumen for easy blood flow
How do valves assist the transport of blood in the veins?
Muscles act as a pump to squeeze blood against gravitational forces due to low pulse/blood pressure, hence prevent blood from flowing backwards
What is the function of blood?
Transport, defence, thermoregulation and maintaining pH of body fluids
What is the composition of blood?
55% plasma, 45% red blood cells and 1% buffy coat (white blood cells and platelets)
What is plasma?
Yellow liquid that acts as a transport medium for water, dissolved minerals, proteins, amino acids, hormones, urea etc
What are the proteins in plasma?
Albumin (maintaining osmotic potential), globulin (aid transport and the immune system) and fibrinogen (clotting)
What is oncotic pressure?
Tendency of water to move into the blood (about -3.3 kPa)
What direction does blood flow in the smaller blood vessels?
From arteriole to venule
Describe the oncotic pressure at the arteriole end
Net flow of water out of the blood; due to high hydrostatic pressure from artery
Describe the oncotic pressure at the venule end
Net flow of water into the blood; due to loss of pulse therefore decreased hydrostatic pressure
What is lymph?
Tissue fluid that has gone into ‘lymph capillaries’. Similar to plasma except it has less oxygen and fewer nutrients
How is lymph transported in the lymphatic system?
Lymph capillaries join up to form larger vessels, then muscles squeeze the lymph through valves to prevent backflow in the low pressure
What are lymphnodes?
Sections on the lymph vessels that produces lymphocytes (produce antibodies) and also intercept bacteria and other debris in the lymph (which are ingested by phagocytes)
How are erythrocytes specialised to transport oxygen?
Biconcave shape for a larger surface area for diffusion of gases and flexibility, no nuclei for more haemoglobin to carry oxygen molecules
What is the equation for the loose binding of oxygen to haemoglobin?
Hb + 4 O2 Hb(O2)4
reversible due to loose binding
How is oxygen transported from the lungs into the erthyrocytes?
- erythrocytes enter capillaries in lungs
- oxygen levels in red blood cells is low compared to alveoli, therefore making a steep concentration gradient
- oxygen binds to haemoglobin in red blood cells
- level of free oxygen molecules is still low so maintains steep concentration gradient
What is positive cooperation?
When an oxygen molecule binds to haemoglobin, it changes the quaternary structure of the protein so it is easier for the next oxygen molecule to bind to the protein
What is the Bohr effect?
As the proportion of carbon dioxide increases, oxygen is more easily given up from haemoglobin
What is the difference in fetal haemoglobin from adult haemoglobin?
Because the fetus is completely dependent on the mother for oxygen, fetal haemoglobin has a higher binding affinity for oxygen, therefore can remove oxygen from the maternal blood for respiration, cell growth etc
How is carbon dioxide transported?
5% dissolved in plasma, 10-20% combined with amino acids to form carbaminohaemoglobin, 75-85% converted into hydrogen carbonate ions in the cytoplasm of red blood cells
Describe the mechanism that transports the majority of carbon dioxide
- carbon dioxide then reacts with water to form carbonic acid, which then dissociates into hydrogen ions and hydrogen carbonate ions
- this is done with the enzyme carbonic anhydrase
- the hydrogen carbonate ions diffuse into the plasma as chloride ions diffuse into the red blood cell
- the hydrogen ions then bind to haemoglobin to form haemoglobinic acid to maintain pH
What is the chloride shift?
When chloride ions diffuse into the red blood cell to replace hydrogen carbonate ions to maintain electrical stability
Define ostium
Small opening or orifice
Define hemolymph
Circulating fluid in some invertebrates that is the equivalent of blood
Define hemocoel
the system of cavaities between organs of arthropods and molluscs which the liquid transport medium circulates
What is the function of the blood?
Transport/removal of oxygen/carbon dioxide, digested food from small intestine, removal of nitrogenous waste products, hormones for cell-to-cell signaling, glucose from storage compounds, platelets and antibodies
