How did the heart evolve?
-No sinus venosus (becomes buried in the wall of the right ventricle to become the sinoatrial node)
-2 atria (left and right), 2 ventricles (left and right) to allow for separation of oxygenated and deoxygenated blood. This eliminates the mixing of blood
What is the definition of aortic arch?
Curved blood vessel that supplies blood to the gills for gas exchange (in fish)
How many aortic arches does the archaic (or basic) plan consist of?
Which aortic arches are missing in fish?
I and II
Why is aortic arch I missing in fish?
Because it corresponds to the mandibular which becomes the jaws, so you don't need much blood flow.
Why is aortic arch II missing in fish?
Because aortic arch II corresponds with jaw suspension, so the blood supply is not required because there are no longer gills
How does aortic arch II differ in sharks?
The afferent portion is still there because sharks have spiracles, so there still needs to be some blood supply
Why are all the aortic arches split in fish?
Because of the development of gills. The gills require space which gives rise to the afferent bronchial artery (to the gills) and the efferent bronchial artery (away from the gills)
Which aortic arches are missing in the lungfish?
Only aortic arch I
Why is aortic arch I missing in the lungfish?
Mandibular developed into the jaws so there is no longer any need for a blood supply
Why is aortic arch II still present in lungfish?
Because they have a paleostylic condition for jaw suspension. This means that none of the gill arches are associated with the skull, so there still needs to be a blood supply.
Why don't aortic arches III and IV supply blood to the gills in lungfish?
Why does the dorsal portion of aortic arch VI branch in lungfish?
Because they have lungs, so the artery branches to supply blood to the lungs.
How is blood flow diverted when the lungfish is in water?
There is a constriction in the vessel that goes to the lungs and aortic arch III and IV
How is blood flow diverted when the lungfish is on land?
Aortic arch II and V constrict as well as the dorsal portion of aortic arch VI
How does the heart of lungfish separate oxygenated blood from deoxygenated blood?
There is a modification in the heart where the sinus venous is shifted to the right side of the heart because of the two types of blood flowing through the heart. The right side of the heart is devoted to deoxygenated blood. The two atria are partially se
How does the frog heart separate oxygenated and deoxygenated blood?
One flap valve channels the deoxygenated blood to the skin. The flap valve creates a spiral channel which diverts the blood to where it needs to go. The sinus venosus is shifted to the right, so it only transports blood into the right atrium. There is sti
How do the frogs benefit from an undivided ventricle?
Blood vessels to the lungs constrict, so the blood is diverted to the rest of the body while diving.
Which aortic arches are missing in the frog?
I, II, V, dorsal part of aortic arch VI, and a portion of the dorsal aortic arch between arch III and IV (ductus caroticus)
Why is aortic arch I missing in frogs?
The mandibular arch is missing because it develops into the jaws which are attached by metautostylic jaw suspension
Why is aortic arch II missing in frogs?
Hyoid arch is missing because it becomes the columnella--> middle ear
Why is the ductus caroticus missing in frogs?
Because it diverts blood flow to the brain. Aortic arch III is now called the carotid artery
Why is aortic arch V missing in frogs?
there is no point of having two aortic arches taking blood to the same part of the body. By only having the aortic arch IV supplying the blood to the body, a higher blood pressure is created. This means that oxygen and nutrient delivery is improved which
Why is the dorsal part of aortic arch IV (ductus arteriosus) missing in frogs?
Diverts the blood only to the lungs, and no longer the entire body. The part that closes off is called the ductus arteriosus and the remaining branch of aortic arch VI is now called the pulmonary artery
How does the heart of the turtle separate oxygenated and deoxygenated blood?
They have a septum and a ventricle which provides partial separation of the two bloods. The conus arteriosus chamber has become subdivided into three vessels. Conus arteriosus keeps the blood completely separated.
How do turtles benefit from the incomplete separation of the ventricle?
When the ventricle contracts, the flap between the pulmonary trunk and left systemic artery retracts towards the septum, so they do not get as much mixing of the two bloods.
What are the differences between the aortic arches of reptiles and frogs? Why did these changes occur?
The systemic artery has split in two, one taking the blood to the left side of the body and the other to the right side of the body. The pulmonary trunk becomes its own separate connection. Everything has to go through the heart, there are no longer any c
What is the evolutionary error in the heart of the crocodiles?
The septum grew and connected in between the right and left systemic arteries instead of connecting between the pulmonary trunk and left systemic artery. The mistake is that the left side of the body can receive deoxygenated blood
How has the evolutionary error in the crocodile been corrected?
There is an opening between the right and left systemic arteries called the foramen of panizza. This corrects the error because the left ventricle is always more muscular than the right, so it pumps more forcefully which creates more pressure in the right
How does the crocodile divert blood flow during a dive?
What are the differences in the aortic arches of mammals and birds?
The left systemic is missing in birds and most of the right systemic is missing in mammals (except right subclavian artery)
What is the relevance to the differences in the aortic arches of mammals and birds?
That we have different ancestors
The bird and mammalian hearts are completely separated into a right and left side. Advantage?
There is now a dual pump (one for each type of blood). The dual pump creates more pressure on the left side so that blood can be pumped throughout the entire body, and less pressure on the right side so that blood can be pumped to the lungs.
Why do you want low pressure going to the lungs?
If you have too much pressure, you can have too much blood going to the lungs which can create issues. You also want low pressure so that gas exchange can occur. If there is too high of a pressure, the blood will be traveling through the vessels at too hi
Why do you need more pressure on the left side?
Because blood needs to travel throughout the whole body, and you need enough pressure in the glomerulus to push the blood through for filtration
What is the fate of the sinus venosus in birds and mammals?
In mammals: becomes miniaturized and incorporated in the right wall of the atrium to become the sinoatrial node.
In birds: becomes a projection of the wall of the right atrium.
What is the definition of rete?
Network of blood vessels. These vessels are parallel and long, and the blood that runs through them travels in opposite directions.
How is the oxygen in the swim bladder adjusted as the fish ascends?
When the fish descend, oxygen is added to the gas gland and swim bladder. As it goes deeper, the water column increases and puts pressure on the swim bladder, which may cause the swim bladder to collapse. The gas gland carries out anaerobic respiration to
How is the oxygen in the swim bladder adjusted as the fish descends?
When the fish ascends, the water column puts less pressure on the swim bladder, which then has a tendency to over expand. To avoid that, they release some oxygen from the swim bladder to the oval chamber. This chamber has sphincters that connect to the sw
What prevents the diffusion of oxygen from the swim bladder?
Guanine crystals in the wall of the swim bladder.
What is the role of the rete in fast swimming fish?
Temperature of the venule is higher than the blood in the arteriole which creates a gradient. The heat from the venule will enter the arteriole, which is then brought back to the core
What is the role of the rete in mammals?
The rete is located at the base of the brain and connected to the nasal passageway. It acts as a cooling system for the brain. The blood vessels in the nose are exposed to the cool air. When the mammal is breathing through its nose, it is breathing in the