Download Name: _______GREG CROWTHER_______________

Laboratory 7: Vertebrate heart and aortic arches
Name: _______GREG CROWTHER_______________; Date: ___MAY 2015______
Other Group Members: ________JEFF JENSEN_______________________________________
Points: 3 points for general participation, 8 for the walk-throughs, and 9 points for the
specific questions marked below.
Shark arterial system
Do the afferent branchial arteries carry oxygenated or deoxygenated blood?
Deoxygenated blood.
Internal carotid artery. To what does this supply blood? Do you have this vessel?
 The internal carotid artery sends blood to the brain.
 Yes, humans have this vessel.
Hypobranchial artery. To what does this supply oxygen? Why is this necessary? [1 pt.]
 The hypobranchial artery sends oxygen to the heart.
 The heart is a muscle that requires energy to contract, and blood flowing through the
heart does not itself deliver oxygen (or other nutrients) to the muscle cells deep within
the heart’s walls.
Shark heart exterior
Sinus venosus. Does this appear to be a muscular structure? What is its role? Do you have
one? [2 pts.]
 The sinus venosus is not muscular.
 The sinus venosus is essentially a holding area for blood on the way into the heart.
 Humans do not have a full sinus venosus, though the sinoatrial node is an evolutionary
remnant of it.
Shark heart interior
Atrium. How many chambers does it contain? How is your atrium different? [1 pt.]
 The shark heart has only one atrium.
 The human atrium is different in that it is divided into two separate chambers.
Conus arteriosus and internal valves. What function do the valves serve?
They prevent back-flow of blood, thus helping the heart pump the blood efficiently.
The shark heart is encased in a cartilaginous box. How would contraction of the ventricle
help move blood from the sinus venosus into the atrium?
When the ventricle relaxes again, the negative pressure inside the expanding ventricle pulls
blood from the atrium, and the exit of this blood from the atrium pulls new blood into the
atrium.
BBIO352 – Principles of Anatomy and Physiology II – Spring 2015
Laboratory 7: Vertebrate heart and aortic arches
External features of the calf heart
Pulmonary trunk. Is this an artery or vein? Does it carry oxygenated or de-oxygenated
blood? [1 pt.]
The pulmonary trunk is an artery. It carries deoxygenated blood.
Does the calf have a ligamentum arteriosum, or is it a ductus arteriosus?
Most calves develop a ligamentum arteriosum shortly after birth, although most of the hearts
we dissected did not contain enough aorta and pulmonary artery to tell for sure.
Inside the calf’s right atrium
Tricuspid valve. What chambers does it lie between? [1 pt.]
The right atrium and right ventricle.
Interatrial septum. Does your calf heart interatrial septum contain a fossa ovalis, or is it a
foramen ovale?
A foramen ovale was expected in most calves, but you weren’t necessarily able to find it. Some
of you appeared to have a fossa ovalis (dimple in the wall).
Inside the calf’s left ventricle
How do the wall of the left and right ventricular walls compare? Which is thicker? What is
the functional significance of this? [1 pt.]
 The left ventricle’s wall is thicker, which is consistent with the left ventricle’s job to
generate high pressures in propelling the blood through the rest of the body.
 The right ventricle sends blood to the lungs, which cannot handle such high pressures.
Fetal circulation in the calf
How does oxygenated blood enter the heart in fetal mammals? Why is it useful to have a
shunt between the right and left atria? To where does the oxygenated blood entering the
heart go after leaving the right atrium? [2 pts.]
 Oxygenated blood enters the fetal heart from the vena cava after passing through the
placenta.
 The shunt is useful because it reduces the flow of blood to the pulmonary vessels. Since
the lungs are not yet functional, sending blood to them is pointless.
 From the right atrium, some of the blood gets shunted to the left atrium while some
moves into the right ventricle and then the pulmonary artery.
Is blood leaving the right ventricle high in oxygen, or low? Is it significant that the vessels
carrying oxygenated blood from the aorta to the head branch off before the ductus
arteriosus enters the aorta? Explain.
BBIO352 – Principles of Anatomy and Physiology II – Spring 2015
Laboratory 7: Vertebrate heart and aortic arches
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Blood leaving the right ventricle is of intermediate oxygen levels, being a mix of
oxygenated blood from the placenta and deoxygenated blood from the rest of the body.
Thanks to “hydrodynamic valving” (incomplete mixing of blood), the most oxygenated
blood (coming from the placenta) gets preferentially sent to the head before mixing
with the less oxygenated blood coming from the ductus arteriosus. This ensures that
the brain receives as much oxygen as possible.
Is the blood going to the body high in oxygen, low in oxygen, or mixed (i.e. intermediate)?
Mixed/intermediate.
At birth the lungs inflate and pulmonary resistance decreases. What effect do you think
this will have on blood flow through the ductus arteriosus? How will decreased pulmonary
resistance affect blood flow to the left atrium? How will this affect blood flow through the
foramen ovale? Will blood entering the left atrium be high or low in oxygen?
 Decreased pulmonary resistance will lower flow through the ductus arteriosus.
 Decreased pulmonary resistance will reduce flow from the right atrium to the left
atrium through the foramen ovale. Flow to the left atrium from the pulmonary veins
will increase, though.
 Blood entering the left atrium will now be high in oxygen.
BBIO352 – Principles of Anatomy and Physiology II – Spring 2015