Heart Lab Flashcards
Difference between human and sheep heart
- Sheep has 3 vena cava’s - left anterior (smaller)
- left posterior
- right anterior (larger))
What separates the 3 vena cava?
Fat pads
Left and right anterior vena cava drain:
Head and forelegs
Ventral view of sheep heart:
- Ventral interventricular sulcus is on 45 degree angle
- Aorta is to the sheep’s left (our right)
- pulmonary trunk is the most ventral
- ventral side is rounder than the flatter dorsal side due to the spine
- ligamentum arteriosum is only visible in ventral view
Dorsal view of sheep heart:
- Dorsal interventricular sulcus is straight
- More vessels in dorsal view
- flatter than ventral side
What colour is the atria?
Dark red
Great arteries appearance:
- Shrouded with fat
- Cream-coloured wall
- Pulmonary trunk is most ventral
What makes up the apex of the heart?
Left ventricle
Appearance of aorta
Large and white
Interaction between pulmonary trunk and aorta
They half twist around each other, reversing positions as they continue away from the heart
What is the ligamentum arteriosum?
- Remnant of ductus arteriosus
- Fibrous bridge
Brachiocephalic trunk:
Supplies the arm and the brain
Posterior vena cava drain:
Posterior of sheep
Cross-section of the base of the heart:
- Dorsal: Right ventricle opening and left ventricle opening
- Central: aorta
- Most-ventral: pulmonary trunk
Atria internal wall:
Smooth - allows for smooth laminar flow
Auricle internal wall:
Irregular due to bundles of muscle fibres crossing over like a woven basket.
They’re trabeculated
Function of trabeculae:
To aid contraction
What are the tendinous cords made of?
Fibrous connective tissue
What is in the RV but not in the LV?
Moderator band that crosses from the septum to the ventricular wall
What is the function of the moderator band:
Made of purkinje fibres, aids in conduction
When is the mitral valve open?
Ventricular filling and atrial contraction
When is the mitral valve closed?
Isovolumetric ventricular filling, ventricular ejection, and isovolumetric ventricular relaxation
Aortic valve open view
- Brachiocephalic trunk opening superior to valve flaps
- 3 valve cusps (semilunar shape)
- 2 coronary ostia (openings to coronary arteries) just behind valve flaps
Where do cardiac veins drain into
Left anterior vena cava
Fossa ovalis
- remnant structure of foreman ovale
- Between right and left atrium, interatrial septum
- translucent
What happens when the papillary muscles rupture?
Inlet valves can no longer close; as the tension the papillary muscle provided to keep the chordae teninae tight is gone so the flaps shoot upwards when ventricular pressure exceeds atrial pressure
What could cause a rupture of the papillary muscles?
- Myocardial infarction
- Bacterial or viral infection
- Ischemia
Why don’t the outlet valves need chordae tendinae?
No place to attach
They use their cup/pocket shape structure to be closed via the pressure of blood
Their shape gives strength
What did the foramen ovale do?
- Let blood flow from RA to LA because fetus had no need for pulmonary circuit as placenta of mother supplied oxygenated blood
- flap is on the left side
- in fetus the pressure is opposite
What did the ductus arteriosus do?
Allowed a shunt of blood to pass from the pulmonary trunk to the aorta, again because fetus has no need for pulmonary circuit.
What causes closure of foramen ovale?
After birth the left side pressure increases and as the RA starts being used and blood goes to the lungs pressure decreases, forcing th valve closed.
Connective tissue growth seals the flap
What causes closure of ductus arteriosus?
Smooth muscle constriction after birth
What happens if ductus arteriosus doesn’t close
- The shunt bridge is called patent
- shunt of blood from the aorta to the pulmonary trunk (as pressure gradients reverse after birth)
- Volume reaching the lung increases
- if this occurs for too long we get hypertopy of right side leading to eventual reversal of flow
- greater blood flow to the lungs than to the systemic circuit
In the sheep heart, blood that enters the coronary arteries has just passed through the:
aortic valve
Compare the left side of the sheep heart with the right
- aortic valve - pulmonary valve
- mitral valve - tricuspid valve
- left and right pulmonary veins - right anterior, left anterior, and posterior vena cavae)
- thick-walled ventricle - thin-walled ventricle
Cardiac veins drain into the _____, their openings are very small, but they can be found by slitting open lengthwise the small left anterior vena cava and searching inside the wall of the vessel
right atrium
What is in the right atrium and close to the interatrial septum
Fossa ovalis
What is a fibrous bridge linking the pulmonary trunk to the aorta
Ligamentum arteriosum
Traversing the right ventricle from wall to wall is a slender bridge that is made of muscle, not connective tissue.
It has no mechanical function in the action of the heart and actually contains modified cardiac muscle fibers (Purkinje fibers)
Moderator band
The tricuspid valve gets what sort of blood?
Deoxygenated
The pulmonary valve gets what sort of blood?
Deoxygenated
The mitral valve gets what sort of blood?
oxygenated
The aortic valves get what sort of blood
oxygenated
What do papillary muscles do during systole
contract
The foramen ovale of the fetal heart is a hole in the ____ septum. It allows blood to cross from the ____ atrium to the ___. It has a flap valve on the ___ side of the septum
Interatrial
right
left
left
The ligamentum arteriosum is a remnant of a large fetal vessel called the ____ ____. This vessel carries blood from the ____ ____ to the ____
Ductus arteriosus
Pulmonary trunk
aorta
If the ductus arteriosus remains open after birth, the result would be a large shunt of blood from the ____ to the ____ ___.
In that case, the volume of blood reaching the lungs would be _____ than normal
aorta
pulmonary trunk
larger
During your dissection of the sheep’s heart, you used scissors to remove the apex of the heart.
Among the structures cut with the scissors were the:
Papillary muscles
In the sheep heart, one of the four heart valves has only two flaps or cusps.
When closed this valve prevents blood flow from:
the left ventricle to the left atrium
A chamber of the sheep’s heart is entered by three thin-walled vessels of unequal size.
The chamber has a valve at its outlet but no inlet valve.
The wall of the chamber is partly smooth and partly trabeculated.
When alive, the blood in the chamber would be a dark red/blue in colours.
This chamber is the:
right atrium
Which structure is made of white fibrous CT
chordae tendinae
interventricular septum has
cardiac muscle
Chordae tendinae has:
dense regular fibrous connective tissue
Auricles have:
cardiac muscle
Moderator band has:
modified cardiac muscle
Pericardium, out to in layers
fibrous pericardium
parietal pericardium
serous fluid
visceral/epicardium pericardium
Heart wall layers
epicardium
myocardium
endocardium
For blood to enter either atrium, what must the vessels/atrium do to ensure the filling of the atrium?
the atrium pressure must be below 5/8mmHg
Right ventricle
- pressure range
- wall thickness
2-27mmHg
Thin wall
Left ventricle
- pressure range
- wall thickness
5-120mmHg (5x as RV)
3x thicker than RV
What has no mechanical function in the heart?
The moderator band
It has no mechanical function in the action of the heart, and actually contains modified cardiac muscles (Purkinje fibers) which are part of the heart’s conduction system.
How many heart sounds?
Two, one from the atrioventricular valves and the 2nd one from the semilunar valves
Which heart sound does the tricuspid valve contribute to?
first: when the tricuspid valve closes, the first heart sound is made
The semilunar valve has _ leaflets
3
When is the mitral valve open?
ventricular relaxation
When is the mitral valve active?
During systole when it’s contracting
When is the aortic valve open?
during ventricular contraction or systole
Which heart sound does the aortic valve contribute to?
The second one
What is the first division of the aorta?
The coronary arteries
Peak pressure in the aorta:
120 mmHg (lowest 80 mmHg)
Is there coronary Ostia in the pulmonary trunk?
No, only in the aortic valve
The posterior end of a sheep is equivalent to the _____ or ____ surface of a human.
Inferior or caudal
The dorsal surface of a sheep is equivalent to the _____ or ____ surface of a human.
posterior or dorsal
The anterior surface of a sheep is equivalent to the _____ or ____ surface of a human.
superior or cranial
The ventral surface of a sheep is equivalent to the _____ or ____ surface of a human.
anterior or ventral
