Cardiac histology Flashcards
What are the receiving chambers of the heart?
The two atria
The pumps or discharging chambers are what?
Ventricles
What side of the heart pumps blood out to the body? (systemic circuit)
The left side
Which atrium receives oxygenated blood?
The left atrium
Which side of the heart is for the pulmonary circuit?
The right side
Which atrium receives deoxygenated blood?
The right atrium
The heart has a fibrous skeleton- what surrounds the valves and what connects the rings?
Four fibrous rings surround the valve orifices
Two fibrous trigones connect the rings
What is the epicardium?
The outer; visceral layer of the serous pericardium
What is the myocardium?
The middle layer, primarily composed of cardiac muscle
Which layer of the heart wall contains the fibrous skeleton of the heart?
The mycardium
What is the endocardium and how many components are in it?
It is the inner layer with three components
What are the three components of the endocardium and what are they made up of?
- Endothelial cell layer- inner layer
- Subendothelial layer-Underlying layer of dense CT
- Subendocardial layer- CT layer
Why are the walls of the left ventricle thicker than those of the right ventricle?
Because the left ventricle sends blood to the systemic circuit (the entire body) and has to overcome much more friction than the pulmonary circuit of the right side
Is the heart sitting in a sac?
Yes
What is the purpose of the atrioventricular valves?
Prevent backflow into the atria
What are the two atrioventricular valves?
Tricuspid and bicuspid (mitrial) valves
What are the two semilunar valves?
Aortic semilunar and pulmonary semilunar valves
What is the purpose of the two semilunar valves?
To prevent backflow into the ventricles.
T/F both ventricles have the same amount of blood being push out of the ventricles?
Truth
Are there valves associated with entrances of venae cavae, coronary sinus, and pulmonary veins into the heart?
Nope
T/F Heart valves enforce one way blood flow through the heart and open/close in response to pressure changes.
True
What is the composition of heart valves?
connective tissue overlying endocardium
What are the three layers of the heart valves?
Spongiosa
Fibrosa
Ventricularis
The tricuspid valve is in on what side of the heart?
The right side
The bicuspid/mitral valve is on which side of the heart?
The left!
What is the spongiosa layer of the heart valve responsible for?
Shock absorber
What is the fibrosa layer of the heart valve for?
It is the core of the valve that contains fibrous extensions from the dense CT of the skeletal rings of the heart
What is the ventricular layer of the heart valve made of and where is it at?
Well, it’s dense CT with layers of elastic fibers- adjacent to the ventricular side of the valve
Which layer of the heart valve is thickest?
The fibrosa layer
What allows the cardiac muscle of the heart to depolarize and contract without impulses from the nervous system?
The intrinsic cardiac conduction system
Which node is the pacemaker of the heart?
The sinoatrial (SA) node
An impulse travels from the SA node to the AV node via what?
Internodal tracts/pathways
How long is the impulse delayed between SA and VA nodes and why?
0.1 seconds to allow the atria to contract so the heart doesn’t explode like a balloon as everything contracts at once
What is the only electrical connection between the atria and ventricles?
The atrioventricular bundle or bundle of His
Where are the right and left bundle branches of the atrioventricular bundle headed?
toward the apex of the heart through the interventricular septum
Where are the purkinje fibers headed?
They finish the pathway and head from the apex back up towards the atria
Describe the nodal cardiac cells.
Found in SA and AV nodes
They are modified cardiac muscle cells
Smaller than surrounding atrial contractile cardiac cells
Contain fewer myofibrils and lack intercalated disks
Describe purkinje fibers
Found in AV bundle, bundle branches, and subendothelial branches
Also are modified cardiac cells
Larger than surrounding ventricular contractile cardiac cells
Contain myofibrils at periphery of cell
Nuclei are round and larger than nuclei of regular cardiac fibers
Have associated intercalated discs
What are the three types of blood vessels?
Arteries
Capillaries
Veins
What do arteries do?
Carry blood away from the heart- oxygenated in systemic circuit, deoxygenated in pulmonary circuit
What is the smallest artery called?
Arteriole
What do capillaries do?
smallest of the blood vessels, thin wall- they all the exchange of materials between the blood and body tissues
What do veins do?
Carry blood towards the heart- oxygen poor blood in systemic circuit and oxygen rich blood in pulmonary circuit
What is the smallest vein called?
Venule
The walls of blood vessels, except the smallest, have three layers. What are they?
Tunica intima
Tunica media
Tunica externa
Tell me about the tunica externa.
In larger vessels this tunic contains a vasa vasorum and a nervi vascularis
Tell me about tunica media.
Contains rings of smooth muscle cells responsible for vasoconstriction and vasodilation- can contain elastin!
Tell me about tunica intima.
Has three parts- endothelium, basal lamina, subendothelial layer
In cross section ____ will appear more open while _____ will appear more flat.
Arteries
Veins
What is the thickest layer of arteries?
The tunica media
What is the thickest layer of veins?
Tunica externa
What do elastic/conducting arteries do?
These are the largest diameter arteries, they are elastic and are important in helping to propel blood onward while ventricles are relaxing- the elastic fibers function as a pressure reserve
What are muscular/distributing arteries?
Medium sized arteries- contain lots of smooth muscle- regulate blood flow to specific body regions- smooth muscle cells responsible for vasodilation/constriction
How big are elastic/conducting and muscular/distributing arteries?
Greater than 10mm
2-10 mm
Describe small arteries.
0.1mm-2mm in diameter and as many as 8 layers of smooth muscle in the tunic amedia
Describe arterioles.
Smallest artery diameter- 10-100 micrometers- only one or two layers of smooth muscle in the tunica media
Describe capillaries.
Smallest diameter of blood vessels.
Thin wall
Allows for exchange of materials
What are the three types of capillaries?
Continuous
Fenestrated
Discontinuous (sinusoidal)
Where are continuous capillaries found?
In muscles
Lungs
CNS
Do continuous capillaries have holes in their walls?
No- they have tight junctions
Are pinocytotic vessels or pericytes seen in continuous capillaries?
Yep
Where are fenestrated capillaries found?
In endocrine glands and at sites of fluid and metabolite absorption
Will you see pinocytotic vessels or pericytes in fenestrated capillaries?
Just pinocytotic vessels
Where are discontinuous (sinusoidal) capillaries found?
Liver, spleen and bone marrow
Which capillaries have the biggest holes in them?
Sinusoidal capillaries
The flow of blood from an arteriole through a capillary network to a postcapillary venule is called what? What is the functional unit called?
Microcirculation
Microcirculatory bed/microvascular bed
What are the two types of vessels in the capillary network?
True capillaries
Ateriorvenous anastomoses/shunts
What type of capillary has oval windows? Which type has irregular holes?
Fenestrated- ovals
Sinusoidal- irregular
If precapillary sphincters relax, more blood flows through which capillaries?
True capillaries
If precapillary sphincters constrict, where does more blood go?
The arteriovenous anastomoses to bypass the true capillaries
What are the four types of veins?
Venule
Small veins
Medium veins
Large veins
Venules receive blood from what?
What are the two types of venules?
Capillaries
Postcapillary venule
Muscular venule
Small veins receive blood from what?
Muscular venules
In which veins are all three layers present?
Medium and large veins
Most veins in the limbs have ___.
Valves
Valves in veins are really what?
Folds in the tunica intima
What do valves in veins do? What is their purpose?
Prevent backflow
