Unit 1 - CV System The Heart PART C Flashcards
Why is a hydraulic pump required?
In order to sustain the pressure gradients needed to create the blood flow necessary to transport material (nutrients, gases, wastes, etc.) throughout the body
The heart is a fascinating organ in that begins beating after only…
3-6 weeks after fertilization
It will beat on average ______ times before we die
3 billion
Even when the heart is removed from the body, it can…
continue to beat on its own, without any need for nervous stimulation
Where does the heart lie?
in the center of the thorax, sandwiched b/t the lungs
Must contract from the _____ so that blood is squeezed out of the ____
BOTTOM UP
TOP
List the 4 features of the heart structure?
a. Four chambers
b. Walls of each chamber are composed of 3 layers
c. Pericardial sac
d. Heart Valves
What are the 4 chambers?
i. Left and right atria
ii. Left and right ventricles
What are the 3 layers that walls of each chamber are composed of?
i. Endocardium
ii. Myocardium
iii. Epicardium (= visceral pericardium)
Endocardium
inner epithelial lining of the heart (continuous with lining of blood vessels)
Myocardium
- cardiac muscle cells joined together by intercalated disks that contain gap junctions that allow ions to flow directly between cells (electrical coupling)
- 99% of cells are normal contractile cells
- 1% of cells are non-contractile cells referred to as “autorhythmic cells” that form a network called the conduction system.
____ of cells are normal contractile cells
99%
____ of cells are non-contractile cells referred to as “_________” that form a network called the ___________.
1%
autorhythmic cells
conduction system
Cardiac muscle cells contract…
without innervention
Epicardium (= visceral pericardium)
- epithelial lining covering the outer surface of the heart
1st, ____ contract together, then the _____ contract together
ATRIA
VENTRICLES
“Autorhythmic cells”
form a network called the conduction system
- specialized to generate APs spontaneously
- has a special ability (specialized myocardial cells) to contract without any outside signals
- AKA pacemakers b/c they set the rate of the heartbeat
- don’t contribute to the contractile force of the heart
Surrounding and protecting the heart =
Pericardial sac
Where is the pericardial sac formed from?
formed from parietal pericardium fused to the fibrous pericardium (thick layer of connective tissue)
What does the pericardial sac prevent?
Prevents overdistension of the heart and anchors it to surrounding structures
Where is the pericardial cavity space?
between pericardial sac and epicardium
What does the pericardial cavity space contain?
contains serous fluid that reduces the friction resulting from contractions
Heart Valves
passive unidirectional valves (open in response to
changes in pressure) that PREVENT the backflow of blood from the ventricles to the atria or from the large vessels to the ventricles.
What do heart valves open in response to?
open in response to changes in pressure
What are the 2 kinds of heart valves?
i. Atrioventricular valves (between atria and ventricles)
ii. Semilunar valves (between ventricles and larger arteries)
Where are the Atrioventricular valves located?
between atria and ventricles
What are the 2 types of Atrioventricular valves (AV)?
- TRIcuspid valve
- BIcuspid valve
Where is the TRIcuspid valve located?
between right atrium and right ventricle
Where is the BIcuspid valve located?
between left atrium and left ventricle
For Atrioventricular valves, ____ pressure in the ventricles due to ventricular ________ CLOSES them
HIGH
CONTRACTION
*when a ventricle contracts, blood pushes against the bottom side of its AV valve & forces it upward into a closed position
For Atrioventricular valves, when ventricles _____, pressure in the ventricles falls below that in the atria and the valves ___.
RELAX
OPEN
Where are the Semilunar valves located?
between ventricles and larger arteries
What are the 2 types of Semilunar valves?
- aortic semilunar valve
- pulmonary semilunar valve
Where is the aortic semilunar valve located?
between left ventricle and the aorta
Where is the pulmonary semilunar valve located?
between right ventricle and pulmonary trunk
The Semilunar valves…
DON’T need connective tendons as the AV valves do
For Semilunar valves, HIGH pressure in the ventricles due to ventricular ________ _____ them
CONTRACTION
OPENS
For Semilunar valves, when the ventricles RELAX, pressure in the ventricles ____ _____ that in the
large vessels, and the HIGHER pressure in the aorta/pulmonary trunk _____ the semilunar valves.
FALLS BELOW
CLOSES
During ventricular CONSTRICTION, the ____ _____ remain ______ to…
AV VALVES
CLOSED
PREVENT BLOOD FLOW BACKWARD INTO THE ATRIA
During ventricular RELAXATION, the ______ ______…
SEMILUNAR VALVES
PREVENTS BLOOD THAT HAS ENTERED THE ARTERIES FROM FLOWING BACK INTO THE VENTRICLES
What is the Chordae tendineae and the Papillary muscles?
Chordae tendineae:
- collagenous tendons
- AV valves connects to this
- prevent valve from being pushed back into the atrium (if it fails, prolapse is the result)
Papillary muscles:
- provide stability for the chordae
Fibrous skeleton
4 fibrous CONNECTIVE TISSUE RINGS that surround the 4 heart valves
What do the Fibrous skeleton do?
i. Prevent collapse of valve openings.
ii. Physically and electrically separate atria from the ventricles, allowing atria to contract as a unit to push blood down into ventricles, and allow ventricles to contract as a unit to push blood upwards into the major blood vessels (aorta and pulmonary trunk/arteries).
- acts as an electrical insulator - blocking most transmission of electrical signals b/t the atria & the ventricles
