CVS- The Heart (8) Flashcards
What is the cardiovascular system?
> It provides the transport system that ensures blood continuously circulates to fulfil homeostatic need
Heart is transport system pump and blood vessels are the delivery route
Blood is transport medium and heart constantly propels oxygen, nutrients, wastes and other substances through blood vessels
What is the heart anatomy?
> Roughly size of fist
250-350g
Enclosed within mediastinum (medial cavity of thorax)- slightly left of midline, superior of diaphragm and anterior to vertebral column
What are the coverings of the heart (layers of the pericardium)?
1) Fibrous pericardium
2) Parietal pericardium
3) Serous pericardium
4) Visceral pericardium
What is the pericardium?
A double-walled sac that encloses the heart
What is the fibrous pericardium?
A superficial loose layer that protects the heart, anchors it to surrounding structures and prevent overfilling of heart with blood
What is the parietal pericardium?
> Lines the internal surface of the fibrous pericardium
At superior margin of heart, it attaches to the large arteries exiting the heart, then turns inferiorly and continues over the external heart surface as the visceral layer.
What is the serous pericardium?
> Thin, slippery, 2-layer serous membrane that forms a closed sac around the heart
What is the visceral layer?
> Also called epicardium
What is the pericardial cavity?
> Contains film of serous fluid
The serous membranes that are lubricated by the fluid glide smoothly past each other which allows the heart to work in a relatively-free friction environment
What is pericarditis?
Inflammation of the pericardium which roughens the serous membranes so when the heart beats it rubs against the sac, causing pain.
What are the 3 layers of the heart wall?
Epicardium
Myocardium
Endocardium
What is the myocardium?
> Composed of specialised cardiac muscles found only in the heart
Not under voluntary control
Forms the bulk of the heart and is the layer that contracts
Branching cardiac muscle cells are connected to one another by crisscrossing connective tissue fibres, arranged in spiral/circular bundles
These bundles link the whole heart together
The connective tissue forms the ‘fibrous skeleton of the heart’ which reinforces the myocardium and anchors the cardiac muscle fibres
The network of collagen and elastic fibres is thicker in some areas e.g. where vessels leave the heart and around the heart valves- without this, vessels and valves may become stretched due to continuous pressure of blood pumping through them
Connective tissue isn’t electrically excitable so the fibrous skeleton limits the spread of action potentials across the heart
What is the endocardium?
> Glistening white sheet of squamous endothelium resting on a thin connective tissue layer
On the inner myocardial surface, it lines the heart chambers and covers the fibrous skeleton of the valves
It is continuous with the endothelial linings of the blood vessels entering and leaving the heart.
What is the epicardium?
> The visceral layer of the heart
What is the pulmonary circulation loop?- part 1
> Happens on the right side of the heart
Right ventricle pumps deoxygenated blood through the pulmonary semilunar valve into pulmonary trunk (this splits off to form the left and right pulmonary arteries)
Blood goes through pulmonary artery into lungs where it can be oxygenated and loses co2.
blood moves back into the heart by pulmonary veins into the left atria (area of lowest pressure).
What is the systemic loop?- part 2
> Happens on the left side of the heart
Left atrium contracts, increasing pressure so the blood moves through the mitral valve, into the left ventricle
Left ventricle contracts, increasing pressure so blood moves through the aortic semilunar valve into the aorta, sending blood to the rest of the body (transported by smaller systemic arteries).
Part 3
> Deoxygenated blood enters heart by superior vena cava and inferior vena cava into right atrium
Right atrium contracts, forcing blood through the tricuspid valve into the right ventricle