The Heart Flashcards
3 major structural components of the CVS
Heart, Blood, Blood vessesl
2 circuits of the CVS
Pulmonary and systemic
3 layers of the pericardium
Fibrous pericardium
Parietal layer of serous pericardium
Visceral layer of serous pericardium
What is the pericardial cavity
A space between both serous pericardium which contains a serous fluid which reduces friction between the heart and the outer wall of the pericardial sac
3 layers of the heart wall
Epicardium = outermost layer which consists of visceral serous pericardium as well as other connective tissue Myocardium = middle layer which contains cardiac tissue and is the contractile layer Endocardium = innermost layer consisting of simple squamous epithelium on a thin layer of connective tissue
Functions of the papillary muscles and chordae tendineae
Prevent the valves from being pushed back to the atria, located within ventricles
Muscles relaxed and tendinae slack when valves open
Diastole vs systole
Diastole = ventricular relaxation (AV valves open, semilunar closed)
Systole = contraction (AV valves close, semilunar open)
Major sulci of the heart
Atrioventricular, anterior interventricular and posterior interventricular
These contain adipose tissue and blood vessels (Fat cushions but too much is bad)
Steps in the cardiac conduction system
- SA node excites
- Signal travels to the AV node and pauses for 0.1 seconds (allowing time for the atria to contract first)
- The signal travels along the AV bundle (bundle of His) and through to the left and right bundle branches
- The signal travels to the ventricles via the Purkinje fibres (subendocardial conducting network)
- Purkinje fibres spread signal to allow for rapid contraction of ventricles
Where are Purkinje fibres located and why are they directed superiorly?
Located between endocardium and myocardium
Directed superiorly so that heart contracts from bottom up (allows all blood to leave the heart)
Innervation of the heart
Parasympathetic (vagus nerve) decreases HR and innervates the SA, AV nodes and coronary arteries
Sympathetic (sympathetic trunk) increases HR and strength of cardiac contraction. Innervates the SA, AV nodes, coronary arteries and cardiac musculature
When do heart sounds occur?
Closing of AV valves (lub)
Closing of semilunar salves (dub)
What is atrial fibrillation (Afib)?
Irregular and rapid heart beat caused by extra electrical impulses disrupting SA node activity. Results in chaotic atrial contractions at faster rates than ventricles. Affects >5% of Australians 65+ and is treated with electrocardioversion, catheters, pacemakers
3 types of arteries
- Elastic arteries (conducting): Largest, low resistance, near the heart; High in elastin (tunica media)- stretchy; Allows large pressure surges from the heart
- Muscular arteries (distribution): Distal, supply groups of organs; Tunica media is thicker relative to lumen; Smooth muscle sandwiched between 2 elastin layers; Muscular layer regulates blood flow to organs
- Arterioles: Smallest arteries, lead to capillary beds; Thin tunica media of smooth muscle cells; Contraction/relaxation regulated via local signals or sympathetic nervous system
3 types of capillaries
Continuous- most common, least permeable
Fenestrated- have pores for high exchange rates
Sinusoid- very leaky for high exchange of large molecules
