Anatomy of the Heart - Part 2 Flashcards
Describe the different valves of the heart
(larger valves in transverse image) Atrioventricular valves: separates atrium and ventricle. prevents blood flow returning to atria during ventricular contraction.
- right side: tricuspid valve
- left side - bicuspid (mitral) valve
(smaller valves in transverse pictures) Semilunar valves: controls flow from ventricles to outflow arteries. prevents blood returning to ventricles during filling (diastole)
- right side: pulmonary (semilunar) valve, 3 cusps
- left side - aortic (semilunar) valve, 3 cusps.
pushed open as blood flows out of heart and close as blood starts to back flow.
What are the two phases of the cardiac cycle?
Diastole:
- atrioventricular valves open
- blood coming into the heart, filling it. heart is relaxed
(ventricular) Systole:
- Atrioventricular valves closed
- ventricles are contracting and pressure increases in the chambers (closing the atrioventricular valves with the pressure, and then opening the semilunar valves as the pressure increases more)
What are the extra structures involved with the AV valves?
papillary muscles and chordae tendineae which are attached to the AV valve leaflet. these do NOT open the valve, they instead control the closing of the valve so that it doesn’t snap shut with the pressure of back flow and then give way under backflow pressure. kind of anchors the leaflet.
What are the arteries of the heart?
- Right coronary artery: originates at the base of the aorta (and is the first part of the systemic circulation, as the heart oxygenates itself first). runs epicardially (in the layer of the epicardium)
- Left coronary artery: propagates off a branch of the coronary aorta. runs epicardially as well and has two branches coming off it.
- Anterior interventricular artery: lies along the inter ventricular septum. is a branch of the left coronary artery
- Circumflex artery: curfumflexes the coronary of the heart. is another branch of the left coronary artery.
What are the veins of the heart?
- Small cardiac vein: right side of heart it drained primarily by this vein
- Great cardiac vein: left side of heart is drained priorly by this vein
- Coronary sinus: both of the above two veins drain into the coronary sinus where blood is then sent into the pulmonary system to be oxygenated
How does the size of capillaries relate to their function?
Capillaries are only wide enough to allow one gas carrying cell down them at a time so they can be as close to the wall as possible (for diffusion?).
Describe the structure of cardiac muscle cells
- Striated
- Short, branched cells
- One (or occasionally 2) nuclei/cell
- Central (oval shaped) nucleus
- Cytoplasmic organelles packed at the poles of nucleus
- Interconnected with neighbouring cells via intercalated disks (ICDs)
What are key defining factors of skeletal muscle cells when looking at images?
- Multiple nuclei and they are on the side (pushed to the periphery) of the muscle fibres
- Straight, long fibres (NOT branched)
- Not very many mitochondria (compared to cardiac muscle) as they only makes up 2% roughly of cell volume of this type of muscle
What are the key defining factors of the cardiac muscle cells when looking at images?
- One (or two) nuclei and they are in the middle of the muscle fibre
- Fibres are branched and not perfectly straight as they need to bend into branches at times
- Large amount of mitochondria because the heart needs so much oxygen for metabolism (20% of the volume of the cell is mitochondria)
- The cardiomyocytes have thicker areas too which represent the presence of intercalated disks (the darker vertical lines)
What are the different types of intercalated disks found in muscle?
- Adhesion belts: link actin to actin in the vertical portion. once cell contracting pulls on another, the force is transmitted by the pull
- Desmosomes: linking cytokeratin with cytokeratin keep the cells together during the pulling so they don’t come apart
- Gap junctions: are about communication. Ca2+ is released by one cell and then some also travels into the neighbouring cell through this type of junction, stimulating that cell to contract too. it is electrochemical communication in the horizontal portion
Describe the conduction system of the heart
- It has its own conduction pathways, this increases efficiency of heart pumping as it is extremely coordinated
- Its actions greatly increase the efficiency of heart pumping
- This system is responsible for the co-ordination of heart contraction and of atrioventricular valve action
- Autonomic nerves alter the rate of conduction impulse generation
Describe the conduction pathway in the heart in order from start to finish
- SA node (sinoatrial node)
- internal pathways (three of them)
- AV node (atrioventricular node)
- AV bundle
- R and L bundle branches
- Purkinje fibres
Conduction pathways are not nervous tissue but modified cardiac muscle!
Describe the traits of conduction cells
- (some) peripheral myofibrils
- central nucelus
- mitochondria, glycogen
- lots of gap junctions (for signalling), and less of the rest because not contracting so don’t need the extra hold btw cells
- makes up 1% of cardiac cells
Conduction cells were originally contractile cells but they eventually differentiate.
