3.1 Anatomy of Cardiac Muscle Flashcards
What separates the fibrous pericardium and the parietal pericardium
A layer of connective tissue
How can we subdivide the visceral serous pericardium from the parietal serous pericardium
Visceral pericardium is a single layer of mesothelium that sits on top of the epicardium
Why do some stains show a lighter area around the nucleus of cardiomyocytes in histological section?
- Other organelles surround the nucleus
- Endoplasmic reticulum, golgi body etc.
What type of junctions are in intercalated discs
- Adherens junctions (bind to actin in cytoskeleton)
- Gap junctions (made of conexins, allow APs to spread)
Describe the arrangement of heart muscles around the apex
They spiral down toward the apex
What are sarcomeres?
A single contractile unit of actin and myosin filaments
How long are sarcomeres?
2 micrometers
Where does the depolarization of a cardiomyocyte begin? What is the technical name for this?
- Begins in cell membrane
- AKA sarcolemma
What does “sarco” mean?
Meat
Summarise cardiomyocyte contraction
- Action potential depolarises sarcolemma
- Depolarization travels through the Transerve Tubules
- Calcium travels into cell
- Triggers release of calcium from sarcoplasmic reticulum
How is calcium returned to the sarcoplasmic reticulum during cardiac recovery?
ATP-dependent pumps
How is calcium removed back into the external environment around cardiomyocytes?
Sodium-calcium pump; sodium is pumped in, calcium is pumped out
What is a diad in a cardiomyocyte?
Join between sarcoplasmic reticulum and transverse tubule
What % volume of cardiomyocytes is mitochondria?
40%
Why do Purkinje fibres have more gap junctions than cardiomyocytes?
Because their job is to transport action potentials throughout the heart; they need to be able to transport ions quickly.
List two notable characteristics of heart valves
- Only consist of connective tissue
- They have no blood vessels
Name and describe the function of the three layers of heart valves
- Fibrosa (strong CT)
- Spongiosa (helps adapt to pressure change)
- Ventricularis (elastic fibres; enables bending)
What is the fibrosa of heart valves made of?
Dense connective tissue
What is the spongiosa of heart valves made of?
Proteoglycans
What is the ventricularis of heart valves made of?
Elastic fibres
