Cardiac Muscle

Fibers of cardiac muscle have features somewhat intermediate between those of skeletal and visceral muscle.

• The intercalated discs are key features of cardiac muscle.
   

Clinical note: The fact that cardiac muscle lacks satellite cells severely limits its capacity for repair after injury, such as injury from transient ischemia during myocardial infarction (heart attack). As shown on the next page, injured cardiac myofibers degenerate and are replaced by connective tissue. Cardiac muscle injury and degeneration causes release of various cytoplasmic enzymes, which can be detected in the circulating blood and used as an indicator of heart damage.

Can you give a functional explanation as to why cardiac muscle has many histological features that are intermediate between skeletal and smooth muscle?

Now on to blood cells & hematopoiesis.