Final answer:
Hypertrophy typically occurs in muscle tissue, specifically in skeletal muscle from resistance training, in cardiac muscle as a condition, and in smooth muscle due to hormonal signals like those in the uterus.
Step-by-step explanation:
Hypertrophy is the increase in the size of a structure and is most often associated with muscle growth.
Muscle hypertrophy tends to occur in response to resistance training, such as weight-lifting exercises, rather than endurance training.
During such resistance training, an increase in the number of sarcomeres and myofibrils in a skeletal muscle happens, leading to a greater overall mass of the muscle without a significant increase in mitochondria or capillary density.
Connective tissues also develop further to contain the muscles more robustly as they generate increasingly powerful contractions.
Similarly, cardiac hypertrophy is observed when the myocardium, the cardiac muscle that forms the wall of the heart, enlarges abnormally. This condition can compromise the heart's ability to pump blood effectively, potentially leading to heart failure.
Smooth muscle can also undergo hypertrophy and hyperplasia; the uterus is a prime example, where an increase in smooth muscle cells occurs in response to hormonal changes.
In all cases of muscle hypertrophy, it is the individual muscle fibers that increase in width, while the total number of fibers generally remains unchanged.
The development and regeneration of muscle tissue are critical for maintaining this hypertrophic state, particularly in those who engage in bodybuilding or regular resistance training, which demands high numbers of fast glycolytic (FG) fibers.