Hypertrophy

Hypertrophy is a growth adaptation in response to physiologic stress placed on it.

Hypertrophy is an increase in cell growth. An increase in cell growth through increasing the size of the cells. Increase in size of the cells is done by stretching of the cells. This stretching of the cells is seen only in the permanent tissues of the body like Heart myocytes, Skeletal tissues and Nerves.

These permanent tissues can only undergoes Hypertrophy because stem cell is absent in these cells. The Stem cells are necessary to produce new cells as a cell growth. 

Why does Permanent tissues need Hypertrophy ?

The Organs of the body are in continuous stress from the Outside Environment. There is a Physiologic Stress that are continuously working on the Organs.

In order to deal with the changing stress the permanent tissues also changes. Therefore, an increase in stress leads to an increase in workload to the Permanent tissues that forces the cells of the Permanent tissues to undergo Hypertrophy in order to maintain Homeostasis. 

How does Permanent Tissues undergoes Hypertrophy ?

Hypertrophy is to be done through a series of steps :-

First in order for the cell to undergoes hypertrophy, it needs an increase in Protein Synthesis. An increase in Protein Synthesis ensures an increase in Cytoskeloton that gives the cell it’s shape and size. The Cytoskeleton is predominantly made up of Proteins. 

In order to produce excess Protein in body, it needs a gene activation which signals the cells of the Permanent tissues to increase the Protein synthesis. 

When the cells get bigger it requires cellular machinery to handle it. Hence cells started to make organelles in order to support the cellular function of Hypertrophic cell.  

Examples of Hypertrophy :-

Left Ventricular Hypertrophy is seen as a result of increase in Afterload or  Pre-load. Increase in Afterload is seen as a result of resistance against the outflow that is an increase resistance at the aorta creates an increased Afterload which increases the workload at the left ventricle as a result Left ventricles Hypertrophies. Increase in pre-load also increases the workload at the ventricles which later turns into a Hypertrophic ventricles.

Skeletal Muscle Hypertrophies as a result of Muscle Training. An increase in stress at muscle due to rigorous muscle training changes the gene expression leading to the duplication of sarcomere that causes the muscles to be thicker and longer. 

Surgical removal of one Kidney can also creates a compensatory hypertrophy of the remaining Kidney. As surgical removal of one Kidney produces a work overload on remaining kidney as a result the remaining Kidney Hypertrophies post nephrectomy.

Hypertrophy is also seen in a cellular level during Cytomegalovirus (CMV) infection. As cell enlargement is seen due to Iron uptake into the Cytosol of the Cytomegalovirus infected cells. 

The transverse section of the heart and sign & symptoms indicates that there is a cardiomegaly with severe left ventricular hypertrophy that reflects stiff and non-compliant ventricles. 

The left ventricular hypertrophy is seen due to chronic pressure overload caused by hypertension. 

In response to increased pressure, the left ventricle compensates through hypertrophy of the myocardial fibers and thickening of the ventricular wall.