Question

One of the main concepts you will see repeated in this course is: form allows for function (the principle of complementarity of structure and function). Using your textbook or another reliable source, describe the characteristics of a cardiac muscle cell found in the heart and a simple columnar cell found within the small intestine. Contrast these two types of cells in terms of their structure and the organelles found within them. Finally, explain how the structure of each type of cell allows it to perform its function(s).

PLEASE CITE RELIABLE SOURCES

Answer 1

Feature	Cardiac muscle cell	Simple columnar cell
Location	Only found in heart	Found in various parts like digestive tract, female reproductive system etc.
Shape	Branching chain of cells	Tall pillar like cells
Layering	Multiple layers of cells seen (synctium appearance).	Cells are usually seen as a single layer
Cilia	Absent	Present at some places
Association with goblet cells	Absent	Present at small intestine.
Organelles: 1.Nucleus 2.Endoplasmic reticulum (sarcoplasmic reticulum in case of cardiac muscle) 3.Mitochondria	1.Mononucleated, nucleus placed at centre of cell 2.Less abundant with one terminal cistern per sarcomere 3. More in number	1.Mononucleated, nucleus placed at the bottom of cell 2. Endoplasmic reticulum similar to that of normal cell. 3.Similar to that of normal cell( lesser when compared to cardiac cell).
Junction	Gap junctions are seen between adjacent cells which are connected by intercalated discs.	Usually tight junctions are seen between adjacent cells.
Function	Transmission of impulses and contraction of heart	Absorption and secretion of mucus, enzymes etc. Sometimes microvilli may be present.

Keeping in mind the above points, let us discuss how the structure of these cells helps to perform their functions:

*Columnar cells are seen as a single layer. This helps them to act as lining tissue and has protective effects.

*The number of mitochondria are higher in cardiac muscle which is helpful for their non-fatigue nature. Cardiac cells never undergo fatigue and are in constant need of energy which in turn explains their larger mitochondria levels.

* Microvilli are found on the surface of columnar cells but not of cardiac cells. Microvilli helps to increase the surface area, which inturn helps to enhance absorption which is the main function of Columnar cells( cardiac cells do not have absorptive function).

* Goblet cells are found in association with columnar cells and not cardiac cells. Columnar cells have secretory function, for the smooth passage of gut contents and hence these goblet cells help in secreting mucus.

*Cardiac cell as such cannot have contractive function.These cells form sarcomere which is the unit of muscle contraction.So for the passage of impulses across the cells, they have gap junctions bounded by intercalated discs while the Columnar cells have tight junctions.

You can use Guyton and Hall physiology for reference purposes.