I myself to this day after 54 years of keeping pigeons am still learning. I like most of us I never wanted to study physiology. That was until I realized I would need to learn all I could about my pigeons if I wanted to be a successful pigeon flier.
I will always be grateful to Dr. Leon F. Whitney it was from his book "keep Your Pigeons Flying" I found so much knowledge I was often able to win out of turn.
Back to school
Cell: By definition is A tiny mass of protoplasm that contains nucleus, is enclosed by a membrane, and forms the fundamental unit of living matter.
Physiology: by definition is 1: a science dealing with the functions and functioning of living matter and beings.
2: Functional processes in an organism or any of its parts.
Anatomy : by definition is 1: a branch of science dealing with the structure of organisms.
2: Structural makeup of organism or any of it parts.
3: a separating into parts for detailed study.
Our pigeons life starts when one male cell ( Sperm) combines with one female cell (ovum) once united the cell begin to divide 2 into 4, 4 into 8 and at the same time changing. Some become the eye's others become skin, bone and so on. Some of the cells will replace them selves while others will not.
Note: I think we pretty much get the picture. Pigeons like people are just a mass of cells each with it own function living together each doing its job to make life possible. It also import that we understand. We as pigeon keepers provide an environment that will not hinder the cells from doing there work. Overfeeding, underfeeding, overcrowding, and unsanitary conditions all can lead to problems. It is also important for you as there keeper not to just treat the pigeons with any medication unless your sure it will do more good then harm. If your unsure find a DVM you and your pigeons will be a lot better off.