Introduction to anatomy and physiology

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Understanding the anatomy and physiology of birds and the different body systems found in the bird is useful for people seeking an understanding of how poultry work or function. Knowledge of anatomy (body parts) and physiology (body function) of the bird helps the poultry industry maximise bird performance and maintain good welfare practices. Like humans, birds eat, grow, breathe, reproduce, empty out wastes and move about. Both need food, water and air, and must protect themselves from changes in the environment.

Anatomical and physiological systems

Birds, like other animals, consist of a number of body systems, each operating independently or with each other to provide for the normal activity and functioning of the animal as a whole. Each of these body systems consists of organs – special structures adapted to carry out specific activities or functions. Each organ, in turn, consists of tissues consisting of the various types of cells that ultimately provide the means for the organs and systems to carry out their activities and functions. The study of anatomy is the study of the structure of the different cells, tissues, organs and systems. Knowledge of these structures helps to understand how they function or operate under normal circumstances. The study of how they work and function is known as physiology.

Cells

The basic unit of all systems, organs and tissues is the cell. The cell consists of a number of parts or organelles including the cytoplasm, mitochondria, ribosomes, golgi body, and the nucleus. Not all cells contain all of the various parts, for example, red blood cells lack most of the internal organelles. The contents of a cell are enclosed in a cell membrane or wall that permits the various nutrients and compounds required for its normal functioning to move into and out of it. The nucleus contains structures called chromosomes, that carry the genes, and animals generally have a pair of each chromosome.

The metabolic processes that are the basis of life are carried out in the cell by many different enzymes. Cells reproduce by mitosis or simple division where one cell divides to become two – this is normal growth. The sex cells are the exception to this – these are formed in the gonads (ovary or testes) by meiosis or reduction division and carry one instead of two of each chromosome. When two sex cells join at mating, one from the male and one from the female, the resulting cell will carry the normal cell chromosome number. The resulting cell therefore carries half of the genes of each parent. In animals like birds, this cell further divides by mitosis to become the embryo.

Not all cells are exactly alike, but depend on the function of the tissue, organ or system to which they belong. Some are glandular, others are protective, others provide support, others provide a means of communication, others provide movement, and others have a connecting function holding tissues, organs and systems together or in place. Animals consist of systems, organs, tissues and cells that serve certain functions.

Cells have a number of special features that differentiate them from non-living things:

1. They provide cooperative support of own structures, that is, the cells, tissues, organs and systems support each other.
2. They carry out the metabolic processes, that is, the chemical changes, both anabolic (constructive) and catabolic (destructive) that occur in living organisms to provide for the normal functioning of the organism or animal.
3. They respond to irritation. Irritation is defined as that ability inherent in living organisms to receive external impressions or stimuli and react to them.
4. They can reproduce their own kind as a normal function.
5. They provide their own protection or defence to the many potentially harmful situations in their environment.
6. They provide for the coordinated growth and development of their own body.