The animal body is a collection of tissue elements and, in most instances, these tissues have organized themselves into a recognizable entity. These entities will perform a distint function and therefore are given the name, ‘organ’.
Among the organs present in the human body, the largest is the ‘skin’. Skin covers the entire surface of the body while there are many other organs which can hardly be seen by the naked eye. Some organs are arranged in pairs (e.g kidneys) while some are single structural units (e.g bladder). In certain instances, organs are labeled as ‘hollowed organs’ as they contain a cavity within their outer coverings.
The body contains many different organs and, in most instances, these organs are arranged into ‘organ systems’. For example, the kidneys, the ureters, the bladder, and the urethra are separate organs and together these organs form the ‘excretory system’. Similarly, organs such as the mouth, esophagus, stomach, small and large intestines together will form the ‘digestive system’. In total, there are about ten different organ systems in the human body and the characteristic feature of each of these systems is the fact that there are two or more organs working together in order to provide a common function in each of these systems.
In order to recognize the major organs in the body, one effective way is to look at the main organ systems. Following is a brief description of such systems, along with the organs giving rise to each.
As mentioned before, the digestive system is composed of the mouth, esophagus, stomach, small intestine and the large intestine. Its main function is to break down the ingested food particles and absorb the nutrients before excreting the remnants as stool.
The respiratory system is composed of the nose, larynx (or voice box), trachea, and the lungs. It performs the vital function of breathing in oxygen and allowing the exchange of oxygen and carbon dioxide from the blood vessels inside the lungs.
When the heart, blood vessels and the blood act together, it becomes the circulatory system. Its main function is to transport nutrients, gases such as oxygen and carbon dioxide, hormones, by-products and other elements throughout the body.
The main organs giving rise to the skeletal system include the bones and the cartilages. However, tendons and ligaments are also considered to be components of this system. It provides structural support to the body and protects internal organs from outside forces. At the same time, the skeletal surfaces will provide much needed attachment sites for other organs in the body.
The muscular system consists of two main muscle types; the skeletal muscles and the smooth muscles. It provides the strength and the flexibility for body movements and, at times, it provides support to internal organs to mobilize or contract depending on the functionality of these structures.
The main organs giving rise to the nervous system include the brain, spinal cord and the peripheral nerves. It provides signal transmission throughout the body and enables the feeling of pain, sense of position and other sensations. As with many other organ systems, the nervous system does not function in isolation but provides support to other organ systems to perform its function in a regulated manner.
It could be designated as a collection of organs giving rise to chemical signals through hormone secretion and it includes organs such as the pituitary, pancreas, thyroid, adrenal glands, etc.
As mentioned previously, the kidneys, ureters, bladder and the urethra forms the excretory system and it enables the body to excrete toxins, byproducts and other elements from the body.
The reproductive system contains organs which manufacture cells necessary for reproduction. The organs involved will differ in their structure and function between the two genders. Thus, the female reproductive system is composed of the ovaries, oviducts, uterus, vagina and mammary glands, while the testes, seminal vesicles and penis gives rise to the male reproductive system.
Apart from these organ systems, the lymphatic system functions by providing immune protection to the body and consists of the lymph nodes, the lymphatic vessels, and other cellular elements.