Interesting (Anatomy) Tid-bits.

- Humans are excellent at detecting surface pain, but not internal pain. When an organ is in pain, the body refers the pain to another area of the body (this is called referred pain). Examples include appendix pain radiating to the abdominal wall, kidney, bladder, or gallbladder pain radiating to the testes, and heart pain radiating to the left arm. The brain can't differentiate whether the pain is coming from the organ or from the skin as both the associated skin patch and organ (e.g. the left arm and the heart) have pain receptors that cross over in the spinal column at the same spot, making it hard to differentiate the two. Thus even though the heart is in pain, the brain can think that the arm that is in pain instead.

- The number of pain receptors varies all over the body. The face, for instance, has many, many more receptors than on our back. Think about it: if your back feels itchy, you scratch your back randomly and roughly until you feel like the itch is gone, but if you felt an itch on your face, you would never scratch rough and randomly because you'd probably due some damage to its delicate skin. You'd scratch only a specific spot because if you scratched anymore, you'd activate more pain receptors and you'd end up hurting yourself rather than getting rid of the itch.

- Phantom limb pain (which I talked about briefly last year) can be experienced by amputees. Although it may sound crazy, it is true that they may describe pain coming from their missing limb. How is this possible? After the limb was removed, the main nerve of the limb will continue to grow, as if it were attempting to repopulate the limb with branches of the main nerve. As the nerve grows, all of the newly formed branches pile up in the scar tissue where the limb was removed. Every once and awhile the newly formed nerves (that correspond to the missing limb) can be stimulated, hence the phantom limb pain.

- The anterior abdominal wall (aka the skin layer on top of the stomach) is 13 layers deep! (This is not the entire abdomen but just the outermost wall, and it does not include any organs ...this is why I included the exclamation mark at the end of the previous sentence, but 13 layers is crazy).

- The posterior abdominal wall is also known as the psoas major (as this is the name of the main muscle that makes up the wall). Psoas means loin in Greek. The psoas major of most animals is referred to as the tenderloin by butchers.