Skin deep muscles - I

Our skin looks so delicate and thin but has muscles in it and muscles beneath and attached to it.

Arrector pili are the muscles in the skin. And panniculus carnosus are the muscles just beneath the skin.

The panniculus carnosus are seen in animals like cattle and cats who move portions of their skin at will. The panniculus carnosus, are in the form of a sheet and in higher mammals, like primates, they have slowly regressed. Their functional importance has reduced as our arm can reach almost any part of the body that needs to be scratched or freed from pestering parasites.

Arrector pili are the erector muscle of the hair. They are strands of smooth muscles attached to the hair follicleor shaft at one end and to the dermis at the other end just beneath the epidermis. On contraction the arrector pili pull the hair into an upright position and creates a tiny dimple into the skin beneath the hair. In the absence of hair i.e. in glabrous skin it forms the "goose bumps".

Forming the goose bumps is a reflex action (pilomotor reflex.) A reflex action is one which takes place automatically, without thinking, immediately and repeatedly in the same manner, when the same stimulus is applied.

The contraction of arrector pili muscles, pulls on the hair changing the angle they make with skin and such movement can trap variable amounts of air in the fur. This mechanism allows animals to keep themselves warm or cool as required.

Birds may erect their feathers in a similar manner. Birds as well as mammals erect their feather or hair when they are scared, angry, or cold. They look more formidable with apparent increase in size and may add some more air to insulate them further. In birds the feather muscles and the apterial muscles are bundles of smooth muscle and are limited to the dermis of the skin.

Aquatic mammals like seals do not have arrector pili muscles in the skin, and their fur lies flat.

Cranes have bare red skin patches on their heads. These patches play an important role in communication as by contracting or relaxing the subcutaneous muscles, the cranes can vary the extent of skin displayed.

Long and sensitive vibrissae (vibrators) or whiskers are seen in many animals. The whiskers decorate a cat, dog, rabbit, rat, mouse, seal and walruses' muzzles. Whiskers are nearly twice as thick as ordinary hair are. Their roots are deeper than roots of other hair. The base of a vibrissa lies in a follicle, where receptor cells detect displacement (bending) and pressure. The tremble of a vibrissa is possible because of a muscular filament in skin, which forms a loop around sack. Whiskers can be moved at will backward or forward to detect sensations like movements better.

Go To Page: 1 2