Where is the origin of the arrector pili muscle?
Conclusion: At the isthmus level, above their follicular attachments, the arrector pili muscles that originate from their respective follicles join together, forming a single muscular structure that extends upward to its superior attachment zone.
Why vestigial structures are evidence for evolution?
Structures that have lost their use through evolution are called vestigial structures. They provide evidence for evolution because they suggest that an organism changed from using the structure to not using the structure, or using it for a different purpose.
What is the purpose of the arrector pili muscle?
Arrector Pili Muscle – This is a tiny muscle that attaches to the base of a hair follicle at one end and to dermal tissue on the other end. In order to generate heat when the body is cold, the arrector pili muscles contract all at once, causing the hair to “stand up straight” on the skin.
When the arrector pili muscles contract what happens?
The arrector pili muscle is a tiny muscle connected to each hair follicle and the skin. When it contracts it causes the hair to stand erect, and a “goosebump” forms on the skin.
Are arrector pili voluntary or involuntary?
involuntary
Each arrector pili is composed of a bundle of smooth muscle fibres, which attach to several follicles (a follicular unit) and is innervated by the sympathetic branch of the autonomic nervous system. The contraction of the muscle is, therefore, involuntary .
What is the arrector pili muscle made of?
smooth muscle fibres
Anatomical terms of muscle Each arrector pili is composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit), and is innervated by the sympathetic branch of the autonomic nervous system. The contraction of the muscle is then involuntary–stresses such as cold, fear etc.
What was the Lamarck’s theory of evolution?
Lamarckism, a theory of evolution based on the principle that physical changes in organisms during their lifetime—such as greater development of an organ or a part through increased use—could be transmitted to their offspring.
What is the strongest evidence of evolution from a common ancestor?
Today, scientists can compare their DNA. Similar DNA sequences are the strongest evidence for evolution from a common ancestor.
Why is arrector pili vestigial?
Arrector Pili This process is vestigial in humans because we don’t have enough hair or fur to make it worthwhile. Fluffing up hair or fur creates pockets to trap air and warm the body. It also can make the animal look bigger as protection against threatening creatures.
What occurs when the Arrector pili muscles contract quizlet?
What occurs when the arrector pili muscles contract? Your hair stands!! Also known as Goosebumps that appear on skin.
Which fibers stimulate the arrector pili muscles?
Which fibers stimulate the arrector pili muscles? Follicles.
Which nerve fibers control the arrector pili muscles?
Each arrector pili is composed of a bundle of smooth muscle fibres which attach to several follicles (a follicular unit). Each is innervated by the sympathetic division of the autonomic nervous system.