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In human anatomy, a fascicle is defined as a cluster or a bundle. This term is most commonly used when describing bundles of muscle or nerve fibers. These structures are found throughout the body and have different functions, depending on location.
A muscle fascicle is made up of skeletal muscle fibers. Skeletal muscles are one of the major muscle types found in the human body and are attached to the bones by tendons, structures formed by groups of collagen fibers. The muscle fascicle is surrounded by a specific kind of connective tissue known as perimysium.
A nerve fascicle is comprised of a bundle of nerve fibers known as axons. Axons are responsible for carrying nerve impulses away from cells. The nerve fascicle is surrounded by the perineurium, a transparent membrane made of connective tissue. The perineurium works as a protective covering for the fibers contained in the nerve fascicle.
The nerve fascicle has many different types and variations, depending on the role of the nerve fibers contained in each bundle. For instance, the superior longitudinal fasciculus connects to various lobes of the brain. What that means is that this structure plays a role in such functions as motor skills and visual perception. Memory and language skills are also affected by the superior longitudinal fasciculus.
The arcuate fasciculus is a curved bundle of nerves that is connected to the frontal cortex portion of the brain. Damage to these nerves can lead to a form of aphasia where the patient has trouble repeating what has been heard. While this was once considered a fascicle on its on, the arcuate fasciculus is now categorized as being a part of the superior longitudinal fasciculus.
The fasciculus gracilis is located in the spinal cord. The nerves found here transmit information to the brain concerning vibrations and fine touch. The sense of body positioning involving the lower part of the body is also controlled my these nerve bundles.
The cuneate fasciculus is found in the spinal cord and is responsible for transmitting information through nerve impulses to the arms. This information includes perceptions such as fine touch, vibration, and light pressure. The body's knowledge concerning the location of the arms is also attributed to the cuneate fasciculus.
The dorsal longitudinal fasciculus resides in the brain stem. It is a tract consisting of white matter fibers. White matter is responsible for carrying messages through the grey matter portions of the brain. This set of nerve bundles is responsible for carrying various types of sensory information throughout the brain.