Chapter 4. Connective Tissues of Peripheral Nerves
Which of the following descriptions is correct about the structure of the nerve?
A. Along the nerve, the same axon can contribute to different fascicles.
B. The location of nerve fascicles inside the nerve is consistent along the nerve, with little variation.
C. The proportion of connective tissue in the nerve decreases as it travels distally.
D. In the vicinity of a joint, the nerve has fewer fascicles of larger size to offer more resistance to stretching.
A is correct. Inside each nerve, the axons form an intraneural plexus in such a fashion that one axon can contribute to different fascicles along the nerve length.
B is incorrect. The number, size, and locations of fascicles in peripheral nerves are also variable even within a single nerve and can vary as much as 23 times along a 4- to 5-cm length of nerve.
C is incorrect. The proportion of neural tissue is higher at the origin of the nerve. Distally, the proportion of connective tissue increases and can reach up to 75% of the nerve cross section.
D is incorrect. In the proximity of joints, the fascicles are thinner, more numerous, and have a thicker perineurium, which may confer better protection against pressure and stretching.
The connective tissue layers of a typical peripheral nerve are as follows from inside to outside:
A. Endoneurium - paraneurium - epineurium - perineurium
B. Perineurium - endoneurium - paraneurium - epineurium
C. Endoneurium - perineurium - epineurium - paraneurium
D. Perineurium - endoneurium - epineurium - paraneurium
C is correct. The endoneurium is a thin, delicate layer of loose connective tissue surrounding each fiber. A group of fibers forms the nerve fascicle, which is surrounded by the perineurium. The epineurium is the outer layer of connective tissue. The paraneurium is the connective tissue that binds the nerve to the surrounding tissues or more than one nerve together.
A, B, and D are incorrect. These options don’t follow the correct order for connective tissue layers from inside to outside.
Which of the following anatomical descriptions of the structure of a peripheral nerve is correct?
A. The interfascicular epineurium consists of elastic connective tissue fibers binding and maintaining the fascicles in a consistent disposition along the nerve.