muscle fiber arrangements

Question 1

Longitudinal arrangement

Answer 1

-parallel arrangement (tendons at end)
-long, strap like muscle with fibers parallel to its long axis
-increased ROM but less power
Examples: Sartorius (longest in body) and Sternocleidomastoid

Question 2

quadrilateral arrangement

Answer 2

parallel arrangement
-four sided and flat
-consists of parallel fibers that allow increased power but smaller ROM
Examples: rhomboids and Masseter

Question 3

Fusiform Arrangement

Answer 3

-parallel arrangement
-rounded muscle that tapers at the end
-allows for power and ROM
examples: biceps and brachioradialis

Question 4

Triangular/Fan shaped arrangement

Answer 4

-Parallel
-origin of muscle is broad, converges towards the tendon of insertion
-occurs if a large powerful muscle has to be focused at a restricted point of leverage
Example: pectoralis major

Question 5

pennate arrangements

Answer 5

“feathery” in appearance
seem to offer strength without bulk
muscles are usually quite flat or are found operating within confined spaces
-tendon goes up into them

Question 6

Unipennate

Answer 6

a series of short, parallel feather like fibers extends diagonally for a side of a long tendon
-half a feather
examples: tibialis posterior and flexor pollicis longus

Question 7

Bipennate

Answer 7

has a long central tendon with fibers extending diagonally in pairs from either side
example: rectus femoris

Question 8

Multipennate

Answer 8

several tendons are present, with fibers running diagonally between them
example: middle deltoid