Skeletal Muscle Architecture and Muscle Naming

Question 1

Fascicle Orientation: Circular

Answer 1

Circular (orbicularis oris, orbicularis oculi)

• -sphincter
• -surround external body openings
• -close when they contract

Question 2

Fascicle Orientation: Convergent

Answer 2

Convergent (latissimus dorsi, gluteus medius, pectoralis major)

• -broad origin
• -narrow insertion
• -direction of pull can be changed b/c different groups of fibers can be activated

Question 3

Fascicle Orientation: Parallel

Answer 3

Parallel (sartorius, sternocleidomastoid, brachioradialis, flexor digitorum superficiali [FDS])

• -fascicles run parallel to long axis of muscle
• -tapered at both ends
• -strap
• -high endurance, not very strong though

Question 4

Fascicle Orientation: Pennate

Answer 4

Pennate (uni: extensor digitorum longus; bi: rectus femoris; multi: deltoid)

• -fascicles short
• -attach obliquely to tendon or raphe
• -uni-, bi-, to mulitpennate
• -stronger than parallel muscle of same size

Question 5

Muscle Compartments

Answer 5

Dense, fibrous CTs divides muscles into compartments
Muscles in same compartment are often synergistic (similar actions)
Muscles in opposite compartments are usually antagonistic (opposite actions)
Usually, muscles in one compartment are innervated by a single nerve

Question 6

Compartment syndrome

Answer 6

Damaged muscle swells, surrounding fascia (inelastic) constricts

Puts pressure on vessels and nerves (pain!), also prevents blood from entering or draining

Acute compartment syndrome (accident/injury) can lead to tissue loss (muscle or limb) due to a loss of blood supply

Chronic compartment syndrome is caused by overuse…resting until it heals is the best course

Question 7

Naming Muscles: 1. Location

Answer 7

Biceps BRACHII (arm)
Quadriceps FEMORIS (femur)

Question 8

Naming Muscles: 2. Shape

Answer 8

DELTOID (triangular…think Greek letter delta)

TRAPEZIUS (trapezoidal)

Question 9

Naming Muscles: 3. Relative Size

Answer 9

Gluteus MAXIMUS (largest)
Adductor BREVIS (short)

Question 10

Naming Muscles: 4. Direction of Fascicles and Fibers

Answer 10

RECTUS (straight) abdominus

External OBLIQUE

Question 11

Naming Muscles: 5. Location of Attachments

Answer 11

CORACOBRACHIALIS (coracoid process and arm)

Question 12

Naming Muscles: 6. Number of Origins/Heads

Answer 12

BICEPS (2 heads) brachii

QUADRICEPS (4 heads) femoris

Question 13

Naming Muscles: 7. Action

Answer 13

FLEXOR digitorum longus
ADDUCTOR magnus
ABDUCTOR pollicis longus