muscle fascicles and muscle structure
skeletal muscles consist of fascicles, i.e. bundles of muscle fibers surrounded by connective
tissue layer. the arrangement of fascicles varies, producing a variety of muscle structures.
convergent
muscle fascicles that
converge to a single
insertion tendon.
example: pectoralis major
(pectoral muscle)
fusiform
a modification of parallel which
results in a muscle with an
expanded midsection.
example: biceps brachii
parallel
muscle fascicles run parallel
to the long axis of the muscle.
example: sartorius of thigh.
circular
muscle fascicles arranged
in concentric rings.
examples: muscles around
the mouth and eyes.
pennate (feather) musc
muscle fascicles are attac
obliquely to a central tendor
may be multipennate,
bipennate, or unipennate.
multipennate
muscle fascicles insert into
the tendon from several side
example: deltoid
bipennate
muscle fascicles insert into
opposite sides of the tendon
example: rectus femoris
(one of four muscles of the
quadriceps).
unipennate
muscle fascicles insert into only
one side of the tendon.
example: extensor digitorum
longus of the lower leg
1. on the previous page, use the word list to label the muscle groups on the figure:
2. which major muscles / group(s) would be used to carry out the following movements:
(a) raise the lower leg (i.e. tibia and fibula) towards the buttocks:
(b) bring the upper leg forward (i.e. the femur) as in taking a step:
(c) rotate the wrist:
(d) raise the arm from the side of the body up over the head:
3. what is the unusual feature of facial muscles?

4. describe the difference between parallel and fusiform muscle structure:

©2023 biozon
isbn: 978-1-99

Question

muscle fascicles and muscle structure
skeletal muscles consist of fascicles, i.e. bundles of muscle fibers surrounded by connective
tissue layer. the arrangement of fascicles varies, producing a variety of muscle structures.
convergent
muscle fascicles that
converge to a single
insertion tendon.
example: pectoralis major
(pectoral muscle)
fusiform
a modification of parallel which
results in a muscle with an
expanded midsection.
example: biceps brachii
parallel
muscle fascicles run parallel
to the long axis of the muscle.
example: sartorius of thigh.
circular
muscle fascicles arranged
in concentric rings.
examples: muscles around
the mouth and eyes.
pennate (feather) musc
muscle fascicles are attac
obliquely to a central tendor
may be multipennate,
bipennate, or unipennate.
multipennate
muscle fascicles insert into
the tendon from several side
example: deltoid
bipennate
muscle fascicles insert into
opposite sides of the tendon
example: rectus femoris
(one of four muscles of the
quadriceps).
unipennate
muscle fascicles insert into only
one side of the tendon.
example: extensor digitorum
longus of the lower leg
1. on the previous page, use the word list to label the muscle groups on the figure:
2. which major muscles / group(s) would be used to carry out the following movements:
(a) raise the lower leg (i.e. tibia and fibula) towards the buttocks:
(b) bring the upper leg forward (i.e. the femur) as in taking a step:
(c) rotate the wrist:
(d) raise the arm from the side of the body up over the head:
3. what is the unusual feature of facial muscles?

4. describe the difference between parallel and fusiform muscle structure:

©2023 biozon
isbn: 978-1-99

Accepted Answer

### Question 2 (a)
# Brief Explanations:
To raise the lower leg (tibia and fibula) towards the buttocks, the hamstring muscles (biceps femoris, semitendinosus, semimembranosus) or more specifically, the **gastrocnemius** (calf muscle) and **soleus** work in conjunction with the hamstrings? Wait, no—actually, the movement of flexing the knee (bringing lower leg to buttocks) is primarily done by the **hamstring group** (biceps femoris, semitendinosus, semimembranosus) and also the **gastrocnemius** (but gastrocnemius is more for plantar flexion). Wait, correct muscle: the **hamstrings** (biceps femoris, semitendinosus, semimembranosus) are the primary knee flexors, which perform this movement. Alternatively, the **gastrocnemius** (part of calf) also assists, but the main muscle group for knee flexion (lower leg to buttocks) is the hamstrings. Wait, let's recall: knee flexion (angle between thigh and lower leg decreases) is done by hamstrings (posterior thigh muscles) and also the gastrocnemius (since it crosses the knee joint). But the most direct answer here is likely the **hamstring muscles** or specifically, the **biceps femoris, semitendinosus, semimembranosus**—but maybe the answer expected is "hamstrings" or "gastrocnemius and hamstrings"? Wait, no, the primary knee flexors are the hamstrings. Wait, another thought: the movement of bringing lower leg to buttocks is knee flexion, so the muscles involved are the hamstring group (biceps femoris, semitendinosus, semimembranosus) and the gastrocnemius (calf muscle) also contributes. But maybe the answer here is the **hamstrings** or the **biceps femoris, semitendinosus, semimembranosus**. Alternatively, the **gastrocnemius** (but that's more for ankle movement, but it does cross the knee). Wait, perhaps the answer is the **hamstring muscles** (biceps femoris, semitendinosus, semimembranosus) or the **popliteus**? No, popliteus is for unlocking the knee. So the main muscles for knee flexion (lower leg to buttocks) are the hamstrings. So the answer should be the hamstring group (biceps femoris, semitendinosus, semimembranosus) or simply "hamstrings".

# Answer:
Hamstring muscles (biceps femoris, semitendinosus, semimembranosus) (or gastrocnemius also assists, but primary is hamstrings)

### Question 2 (b)
# Brief Explanations:
Bringing the upper leg forward (femur) as in taking a step is hip flexion. The primary muscles for hip flexion are the **iliopsoas** (iliacus and psoas major), the **rectus femoris** (part of quadriceps), the **sartorius**, and the **tensor fasciae latae**. So the main muscle group here is the iliopsoas, rectus femoris, sartorius, or tensor fasciae latae. The most common answer for hip flexion (stepping forward) is the **iliopsoas** (iliacus + psoas major) and the **rectus femoris** (quadriceps). Alternatively, the sartorius (the longest muscle in the body) also assists in hip flexion. So the answer would be the iliopsoas, rectus femoris, sartorius, or tensor fasciae latae. The primary one is iliopsoas.

# Answer:
Iliopsoas (iliacus + psoas major), rectus femoris (quadriceps), sartorius, or tensor fasciae latae (primary is iliopsoas)

### Question 2 (c)
# Brief Explanations:
Rotating the wrist involves the **supinator** (for supination, turning palm up) and the **pronator teres** and **pronator quadratus** (for pronation, turning palm down). Additionally, the **extensor carpi radialis longus/brevis** and **flexor carpi radialis** also assist in wrist rotation. But the main muscles for wrist rotation (supination/pronation) are the supinator (supination) and pronator teres/quadratus (pronation). So the answer would be the supinator, pronator teres, and pronator quadratus.

# Answer:
Supinator (for supination), Pronator teres and Pronator quadratus (for pronation) (or collectively, the supinator and pronator muscles)

### Question 2 (d)
# Brief Explanations:
Raising the arm from the side up over the head is shoulder abduction (moving arm away from body) and then shoulder flexion (moving arm overhead). The primary muscles for shoulder abduction (first part, raising from side) are the **deltoid** (middle deltoid) and the **supraspinatus** (initiates abduction). For shoulder flexion (moving overhead), the **anterior deltoid**, **coracobrachialis**, and **pectoralis major** (clavicular head) also assist. So the main muscles here are the **deltoid** (middle and anterior parts) and the **supraspinatus**. So the answer would be deltoid (middle deltoid for abduction, anterior deltoid for flexion) and supraspinatus.

# Answer:
Deltoid (middle deltoid for abduction, anterior deltoid for flexion), Supraspinatus (initiates abduction)

### Question 3
# Brief Explanations:
Facial muscles have an unusual feature: they are **inserted into the skin** rather than into bones (like most skeletal muscles, which have origins and insertions on bones). So when facial muscles contract, they move the skin (creating facial expressions) rather than moving bones relative to each other. For example, the orbicularis oris (around mouth) and orbicularis oculi (around eyes) insert into the skin of the face, allowing for expressions like smiling, frowning, etc.

# Answer:
Facial muscles insert into the skin (rather than bones) so their contraction moves the skin (creating facial expressions)

### Question 4
# Brief Explanations:
- **Parallel muscle structure**: Muscle fascicles run parallel to the long axis of the muscle. These muscles have a uniform width along their length (e.g., sartorius of the thigh).
- **Fusiform muscle structure**: A modification of parallel structure where the muscle has an expanded (bulging) midsection (belly) and tapered ends. The fascicles still run parallel, but the muscle’s shape is spindle - like (e.g., biceps brachii).

So the difference is in their shape: parallel muscles have a uniform width, while fusiform muscles have a wider (expanded) middle and narrower ends, even though their fascicles are parallel in both cases.

# Answer:
Parallel: Fascicles parallel to muscle long axis, uniform width (e.g., sartorius). Fusiform: Parallel fascicles, expanded midsection (spindle - shaped, e.g., biceps brachii).

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QUESTION IMAGE

Question

Explanation:

Question 2 (a)

Answer:

Question 2 (b)