Types of Muscle Pennation and Facial Muscles Anatomy

Which muscle is the prime mover of hip flexion?

What is the function of the gluteus maximus muscle?

Which muscle acts as a synergist to bring about the cross-legged position?

Which muscle group is a prime mover of thigh extension and knee flexion?

What is the main function of the adductor muscles?

Where are vastus lateralis and rectus femoris sometimes used as sites for intramuscular injections?

During muscle contraction, what happens to the thin actin filaments?

What occurs to the I bands during muscle contraction?

What is the function of Troponin during muscle contraction?

What characterizes an isotonic muscle contraction?

Which phase of contraction involves the muscle cell shortening due to myosin pulling (power stroke)?

What happens to the H zone during muscle contraction?

What type of muscle arrangement is characterized by fascicles inserting into only one side of the tendon?

Which muscle covers the frontal bone and is responsible for raising the eyebrow and wrinkling the forehead?

Which facial muscle is known as the 'kissing muscle' and allows for closing the mouth and protruding the lips?

What function does the Buccinator muscle serve?

Which muscle acts synergistically with the Masseter in closing the jaw?

Which muscle pulls the corner of the mouth inferiorly, producing a downward sag of the mouth?

Muscle Functions and Actions

The iliopsoas muscle is the prime mover of hip flexion.
Gluteus maximus is primarily responsible for hip extension, external rotation, and maintaining pelvis stability during movements.
Sartorius acts as a synergist for achieving the cross-legged position by flexing, abducting, and laterally rotating the hip.
The hamstring group serves as a prime mover for thigh extension and knee flexion during activities such as walking and running.
Adductor muscles function to bring the thighs together (adduction) and assist in stabilizing the pelvis during movement.

Intramuscular Injection Sites

Vastus lateralis and rectus femoris are often used as sites for intramuscular injections, especially in pediatric patients due to their muscle size and accessibility.

Muscle Contraction Mechanisms

During muscle contraction, thin actin filaments slide over thick myosin filaments, leading to muscle shortening.
I bands, which contain only actin filaments, decrease in width during contraction as actin slides toward the center of the sarcomere.
Troponin regulates muscle contraction by binding calcium ions, causing tropomyosin to shift and uncover the myosin-binding sites on actin filaments.
Isotonic muscle contractions involve the muscle changing length while generating force, such as during lifting or lowering an object.
The power stroke phase of contraction is characterized by the muscle cell shortening as myosin pulls the actin filament.

Structural Changes During Contraction

The H zone, representing the region of only myosin filaments, diminishes during contraction as actin filaments slide inwards, resulting in a more overlapping arrangement.

Muscle Arrangement

Unipennate muscle arrangement is characterized by fascicles inserting into only one side of the tendon, providing efficient force generation.

Facial Muscles and Functions

Frontalis muscle covers the frontal bone and is responsible for raising the eyebrows and wrinkling the forehead.
Orbicularis oris is known as the 'kissing muscle' that enables mouth closure and lip protrusion.
Buccinator muscle aids in chewing by holding food between the teeth and flattening the cheeks.
Temporalis muscle works synergistically with the masseter in closing the jaw during biting and chewing.
Depressor anguli oris pulls the corner of the mouth inferiorly, creating a downward sag of the mouth.

Learn about the different types of muscle pennation including unipennate, bipennate, and multipennate. Explore the anatomy of head and neck muscles, as well as facial muscles such as Frontalis, Orbicularis Oculi, and Orbicularis Oris.