OCC313 Biomedical Science

Muscles of the Upper and Lower Limbs

Skeletal muscles consist of muscle tissue (fibers), connective tissues, nerves, and blood vessels, playing a vital role in movement.
Five primary functions of skeletal muscles include producing movement, maintaining body posture, supporting soft tissues, guarding body openings, and regulating body temperature.

Muscle Contraction Types

Isotonic Contractions: Muscles change length to move a load, categorized into:
- Concentric: Muscle shortens when tension exceeds resistance.
- Eccentric: Muscle lengthens when tension is less than resistance.
Isometric Contractions: Muscles develop tension without changing length.

Muscle Interactions and Roles

Muscles work in synergistic groups to enhance efficiency in movement.
Functional Groups:
- Prime Movers: Major force producers for specific movements.
- Antagonists: Oppose movements; regulate prime movers' actions to prevent overshooting.
- Synergists: Add force and reduce unwanted movements.
- Fixators: Stabilize bones/muscle origins.

Muscular System Divisions

Axial Muscles: Account for 60% of skeletal muscles; responsible for head, spinal column positioning, and rib cage movement.
Appendicular Muscles: 40% of skeletal muscles; support girdles and limbs.

Nerve Supply to Upper Limb Muscles

Brachial plexus is a network of nerves crucial for upper limb innervation, originating from C5-C8 and T1, with contributions from C4 and T2.
Major nerves derived include:
- Axillary
- Musculocutaneous
- Median
- Ulnar
- Radial

Muscles Crossing the Shoulder Joint

Movements at the shoulder include flexion, extension, abduction, adduction, and rotation.
Prime movers of the arm include:
- Pectoralis Major: Originates from sternum, flexes and adducts the arm.
- Latissimus Dorsi: Extends and rotates the arm.
- Deltoid: Abducts the arm.

Muscles of the Elbow Joint

Triceps Brachii: Prime mover of elbow extension; innervated by the radial nerve.
Anconeus: Stabilizes the ulna during pronation; assists triceps.

Forearm Muscles

Anterior Flexors: Flexor Carpi Radialis and Ulnaris; both facilitate wrist flexion but differ in hand motions.
Posterior Extensors: Extensor Carpi Radialis Longus and Brevis extend and abduct the wrist.

Muscles Moving the Hand

Flexor Digitorum Superficialis: Flexes at the wrist and middle phalanges; innervated by the median nerve.
Flexor Pollicis Longus: Flexes the thumb; innervated by anterior interosseous nerve.
Extensor Digitorum: Primary finger extender; innervated by radial nerve.

Intrinsic Hand Muscles

Control fine finger movements and include thenar and hypothenar eminences, as well as midpalmar muscles.

Lower Limb Musculature

Hip and Knee Movements: Anterior muscles flex the thigh and extend the leg, while posterior muscles extend the thigh and flex the knee.
Adductors: Medial group of thigh muscles that adduct and medially rotate.

Thigh Muscles Overview

Flexors: Iliopsoas (iliacus and psoas major), rectus femoris, and tensor fasciae latae.
Extensors: Hamstring group (biceps femoris, semitendinosus, semimembranosus) and gluteus maximus.
Adductors: Include adductor magnus, longus, and gracilis.

Foot Movement Muscles

Dorsiflexion and Inversion: Tibialis anterior.
Plantar Flexion: Gastrocnemius, soleus, and plantaris are responsible; collectively called the triceps surae.
Retinaculae: Structures that hold tendons in place at the ankle.

Summary

Understanding the anatomy and functions of upper and lower limb muscles is essential for recognizing how movements are generated, controlled, and facilitated throughout the body. This involves a complex interaction of muscular contractions, functional roles, and neural innervation.### Muscles of the Thigh

Adductors: Located in the medial compartment, these muscles are responsible for adducting the thigh.
Hamstrings: Found in the posterior compartment, they flex the leg and extend the thigh, innervated by the tibial nerve (part of sciatic nerve).
Vastus Muscles: Includes vastus lateralis, vastus intermedius, and vastus medialis; these are part of the quadriceps femoris group located in the anterior compartment, responsible for extending the leg.
Rectus Femoris: Also part of the quadriceps group, it aids in leg extension and plays a role in hip flexion.

Compartment Overview

Posterior Compartment: Contains muscles that primarily flex the leg and extend the thigh.
Anterior Compartment: Contains extensor muscles of the leg, innervated by the femoral nerve.
Medial Compartment: Home to adductor muscles; innervated by the obturator nerve.

Muscles of the Leg

Triceps Surae: Comprised of the gastrocnemius and soleus; located in the posterior compartment of the leg, responsible for plantar flexion of the foot and flexion of the toes, innervated by the tibial nerve.
Tibialis Anterior: Found in the anterior compartment, it dorsiflexes the foot and extends the toes, innervated by the deep fibular nerve.
Fibularis Muscles: Located in the lateral compartment of the leg, these muscles plantar flex and evert the foot, innervated by the superficial fibular nerve.

Bone References

Femur: Main thigh bone, crucial for muscle attachment in the thigh.
Tibia and Fibula: Bones of the lower leg, providing support and muscle attachment for the leg muscles.