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Topic 5_Anatomy of the Muscular System

Muscle System Overview

  • Chapter 9: p. 281-282

  • Chapter 10: p. 323-384 (Sections 10.1 – 10.5, omit p. 325-327)

  • Content focus: only the muscles included in the PowerPoint presentation.

Usage Rights

  • Educational Only: This PowerPoint presentation is for educational purposes only.

  • Do not post or distribute without permission from the author.

  • Affiliation: Université d’Ottawa | University of Ottawa

Skeletal Muscles Overview

Learning Objectives

  • Describe the functions of skeletal muscles.

  • Describe characteristics of muscle tissue.

  • Understand the gross structure of skeletal muscles, including membranes and tendons/aponeuroses.

Functions of Skeletal Muscles

  • Produce movement

  • Maintain posture and body position

  • Stabilize joints

  • generate heat- shivering

Additionally:

  • protects organs forms valves controls pupil size

  • support soft tissue

  • guard entracnes and exit

  • store nutritional reserves.

Characteristics of muscle tissue

  • excitability (responsiveness)

  • Contractility (the ability to shorten and generate force) is another key characteristic, allowing muscles to perform work and produce movement.

  • Extensibility: ability to be stretched

  • Elasticity: ability to recoil or resume resting length after being stretched

Fascicle Arrangements

  • Identify different types of fascicle arrangements in skeletal muscles.

  • Define:

    • Agonist: muscle that provides major force for a movement.

    • Antagonist: opposes/reverses a particular movement.

    • Synergist: helps the prime mover and reduces undesirable movement.

    • Fixator: a type of synergist that immoblizes bone.

    • Origin: attachment of muscle that remains fixed.

    • Insertion: attachment that moves during contraction.

Muscle Nomenclature

  • Explain the general nomenclature of skeletal muscles.

  • Discuss origin, insertion, and action of:

    • Muscles of facial expression.

    • Muscles that move the eyeballs, mandible, and tongue.

    • Muscles of the neck.

    • Muscles moving the vertebral column.

    • Respiratory muscles.

    • Muscles of the pelvic floor and perineum.

    • Muscles that move the pectoral girdle.

    • Muscles of the arm, forearm, thigh, leg, hand, and foot.

Connective Tissue Sheaths

Types of Connective Tissue Wrappings

  • Endomysium: fine areolar CT surrounding each muscle fiber.

  • Perimysium: dense irregular CT around fascicles (groups of muscle fibers).

  • Epimysium: dense, irregular CT surrounding the entire muscle.

  • Deep Fascia: coarser layer binding muscles into functional groups.

Muscle Attachments

  • Direct Attachment: epimysium fused to the periosteum of bone or perichondrium of cartilage.

  • Indirect Attachment: most muscles attach via tendons or aponeuroses, spanning joints and attaching to bones at two points.

Muscle Actions and Interactions

  • muscles can only pull;never push

  • muscles can work together or in opposition

  • 3 functional groups: prime movers, antagonists, synergists

    • muscles can change their role depending on the movement

Functional Groups

  • Prime Mover (Agonist): major force for a specific movement.

    • e.g. brachialis in elbow flexion

  • Antagonist: opposes the action of prime movers.

    • e.g. triceps in elbow flexion

  • Synergist: assists the prime mover to create the same movement.

    • add force

    • reduce unecessary movements

    • holding a bone steady: fixators

  • All muscles can change roles depending on the activity (ex: triceps brachii).

Fascicle Arrangement

Types of Fascicle Arrangements

  • Circular: concentric rings around openings (e.g., orbicularis oculi).

  • Parallel: fascicles parallel to long axis (e.g., sartorius, biceps brachii).

  • Pennate: short fascicles attaching obliquely to a central tendon (unipennate, bipennate, multipennate).

  • Convergent: fascicles converge towards a single tendon (e.g., pectoralis major).

Naming Skeletal Muscles

Criteria for Naming

  • Location: associated with a bone or body region (e.g., intercostals).

  • Shape: named based on shape (e.g., deltoid = triangle).

  • Size: descriptors (e.g., maximus for largest).

  • Direction: fiber orientation (e.g., rectus = straight).

  • Number of Origins: e.g., biceps (two heads).

  • Attachments: named for points of origin and insertion.

extensor carpi radialis longus

  • muscle that extends the wrist and is located along the radial side of the forearm.

  • when it gets this specific, usually means there is a carpi ulnaris, otherwise it would just be extensor carpi longus.

Muscles of Facial Expression

Key Muscles

  • Epicranius (Frontal and Occipital Bellies): raises eyebrows and fixes the aponeurosis.

  • Platysma: tenses neck, depresses the mandible.

  • Orbicularis Oculi: protects eyes, enables blinking.

  • Zygomaticus: raises corners of the mouth.

  • Buccinator: involved in whistling and chewing.

Muscles of Mastication

Key Muscles

  • Masseter: primary jaw closure muscle.

  • Temporalis: elevates and retracts mandible.

    • Innervated by mandibular division of cranial nerve V.

Eye Movement Muscles

Key Muscles and Functions

  • Lateral Rectus: moves the eye laterally (innervated by CN VI).

  • Medial Rectus: moves the eye medially (innervated by CN III).

  • Superior Rectus: elevates the eye (innervated by CN III).

  • Inferior Rectus: depresses the eye (innervated by CN III).

  • Superior Oblique: depresses and turns the eye laterally (innervated by CN IV).

  • Inferior Oblique: elevates and turns the eye laterally (innervated by CN III).

Muscles of the Neck

Key Muscles

  • Sternocleidomastoid: prime mover for head flexion.

  • Scalenes: elevates first two ribs and aids in neck rotation.

Back and Vertebral Muscles

Key Muscles

  • Erector Spinae: prime mover of back extension.

  • Quadratus Lumborum: helps lateral flexion of the vertebral column.

Respiratory Muscles

Key Muscles

  • External Intercostals: elevate the rib cage during inspiration.

  • Internal Intercostals: depress the rib cage during expiration.

  • Diaphragm: prime mover of inspiration, flattening during inhalation.

Abdominal Wall Muscles

Key Muscles

  • Rectus Abdominis: flexes and stabilizes the pelvis.

  • External Obliques: aid in trunk rotation.

  • Transversus Abdominis: compresses abdominal contents.

Muscles of the Pelvic Floor

Key Functions

  • Levator Ani and Coccygeus: support pelvic organs, resist intra-abdominal pressure.

Muscles of the Upper Limb

Shoulder Joint Muscles

  • Pectoralis Major: prime mover of arm flexion, adduction, and medial rotation.

  • Latissimus Dorsi: prime mover of arm extension and adducts the arm.

  • Deltoid: prime mover of arm abduction.

Elbow Joint Muscles

  • Biceps Brachii: flexes elbow and supinates forearm.

  • Triceps Brachii: powerful forearm extensor.

Muscles of the Lower Limb

Key Groups

  • Iliopsoas: major hip flexor.

  • Quadriceps Femoris: prime mover of knee extension.

  • Hamstrings: prime movers of thigh extension and knee flexion.

Leg and Ankle Muscles

  • Gastrocnemius: plantar flexes the foot.

  • Soleus: assists in plantar flexion.

  • Tibialis Anterior: prime mover of dorsiflexion.

Intrinsic Muscles of the Hand and Foot

  • Control precise movements of fingers and toes; not required to memorize specific muscles.