Exercise 12 Review Sheet Gross Anatomy Of The Muscular System

Exercise 12 Review Sheet: Gross Anatomy of the Muscular System

This comprehensive guide serves as a detailed review sheet for Exercise 12, focusing on the gross anatomy of the muscular system. We'll cover key muscle groups, their origins and insertions, actions, and innervations, providing you with a robust understanding to ace your next exam. Remember to consult your textbook and lab manual for additional information and specific diagrams.

I. Introduction to the Muscular System

The muscular system is responsible for movement, posture, and heat production. It comprises three main muscle types: skeletal, smooth, and cardiac. This exercise primarily focuses on skeletal muscles, which are voluntary muscles responsible for body movement. Understanding their gross anatomy, including their origins, insertions, actions, and innervations, is crucial for comprehending how the body moves. We'll dissect this systematically, covering major muscle groups and their functions.

A. Key Terminologies

Before diving into specific muscles, let's review essential terminology:

• Origin: The relatively stationary attachment point of a muscle. Usually proximal to the insertion.
• Insertion: The more movable attachment point of a muscle. Usually distal to the origin.
• Action: The movement a muscle produces when it contracts. This can be flexion, extension, abduction, adduction, rotation, etc.
• Innervation: The specific nerve that supplies a muscle with motor impulses. Understanding innervation helps diagnose neurological issues.
• Agonist (Prime Mover): The muscle primarily responsible for a specific movement.
• Antagonist: The muscle that opposes the action of the agonist. It helps control the movement and prevent overextension.
• Synergist: Muscles that assist the agonist in performing a movement.

II. Major Muscle Groups and Individual Muscles

We'll now explore major muscle groups, detailing key individual muscles within each group. Remember to visualize these muscles in three dimensions, considering their relationships to bones and other muscles.

A. Muscles of the Head and Neck

This region contains muscles responsible for facial expression, mastication (chewing), and head movement.

• Facial Muscles: These muscles are incredibly diverse, responsible for a wide array of expressions. Key examples include the orbicularis oculi (closes the eye), orbicularis oris (closes the mouth), zygomaticus major (smiling muscle), and frontalis (raises eyebrows). Their innervation is primarily by the facial nerve (CN VII).

• Masseter and Temporalis: These are the primary muscles of mastication, responsible for closing the jaw. They are innervated by the mandibular branch of the trigeminal nerve (CN V3).

• Sternocleidomastoid: This powerful neck muscle flexes the neck and rotates the head. It's innervated by the spinal accessory nerve (CN XI) and cervical spinal nerves.

B. Muscles of the Shoulder and Upper Limb

This area includes muscles responsible for shoulder movement, arm flexion and extension, forearm rotation, and hand movements.

• Shoulder Muscles: The deltoid is a large, superficial muscle responsible for abduction of the arm. Other important shoulder muscles include the pectoralis major (adduction and medial rotation), latissimus dorsi (extension and adduction), trapezius (elevation and retraction of scapula), and supraspinatus, infraspinatus, teres minor, and subscapularis (rotator cuff muscles responsible for shoulder stability and rotation). Innervation varies depending on the specific muscle, involving branches of the brachial plexus.

• Arm Muscles: The biceps brachii (flexion of the elbow and supination of the forearm) and triceps brachii (extension of the elbow) are prime movers for elbow movements. They are innervated by the musculocutaneous nerve (biceps) and radial nerve (triceps).

• Forearm Muscles: The forearm contains numerous muscles responsible for wrist and finger movements. These are categorized into anterior (flexors) and posterior (extensors) compartments. Important examples include the flexor carpi ulnaris, flexor carpi radialis, extensor carpi ulnaris, and extensor carpi radialis. Their innervation comes from the median, ulnar, and radial nerves.

• Hand Muscles: The intrinsic muscles of the hand are responsible for fine motor control of the fingers.

C. Muscles of the Thorax

These muscles play crucial roles in breathing and posture.

• Diaphragm: The primary muscle of inspiration (breathing in). It's innervated by the phrenic nerve.

• Intercostal Muscles: These muscles located between the ribs assist in breathing. The external intercostals are involved in inspiration, and the internal intercostals in expiration. They're innervated by the intercostal nerves.

D. Muscles of the Abdomen

These muscles support the abdominal viscera, aid in defecation, urination, and childbirth, and contribute to posture and trunk movement.

• Rectus Abdominis: The "six-pack" muscle, responsible for flexion of the trunk.

• External and Internal Obliques: These muscles rotate and flex the trunk.

• Transversus Abdominis: The deepest abdominal muscle, providing support for abdominal viscera.

These abdominal muscles are generally innervated by the thoracic and lumbar spinal nerves.

E. Muscles of the Back

These muscles are crucial for posture, extension of the vertebral column, and lateral flexion.

• Erector Spinae Muscles: A group of muscles that extend along the entire length of the vertebral column, playing a vital role in posture and extension.

• Trapezius (partially): As mentioned previously, the trapezius also plays a role in back movement and scapular stabilization.

• Latissimus Dorsi (partially): The latissimus dorsi also contributes to back extension and arm movements.

Innervation for back muscles primarily comes from posterior rami of spinal nerves.

F. Muscles of the Pelvic Floor

These muscles support pelvic organs, aid in urination and defecation, and play a role in sexual function.

• Levator Ani: A group of muscles forming the pelvic floor.

• Coccygeus: Another muscle contributing to the pelvic floor.

Innervation is via branches of the sacral plexus.

G. Muscles of the Lower Limb

This region contains muscles crucial for locomotion, including hip flexion and extension, knee flexion and extension, ankle movement, and foot movement.

• Hip Muscles: The gluteus maximus (extension of hip), gluteus medius, and gluteus minimus (abduction and medial rotation of hip) are important muscles around the hip joint. The iliopsoas (flexion of hip) is also crucial. Innervation comes from branches of the lumbar and sacral plexuses.

• Thigh Muscles: The quadriceps femoris (extension of knee), comprised of the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius, is a powerful knee extensor. The hamstrings (flexion of knee), including the biceps femoris, semitendinosus, and semimembranosus, are antagonists to the quadriceps. The adductor muscles adduct the thigh. Innervation is mainly from the femoral and sciatic nerves.

• Leg Muscles: The gastrocnemius and soleus are the primary muscles of the calf, responsible for plantarflexion of the foot. The tibialis anterior dorsiflexes the foot. Innervation comes from the tibial and common peroneal nerves.

• Foot Muscles: The intrinsic muscles of the foot are responsible for fine motor control of the toes.

III. Clinical Correlations

Understanding the muscular system’s anatomy is crucial for diagnosing and treating various conditions. For example:

• Muscle strains and tears: Knowledge of muscle origins, insertions, and actions helps diagnose the location and severity of muscle injuries.

• Neurological disorders: Innervation patterns help pinpoint the location of nerve damage, leading to more accurate diagnoses.

• Musculoskeletal disorders: Understanding muscle imbalances can contribute to identifying and managing conditions like back pain and carpal tunnel syndrome.

IV. Practical Applications and Further Study

This review sheet provides a strong foundation for understanding the gross anatomy of the muscular system. To solidify your knowledge:

• Active Recall: Test yourself regularly using flashcards or diagrams.

• Clinical Integration: Relate the anatomical knowledge to clinical scenarios, such as muscle injuries and nerve damage.

• Three-Dimensional Visualization: Use anatomical models or online resources to visualize the muscles in three dimensions.

• Comparative Anatomy: Explore the muscular systems of other animals to broaden your understanding of musculoskeletal function.

By actively engaging with the material and employing these strategies, you will develop a deeper, more robust understanding of the muscular system, setting you up for success in your studies. Remember to consult your textbook and lab manual for additional details and diagrams. This review sheet serves as a robust starting point for your continued learning and should be supplemented with further independent study and active recall practices.