Joints and Muscles: Key Structures and Functions (Lab Exam 2 Study Guide)

Lab 9: Articulation and Movements

Key Ligaments and Bones of Major Joints

This section covers the primary ligaments and bones involved in joint structure and movement, focusing on the knee, shoulder, and hip joints. Understanding these components is essential for recognizing how joints provide stability and allow for movement.

• Anterior cruciate ligament (ACL): A major ligament in the knee that prevents anterior displacement of the tibia relative to the femur.

• Fibular collateral ligament (LCL): Provides lateral stability to the knee joint.

• Tibial collateral ligament (MCL): Provides medial stability to the knee joint.

• Lateral and Medial meniscus: Crescent-shaped cartilage pads that cushion and stabilize the knee joint.

• Patella: The kneecap; protects the knee joint and improves leverage of the quadriceps muscle.

• Patellar ligament: Connects the patella to the tibia.

• Quadriceps tendon: Connects the quadriceps muscles to the patella.

• Femur, Tibia, Fibula: The main bones forming the knee joint.

• Coxal bone: The hip bone, forming the pelvic girdle.

• Iliofemoral, Pubofemoral, and Ischiofemoral ligaments: (Note: Ischiofemoral not listed but commonly included) These ligaments reinforce the hip joint capsule.

• Coracohumeral and Glenohumeral ligaments: Stabilize the shoulder joint.

• Scapula, Humerus: Bones forming the shoulder joint.

Example: The ACL is commonly injured in sports that involve sudden stops and changes in direction, such as soccer or basketball.

Additional info: The stability of synovial joints depends on the shape of the articular surfaces, the strength of ligaments, and the tone of surrounding muscles.

Lab 10: Muscle Structure and Function

Microscopic Anatomy of Skeletal Muscle

Skeletal muscle fibers are highly organized structures that allow for voluntary movement. Understanding their microscopic anatomy is crucial for grasping how muscles contract and generate force.

• Endomysium: A thin connective tissue layer surrounding each muscle fiber.

• Myofibrils: Cylindrical organelles within muscle fibers, composed of repeating units called sarcomeres.

• Sarcomere: The functional contractile unit of muscle, defined as the region between two Z discs.

• Sarcolemma: The plasma membrane of a muscle fiber.

• Sarcoplasmic reticulum (SR): Specialized endoplasmic reticulum that stores and releases calcium ions for muscle contraction.

• Terminal cisternae: Enlarged areas of the SR that closely associate with T tubules to form a triad.

• Transverse (T) tubules: Invaginations of the sarcolemma that transmit action potentials into the muscle fiber.

• Triad: A structure formed by a T tubule flanked by two terminal cisternae; essential for excitation-contraction coupling.

• Mitochondrion: Organelle responsible for ATP production, abundant in muscle cells due to high energy demand.

• Nucleus: Skeletal muscle fibers are multinucleated, with nuclei located at the periphery of the cell.

Example: During muscle contraction, calcium released from the SR binds to troponin, initiating the sliding filament mechanism within the sarcomere.

Additional info: The arrangement of myofibrils and sarcomeres gives skeletal muscle its striated appearance.

Lab 11: Muscular System

Major Muscles of the Human Body

This section lists and describes the primary muscles responsible for movement and posture. Knowledge of muscle names, locations, and functions is fundamental for understanding human anatomy and physiology.

• Adductor longus, Adductor magnus: Medial thigh muscles that adduct the femur.

• Biceps brachii: Flexes the elbow and supinates the forearm.

• Biceps femoris, Semimembranosus, Semitendinosus: Hamstring muscles; flex the knee and extend the hip.

• Brachialis, Brachioradialis: Flex the forearm at the elbow.

• Deltoid: Abducts the arm at the shoulder.

• Extensor carpi radialis longus, Extensor carpi ulnaris, Extensor digitorum: Extend the wrist and fingers.

• External oblique, Rectus abdominis: Compress the abdomen and flex the vertebral column.

• Flexor carpi radialis, Flexor carpi ulnaris, Flexor digitorum profundus: Flex the wrist and fingers.

• Frontalis, Temporalis, Masseter: Muscles of facial expression and mastication.

• Gastrocnemius, Soleus: Plantar flex the foot at the ankle.

• Gluteus maximus, Iliacus, Psoas major: Extend and flex the thigh at the hip.

• Infraspinatus, Subscapularis, Supraspinatus, Teres major, Teres minor: Rotator cuff muscles; stabilize and move the shoulder joint.

• Latissimus dorsi, Trapezius, Rhomboid major: Move and stabilize the scapula and shoulder.

• Orbicularis oculi, Orbicularis oris: Close the eyelids and lips, respectively.

• Pectoralis major: Flexes, adducts, and medially rotates the arm.

• Rectus femoris, Vastus intermedius, Vastus lateralis, Vastus medialis, Sartorius: Quadriceps muscles; extend the knee and flex the hip.

• Serratus anterior: Protracts the scapula.

• Sternocleidomastoid: Flexes and rotates the head.

• Tensor fasciae latae: Abducts and medially rotates the thigh.

• Tibialis anterior: Dorsiflexes the foot at the ankle.

• Triceps brachii: Extends the forearm at the elbow.

Example: The quadriceps femoris group is essential for standing up from a seated position and for walking.

Additional info: Muscles often work in antagonistic pairs; for example, the biceps brachii (flexor) and triceps brachii (extensor) control elbow movement.

Summary Table: Selected Muscles and Their Actions

Muscle	Location	Primary Action
Biceps brachii	Anterior upper arm	Flexes elbow, supinates forearm
Triceps brachii	Posterior upper arm	Extends elbow
Deltoid	Shoulder	Abducts arm
Gastrocnemius	Posterior lower leg	Plantar flexes foot
Rectus femoris	Anterior thigh	Extends knee, flexes hip
Gluteus maximus	Buttocks	Extends and laterally rotates thigh
Masseter	Jaw	Elevates mandible (closes jaw)

Additional info: For a complete understanding, students should refer to anatomical diagrams to visualize muscle locations and attachments.