Anatomy & Physiology Lab Exam 2 Study Guide: Skeletal System, Joints, and Muscles

The Skeletal System

Overview of the Skeletal System

The human skeletal system provides the structural framework for the body, protects vital organs, enables movement, and serves as a reservoir for minerals. It is divided into two main parts: the axial skeleton and the appendicular skeleton.

• Axial Skeleton: Composed of 80 bones, including the skull, vertebral column, and thoracic cage.

• Appendicular Skeleton: Composed of 126 bones, including the pectoral and pelvic girdles, and the bones of the limbs.

Axial Skeleton: Major Bones and Features

• Skull: Protects the brain and forms the structure of the face. Includes cranial and facial bones.

• Vertebral Column: Supports the body and protects the spinal cord. Divided into cervical (7), thoracic (12), lumbar (5), sacral (5 fused), and coccygeal (2-4) vertebrae.

• Thoracic Cage: Consists of the sternum and 12 pairs of ribs (true, false, and floating), protecting the heart and lungs.

Appendicular Skeleton: Major Bones and Features

• Pectoral Girdle: Clavicle and scapula, connecting the upper limb to the trunk.

• Upper Limb: Humerus, radius, ulna, carpals, metacarpals, and phalanges.

• Pelvic Girdle: Coxal bones (ilium, ischium, pubis) forming the pelvis.

• Lower Limb: Femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.

Bone Markings and Long Bone Structure

• Epiphyses: The proximal and distal ends of a long bone.

• Diaphysis: The shaft or central part of a long bone.

• Medullary Cavity: The hollow region within the diaphysis containing bone marrow.

• Compact Bone: Dense outer layer providing strength.

• Spongy Bone: Porous inner bone containing red marrow.

• Articular Cartilage: Hyaline cartilage covering joint surfaces for smooth movement.

• Epiphyseal Line: Remnant of the growth plate in adult bones.

Types of Bone Tissue

• Osseous Tissue: The main tissue of bone, providing rigidity and support.

• Hyaline Cartilage: Found on articular surfaces, in the nose, trachea, and at epiphyseal plates.

• Fibrocartilage: Found in intervertebral discs and pubic symphysis, providing strength and flexibility.

Joints (Articulations)

Classification of Joints

Joints are classified structurally by the material binding the bones and functionally by the degree of movement allowed.

Structural Classification	Types	Examples	Functional Classification
Fibrous	Sutures, Syndesmosis, Gomphosis	Skull sutures, distal tibiofibular joint, tooth/socket	Synarthrosis (immovable)
Cartilaginous	Symphysis, Synchondrosis	Pubic symphysis, intervertebral discs, epiphyseal plates	Amphiarthrosis (slightly movable), Synarthrosis
Synovial	Planar, Hinge, Pivot, Condyloid, Saddle, Ball & Socket	Shoulder, hip, elbow, knee, intercarpal joints	Diarthrosis (freely movable)

Synovial Joint Structures

• Articular Cartilage: Covers bone surfaces at joints.

• Joint Cavity: Space containing synovial fluid.

• Synovial Membrane: Produces synovial fluid for lubrication.

• Fibrous Capsule: Encloses the joint cavity.

• Ligaments: Connect bone to bone, stabilizing joints.

• Bursa: Fluid-filled sacs reducing friction.

• Periosteum: Connective tissue covering bone surfaces.

Movements at Synovial Joints

• Flexion / Extension: Decreasing/increasing the angle between bones.

• Abduction / Adduction: Movement away from/toward the midline.

• Rotation: Bone turns around its own long axis.

• Circumduction: Circular movement combining flexion, extension, abduction, and adduction.

• Pronation / Supination: Rotational movement of the forearm.

• Dorsiflexion / Plantarflexion: Upward/downward movement of the foot at the ankle.

• Inversion / Eversion: Turning the sole of the foot inward/outward.

• Elevation / Depression: Lifting/lowering a body part (e.g., shoulders).

• Protraction / Retraction: Moving a body part forward/backward (e.g., jaw).

Muscular System

Muscle Tissue Types

• Skeletal Muscle: Voluntary, striated muscle attached to bones for movement.

• Cardiac Muscle: Involuntary, striated muscle found only in the heart.

• Smooth Muscle: Involuntary, non-striated muscle found in walls of hollow organs.

Microscopic Structure of Muscle

• Sarcomere: The functional contractile unit of muscle fiber, defined by Z discs.

• Actin (Thin Filaments): Protein filaments involved in contraction.

• Myosin (Thick Filaments): Protein filaments that interact with actin for contraction.

• A Band: Dark area; length of thick filaments.

• I Band: Light area; contains only thin filaments.

• Z Disc: Defines the boundary of each sarcomere.

Major Muscles to Identify

Students must be able to identify the following muscles on models and diagrams. For muscles in bold, know their origin, insertion, action, and location.

• Head, Neck, Trunk: Temporalis, Masseter, Frontalis, Orbicularis oris, Trapezius, Sternocleidomastoid, Rectus abdominus, External oblique, Internal oblique

• Chest, Shoulder Girdle, Arm: Deltoid, Latissimus dorsi, Pectoralis major, Pectoralis minor, Serratus anterior, Rhomboids, Subscapularis, Supraspinatus, Infraspinatus, Teres Minor, Teres major, Triceps brachii, Biceps brachii, Brachialis, Brachioradialis, Pronator teres, Flexor carpi radialis, Palmaris longus, Flexor carpi ulnaris, Extensor carpi radialis longus, Extensor carpi radialis brevis, Extensor carpi ulnaris, Extensor digitorum

• Pelvic Girdle, Hip, Leg: Sartorius, Tensor fascia latae, Rectus femoris, Vastus lateralis, Vastus medialis, Gracilis, Gluteus medius, Gluteus maximus, Semitendinosus, Semimembranosus, Biceps femoris, Gastrocnemius, Extensor Digitorum Longus, Soleus, Tibialis anterior

• Other Structures: Achilles (calcaneal tendon), Patellar tendon, Iliotibial band

Muscle Origin, Insertion, and Action

• Origin: The fixed attachment point of the muscle.

• Insertion: The movable attachment point.

• Action: The movement produced when the muscle contracts.

Example: The biceps brachii originates on the scapula, inserts on the radius, and flexes the forearm at the elbow.

System Relationships: Bones, Muscles, and Joints

How Bones, Muscles, and Joints Produce Movement

Movement is produced by the coordinated action of bones, muscles, and joints. Muscles contract to pull on bones, which act as levers at joints (articulations).

• Bones: Serve as levers and points of attachment for muscles.

• Joints: Act as fulcrums, allowing movement in specific directions.

• Muscles: Generate force to move bones at joints.

Example: During elbow flexion, the biceps brachii contracts, pulling the radius toward the humerus at the elbow joint (a hinge joint).

Summary Table: Major Bones of the Axial and Appendicular Skeleton

Bone Group	Name of Bone	Bone Type	Number of Bones	Notes
Axial: Skull (Cranial)	Frontal, Parietal, Occipital, Temporal, Sphenoid, Ethmoid, Sutural	Flat	Varies	Some contain sinuses
Axial: Skull (Facial)	Mandible, Maxillary, Zygomatic, Nasal, Lacrimal, Palatine, Vomer	Varies	Varies	Mandible contains sinus
Axial: Vertebral Column	Cervical (7), Thoracic (12), Lumbar (5), Sacral (5 fused), Coccygeal (2-4)	Irregular	Varies	Supports trunk, protects spinal cord
Axial: Thoracic Cage	Sternum, Ribs (24: 12 pairs)	Flat	25	True, false, and floating ribs
Appendicular: Pectoral Girdle	Clavicle, Scapula	Flat	4	Shoulder girdle
Appendicular: Upper Limb	Humerus, Ulna, Radius, Carpals, Metacarpals, Phalanges	Long/Short	60	Pollex (thumb) has 2 phalanges
Appendicular: Pelvic Girdle	Ilium, Ischium, Pubis (fused as coxal bones)	Flat/Irregular	6	Forms acetabulum (hip socket)
Appendicular: Lower Limb	Femur, Patella, Tibia, Fibula, Tarsals, Metatarsals, Phalanges	Long/Short/Sesamoid	60	Hallux (big toe) has 2 phalanges

Key Study Strategies

• Understand the structure, location, and function of each bone, joint, and muscle.

• Practice identifying structures on models, diagrams, and slides.

• Connect how bones, joints, and muscles work together to produce movement.

• Be able to explain the principle of complementarity: how structure supports function.

Additional info: For exam preparation, focus on the origin, insertion, and action of bolded muscles, and be able to classify joints by both structure and function. Practice articulating bones to form joints and identifying movements possible at each joint type.