Ch.4 Skeletal System

Overview of the Skeletal System

The skeletal system is a fundamental component of the human body, providing structure, protection, movement, production, and storage. It consists of bones, cartilage, ligaments, and joints, each serving specific functions essential for health and mobility.

• Support: The skeleton forms the framework of the body, maintaining its shape and posture.

• Protection: Bones protect vital organs such as the brain, heart, and lungs from injury.

• Movement: Bones act as levers and joints as fulcrums, enabling movement when muscles contract.

• Production: The skeletal system produces blood cells in the bone marrow, including red blood cells, white blood cells, and platelets.

• Storage: Bones store minerals such as calcium and phosphorus, which are essential for various bodily functions.

Functions of Specific Bones

• Mandible (Lower jawbone): Supports chewing and speech (Support, Movement).

• Ribs: Protect the lungs and heart (Protection).

• Spinal column: Provides structural support and flexibility (Support, Movement).

• Femur (Thigh bone): Bears body weight and enables movement (Support, Movement).

Classification of Bones

Types of Bones

Bones are classified based on their shape and function. Most bones in the human body are long bones, but other types exist to serve specialized roles.

• Long Bones: Elongated shape; found in arms and legs (e.g., femur).

• Short Bones: Cube-shaped; found in wrists and ankles (e.g., carpals).

• Flat Bones: Thin and broad; found in the shoulder blade (scapula), ribs, and sternum.

• Irregular Bones: Complex shapes; found in vertebrae and facial bones.

• Sesamoid Bones: Develop within tendons; found in the kneecap (patella).

Examples of Bone Classification

• Femur: Long bone

• Sternum: Flat bone

• Carpals: Short bone

• Patella: Sesamoid bone

• Mandible: Irregular bone

Parts of the Skeleton

Skeletal Organization

The human skeleton contains 206 bones and is organized into two main parts: the axial skeleton and the appendicular skeleton. Each part has distinct functions and anatomical structures.

• Axial Skeleton: Includes the skull, vertebral column, and thoracic cage. Provides support and protection for the brain, spinal cord, and thoracic organs.

• Appendicular Skeleton: Includes the limbs and the pectoral and pelvic girdles. Facilitates movement and interaction with the environment.

Major Bones of the Axial Skeleton

• Skull: Cranium, maxilla (upper jaw), mandible (lower jaw)

• Spinal Column: Vertebrae, sacrum, coccyx (tailbone)

• Thoracic Cage: Ribs, sternum (breastbone)

Major Bones of the Appendicular Skeleton

• Pectoral Girdle: Clavicle (collarbone), scapula (shoulder blade)

• Upper Limbs: Humerus (upper arm), radius and ulna (forearm), carpals, metacarpals, phalanges (hand)

• Pelvic Girdle: Ilium, ischium, pubis

• Lower Limbs: Femur (thigh), patella (kneecap), tibia (shinbone), fibula (lower leg), tarsals, metatarsals, phalanges (foot)

Bone Markings

Surface Features of Bones

Bones have various markings that serve as attachment points for muscles, passageways for nerves and blood vessels, and articulation sites for joints.

• Head: Rounded end of a long bone that helps in joint formation.

• Condyle: Smooth, rounded projections at the lower end of a bone.

• Trochanter: Large, rough processes for muscle attachment.

• Neck: Area between the head and the trochanters.

Bone Depressions

• Fossa: Shallow depression at the surface of a bone.

• Fissure: Slit-like opening.

• Foramen: Smooth, rounded opening.

• Sinus: Hollow cavity within a bone.

Joints and Movements

Types of Joints

Joints, or articulations, are classified based on their degree of movement:

• Synarthrosis: Immovable joint (e.g., skull sutures).

• Amphiarthrosis: Slightly movable joint (e.g., intervertebral discs).

• Diarthrosis: Freely movable joint (e.g., shoulder, hip).

Joint Movements

Freely movable joints (diarthroses) allow a variety of movements, each described by specific medical terms.

• Abduction: Moving a body part away from the midline.

• Adduction: Moving a body part toward the midline.

• Flexion: Bending a joint, decreasing the angle between bones.

• Extension: Straightening a joint, increasing the angle between bones.

• Dorsiflexion: Bending the ankle upward.

• Plantar Flexion: Bending the ankle downward toward the sole.

• Inversion: Turning the sole of the foot inward.

• Eversion: Turning the sole of the foot outward.

• Pronation: Turning the palm or foot downward.

• Supination: Turning the palm or foot upward.

• Protraction: Moving a body part forward.

• Retraction: Moving a body part backward.

• Circumduction: Moving a body part in a circular motion.

• Rotation: Turning a body part around its axis.

Skeletal System: Word Building

Combining Forms

Medical terminology for the skeletal system often uses combining forms based on anatomical names and characteristics.

• crani/o: cranium

• humer/o: humerus

• sacr/o: sacrum

• tibi/o: tibia

• cervic/o: neck

• cost/o: ribs

• olecran/o: elbow

• condyl/o: knuckle

• chir/o: hand

• ped/o, pod/o: foot

• dactyl/o: finger, toe

• articul/o: joint

• myel/o: bone marrow, spinal cord

• spondyl/o: vertebra

• coll/a: glue

• syn/o: connect

• burs/o: sac

• acr/o: extremity

Characteristics and Conditions

• ankyl/o: stiff, fused

• scoli/o: crooked, curvature

• kyph/o: humpback

• lord/o: bent backward

• orth/o: straight

• fixat/o: fastened

• rheumat/o: discharge

• lith/o: stone

• por/o: pore

• prosthet/o: artificial part

Suffixes

• -clast, -clasia: to break

• -listhesis: slipping

• -phyte: growth

• -poiesis: formation

• -lysis: loosen

• -oid: resembling

• -dynia: pain

• -ion: process

• -ous: pertaining to

Skeletal System Vocabulary

Pathology and Fractures

• Rheumatoid arthritis: Autoimmune disease marked by joint inflammation.

• Genu valgum (Knock-knee): Knees touch, ankles apart.

• Genu varum (Bowleg): Knees angle out, ankles together.

• Gout: Acute arthritis marked by foot joint inflammation.

• Rickets: Disease causing weak, soft bones from vitamin D deficiency.

• Hallux: Great toe.

• Acetabulum: Cup-shaped socket in the pelvis forming the hip joint.

• Symphysis: Joint where two bones are connected by fibrocartilage.

• Comminuted fracture: Bone broken into three or more pieces.

• Compound fracture: Bone breakage through the skin.

• Compression fracture: Bone breakage from pressure leading to collapse.

• Greenstick fracture: Incomplete bone breakage, typical in children.

• Oblique fracture: Bone breakage at an angle.

• Transverse fracture: Complete bone breakage straight across.

Medical Procedures

Surgical and Diagnostic Terms

• Reduction: Realignment of bone fragments.

• Traction: Continuous pulling force to restore alignment.

• Spinal Fusion: Permanently joining multiple bones of the spine.

• DEXA Scan: Measures bone density using low-dose X-rays.

• CT Scan: Computerized scanning system providing cross-sectional and 3D images.

• MRI Scan: Body imaging method using radio waves in a magnetic field.

Summary Table: Bone Types and Functions

Summary Table: Types of Joints