Comprehensive Study Notes on Skeletal Anatomy, Articulations, and Kinesiology

Course Schedule & Administrative Milestones

• SmartBook & APR Assignments:
  • Chapter 6 SmartBook and APR assignments are due Wednesday night.
  • Chapter 7 SmartBook and APR assignments are due Tuesday night.
• Upcoming Assessments:
  • The Lab Quiz focusing on bone anatomy is scheduled for next Wednesday.
  • Test 3 is scheduled for Monday, October 5, and covers Chapters 6, 7, and 8 (Bones, Muscles, and Nervous System).

The Thoracic Cage & Sternum

• Thoracic Cage Structure:
  • Composed posteriorly of 12 thoracic vertebrae and 12 pairs of ribs.
  • Anteriorly bound by the sternum (breastbone) and costal cartilages.
• Functions of the Thoracic Cage:
  • Protects vital internal thoracic organs, primarily the heart and lungs.
  • Provides attachment points and structural support for the trunk, pectoral girdles (shoulders), and upper limbs.
  • Maintains structural flexibility: Costal cartilages allow the ribcage to flex during respiration, altering internal lung air pressure to enable movement of air into and out of the lungs.
• Rib Classifications (12 Pairs Total):
  • True Ribs (Ribs 1–7): The first seven pairs of ribs attach directly to the sternum in the center of the chest via individual costal cartilages.
  • False Ribs (Ribs 8–10): The middle three pairs do not connect directly to the sternum; their costal cartilages fuse to the cartilage of the rib directly superior.
  • Floating Ribs (Ribs 11–12): The final two pairs have no anterior attachment to the sternum or costal cartilage, ending freely within the lateral abdominal wall.
• Vertebral Attachment:
  • Each rib features two posterior attachment points articulating with the thoracic vertebrae (at the vertebral body and the transverse process) to stabilize the thoracic framework.
• Anatomy of the Sternum (Breastbone):
  • Manubrium: The superior portion of the sternum, triangular in shape, visually resembling a necktie knot.
  • Body: The elongated central portion of the sternum.
  • Xiphoid Process: The small, pointed inferior tip of the sternum (pronounced with a initial "Z" sound).

The Pectoral Girdle & Upper Extremity

• Pectoral Girdle Components:
  • Consists of two bilateral sets: left and right girdles.
  • Each girdle contains a Clavicle (collarbone) anteriorly and a Scapula (shoulder blade) posteriorly.
• Clavicle:
  • Connects medially to the superior aspect of the sternum's manubrium and laterally to the scapula at the shoulder joint.
  • Highly susceptible to structural fracture or severe bruising in automobile collisions due to diagonal seatbelt restraint forces.
• Scapula:
  • Posterior shoulder bone (mnemonic: scapula phonetically aligns with scalpel, indicating a blade shape—hence, "shoulder blade").
  • Glenoid Cavity: A shallow cup-like pocket on the lateral margin of the scapula that receives the head of the humerus. Due to its shallow depth, the shoulder joint is prone to dislocation but can typically be rearticulated relatively easily.
• Humerus (Upper Arm):
  • Anatomical Neck: The narrow ring located immediately inferior to the rounded head of the humerus.
  • Surgical Neck: A region located inferior to the anatomical neck and tubercles; designated as the surgical neck because it represents the most frequent fracture site requiring surgical intervention.
• Forearm (Radius and Ulna):
  • Ulna: The medial bone of the forearm (aligned with the pinky finger; mnemonic: ulna is a shorter word, corresponding to the smaller pinky finger). Slightly longer than the radius because its proximal end forms the posterior point of the elbow joint.
  • Radius: The lateral bone of the forearm (aligned with the thumb side in the standard anatomical position).
• Hand Architecture:
  • Carpals: 8 wrist bones forming the basal region of the hand.
  • Metacarpals: 5 long bones forming the structural foundation of the palm, numbered I through V.
  • Phalanges: Finger bones.
    • Thumb (Pollex): Contains only 2 phalanges (proximal and distal).
    • Digits II through V: Each contains 3 phalanges (proximal, middle, and distal).
    • Identification Tip: Counting bones outward from the palm distinguishes palm metacarpals from digit phalanges.

The Pelvic Girdle & Pelvic Dimorphism

• Components of the Pelvic Girdle:
  • Attaches the lower limbs to the axial skeleton.
  • Composed of two Coxal bones (hip bones), the Sacrum, and the Coccyx (tailbone, forming the inferior terminal extension of the vertebral column).
  • Terminology Distinction: Do not confuse the coccyx (tailbone) with the coxal bones (hip structures).
• Coxal Bone Subdivisions (3 Fused Bones):
  • Ilium: The large, superior, flared region of the hip bone (the structure felt when placing hands on hips).
  • Ischium: The inferior-posterior portion forming the primary weight-bearing ischial tuberosity ("butt bone"); bears body weight during upright sitting, distinct from the sacrum or coccyx.
  • Pubis: The anterior region of the coxal bone.
• Pubic Symphysis:
  • A cartilaginous joint formed by fibrocartilage connecting the left and right pubic bones along the anterior midline (prefix sym- or syn- denotes joining or coming together).
• Acetabulum:
  • A deep, cup-shaped socket located on the lateral aspect of the coxal bone that articulates with the rounded head of the femur.
  • Etymology: Derived from the Latin term for a "vinegar bowl."
• Sexual Dimorphism of the Pelvis:
  • Female Pelvis: Features a wider, larger, and more rounded pelvic inlet and outlet to accommodate childbirth; the coccyx is tilted posteriorly (backward) to prevent injury to an infant during delivery; acetabula are oriented differently.
  • Male Pelvis: Features a narrower, smaller pelvic cavity; the coccyx points more anteriorly (forward).
  • Anatomical differences manifest during puberty and serve as key markers in forensic anthropology.

The Lower Extremity & Foot Anatomy

• Femur:
  • The thigh bone; recognized as the largest, longest, and strongest bone in the human body. The head articulates directly into the acetabulum.
• Patella:
  • The kneecap; a sesamoid bone located within the joint complex between the femur and the lower leg bones.
• Lower Leg Bones (Tibia and Fibula):
  • Tibia: The larger, medial shin bone. Primary weight-bearing bone of the lower leg articulating directly with the femur at the knee joint.
    • Medial Malleolus: The prominent bony expansion at the distal end of the tibia forming the inner ankle bump.
  • Fibula: The slender, lateral lower leg bone positioned lateral and slightly posterior to the tibia.
    • Does not articulate with the knee joint directly and is non-weight-bearing; functions primarily for muscle attachment and lateral joint stabilization.
    • Lateral Malleolus: Distal terminus of the fibula forming the outer ankle bump.
    • Terminology Caution: Avoid combining terms into incorrect forms such as "tibula."
• Foot Architecture:
  • Tarsals: 7 ankle and heel bones.
    • Calcaneus: The heel bone; the largest individual tarsal bone.
  • Metatarsals: 5 bones comprising the instep/arch of the foot, designated with Roman numerals I through V.
  • Phalanges: Toe bones.
    • Great Toe (Hallux): Contains 2 phalanges.
    • Toes II through V: Each contains 3 phalanges, including the minute distal digit of the fifth toe.

Structural & Functional Classification of Joints

• Fibrous Joints (Sutures):
  • Synarthrotic (immovable) joints held together firmly by dense irregular connective tissue.
  • Examples: Cranial sutures of the skull; articulation of teeth within jaw sockets (gomphoses).
• Cartilaginous Joints:
  • Amphiarthrotic (slightly movable) joints connected by cartilage.
  • Individual movements between adjacent bones are slight, but cumulative movement across multiple sequential joints yields broad range of motion.
  • Examples: Intervertebral discs of the vertebral column; pubic symphysis (which undergoes hormone-induced relaxation during late pregnancy).
• Synovial Joints:
  • Diarthrotic (freely movable) joints featuring complex structural components.
  • Characterized by a fluid-filled articular/synovial cavity enclosed within a joint capsule, lined by a synovial membrane, with articular cartilage capping the epiphyses of articulating bones to absorb shock and prevent friction.

Types of Synovial Joints

• Plain (Gliding) Joints: Articular surfaces are flattened or slightly curved, permitting sliding/gliding movements across a single plane (unaxial). Example: Articulations between individual carpal bones.
• Condylar (Ellipsoid) Joints: An oval articular head fits into a complementary shallow oval depression, enabling movement across two planes (biaxial). Example: Articulation between the radius and carpal bones at the wrist joint.
• Hinge Joints: A convex cylindrical surface articulates within a concave depression, permitting movement restricted to a single plane (uniaxial), analogous to a door hinge. Examples: Elbow joint, knee joint.
• Saddle Joints: Both articulating surfaces contain concave and convex regions fitting together like a rider in a saddle, permitting movement in two planes (biaxial).
• Pivot Joints: A cylindrical bone rotates within a ring formed by another bone and a ligament, permitting rotational movement around a central longitudinal axis. Example: Rotation of the atlas around the axis at the neck.
• Ball-and-Socket Joints: A spherical head articulates within a deep cup-shaped socket, allowing the greatest multiaxial range of motion in all planes. Examples: Shoulder joint (glenoid cavity and humerus), hip joint (acetabulum and femur).

Terminology of Anatomical Movements

• Flexion: Decreasing the angle between two articulating bones (e.g., reducing a joint angle from $180^\circ$ to $90^\circ$ or $45^\circ$).
• Extension: Increasing the angle between articulating bones to return a flexed joint back toward anatomical position ($180^\circ$).
• Hyperextension: Extension of a joint beyond its standard anatomical alignment or neutral baseline angle.
• Circumduction: Movement of a limb such that the distal end traces a continuous circular pattern while the proximal point of origin remains stationary.
• Abduction: Movement of a body part laterally away from the longitudinal midline of the body (mnemonic: abduction is being taken away).
• Adduction: Movement of a body part medially toward the longitudinal midline of the body (mnemonic: "adding" back to the torso).
• Rotation: Turning a bone around its own central longitudinal axis.
  • Medial (Internal) Rotation: Turning anteriorly toward the midline.
  • Lateral (External) Rotation: Turning anteriorly away from the midline.
• Pronation & Supination:
  • Pronation: Rotation of the forearm causing the palm to face posteriorly or downward (corresponds to lying in a prone position, face down).
  • Supination: Rotation of the forearm causing the palm to face anteriorly or upward (corresponds to lying in a supine position, face up; mnemonic: "supine is fine").
• Inversion & Eversion:
  • Inversion: Medial movement of the foot turning the sole inward.
  • Eversion: Lateral movement of the foot turning the sole outward.
• Dorsiflexion & Plantar Flexion:
  • Dorsiflexion: Movement of the ankle lifting the foot so the toes point upward toward the shin/dorsum.
  • Plantar Flexion: Movement at the ankle depressing the foot so toes point downward (e.g., standing on tiptoes or dancing like a ballerina).