week 3 ana

Articulation (Joint)

Any point where two bones meet. Joints are usually named for the bones that form them. Example: the atlas and occipital bone form the atlanto-occipital joint.

Arthrology

The study of joint structure, function, and dysfunction.

Biomechanics

The study of movements and mechanics of the body.

Fibrous Joint

A joint where collagen fibers bind adjacent bones. These joints allow little to no movement. Example: sutures tightly connect the bones of the skull.

Cartilaginous Joint

A joint where two bones are connected by cartilage and have limited/slight movement. Examples include costal cartilage, the pubic symphysis, and intervertebral discs.

Cartilaginous Joint Cartilage

Hyaline cartilage occurs in structures such as costal cartilage. Fibrocartilage occurs in the pubic symphysis and intervertebral discs.

Synovial Joint

The most structurally complex type of joint. It contains a fluid-filled joint cavity and can range from limited to free movement. Examples include the shoulder, hip, elbow, and knee.

Why are synovial joints important?

They provide much of the body's movement. Their mobility allows activities such as walking, reaching, bending, and rotating, although greater mobility can come with decreased stability.

Articular Cartilage

A layer of hyaline cartilage covering the facing surfaces of bones inside a synovial joint. It provides a smooth surface where the bones meet.

Joint Cavity

The narrow, fluid-filled space between the articulating bones of a synovial joint. It contains synovial fluid.

Synovial Fluid

A viscous, slippery fluid inside the joint cavity. It lubricates the joint to reduce friction, nourishes articular cartilage, and helps remove waste.

Joint/Articular Capsule

Surrounds a synovial joint and encloses the articulating bones and joint cavity. It consists of an outer fibrous capsule and an inner synovial membrane.

Outer Fibrous Capsule

The tough, ligamentous outer layer of the joint capsule. It encloses the articulating bones and contributes to joint stability.

Synovial Membrane

The inner layer of the joint capsule. It contains cells that produce synovial fluid.

Tendon

Connective tissue that attaches muscle to bone. Tendons can cross joints and are important for movement and joint stability.

Ligament

Rope-like connective tissue that connects bone to bone. Ligaments help stabilize joints and restrict excessive or unwanted movement.

Tendon vs. Ligament

Tendon = muscle to bone. Ligament = bone to bone. Both can cross a joint and contribute to joint stability.

Bursa

A fibrous sac filled with synovial fluid that reduces friction and cushions tissues. Found between adjacent muscles or where tendons pass over bone.

Tendon Sheath

An elongated bursa through which a tendon runs, helping the tendon move with less friction.

Ball-and-Socket Joint

One bone has a hemispherical head that fits into a cup-like depression of another bone. It allows movement in all 3 planes. Examples: shoulder and hip.

Condylar Joint

An oval convex surface on one bone fits into a similarly shaped depression on another. Examples: radiocarpal joint and metacarpophalangeal joints.

Saddle Joint

Both articulating surfaces are shaped like a saddle. Examples: base of the thumb and sternoclavicular joint.

Plane/Gliding Joint

Adjacent bone surfaces slide over one another. Examples: joints between the carpal bones and between the tarsal bones.

Hinge Joint

A convex surface of one bone fits into the concave surface of another. Primarily allows movement in one plane, especially flexion and extension. Examples: elbow, knee, and interphalangeal joints.

Pivot Joint

A projection of one bone fits into a ring-like ligament of another and rotates around its longitudinal axis. Examples: proximal radioulnar joint and atlantoaxial joint.

Flexion

Movement that decreases the angle between two bones. Example: bending the elbow or knee.

Extension

Movement that increases the angle between two bones. Example: straightening the elbow or knee.

Shoulder Flexion

Anterior movement of the arm at the shoulder in the sagittal plane.

Shoulder Extension

Posterior movement of the arm at the shoulder in the sagittal plane.

Spinal Flexion

Forward bending of the head or trunk.

Spinal Extension

Backward bending of the head or trunk.

Lateral Flexion

Bending the head or trunk to the right or left side.

Right and Left Rotation

Twisting the head or waist toward the right or left.

Abduction

Movement of a body part away from the body's medial plane or midline. Example: raising an arm out to the side.

Adduction

Movement of a body part toward the body's medial plane or midline. Example: bringing an arm back toward the body.

Finger Abduction

Spreading the fingers apart.

Finger Adduction

Bringing the fingers together.

Elevation

Moving a body part upward vertically. Example: raising the shoulders in a shrug.

Depression

Moving a body part downward. Example: lowering the shoulders after a shrug.

Protraction

Moving a bone or body part anteriorly on a horizontal plane.

Retraction

Moving a bone or body part posteriorly on a horizontal plane.

Circumduction

One end of an appendage remains relatively stationary while the other end makes a circular motion.

Rotation

A bone turns or spins around its longitudinal axis.

External/Lateral Rotation

The anterior surface of a bone rotates away from the body's midline.

Internal/Medial Rotation

The anterior surface of a bone rotates toward the body's midline.

Pronation

Forearm rotation that turns the palm posteriorly/downward. During pronation, the radius crosses over the ulna.

Supination

Forearm rotation that turns the palm anteriorly/upward. During supination, the radius and ulna become parallel.

Pronation vs. Supination

Pronation = palm posterior/down and radius crosses ulna. Supination = palm anterior/up and radius and ulna are parallel.

Radial Deviation

Tilting the hand toward the thumb/radius side.

Ulnar Deviation

Tilting the hand toward the little-finger/ulna side.

Opposition

Moving the thumb across the palm so it can touch the tips of the other fingers.

Reposition

Returning the thumb from opposition back toward anatomical position.

Dorsiflexion

Raising the foot/toes toward the shin at the ankle.

Plantar Flexion

Pointing the foot/toes downward at the ankle.

Inversion

Lifting the medial border of the foot so the sole faces medially, toward the opposite foot.

Eversion

Lifting the lateral border of the foot so the sole faces laterally, away from the opposite foot.

Glenohumeral Joint

The shoulder joint formed by the head of the humerus articulating with the glenoid cavity of the scapula. It is a ball-and-socket joint capable of movement in all 3 planes.

Why is the shoulder highly mobile?

Its ball-and-socket structure allows movement in multiple directions. It is the most mobile joint in the body, but this mobility sacrifices stability.

Shoulder Mobility vs. Stability

The shoulder is designed for a large range of motion, so it sacrifices stability for mobility. Structures around the joint help keep the humeral head positioned against the glenoid cavity.

Glenoid Labrum

A ring of fibrocartilage around the glenoid cavity of the scapula. It deepens the shoulder socket and helps improve stability.

Transverse Humeral Ligament

Stretches between the greater and lesser tubercles of the humerus and forms a tunnel for the biceps brachii tendon.

Biceps Brachii Tendon at the Shoulder

Passes through the tunnel created by the transverse humeral ligament. It is an important stabilizer because it helps hold the humerus against the glenoid cavity.

Subdeltoid Bursa

Located under the deltoid muscle. It cushions tissues and reduces friction during shoulder movement.

Subacromial Bursa

Located under the acromion process. It reduces friction as shoulder structures move beneath the acromion.

Subcoracoid Bursa

Located under the coracoid process. It cushions tissues and reduces friction during shoulder movement.

Subscapular Bursa

Located under the tendon of the subscapularis. It reduces friction as the tendon moves.

Four Shoulder Bursae

Subdeltoid = under deltoid; subacromial = under acromion; subcoracoid = under coracoid; subscapular = under subscapularis tendon.

Rotator Cuff

Four muscles whose tendons stabilize the shoulder: subscapularis, supraspinatus, infraspinatus, and teres minor.

Rotator Cuff Muscles

Subscapularis, supraspinatus, infraspinatus, and teres minor. The four can be remembered as SITS: supraspinatus, infraspinatus, teres minor, subscapularis.

How does the rotator cuff stabilize the shoulder?

The tendons of the four rotator cuff muscles fuse with the joint capsule and form a thick cap of connective tissue that holds the humeral head in place.

Why does the shoulder need extra stabilizing structures?

The shoulder sacrifices stability for mobility. The glenoid labrum, biceps brachii tendon, and rotator cuff help keep the humeral head associated with the glenoid cavity while allowing a large range of motion.

Elbow Joint

The elbow contains two articulations: the humeroulnar articulation functions as a hinge, while the radioulnar articulation functions as a pivot.

Humeroulnar Joint

The articulation of the humerus and ulna. It is a monoaxial hinge joint that mainly allows flexion and extension in one plane.

What movement occurs at the humeroulnar joint?

Mainly flexion and extension because it functions as a monoaxial hinge joint.

Olecranon Bursa

Located on the posterior side of the elbow near the olecranon. It reduces friction and eases the movement of tendons.

Radial/Lateral Collateral Ligament of Elbow

Located on the lateral side of the elbow and restricts unwanted side-to-side motion, helping stabilize the elbow.

Ulnar/Medial Collateral Ligament of Elbow

Located on the medial side of the elbow and restricts unwanted side-to-side motion, helping stabilize the elbow.

Radioulnar Joint

A pivot articulation between the radius and ulna. It allows the radius to rotate relative to the ulna during pronation and supination.

Annular Ligament

Encircles the head of the radius and attaches at each end to the ulna. It holds the radial head in position while still allowing it to rotate.

Why is the annular ligament important?

It keeps the head of the radius associated with the ulna while allowing the radial head to rotate during pronation and supination.

Proximal Radioulnar Joint

Located near the elbow where the radial head meets the radial notch of the ulna. The radial head rotates here during forearm rotation.

Radial Notch of Ulna

The area of the ulna where the radial head articulates at the proximal radioulnar joint.

Distal Radioulnar Joint

Located near the wrist where the ulna articulates with the ulnar notch of the radius.

Ulnar Notch of Radius

The area of the distal radius where it articulates with the ulna at the distal radioulnar joint.

How does the forearm rotate?

The proximal and distal radioulnar joints allow the radius to move relative to the ulna. During pronation the radius crosses the ulna; during supination they are parallel.

Hip/Coxal Joint

A ball-and-socket joint where the head of the femur fits deeply into the acetabulum. It is adapted for weight bearing and is more stable than the shoulder.

Hip vs. Shoulder

Both are ball-and-socket joints. The shoulder emphasizes mobility and sacrifices stability, while the hip has a deeper socket and is adapted for stability and weight bearing.

Acetabulum

The deep socket of the hip that receives the head of the femur. All three parts of the os coxa contribute to the acetabulum.

Acetabular Labrum

A ring of connective tissue around the acetabulum that extends/deepens the socket and contributes to hip stability.

Fovea Capitis

A pit on the head of the femur that provides the attachment site for the round ligament.

Round Ligament

Arises from the fovea capitis on the femoral head and attaches to the lower margin of the acetabulum.

Three Major Hip Ligaments

Iliofemoral, pubofemoral, and ischiofemoral ligaments. They support the hip articulation and are named for the bones associated with their attachments.

Iliofemoral Ligament

A supporting ligament of the hip associated with the ilium and femur.

Pubofemoral Ligament

A supporting ligament of the hip associated with the pubis and femur.

Ischiofemoral Ligament

A supporting ligament of the hip associated with the ischium and femur.

Why is the hip more stable than the shoulder?

The hip is adapted for weight bearing, and the femoral head fits into the deep acetabulum. The acetabular labrum further extends the depth of the socket.

Movements at the Hip

As a ball-and-socket joint, the hip can perform flexion, extension, abduction, adduction, medial rotation, lateral rotation, and circumduction.

Tibiofemoral/Knee Joint

The articulation between the femur and tibia. It functions primarily as a hinge for flexion and extension but can rotate slightly when the knee is flexed.

Why isn't the knee a perfect hinge?

It primarily performs hinge-like flexion and extension, but when the knee is flexed it can also rotate slightly.

Patellofemoral Joint

A gliding joint involving the patella. The patella slides during knee movement.