Musculoskeletal System (Anatomy)

Question 1

Explain the difference between axial and appendicular skeletons

Answer 1

• The axial skeleton forms the central supporting axis of the body and includes the skull, auditory ossicles, hyoid bone, vertebral column, and thoracic cage.
• The axial skeleton protects internal organs.
• The appendicular skeleton includes the bones of the upper limb and pectoral girdle, and the bones of the lower limb and pelvic girdle.
• The appendicular skeleton facilitates movement.

Question 2

Classify the different types of bones according to shape and name specific bones within each group

Answer 2

• Long - humerus, femur, tibia
• Short - carpals, tarsals
• Flat - scapula, parietal
• Irregular - facial, vertebrae
• Sesamoid - patella
• Pneumatic - bones that contain air-filled spaces e.g sphenoid

Question 3

What are the subdivisions of fibrous joints and what movements do they permit

Answer 3

Sutures

• Can be classified as serrate, lap, and plane sutures.
• Only found between the flat, plate-like bones of the skull.
• Limited movement until about 20 years of age, after which they are immovable.

Syndesmoses

• Slightly movable joints.
• They are comprised of bones held together by an interosseous membrane e.g. the middle radioulnar and middle tibiofibular joint.
• They provide strength along the length of long bones and prevent them from separating.

Gomphoses

• Immovable joints.
• Can be found where the teeth articulate with their sockets in the maxillae or mandible.
• The tooth is held firmly in place by a fibrous periodontal ligament which allows the tooth to move a little under the stress of chewing.

Question 4

What are the subdivisions of cartilaginous joints and what movement do they permit

Answer 4

Synchondroses

• Also known as primary cartilaginous joints.
• Only involve hyaline cartilage.
• Immovable or slightly movable.
• Examples include the temporary joint between the epiphysis and diaphysis of a long bone in a child, and the attachment of the first rib to the sternum by a hyaline costal cartilage.

Symphyses

• Also known as secondary cartilaginous joints.
• Can involve fibrocartilage or hyaline cartilage.
• Slightly movable.
• Examples include the pubic symphysis in which the right and left pubic bones are joined by the interpubic disc, and the joint between the bodies of two vertebrae, united by an intervertebral disc.

Question 5

What are the subdivisions of synovial joints and what movements do they permit

Answer 5

Plane

• Bone surfaces are flat or only slightly concave and convex.
• Adjacent bones slide over each other and have relatively limited movement.
• Found between the carpal bones of the wrist, tarsal bones of the ankle, and the articular processes of the vertebrae.

Hinge

• Monaxial joints which move freely in one plane with very little movement in any other.
• Permits flexion and extension.
• Examples include the elbow, knee, and interphalangeal joints.

Pivot

• Monaxial joints in which a bone spins on its longitudinal axis.
• Examples include the atlantoaxial joint between the first two vertebrae and the proximal radioulnar joint.

Condyloid

• Biaxial joints, capable of movement in two planes.
• Permits flexion, extension, adduction, abduction, and circumduction.
• Examples include the radiocarpal joint of the wrist and the metacarpophalangeal joints at the bases of the fingers.

Saddle

• Concave and convex joint surfaces unite.
• Examples include the trapeziometacarpal joint and the sternoclavicular joint.

Ball and socket

• Multiaxial joints.
• Only examples are the shoulder (glenohumeral) and hip joints.

Question 6

Explain the different classification groups of skeletal muscle and name specific muscles within each group

Answer 6

Strap

• Muscle fibres run parallel to one another.
• The muscles have broad attachments compared to other muscle types.
• Not very strong but can shorten to about 40-60% of their resting length.
• Sternocleidomastoid, Sartorius, Rectus abdominis

Fusiform

• Wide and cylindrically shaped in the middle and taper off at the ends (spindle-shaped).
• The force produced is concentrated into a small area (relatively strong).
• Biceps brachii, Gastrocnemius

Convergent

• Arise from a broad area and converge to form a single tendon (allows for strength).
• Considered versatile as they are able to change the direction of pull depending on how the fibres are contracting.
• Pectoralis major

Unipennate

• All the fascicles approach the tendon from one side.
• The fascicles insert obliquely on a tendon that runs the length of the muscle (like the shaft of a feather).
• Higher force but smaller range of motion.
• Gluteus maximus, Palmar interosseous muscles of the hand

Bipennate

• The tendon runs in the centre of the muscle and the fascicles run obliquely to it from both sides.
• Allows even greater power but less motion range than unipennate.
• Rectus femoris, interosseous muscles between the carpal bones

Multipennate

• The tendon runs in the centre of the muscle and the fibres run obliquely to it from all sides and converge at a single point.
• Allows even greater power (more muscle fibres in a given length of muscle) but less motion range than unipennate.
• Deltoid

Sphincter

• Circular muscles that surround body openings.
• When they contract they constrict the opening.
• Orbicularis oculi, anal sphincters

Question 7

Describe the anatomical features of a typical synovial joint

Answer 7

• The facing surfaces of the two bones are covered in hyaline articular cartilage.
• The two bone surfaces are separated by a synovial cavity containing synovial fluid, and bound together by a fibrous capsule which is lined on the inside by synovial membrane.

Question 8

Describe the directional terms and movements of the body

Answer 8

• Flexion - a movement that decreases a joint angle, usually in the sagittal plane (e.g. bending the elbow so that the arm and forearm go from a 180 to 90 degrees angle).
• Extension - a movement that straightens a joint and returns a body part to the zero position (e.g. straightening the elbow).
• Hyperextension - further extension of a joint beyond the zero position.
• Abduction - the movement of a body part in the frontal plane away from the midline of the body (e.g. raising an arm to one side of the body).
• Hyperabduction - e.g. raising your arm high enough to cross it slightly over the front or back of your head.
• Adduction - movement in the frontal plane back toward the midline.
• Hyperadduction - e.g. crossing your ankles or your fingers.
• Elevation - a movement that raises a body part vertically in the frontal plane (e.g. shrugging your shoulders).
• Depression - a movement that lowers a body part vertically in the frontal plane.
• Protraction - the anterior movement of a body in the transverse (horizontal) plane (e.g. the shoulder protracts and retracts during push-ups).
• Retraction - the posterior movement of a body part in the transverse plane.
• Circumduction - one end of an appendage remains stationary while the other end makes a circular motion.
• Rotation - a movement in which a bone spins on its longitudinal axis (medial = internal rotation, lateral = external rotation).
• Supination (of the forearm) - a movement that turns the palm to face anteriorly (upward), and the radius is parallel with ulna.
• Pronation - causes the palm to face posteriorly (downward), and the radius to cross the ulna like an X.
• Dorsiflexion - movement of the foot so the toes point upward.
• Plantar flexion - movement of the foot so the toes point downward.
• Inversion - a foot movement that tips the soles medially.
• Eversion - a foot movement that tips the soles laterally.
• Opposition - means to move the thumb to touch the tip of one of the four fingers. Reposition is the return to zero position.