CEAS Human Anatomy & Biomechanics 1 — Questions and Answers
Question 1: The lumbar spine consists of how many vertebrae?
- Four (L1–L4)
- Five (L1–L5) (Correct answer)
- Six (L1–L6)
- Seven (C1–C7)
Correct answer: Five (L1–L5)
The lumbar spine contains five vertebrae (L1–L5), which bear the greatest compressive loads and are most vulnerable to work-related injury.
Question 2: The carpal tunnel is bounded on three sides by carpal bones and on the palmar surface by which structure?
- Extensor retinaculum
- Flexor retinaculum (transverse carpal ligament) (Correct answer)
- Annular ligament
- Palmar aponeurosis
Correct answer: Flexor retinaculum (transverse carpal ligament)
The flexor retinaculum (transverse carpal ligament) forms the roof of the carpal tunnel on the palmar side, and tightening of this structure compresses the median nerve.
Question 3: In seated workstation ergonomics, the 'hip angle' is defined as the angle between:
- The trunk and the floor
- The thigh and the lower leg
- The trunk and the thigh (Correct answer)
- The foot and the ankle
Correct answer: The trunk and the thigh
The hip angle is formed between the trunk and the thigh; a range of approximately 90–110° is recommended for a neutral, low-stress seated posture.
Question 4: Which spinal structure primarily absorbs compressive forces and allows movement between adjacent vertebrae?
- Facet joint
- Intervertebral disc (Correct answer)
- Spinous process
- Transverse process
Correct answer: Intervertebral disc
The intervertebral disc, composed of the nucleus pulposus and annulus fibrosus, acts as a hydraulic shock absorber between vertebral bodies.
Question 5: Ulnar deviation of the wrist describes movement of the hand toward:
- The thumb (radial) side
- The little finger (ulnar) side (Correct answer)
- The dorsal (back) surface
- The palmar (front) surface
Correct answer: The little finger (ulnar) side
Ulnar deviation moves the hand toward the ulnar (little finger) side and is a posture commonly associated with elevated risk of carpal tunnel syndrome.
Question 6: When a worker holds a load at arm's length rather than close to the body, the primary biomechanical effect on the lumbar spine is:
- Reduced compressive force because the load is distributed across a wider area
- No change because the object's weight is the same
- Increased spinal moment (torque) due to a greater moment arm (Correct answer)
- Reduced lower-back muscle activation
Correct answer: Increased spinal moment (torque) due to a greater moment arm
A longer moment arm multiplies the torque that spinal muscles must generate to maintain balance, greatly increasing lumbar compressive and shear forces.
Question 7: Neutral wrist posture in ergonomic guidelines is typically defined as approximately:
- 90° of wrist flexion
- 0–15° of extension with 0–5° of ulnar deviation (Correct answer)
- 30° of ulnar deviation
- Maximum pronation with 45° of flexion
Correct answer: 0–15° of extension with 0–5° of ulnar deviation
Neutral wrist posture (0–15° extension, minimal ulnar deviation) minimizes pressure on tendons and the median nerve within the carpal tunnel.
CEAS Human Anatomy & Biomechanics 1
The lumbar spine consists of how many vertebrae?