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Unit 2 of 4 · B.Sc MLS Sem 2

Unit 2: Musculoskeletal system

Human Anatomy and Physiology-I notes · PTU syllabus (BMLS203-18)

3 min read5 topics10 exam questions
On this page
  1. Unit summary
  2. The skeletal system
  3. Structure of bone
  4. Joints
  5. Muscles
  6. Movements of the body
  7. Key terms
  8. Quick revision
  9. Important questions

Unit summary

Bones, joints and muscles support the body and move it. This unit covers the classification, structure and functions of the skeletal system, muscles and joints, and movements of the body.

After this unit you can

  • Classify bones and describe the skeleton
  • Describe the structure of bone
  • Classify joints and muscles
  • Describe body movements

PTU syllabus topics

  • Classification
  • structure and function of the skeletal system
  • muscles and joints
  • movements of the body
ClassificationTypes of joints
Joints

  • Fibrous (immovable)

    Sutures of the skull

  • Cartilaginous (slightly movable)

    Between vertebrae

  • Synovial: ball and socket

    Shoulder, hip

  • Synovial: hinge

    Elbow, knee

  • Synovial: pivot

    Between atlas and axis

1

Topic 1

The skeletal system

  • The adult skeleton has 206 bones — the axial skeleton (skull, vertebral column, ribs, sternum — 80 bones) and the appendicular skeleton (limbs and girdles — 126 bones).
Key termsFunctions of the skeleton
Support
Framework of the body
Protection
Skull guards the brain; ribs guard heart and lungs
Movement
Levers for muscles
Mineral storage
Calcium and phosphate
Blood formation
Red bone marrow (haemopoiesis)
Fat storage
Yellow marrow
ComparisonClassification of bones
Shape
Examples

Long

Longer than wide; shaft and two ends

Femur, humerus

Short

Cube-shaped

Carpals, tarsals

Flat

Thin plates

Skull bones, sternum, ribs, scapula

Irregular

Complex shapes

Vertebrae

Sesamoid

Within tendons

Patella

2

Topic 2

Structure of bone

  • Long bone: diaphysis (shaft) with a medullary cavity, epiphyses (ends) covered by articular cartilage, periosteum outside, endosteum inside.
  • Compact bone: Haversian systems (osteons) with central canals and lamellae; spongy bone: trabeculae containing red marrow.
Key termsBone cells
Osteoblasts
Form bone
Osteocytes
Mature cells in lacunae
Osteoclasts
Resorb bone
Osteoprogenitor cells
Stem cells
  • Vertebral column: 33 vertebrae — 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 4 coccygeal (fused).
3

Topic 3

Joints

ComparisonClassification of joints
Movement
Examples

Fibrous (synarthroses)

Immovable

Skull sutures

Cartilaginous (amphiarthroses)

Slightly movable

Intervertebral discs, pubic symphysis

Synovial (diarthroses)

Freely movable; joint capsule, synovial membrane and fluid, articular cartilage

Knee, shoulder, elbow

Key termsTypes of synovial joint
Ball and socket
Shoulder, hip — all directions
Hinge
Elbow, knee — one plane
Pivot
Atlas–axis — rotation
Gliding (plane)
Carpals
Saddle
Thumb carpometacarpal
Condyloid (ellipsoid)
Wrist
4

Topic 4

Muscles

  • The body has over 600 skeletal muscles, attached to bones by tendons; each has an origin (fixed end) and insertion (moving end).
ComparisonMuscle tissue
Skeletal
Smooth and cardiac

Appearance

Striated, multinucleated fibres

Smooth: non-striated spindle cells; cardiac: striated, branched, intercalated discs

Control

Voluntary

Involuntary

Location

Attached to skeleton

Smooth: viscera and vessels; cardiac: heart

  • Contraction (sliding filament theory): a nerve impulse releases acetylcholine; calcium released from the sarcoplasmic reticulum lets myosin heads bind actin and pull, using ATP — the sarcomere shortens.
5

Topic 5

Movements of the body

Key termsMovements at joints
Flexion and extension
Decreasing or increasing the angle — bending and straightening the elbow
Abduction and adduction
Away from or towards the midline
Rotation
Turning about an axis
Circumduction
Circular movement — shoulder
Pronation and supination
Palm down or up
Dorsiflexion and plantar flexion
Foot up or down
Inversion and eversion
Sole inward or outward

Key terms

Axial skeleton
Skull, vertebral column and thoracic cage
Osteon
Structural unit of compact bone
Synovial joint
Freely movable joint with a fluid-filled cavity
Insertion
Movable attachment of a muscle
Sarcomere
Contractile unit of muscle fibre

Quick revision

  • 206 bones; axial 80, appendicular 126; functions.
  • Long, short, flat, irregular, sesamoid bones; bone structure and cells; vertebrae.
  • Fibrous, cartilaginous, synovial joints; types of synovial joints.
  • Skeletal, smooth, cardiac muscle; sliding filament theory.
  • Flexion, extension, abduction, adduction, rotation and other movements.

Important exam questions

Practice questions written to the PTU exam pattern for this unit's syllabus: short answers (Section A style) and long answers (Sections B and C style).

Short-answer questions

  1. Q1.How many bones are there in the adult skeleton?
  2. Q2.Give two functions of the skeleton.
  3. Q3.Name the cells that resorb bone.
  4. Q4.Give an example of a hinge joint.
  5. Q5.What is the sliding filament theory?
  6. Q6.Distinguish abduction and adduction.

Long-answer questions

  1. Q1.Describe the classification and functions of bones.
  2. Q2.Describe the structure of a long bone.
  3. Q3.Classify joints with examples.
  4. Q4.Describe muscle types and the mechanism of muscle contraction.

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