The Skeletal System

1
The Skeletal System

• Dr. Rodney Kennedy

2
Objectives

• Identify the partitions of the skeletal system
• Describe the functions of the skeletal system
• Describe the anatomical features of bones
• Classify bones based on their structure and
  function
• Describe the growth process of long bones
• Classify joints based on their structure and
  function
• (continued)

3
Objectives

• Sub-classify synovial joints according to their
  structure and function
• Describe the anatomical features of synovial
  joints
• Describe the functions of articular cartilage
• Describe the functions of synovial fluid
• Identify the factors that contribute to the
  stability of synovial joints
• Identify the factors that contribute to the
  flexibility of synovial joints

4
The human skeleton

• Two partitions
• axial skeleton
• appendicular skeleton

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The human skeleton
6
The human skeleton

• axial skeleton
• skull
• vertebrae
• sternum
• ribs
• appendicular skeleton
• bones composing the body appendages

7
The vertebral column

• Divided into 4 main regions
• Cervical (7)
• Thoracic (12)
• Lumbar (5)
• Sacral
• the 5 sacrum vertebrae and 4
• coccygeal vertebrae are fused to
• form one solid bone.

8
The human skeleton functions

• Mechanical functions
• support
• protection
• movement
• Physiological functions
• haemopoiesis (blood cell production)
• mineral storage calcium phosphorous

9
Categories of bone

• Compact cortical compact mineralized bone with
  low porosity found in the shafts of long bones
• Cancellous trabecular less compact bone with
  high porosity found in the ends of long bones
  and the vertebrae

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Categories of bone
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Types of bones

• short approximately cubical
• flat protect organs provide surfaces for
  muscle attachments
• irregular have different shapes to serve
  different functions
• long form the framework of the appendicular
  skeleton
• sesamoid develop within tendons

12
Short bones
13
Types of bones

• short approximately cubical
• flat protect organs provide surfaces for
  muscle attachments
• irregular have different shapes to serve
  different functions
• long form the framework of the appendicular
  skeleton
• sesamoid develop within tendons

14
Flat bones
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Types of bones

• short approximately cubical
• flat protect organs provide surfaces for
  muscle attachments
• irregular have different shapes to serve
  different functions
• long form the framework of the appendicular
  skeleton
• sesamoid develop within tendons

16
Irregular bones
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Types of bones

• short approximately cubical
• flat protect organs provide surfaces for
  muscle attachments
• irregular have different shapes to serve
  different functions
• long form the framework of the appendicular
  skeleton
• sesamoid develop within tendons

18
Long bones
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Types of bones

• short approximately cubical
• flat protect organs provide surfaces for
  muscle attachments
• irregular have different shapes to serve
  different functions
• long form the framework of the appendicular
  skeleton
• sesamoid develop within tendons

20
Sesamoid bones
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Structure of long bone

• Diaphysis is the long, hollow
• cylinder of hard, compact bone
• At the end of the diaphysis is an
• epiphysis
• The medullary marrow cavity
• in the center, is filled with marrow,
• and is surrounded by compact
• bone.

22
Structure of long bone

• Epiphyseal plate or growth plate
• is the cartilage plate in the long
• bones of children and adolescents.
• Periosteum a tough, fibrous
• tissue that covers the external
• surface of bone
• Endosteum a tough, fibrous
• tissue that covers the internal
• surface of bone

23
Bone growth and development

• How do bones grow in length?
• the epiphyses, or epiphyseal plates, are growth
  centers where mineral matter (calcium,
  phosphorous, magnesium) starts to replace
  cartilage, creating new bone
• the process is called ossification
• continues until the epiphysis closes during late
  adolescence or early adulthood early 20s

24
Bone growth and development

• How do bones grow in circumference?
• the inner layer of the periosteum, builds
  concentric layers of new bone on top of existing
  ones
• The changes in bone size and shape are the work
  of specialized cells called osteoblasts and
  osteoclasts

25
Joint classifications

• Fibrous or synarthrodial (immovable)

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Joint classifications

• Cartilaginous or amphiarthrodial (slightly
  moveable)

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Joint classifications

• Synovial or diarthrodial (freely moveable)

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Types of synovial joints

• Ball Socket
• spherical head round socket
• multiaxial movement
• Condyloid
• egg-shape articular surface oval concavity
• side-to-side, backforth movement
• Gliding
• articular surface in flat plane
• Short gliding movement

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Types of synovial joints
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Types of synovial joints

• Ball Socket
• spherical head round socket
• multiaxial movement
• Condyloid
• egg-shape articular surface oval concavity
• side-to-side, backforth movement
• Gliding
• articular surface in flat plane
• Short gliding movement

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Types of synovial joints
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Types of synovial joints

• Ball Socket
• spherical head round socket
• multiaxial movement
• Condyloid
• egg-shape articular surface oval concavity
• side-to-side, backforth movement
• Gliding
• articular surface in flat plane
• Short gliding movement

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Types of synovial joints
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Types of synovial joints

• Hinge
• cylindrical end of 1 bone fits into trough shape
  of other
• angular movement-1 plane
• Pivot
• round end fits into ring of bone ligament
• rotation on long axis
• Saddle
• articular surface both concave convex
• side-to-side, back-forth movement

35
Types of synovial joints
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Types of synovial joints

• Hinge
• cylindrical end of 1 bone fits into trough shape
  of other
• angular movement-1 plane
• Pivot
• round end fits into ring of bone ligament
• rotation on long axis
• Saddle
• articular surface both concave convex
• side-to-side, back-forth movement

37
Types of synovial joints
C1 C2
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Types of synovial joints

• Hinge
• cylindrical end of 1 bone fits into trough shape
  of other
• angular movement-1 plane
• Pivot
• round end fits into ring of bone ligament
• rotation on long axis
• Saddle
• articular surface both concave convex
• side-to-side, back-forth movement

39
Types of synovial joints
40
Structure of synovial joints

• They are characterized by
• articular cartilage a protective layer of dense
  white connective tissue covering the articulating
  bone surfaces
• articular capsule a double-layered membrane that
  surrounds the joint
• (continued)

41
Structure of synovial joints

• They are characterized by
• synovial fluid a clear, slightly yellow liquid
  that provides lubrication inside the articular
  capsule
• associated bursae small capsules filled with
  synovial fluid that cushion the structures they
  separate

42
Functions of articular cartilage

• it spreads loads over a wide area, thereby
  reducing contact stress
• it provides a protective lubrication that
  minimizes friction and mechanical wear at the
  joint

43
Fibrocartilage

• Soft-tissue discs or menisci that intervene
• between articulating bones, as exemplified by
• the menisci of the knee above

44
Functions of fibrocartilage

• distributing loads over joint surfaces
• improving the fit of articulations
• limiting slip between articulating bones
• protecting the joint periphery
• lubricating the joint
• absorbing shock at the joint

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Articular connective tissue

• tendons connect muscles to bones
• ligaments connect bones to other bones

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Joint stability

• Refers to the ability of a joint to resist
  abnormal
• displacement of the articulating bones.
• Factors that increase joint stability
• a closely reciprocating match of the articulating
  bone surfaces (stability is maximal when joints
  are in the close-packed position)
• a strong array of ligaments and muscle tendons
  crossing the joint
• absence of muscle fatigue

47
The Knee Joint
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Joint flexibility

• Refers to the relative ranges of motion allowed
• at a joint in different directions. Limited by
• Ligaments
• Muscles
• Bones
• Joint damage

49
Joint flexibility
Muscles that cross more than one joint e.g
hamstrings on hip flexion
50
Further Reading

• Chapter 10 from
• McGinnis, P. M. (2005) Biomechanics of sport and
  exercise. 2nd ed.
• ChampaignHuman Kinetics.