Structure and Function of Joints, Part 2

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PTA 1502: Functional Anatomy and Kinesiology:

Structure and Function of Joints Part 2 PTA 1502: Functional Anatomy and Kinesiology More about Joints

Axis of Rotation:

Axis of Rotation Axis rarely fixed in anatomical joints Critical to estimate axis of rotation Goniometry Exercise Prosthetics Orthotics Typically coincides with convex surface of joint

Composition of Joints:

Composition of Joints Connective tissue components Fibers Collagen Stiff: Ligaments, fascia, joint capsules, tendons Flexible: Hyaline cartilage Elastin Provide elasticity Certain ligaments ( spinal ligaments )

Connective Tissue Components:

Connective Tissue Components Ground Substance Water, GAG’s, solutes Provides for nutrient diffusion, resistance to compression Articular cartilage Cells Maintenance, repair Few in number; limited healing

Types of Connective Tissue:

Types of Connective Tissue Dense, irregular connective tissue Joint capsule Ligaments Fascia Tendons, less irregular than ligaments; parallel Articular Cartilage Ends of articulating bones (synovial joints) Fibrocartilage Intervertebral discs Symphysis pubis Menisci labrum Bone

Articular Cartilage:

Articular Cartilage Hyaline cartilage 1 – 7 mm thick, dependent upon location, load-bearing Avascular, aneural Poorly repaired when injured Distributes, disperses compressive forces Reduces friction


Fibrocartilage Intervertebral discs, labrum, menisci Help support, stabilize joints Dissipate compressive forces Shock absorber Aneural ( no pain ), except at periphery Vascular at periphery Limited repair to periphery ( meniscus ) Nourished by synovial fluid


Bone Functions Rigid framework of body Protects vital organs Assists with movement Attachment for muscles. Leverage Manufactures blood cells Ilium Vertebrae Sternum Ribs Stores Calcium, other minerals

Types of Skeleton:

Types of Skeleton Axial (Upright) 80 bones Head, Thorax, Trunk Appendicular 126 Bones Attaches to axial Extremities

Composition of Bone:

Composition of Bone 1/3 Organic (collagen) Gives elasticity 2/3 Inorganic (minerals) Gives strength Makes opaque on X-Ray

Compact Bone:

Compact Bone Hard Outer shell Completely covers Thick at shaft, thin at ends


Cancellous Porous / Spongy Contains trabeculae ( marrow ) Most of articular surfaces are cancellous bone

Structure of Bone:

Structure of Bone


Epiphysis Area at each end of diaphysis Tends to be wider than shaft Osseous in adults Cartilaginous in growing bone Epiphyseal plate Manufactures new bone/growth.


Diaphysis Main shaft Mostly compact bone (gives strength) Medullary canal, center Hollow, decreases weight Contains marrow Passage of nutrients

Endosteum :

Endosteum Membrane that lines medullary canal. Contains osteoclasts. Bone resorption


Metaphysis Flared portion at each end of diaphysis in long bones. Mostly cancellous bone Supports epiphysis

Types of Bones:

Types of Bones Long Bones: length > width Appendicular skeleton Tubular shaped with shaft and two bulbous ends ( epiphysis ) Metaphysis, epiphysis consist of cancellous bone covered by compact bone. Hyaline cartilage at articular surface

Short Bones:

Short Bones More equal dimensions of height, length, width. Cubical shape Large articular surface, typically articulate with >1 bone Makeup similar to long bones Wrist, ankle.

Flat Bones:

Flat Bones Very broad surface Not very thick 2 layers of compact bone, cancellous bone between Ilium, Scapula

Irregular Bones:

Irregular Bones Variety of mixed shapes Vertebra, sacrum don’t fit in other categories Cancellous bone, marrow, layer of compact bone.

Sesamoid Bones:

Sesamoid Bones Resemble shape of sesame seeds. Small Located where tendons cross ends of long bones. ( extremities ) Great toe

Review of Anatomical Descriptors:

Review of Anatomical Descriptors

Anatomical Descriptors:

Anatomical Descriptors Foramen Hole blood vessels, nerves, ligaments Fossa Hollow, depression Groove ditch-like groove tendons, blood vessels Meatus Canal, tube-like opening


Terminology Sinus air-filled cavity Condyle rounded, knuckle-like projection. Eminence projecting, prominence Facet flat, shallow articular surface Head rounded articular projection, beyond neck of bone.


Terminology Crest ridge, border Epicondyle prominence above, on condyle Line less prominent ridge Spine long, thin projection

Terminology :

Terminology Trochanter very large prominence, for muscle attachment. Tubercle small, rounded projection Tuberosity large, rounded projection

Effects of Aging, Other Factors:

Effects of Aging, Other Factors

Effects of Aging:

Effects of Aging Decreased rate of fiber, connective tissue repair Microtrauma accumulates over time Results in degenerative changes of tissue Decreased hydration of connective tissue Lower resistance to compressive forces Increased likelihood of adhesions between layers Decreased range of motion, flexibility Decreased bone metabolism Osteoporosis Slower healing of fractures

Effects of Immobilization:

Effects of Immobilization Arrangement of connective tissue fibers influenced by activity Align according to forces Immobilization produces random collagen formation, decreased range of motion Decreased strength of connective tissue Decreased bone density Decreased ligament strength

Joint Pathology:

Joint Pathology


Trauma Acute Trauma Occurs from a single event Tibiofemoral, talocrural, glenohumeral joints most susceptible Chronic Trauma Occurs over time, “ overuse syndrome ” Can cause chronic instability Can lead to other failures (meniscus tear, osteochondral defect, labral tear) Osteoarthritis

The End:

The End

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