Joints of the Skeletal System

1. Joints of the Skeletal System Chapter 8

2. What’s a Joint? Is it legal? • Functional junctions between bones • Also called articulations • Classified by the type of tissue that attaches the bones at the junction • Also classified by the way in which they move at

3. Joints Classified by Tissue • Fibrous Joints • Dense connective tissue abundant in collagenous fibers found in these joints • Usually found between bones that lie very close to each other • 3 types of fibrous joints:Syndesmosis, Suture and Gomphosis • Cartilaginous Joints • Either Hyaline cartilage or Fibrocartilage connects the bones in these joints • 2 types of cartilaginous joints:Synchondrosis and Symphysis • Synovial Joints • The most common type of joint in the skeletal system • Allow free movement • More complex than fibrous or cartilaginous joints • Consist of: 1) articular cartilage 2) Joint capsule 3) synovial membrane that secretes synovial fluid • 6 types of synovial joints: Ball-and-socket, Condyloid, Gliding joint, Hinge joint, Pivot joint, and Saddle joint.

4. Joints Classified by Degree of Movement • Synarthrotic – immovable • Amphiarthrotic – partially movable • Diarthrotic – freely movable

5. Fibrous Joints • Syndesmosis • Amphiarthrotic (allows slight movement) • Bones in this type of joint are connected to each other with long stands of connective tissue that are collectively called an interosseous ligament (between bones) • Found in places such as the distal ends of fibula and tibia, between the tarsals and carpals

6. Syndesmosis Interosseous

7. Fibrous Joints • Suture • Synarthrotic - immovable • Exist between flat bones of the skull only – joined by a thin layer of dense connective tissue • Starts out as a fontanel – wide membranes of dense connective tissue between the skull bones, and allows compression of skull during childbirth, as well as room for growth • Fontanels are replaced by sutures

8. Sutures

9. Fibrous Joints • Gomphosis • Synarthrotic - immovable • A strange joint that is formed when a cone-shaped process of a bone is located within a socket of another bone • The root of a tooth located within the jawbone and held together by the periodontal ligament is a good example

10. Gomphosis Tooth enamel Blood vessels and nerve endings Periodontal ligament Root of tooth Jawbone

11. Cartilaginous Joints • Synchondrosis • Synarthrotic – immovable • Bands of hyaline cartilage join parts of bones • Much of this cartilage disappears upon maturity • Example: epiphyseal plate – replaced by bone when full growth is reached (before age 25) – no more movement after this point • Another example: articulation between manubrium and first rib by costal cartilage (also synarthrotic and permanent)

12. Synchondrosis

13. Cartilaginous Joints • Symphysis • Amphiarthrotic – slightly movable • Bones that meet at these joints have a layer of hyaline cartilage covering their ends • The hyaline cartilage is also attached to a pad of fibrocartilage which allows a “spring” to movement • Examples: Pubic symphasis and joints formed between adjacent vertebrae separated by intervertebral discs Intervertebral discs are also made up of fibrocartilage that surrounds a gelatinous core

14. Symphysis

15. Synovial Joints • Diarthrotic – freely moving • Most common type of joint in the body • More complex than fibrous and cartilaginous joints • Consist of: • Articular cartilage • Joint capsule • Synovial membrane

16. Synovial Joints • Articular cartilage – made up of hyaline cartilage and cover the articular surfaces of bones in the joint – these bone ends are made up of spongy bone (like in epiphysis). The articular cartilage minimizes friction and wear • Joint Capsule – Holds the bones in a synovial joint together. • The outer layer of the capsule is made up of dense connective tissue and reinforced with collagenous fibers called ligaments. The outer layer attaches to the periosteum of the bones in the joint • A inner layer of the joint capsule is made of a shiny vascular lining of loose connective tissue called the synovial membrane • Synovial Membrane – only a few cells thick, surrounds a closed sac called the synovial cavity that is filled with synovial fluid (secreted by the cells of the synovial membrane

17. A Typical Synovial Joint (Joint)

18. Some synovial joints… • Are divided (partially or completely) into 2 compartments by discs of fibrocartilage called menisci or meniscus (singular). These are located between the articular surfaces of the bones • Found in joints like the knee, where the menisci cushion the articulating surfaces • Other synovial joints have synovial fluid filled sacs called bursae near them – usually between the skin and the bones of the synovial joint

19. Meniscus and Bursa

20. Menisci are crescent-shaped and attach to the joint capsule on its lateral sides View of menisci from the top

21. Synovial fluid • A thick, stringy fluid found in the cavities of synovial joints. With its egg-like consistency (synovial comes from Latin for “egg"), synovial fluid reduces friction between the articular cartilage and other tissues in joints to lubricate and cushion them during movement. • Normal synovial fluid contains hyaluronic acid and a glycoprotein called Lubricin • Synovial fluid is secreted by cells of the synovial membrane and supply nutrients to the articular cartilage (remember – the synovial membrane is made of loose connective tissue and therefore has blood vessels)

22. Arthrocentesis: extraction of synovial fluid from joint The sample can be examined to determine the cause of joint problems

23. cloudy but translucent inflammatory synovial fluid taken from a patient with rheumatoid arthritis (left) and gout (right) respectively. pus-like fluid aspirated from a patient with acute bacterial infectious arthritis

24. colorless, clear synovial fluid from a patient with osteoarthritis accompanied by a low synovial-fluid white cell count bloody fluid aspirated from a patient with a tibial fracture into the joint space

25. Types of Synovial Joints • Hinge Joint • Movement in one plane only • Convex surface of one bone fits into concave surface of another • Example: trochlea of humerus into trochlear notch of ulna

26. Gliding Joint • Articulating surfaces of both bones in this joint are almost flat – or maybe very slightly curved • Back-and-forth and twisting movements • Example – carpals, tarsals, vertebrae, clavicle

27. 3. Saddle Joint • Between bones that have both concave as well as convex regions on their articulating surfaces • 2 planes of movement • Forward and back • Side-to-side

28. 4. Ball-and-Socket Joint • Bone with a round protrusion at the articular end fits into a cup-shaped cavity of another bone • Movement in all planes • Example: femur head and acetabulum of coxa

29. 5. Pivot Joint • Cylindrical surface of one bone rotates within another bone • Examples: the dens (odontoid process) of the axis within a facet of the atlas

30. 6. Condyloid Joint • A condyle of one bone articulates with an elliptical cavity of another bone • Example: Joints between carpals and metacarpals, Occipital condyles with facets of atlas

31. Types of Joint Movement • Flexion – Bending the lower limb at the knee or bending the hand downward at the wrist • Extension – Straightening lower limb at the knee or straightening the hand at the wrist • Hyperextension – Moving head upward, toward back or hand toward upper arm • Dorsiflexion – bending foot upward, toward the shin • Plantar Flexion – bending foot downward, toward the heel • Abduction – Moving a leg away from midline, horizontally • Adduction – Returning leg from horizontal position back to midline • Rotation – twisting head from side to side • Circumduction – moving finger in a circular motion without moving hand • Supination – palms facing anteriorly • Pronation – palms facing posteriorly • Eversion – Pushing foot away from body laterally • Inversion – Pushing foot laterally toward body (medially) • Protraction – Pushing chin forward • Retraction – Pulling chin back • Elevation – Raising, Shrugging shoulders • Depression – lowering, drooping shoulders

32. Gliding

33. Flexion

34. Supination vs. Pronation Supination: Palm faces upward Pronation: Palm faces downward

35. Extension, Hyperextension, and Flexion Another example: raising and lowering of hand, without moving arm

36. Dorsiflexion vs. Plantar flexion

37. Abduction, Adduction, and Circumduction

38. Rotation

39. Inversion vs. Eversion

40. Protraction vs. Retraction

41. Elevation vs. Depression Another example: Shrugging and relaxing of shoulders

42. Opposition

43. Examples of Synovial Joints I. Shoulder Joint – Includes the glenoid cavity of the Scapula and the head of the humerus. It is a Ball-and socket joint. • The joint capsule is attached to the circumference of the glenoid cavity of the scapula and the anatomical neck of the humerus • The joint capsule is reinforced by several ligaments and tendons of muscles to create a rotator cuff which supports the shoulder joint

44. Ligaments of the Shoulder Joint Acomion process • Coracohumeral – connects the coracoid process of the scapula to the greater tubercle of the humerus Greater tubercle of humerus Coracoid process Coracohumeral Ligament MADE UP OF CONNECTIVE TISSUE

45. 2. Glenohumeral Ligament • These 3 bands of ligament fibers extend from the edge of the glenoid cavity of the scapula tothe lesser tubercle and the anatomical head of the humerus Acromion Process Clavicle Coracoid process Glenohumeral Ligament MADE UP OF CONNECTIVE TISSUE

46. 3. Transverse Humeral Ligament Acomion process • Connects the greater and lesser tubercles of the humerus Greater tubercle of humerus Coracoid process Lesser Tubercle of humerus Transverse Humeral Ligament MADE UP OF CONNECTIVE TISSUE

47. 4. Glenoid Labrum Joint Capsule • Attaches along the circumference of the glenoid cavity of the scapula and forms a cup-like shape with a free rim Glenoid Labrum MADE OF FIBROCARTILAGE Glenoid cavity

48. Bursae • There are several bursae associated with the shoulder joint. The major ones are: • Subscapular bursa • Subdeltoid bursa • Subacromial bursa • Subcoracoid bursa

49. II. Elbow Joint Has 2 articulations: • The hinge joint between the trochlea of the humerus and the trochlear notch of the ulna • The gliding joint between the capitulum of the humerus and the fovea on the head of the radius A joint capsule encloses the joint and it is reinforced by ulnar and radial ligaments and muscle fibers form the brachialis muscle

50. The Elbow Joint Capitulum Trochlea Trochlear notch