Joints and its classification

Joints and its Major classification with examples
Key structure in Synovial joint

1. JOINTS SHAZIA REHMAN

2. INTRODUCTION Arthrology: Study of joints Joint: a junction between two or more bones or cartilages.

3. CLASSIFICATION OF JOINT Depending on the presence or absence of joint cavity. Joints are classified into two groups Synarthroses or Solid joint Diarthroses or Cavitated joint

4. Synarthroses Joints Types of connective tissue that binds the bones together 1.Fibrous Suture Syndesmoses Gomphoses 2. Cartilaginous Primary (Synchondroses) Secondary (Symphyses)

5. CLASSIFICATION OF DIARTHROSES These are cavitated joints also called Synovial joints 1) According to plane of movements 2) According to number of articulating bones 3) According to shape of articulating surfaces

6. According to plane of movements Uniaxial Biaxial Multiaxial According to number of articulating bones Simple joint Compound joint Complex joint

7. According to shape of articulating surfaces Plane joint Hinge joint Pivot joint Condylar joint Ellipsoid joint Saddle joint Ball and socket joint

8. Synarthroses immovable joints No joint cavity Also called fixed joint Further divided into Cartilaginous joint Fibrous joint

9. Cartilaginous joints Cartilaginous joint, the adjacent bones are united by cartilage, a tough but somewhat flexible type of connective tissue. These types of joints lack a joint cavity and involve bones that are joined together by either hyaline cartilage or fibrocartilage  

10. Primary ( Synchondroses ) Cartilaginous joints connected by hyaline cartilage are termed synchondroses . Eg Sternocostal joint

11. Secondary ( Symphyses ) A cartilaginous joint where the bones are joined by fibrocartilage is called a  symphysis Eg Pubic symphysis

12. Fibrous joint Bones united by fibrous tissue Fixed or immovable joints Fibrous joints have no joint cavity

13. Sutures A suture is a type of fibrous joint bound by fibers that only occurs in the skull (cranium). Depending on the shape of edge joining edge the sutures are further classified into various type Serrate suture Denticulate Suture Squamous Suture Plane Suture

14. Serrate suture Bony edges are saw like E.g Sagittal suture Denticulate Suture Bony edges have tooth like processes E.g Lambdoid Suture

15. Squamous Suture Bony edges overlap each other and beveled reciprocally Eg Temporo-Parietal suture Plane Suture Bony edges which fuse have flat surface Eg Intermaxillary suture

16. Gomphoses Peg and socket joint Fibrous joint in which a conical process or peg of one bone fits into a hole or socket in another bone. Roots of the teeth and alveolar socket of the jaw bones

17. Syndesmoses A syndesmoses joint is a fibrous joint where two bones are connected by band of strong ligaments or membrane (Interosseous membrane)

18. Diarthroses freely movable joints Cavitated joint Also called Synovial joint E.g (knee joint)

19. According to plane of movements Uniaxial Biaxial Multiaxial Allows for a motion in a single plane Allow movements in two planes Allows for the several directions of movement elbow joint flexion and extension wrist joint. (adduction and abduction) (flexion and extension). The shoulder and hip joints 

20. According to number of articulating bones Simple joint Compound joint Complex joint Two articulating surfaces More then two articulating surfaces a joint with a disc or a joint with 3 or more elements E.G Shoulder joint E.G Elbow joint E.G Knee joint

21. According to shape of articulating surfaces Plane Joints Articulating surfaces that are flat or slightly curved faces Movements Gliding movements Eg Carpal bones joint

22. Hinge Joints Slightly rounded end of one bone fits into the slightly hollow end of the other bone Movements Permit movement in one plane Eg Elbow joint

23. Pivot joints Pivot joints consist of the rounded end of one bone fitting into a ring formed by the other bone. Movements This structure allows rotational movement Eg Radioulnar joint

24. Condyloid joints An oval-shaped end of one bone fitting into a similarly oval-shaped hollow of another bone. Movements Allow in two planes Eg Radiocarpal joint

25. Saddle joints  Are so named because the ends of each bone resemble a saddle, with concave and convex portions that fit together. Movements Allow in two planes Eg Carpometacarpal joint

26. Ball-and-socket joints A rounded, ball-like end of one bone fitting into a cup-like socket of another bone Movements multiaxial joints Eg Shoulder joint

27. Key structure of Synovial joint The three main features of a synovial joint are: ( i ) articular capsule, (ii) articular cartilage, (iii) synovial fluid

28. Articular capsule A fibrous connective tissue structure that is attached to each bone just outside the area of the bone’s articulating surface. Synovial joints are characterized by the presence of a joint cavity. The walls of this space are formed by the  articular capsule. Synovial membrane Lining the inner surface of the articular capsule is a thin  synovial membrane . The cells of this membrane secrete  synovial fluid

29. Articular Cartilage The  articulating surfaces  of a synovial joint are covered by a thin layer of hyaline cartilage. Functions The articular cartilage has two main roles: ( i ) minimizing friction upon joint movement (ii) absorbing shock.

30. Synovial fluid   ( synovia = “a thick fluid”), a thick, slimy fluid that provides lubrication to further reduce friction between the bones of the joint. This fluid also provides nourishment to the articular cartilage, which does not contain blood vessels.  Volume of synovial fluid in large joint: 0.5 ml

31. Ligament Strong bands of fibrous connective tissue. Functions These strengthen and support the joint by anchoring the bones together and preventing their separation. Ligaments allow for normal movements at a joint, but limit the range of these motions, thus preventing excessive or abnormal joint movements.

32. Ligaments are classified based on their relationship to the fibrous articular capsule. Extrinsic ligament  is located outside of the articular capsule Intrinsic ligament  is fused to into the wall of the articular capsule Intracapsular ligament  is located inside of the articular capsule.

33. Additional Structures Associated with Synovial Joints A few synovial joints of the body have a fibrocartilage structure located between the articulating bones. This is called an  articular disc , which is generally small and oval-shaped, or a  meniscus , which is larger and C-shaped.  Functions Act as shock absorber They facilitate the occurrence of combined movement Adjust the unequal articulating surfaces

34. Bursae A bursa is a small sac lined by  synovial membrane , and filled with synovial fluid. They are located in regions where skin, ligaments, muscles, or muscle tendons can rub against each other, usually near a body joint . Function Bursae reduce friction by separating the adjacent structures, preventing them from rubbing directly against each other.

35. Bursae are classified by their location Subcutaneous bursa Submuscular bursa  Subtendinous bursa between the skin and an underlying bone Eg prepatellar bursa (knee joint) between a muscle and an underlying bone Eg trochanteric bursa (hip joint) between a tendon and a bone Eg subacromial bursa (shoulder joint)

36. Vasculature Arterial supply to synovial joints is via  articular arteries , which arise from the vessels around the joint. The articular arteries are located within the joint capsule, mostly in the synovial membrane. The  articular veins  accompany the articular arteries and are also found in the synovial membrane.

37. Nerve supply of Synovial joint Synovial joints have a rich supply from articular nerves. The innervations of a joint can be determined using Hilton's Law – 'the nerves supplying a joint also supply the muscles moving the joint and the skin covering their distal attachments.