1. BLOCK 14 HISTOLOGY OF THE JOINTS
Dr N NAVSA
DEPARTMENT OF ANATOMY
R4-12 BMW

2. Joint Categories
Traditionally – joints (arthroses / articulations) are divided into 2 categories based on:
Type of material used
Type of movement allowed
Two categories are:
Synarthroses (non-synovial joints)
Diarthroses (synovial joints)

3. Synarthroses
The material used to connect the bony elements in synarthrodial joints is interosseous connective tissue (fibrous & cartilagenous)
Synarthroses are thus grouped into 2 divisions according to the type of connectives tissue

4. Diarthroses
The ends of the bony components are free to move in relation to one another because no cartilaginous tissue directly connects adjacent bony surfaces.
The bony components are indirectly connected to one another by means of a joint capsule that encloses the joint
Synovial joints also have accessory structures – cartilaginous discs, plates/menisci, labrums, fat pads, ligaments, tendons, etc.

5. CLASSIFICATION OF JOINTS
Fibrous joints
Cartilagenous joints
Synovial joints

6. Fibrous Joints Synarthroses Immobile Syndesmosis e.g. tibiofibular
Suturae e.g. skull
Gomphosis e.g. tooth
Synostosis – bones joined by fibrous tissue

7. FIBROUS JOINTS

8. Cartilagenous joints Amphiarthroses Restricted movement
Symphyseal joints
Pubic symphysis : bony elements covered by hyaline cartilage with fibrous cartilage in between
Intervertebral discs
Specialised symphysis – hyaline cartilage plates of vertebral bodies joined by ring of fibrous cartilage e.g. annulus fibrosus

9. CARTILAGINOUS JOINTS

10. Synovial Joints Diarthroses Mobile
Articular surfaces covered by hyaline cartilage
Fibrous capsule lined by synovial membrane
Fibrous layer (layers of collagen) of capsule connected to periosteum of bones
Synovial cavity with synovial fluid
Ligaments formed by irregular connective tissue
Menisci / articular discs of fibrous cartilage

11. Synovial Joints contd Synovial membrane:
Inner surface smooth / with folds (villi)
Contains blood vessels, lymphatic vessels, nerves
Cells about 1-6 layers on the inside
Type A cells: macrophages
Type B cells: fibroblasts which form synovial fluid

12. SYNOVIAL JOINTS

13. HUMAN DEVELOPMENT TEXTBOOKS
Medical Embryology by J Langman 4th edn
Chapter 9 : Skeletal system p123
Chapter 10 : Muscular system p138
The Developing Human by KL Moore 4th edn
Chapter 15 : The skeletal system p334
Chapter 16 : The muscular system p350

14. NORMAL DEVELOPMENT

15. SKELETAL SYSTEM 3rd wk Mesoderm – series of blocks = somites
Differentiation
Sclerotome = ventromedial
Dermatome = dorsolateral
4th wk-sclerotome cells mesenchyme=conn tissue
Migration

16. SKELETAL SYSTEM Sclerotome cells migrate Bone formationMesenchyme
Fibroblasts (matrix formation)
Chondroblasts (cartilage formation)
Osteoblasts (bone formation)
Bone formationMesenchyme
Bone can also form in somatic mesoderm of body wall

17. LIMBS 5th wk – limb buds Initially – mesenchyme core surr by ecto
Apex of bud thickened=ectodermal ridge
Ridge influences underlying mesenchyme
Rapid growth & differentiation
6th wk – terminal end of buds flat
= hand and foot plates

18. LIMBS Tissue disappearance in radial grooves
= fingers & toes
External shape is established
6th wk – hyaline cartilage model
End of embryonic period
endochondral ossification
12th wk – primary ossification centers

19. LIMBS Ossification progresses from primary center To the ends At birth
Diaphysis completely ossified
Epiphyses cartilaginous
Cartilage plate inbetween = epiphyseal plate
Latter NB for growth in length
Full length – plate disappears, epiphyses unite

20. Clinical application Fracture vs Normal development
Determination of proper maturation age
Hand and wrists commonly used to determine “bone age”

21. HUMAN DEVELOPMENT ABNORMALITIES

22. LIMB ABNORMALITIES Amelia – 1 or 2 extremities are absent
Meromelia – hands & feet attached to trunk
Micromelia – all extremities present but abnormally short
Polydactyly – extra fingers or toes
Syndactyly – abnormal fusion
Lobster claw – abn cleft betw 2nd & 4th metacarpal (MC) bones & sift tissues; 3rd MC & phalanges almost always absent; thumb, index finger, 4th, 5th finger may be fused.
Club foot – sole in, foot add & plantar flexed