3
4 4
4
7 Articular System
Joints, simply defi ned, are the meeting
places between bones. Th is simple defi nition describes a joint as any place
in the skeleton where one skeletal element contacts another skeletal element. It is important to understand that, as a part of this defi nition,
the bones never contact each other directly. Instead, there is always some other connective tissue between the bony contact
surfaces. Joints come in a wide variety of structural junctions, with an accompanying variety of functions.
Because joints have various functions and those
functions do not always deal with movement, it is illogical to defi ne joints by their movements. Th e best
method for classifying joints is based on their structure. Because the structure of joints includes the connective tissues between the neighboring bones, a
classifi cation based on the structure of those tissues
is logical. At the simplest level, there are two basic
ways bones connect with one another to form joints.
Either they are connected by solid masses of connective tissue, or they are bound together by a connective
tissue capsule, which surrounds a lubricated cavity between the adjoining bones.
Joints formed by a solid core of connective
tissue between the neighboring bones are called
synarthroses. Th ere are two subcategories of
synarthroses — fi brous joints, which have connective tissue cores of connective tissue proper, typically dense irregular connective tissue, and cartilage
joints, which use some form of cartilage as the
connecting tissue between the bones. Th e capsular joints, with their lubricated cavity, are called
diarthroses or synovial joints. Th ere are numerous subcategories of diarthroses, each
based on the structure and function of their
articular surfaces.
In addition to joints, this chapter will
also illustrate other closely related synovial
structures — bursae and synovial (tendon)
sheaths.
Find more information
about arthrology in
123
REAL ANATOMY
1
2
3
4
5
6
7
8
9
10
124
tissue binding the neighboring bones can vary considerably. Examples of fi brous joints are depicted on this and the facing
page. Gomphoses and sutures (the four different suture types are shown on the opposite page) have a very thin membrane
of collagenous connective tissue anchoring neighboring bony structures to one another. On the other hand, the syndesmoses between the tibia and fi bula — both the interosseous membrane and the tibiofi bular ligaments at the distal end — have
considerably more binding connective tissue. There is also an example of another syndesmosis, the interspinous ligament,
in the next section.
Fibrous joints are synarthrotic joints that
bind bone to bone with collagenous connective tissue. The amount of connective
Synarthrosis - Fibrous Joints
1 Periodontal membrane
2 Crown of tooth
3 Root of tooth
4 Gingiva
5 Mandible
6 Tibia
7 Fibula
8 Interosseous membrane
9 Anterior tibiofibular ligament of tibiofibular syndesmosis
10 Patellar ligament (cut)
Dento-alveolar syndesmosis or gomphosis
Sagittal section of tooth in mandible
Crural skeleton – tibia and fi bula
Anterior view
1
2
3
4
5
6
7
9
10
125
Squamous-type suture
Squamous or temporoparietal suture
Denticulate-type suture
Lamboidal or parieto-occipital suture
Serrate-type suture
Coronal or frontoparietal suture
Plane-type suture
Internasal suture
1
2
3
4
6
13
14
16 15
18
18
19
17
20
21
22
126
Sagittal section of head and trunk
Medial view
Synarthrosis - Cartilaginous Joints Like the fi brous joints, the
cartilaginous joints join
neighboring skeletal ele-
1 Intervertebral disc (symphysis)
2 Nucleus pulposus of intervertebral disc
3 Anulus fibrosus of intervertebral disc
4 Pubic symphysis
5 Manubriosternal synchondrosis
6 Spheno-occipital synchondrosis
7 Epiphysial cartilage or primary cartilaginous joint
8 Sternocostal (synchondrosis)
9 Sternocostal (typically synovial but can be symphysial)
10 Interchondral (synovial)
11 Interchondral (synchondrosis)
12 Costochondral (synchondrosis)
13 Interspinous ligament (vertebral syndesmosis)
14 Nuchal ligament (vertebral syndesmosis)
15 Anterior longitudinal ligament (vertebral syndesmosis)
16 Posterior longitudinal ligament (vertebral syndesmosis)
17 Body of vertebra
18 Spinous process of vertebra
19 Lamina of vertebra
20 Psoas major muscle
21 Aorta
22 Inferior vena cava
ments with a solid mass of connective tissue, but the uniting tissue is some type of cartilage instead of collagenous connective tissue proper. The three types of cartilaginous joints are: 1) synchondroses, 2) symphyses, and 3) epiphysial cartilages
or primary cartilaginous joints. The photos on these facing pages depict the different categories of cartilaginous joints. A few
syndesmoses from the fi brous joint category are also evident.
Transverse section of lumbar intervertebral disc
Inferior view
1
2
3
4
6
13
14
16 15
18
18
19
17
20
21
22
5
1
1
7
8
10
10
11
12
9
9
9
9
9
127
Radiograph of juvenile wrist region
Anterior view
Joints of the thoracic cage
Anterior view
Epiphysial cartilage Fetal skeleton 200x
Posterior view
1
1
7
8
10
10
11
12
9
9
9
9
9
7
1
2
5
128
Diarthroses or Synovial Joints Diarthroses differ from synarthroses
in one major way: instead of connecting neighboring bones by a solid mass
of connectve tissue, the bony connection consists of a double-layered connective tissue capsule that surrounds a lubricated
cavity between the bones. Within the capsule the ends of neighboring bony surfaces are covered by a smooth layer of hyaline cartilage. As a result of this design there is typically a much greater range of motion present in synovial joints, and they
form the joints of the skeleton that are responsible for the major movements of the body. The outer layer of the capsule, the
fi brous membrane, is continuous with the periosteum on the adjoining bones, while the inner layer of the capsule, the synovial membrane, attaches from the border of the articular cartilage on one bone to the border of the articular cartilage on the
other bone. Additionally, the synovial membrane secretes synovial fl uid, a lubricant that reduces friction between the mobile
cartilage-covered articular surfaces of the bones. The section through a fi nger joint below and the dissections of the knee
joint on the opposite page illustrate the basic features of a synovial joint. The pages that follow depict the major synovial
joints of the skeleton. One other key feature among synovial joints that is responsible for their varied range of motion is the
shape of the adjoining bone surfaces. It is this feature that anatomists use to describe the different types of synovial joints.
1 Middle phalanx of index finger
2 Proximal phalanx of index finger
3 Fibrous membrane of joint capsule
4 Synovial membrane of joint capsule
5 Articular cartilage
6 Joint cavity
7 Collateral ligament
8 Quadriceps tendon
9 Patellar ligament
10 Suprapatellar bursa
11 Synovial fold
12 Meniscus
13 Periosteum
14 Junction of periosteum (removed) with fibrous membrane
15 Junction of synovial membrane (removed) with articular cartilage
16 Femur with periosteum removed
17 Tibia with periosteum removed
18 Fibula with periosteum removed
19 Patella within quadriceps tendon
Proximal interphalangeal joint showing design of synovial joint
Frontal section, anterior view
3
7
4
6
3
7
7
4
5
5
5
8
9
10
11
12
13
14
14
15
15
16
17
18
19
129
Dissection of knee showing design of synovial joint
Medial view
Dissection of knee showing design of synovial joint
Lateral view
4
No comments:
Post a Comment
اكتب تعليق حول الموضوع