THE ARTICULATIONS. Into what Classes are the Articulations divided? Into 3,-1. Synarthro'sis, immovable; 2. Amphiarthro'sis, Synchondrosis, or Symphysis, having limited motion; 3. Diarthro'sis, having free motion. How are the Synarthroses subdivided? Into 3 divisions,-Sutura, by indentations; Schindy'lesis, by a plate of bone into a cleft in another; and Gompho'sis, by a conical process into a socket. The Sutura are again subdivided into-S. Dentata, having tooth-like processes; S. Serrata, with serrated edges; S. Limbosa, having beveled margins and dentated processes; S. Squamosa, with thin beveled margins overlapping each other; S. Harmonia, contiguous rough surfaces opposed to each other. The first 3 are also named Sutura Vera (true sutures) having indented borders; the last 2 Sutura Notha (false sutures) being formed by rough surfaces. How are the Diarthroses divided? Into 4 divisions,-Arthrodia, gliding joint; Enarthrosis, ball-and-socket joint; Ginglymus, hinge-joint; and Diarthrosis Rotatorius, a ring surrounding a pivot. Give an Example of each of the above-named articulations. Sutura Dentata,—the inter-parietal suture. Sutura Harmonia,—the intermaxillary symphysis. Schindy' lesis,-rostrum of sphenoid with the vomer. Amphiarthro'sis,—the bodies of the vertebræ, the sacro-iliac, and pubic symphyses. Diarthro'ses,— Arthrodia,-sterno-clavicular articulation. Enarthrosis,-hip-joint, shoulder-joint. Ginglymus, elbow-joint, ankle-joint, knee-joint. Diarthrosis Rotatorius,—the superior radio-ulnar, and atlo-axoid articulations. Name the Varieties of motion in joints? There are 7 varieties, viz.— flexion, extension, adduction, abduction, rotation, circumduction, and gliding movement. What Structures enter into the formation of joints? There are 5, viz.— the articular lamella of bone, ligaments, cartilage, fibro-cartilage, and synovial membrane. Articular Lamella of bone differs from ordinary bone tissue in being more dense, containing no Haversian canals nor canaliculi, and having larger lacunæ. Ligaments are bands of white fibrous tissue, except the ligamentum subflava and the ligamentum nuchæ, which are both composed purely of yellow elastic tissue. Cartilage is temporary or permanent. The first forms the original framework of the skeleton, and becomes ossified. Permanent cartilage is not prone to ossification, and is divided into 3 varieties,-Articular, covering the ends of bones in joints; Costal, forming part of the skeleton; Reticular, arranged in lamellæ or plates to maintain the shape of certain parts. Fibro-cartilage is Interarticular (menisci), separating the bones of a joint; Connecting, binding bones together; Circumferential, deepening cavities; Stratiform, lining grooves. Synovial Membranes secrete the synovia, a viscid, glairy fluid, and resemble the serous membranes in structure. They are Articular, lubricating joints; Bursal, forming closed sacs (bursæ); Vaginal, ensheathing tendons. Describe the Vertebral Articulations. They are formed by the adjacent surfaces of the bodies of the vertebræ, and their articular processes, and are connected by the following ligaments, etc.-(See FIG. 31.) Intervertebral Fibro-cartilages, between the bodies of all true vertebræ, except the axis and atlas. Anterior Common Ligament,1 along fronts of the bodies. Posterior Common Ligament, along backs of the bodies. Ligamenta Subflava, connect the laminæ of adjacent vertebræ. Capsular, surround the articular processes, and are lined by synovial membrane. Supra-spinous and Inter-spinous, connect the spinous processes. Inter-transverse,3 connect the transverse processes. Describe the Occipito-atloid Articulation. It is a double arthrodia formed 2 Lateral, from the jugular processes of the occipital bone to the bases of the transverse processes of the atlas. 2 Capsular,d around the articular surfaces, lined by synovial membrane. Describe the Occipito-axoid Articulation. Formed by the occipital bone and the odontoid process of the axis, which do not articulate with each other strictly, but are connected by 4 ligaments. Occipito-axoid1 (Apparatus Ligamentosus Colli), a continuation of the posterior common spinal ligament to the basilar process of the occipital bone. 2 Lateral Occipito-odontoid (Check Ligaments), from the head of the odontoid process to the sides of the occipital condyles. Vertical Occipito-odontoid (Ligamentum Suspensorium), from the anterior margin of the foramen magnum to the odontoid apex. Describe the Atlo-axoid Articulation. It is a double arthrodia between the articular processes, a double diarthrosis rotatorius between the atlas and the odontoid process, and has 6 ligaments, and 4 synovial membranes. 2 Anterior and 1 Posterior Atlo-axoid, continuations of the anterior and posterior common spinal ligaments. 2 Capsular, surrounding the articular surfaces, each lined by a synovial membrane. Transverse, or Cruciform Ligament, divides the spinal foramen of the atlas into two portions, stretching across between the tubercles on the inner sides of the articular processes. It holds the odontoid process in place, having a synovial membrane interposed. Another synovial membrane is situated between the process and the anterior arch. The transverse ligament sends two vertical slips, one upwards, the other downwards, from which it is named the Cruciform Ligament. Describe the Temporo-maxillary Articulation. A double arthrodia between the condyle of the lower jaw and the anterior part of the glenoid cavity of the temporal bone. It has 2 synovial membranes with an inter-articular fibrocartilage between them, and 4 ligaments, viz.— External Lateral, from the tubercle of the zygoma to the outer side of the neck of the condyle of the lower jaw. Internal Lateral,d from the spine of the sphenoid to the margin men. Stylo-maxillary,ƒ from the styloid process of the temporal bone to the angle of the inferior maxillary. FIG. 30. a Capsular,c from the edge of the glenoid cavity and the eminentia articularis to the neck of the inferior maxillary condyle. Nerves are derived from the auriculo-temporal and masseteric branches of the inferior maxillary. Describe the Costo-vertebral Articulations. They are each a double arthrodia between the head of the rib and the bodies of 2 adjacent vertebræ, except in the Ist, 10th, 11th, and 12th ribs, which are each a single arthrodia, as they articulate with but I vertebra each. Their ligaments are 3, viz.Anterior Costo-vertebral, or Stellate Ligament, consists of 3 bundles, which fasten the anterior part of the head of the rib to the intervertebral disk and the 2 adjacent bodies. FIG. 31. Inter-articular Costo-vertebral, in the interior of the joint, from the crest on the head of the rib to the intervertebral disk; on each side there is a separate synovial membrane. Capsular, surrounding the articular surfaces. Describe the Costo-transverse Articulations. They are 10 arthrodial articulations between the tubercles of the first 10 ribs and the transverse processes of the vertebræ next below. Their ligaments are 3, viz.-Anterior, Middle, and Posterior Costo-transverse. Describe the Costo-sternal Articulations. One a synarthrodial, 6 are arthrodial articulations, between the costal cartilages and the margin of the sternum. The first has no synovial membrane, the second only has an interarticular fibro-cartilage. Each has 3 ligaments, the Anterior and Posterior Costo-sternal, and a Capsular. The Costo-xiphoid Ligament connects the xiphoid appendix to the cartilage of the 6th or 7th rib. How are the Costal Cartilages connected with the ribs and with each other? With the ribs by a depression on the end of each rib, strengthened by the blending together of the periosteum and the perichondrium. The cartilages of the lower ribs, sometimes from the 5th to the 10th inclusive, articulate with each other by their borders and for each a capsular and an intercostal ligament, with 3 synovial membranes for the 3 articulations between the 6th and the 9th cartilages. What are the Ligaments of the Sternum? An anterior sternal and a posterior sternal ligament, with a layer of cartilage between the manubrium and the gladiolus. Describe the Sacro-vertebral Articulation. It is similar to the other vertebral articulations, but has 2 additional ligaments on each side, viz. Lumbo-sacral, from the transverse processes of the 5th lumbar vertebra to the base of the sacrum laterally and anteriorly. Lumbo-iliac, from the apices of the transverse processes of the 5th lumbar vertebra to the crest of the ilium. Describe the Sacro-coccygeal Articulation. It is an amphiarthrodial joint, and has 3 ligaments, viz.— Anterior Sacro-coccygeal. Posterior Sacro-coccygeal. Interarticular Fibro-cartilage, in the joint. Describe the Sacro-iliac Articulation. It is an amphiarthrodial joint, formed by the auricular surfaces of the sacrum and ilium. Its ligaments on each side are as follows, viz. Anterior Sacro-iliac. Oblique Sacro-iliac. Posterior Sacro-iliac.8 Describe the Sacro-ischiatic Articulation. Its ligaments convert the sacro-sciatic notches into foramina, the greater notch by the lesser ligament, the lesser notch by the greater ligament. These foramina are described under the ilium and ischium bones. Great Sacro-sciatic Ligament, 13 14 from the posterior inferior spine of the ilium and the posterior surfaces and margins of the sacrum and coccyx, to the inner margin of the tuberosity and the ascend ing ramus of the ischium. FIG. 32. Lesser Sacro-sciatic Ligament,15 16 from the margins of the sacrum and coccyx, into the spine of the ischium. Describe the Pubic Articulation. It is an amphiarthrodial joint, formed by the 2 pubic bones. It has an interarticular fibro-cartilage and 4 ligaments, viz.— Posterior Pubic. Supra-pubic. Anterior Pubic. |