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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
costochondral angle is opened out. By these latter movements a considerable increase in the transverse diameter of the thorax is effected.
  Vertebrochondral Ribs (Fig. 318).—The seventh rib is included with this group, as it conforms more closely to their type. While the movements of these ribs assist in enlarging the thorax for respiratory purposes, they are also concerned in increasing the upper abdominal space for viscera displaced by the action of the diaphragm. The costal cartilages articulate with one another, so that each pushes up that above it, the final thrust being directed to pushing forward and upward the lower end of the body of the sternum. The amount of elevation of the anterior extremities is limited on account of the very slight rotation of the rib neck. Elevation of the shaft is accompanied by an outward and backward movement; the outward movement everts the anterior end of the rib and opens up the subcostal angle, while the backward movement pulls back the anterior extremity and counteracts the forward thrust due to its elevation; this latter is most noticeable in the lower ribs, which are the shortest. The total result is a considerable increase in the transverse and a diminution in the median antero-posterior diameter of the upper part of the abdomen; at the same time, however, the lateral antero-posterior diameters of the abdomen are increased.
  Vertebral Ribs.—Since these ribs have free anterior extremities and only costocentral articulations with no interarticular ligaments, they are capable of slight movements in all directions. When the other ribs are elevated these are depressed and fixed to form points of action for the diaphragm.
 
5h. Articulation of the Vertebral Column with the Pelvis The Iliolumbar Ligament
 
  The ligaments connecting the fifth lumbar vertebra with the sacrum are similar to those which join the movable segments of the vertebral column with each other—viz.: 1. The continuation downward of the anterior and posterior longitudinal ligaments. 2. The intervertebral fibrocartilage, connecting the body of the fifth lumbar to that of the first sacral vertebra and forming an amphiarthrodial joint. 3. Ligamenta flava, uniting the laminæ of the fifth lumbar vertebra with those of the first sacral. 4. Capsules connecting the articular processes and forming a double arthrodia. 5. Inter- and supraspinal ligaments.
  On either side an additional ligament, the iliolumbar, connects the pelvis with the vertebral column.

The Iliolumbar Ligament (ligamentum iliolumbale) (Fig. 319).—The iliolumbar ligament is attached above to the lower and front part of the transverse process of the fifth lumbar vertebra. It radiates as it passes lateralward and is attached by two main bands to the pelvis. The lower bands run to the base of the sacrum, blending with the anterior sacroiliac ligament; the upper is attached to the crest of the ilium immediately in front of the sacroiliac articulation, and is continuous above with the lumbodorsal fascia. In front, it is in relation with the Psoas major; behind, with the muscles occupying the vertebral groove; above, with the Quadratus lumborum.
 
5i. Articulations of the Pelvis
 
  The ligaments connecting the bones of the pelvis with each other may be divided into four groups: 1. Those connecting the sacrum and ilium. 2. Those passing between the sacrum and ischium. 3. Those uniting the sacrum and coccyx. 4. Those between the two public bones.
  1. Sacroiliac Articulation (articulatio sacroiliaca).—The sacroiliac articulation is an amphiarthrodial joint, formed between the auricular surfaces of the sacrum and the ilium. The articular surface of each bone is covered with a thin plate of cartilage, thicker on the sacrum than on the ilium. These cartilaginous plates are in close contact with each other, and to a certain extent are united together by irregular patches of softer fibrocartilage, and at their upper and posterior part by fine interosseous fibers. In a considerable part of their extent, especially in advanced life, they are separated by a space containing a synovia-like fluid, and hence the joint presents the characteristics of a diarthrosis. The ligaments of the joint are:
The Anterior Sacroiliac.
The Posterior Sacroiliac.
The Interosseous.

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