There are two truesacral vertebrae, but as development proceeds a number of other vertebrae become fused with the true sacrals, the whole forming a large compound sacrum.
But of these only two or three answer to the definition of true sacral vertebrae in being united to the ilia by small ribs.
The cervical part of the vertebral column is very long and flexible, while the post-cervical portion is generally very rigid, owing to the fusion of many of the vertebrae, especially in the lumbar and sacral regions.
The pelvic girdle differs from the pectoral in the fact that the dorsal bones--the ilia--are nearly always firmly united to transverse processes of the sacral vertebrae, by means of rudimentary ribs.
The sacral vertebra or =sacrum= differs from the vertebrae immediately in front of it only in the fact that its transverse processes are stouter and more obviously divided into dorsal and ventral portions.
The neck is long, the caudal vertebrae are amphicoelous, and from three to five vertebrae are fused together in the sacral region.
The urostyle is post-sacral and corresponds to three or more modified vertebrae.
In Notoryctes there is extensive fusion in the sacral region, six vertebrae, owing mainly to the great development of their metapophyses, being united with one another, and with the ilia, and the greater part of the ischia.
The first vertebra differs a good deal from any of the others; the seventeenth or sacral vertebra and the eighteenth or first caudal also present peculiarities of their own.
The sacral vertebrae of living forms are not ankylosed together, and the caudal vertebrae usually have well-developed chevron bones.
And why, if typical uniformity was to be maintained, does the number of sacral vertebræ vary within the same order of birds?
Mr. Spencer says: "In man there are five of these confluent sacral vertebræ; and in the ostrich tribe they number from seventeen to twenty.
The twelfth thoracic spinous process and the space below it are opposite the sacral segments (Chipault).
Sometimes there are no nervous disturbances, and this is especially the case when the defect is in the lower lumbar and sacral regions below the termination of the cord.
In the case of the lower extremities, three or more of the lumbar and one or more of the sacral nerve roots are resected within the vertebral canal.
Sensibility returns in the order--touch, pain, temperature, and the parts supplied by the lowest sacral segments usually become sentient first.
It is most frequent in the lumbar and sacral regions (Fig.
Pott's disease in the lumbo-sacral region usually affects adults, and, on account of the breadth of the vertebral bodies and the limited range of movement in this segment of the spine, is seldom accompanied by marked symptoms or deformity.
In rare cases these injuries are accompanied by damage to the intestine, the rectum, the sacral nerves, or the iliac blood vessels.
The thigh is rotated in both directions, and on comparing the two sides it will be found that rotation is restricted or abolished on the side affected, any apparent rotation taking place at the lumbo-sacral junction.
A mass of fat may project towards the surface, and when situated in the lumbo-sacral region may suggest a caudal appendage or tail (Fig.
In other cases the pain appears to be neuralgic in character, and is referable to the fifth sacral and the coccygeal nerves, or to the terminal branches of the sacral plexus distributed in this region.
On walking, the affected limb is dragged in such a way as to avoid movement at the hip, and to substitute for it movement at the lumbo-sacral junction.
With the assumption of the erect posture the normal S-shaped curve is developed, the cervical and lumbar segments arching forward, while the thoracic and sacral segments arch backward.
In injuries involving the lumbo-sacral region it is sometimes advisable to perform laminectomy for the purpose of suturing divided nerve cords.
Injuries of the lower thoracic and upper lumbar vertebræ, therefore, may produce complete paralysis within the area of distribution of the lumbar and sacral plexuses.
The last lumbar and the four upper sacral unite to form the sacral plexus.
The spots described by him were of a blue or purple color, were located upon the back (especially in the sacral region), and were variable in form and size.
We may say, then, that in Palenque every Maya baby below ten months of age was sacral spotted, and that no Mestizo baby was.
Baelz and some other writers have, therefore, gone so far as to consider the purple sacralspot a mark peculiar to that race, and to believe its occurrence proof of Mongolian origin.
I do not believe that the sacral spot exists among Aztecs.
Sacral spots have also been reported among Samoans and Hawaiians.
The injections of spermine, given for a period of fifteen months, restored the old lady to such an extent that she recovered her power of hearing and felt the sacral pains only slightly and after a long walk.
This patient had complained for several years of sacral pains, and moreover was nearly quite deaf and suffered from periodic attacks of malarial fever.
The middle sacral artery has already been referred to.
One of the most constant symptoms is pain in the back, and this is severe in proportion to the swelling and sensitiveness of the organ, when it presses on the sacral nerves and rectum.
This is, however, not the case; when sudden painful symptoms arise, they are invariably referred to the sacral region.
The family characters are mainly derived from the dilatation or non-dilatation of the sacral diapophyses, and the presence of teeth in one or both jaws, or their absence.
In the Ecaudata, the form of the transverse processes of the sacral vertebra varies very considerably, and has afforded important characters to the systematist.
Posterior (A) and ventral (B) views of the sacral vertebrae (S.
In man the lumbar vertebrae have sometimes assumed the character of the sacral vertebrae, the sacral vertebrae presenting the aspect of lumbar vertebrae, etc.
We sometimes observe a condition of anterior curvature of the lumbar and sacral regions, which might be taken for a congenital lordosis, but this is really a deformity produced after birth by the physiologic weight of the body.
Weil reported the case of a man of twenty-two years who was born with what was supposed to be a spina bifida in the lower sacral region.
From the body of an otherwise perfectly formed child was a supernumerary head protruding from a broad base attached to the lower lumbar and sacral region.
The sacral promontory was exaggerated, and the anteroposterior pelvic diameter of the inlet in consequence diminished.
The twins were united below the third sacralvertebrae in such a manner that they could lie alongside of each other.
Anorectal atresia is the ordinary imperforation of the anus, in which the rectum terminates in the middle of the sacral cavity.
In evidence of the probability of the truth of this position, we will draw your attention, first to its central location between the sacraland cerebral nerve centers.
It is dead until sensation reaches the vein from the sacral and pudic plexus.
The womb sacral (utero-sacral) which holds the womb well up in the hollow of the sacrum and the round ligaments which keep the womb well forward enter most actively into the support of the womb.
As previously stated, it is scarcely possible to count the lumbo-sacral vertebræ; but they certainly do not correspond in shape or number in the several skeletons.
The rock-pigeon has twelve sacral vertebræ; but these vary in number, relative size, and distinctness in the different breeds.
In tumblers there are either eleven, twelve, or thirteen sacral vertebræ.
The more recent ancestors of this series were tailless anthropoids (similar to the Anthropopithecus), with five sacral vertebrae.
The more remote ancestors were tailed Cercopitheci, with three or four sacral vertebrae.
Defn: The cartilaginous cap at the sacral end of the ilium of some animals.
Defn: Of or pertaining to both the caudal and sacral parts of the vertebral column; as, the urosacral vertebræ of birds.
A general treatise on the subject of lameness does not properly include such structures any more than it does the various affections of the dorsal, lumbar and sacral vertebrae or inflammation of the abdominal parietes.
The lumbosacral plexus results substantially from the union of the ventral branches of the last three lumbar and the first two sacral nerves, but it derives a small root from the third lumbar nerve also.
Rheumatism or metastatic infection may be the cause of hip lameness as well as affections of the pelvic bones, lumbar and sacral vertebrae.
Similarly the five vertebrae which follow the truesacral vertebrae are originally part of the tail, and have been blended with the other vertebrae in front, in consequence of the extension along them of the bird's hip bones.
The great difference between the sacrum of a Pterodactyle and that of a bird has been rendered intelligible by the excellent discussion of the sacral region in birds made by Professor Huxley.
The hip bones are closely united with the sacrum by bony union, and rarely appear to come away from the sacral vertebrae, as among mammals and reptiles, though this happens with the Lias Pterodactyles.
There are other groups of fossil reptiles in which the number of sacral vertebrae is in some cases less and in other cases more.
Almost any placental mammal in which the vertebrae of the sacral region are anchylosed together has a similar sacrum, which differs from that of birds in the more complete individuality of the constituent bones remaining evident.
In birds the sacral vertebrae number from five to twenty-two.
There is, perhaps, no group in which the sacrum makes a nearer approach to that of birds than is found among these Pterodactyles, although there are more sacral vertebrae in some Dinosaurs.
The sacral vertebrae are generally three in number, and the lumbar and dorsal together vary from nineteen to twenty-three.
The dorsal and lumbar vertebrae are, of course, to be distinguished by the presence of ribs attached to the former; but as there is only a rudimentary pelvis, not attached to the vertebral column, no sacral region can be detected.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "sacral" in a variety of sentences. We hope that you will now be able to make sentences using this word.
