Variations in thickness of articular cartilage in the human sacroiliac joint.

Differences in articular cartilage thickness in the sacroiliac joint were investigated in different regions of the sacral and the iliac articular surfaces in the embalmed cadavers of five males and six females. The mean thickness of the sacral articular cartilage was greater than that of the iliac articular cartilage (P < 0.001) and the sacral articular cartilage of the female was thicker than that of the male (P < 0.02). Differences between thicknesses of the iliac articular cartilage in the male and female and in different regions of the sacral and iliac articular cartilages were found to be not significant.

Manual of embryology

This manual is a summary of important aspect of human embryology, and is intended to accompany the lecture course on the subject. It is not meant to substitute for a textbook, many excellent texts being available, but to act as a guide to the student being introduced to the subject. It is hoped that it will encourage further reading in a particularly fascinating and important developing area of biomedical science. (AU)

Manual of embryology

This manual is a summary of important aspect of human embryology, and is intended to accompany the lecture course on the subject. It is not meant to substitute for a textbook, many excellent texts being available, but to act as a guide to the student being introduced to the subject. It is hoped that it will encourage further reading in a particularly fascinating and important developing area of biomedical science(AU)

Manual of embryology

This manual is a summary of important aspect of human embryology, and is intended to accompany the lecture course on the subject. It is not meant to substitute for a textbook, many excellent texts being available, but to act as a guide to the student being introduced to the subject. It is hoped that it will encourage further reading in a particularly fascinating and important developing area of biomedical science.

The effects of paralysis on skeletal development in the chick embryo. I. General effects.

In order to investigate further the effects of paralysis on skeletal development in the chick embryo, paralysis was induced at 6 days of incubation by dropping 0.2% solution of decamethonium bromide onto the chorioallantoic membrane and maintaining paralysis through to 20 days of incubation. General effects of paralysis included lower body weight, marked subcutaneous oedema, twisting of the neck to the right with marked rigidity, and protrusion of the lower beak beyond the upper. Skeletal abnormalities included cartilaginous and later bony fusion between cervical vertebrae and distortion of scapula and pubis. Long bones were normal in their general form but showed marked reductions in full length and in length of the calcified diaphysis. The patella occasionally underwent chondrification, unlike the tibial cartilage at the tarsus. Reduction in length of the bones of both jaws occurred but was substantially greater in the upper, resulting in the protrusion of the lower. Ossification times of most skeletal elements were little affected by paralysis but some centres appearing nearer the end of incubation showed slight delay in their times of appearance.

The effects of paralysis on skeletal development in the chick embryo. II. Effects on histogenesis of the tibia.

In order to study the effects of paralysis on the development of bone, chick embryos were paralysed at 6 days of incubation and the pattern of histogenesis of the tibia was compared with that of control embryos by histology, scanning electron microscopy and morphometry. Up to 11 days of incubation the histological features of chondrification, initial perichondrial ossification and invasion by the vascular bud showed no differences. After this time the paralysed embryos exhibited a reduction in the formation of bone tissue and a reduced development of the fibular crest. The spread of cartilage resorption was also markedly reduced. In addition, scanning electron microscopy suggested a reduction in resorption of the innermost layers of bone. Blood vessels in the marrow cavity appeared smaller and those within developing osteones appeared larger than in the controls. In the paralysed embryos, morphometry confirmed a significant reduction in total volume of the tibia together with changes in its volumetric composition resulting from reduction in bone formation, cartilage formation and cartilage resorption.

The development of pneumatisation in the skull of the domestic fowl (Gallus gallus domesticus).

The development of pneumatisation in the skull of the domestic fowl has been studied in a series of chick embryos from 7-20 days incubation (Hamburger & Hamilton Stages 29-46) and in birds from hatching to 126 days posthatching. During the embryonic period primary pneumatisation developed by 3 routes. (i) The tympanic cavity directly invaded surrounding bones-squamosal, parietal, supraoccipital and prootic. (ii) Extensions of the tympanic cavity invaded the bones in which these occurred-the caudal pneumatic antrum in the exoccipital and the rostral pneumatic antrum in the parasphenoid/basisphenoid. (iii) A tubular diverticulum from the tympanic cavity grew rostrally and invaded the quadrate and pterygoid. A similar diverticulum grew rostrally towards the cartilaginous mandible but was only found to invade it in one case after the time of hatching. In most instances onset of pneumatisation occurred three stages subsequent to the onset of ossification. In bones in which ossification is intramembranous bone tissue often formed around small air sac outgrowths, resulting in multiple sites of invasion while, in bones ossifying perichondrally, cartilage resorption was a necessary prerequisite and air sac invasion frequently occurred in common with a vascular bud resulting in a single pneumatic foramen. After hatching secondary pneumatisation spread from the already pneumatised bones to involve the whole cranium. Spread throughout the parietal and frontal was preceded by the establishment of dipole within these bones and the final extent of pneumatisation was variable. Spread to the most distal parts of the cranium was only accomplished after the intervening sychondroses had fused.

The development of pneumatisation in the postcranial skeleton of the domestic fowl.

The development of pneumatisation in the postcranial skeleton has been investigated in a flock of Golden Comet pullets from hatching to 182 days posthatching. The timing of development of pneumatisation in the vertebral column, vertebral ribs, sternum and humerus has been demonstrated. No pneumatisation was encountered in the sternal ribs, os coxae or coracoid. Development of pneumatisation in the coracoid and humerus was also studied in a flock of White Leghorn pullets and cockerels from hatching to 126 days posthatching. In this group, regular pneumatisation of the humerus occurred after the time of onset and the coracoid was frequently pneumatised unlike the Golden Comets. The rate of development of pneumatisation in the humerus was more rapid in White Leghorn pullets than in cockerels and also more rapid than in Golden Comet pullets.

The distribution of pneumatisation in the skeleton of the adult domestic fowl.

The occurrence of pneumatisation in the skull of the adult domestic fowl was investigated in eight birds by gross and histological examination. It was found to occur regularly throughout the neurocranium and in the quadrate and variably in the mandible, but to be absent in the facial skeleton. Close agreement was found between gross and histological examination. The entire skeletons of fifty one adult birds all from the same hatch and kept under the same conditions were examined grossly for evidence of the occurrence and extent of pneumatisation. Previous findings for the skull were confirmed with the additional information that pneumatisation in the pterygoid was variable. Variation in the extent of skull pneumatisation was less than in the postcranial skeleton, where only cervical vertebrae 5-9 were found to be regularly pneumatised. The humerus and coracoid were variably pneumatised, often unilaterally. The os coxae and sternum had a very low incidence of pneumatisation. The three cockerels in the group appeared to be relatively well pneumatised. Some possible factors governing the occurrence and extent of pneumatisation in the skeleton are discussed.

Fusions within the mandible of the domestic fowl (Gallus gallus domesticus).

The articulations formed within the mandible of the domestic fowl by its constituent elements have been described and illustrated. The sutures identified were suturae angulosplenialis, angulosupra-angularis, articulare/pre-articulo-angularis, articulare/pre-articulosupra-angularis, dento-angularis, dentosplenialis, dentosupra-angularis and supra-angulosplenialis. Some degree of fusion was found to occur in all sutures except sutura supra-angulosplenialis. The range of fusion time and mean fusion time for each site was studied in a flock of Golden Comet pullets. Mean fusion times varied from 45-119 days post-hatching.

Ossification of the laryngeal, tracheal and syringeal cartilages in the domestic fowl.

The process of ossification in the cartilages of the larynx, trachea and syrinx of the domestic fowl has been studied in growing and in adult Golden Comet birds. In the laryngeal cartilages, mineralisation occurred consistently in the body and wings of the cricoid cartilage, in the procricoid cartilage and in the bodies of the arytenoid cartilages. In 7 out of 12 adult birds there were small additional centres in the tips of the rostral processes of the arytenoid cartilages and in one adult bird there were small centres in the caudal processes also. When present, these additional centres were always found bilaterally. Mineralisation in the laryngeal cartilages developed from 105 days post-hatching onwards and was first seen in the bodies of the arytenoid cartilages. Some evidence of a segmental pattern was noted, both in the earliest centres and in the final stage in the caudal region of the body of the tcricoid cartilage. Mineralisation in the trachea developed from 98 days post-hatching onwards. It was first found in the caudal region and spread craniad. The rings at the caudal end of the trachea and the cranial end of the tympanum (but not the last two rings of he tympanum) were always fully involved. Rings in the cranial part of the trachea remained more lightly mineralised. In the syrinx, mineralisation regularly occurred only in the pessulus and in the base of the first bronchial syringeal cartilages. In some birds, it was also encountered more caudally in the cartilages of the primary bronchi. Histological examination showed that, in the early stages, the alizarin staining was due to the presence of mineralised cartilage. At 182 days post-hatching and in the adults, actual bony tissue was observed. The possible significance of the occurrence of ossification in these cartilages of birds in briefly considered.

A radiographic study of mineralised tendons in the domestic fowl.

1. The occurrence of mineralised tendons in the wing and pelvic limb of the domestic fowl was studied radiographically in adults and in growing birds from hatching to 182 d. 2. Mineralised tendons were found to occur in all the adults in the dorsal and plantar tarsometatarsus and variably in the caudal tibiotarsus, cranial metacarpus and caudal antebrachium. In the cranial tibiotarsus a mineralised tendon was detected in two cockerels only. 3. Mineralisation was detected from 91 d onwards, at first in tendons in the plantar tarsometatarsus and cranial metacarpus and later in the dorsal tarsometatarsus. The mineralised tendons found in adults at other sites were not found during the growing period studied.

A re-investigation of the centres of ossification in the avian skeleton at and after hatching.

The centres of ossification occurring in the skeleton of the domestic fowl from hatching onwards have been re-investigated in groups of birds from the same hatches, reared under standardised conditions and sampled at intervals from hatching to 182 days. Selected areas have been surveyed in adult birds. The numerous centres which are already present at hatching have been identified. Those first appearing around the time of hatching were for the uncinate processes and the phalanx of digit IV. The centres appearing after hatching were those for metacarpal II, four carpal centres, the orbitosphenoid, rostal and caudal basibranchials, epibranchials, entoglossal, proximal tibial centre, patella and tarsal sesamoid. These have been illustrated and the mean time of appearance and range of time of appearance of each calculated. Some evidence of slight variation in sequence of appearance was detected. The proximal tibial centre was concluded to be the only true secondary centre in the long bones and to correspond to the traction epiphysis of this region in the mammal. In adults, the phalangeal formula of the manus was found usually to be 2:2:1, but occasionally it was reduced to 1:2:1. The only sesamoidean centre found, other than the patella and the tarsal sesamoid, was in the carpal region and was termed the dorsal carpal sesamoid. Some of the many controversies existing in the previous literature have been assessed in the light of the findings of this study.

The articulations of the neurocranium in the postnatal skeleton of the domestic fowl (Gallus gallus domesticus).

In the neurocranium of the domestic fowl the centres of ossification present at hatching and appearing susbequently have been investigated and illustrated. The controversy over centres around the orbit is reviewed and it is concluded that paired laterally placed pleurosphenoids are present by the time of hatching, while paired orbitosphenoids situated near the midline and dorsal to the optic foramen do not appear until between 70 and 91 days after hatching. No additional "presphenoid" centres were detected. The neurocranial articulations were studied: 27, many of them paired, were identified. The sequence and timing of synostosis were determined.