G. Dalin

Sacroiliac Joint of the Horse 1. Gross morphology

A total of 22 morphological features were described in the sacroiliac joints of 41 horses which had no history of any low back condition. Some dramatic differences in both sacral and iliac aspects of joint shape and articular surfaces were seen according to age. These findings were thought to be due to progressive cartilaginous degeneration. Only minor significant differences were seen between left and right sacroiliac joints or between breeds and sex. The iliac surface was more prone to degenerative change. Ankylosis of the joints was not recorded and the incidence of articular or para‐articular spur formation was low.

Sacroiliac Joint of the Horse 2. Morphometric features

The sacroiliac joints were collected from 41 horses from late fetal life to 14 years of age. The sacral and iliac articular surfaces were analysed by morphometry with regard to area, length, width and form factor. The body weights of the animals varied from 10 to 550 kg and the sacral articular surface area from 1.0 to 17.8 cm2. Highly significant correlations were found between articular surface dimensions and body weights. Accordingly, the relative size of the joints decreased with increasing body weight/age. The sacral and iliac measurements were essentially comparable. No consistent left‐right sidedness was found and no significant sex or breed differences were present.

Sacroiliac Joint of the Horse 3. Histological appearance

To establish a baseline for the histological appearance of the sacroiliac joint of the horse, joint specimens were collected from 41 horses from late fetal life to the age of 14 years. Sagittal sections from the joints were radiographed and sectioned for histological examination.

Development of the genital peritoneal folds in sheep.

Development of the genital peritoneum in the sheep was studied in embryos/fetuses that were 27‐69 days old. The plica mesonephrica was the first visible fold of the urogenital organs of the embryos and was the origin of the proximal mesorchium or mesovarium. The plica suspensoria gonadalis fixed the gonad to the mesonephros and held the cranial genital ligament and the cranial part of the gubernaculum. The distal mesorchium or mesovarium evolved from this fold. The inguinal fold fixed the caudal part of the gubernaculum. The suspensory fold of the gonad and plica inguinalis formed a system of serosal folds called the Plica gonadoinguinalis. The fold of the genital ducts had two parts, divided by the crossing with the gubernaculum. The mesepididymis or mesosalpinx evolved from the cranial part of the fold, while the caudal part was the origin of the mesoductus deferens or mesometrium. The caudal part of the right and left folds contributed to defining another system of peritoneal folds, the Plica genitalis. A rearrangement of some accepted terms in the nomenclature is proposed, as are some new terms. An analysis of the meaning of some terms, especially those applied to systems of peritoneal folds, is given to aid in their interpretation.