Body cavi ties and their serous lining 303

Cranial mediastinum

Chest wall Myocardium of the left ventricle

Lung Diaphragm

Hepatic vein Portal vein branch

Stomach

Fig. 6-12. Magnetic resonance imaging of the thorax including the intrathoracic segment of the abdominal cavity of a dog (coronal view); courtesy of Dr. Isa Foltin, Regensburg.

Back musculature Spinous process

Vertebral column Caudal vena cava

Trachea Portal vein branch Cranial mediastinum Liver Left ventricle Lung Right ventricle Sternum

Fig. 6-13. Magnetic resonance imaging of the thorax including the cranial abdominal cavity of a dog (sagittal view); courtesy of Dr. Isa Foltin, Regensburg. terica cranialis). The organs at the ends of the gastrointestinal Pelvic cavity (cavum pelvis) tract attain their final positions in the abdominal cavity (Fig. 6-9) and the cranial mesenteric artery becomes the cranial The pelvic cavity is bordered by the sacrum, a species-depen- root of the mesentery (radix mesenterii). (For a detailed de- dent number of caudal vertebrae, and the two pelvic bones, scription of this process, see an Embryology textbook.) which meet ventrally in the pelvic symphysis. These struc- In large herbivores, voluminous and especially heavy sec- tures form a bony ring, which is in turn surrounded by the tions of the digestive system (e.g. a equine's large intestine) muscles of the hip and rump. The muscles of the pelvic girdle are supported by shortened mesenteries that are partly fused extend from dorsal and lateral into the pelvic cavity. to the dorsal abdominal wall through dense connective tissue. The pelvic inlet (apertura pelvis cranialis) is bordered by This reduces the considerable weight of the filled intestinal the terminal line (linea terminalis) in all domestic animal convolutes that would otherwise rest upon the ventral abdomi- species. The pelvic cavity ends ventrally in all domestic nal wall. The weight of the dorsal rumen sack and of the rumi- species at the ischiatic arch (arcus ischiadicus), but ends nant spleen is also reduced through connective tissue fusions dorsally after a species-dependent number of caudal verte- with the dorsal abdominal wall. brae. The pelvic diaphragm (diaphragma pelvis) closes the pelvic outlet (apertura pelvis caudalis). In carnivores, pigs 304 6 Viscera

Spinal cord

Vertebral column with intervertebral discs Lumbar vertebra

Liver Rectum Transverse colon

Urinary bladder Stomach

Jejunum Descending colon

Fig. 6-14. Sagittal section through the abdominal and pelvic cavities of a dog (E 12 plastination); courtesy of Prof. Dr. M.-C. Sora, Vienna.

Spinal cord Lumbar vertebrae Vertebral column with intervertebral discs

Lung Transverse colon Urinary bladder Jejunum Stomach Penis Liver

Fig. 6-15. Magnetic resonance imaging of a sagittal section through the abdominal and pelvic cavities of a dog; courtesy of Dr. Isa Foltin, Regensburg.

Vertebral canal Thoracic vertebra Lung Diaphragm Rib Stomach Colon Urinary bladder Liver Jejunum

Fig. 6-16. Image of the abdominal and pelvic cavities of a cat (radiograph, laterolateral view); courtesy of Prof. Dr. Ulrike Matis, Munich. Body cav ities and their serous lining 305

Right kidney Coeli ac artery Crani al mesen teric and Crani al mesen ter ic ar tery coe liac gan glions

Right renal ar tery Left kid ney

Cau dal vena cava

Ova ry in the ovari an bursa

Right ureter In ter mesen teric plexus Caudal mesen ter ic gan gli on Left ure ter Deep circum flex artery of the ili um Uterus horn

Caudal mesen ter ic artery Right hypo gastric nerve Medi an sa cral ar tery Left inter nal ili ac artery Right exter nal ili ac ar tery Muscu lar lacu na

Uri nary bladder Fem oral artery in the femo ral space

Femo ral vein Pu bic pecten

Fig. 6-17. Retroperitoneal muscles, organs, vessels and nerve tracts on the dorsal wall of the abdominal and pelvic cavities of a female dog (ventral aspect); courtesy of Dr. R. Macher, Vienna.

and small ruminants, the girth of the pelvic outlet can be in- to be located in the retroperitoneal part of the pelvic cavity. creased through the motility of the caudal vertebrae, which is This section ends caudally at the pelvic diaphragm, which is important for female animals during parturition. The rectum comprised of muscles and fasciae and closes the pelvic outlet. and anus (Fig. 6-4 and 14ff.), along with the urinary bladder The pelvic diaphragm is built through the: and parts of the urogenital tract located caudal of the bladder, are all located in the pelvic cavity. In females, the urethra, ● paired coccygeal muscles and the paired levator ani the uterine body, the cervix, the vagina and its vestibule are muscles (mm. coccygei et levatores ani), all located here, whereas in the male animal the pelvic section ● external and internal fasciae (fascia externa et interna) of the urethra, the ductus deferens and the accessory sex of the pelvic diaphragm, glands are found in the pelvic cavity. ● external anal sphincter muscle (m. sphincter ani externus), The cranial section of the pelvic cavity is lined with peri- ● bulbospongious muscle (m. bulbospongiosus), toneum and is therefore referred to as the peritoneal segment ● ischiocavernous muscle (m. ischiocavernosus), and the of the pelvic cavity. Here, the peritoneum builds multiple cau- ● urethral sphincter muscle (m. sphincter urethrae). dal pouches, the pouches (excavationes) (Fig. 6-15 and 28). The urinary bladder has two lateral ligaments, the liga- menta vesicae lateralia, each of which contains the remnants of The anus and the end of the urogenital canal perforate the an umbilical artery (ligamentum teres vesicae). The bladder pelvic diaphragm and are bordered by the paired levator ani is attached to the ventral wall by the median vesical ligament. muscles. The mesenteries of the female genital tract suspending the two The region between the tail base and the scrotum in male ovaries and the uterus are parts of the genital plica, from animals and between the tail base and the vulva in female ani- which the broad uterine ligament (ligamentum latum uteri) mals is the perineal region (regio perinealis). Located here is develops. The organs caudal to the peritoneal pouches are said the perineum, which is a fibrillary-muscular section of skin be-