CompAnat: Chapter 2.5: Part 2

Sacrum

The sacral vertebrae and their ossified intervertebral discs are firmly fused to form a single bone

1.5 years

The fusion of the single elements is usually completed (carnivores and pigs)

3-4 years

The fusion of the single elements is usually completed (ruminants)

4-5 years

The fusion of the single elements is usually completed (horse)

first sacral vertebra

with its expanded wings forms a firm articulation with the pelvic girdle through which the thrust of the hindlimbs is transmitted to the trunk

quadrilateral

Shape of sacrum in carnivores

Triangular

Shape of sacrum in domestic mammals

dorsal surface

Gives attachment to the hip, rump and hamstring musculature and provides openings for the passage of the dorsal spinal nerves of the lumbosacral plexus

carnivores and the horse

the free ends of the spinous processes remain separate, while their bases are fused.

ruminants

dorsal spines are fused to form the median sacral crest (crista sacralis mediana).

pig

the spinous processes are replaced by an indistinct crest

intermediate sacral crest

found in ruminants and represents the fused rudiments of the articular processes.

caudal vertebrae

gradually reduce in size from first to last.

caudal vertebrae

also show a progressive simplification in their form by losing characteristic vertebral features, such as arches and processes

Cylindrical rods

The last caudal vertebrae resemble

Horse

spinous processes of the second caudal vertebra is bifurcated and the arch of the third caudal vertebra is already incomplete, thus the vertebral canal is open dorsally

Ribs and Sternum

The thoracic skeleton comprises the thoracic vertebrae

cranial aperture

The thorax encloses the thoracic cavity, which is accessible cranially through the

cranial aperture

thoracic inlet between the first ribs.

caudal aperture

framed on both sides by the costal arches

thoracic wall

composed of the costal arch, the intercostal spaces and the angle between the left and right costal arches.

Herbivores

The bony thorax is compressed laterally in its cranial part and widens caudally in

Carnivores

The bony thorax is stouter and deeper ventrally

ribs

form the skeleton of the lateral thoracic walls.

Intercostal spaces

Ribs are arranged serially in pairs and are interspersed by the

Osseous part, costal cartilage

Each rib consists of a bony dorsal part and a cartilaginous ventral part

costochondral junction

bony dorsal part, the osseous part and a cartilagenous ventral part, the costal cartilage, which meet in the

Sternal or “true ribs”

The first seven to nine ribs articulate directly with the sternum

Asternal or “false ribs”

The remaining caudal ribs articulate indirectly with the sternum by uniting with the cartilage of the rib in front to form the costal arch.

“Floating ribs”

Ribs at the end of the series, whose cartilage ends free in the musculature without attachment to an adjacent cartilage

sternum

consists of an unpaired, segmental series of bones

Intersternal cartilages

The sternum are joined together by

Manubrium, Body, Xiphoid process

Sternum can be divided into three parts:

Manubrium

most cranial part of the sternum

Cylindrical

Body of sternum in carnivores

Wide and flat

Body of sternum in ruminants

Sternal crest

Body of sternum in horses

Xiphoid Process

the last sternebra, which extends into a cartilagenous process caudally