The skeleton and muscles are part of the musculoskeletal system. The skeleton provides support for the body and organs of movement, protects the most important organs. Due to the work of the muscles, movement is carried out.
The skeleton is divided into 4 sections:
- head skeleton (skull);
- skeleton of the torso;
- the skeleton of the girdles of the limbs;
- skeleton of free limbs.
Head skeleton (skull)
The skull is formed by a solid cerebral box and is divided into cerebral and facial regions.
Mammals develop a hard (bony) palate that separates the nasal passage from the mouth and prevents blockage of the airways during meals.
The spine is represented by the following sections:
- cervical spine – all mammals, except sloths and manatees, always have 7 vertebrae. The length of the cervical spine varies depending on height, lifestyle. The first two vertebrae – atlas and epistrophy – are well defined.
- Thoracic region – 12-15 vertebrae. The ribs are attached to the first 7, fused with the sternum. The rest of the vertebrae bear false ribs.
- Lumbar region – 2-9 vertebrae with rudimentary ribs.
- The sacral region is usually formed by 4 fused vertebrae.
- The tail section contains from 3 to 50 vertebrae.
Limb Belts Skeleton
Forelimb girdle (shoulder girdle)
- paired shoulder blades;
- paired collarbones (not developed in all mammals).
Only the platypus and the echidna have paired crow bones (coracoids).
Hind limb girdle (pelvic girdle)
Consists of fused (in most species) paired bones and forms one pelvic bone.
Free limbs skeleton
The limbs are five-fingered, however, in different groups, they undergo significant changes in the course of adapting to various modes of movement – on the ground, sand, trunks and branches of plants, through the air, in water and underground. In terrestrial vertebrates, the upper extremities are lengthened. In aquatic mammals, they turn into flippers. In ungulates, the number of fingers is reduced, etc.
The muscular system is well developed and differentiated. The chewing muscles, muscles of the limbs and trunk are well developed.
A muscular diaphragm appears, which divides the body into two cavities – chest and abdominal. It is she and the intercostal muscles that change the volume of the chest during breathing.
Some mammals have well-developed facial muscles – muscles located on the front of the skull and reflecting the emotions of the animal.
There are muscles that lift the hairs of a mammal (to keep warm, as well as when defending or attacking).