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:
- skeleton of the head (skull);
- skeleton of the torso;
- the skeleton of the girdles of the limbs;
- skeleton of free limbs.
Head skeleton (skull)
The skeleton of the head, or skull, consists of the cranium and the lower jaw.
The skeleton of the trunk in all vertebrates consists of a spine and ribs.
The spine of reptiles is divided into sections (there are more of them than in amphibians):
In reptiles, the ribcage first appeared, which consists of the thoracic vertebrae, ribs and sternum.
The ribs of reptiles are long and participate in respiration.
A new breathing mechanism appears in reptiles. Ventilation of the lungs in them occurs due to changes in the volume of the chest. When it increases, air enters the lungs and inhalation occurs. With a decrease in the volume of the chest, air is pushed out of the lungs and exhalation occurs. This is achieved through the work of the intercostal muscles.
In turtles, the ribs are fused with the shell. Therefore, their breathing movements are carried out by the belt of the forelimbs.
Snakes do not have a sternum (and, accordingly, a chest), otherwise it would be impossible to swallow food whole (this is how all snakes eat).
The ingestion of food, which is several times greater than its thickness, is entirely facilitated by the special structure of the jaws of snakes – they are connected to each other with the help of ligaments.
The cervical region consists of 8 (in a lizard) or more vertebrae. The lengthening of the neck, the special structure and connection of the cervical vertebrae ensure the mobility of the head. Thanks to this, reptiles can turn their heads in different directions and better navigate in the environment.
Limb Belts Skeleton
Front limb belt:
- paired shoulder blades;
- paired collarbones;
- paired crow bones (coracoids) connected to the sternum (which provides greater strength to the shoulder girdle).
Hind limb girdle: formed by fused pelvic bones.
The pelvic bones in reptiles fused with two vertebrae, which strengthened the girdle of the hind limbs.
Free limbs skeleton
The free forelimbs are similar in structure to the limbs of amphibians (ground type – consisting of parts and having their own muscle mass). Some members of the class have no limbs (snakes, legless lizards).
Front limb skeleton:
- two bones of the forearm (ulna and radius);
- bones of the hand (consisting of parts: wrist, metacarpus, phalanges of the fingers).
Hind limb skeleton:
- 2 shin bones (tibia and tibia);
- bones of the foot.
In reptiles, intercostal muscles have appeared, with the help of which the position of the ribs changes and, as a consequence, the volume of the chest cavity of the body changes (the costal breathing method has developed).
In reptiles, neck muscles have developed, and the muscles of the limbs have become more developed than in amphibians.