Thanks to the joint actions of the dog´s bone and muscular systems they allow him to fulfill multiple functions such as moving, fleeing from danger, looking for food and protecting himself from weather conditions. The lack of information available regarding the functioning of the bone system and the very important care that must be taken for the healthy development of their bones can have a negative impact on the dog´s well-being. The following article will provide you with important information regarding the structure and functions of their skeleton, the most common diseases, and what to do to take care of their bones.
What is the skeleton?
The skeleton is the bony framework of the body in all vertebrate animals, which provides the body its shape as well as a firm structure so that he can move around easily. The bones are connected to each other by the ligaments, and the muscles are connected to the bones by the tendons.
Muscular and Skeletal Systems
A dog´s skeleton consists of approximately 319 bones, with certain variations depending on the number of bones in the tail.
What are the main functions of the dog´s skeleton?
The skeletal system provides stability and support to the muscles which in coordination with the muscular system, create movement. Another function is to protect the different parts of the body from possible blows or accidents. For example: the skull bone acts as a protective helmet for the brain, the ribs act as a protective box that surrounds the internal organs (heart, lungs, liver, etc.) and the canal created by the vertebras protects the spinal cord. Another function of the skeleton is to produce red blood cells in the bone marrow, and to store vitamins and minerals for the body to use when it needs them.
The ribs are a protective box for the internal organs
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The skeleton is made up of various types of bones that are classified according to their shape and function:
Long bones
Long bones are characterized by their elongated and cylindrical shape. They are responsible for supporting the weight of the dog´s body and helping him to move. The femur, humerus, tibia, fibula, radius, ulna, metacarpals, and metatarsals belong to this category.
Femur bone
Short bones
Short bones are roughly cube-shaped. They provide stability and little bit of movement in the ankle and wrist joints. The carpal, tarsus and vertebrae are bones in this category.
Flat bones
These bones are flat and wide. They protect the internal organs such as the brain, the heart and the pelvic organs. The bones of the skull, hip, ribs, and shoulder blades are examples of this group.
Shoulder blade bone
Skeletal divisions
The skeleton is divided into 3 parts:
1. Axial skeleton
It is called axial because it is located on the central axis of the body. It comprises the bones of the head, spine, ribs, and sternum.
Skull bones
The skull bones can be classified into 2 groups: 1) bones of the cranium 2) bones of the face.
Bones of the cranium: they form the bone box which is responsible for covering and protecting the brain. It is made up of the following bones: 2 temporal, 2 parietal, 2 frontal, 1 occipital, 1 inter-parietal, 1 sphenoid, and 1 ethmoid.
Bones of the face: they define the outline of the face and most of the sense organs that are housed within their cavities. The face is composed of the following bones: 2 pre-maxillaries, 2 maxillary, 2 nasals, 2 lacrimals, 2 malars, 2 pterygoids, 2 palatines, 4 turbinates, 1 vomer, 1 mandible and 1 hyoid.
- 1. Maxilla 2. Frontal 3. Lachrymal 4. Palatine 5. Malar 6.Nasal 7. Pre-maxilla 8. Parietal 9. Interparietal 10. Temporal 11. Occipital 12. Lower maxilla or mandible.
The shape of the dog´s head defines the variability between the different breeds of dogs. Dolichocephalic dog breeds have elongated and narrow skulls. The greyhound, the collie and the Afghan hound are part of this group.
Dolichocephalic dog breed
Brachycephalic dog breeds have a short nosed and flattened face. The boxer and the pug fit into this classification.
Mesocephalic breed of dogs has craniums whose length and width is proportional or similar in measurement. The German Shepherd is part of this group.
Mesocephalic dog breed
The vertebral column
Also called the backbone, is the central axis of the skeleton. This part of the body is formed by vertebrae, these are tough rings of bone and their function is to protect the spinal cord from possible injury and potential paralysis. It also provides an attachment point for the ribs.
The vertebral column is comprised of the following bones:
Seven cervical vertebrae (C1- C7): form the bony base of the neck.
Thirteen thoracic vertebrae (T1-T13): form the bony base of the thorax.
Seven lumbar vertebrae (L1-L7): form the bony base of the back.
Three sacral vertebrae (S1-S3): they are formed by the union of several vertebrae that articulate within the pelvic girdle.Coccygeal or caudal vertebrae (20-23): the number of vertebrae varies depending on the breed of dog and form the bony base of the tail.
A. cervical vertebrae B. Thoracic vertebrae C. Lumbar vertebrae D. Sacral vertebrae E. Tail vertebrae.
Between each one of the vertebrae there is an inter-vertebral disc whose main function is to provide mobility and flexibility to the Vertebral column when the dog walks, runs, or jumps.
View of the vertabrae and the intervertebral disk
Ribs
The ribs protect the internal organs located inside the rib cage such as the heart, liver, and lungs. There are 13 pairs of ribs: 9 of them articulate the upper part of the thoracic vertebrae (or dorsal vertebrae) and in the lower area it articulates with the sternum.
The next 3 pairs are known as ¨false ribs¨ as they are not in direct contact with the sternum but are connected by cartilage; while the last pair of ribs are called ¨floating ribs¨, and they are the smallest ones and are not attached to the sternum. The space in between the ribs is called the intercostal space.
Ribs
Sternum
The sternum is located at the center of the thorax. It is an elongated bone, formed by 8 bone segments.
2. Appendicular skeleton
This group of bones determines the movement of the skeleton; it includes the bones of the front and rear limbs. Comparing it to the human body, the front limbs of the dog would be equivalent to the arms and the hind limbs to the legs.
Forelimbs
They are formed by the following bones:
Scapula: also called the shoulder blade, which together with the humerus form the shoulder joint.
Humerus: It is a long bone that extends from the shoulder to the elbow.
Radius and ulna: they are 2 long bones that make up the forearm.
Bones of the paw: comprised of the carpal bones (equivalent to the human wrist), the metacarpal bones (between the wrist and the phalanges/fingers), and the phalanges/digits (fingers).
Bones of the forelimb
Hind limbs
They are in charge of the dog´s locomotion and are made up of the following bones:
Coxal bone: the largest of the flat bones, comprised of 3 bones welded together: the ilium, the ischium, and the pubis.
Femur (upper extremity): forms the bony structure of the thigh and extends from the hip to the knee.
Tibia and fibula: 2 bones that form the leg where the bones are arranged in parallel with one next to the other; these bones connect the knee to the tarsus (ankle joint).
Foot bones: composed of 3 sections: tarsus (equivalent to the ankle, also called hock), metatarsals bones and phalanges/digits (fingers).
Imagen / Florian Scheuerer
Skeleton of a mammal
3. Splanchnic or visceral skeleton
The visceral skeleton are those bones that develop inside the parenchyma of some soft organs or viscera, such as the heart bone of the ox and the bone of the dog’s penis.
We must remember the importance of keeping the dog´s bones healthy, since they protect the internal organs, form the basis of his body, and allow for his mobility. The puppy´s skeleton is primarily cartilaginous when he is born, and unlike bone, cartilage is flexible and can change shape and he could develop hip dysplasia and elbow dysplasia if overweight. To avoid the appearance of these disorders, it is very important to have his growth and weight well under control. Let’s look at some of the situations that could affect the health of his bones:
Obesity
Puppy overfeeding is one of the main causes of the development of hip dysplasia, elbow dysplasia, malformations and joint problems. Although it is true, that the hereditary genetic factor is the trigger for hip dysplasia and elbow dysplasia, external factors precipitate their appearance, as is the case of obesity due to overeating.
Excess exercise Puppies during their growing phase need to release large amounts of energy and sometimes their owners mistakenly expose them to strong and excessive activities. You should keep in mind that during their growing process, their skeleton is still too immature to withstand the impact of intense exercises which could seriously damage the health of his bones.
Excess calcium
Calcium is important for bone health, but consuming too much of it, can lead to bone disease. If your dog has a well-balanced diet, it is best not to add calcium supplements.
There are some signs that may indicate that your dog has some type of bone or joint problem: he does not want to participate in physical activities that he used to enjoy, has difficulty walking up and down stairs, presents limb weakness, lameness, trouble getting up, and growling when he is touched. If he presents any of these symptoms or similar signs, you should take him immediately to the veterinarian.
Vitamin deficiency diseases which are caused by poor nutrition can also occur. Some of these diseases are:
Rickets
This disease is characterized by bowed limbs, pelvic deformities, and curvatures of the spine. It is produced by the deficiency of nutrients especially of vitamins D and lack of adequate calcium and phosphorus. To avoid rickets, vitamins that are not in their food should be added to his diet, and if necessary, any other treatment recommended by the veterinarian.
Nutritional secondary hyperparathyroidism
It is a disease caused by an elevation of the parathyroid hormone that is secondary to inadequate nutrition. This disease is the result of a nutritional deficiency in Calcium, vitamin D, and/or excess phosphorus. Its symptoms include lameness, pain, bone deformities, bone fractures, and joint inflammation. Eating a balanced diet will help him recover.
Juvenile osteoporosis
Osteoporosis is characterized by a significant loss of bone density; the bones become so weak that the risk of fracture is high. The main cause is that there is an imbalance in the consumption of calcium and phosphorus.
Conclusions: just as human beings need exercises and balanced nutrition to stay healthy, it is also important in dogs to avoid disease, injury, and paralysis. While it is true that some bone diseases have a genetic predisposition, a preventive lifestyle reduces the chances of having them.