Everybody that loves dogs should know a little bit about anatomy. Dog bone anatomy is not too difficult. Here we will learn about the dog skeleton. To understand health problems in dogs we first should know how organs work, but organs are held in place and protected by the skeleton.
The dog skeleton is the bony part of dogs made for the support and protection of internal organs. Bones are connected through joints and muscles move the bones to produce the normal dog movements.
In this article we will cover:
Let’s check the parts of the dog skeleton one by one.
Bone types and parts of the dog skeleton
Regarding bone types, the dog skeleton is made of three main types of bones: long, irregular (no particular shape) and flat bones
In the big picture, the dog skeleton is made of two basic parts: axial and appendicular (limbs).
Axial skeleton = head (skull) + the spine (made of vertebrae) + ribs + sternum
Appendicular = forelimb bones + hindlimb bones
The dog skull
The head bones make the skull. The skull is made mostly of flat bones that protect internal organs located in 3 cavities: the cranial cavity, the nasal cavity, and the oral cavity. The cranial cavity is the place for the brain.
Skull = face (with nasal and oral cavity) + cranium (with cranial cavity)
The nasal cavity is filled with labyrinth lie bones covered by the nasal mucosa.
Several bones in the skull are hollow and house cavities that are normally covered with a mucous membrane. These cavities are called sinuses (inflammation of this mucosa is called sinusitis).
The skull has many holes (called foramen in anatomy) that let blood vessels and nerves in and out.
What is considered the face in the dog skeleton?
In front of the eye sockets is the area we call face. Behind the eye sockets is the region we call the cranium.
The bones of the face are:
- Frontal (shared by face and cranium, frontal sinus inside)
- Maxilla (maxillary sinus inside)
- Mandible (jawbone)
The bones of the cranium are:
- Frontal (shared by face and cranium, frontal sinus inside)
The mandible connects with the temporal bone of the skull and forms the temporomandibular joint which is used to perform chewing (and biting!) on dogs.
The mandible and the maxilla are the lower and upper jawbones. Both have sockets to house the teeth. Incisive bone also has sockets, for upper incisive bones.
Interestingly, teeth are not bones, therefore they are not part of the skeleton. They are special bony structure coated with a substance with a hardness similar to diamond: the enamel.
The spine has 5 regions (1) cervical or neck, 2) thoracic (upper back) 3) lumbar (lower back) 4) sacral (sacrum bone), and 5) coccygeal (tail), all composed of vertebrae.
Vertebrae are irregular type bones, ring-shaped with the function of being the axis of the dog body and to protect the spinal cord (a part of the central nervous system conveying nervous signals from and to the brain).
The spine is made of several bones (vertebrae) to absorve the forces generated in the dog limbs (when dogs jump, run, etc.) that otherwise would break the spine (if it was a single long bone).
Vertebrae vary along the different regions of the spine, but most have bony projections in common. For instance, the spinous process (single, projecting upward) and transverse processes (paired, projected laterally). Projections in bones are usually meant for the attachment of muscles. The lower cylindric shape par is called the body (the floor of the ring) and the arch (lateral and ceiling parts of the ring).
The first two vertebrae in the cervical (neck) region are special shaped. The first vertebra is called atlas and connects to the occipital bone of the skull, in such a way that dogs can make a yes movement of the head. The second vertebra is called axis and connects with the atlas in a joint that allows laterality of the head (like when we say “no”).
The sacrum is a bone resulting from the fusion of three sacral vertebrae.
The coccygeal vertebrae make the bony part of the tail.
Besides the thoracic vertebrae, the trunk is composed of ribs (13 pairs in the dog) and the sternum. All ribs except the last pair (floating ribs) are connected to the sternum. All three: thoracic vertebrae, ribs, and the sternum are the bony thorax and protect internal thoracic (mostly vital) organs.
The sternum is in the lower position and is made of the connection of several bones called sternebrae (similarly as several bones called vertebrae compose the spine).
From proximal (near the body) to distal (away from the body) the bones of the forelimb skeleton are:
Scapula (flat bone, connects the forelimb to the side of the body).
Humerus (long bone, is the bone of the arm)
Ulna, radius (they are together side by side, they are the bones that make the forearm)
Carpal bones (They are mostly short bones, they form the wrist)
Metacarpals (they are five bones; they are the bones of the palm)
Phalanges (they are usually 3. They are the bones of the fingers; dogs have 5 fingers. Finger#1 is the thumb and only has two phalanges, the rest have three. The names of the phalanges are proximal, middle, and distal, being proximal the closest to the body; the thumb only has proximal and distal, no middle). Curious fact: the last (distal) phalange on each finger has a horn-shaped projection that supports the nail.
From proximal (near the body) to distal (away from the body) the bones of the hindlimb skeleton are:
Hip bone (2 coxae bone, right and left; each coxae bone is made of three bones: ischium, ilium and pubis; together they surround the pelvis cavity, that is, the floor and the lateral walls of the bony pelvic cavity, the sacrum makes the roof). Connects the hindlimb to the spine (sacral region).
Femur (is a long, bony base of the thigh)
Patella (knee bone, forms part of the knee joint, together with the femur and tibia and fibula)
Sesamoid bones (2 small bones, behind the knee, called lateral and medial)
Tibia and fibula (they are together side by side and form the bony part of the leg)
Tarsal bones (they conform the heel and ankle)
Phalanges (foot fingers, similar to those in the hand, hindleg)
Joints are the connections between bones in the dog skeleton.
Check our articles on dog joints to learn how they function and diseases in dogs associated with pain and movement problems (like arthritis).