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→Thoracic Vertebrae
==Thoracic Vertebrae==
==Thoracic Vertebrae==
Canines and most mammals have thirteen thoracic vertebrae. Thoracic vertebrae articulate with one another and with the ribs using both cartilaginous and synovial joints (see section above). Thoracic vertebrae are generally very similar throughout the length with only small differences occurring gradually between those vertebrae cranially and caudally. Thoracic vertebrae have short bodies with flattened extremities, short transverse processes and prominent spinous processes. Each body has costal facets which have a synovial joint to articulate with the corresponding rib. These costal facets become more basic the further caudal the vertebrae. The spinous processes reach a maximum height only a few vertebrae behind the cervicothoracic junction and then decline gradually towards the lumbar vertebrae. The orientation of spinous processes shifts from slanting in a general caudal direction for the first eight thoracic vertebrae to slanting in a cranio-dorsal direction for the last few caudal vertebrae.
Canines and most mammals have thirteen thoracic vertebrae. Thoracic vertebrae articulate with one another and with the ribs using both cartilaginous and synovial joints. Thoracic vertebrae are generally very similar throughout the length with only small differences occurring gradually between those vertebrae cranially and caudally. Thoracic vertebrae have short bodies with flattened extremities, short transverse processes and prominent spinous processes. Each body has costal facets which have a synovial joint to articulate with the corresponding rib. These costal facets become more basic the further caudal the vertebrae. The spinous processes reach a maximum height only a few vertebrae behind the cervicothoracic junction and then decline gradually towards the lumbar vertebrae. The orientation of spinous processes shifts from slanting in a general caudal direction for the first eight thoracic vertebrae to slanting in a cranio-dorsal direction for the last few caudal vertebrae.
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===Ribs===
===Ribs===
[[File:Dog ribs.JPG|thumb|right|300px|'''Canine ribs & Sternum''' - Kirill Tsukanov, Moscow State University, 12/04/12]]
[[File:Dog ribs.JPG|thumb|right|300px|'''Canine ribs & Sternum''' - Kirill Tsukanov, Moscow State University, 12/04/12]]
The ribs are paired structures that articulate with a two ribs - the corresponding thoracic vertebrae and also partially with the vertebrae directly caudal. It is the caudal vertebrae that has the same numerical designation as the rib. An individual rib is composed of a number of elements. Dorsally the rib has a tubercle, head and neck. The head of the rib is rounded with two facets, each of which represents the surface which articulates with the vertebral body. The area between the two facets is referred to as the ''crest'' and allows the attachment of the intercapital ligament. The tubercle of the dorsal rib can act as a further third articular facet in more caudal ribs with the transverse processes. The main body of the rib is long and curved and the lateral surface of the rib is often flattened. The highest degree of curvature of the rib is just ventral to the dorsal neck of the rib and is known as the ''angle''. The angle allows the attachment of the iliocostalis muscles whilst the cranial and caudal edges of the rib allow attachment of the intercostal muscles. The caudal aspect of the body of the rib also contains a small groove which is designed to afford protection to the neurovascular bundle that runs along the length of each rib. At the ventral third of each rib the bone structure of the rib is replaced with costal cartilage at the costochondral junction. This costal cartilage is more flexible than the bone and progressively ossifies with age. The cartilage is bent in a cranioventral manner before making contact with the sternum which together with the increased flexibility of the cartilage itself provides the thoracic cavity with a wide degree of changes in shape. There are vast differences in the size of rib depending on which number the rib is - the first rib if usually the shortest and articulates with the sternum in a more rigid manner than caudal ribs to act as an anchor on which the other ribs draw for inspiration. Ventrally the cartilaginous element of the rib articulates with the sternum (see section below) in nearly all ribs. The exception are the most caudal ribs in which the cartilaginous ventral element of the rib fails to make contact with the sternum and is referred to as a 'floating' rib.
The ribs are paired structures that articulate with two ribs - the corresponding thoracic vertebrae and also partially with the vertebrae directly caudal. It is the caudal vertebrae that has the same numerical designation as the rib. An individual rib is composed of a number of elements. Dorsally the rib has a tubercle, head and neck. The head of the rib is rounded with two facets, each of which represents the surface which articulates with the vertebral body. The area between the two facets is referred to as the ''crest'' and allows the attachment of the intercapital ligament. The tubercle of the dorsal rib can act as a further third articular facet in more caudal ribs with the transverse processes. The main body of the rib is long and curved and the lateral surface of the rib is often flattened. The highest degree of curvature of the rib is just ventral to the dorsal neck of the rib and is known as the ''angle''. The angle allows the attachment of the iliocostalis muscles whilst the cranial and caudal edges of the rib allow attachment of the intercostal muscles. The caudal aspect of the body of the rib also contains a small groove which is designed to afford protection to the neurovascular bundle that runs along the length of each rib. At the ventral third of each rib the bone structure of the rib is replaced with costal cartilage at the costochondral junction. This costal cartilage is more flexible than the bone and progressively ossifies with age. The cartilage is bent in a cranioventral manner before making contact with the sternum which together with the increased flexibility of the cartilage itself provides the thoracic cavity with a wide degree of changes in shape. There are vast differences in the size of rib depending on which number the rib is - the first rib if usually the shortest and articulates with the sternum in a more rigid manner than caudal ribs to act as an anchor on which the other ribs draw for inspiration. Ventrally the cartilaginous element of the rib articulates with the sternum (see section below) in nearly all ribs. The exception are the most caudal ribs in which the cartilaginous ventral element of the rib fails to make contact with the sternum and is referred to as a 'floating' rib.
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===Sternum===
===Sternum===
The sternum represents the bony structure that runs ventrally along the thoracic cavity and provides attachment for the ribs and an anchor for some of the muscles involved in respiration. The sternum is composed of three elements; the '''manubrium''', the '''body''' and the '''xiphoid'''. The '''manubrium''' in canines is rod-shaped and projects cranially to the first rib and unless the dog is particularly well muscles, it can often be palpated at the region of the ventral neck. The body of the sternum is composed of numerous segments interconnected by the costochondral ventral aspects of the ribs (see section above) via small depressions in the segments. These segments are referred to as ''sternebrae'' and are cartilaginous in young canines and ossify with age. The body of the sternum in dogs is generally cylindrical in shape. The '''xiphoid''' cartilage extends caudally in a similar manner to that of the manubrium cranially. It provides attachents for the most cranial aspects of the abdomen and also for the ''linea alba''.
The sternum represents the bony structure that runs ventrally along the thoracic cavity and provides attachment for the ribs and an anchor for some of the muscles involved in respiration. The sternum is composed of three elements; the '''manubrium''', the '''body''' and the '''xiphoid'''. The '''manubrium''' in canines is rod-shaped and projects cranially to the first rib and unless the dog is particularly well muscled, it can often be palpated at the region of the ventral neck. The body of the sternum is composed of numerous segments interconnected by the costochondral ventral aspects of the ribs (see section above) via small depressions in the segments. These segments are referred to as ''sternebrae'' and are cartilaginous in young canines and ossify with age. The body of the sternum in dogs is generally cylindrical in shape. The '''xiphoid''' cartilage extends caudally in a similar manner to that of the manubrium cranially. It provides attachents for the most cranial aspects of the abdomen and also for the ''linea alba''.
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