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=Costae=

==Costae==

[[Image:Thorax skeleton.png|thumb|right|150px|Canine thorax showing placement of mitral valve - Wikimedia Commons 2008]]

[[Image:Thorax skeleton.png|thumb|right|150px|Canine thorax showing placement of mitral valve - Wikimedia Commons 2008]]

Costae are arranged in pairs and articulate with two successive vertebrae. Individual ribs have a bony dorsal part, a body of rib, and ventral costal cartilage. They increase in length, curvature and amount of cartilage craniocaudally. The cartilage of last rib may fail to join that of its neighbour and is said to be a '''floating''' rib. Costae join ventrally on the midline at the '''sternum''', which is composed of three parts, the '''manubrium''', '''sternebrae''' and '''xiphoid cartilage'''. The '''manubrium''' is the most cranial and projects beyond the first set of ribs and can be palpated in most species. The '''sternebrae''' is joined by cartilage in young animals that is later replaced by bone and is the main body joining the ribs on the midline. The '''xiphoid cartilage''' is caudal and projects between lower ends of costal arches, providing attachment for the '''linea alba'''.

Costae are arranged in pairs and articulate with two successive vertebrae. Individual ribs have a bony dorsal part, a body of rib, and ventral costal cartilage. They increase in length, curvature and amount of cartilage craniocaudally. The cartilage of last rib may fail to join that of its neighbour and is said to be a '''floating''' rib. Costae join ventrally on the midline at the '''sternum''', which is composed of three parts, the '''manubrium''', '''sternebrae''' and '''xiphoid cartilage'''. The '''manubrium''' is the most cranial and projects beyond the first set of ribs and can be palpated in most species. The '''sternebrae''' is joined by cartilage in young animals that is later replaced by bone and is the main body joining the ribs on the midline. The '''xiphoid cartilage''' is caudal and projects between lower ends of costal arches, providing attachment for the '''linea alba'''.

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=Thoracic Musculature=

==Thoracic Musculature==

[[Image: Cat diaphragm.jpg|thumb|right|150px|Cat diaphragm- Copyright Uwe Gille]]

[[Image: Cat diaphragm.jpg|thumb|right|150px|Cat diaphragm- Copyright Uwe Gille]]

The thoracic muscles are primarily concerned with respiration. Inspiratory muscles enlarge the thoracic cavity whilst expiratory muscles diminish the cavity and force air out. The most important thoracic muscle is the [[Diaphragm - Anatomy & Physiology|'''''diaphragm''''']], which separates the thoracic and abdominal cavities. It is dome-shaped and convex on its cranial surface. Central tendons form the vertex of the diaphragm. In a neutral position (between full inspiration and full expiration) the diaphragm is located at the 6th rib behind the '''olecranon'''. The diaphragm attaches via a muscular periphery to the costal arch.

The thoracic muscles are primarily concerned with respiration. Inspiratory muscles enlarge the thoracic cavity whilst expiratory muscles diminish the cavity and force air out. The most important thoracic muscle is the [[Diaphragm - Anatomy & Physiology|'''''diaphragm''''']], which separates the thoracic and abdominal cavities. It is dome-shaped and convex on its cranial surface. Central tendons form the vertex of the diaphragm. In a neutral position (between full inspiration and full expiration) the diaphragm is located at the 6th rib behind the '''olecranon'''. The diaphragm attaches via a muscular periphery to the costal arch.

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=Abdominal Musculature=

==Abdominal Musculature==

The ventrolateral muscles of the abdomen create the flanks and abdominal floor. All muscles join via aponeuroses in the '''linea alba''' at midline, which runs from the [[Ribs and Sternum - Anatomy & Physiology#Costae|xiphoid process]] to the [[Pelvis - Anatomy & Physiology#Pelvic Girdle|pelvic symphysis]] via the prepubic tendon, ensheathing the '''rectus abdominus'''. The '''external abdominal oblique''' runs caudoventrally from the lateral surface of the ribs and the lumbar fascia to the linea alba. Its caudal border is thickened to form the inguinal ligament and a slit in its aponeurosis forms the superficial inguinal ring. The '''internal abdominal oblique''' runs cranioventrally from the tuber coxae and the thoracolumbar fascia to the linea alba. It forms the cranial border of the inguinal canal. The '''transversus abdominus''' is the deepest muscle of the flank, running dorsoventrally from the inner surface of the last ribs and the transverse processes of the lumbar vertebrae. The '''rectus abdominus''' forms a broad band parallel to the linea alba, arising from the ventral costal cartilages and inserting on the prepubic tendon. It also forms the medial border of the inguinal canal. The '''sublumbar muscles''' include the '''psoas minor''' which is a stabilizer of the vertebral column and may also rotate the pelvis at the sacroiliac joint, and the '''psoas major''' and '''Iliacus'''.

The ventrolateral muscles of the abdomen create the flanks and abdominal floor. All muscles join via aponeuroses in the '''linea alba''' at midline, which runs from the [[Ribs and Sternum - Anatomy & Physiology#Costae|xiphoid process]] to the [[Pelvis - Anatomy & Physiology#Pelvic Girdle|pelvic symphysis]] via the prepubic tendon, ensheathing the '''rectus abdominus'''. The '''external abdominal oblique''' runs caudoventrally from the lateral surface of the ribs and the lumbar fascia to the linea alba. Its caudal border is thickened to form the inguinal ligament and a slit in its aponeurosis forms the superficial inguinal ring. The '''internal abdominal oblique''' runs cranioventrally from the tuber coxae and the thoracolumbar fascia to the linea alba. It forms the cranial border of the inguinal canal. The '''transversus abdominus''' is the deepest muscle of the flank, running dorsoventrally from the inner surface of the last ribs and the transverse processes of the lumbar vertebrae. The '''rectus abdominus''' forms a broad band parallel to the linea alba, arising from the ventral costal cartilages and inserting on the prepubic tendon. It also forms the medial border of the inguinal canal. The '''sublumbar muscles''' include the '''psoas minor''' which is a stabilizer of the vertebral column and may also rotate the pelvis at the sacroiliac joint, and the '''psoas major''' and '''Iliacus'''.

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