4 - Chapter 4. SKELETON The skeleton (an organ system) is...

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Chapter 4. SKELETON The skeleton (an organ system) is the framework of hard structures that supports and protects the soft tissues of animals. In order of importance, skeletal structures consist of bones, cartilages, and ligaments; sometimes teeth are included in this grouping. The formal study of bones is called osteology , that of cartilage is chondrology , arthrology in the case of joints, and the study of teeth is called odontology . The skeleton (Figure 4-1) is best considered in terms of two major parts: the axial skeleton and the appendicular skeleton . In some cases a third division, the visceral skeleton , may be included. Figure 4-1. Equine skeleton. Examine this illustration of the horse to develop an appreciation for the relationships that are evident between the skull and neck, the limbs and spine, and ribs and spine. The external surface of the animal is shown in dotted outline to indicate the amount of variation in soft tissue cover of the skeleton. The portions of the skeleton which require detailed treatment are shown in subsequent figures. 2007 version – page 25
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A. The axial skeleton The axial skeleton includes the skull, the vertebrae of the vertebral column, and the ribs and sternum (Figure 4-2). The vertebrae make up a chain, or column, of unpaired dorsomedial bones that extends from the skull to the caudal extremity of the tail. They are divided into five regions: cervical , thoracic , lumbar , sacral , and coccygeal , corresponding to the everyday terms, neck, chest, waist, rump, and tail. Figure 4-2. Axial skeleton. The axial skeleton consists of the skull (sk), the ribs (r), the sternum (st), and the vertebral column, divided here into cervical (ce), thoracic (th), lumbar (lu), sacral (sa), and coccygeal (co) portions. The appendicular skeletal attachments are shown in dotted outline. 1. The vertebrae The sacral vertebrae are partly fused one to another to form a rigid platelike structure that supports the pelvis. The individual bones within each region are named or numbered craniad to caudad. For example, the cervical vertebrae are labeled C-1, C-2, C-3 . . . C-7. Individual vertebrae have distinguishing features that enable a skilled anatomist to uniquely identify them. They also have some common features, and all can be considered to be made up of three parts (Figure 4-3): the body , the arch , and processes. The body is the cylindric mass, oriented craniocaudally along its long axis, upon which all other parts are formed. The body 2007 version – page 26
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of one vertebra is juxtaposed cranially and caudally with bodies of adjacent vertebrae. The apposing surfaces are separated by menisci , or cartilaginous disks. The orientation of the cervical, thoracic, and lumbar vertebrae can usually be deduced from the faces. With few exceptions, the cranial Figure 4-3. Major trunk vertebrae of cattle:C-7. The vertebra consists of a body (1) to which processes are attached. The vertebrae from different locations along the column have characteristic shapes, largely determined by
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This note was uploaded on 03/23/2009 for the course ANSCI 1110 taught by Professor Brucecurrie during the Fall '08 term at Cornell University (Engineering School).

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4 - Chapter 4. SKELETON The skeleton (an organ system) is...

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