![]() ![]() Intervertebral discs also act as ligaments to bind vertebrae together. Each disc is part of a joint that allows for some movement of the spine and acts as a cushion to absorb shocks from movements such as walking and running. Intervertebral discs composed of fibrous cartilage lie between adjacent vertebral bodies from the second cervical vertebra to the sacrum. The arched curvature of the vertebral column increases its strength and flexibility, allowing it to absorb shocks like a spring ( Figure 29.8). The thoracic and sacral curves are concave-curve inwards relative to the front of the body-and the cervical and lumbar curves are convex-curve outwards relative to the front of the body. The names of the spinal curves correspond to the region of the spine in which they occur. The vertebral column is approximately 71 cm (28 inches) in adult male humans and is curved, which can be seen from a side view. There is also a notch on each side through which the spinal nerves, which serve the body at that level, can exit from the spinal cord. (credit a: modification of work by Uwe Gille based on original work by Gray's Anatomy credit b: modification of work by NCI, NIH)Įach vertebral body has a large hole in the center through which the nerves of the spinal cord pass. (b) Spinal curves increase the strength and flexibility of the spine. The adult vertebrae are further divided into the seven cervical vertebrae, 12 thoracic vertebrae, and five lumbar vertebrae ( Figure 29.8).įigure 29.8 (a) The vertebral column consists of seven cervical vertebrae (C1–7), 12 thoracic vertebrae (Th1–12), five lumbar vertebrae (L1–5), the os sacrum, and the coccyx. We begin life with approximately 33 vertebrae, but as we grow, several vertebrae fuse together. Around the age of 70, the sacrum and the coccyx may fuse together. The coccyx is typically three to four vertebrae that fuse into one. ![]() In the adult, the sacrum is typically composed of five vertebrae that fuse into one. The adult vertebral column comprises 26 bones: the 24 vertebrae, the sacrum, and the coccyx bones. The vertebral column, or spinal column, surrounds and protects the spinal cord, supports the head, and acts as an attachment point for the ribs and muscles of the back and neck. In animals with teeth, the mandible brings the surfaces of the teeth in contact with the maxillary teeth. The mandible controls the opening to the airway and gut. The mandible articulates with the base of the skull. It acts as a movable base for the tongue and is connected to muscles of the jaw, larynx, and tongue. The hyoid bone lies below the mandible in the front of the neck. The facial bones of the skull form the face and provide cavities for the eyes, nose, and mouth.Īlthough it is not found in the skull, the hyoid bone is considered a component of the axial skeleton. Information presented and examples highlighted in this section are not within the scope for AP ® and do not align to the Curriculum Framework.įigure 29.7 The cranial bones, including the frontal, parietal, and sphenoid bones, cover the top of the head. Exploring the evolution of the musculoskeletal system in animals would provide information on this history. Literally step-by-step, these adaptations accumulated. ![]() From an evolutionary perspective, the transition of animals onto land required changes in body design as locomotion on land presented a number of new challenges for animals that were adapted to movement in the water, such as the effect of gravity and lack of buoyancy. ![]() Humans and most animals depend on movement for daily activities. Events occurring at the neuromuscular junction are similar to events occurring at synapses between neurons as discussed in the chapter on the nervous system. In a later section, knowledge of the nervous system will be used to understand the musculoskeletal system because muscle contraction depends on neural input. Bones provide a storage area for calcium and phosphorus salts, and also are the site of blood cell formation. However, as a student of biology, you should have a fundamental understanding of how the muscular and skeletal systems work together to provide support and protection while allowing for a range of movement. Much of the information in this section is not in scope for AP ®. ![]()
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