![]() ![]() (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. Each haversian systems run lengthwise along the bone & consists of laminated (multilayered) cylinder composed of concentric layers of ossified bone matrix arranged around a central canal.Much of the information in this section is not in scope for AP ®. They make up the shafts of long bones & the outside layer of all is composed of tiny compacted cylinders of bone called the Haversian system. ![]() Alternatively, compact bone is very heavy, dense & strong. The organization of the spicules of cancellous bone may appear random, but spicules are actually arranged to stand up to the forces bone is subjected to. It is light, but amazing strong & helps reduce the weight of the bones of the skeleton without significantly reducing the strength. To the naked eye, the many spicules & spaces give cancellous bone its spongy appearance. In life, the spaces between the spicules are occupied by bone marrow. Cancellous bone consists of tiny spicules of bone that appear randomly arranged with lots of spaces between them. ![]()
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