The vertebral column is approximately 70 cm (28 in) in adults and is curved, which can be seen from a side view. There is a notch on each side of the hole through which the spinal nerves, can exit from the spinal cord to serve different regions of the body. Below this level, the hole contains spinal nerves which exit between the vertebrae. Each vertebral body has a large hole in the center through which the spinal cord passes down to the level of the first lumbar vertebra. It consists of 26 bones: the 24 vertebrae, the sacrum, and the coccyx. The vertebral column, or spinal column, surrounds and protects the spinal cord, supports the head, and acts as an attachment point for ribs and muscles of the back and neck. The mandible controls the opening to the mouth and hence, the airway and gut. The mandible forms a joint 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. Facial bones provide cavities for the sense organs (eyes, mouth, and nose), and serve as attachment points for facial muscles. The auditory ossicles consist of two malleus (hammer) bones, two incus (anvil) bones, and two stapes (stirrups), one on each side. The auditory ossicles of the middle ear transmit sounds from the air as vibrations to the fluid-filled cochlea. In the adult they are tightly jointed with connective tissue and adjoining bones do not move. The cranial bones form the cranial cavity, which encloses the brain and serves as an attachment site for muscles of the head and neck. The skull consists of cranial bones and facial bones. The bones of the skull support the structures of the face and protect the brain. (credit: modification of work by Mariana Ruiz Villareal) The appendicular skeleton, shown in red, consists of the bones of the pectoral limbs, pectoral girdle, pelvic limb, and pelvic girdle. Figure 11.25 The axial skeleton, shown in blue, consists of the bones of the skull, ossicles of the middle ear, hyoid bone, vertebral column, and thoracic cage. The axial skeleton forms the central axis of the body and includes the bones of the skull, ossicles of the middle ear, hyoid bone of the throat, vertebral column, and the thoracic cage (rib cage) ( Figure 11.25). The skeletal system in vertebrates is divided into the axial skeleton (which consists of the skull, vertebral column, and rib cage), and the appendicular skeleton (which consists of limb bones, the pectoral or shoulder girdle, and the pelvic girdle).Įxplore the human skeleton by viewing the following video with digital 3D sculpturing. The skeleton has five main functions: providing support to the body, storing minerals and lipids, producing blood cells, protecting internal organs, and allowing for movement. An endoskeleton develops within the body rather than outside like the exoskeleton of insects. The human skeleton is an endoskeleton that consists of 206 bones in the adult. Replacement joints for shoulders, elbows, and fingers are also available. Progress in the science of prosthesis design has resulted in the development of artificial joints, with joint replacement surgery in the hips and knees being the most common. Other diseases affect the joints, such as arthritis, which can make movement difficult and, in advanced cases, completely impair mobility. The most common musculoskeletal diseases worldwide are caused by malnutrition, which can negatively affect development and maintenance of bones and muscles. Injury or disease affecting the musculoskeletal system can be very debilitating. The muscles of the muscular system contract and pull on the bones, allowing for movements as diverse as standing, walking, running, and grasping items. The bones of the skeleton protect the body’s internal organs and support the weight of the body. The muscular and skeletal systems provide support to the body and allow for movement.
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