Why is the axial skeleton critical to life

Once the area of bone has been resorbed, the osteoclasts move on, while the osteoblasts move in to rebuild the bone matrix.

Osteoblasts synthesise collagen fibres and other organic components that make up the bone matrix. They also secrete alkaline phosphatase, which initiates calcification through the deposit of calcium and other minerals around the matrix Robson and Syndercombe Court, As the osteoblasts deposit new bone tissue around themselves, they become trapped in pockets of bone called lacunae. Once this happens, the cells differentiate into osteocytes, which are mature bone cells that no longer secrete bone matrix.

The remodelling process is achieved through the balanced activity of osteoclasts and osteoblasts. If bone is built without the appropriate balance of osteocytes, it results in abnormally thick bone or bony spurs. Conversely, too much tissue loss or calcium depletion can lead to fragile bone that is more susceptible to fracture. Typical features on X-ray include focal patches of lysis or sclerosis, cortical thickening, disorganised trabeculae and trabecular thickening. As the body ages, bone may lose some of its strength and elasticity, making it more susceptible to fracture.

This is due to the loss of mineral in the matrix and a reduction in the flexibility of the collagen. Adequate intake of vitamins and minerals is essential for optimum bone formation and ongoing bone health. Two of the most important are calcium and vitamin D, but many others are needed to keep bones strong and healthy Box 2. Key nutritional requirements for bone health include minerals such as calcium and phosphorus, as well as smaller qualities of fluoride, manganese, and iron Robson and Syndercombe Court, Calcium, phosphorus and vitamin D are essential for effective bone mineralisation.

Vitamin D promotes calcium absorption in the intestines, and deficiency in calcium or vitamin D can predispose an individual to ineffective mineralisation and increased risk of developing conditions such as osteoporosis and osteomalacia. Other key vitamins for healthy bones include vitamin A for osteoblast function and vitamin C for collagen synthesis Waugh and Grant, Physical exercise, in particular weight-bearing exercise, is important in maintaining or increasing bone mineral density and the overall quality and strength of the bone.

This is because osteoblasts are stimulated by load-bearing exercise and so bones subjected to mechanical stresses undergo a higher rate of bone remodelling. Reduced skeletal loading is associated with an increased risk of developing osteoporosis Robson and Syndercombe Court, Bone is a dynamic structure, which is continually remodelled in response to stresses placed on the body.

Changes to this remodelling process, or inadequate intake of nutrients, can result in changes to bone structure that may predispose the body to increased risk of fracture.

Part 2 of this series will review the structure and function of the skeletal system. Tagged with: Newly qualified nurses: systems of life. Sign in or Register a new account to join the discussion. You are here: Orthopaedics. Skeletal system 1: the anatomy and physiology of bones.

Abstract The skeletal system is formed of bones and cartilage, which are connected by ligaments to form a framework for the remainder of the body tissues. This article has been double-blind peer reviewed Scroll down to read the article or download a print-friendly PDF here if the PDF fails to fully download please try again using a different browser Read part 2 of this series here. Box 1. Types of bones Long bones — typically longer than they are wide such as humerus, radius, tibia, femur , they comprise a diaphysis shaft and epiphyses at the distal and proximal ends, joining at the metaphysis.

Most long bones are located in the appendicular skeleton and function as levers to produce movement Short bones — small and roughly cube-shaped, these contain mainly cancellous bone, with a thin outer layer of cortical bone such as the bones in the hands and tarsal bones in the feet Flat bones — thin and usually slightly curved, typically containing a thin layer of cancellous bone surrounded by cortical bone examples include the skull, ribs and scapula.

Most are located in the axial skeleton and offer protection to underlying structures Irregular bones — bones that do not fit in other categories because they have a range of different characteristics. They are formed of cancellous bone, with an outer layer of cortical bone for example, the vertebrae and the pelvis Sesamoid bones — round or oval bones such as the patella , which develop in tendons. Box 2. Vitamins and minerals needed for bone health Key nutritional requirements for bone health include minerals such as calcium and phosphorus, as well as smaller qualities of fluoride, manganese, and iron Robson and Syndercombe Court, Danning CL Structure and function of the musculoskeletal system.

In animals with teeth, the mandible brings the surfaces of the teeth in contact with the maxillary teeth. 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.

The adult vertebral column is comprised of 26 bones: the 24 vertebrae, the sacrum, and the coccyx bones. In the adult, the sacrum is typically composed of five vertebrae that fuse into one. We begin life with approximately 33 vertebrae, but as we grow, several vertebrae fuse together. The adult vertebrae are further divided into the 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae.

Vertebral column : a The vertebral column consists of seven cervical vertebrae C1—7 , twelve thoracic vertebrae Th1—12 , five lumbar vertebrae L1—5 , the sacrum, and the coccyx. Each vertebral body has a large hole in the center through which the nerves of the spinal cord pass.

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. The names of the spinal curves correspond to the region of the spine in which they occur. The thoracic and sacral curves are concave, while the cervical and lumbar curves are convex.

The arched curvature of the vertebral column increases its strength and flexibility, allowing it to absorb shocks like a spring. Intervertebral discs composed of fibrous cartilage lie between adjacent vertebral bodies from the second cervical vertebra to the sacrum. Each disc is part of a joint that allows for some movement of the spine, acting as a cushion to absorb shocks from movements, such as walking and running. Intervertebral discs also act as ligaments to bind vertebrae together.

The inner part of discs, the nucleus pulposus, hardens as people age, becoming less elastic. This loss of elasticity diminishes its ability to absorb shocks. The thoracic cage, also known as the ribcage, is the skeleton of the chest. It consists of the ribs, sternum, thoracic vertebrae, and costal cartilages. The thoracic cage encloses and protects the organs of the thoracic cavity, including the heart and lungs. It also provides support for the shoulder girdles and upper limbs, and serves as the attachment point for the diaphragm, muscles of the back, chest, neck, and shoulders.

Changes in the volume of the thorax enable breathing. Thoracic cage : The thoracic cage, or rib cage, protects the heart and the lungs. The sternum, or breastbone, is a long, flat bone located at the anterior of the chest.

It is formed from three bones that fuse in the adult. The ribs are 12 pairs of long, curved bones that attach to the thoracic vertebrae and curve toward the front of the body, forming the ribcage.

Costal cartilages connect the anterior ends of the ribs to the sternum, with the exception of rib pairs 11 and 12, which are free-floating ribs.

The appendicular skeleton supports the attachment and functions of the upper and lower limbs of the human body. The human appendicular skeleton is composed of the bones of the upper limbs which function to grasp and manipulate objects and the lower limbs which permit locomotion.

It also includes the pectoral or shoulder girdle and the pelvic girdle, which attach the upper and lower limbs to the body, respectively.

Appendicular skeleton : The appendicular skeleton is composed of the bones of the pectoral limbs arm, forearm, hand , the pelvic limbs thigh, leg, foot , the pectoral girdle, and the pelvic girdle. The pectoral girdle bones, providing the points of attachment of the upper limbs to the axial skeleton, consists of the clavicle or collarbone in the anterior, as well as the scapula or shoulder blades in the posterior.

The clavicles, S-shaped bones that position the arms on the body, lie horizontally across the front of the thorax chest just above the first rib. Pectoral girdle : a The pectoral girdle in primates consists of the clavicles and scapulae. The scapulae are flat, triangular bones that are located at the back of the pectoral girdle. They support the muscles crossing the shoulder joint. The spine runs across the back of the scapula; it is a good example of a bony protrusion that facilitates a broad area of attachment for muscles to bone.

The upper limbs contain 30 bones in three regions: the arm shoulder to elbow , the forearm ulna and radius , and the wrist and hand. The humerus is the largest and longest bone of the upper limb and the only bone of the arm. It articulates joins with the scapula at the shoulder and with the forearm at the elbow. The forearm, extending from the elbow to the wrist, consists of two bones: the ulna and the radius. The radius, located along the lateral thumb side of the forearm, articulates with the humerus at the elbow.

The ulna, located on the medial aspect pinky-finger side of the forearm, is longer than the radius. It articulates with the humerus at the elbow. The radius and ulna also articulate with the carpal bones and with each other, which in vertebrates enables a variable degree of rotation of the carpus with respect to the long axis of the limb. The skeletal system includes all of the bones, cartilages, and ligaments of the body.

It serves to support the body, protect the brain and other internal organs, and provides a rigid structure upon which muscles can pull to generate body movements. It also stores fat and the tissue responsible for the production of blood cells. The skeleton is subdivided into two parts. The axial skeleton forms a vertical axis that includes the head, neck, back, and chest. It has 80 bones and consists of the skull, vertebral column, and thoracic cage. The adult vertebral column consists of 24 vertebrae plus the sacrum and coccyx.

The thoracic cage is formed by 12 pairs of ribs and the sternum. The appendicular skeleton consists of bones in the adult and includes all of the bones of the upper and lower limbs plus the bones that anchor each limb to the axial skeleton. The axial skeleton forms the vertical axis of the body and includes the bones of the head, neck, back, and chest of the body. It consists of 80 bones that include the skull, vertebral column, and thoracic cage.

The appendicular skeleton consists of bones and includes all bones of the upper and lower limbs. The axial skeleton supports the head, neck, back, and chest of the body and allows for movements of these body regions.

By the end of this section, you will be able to: Discuss the functions of the skeletal system Distinguish between the axial skeleton and appendicular skeleton Define the axial skeleton and its components Define the appendicular skeleton and its components. Figure 7. It consists of the skull, vertebral column including the sacrum and coccyx , and the thoracic cage, formed by the ribs and sternum.

The appendicular skeleton is made up of all bones of the upper and lower limbs. Previous Next. Order a print copy As an Amazon Associate we earn from qualifying purchases.

We recommend using a citation tool such as this one. Authors: J. Gordon Betts, Kelly A. Young, James A. Kruse, Oksana Korol, Jody E.