Lab Four: Skeletal Tissues Essay

This week, we are examining tissues of the skeletal system. Specifically, we will investigate the process by which the long bone of the upper arm, the humerus, grows and lengthens in our patient, an 8-year old boy. Then, we will compare this process of growth with the process of healing and repair when this same patient sustains a distal end greenstick fracture of the humerus at his weekly gymnastics practice! Your assignment, which is worth 30 points, is to write a one to two page essay discussing the development and growth of a long bone, such as the humerus.

Then, assume this bone has sustained the injury described above, and describe the process by which this injury is repaired. Be comprehensive! Be creative! Please use appropriate citation in APA format where appropriate. Begin your assignment below: Charce Leonard Bones grow in three stages during life. The bone starts growing in the embryo at around 8 weeks. Ossification is the word for the formation of bone. There are osteoblasts that help form the bone and osteoclasts that eat away at old bone. Bones start off as cartilage, but then is replaced by bone.

Connective tissue forms a sheet where the bones are going to be. These connective tissue sheets are highly invested with blood vessels. Some of the cells in the connective tissue sheets differentiate into osteoblasts. These osteoblasts begin laying down the bone extracellular matrix, called spongy bone. These osteoblasts get trapped within the hard matrix and are then called osteocytes. As time goes more and more osteoblasts form from the connective tissue sheets. The connective tissue sheets, as they become major producers of osteocytes, are no longer called connective tissue sheets.

They are now called the bone’s periosteum. But the newer osteoblasts made by the periosteum cannot enter the spongy bone. So, they begin to accumulate on the edges of the spongy bone. They lay down more hard matrix, but now as compact bone. Then, they get trapped within this matrix and are called osteocytes. Long bones need to grow longer so we grow taller. The way they do this is a modification of the way they grow embryonically. The only cartilage that remains in the bone is the cartilage that is found in the epiphyseal disks. The cartilage within the epiphyseal disks is constantly dividing.

As it makes more cartilage, the older cartilage turns into bone. A greenstick fracture is an incomplete fracture where one side of the bone breaks and the other side bends. A greenstick fracture is most common in children. They occur more in children because children have a relatively more organic matrix and are more flexible than those of adults. There are three stages of healing after a greenstick fracture. In these stages many things happen to the bone. First, there is hematoma formation. The torn blood vessels hemorrhage, and a mass of blood forms at the fracture site.

This mass of blood is also known as a hematoma. The site of the fracture becomes swollen, painful, and inflamed. Next, a fibrocartilaginous callus forms. Granulation tissue forms a few days after the fracture. Then capillaries grow into the tissue and phagocytic cells begin cleaning debris. Finally, new bone trabeculae appear in the fibrocartilaginous callus. The fibrocartilaginous callus converts into a bony callus. This bone callus begins three to four weeks after the fracture occurs, and continues until firm union is formed two to three months later.

After all of those stages are finished, bone remodeling takes place. The excess material on the bone shaft exterior and in the medullary canal is removed, and compact bone is laid down to reconstruct shaft walls. The fracture is finally healed. But, this fracture will not be healed if the child who received the fracture does not seek out medical attention. With a greenstick fracture, the child will most likely be placed in a cast to properly immobilize the bone so the bone will heal properly.