Rickets: Anatomy, Physiology, and Common Signs and Symptoms

Rickets
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Question One
Rickets is a condition characterized by inadequate mineralization of osteoid at the growth plate on children's bones. Growth plates are the areas of growing tissue in children made up of cartilage. These areas are softened by rickets, causing deformities such as bowed legs, thickened ankles and wrists, and a projected breastbone. Growth plates in children with rickets become irregular and widened.
Bone mineralization occurs by endochondral and intramembranous ossification. The facial and cranial bones are formed through intramembranous ossification directly from the bone cells. Endochondral ossification occurs at the growth plate and leads to longitudinal growth of the bones where the cartilage is calcified and molded into bone. Calcium is essential in this stage, and lack of it results in widened, irregularly calcified physis. The metaphysis is also affected and presents in the form of enlarged wrists, ankles, and breastbone. Inadequate calcium and phosphorous inhibit the formation of hydroxyapatite crystals, which are the mineral building blocks of the bone. Vitamin D in calcitriol is important in absorbing phosphorous and calcium (OpenStax College, 2013). Inadequate vitamin D results in rickets.
Question Two
The growth plate is an area of new bone growth made of cartilage and hardens into a solid bone once a child grows. Bone development occurs in two processes: intramembranous and endochondral ossification. In intramembranous ossification, the bone is formed directly from bone cells. Endochondral ossification is vital in the longitudinal development of bones and occurs at the physis and epiphyseal growth plate (Bush, Hall, & Macnicol, 2008). Usually, the cartilaginous growth plate is calcified and remodeled into a solid bone. The hyaline cartilage is surrounded by the perichondrium, which becomes infiltrated with blood vessels and osteoblasts at the end of the first trimester. The cartilage in the diaphysis begins to disintegrate, allowing osteoblasts to penetrate and replace the disintegrating cartilage with a spongy bone to form the primary ossification center. The cartilage continues to grow, causing the bone to increase in length. After birth, secondary ossification centers develop in the epiphyses. Hyaline cartilage is replaced by bone during secondary ossification except on the epiphysis surface and between the epiphysis and diaphysis. This area forms the epiphyseal plate or growth region.
The physis comprises four parallel zones of cartilage cell that include proliferating, resting, hypertrophic and calcifying zones. Through mitosis, the cartilage in the epiphyseal plate next to the epiphysis continues to grow. Osteoid and calcium are absorbed in the primary spangiosa to facilitate bone remodeling (Bush, Hall, & Macnicol, 2008). This process continues until the cartilage growth slows and eventually stop...