Answer:
External factors include physical and chemical signals. Growth factors are proteins that stimulate cell division. – Most mammal cells form a single layer in a culture dish and stop dividing once they touch other cells. Two of the most important internal factors are kinases and cyclins.
<span>The outermost covering of a plant cell is called cell wall. It is made up of cellulose. It surrounds the cell membrane. Its function is to protect the cell, provide mechanical support and maintain the pressure inside the cell. Fluid collects in the vacuole and pushes out against the cell wall. This turgid pressure is responsible for the crispiness of fresh vegetables and flowers.</span><span />
Answer:
1. hyaline cartilage
2. a fibrocartilage
Explanation:
In endochondral ossification to produce fetal vertebrae, cartilage is substituted with a bone. The process of endochondral ossification includes the development of hyaline cartilage, also called the cartilage model. The hyaline cartilage develops from the chondroblasts derived from mesenchymal cells. The division of chondroblasts results in the growth of hyaline cartilage. It is followed by the development of the primary ossification center wherein the cartilage tissue is replaced with the bone matrix.
During the repair of these bones, a fibrocartilage callus is formed. Fibroblasts present in the site where the bone is broken produce collagen fibers and the cells derived from periosteum develop into chondroblasts and begin to produce fibrocartilage in this region. The fibrocartilage and collagen fibers together make the fibrocartilage callus that joins the broken ends of the bone.
