Well, when chromosomes cross over during prophase 1 of meiosis, the homologous pair of chromosomes exchange segments of DNA which happen to be the genes. So the significance of crossing-over during prophase 1 is that it adds genetic variation to sexually reproducing organisms.
-clears throat and prepares to sing- our whole universe was in a hot dense steep and nearly 14 billion years ago expansion started..........
<span>An event in which rain-cooled air hits the ground and spreads out in all directions is called a </span>downburst.
Nerve that supply bone accompany blood vessels through the nutrient foramen. They are responsible for the innervation of the bone as well as its outer covering, the periostem, the inner lining of the medullary cavity, the endosteum, and the medullary cavity. The nerves that innervates these structures are mainly sensory nerves that signal injuries to the skeleton.
Blood vessels enter the bones from the periosteum through the nutrient foramen (a small opening or hole in the bone), where the nutrient artery enters and where one nutrient veins exists in bone. The blood vessels supply nutrients and oxygen required by cells and remove the waste products from the cells of the bones.
Endosteum functions to cover and lines the bone, it is an incomplete layer of cells that covers all internal surfaces of the bone within the medullary cavity. It contains the Osteoprogenitor cells, osteoblasts and osteoclasts which are important cells of the bone.
Periosteum on the other hand is a fibrous, thick membrane covering the external surface of the bone, apart from the articular cartilage on the epiphysis. It is made of two layers: the outer fibrous layer of dense irregular connective tissues that protects the bone from external structures, anchors the blood vessels and nerves to the surface of the bone. It also serves as an attachment site for ligaments and tendons. The inner cellular layer contains various cells which includes the osteoprogenitor, osteoclasts and osteoblasts.
Phospholipids is the fundamental building block of a new cell membrane
