Final answer:
Bone blood supply is vital for their health, entering through nutrient foramina to nourish the medullary cavity and spongy bone. Nerves also enter bones to regulate blood and support growth, and damaged blood vessels initiate bone repair after a fracture.
Step-by-step explanation:
Blood and Nerve Supply to Bones
The blood supply to bones is an essential aspect of bone health and function. Arteries carrying oxygen and nutrients enter the bone through small openings called nutrient foramina. These are located in the diaphysis, or shaft, of the bone. Once inside, these arteries supply the spongy bone and the medullary cavity, the central cavity of bone shafts where marrow is stored. The periosteum, the outer surface layer of the bone, contains blood vessels that penetrate the spongy bone, providing the osteocytes with necessary nourishment. Veins then collect the blood as it passes through the marrow cavities and exit the bone through the foramina.
In addition to blood vessels, nerves enter the bone following similar paths. Primarily concentrated in the metabolically active regions of the bone, these nerves are responsible for sensing pain and play roles in the regulation of the blood supply and in bone growth. When a bone fractures, blood from damaged vessels forms a fracture hematoma, initiating the process of bone repair.