Final answer:
The outer portion of the periosteum is made of dense irregular connective tissue, which contains blood vessels, nerves, and lymphatics that nourish compact bone. It also facilitates the attachment of tendons and ligaments to bones and plays a vital role in bone growth and repair. The periosteum does not cover areas forming joints, where articular cartilage is present instead.
Step-by-step explanation:
The periosteum is a fibrous membrane that forms the outer surface of bone, providing a surface for the attachment of tendons and ligaments. It is composed of two layers, with the outer layer being made up of dense irregular connective tissue that contains blood vessels, nerves, and lymphatic vessels that nourish the compact bone. The inner layer (or cambium layer) contains progenitor cells that can differentiate into osteoblasts, which are responsible for bone growth and repair. The periosteum is crucial for bone health as it plays an essential role in nourishing bone tissue and facilitating bone repair and growth.
Adjacent to the periosteum is the endosteum, which lines the medullary cavity—the inner space within bones where bone marrow is found. Unlike the periosteum, the endosteum is a delicate membranous lining that contains osteoblasts and osteoclasts that help in bone remodeling. It's important to note that the periosteum does not cover the regions of bones known as epiphyses, which is where joints are formed; in these regions, epiphyses are protected by articular cartilage.