1. Bone Tissue: This is the primary tissue of the skeletal system, forming the hard and rigid structure of bones. It is a specialized connective tissue made of:

* Osteoblasts: Cells responsible for forming new bone tissue.

* Osteocytes: Mature bone cells that maintain the bone matrix.

* Osteoclasts: Cells responsible for breaking down bone tissue.

* Extracellular Matrix: This is the non-living, hard substance surrounding the bone cells, composed of collagen fibers and calcium phosphate crystals.

2. Cartilage Tissue: This is a type of connective tissue that provides cushioning, support, and flexibility to the skeletal system. It is found in areas like:

* Articular Cartilage: Covers the ends of bones at joints, reducing friction during movement.

* Costal Cartilage: Connects ribs to the sternum.

* Elastic Cartilage: Found in the ear and epiglottis, providing flexibility.

* Fibrocartilage: Found in intervertebral discs and menisci, providing shock absorption.

In addition to these primary tissues, the skeletal system also contains:

* Blood: Contained within the bone marrow, responsible for blood cell production.

* Nerves: Provide communication between the skeletal system and the central nervous system.

* Connective Tissue: Found in the periosteum (outer covering of bone) and endosteum (lining of bone marrow cavity), providing support and attachment points for muscles.

So, while bone tissue is the defining element of the skeletal system, cartilage and other supporting tissues play crucial roles in its function and structure.