Connective tissue is a diverse and essential component of the body, providing support, binding together other tissues, and performing various other functions.
The main types of connective tissue are classified into four broad categories:
1. Connective Tissue Proper
- **Loose Connective Tissue:**
- **Areolar Tissue:** Widely distributed under epithelia, packing material around organs.
- **Adipose Tissue:** Stores fat, insulates, and cushions organs.
- **Reticular Tissue:** Forms a soft skeleton (stroma) to support lymphoid organs (e.g., lymph nodes, bone marrow, spleen).
- **Dense Connective Tissue:**
- **Dense Regular Tissue:** Parallel collagen fibers; found in tendons and ligaments.
- **Dense Irregular Tissue:** Irregularly arranged collagen fibers; found in the dermis, joint capsules.
- **Elastic Tissue:** High proportion of elastic fibers; found in the walls of large arteries, bronchial tubes.
2. **Cartilage:**
- **Hyaline Cartilage:** Most common type; found in the nose, trachea, larynx, and at the ends of long bones.
- **Elastic Cartilage:** Contains more elastic fibers; found in the external ear and epiglottis.
- **Fibrocartilage:** Highly compressible with great tensile strength; found in intervertebral discs, menisci of the knee, and pubic symphysis.
3. **Bone (Osseous Tissue):**
- **Compact Bone:** Dense and provides strength and support; found in the outer layer of bones.
- **Spongy Bone (Cancellous Bone):** Lighter, less dense; found at the ends of long bones and in the interior of other bones.
4. **Blood:**
- Blood is a unique type of connective tissue with a fluid matrix (plasma) and no fibers under normal conditions. It consists of red blood cells, white blood cells, and platelets, and it circulates throughout the body delivering nutrients, oxygen, and removing waste.