Connective Tissue
Very different from Epithelial tissue. It connects and binds tissue together. Can provide support, protection and serves as framework. It can fill spaces, store fat molecules, produce blood, fight infection, and repair tissue damage. Looking at the tissue – there is abundant tissue between cells and has a blood supply (some more than others.)
Major Cell Types:
1. Fibroblasts are the most common cell type. Fibroblasts are star shaped cells that secrete fibers and a rather large compared to other cell types.
2. Macrophages – are scavenger cells that defend against infection.
3. Mast cells are cells involved with the inflammatory process, they release an anticoagulant heparin and histamine which promotes inflammation.
Types of Connective Tissue include
Bone, Loose Connective Tissue, Dense Connective Tissue, Blood and Cartilage.
1. Bone
Also known as osseous tissue are composed of bone cells called osteocytes which sit in small cavities called lacunae. A very hard matrix of calcium salts and large amounts of collagen fibers further support the dense network. Bone is used to protect and support body organs and with movement. Bone has a very good blood supply, which is why it heals faster than most connective tissues.
Appearance: Concentric circles of lamella around a central canal. The central canal is characterized by a dark dense column, such as the center of the bull’s-eye. Lamella are concentric rings around the central canal. Several osteons are stacked next to each other, like columns for support.
2. Loose Connective Tissue
Fibers
Strong collagen fibers are white in color. They are made of the protein collagen to add strength and support for holding body parts together.
Elastic fibers are yellowish, and are made of the protein elastin. They are stretchy and at flexibility to the connective tissue.
Reticular fibers are thin collagen fibers that are branched in appearance and help provide a supportive network in various tissues.
Types of Loose Connective Tissue:
Loose Connective Tissue (Areolar Tissue) – binds body parts together such as the skin and underlying organs. It is very thin and delicate.
Appearance: fibroblasts separated by jelly ground substance containing larger collagen and elastic fibers. On appearance there is more space between the fibers when compared to the other connective tissues.
Adipose Tissue – Adipose tissue is also known as fat. Adipose stores fat beneath the skin, around the joints, and around internal organs. Appearance: large white cells packed together with small black nuclei pushed to the edge.
3. Dense Connective Tissue
Dense Regular Connective Tissue
Very densely packed collagen fibers. The density of fibers allow for its strength is found in tendons and ligaments. However it does have a poor blood supply, which limits its healing and repair capabilities.
Appearance: very dense wavelike pattern of fibers. Fibroblast nuclei elongated and appear squished between the fibers.
Dense Irregular Connective Tissue
Structurally supportive connective tissue that has less fiber density than dense connective tissue. The arrangement of fibers are in different directions unlike dense connective tissue.
Appearance: density of fibers in various directions. Many appear smooth and wavy, and oriented in different directions.
4. Blood
Blood is composed of cells suspended in plasma. Red blood cells transport oxygen and carbon dioxide throughout the body. White blood cells are involved in bacteria, viral, and parasite defense. Additional proteins and substances are found in the blood that provide specific functions to be discussed in future chapters.
5. Cartilage
Cartilage is characterized by a rigid connective tissue that provides support and structure for other tissues. It has a very poor vascular system which is why it heals slowly. Chondrocytes are mature cartilage cells that lie within the lacuna of the gel like fluid matrix. There are three types of cartilage: hyaline, elastic, and fibrocartilage.
Hyaline cartilage
1. Most common cartilage.
2. White with abundant collagen fibers.
3. Found at the end of bones for support and protection.
4. Supports respiratory passages.
5. Identifying description of large chondrocytes with few collagen or elastic fibers in matrix.
Elastic cartilage
Contains increased elastic fibers throughout cartilage which results in its elasticity.
1. Supports the external ear.
2. Characterized by large chondrocytes with some elastic fibers distributed throughout the matrix. Elastic cartilage mixed with collagen fibers.
Fibrocartilage
Characterized by dense fibrous network between chondrocytes. Density of collagen and elastic fibers in matrix allows for little space between fibers in matrix.
1. Found in vertebral discs between the vertebrae of the spinal column.
2. Dense collagen and elastic fibers allow for increased support and force absorption.