Bone as a Connective Tissue

Bone is a Connective Tissue

Recall that the human body only contains four different types of tissues. These include epithelial tissues that line open spaces and muscle tissue that contracts. Nervous tissue conducts electricity. Connective tissue does everything else. It has a variety of functions. It is divided into four main groups. There can be fluid connective tissues like blood. There can be loose connective tissues like adipose or fat. There can be dense connective tissues like a tendon or a ligament. There can be supportive connective tissues like bone and cartilageA flexible connective tissue found in joints, the ear, nose, and rib cage. Cartilage can be of three.

All connective tissues can be thought of like a gelatin mold in which fruits are suspended. The fruits are the specialized cellsThe basic structural and functional units of life. that are contained within the connective tissue. Bone, the primary cell type, is called an osteocyteMature bone cells that maintain bone tissue.; there are other bone cells that exist. The gelatin that comes in powder form in the jello packet is actually a mixture of proteinsLarge molecules made of amino acids with various functions in the body.. These proteins are meant to bind waterThe universal solvent essential for life.. They do this when you add hot water to your jello mix. Together the watery substance and the proteins make the gelatin.

In connective tissue we call this gelatin the matrix. The matrix can contain three different types of fibers: collagenA structural protein in the dermis that provides strength and elasticity., elastin, and reticular fibers. Those are the only three available. If you are in a lab and they ask you about the type of fiber in this connective tissue, mention one or more. Choose from those three fibers. The matrix consists of something called ground substance. This acts like an interstitial substance specific to each connective tissue. Here in bone the ground substance is made mostly of calcium salt. In blood the ground substance is made mostly of water. Bone is rich in collagen fibers for strength. There are some elastin fibers. These give bones the ability to twist, bend, and sway with forces.

Components of Bone

We should think of bone as a gelatin mix. It’s important for us to consider the proportion made up of protein. We must also consider the proportion made up of water.  This is similar to comparing the collagen fibers content in bone. It compares them to the calcium salts content in bone.  As you can see the calcium salts are two times that of the collagen fibers present in bone.

Surprisingly, the specialized cells in bone, such as the osteocytes, only make up a mere 2% of your total bone. When bone is being created in utero, collagen fibers are secreted first. These fibers create a substance made up of organic moleculesGroups of atoms bonded together. called the osteoid. After the osteoid takes shape, it is surrounded by salts mainly made of calcium. As you can see from this graph, some of the salts are made of potassium(K⁺): Major ICF cation; essential for muscle and nerve function., sodium(Na⁺): Major ECF cation; important for fluid balance, nerve function., and magnesium(Mg²⁺): Cofactor for many enzymes; important in muscle and nerve function.. This process of depositing the calcium salts is called calcificationThe hardening of tissues due to calcium salt deposition., which is only part of the generation of bone.

Two Types of Bone Texture

First, consider taking one of your long bones, like the femurThigh bone; longest and strongest bone in the body; has a large round head and prominent trochanters. Then slice it in a frontalForehead bone; forms the front part of the skull and roof of the orbits. Smooth and curved. section A cut or slice of the body or an organ for study. to separate the anteriorThe front of the body or toward the front when standing in the anatomical position. and posterior portions of the bone. We would see something similar to this picture here. As you can see, the bone is not a complete solid mass. Most of the bone is composed of a porous type called spongy boneA porous bone tissue found inside bones, providing lightweight support.. It can withstand twisting, pulling, and pushing from all directions.

Spongy bone is supported or surrounded by a denser form of bone tissue called compact boneDense, strong bone tissue forming the outer layer of bones.. This compact bone is only on the superficialNear the surface of the body. faces of the bone. It gives the bone strength only in certain directions. Sometimes this is called a bone collar of compact bone. Similar to the collar of a shirt, it surrounds the bone. It provides structure and support to maintain its shape. Many of the flat bones in your body are composed of a structure called Diploe. Specifically refers to spongy bone trapped between two layers of compact bone. For flat bones, this diploe structure creates incredible strength which should be expected from the bones that protect your brain.