Major Tissues in the Circulatory System
Connective Tissue
below = adipose tissue
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Connective tissue supports, protects, and binds other tissues together. The collagen fibers that are found between connective tissue cells provide strength and flexibility. Some examples of connective tissues are bone, cartilage, blood, and adipose (fat).
Blood is the main connective tissue in the circulatory system, but it's a liquid connective tissue. Blood tissue is in the same family as bone and cartilage, but instead it has a liquid medium that holds it together. The blood's volume is 55% plasma, 44%red blood cells, and 1% platelets and white blood cells. The second inner layer of the arteries is thin and made of elastic and connective tissue. Adipose, or fat, tissue stores energy, forms a protective cushion around organs such as the kidney, insulates and reduces heat loss, and is formed by groups of fat cells. |
Epithelial Tissue
Epithelial tissue, or epithelium, is comprised of sheets of tightly packed cells that coat or line the inner part of hollow organs like the blood vessels, heart, liver, and stomach. Epithelial tissue cells are continually dividing for replacements of old, worn, or damaged cells. Almost all organs are lined with epithelial tissue on the inner cavities. It is the inner and outer lining of arteries, veins, and blood vessels.
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Muscle Tissue
Muscle tissue is made up of muscle cells/fibers that use energy to contract and create a pulling force. Muscle tissue is a group of specialized cells that contract together at the same time to move something.
Smooth muscle tissue is found on the walls of hollow organs and has short fibers with tapering ends. These muscle cells are controlled by the body's autopilot, so you're unaware that it's happening. More specifically, it's controlled by the autonomic nervous system and by hormones. Cardiac muscle tissue is exclusively found in the heart. I t makes the heart contract, or "beat", automatically and tirelessly to pump blood. Cardiac muscle fibers branch to form an inteconnected network with each fiber containing masses of large mitochondria to provide enough energy to keep contracting without break. Inbetween cardiac muscle fibers are myofibrils which contain filaments that interact to cause contraction. The third inner layer of the arteries is thick and is made of muscle and elastic fibers. The middle layer (of three) in the veins is a thin muscle tissue layer. The heart is comprised of many cardiac muscles. The epiglottis is a flap controlled by smooth muscles. The heart has smooth muscle tissue lining. The diaphragm is made of smooth muscle tissue.There are no skeletal muscles in the circulatory system. |
Nervous Tissue
Nervous tissue, also known as neurons, are made of nerve fibers. Nerve fibers are long extensions of neurons that carry electrical signals for coordinating body functions. Billions of neurons, and their support cells, together make up nervous tissue. Each nerve cell has many projections that either receive or transmit electrical signals. Nervous tissue is a network of nerves that relay, produce, and carry high-speed electrical messages called nerve impulses between the brain and various organs in the body.
All of the nerves in the circulatory system's organs are automatic. For example, the heart pumping blood, the kidneys and liver filtering blood, the lungs for breathing (the epiglottis opens for air and the diaphragm relaxes/contracts to let in air or push it out.). |