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Skeletal system: Difference between revisions
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'''Spongy''' | '''Spongy''' | ||
The spongy bone is where all of the blood cells are created from the bone marrow. Spongy bone contains two different types of bone marrow: red and yellow marrow. The red bone marrow produces red and white blood cells and platelets. The yellow bone marrow, however, is used to store fats.[http://webschoolsolutions.com/patts/systems/skeleton.htm] | The spongy bone is where all of the blood cells are created from the bone marrow. Spongy bone contains two different types of bone marrow: red and yellow marrow. The red bone marrow produces red and white blood cells and platelets. The yellow bone marrow, however, is used to store fats.[http://webschoolsolutions.com/patts/systems/skeleton.htm] | ||
==Cartilage== | |||
Cartilage is a tough, elastic, and flexible [[connective tissue]]. The ground substance of cartilage is composed primarily of chondroitin. Its extracellular material is produced by chondrocytes, or mature cartilage cells. These cells are too large to directly inhabit the matrix. Instead, they reside in hollow spaces in the ground substance called lacuna. Another unusual characteristic of cartilage in comparison to other connective tissues is it is avascular, meaning that it lacks blood vessels. This is an issue because the chondrocytes are still living cells and require oxygen and other nutrients to function. Therefore, the elements necessary for the cells' survival must diffuse through the matrix. For this reason, the extracellular matrix cannot be very thick. Regardless, cartilage is very strong and durable to withstand arduous circumstances. | |||
Often, cartilage is only a temporary form of [[connective tissue]], later to be replaced by bone. In the early stages of life, a baby’s skeletal system is composed entirely out of cartilage. As the baby develops in the mother’s womb, however, the cartilage is gradually replaced by bone in a process called ossification. This change occurs because bones, which have their own blood vessels, are more self-efficient than the cartilage which depends upon diffusion for its nutrients. Some parts of the body, however, remain as cartilage throughout a person’s life. Examples include the tip of the nose, the external ear, the walls of the [[trachea]], and the [[larynx]]. There are three specific types of cartilage: hyaline cartilage, elastic cartilage, and fibrocartilage. <ref name=Cartilage>[http://www.mhhe.com/biosci/ap/histology_mh/cartilag.html Cartilage] by The McGraw-Hill Companies</ref><ref name=45-46>Wile, Jay L., Shannon, Marilyn M., ''The Human Body: Fearfully and Wonderfully Made!'' 2001. Published by Apologia Educational Ministries, Inc. Anderson, IN. Printed by CJK. Cincinnati, OH. Sixth Printing 2008. p.50</ref> | |||
<ref name=Cart>[http://www.bcb.uwc.ac.za/Sci_Ed/grade10/mammal/cart.htm Cartilage] by Dr. Harry K. Wong, The Department of Biodiversity & Conservation Biology, The University of the Western Cape.</ref> | |||
=== Joints === | === Joints === | ||
