The traditional way to transplant these stem cells is to extract bone marrow from the donor's hip bone with a syringe and introduce the material into the recipient's body. Several marrow diseases can be treated through stem cell transplants, which introduce healthy stem cells to the patient's body to replace the diseased cells. Disorders such as aplastic anemia and myelodysplastic syndromes (MDS) hinder the marrow's ability to produce enough blood cells. Myeloproliferative disorders (MPDs) cause the overproduction of immature cells from the marrow. The body also stores iron in bone marrow.īone marrow can become diseased. Some bones have a lot more red marrow than others - the pelvic bone, the spine's vertebrae and our ribs are all rich with it. If the body needs more blood cells, yellow marrow can transform back into red marrow and produce them. Yellow marrow is mostly fat, and as we age, it can be found in places where red marrow once resided - some of the bones in our arms, legs, fingers and toes, for instance. Stromal stem cells are being studied for their possible use in repairing spinal cord damage and healing disorders of the lymphatic system. This type of stem cell generates bone cells, cartilage, fat cells and connective tissue. HSCs can leave the marrow and enter the bloodstream, where the ratio of blood cells to stem cells is about 100,000-to-1. Marrow stem cells can even produce more marrow stem cells.
HSCs create every type of blood cell: red blood cells (which carry oxygen throughout the body), white blood cells (which fight infections and kill bacteria) and platelets (which help your blood clot). This type of stem cell is responsible for creating billions of new blood cells daily, at a rate of about 8 million every second. In the next section, we'll learn more about bone marrow. It provides structural stability and acts as a kind of shock absorber inside the bone, but without adding too much to the overall weight of the body. Though cancellous bone only makes up about 20 percent of the body's bone mass, it plays important roles in body function. Within these marrow-filled spaces is where new blood cells are produced.
The latticework of tiny chambers is filled either with bone marrow or connective tissue. However, instead of a network of bone structure with periodic gaps, cancellous bone is more like a network of connecting spaces with periodic structure. It's formed by trabeculae, which are needlelike structures that create a meshwork. In the case of long bones such as the femur (the upper leg bone), the periosteum covers the central portion of the bone but - like a sleeveless vest - stops short of the cartilage tissue that resides on both ends of the bone (we'll discuss this cartilage in a later section).Ĭancellous bone, also known as trabecular or spongy bone, is the inner layer of bone and is much less dense than cortical bone. The periosteum contains capillaries that are responsible for keeping the bone nourished with blood. Think of the periosteum as a utility vest that fits over the bone - it has brackets and places for muscles and tendons to attach. Ĭortical bone is covered by a fibrous membrane called the periosteum. It makes up 80 percent of bone mass and is dense, strong and rigid. Cortical bone, also known as compact bone, provides external protection for the inner layer against external force. There are two different types of bone tissue: cortical bone (the outer layer) and cancellous bone (the inner layer).
#Bones that join together and are held in place skin
In this article, we'll discuss one of the systems that makes life possible: the skeletal system.īones prevent you from puddling on the floor in the form of a jellyfish, but what else do they do? Bones rebuild themselves, they produce blood cells, they protect our brains and our organs, they provide a giant system of levers that allow us to move ourselves around, and bones also help maintain a steady amount of calcium in our bodies.Īnd, even if you never make your mark on the world (or in the history books), your bones will stick around long after you have otherwise vanished to declare to the world: "These skeletal remains once supported skin and tissue and organs! This person once existed!" And as the construction crew that unearthed your bones reels back in horror, every life choice you ever made will seem - if but for a moment before you are shoveled into a Dumpster - very much worthwhile.īefore we leave behind our skeletal remains to freak out future generations, we should first learn some basics about bones: What are bones made of? What happens when they break? And just how many of them do you have, anyway?
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