skeletal system 1 Flashcards
The primary function for the skeletal system is what?
For supporting the body and protecting vital organs
How many bones are we born with? How much is left when we age?
270
206 named bones
What are bones made up of?
Bones are made up of a complex arrangement of inorganic minerals and a variety of tissues including bone, bone marrow, nerves, blood vessels, endothelial, and cartilage
What are the functions of bones?
- Protection - of organs (skull protects the brain, ribs protects the heart, etc)
- Support and framework for the human body
- Movement - by providing attachment points for muscles
- pH balance - of the blood by absorbing or releasing bone minerals
- Hematopoiesis - (blood production) in blood marrow
- Fat storage - in yellow bone marrow
- Sound transduction - through small bones located in the ear canal
- Storage of growth factor in bone matrix
- Removal of heavy metals or foreign chemicals - to detoxify blood and release slowly for excretion
- Mineral storage - of calcium and phosphorous
- Production of hormones - such as ostocalcin
What are bone minerals mostly made of?
Calcium and phosphorous
Bone mineral is created by what? And it allows what?
Osteoblasts
Allows bones to withstand large amounts of compressional force
What is the other major component of bone matrix?
Organic collagen, which is a protein that gives bone the ability to withstand stretching forces
What are the major cells that contribute to building and breaking down bone matrix and bone structure?
Osteoblasts, osteocytes, and osteoclasts
Osteoblasts are responsible for what?
Responsible for creating bone matrix, and therefore building bone
When does osteoblasts become osteocytes?
Once osteoblasts have become trapped in the bone matrix they have created, they become osteocytes
What is the function of osteocytes?
Maintain the bone matrix and calcium homeostasis
Osteocyte, a cell that lies within the substance of fully formed bone. It occupies a small chamber called a lacuna, which is contained in the calcified matrix of bone. Osteocytes derive from osteoblasts, or bone-forming cells, and are essentially osteoblasts surrounded by the products they secreted.
Where are osteocytes located?
Lacunae
What are osteoclasts?
Large cells that are capable of reabsorbing bone minerals, and therefore remodeling bone structure
They also remove minerals to the bloodstream for a variety of bodily functions, such as muscle contraction
Bone matrix can be arranged into what classifications?
- Compact bone
2. Trabecular bone
Define compact bone
Also known as dense or cortical bone, is extremely hard and compact with very little space
Bone mineral in compact bone is arranged into tight circles called osteons, with nerves and blood vessels passing through the center. Compact bone accts for 80% of the total bone mass
Define trabecular bone
Also known as spongy or cancellous bone, is porous and more like a network that allows nerves, blood vessels, and bone marrow to easily fill trabecular bone
Stress on trabecular bone causes it to create new and stronger networks, making it extremely adaptable
Accts for 20% of the total bone mass, it has a greater surface area than compact bone
What are the five main types of bone based on their shape?
- Long bones - bones that are longer than they are wide and made up of primarily compact bone (e.g. arm bones, leg bones, and phalanges)
- Short bones - cube-shaped with a thin layer of compact bone (e.g. wrist and ankle bones)
- Sesamoid bones - bones embedded in tendons. (e.g. patella and pisiform)
- Flat bones - thin and curved with parallel layers of compact bone. (e.g. sternum and bones of the skull)
- Irregular bones - bones that do no fit in any of the other categories. (e.g. vertebra and bones of the sinus)
What does collagen fibers allow bones to do?
The presence of collagen fibers allow bone to endure stretching forces
What does mineral salts allow bones to do?
Allow bones to endure compression forces
How is the bone construction similar to reinforced concrete?
Similar in that steel rebar allows concrete to resist strecthing forces, while the cement resists compression
Bone structure is somewhat similar to reinforced concrete that contains structural metal reinforcement rods or bars. These metal reinforcements are commonly called rebar. Protein strands make up the rebar of bone. Calcium and phosphorus mineral crystals deposited around the protein strands are somewhat like the concrete poured around the rebar in reinforced concrete. The protein strands provide the tensile strength that holds everything together and the minerals provide the solid structure. If bones were made only of protein, they would be too flexible. If bones were made solely from minerals, the skeleton would be too brittle.
What is the function of osteons?
Allows the bone to resist greater amounts of force
The bone construction does not resist what?
Does not tend to resist twisting forces, and in fact is the primary cause of bone fractures
What are the two main components of extracellular matrix?
Mineral salts and collagen
What types of force do collagen and bone mineral resist?
Bone mineral resist compression forces
Collagen fibers resist tension forces
What chemicals make up the organic portion of the bone extracellular matrix?
Made up of proteoglycans, water, minerals, and fibrous proteins
What chemicals make up the inorganic portion of the bone extracellular matrix?
Consists of hydroxapatites or minerals salts, primarily calcium phosphate