Angila: Unit 3 Review #2

Unit 3 Compendium Review #2
-Bones, bone tissue, and calcium
-Movement across joints
-Muscle cells, contraction and calcium

Bones, bone tissue and calcium
There are 206 bones in the human adult body that make up the skeletal system. The skeletal system is very important because it provides us with support allowing us to move and it also protects parts of the body for example the brain, spinal cord and heart and lungs. The skeletal system has other important functions as well; it produces blood cells within the red bone marrow and stores minerals and fat.
There are two main parts that make up bone, compact bone and spongy bone. Compact bone makes up the outer shell of the long bone and surrounds the medullar cavity where yellow bone marrow is contained. Fat is stored within yellow bone marrow. Blood vessels exchange nutrients and wastes with bone cells and are located in the bone marrow and throughout compact bone. Spongy bone is located at the ends and throughout bones, and even though it is lighter than compact bone it still provides support and strength. Spongy bone is a matrix of thin plates dispersed unequally leaving spaces where red bone marrow exists. Red bone marrow is a tissue that produces all types of blood cells needed in the body. Besides yellow and red bone marrow tissue there is one more important tissue related to bones which is fibrous connective tissue. This tissue makes up ligaments and tendons. Ligaments connect bone to bone while tendons connect bone to muscles at joints. Bones play a huge role in regulating calcium levels in the blood and is referred to as bone recycling. When blood calcium levels rise the excess is stored in bones and when calcium levels decrease below normal calcium is removed from bones. If too much calcium is removed from the bones the development of weak bones occurs called osteoporosis. (long bone anatomy shown below)

Movement across joints

While the skeletal system is made up of bones it also has many joints connecting bones and muscle together. Joints allow movement in the body with some moving more freely than others and some not moving at all. Sutures are immovable fibrous joints located between cranial bones. There are two main classes of joints Cartilaginous joints which are slightly movable and synovial joints that are freely movable. Cartilaginous joints connect the ribs of the sternum together by hyaline cartilage and join the vertebrae with fibrocartilage. (catilaginous joint)

Cartilage is gel-like matrix composed of collagenous and elastic fibers. It is not as strong as bone, has no blood vessels, and has no nerves making it great for padding between bones and in joints but takes longer to heal if damaged. Depending on how the matrix of fibers are arrange determines the type of cartilage is present. Hyaline cartilage is flexible but firm. Fibrocartilage is stronger and can with stand tension and pressure; located in the knee and between the vertebrae. Lastly elastic cartilage is highly flexible and found in the ear as well as other places. With the understanding of cartilage I would like to move onto the second type of joints synovial joints. Synovial joints have a cavity of synovial fluid which is a lubricant for the joint. Ligaments support the joint and give it strength by holding the two bones together. Cartilage also plays a large role in these joints providing as a shock absorber and stability. (Synovial joint anatomy)There are different types of synovial joints in the body; hinge joints and ball-and-socket joints. The knee and elbow are examples of hinge joints because they permit movement in one direction only like a hinge. Unlike ball-and-socket joints which have a rotational movement like that of the hips, ankle and shoulders. The movement capable of synovial joints are as follows;1st illustration shows:

Flexion, joint angle decreases

Extensoin, joint angle increases

2nd illustration shows:

Adduction, body part moves towards midline

Abduction, body part moves away from midline

3rd illustration shows:

Rotation, body part moves around its own axis

Circumduction, body part moves so that a cone shape is outlined

4th illustration shows:

Inversion, sole of foot turns inwards

Eversion, sole of foot turns outward

Muscle cells, contraction and calcium

We learned bones provide support, among other things, and joints connect bones together allowing movement now we are going to talk about what makes this movement possible. Muscle cells called muscle fibers combine together making muscle which makes movement possible throughout the body. There are three types of muscle tissue: smooth, cardiac, and skeletal. Smooth or visceral muscle is involuntary, automatic not controlled by the mind, with a single nuclei for each spindle-shaped cells. Smooth muscle lines blood vessels and the digestive tract. Cardiac muscle is only found in the heart and has characteristics from both smooth and skeletal. Its has branching striated cells like skeletal but with only a single nuclei and it too in involuntary like smooth. Skeletal muscle is voluntary and when it contracts body parts move. This is because skeletal muscle is attached to bones by tendons. Skeletal muscle fibers are cylindrical and long and with multiple nuclei in the striated cells. (3 muscle tissues)Skeletal muscles have many functions including providing support for the body, making bones move, protect internal organs and support joints. and aiding in keeping a constant body temperature. Skeletal muscles help keep a constant body temperature because when it contracts it is using ATP (energy) which when it breaks down to be used it releases heat that is dispersed throughout the body.
Along with ATP calcium is important to muscle contraction. Calcium is stored within muscle fiber (cells) in the sarcoplasmic reticulum. When muscles are motivated to move impulses travel though T tubule which causes calcium (Ca2+ ) to be released from the sarcoplasmic reticulum. The Ca2+ that is released combines with troponin, protein apart of actin filament, causing the tropomyosin (another protein) threads to shift their position. Resulting in myosin binding sites. This is where ATP in the form of ADP + are bound to myosin as a myosin head and attaches to actin. A power stroke takes place moving the actin fiber resulting in muscle contraction. This procedure is repeated until muscle is contracted to the desired position.