In this section we learned about:

*calcium and muscle
*calcium and bone
*movement across the joints




The skeletal system is made up of 206 bones, cartilage and fibrous connective tissue. The skeletal system has many different purposes. Some of these are to support the body, protect our organs, allow flexiblity and movement with the help of muscle, it produces red blood cells, and stores fats and minerals.




Cartilage is a connective tissue that is not as strong as bone. It contains collagenous and elastic fibers. Cartilage has no nerves or blood vessels. Therefore making it difficult to heal if injured. There are three different types of cartilage:

Hyaline cartilage - firm and somewhat flexible, it's found at the end of long bones, in the nose, at the end of ribs and in the larynx and trachea

Fibrocartilage - stronger than hyaline cartilage, able to withstand tension and pressure, found in the knee and the vertebrae discs

Elastic cartilage - more flexible than hyaline, found in the ears and epiglottis



Connective Tissues is one of the four types of tissues in the body. Connective tissue is involved in support and structure. There are four types of connective tissue.

Areolar (loose) connective tissue - holds organs and the the top layer of skin together

Adipose tissue - is used for cushioning and energy

Fibrous tissue - forms ligaments and tendons

Reticular tissue - form a soft skeleton to support the lymphoid organs



Muscle



The human body has over 600 muscles in their body. There are three different types of muscle tissue:



Smooth muscle - spindle shaped cells with single nucleus, usually aranged in parallel lines, forming sheets, contraction of smooth muscle is involuntary, does not fatigue easily. They are found in the wall of the bladder, digestive tract, uterus, blood vessels and other internal organs.



Skeletal muscle - tubular fibers that are mulitnucleated, and striated. They run the length of the bone. Movement is voluntary such as the legs and arms.



Cardiac muscle - forms the heart wall and has feature of both the smooth muscle and the skeletal muscle. Fibers are generally uninucleated, striated, tubular, and branched allowing it to interlock at intercalated disks. Muscule contraction is involuntary and rhythmical.


Calcium and Muscle

When muscle fibers are stimulated by axons in the motor neurons to contract the vesicles are filled with the neurotransmitter acetylcholine (ACH). When the nerve impulse arrives at the axon terminal, ach is released. When ach is released it quickly binds to receptors in the sarcolemma. Which then generated impulses that spread over the sacrolemma and down T tubules to the sarcoplasmic reticulum. The release of calcium causes the sarcomere to contract. When calcium ions are released from the sarcoplasmic reticulum, it combines with tropomin causing the tropomyosin threads to shift their position, exposing the binding sites and allowing the myosin to bind to actin.

Calcium and Bone

Calcium plays and important role in the development and maintenance of our bone tissue. Bone tissue is constanlty regenerating itself. Without enough calcium in our body our bones start to show weaknesses. A major condition caused by this is osteoporosis. During osteoporosis men may lose up to 25% of their bone mass and women may lose up to 35% of theirs. Thus leaving them vulnerable to broken bones. While osteoporosis can't be prevented by making sure you are taking in an adequate amount of calcium you can help delay the process.

Joint Movement

Thanks to out joints we are able to bend, twist, turn, wave, rotate, etc the different areas of our body.

The most commonly known joint are the hinge joint and the ball and socket joint.



The hinge joint allows movement to take place in a certain spot. Such as our elbows, knees, wrists, etc. It permits only one type of movement and that is an forward and backward motion.

The ball and socket joint allows us to move our limbs in a circular motion. Such as in our shoulders and hips.


Works Sited:

http://www.polychondritis.com/connectivetissue/Cartilage/WhatisCartilage.html

http://en.wikipedia.org/wiki/Connective_tissue

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=DMUS,DMUS:2006-49,DMUS:en&q=pictures+muscles

http://www.uoguelph.ca/zoology/devobio/210labs/muscle1.html

Mader Human Biology 10e