Category Zoology

Which are the strongest muscles?

                            Although it is not very big, the strongest muscle in the body, for its weight, is the masseter muscle in the jaw. It allows you to have a powerful biting action. The largest muscle of all is the gluteus maximus (a Latin name, like many medical terms). It runs from the buttocks down the back of the thigh. The longest muscle is the sartorius, which runs from the hip bone, or pelvis, right down to just below the knee.

What is muscle tone?

Muscles need constant work to keep them strong and healthy. When two muscles work against each other, they will always be slightly contracted and under tension. This is called muscle tone. The fitter you are, more strongly these muscles will pull against one another, even while you are relaxed.

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What job do muscles do?

                      Muscles are needed for all body movements. Muscles move the bones, pulling them into position as they move about their joints. Some muscles just move soft parts of the body, for example, the face muscles that allow you to smile.

                      You can control many of your movements by using voluntary muscles. Other muscles, called involuntary muscles, work automatically to maintain the body. The heart, for instance, beats without your being aware of it. The muscles that squeeze your food along inside the intestines also work automatically.

How are muscles joined to bone?

                     Muscles are attached to bone by long ropy strands called tendons, which are made of collagen. You can feel these tendons on the inside of your wrist when you flex your hand and fingers.

How are muscles constructed?

                    Muscles are built up from millions of thread-like cells called muscle fibres. These fibres are gathered into bunches. Nerves instruct the muscle fibres when to shorten, or contract, causing the whole muscle to become shorter in length. The shortened muscle then pulls on the tendon and the bone to which it is joined.

Can joints wear out?

                  Joints can become diseased or wear out after a lifetime of use. When this happens, the cartilage or the fluid inside the joint gradually disappears. The joint becomes hard to move and may be very painful.

How many joints do I have?

                      The human body has more than 100 joints. Some joints move like a simple hinge, such as those in the elbows and knees. Other joints move in all directions, such as the shoulder joint or the base of the thumb. Joints in the spine allow only a small amount of movement between the vertebrae that protect the spinal cord. Joints such as the bones of the skull and those joining the two sides of the pelvis are locked firmly together so they do not move at all.

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What are joints?

                        A joint is the point where two or more bones come together. Joints can be fixed, such as those that hold together the rounded part of the skull, or they can allow movement, such as your knees and elbows. Straps of tough flexible material called ligament hold together the bones in a joint.

 How do joints work?

                   The ends of most bones are covered with tough rubbery cartilage, which cushions them from impact as we move.

                   Many joints are lubricated with an oily liquid called synovial fluid so they can bend freely. Synovial fluid is held in a bladder between the layers of cartilage on the ends of the bone. These lubricated joints can move freely and without friction.

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Are bones alive?

                Bones consist of a solid stony material that is laid down in layers by living bone cells. New bone is constantly being reabsorbed and then replaced, to keep it healthy. The surface of a bone is covered by a skin that is full of nerves, so it hurts when you bruise or break a bone. Inside the bone are blood vessels and marrow, a soft material in which new blood cells are produced. When people get old, their bones may become very spongy and weak, and so they are more prone to breakage.

How can bones heal themselves after a break?

                     Bones are alive, and so the bone cells can gradually replace and repair the solid bone when it is broken. The damaged material is gradually absorbed back into the body, and the bone cells secrete more hard bone. This eventually builds up into a thickened area on the repaired bone, which is actually stronger than the original bone.

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What are bones made of?

                          Bones are made of hard minerals that are supported by tough fibres called collagen. Most of the substance of a bone is made of a stony material called calcium phosphate. It is a hard but brittle material. The collagen strands reinforce this brittle material to prevent it from breaking easily.

Are bones alive?

Bones consist of a solid stony material that is laid down in layers by living bone cells. New bone is constantly being reabsorbed and then replaced, to keep it healthy. The surface of a bone is covered by a skin that is full of nerves, so it hurts when you bruise or break a bone. Inside the bone are blood vessels and marrow, a soft material in which new blood cells are produced. When people get old, their bones may become very spongy and weak, and so they are more prone to breakage.