What do you call that part of the muscle that connects directly to the bone?

What do you call that part of the muscle that connects directly to the bone?

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When you open up a chicken leg or a clam and you remove the meat, there is this little part that is connected to the bone and is not easily scraped off.

What is this part called and what mechanism does it use to connect to the bone or the shell?

The tendon is the part of the muscle that connects directly to the bone.

A tendon (or sinew) is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae; all three are made of collagen. Ligaments join one bone to another bone; fasciae connect muscles to other muscles. Tendons and muscles work together to move bones.

The image was taken from the wikipedia link.

First prosthesis in the world with direct connection to bone, nerves and muscles

Thanks to the electrodes system a stable signal is obtained, which allows precise control like handling an egg without breaking. It also provides sensations as if it were a real hand.

The first prosthesis in the world that connects directly to the bone, nerves and muscles, allows the person to experience sensations, free mobility and is handled using the mind.

It was created by the Mexican Max Ortiz Catalan, who lives in Sweden, the device becomes an extension of the human body through osseointegration, this means that it connects directly to the bone via a titanium implant, and thanks to the neuronal and muscle binding interfaces a robust and intuitive control of the artificial hand is achieved, this way just by thinking about it is possible to move the limb.

The Mexican graduated from the Tecnológico de Monterrey says that Magnus, a patient with an arm amputated above the elbow, is the first person to use technology and, since 2013, it has allowed him to develop a normal working life, return to his activity as operator of heavy machinery on the border between Sweden and Finland, as well as manipulate an egg without breaking it.

The doctor in biomedical engineering Ortiz Catalan explains that thanks to the electrodes that are connected in muscles and nerves stable signals that allow precise control, such that the patient handling a small and delicate items without breaking it or throw it obtained, also provides sensations as his own hand and is protected from interference such as sensors in retail stores.

The research was conducted at Chalmers Technological University in Gothenburg, Sweden, in collaboration with the Sahlgrenska University Hospital, and the implant company called Integrum AB, which works with bone anchoring prosthetics.

The device consists of two parts, an implant and a prosthesis, the first part requires surgery in which a titanium piece is placed into the bone and a control system that connect electrodes to the muscles and nerves is installed.

The second corresponds to a removable prosthesis, maintaining a mechanical connection with the bone and an electrical connection with the implanted electrodes. This robotic component can be taken off, so the patient can get wet and have a bath.

About 400 people worldwide already have a titanium implant, but only two count with the system of electrodes implanted in nerves and muscles. It is expected that this year more than ten patients receive the neural control system.

New technology

Technology osseointegration puts an end to inflammation problems, chafing and discomfort that conventional prosthesis cause. "This one strongly presses the stump, it feels like having shoes half a size to small, which is not comfortable however, by having a direct connection to the bone and not having any components that disturb the skin, the use increases considerably, as well as the quality of life ."

In addition, by having a titanium implant allows the bone to grow around it and bind between them, which would not happen with other materials such as stainless steel which generates a reaction of encapsulation and creates mechanical instability.

The titanium implant to anchor the prosthesis to the bone is only available in Europe, Australia, Chile and the United States, but agreements are being sought to develop it in Mexico.

"We aim to make technology that people can use in their daily activities, and we would like it to become a standard treatment for every amputation, thus prices would fall," concludes Dr. Ortiz Catalan.

Scientists find common genes involved in muscle strength

For the first time, scientists have discovered common genetic factors that influence muscle strength. The discovery offers new insights into the biology of muscle strength and its role in age-related conditions such as bone frailty.

Share on Pinterest Researchers have recently found 16 new genetic loci that impact muscle strength.

The study, led by researchers at the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge in the United Kingdom, is published in the journal Nature Communications.

The authors explain that muscle strength, as measured by hand grip strength, is widely used as a clinical indicator of muscular fitness. It is also predictive of a number of health outcomes in older people.

For example, weaker hand grip strength is a known marker of frailty and bone fracture risk, and it has been linked to lower quality of life in older adults.

It is also known that people with higher hand grip strength are more likely to recover better following surgery for hip fracture in later life.

Also, studies that have followed people over many years have shown that grip strength can predict cardiovascular disease and premature death.

The researchers note, however, that it remains unclear whether lower muscle strength actually causes these adverse outcomes or whether it is an early sign of underlying disease.

For their study , the team carried out a large-scale genetic analysis on samples from 140,000 people taking part in the UK Biobank project and from a further 50,000 people in Australia, Denmark, the Netherlands, and the U.K., all of whom were taking part in eight other studies.

They also had data on the participants’ hand grip strength and demographic, biometric, and health outcome variables.

The genetic analysis identified that muscle strength is significantly linked to 16 locations on the human genome.

Some of the 16 locations, or “loci,” are situated within or near genes already known to be important to the biology of muscles.

These genes include ACTG1, which is related to skeletal muscle fibre structure and function, and three genes called PEX14, TGFA, and SYT1, which are all important for muscle cell communication with the nervous system.

Variants of three genes identified – namely, PEX14, LRPPRC, and KANSL1 – are also known to be involved in severe muscle conditions that are caused by a single faulty gene.

The researchers believe that the findings show that the gene variants behind some severe muscle conditions may also play a role in determining muscle strength differences among people generally.

Commenting on the findings, co-senior author Dr. Robert Scott, of the MRC Epidemiology Unit, says, “While we have long suspected a role for genetics in the variation in muscle strength, these findings give the first insights into some of the specific genetic variants that underpin variation in strength.

“These could be important steps towards identifying new treatments to prevent or treat muscle weakness.”

After establishing the link between the 16 genetic factors and muscle strength, the team then looked for clues that might show whether or not low muscle strength actually causes the health problems associated with it.

They found no evidence that reduced muscle strength directly raises risk of premature death or cardiovascular disease.

However, they did find evidence that higher muscle strength reduces risk of bone fracture.

Prof. Nick Wareham, another of the study’s senior authors and director of the MRC Epidemiology Unit, says that this finding highlights “the importance of muscle strength in the prevention of fractures and the complications which can often follow a fall.”

“ The very large number of individuals participating in UK Biobank provides a powerful resource for identifying genes involved in complex traits such as muscle strength, and helps us understand their underlying biology and its relevance to health.”

Co-first author Dan Wright, MRC Epidemiology Unit

Recti muscles

The eye has four recti muscles, all of which attach to the front half of the eye (anterior to the equator of the eye). These muscles are:

Each of the eye’s recti muscles originates from the common tendinous ring (sometimes referred to as the annular tendon or annulus of Zinn), This is a fibrous ring of connective tissue that surrounds the optic nerve where it connects to the orbit.

“Rectus” is the Latin word for “straight,” which indicates that the recti muscles attach directly from the orbit to the sclera of the eye.

Superior rectus muscle

The superior rectus muscle is found at the top of the eye and controls upward movement of the eye. Movement of the superior rectus muscle is controlled by the oculomotor nerve.

Medial rectus muscle

The medial rectus eye muscle attaches to the side of the eye closest to the nose and moves the eye inward. Movement of the medial rectus muscle is controlled by the oculomotor nerve.

Lateral rectus muscle

The lateral rectus eye muscle attaches to the side of the eye closest to the temple. This muscle is what allows the eye to move outward. Movement for the lateral rectus muscle is made possible by the abducens nerve.

Inferior rectus muscle

The inferior rectus eye muscle is located at the bottom part of the eye and allows the eye to move downward. This muscle’s movement is controlled by the oculomotor nerve.

The Muscular and Skeletal System of the Rat

Procedure: Skinning the Rat

You will carefully remove the skin of the rat to expose the muscles below. This task is best accomplished with scissors and forceps where the skin is gently lifted and snipped away from the muscles. You can start at the incision point where the latex was injected and continue toward the tail. Use the lines on the diagram to cut a similar pattern, avoiding the genital area. Gently peel the skin from the muscles, using scissors and a probe to tease away muscles that stick to the skin.

Muscles are attached to bones by connective tissue called tendons that adhere to spines, knobs, and ridges on bones. You will need to refer to the rat skeleton to determine where the muscles are attached to bones. The end attached to the bone that does not move during contraction is called the origin. The end of the muscle that attaches to the bone that does move is called the insertion. The movement caused by the contraction of the muscle is called the action. Muscles can be easily identified from one another by their shape and overlap.

Identify the following muscles:

1. Biceps brachii - located on the anterior surface of the humerus.
2. Triceps brachii - located on the sides and back of the upper arm.
3. Spinotrapezius - located across the dorsal thoracic region of the rat.
4. Latissimus dorsi - located posterior (and partially covered) by the spinotrapezius.
5. Biceps femoris - located on the side of the thigh, in two bundles
6. Tibialis Anterior - located on the front of the leg.
7. Gastrocnemius - located on lower leg, bulk of the calf muscle. Attaches to heel by the Achilles Tendon.
8. External Oblique - located on the sides of the abdomen.
9. Gluteus Maximus - located on the lower back and rear.
10. Pectoralis Major/Minor - located in chest

Pin the muscles listed above on a skinned rat.

Carefully tease away the biceps femoris and gastrocnemius to expose the 3 leg bones: Tibia, Fibula, and Femur and the small patella (kneecap). You can also see the ligaments around the knee that attach the bones of the lower leg to the femur and the achilles tendon which attaches the the gastrocnemius to the ankle.

Spine Structure and Function

Your spine, or backbone, is your body's central support structure. It connects different parts of your musculoskeletal system. Your spine helps you sit, stand, walk, twist and bend. Back injuries, spinal cord conditions and other problems can damage the spine and cause back pain.

What are the parts of the spine?

A healthy spine has three natural curves that make an S-shape. These curves absorb shocks to your body and protect your spine from injury. Many different parts make up your spine:

  • Vertebrae: The spine has 33 stacked vertebrae (small bones) that form the spinal canal. The spinal canal is a tunnel that houses the spinal cord and nerves, protecting them from injury. Most vertebrae move to allow for a range of motion. The lowest vertebrae (sacrum and coccyx) are fused together and don’t move.
  • Facet joints: These spinal joints have cartilage (a slippery connective tissue) that allows vertebrae to slide against each other. Facet joints let you twist and turn, and they provide flexibility and stability. These joints can develop arthritis and cause back pain or neck pain.
  • Intervertebral disks: These flat, round cushions sit between the vertebrae and act as the spine’s shock absorbers. Each disk has a soft, gel-like center (the nucleus pulposus) surrounded by a flexible outer ring (the annulus). Intervertebral disks are under constant pressure. A herniated disk can tear, allowing some of the nucleus’ gel substance to leak out. Herniated disks (also called bulging, slipped or ruptured disks) can be painful.
  • Spinal cord and nerves: The spinal cord is a column of nerves that travels through the spinal canal. The cord extends from the skull to the lower back. Thirty-one pairs of nerves branch out through vertebral openings (the neural foramen). These nerves carry messages between the brain and muscles.
  • Soft tissues: Ligaments connect the vertebrae to hold the spine in position. Muscles support the back and help you move. Tendons connect muscles to bone and aid movement.

What are the spine segments?

The 33 vertebrae make up five distinct spine segments. Starting at the neck and going down toward your buttocks (rear end), these segments include:

  • Cervical (neck): The top part of the spine has seven vertebrae (C1 to C7). These neck vertebrae allow you to turn, tilt and nod your head. The cervical spine makes an inward C-shape called a lordotic curve.
  • Thoracic (middle back): The chest or thoracic part of the spine has 12 vertebrae (T1 to T12). Your ribs attach to the thoracic spine. This section of the spine bends out slightly to make a backward C-shape called the kyphotic curve.
  • Lumbar (lower back): Five vertebrae (L1 to L5) make up the lower part of the spine. Your lumbar spine supports the upper parts of the spine. It connects to the pelvis and bears most of your body’s weight, as well as the stress of lifting and carrying items. Many back problems occur in the lumbar spine. The lumbar spine bends inward to create a C-shaped lordotic curve.
  • Sacrum: This triangle-shaped bone connects to the hips. The five sacral vertebrae (S1 to S5) fuse as a baby develops in the womb, which means they don’t move. The sacrum and hip bones form a ring called the pelvic girdle.
  • Coccyx (tailbone): Four fused vertebrae make up this small piece of bone found at the bottom of the spine. Pelvic floor muscles and ligaments attach to the coccyx.

What conditions and disorders affect the spine?

Up to 80% of Americans experience back pain at some point. Vertebrae and disks can wear down with age, causing pain. Other conditions that affect spine health include:

  • Arthritic conditions, such as ankylosing spondylitis (AS). . such as spina bifida. (jagged edges on vertebrae that put pressure on the spinal cord and nerves).
  • Curvatures of the spine (scoliosis and kyphosis).
  • Neuromuscular diseases, such as amyotrophic lateral sclerosis (ALS).
  • Nerve injuries, including spinal stenosis, sciatica and pinched nerves. (weak bones). , including spinal fractures, herniated disks and paralysis. and cancer.
  • Spine infections like meningitis and osteomyelitis.

How can I keep my spine healthy?

Strong back muscles can protect your spine and prevent back problems. Try to do back-strengthening and stretching exercises at least twice a week. Exercises like planks strengthen the core (abdominal, side and back muscles) to give your spine more support. Other protective measures include:

  • Bend your knees and keep your back straight when lifting items.
  • Lose weight, if needed (excess weight strains your back).
  • Maintain good posture.

When should I call the doctor?

You should call your healthcare provider if you experience:

  • Back pain with fever.
  • Bowel or bladder control issues.
  • Leg weakness or pain that moves from your back down your legs.
  • Pain that worsens, causes nausea or sleeplessness or interferes with daily activities.

A note from Cleveland Clinic

Your spine is a complex structure of small bones (vertebrae), cushioning disks, nerves, joints, ligaments and muscles. This part of your anatomy is susceptible to injury, arthritis, herniated disks, pinched nerves and other problems. Back pain can affect your ability to enjoy life. Your healthcare provider can help ease back pain and offer suggestions to strengthen the muscles that support your back and prevent back injuries.

Last reviewed by a Cleveland Clinic medical professional on 12/07/2020.


  • American Academy of Orthopaedic Surgeons. Spine Basics. Accessed 12/08/2020.
  • American Association of Neurological Surgeons. Anatomy of the Spine and Peripheral Nervous System. Accessed 12/08/2020.
  • American Chiropractic Association. Back Pain Facts and Statistics. Accessed 12/08/2020.
  • Merck Manual. Spinal Cord. Accessed 12/08/2020.
  • U.S. Department of Health and Human Services. Office of Disease Prevention and Health Promotion. Prevent Back Pain. Accessed 12/08/2020.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Muscular System Function

The main function of the skeletal muscle system is movement. However, muscular system organs provide protection to other organs 14. For example, your abdominal muscles protect internal organs such as your intestines and bladder. Skeletal muscles also help maintain your body temperature when you get cold by shivering.

Muscles work together to produce movement. The main muscle that is performing a movement is called the agonist, or prime mover. For example, when you bend your elbow, your biceps muscle is the agonist. However, the biceps does not work alone. Synergists, or helping muscles, such as the brachialis and brachioradialis also bend the elbow.

To allow your elbow to bend, muscles on the opposite side of your elbow have to relax. The opposing muscle group is called the antagonist. The triceps muscle on the back of your arm straightens your elbow, making it the antagonist during elbow flexion.

Foot Tendon Tears

To properly diagnose a foot injury, you may need to see an orthopedic specialist who is trained to detect and treat foot and ankle injuries. During the exam, the doctor will:

  • Ask about the injury, ask how your foot feels now, and when it hurts most
  • Examine your foot and ask you to move it in certain ways
  • Recommend imaging tests such as an:
    • X-ray to check for broken bones and look for other damage
    • MRI or CT scan if there is any question about which part of the foot is injured or the severity of the injury


    Treatment tendon tear in the foot will depend on how serious the tear is and your overall health, but may include any of the following:

    • Rest. You may need to take a break from any activities that put pressure on the injured tendon.
    • Ice. Cold packs may help to reduce pain and swelling. Ice the injury right after it happens, and then 3 or 4 times a day while it is healing. Put ice in a towel or cloth and ice for only 20 minutes at a time. Don’t put ice directly on your skin. When you start back to your usual activities, it may help to ice the area that was injured for 20 minutes after activity to prevent swelling.
    • Nonsteroidal anti-inflammatory medicine (NSAID). NSAIDs like ibuprofen can reduce pain and swelling after the injury. Ask your doctor about the appropriate dose for your injury and how long you should take them.
    • Brace or cast. Your doctor may recommend you use a brace, cast, or boot to support your foot and keep it still while it is healing.
    • Orthotics. An orthotic is an insert that goes in your shoes to support your foot and help you use it the right way. Sometimes a tendon injury changes the shape of your foot, which may require special support.
    • Steroid (cortisone) injections. Cortisone shots can reduce inflammation and pain that come with a tendon injury.. Your doctor will help you decide if this is the right treatment for you.
    • Exercise and physical therapy. Exercises that stretch and strengthen your muscles and tendons may help. A physical therapist will teach you the correct way to do these exercises and coach you as you do them when you first start your exercise program.
    • Surgery. If your tendon is ruptured or your pain and swelling doesn’t go away, surgery may be recommended to repair or replace a tendon. Surgery may also be done to remove any inflamed tissue around the tendon or to change the muscle or bone that the tendon attaches to.


    It’s not always possible to prevent injuries. But you can lower your risk of a foot tendon tear by taking care of the muscles that tendons attach to. Know your limits and don’t push your muscles to do what they are not ready to do.

    If you have a foot tendon injury, you can prevent further damage and future injuries by getting the right treatment.

    #2: Muscles in Motion

    Use your sense of touch to find out which muscles you use when doing different activities. For this project you may want a friend or family member to be your helper.

    1. Hold one arm out in front of you, with your palm facing up. Make a fist, and slowly bring your arm up at the elbow, then bend it back down. Which arm muscles do you think you are using?
    2. Do the first step again, bringing your arm slowly back and forth, but this time put your other hand on your arm just above the elbow. Can you feel your muscles moving?
    3. What muscles would you use to catch a baseball? How about throwing a baseball? With your helper, come up with different sports (Basketball, Tennis, Soccer, etc.). What muscles do you think athletes in these sports use the most? Have your helper act out what an athlete does for a particular sport. For example, for soccer, you might jump, kick, and run. What leg muscles does this use? How about arm muscles?
    4. Try making a slow kicking motion (while sitting in a chair, so you don’t fall down), while your partner feels your leg muscles to see which ones are being used. You could do the same thing with different activities: catching a baseball, catching a football, throwing a frisbee, swinging a golf club, skiing, etc. Act out as many different activities as you can think of, to see what muscles they would use. Take turns with your helper acting out different sports in slow motion.

    What Happened:

    You use various muscles in your body throughout the day. Muscles are what allow you to move. Even very basic things that you do often require you to use your muscles – getting out of bed, eating, walking, and playing all use muscles! When you experimented, you probably found that certain parts of your arms and legs helped you do certain things, like throw or catch a ball, kick a ball, run, etc. Can you think of some other things you do that use those same muscles? How about jumping, skipping, doing cartwheels or summersaults, playing tag or leap-frog, helping set the table or wash the dishes, brushing your teeth, and putting away your toys?

    To learn more about some of the different muscles in your body, check out this worksheet. See if you can name the muscles you used for the different activities you tried above.

    Anatomy and Physiology: The Parts of a Bone

    Most people envision bone as being uniformly solid, but nothing could be farther from the truth. For one thing, as you will see later in this section, bones come in many different shapes?long, short, flat, irregular, wormian, and sesamoid?which have much in common, despite their differences. A typical bone can be broken down into multiple parts, each with a particular function:

    • Epiphysis. This part is at the extreme ends of the bone (epi = above), where joints (articulations) form.
    • Articular cartilage. A layer of hyaline cartilage, called articular cartilage, exists to reduce friction and absorb shock at synovial joints (see The Joints).
    • Diaphysis. The shaft of a long bone, which is the direction at which the bone can withstand the most stress.
    • Metaphysis. The metaphysis is the place where the diaphysis meets the epiphysis. This is where major bone growth occurs, as well as where blood enters the bone.
    • Periosteum. A thin membrane that covers the outside of the bone, where tendons and ligaments attach to the bone. The outer fibrous layer is where blood vessels, nerves, and lymphatics connect to the bone, while the inner osteogenic layer has bone cells necessary for the growth and repair of bone.
    • Medullary (or marrow) cavity. This hollow cavity, in the diaphysis, is for the storage of yellow marrow.
    • Endosteum. This membrane lines the medullary cavity, and contains osteoprogenitor cells (unspecialized bone cells, as you will soon see).

    Up, Down, and Middle

    As you can see in Figure 5.1, the shaft of a long bone is called the diaphysis. The central, fat-storing marrow cavity is found inside the diaphysis. At each end of the bone, at the site of the synovial joint, is an area called epiphysis. At the juncture between the two is an area called the metaphysis.

    Figure 5.1 The many parts of a typical long bone. The example shown here is a femur. (2003

    The Big Picture

    A certain pituitary disorder involves the overproduction of human growth hormone, or hGH. In a child, this results in gigantism, whereas too little hGH results in one form of dwarfism (other forms are caused by either extreme malnutrition or, in the case of achondroplasia, a dominant gene). As an adult, due to the formation of the epiphyseal line, the bones of the face, hands, and feet will enlarge dramatically. This condition, which is seen in certain movie villains, is called acromegaly.

    Remember that organs, including bones, need three connections: blood vessels (both arteries and veins), lymphatics, and nerves. These structures enter the bone through little holes called foramina. A hole specifically for blood vessels is called a nutrient foramen (the singular form of foramina). Any student can tell if a skeleton is real by simply looking for foramina around the metaphysis. Another clue is the weight: Real bones are lighter than solid models, due to the openings for red and yellow marrow.

    Beyond the entering and exiting nerves and vessels, the metaphysis is also the location of the epiphyseal plates, which are the primary growth centers of a long bone. There are four zones in the epiphyseal plate. The zone of resting cartilage is not involved in growth, but it does anchor the plate to the rest of the bone. The zone of proliferating cartilage and zone of hypertrophic cartilage are both involved in producing chondrocytes (cartilage cells), but the latter zone is where maturation of the cells occurs. The last zone, where the bone actually forms, is known as the zone of calcified cartilage.

    As we age, the epiphyseal plates, which are less dense than bone and show up darker on an X-ray, will ossify (turn to bone), at which point they will appear as a light line (called the epiphyseal line). This marks the end of a bone's ability to grow longer this ossification is usually complete by the early to mid twenties (although the sternum doesn't finish until after 30). The facial bones, and often the hands and feet, however, do not stop growing, which explains why a young Jimmy Stewart looked very different than he did as an old man.

    The Harder They Come

    Compact bone is notable for the wide spacing of the cells within a hard crystal matrix (see Figure 5.2). You may remember that both wide spacing and a matrix were characteristics of connective tissue. The main feature of compact bone is its strength. It provides protection for places outside a soft structure, such as in the flat bones of the skull. Compact bone also supports the stress placed on it. In a long bone, the stress is best absorbed along the longitudinal axis of the diaphysis. This arrangement is great for a bone like the femur, which absorbs stress in that direction, but the same cannot be said for the clavicle, which can be easily fractured if it receives a downward blow perpendicular to the diaphysis.

    Microscopically, compact (or dense) bone is distinguished by its arrangement of osteocytes (bone cells) in concentric circles of matrix. Just as people settle around sources of water, these rings, or concentric lamellae, are arranged around a central haversian canal, which holds blood vessels. The combination of the concentric lamellae and the haversian canal is called an osteon, or haversian system. In addition to the haversian canal, there are perpendicular ones called perforating canals that connect haversian canals, and help to provide blood not only to the deeper haversian systems, but also to the marrow cavity.

    The osteocytes look a little like ants because of the arrangement of little canals called canaliculi around each cell these canaliculi, whose name always makes me think of an Italian dessert, are where the interstitial fluid is found. Canaliculi extend outward in every direction from the lacuna, which is the space where the osteocyte is found.

    Figure 5.2 This is a diagram of haversian systems in compact bone. Note the organization of the bone is based on the location of blood vessels. (LifeART1989-2001, Lippincott Williams & Wilkins)

    Not Just For Mopping Up Spills

    Spongy or cancellous bone is very different in appearance. Rather than rigid concentric systems, spongy bone looks, well, spongy. The appearance is due to an irregular collection of overlapping and interconnected spokes called trabeculae (refer to Figure 5.2). To understand the function of spongy bone, note that it appears most commonly in the epiphysis, just under a protective compact layer. The compact layer provides firm attachment for that articular cartilage, both of which help to protect from the friction found in every synovial joint.

    So why the spongy part? In terms of stress at the joint, imagine jumping in the air and landing hard on your feet while keeping your legs straight a great deal of stress will be felt not only in your knees, but also where your femur articulates with your pelvis, not to mention in your back. You can easily reduce the stress by bending your knees and ankles such bending absorbs the stress of the impact. Now do you know the reason for spongy bone? That's right, to absorb some of the shock of impact at synovial joints.

    The screwy multidirectional trabeculae make it possible to absorb stress from multiple directions. In addition, the spaces between the trabeculae make spongy bone much lighter, thus making the skeleton as a whole much lighter. These spaces serve another purpose they are filled with red bone marrow, the site of hemopoiesis.

    Excerpted from The Complete Idiot's Guide to Anatomy and Physiology 2004 by Michael J. Vieira Lazaroff. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

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