Reviewed by: KidsHealth Medical Experts. Larger text size Large text size Regular text size. Bones are made up of two types of bone tissues: Compact bone is the solid, hard outside part of the bone.
It looks like ivory and is extremely strong. Holes and channels run through it, carrying blood vessels and nerves. Cancellous pronounced: KAN-suh-lus bone , which looks like a sponge, is inside compact bone. It is made up of a mesh-like network of tiny pieces of bone called trabeculae pronounced: truh-BEH-kyoo-lee.
This is where bone marrow is found. How Do Bones Grow? Bone contains three types of cells: osteoblasts pronounced: AHS-tee-uh-blastz , which make new bone and help repair damage osteocytes pronounced: AHS-tee-o-sites , mature bone cells which help continue new born formation osteoclasts pronounced: AHS-tee-o-klasts , which break down bone and help to sculpt and shape it What Are Muscles and What Do They Do? Humans have three different kinds of muscle: Skeletal muscle is attached by cord-like tendons to bone, such as in the legs, arms, and face.
Skeletal muscles are called striated pronounced: STRY-ay-ted because they are made up of fibers that have horizontal stripes when viewed under a microscope. These muscles help hold the skeleton together, give the body shape, and help it with everyday movements known as voluntary muscles because you can control their movement. They can contract shorten or tighten quickly and powerfully, but they tire easily. Smooth, or involuntary, muscle is also made of fibers, but this type of muscle looks smooth, not striated.
We can't consciously control our smooth muscles; rather, they're controlled by the nervous system automatically which is why they're also called involuntary. Examples of smooth muscles are the walls of the stomach and intestines, which help break up food and move it through the digestive system. Smooth muscle is also found in the walls of blood vessels, where it squeezes the stream of blood flowing through the vessels to help maintain blood pressure.
Smooth muscles take longer to contract than skeletal muscles do, but they can stay contracted for a long time because they don't tire easily. Cardiac muscle is found in the heart. The walls of the heart's chambers are composed almost entirely of muscle fibers. Six Types of Synovial Joints : Image demonstrating the six different types of synovial joints.
Learning Objectives Identify the different types of synovial joints. Key Points Synovial joints achieve movement at the point of contact of the articulating bones. Synovial joints allow bones to slide past each other or to rotate around each other. This produces movements called abduction away , adduction towards , extension open , flexion close , and rotation. Subcutaneous bursae prevent friction between the skin and an underlying bone, submuscular bursae protect muscles from rubbing against a bone or another muscle, and a subtendinous bursa prevents friction between bone and a muscle tendon.
Tendon sheaths contain a lubricating fluid and surround tendons to allow for smooth movement of the tendon as it crosses a joint. Based on the shape of the articulating bone surfaces and the types of movement allowed, synovial joints are classified into six types.
At a pivot joint, one bone is held within a ring by a ligament and its articulation with a second bone. Pivot joints only allow for rotation around a single axis.
These are found at the articulation between the C1 atlas and the dens of the C2 axis vertebrae, which provides the side-to-side rotation of the head, or at the proximal radioulnar joint between the head of the radius and the radial notch of the ulna, which allows for rotation of the radius during forearm movements. Hinge joints, such as at the elbow, knee, ankle, or interphalangeal joints between phalanx bones of the fingers and toes, allow only for bending and straightening of the joint.
Pivot and hinge joints are functionally classified as uniaxial joints. Condyloid joints are found where the shallow depression of one bone receives a rounded bony area formed by one or two bones.
Condyloid joints are found at the base of the fingers metacarpophalangeal joints and at the wrist radiocarpal joint. At a saddle joint, the articulating bones fit together like a rider and a saddle. An example is the first carpometacarpal joint located at the base of the thumb. Both condyloid and saddle joints are functionally classified as biaxial joints. Plane joints are formed between the small, flattened surfaces of adjacent bones. These joints allow the bones to slide or rotate against each other, but the range of motion is usually slight and tightly limited by ligaments or surrounding bones.
This type of joint is found between the articular processes of adjacent vertebrae, at the acromioclavicular joint, or at the intercarpal joints of the hand and intertarsal joints of the foot. Ball-and-socket joints, in which the rounded head of a bone fits into a large depression or socket, are found at the shoulder and hip joints.
Both plane and ball-and-sockets joints are classified functionally as multiaxial joints. However, ball-and-socket joints allow for large movements, while the motions between bones at a plane joint are small. Which type of synovial joint allows for the widest ranges of motion? Visit this website to read about a patient who arrives at the hospital with joint pain and weakness in his legs. Gout is due to the accumulation of uric acid crystals in the body.
Usually these accumulate within joints, causing joint pain. This patient also had crystals that accumulated in the space next to his spinal cord, thus compressing the spinal cord and causing muscle weakness.
The most common cause of hip disability is osteoarthritis, a chronic disease in which the articular cartilage of the joint wears away, resulting in severe hip pain and stiffness. The immune system malfunctions and attacks healthy cells in the lining of your joints. This causes inflammation and pain in the joints and surrounding tissues.
Skip to content Learning Objectives By the end of this section, you will be able to: Describe the characteristic features for synovial joints and give examples Describe the structural features and functional properties of a synovial joint Discuss the function of additional structures associated with synovial joints Compare the six types of synovial joints Name an example of each of the six types of synovial joints and describe its functional properties.
Homeostatic Imbalances — Bursitis. Bursitis is the inflammation of a bursa near a joint. This will cause pain, swelling, or tenderness of the bursa and surrounding area, and may also result in joint stiffness. Bursitis is most commonly associated with the bursae found at or near the shoulder, hip, knee, or elbow joints.
At the shoulder, subacromial bursitis may occur in the bursa that separates the acromion of the scapula from the tendon of a shoulder muscle as it passes deep to the acromion. In the hip region, trochanteric bursitis can occur in the bursa that overlies the greater trochanter of the femur, just below the lateral side of the hip. Ischial bursitis occurs in the bursa that separates the skin from the ischial tuberosity of the pelvis, the bony structure that is weight bearing when sitting.
At the elbow, olecranon bursitis is inflammation of the bursa between the skin and olecranon process of the ulna. External Website Watch this video to see an animation of synovial joints in action. Aging and the…Joints. Arthritis is a common disorder of synovial joints that involves inflammation of the joint. This often results in significant joint pain, along with swelling, stiffness, and reduced joint mobility.
There are more than different forms of arthritis. Arthritis may arise from aging, damage to the articular cartilage, autoimmune diseases, bacterial or viral infections, or unknown probably genetic causes. External Website Visit this website to learn about a patient who arrives at the hospital with joint pain and weakness in his legs.
External Website Watch this animation to observe hip replacement surgery total hip arthroplasty , which can be used to alleviate the pain and loss of joint mobility associated with osteoarthritis of the hip joint. External Website Watch this video to learn about the symptoms and treatments for rheumatoid arthritis. Chapter Review Synovial joints are the most common type of joints in the body.
Interactive Link Questions Watch this video to see an animation of synovial joints in action. Review Questions. Exercises 1. Describe the characteristic structures found at all synovial joints. Describe the structures that provide direct and indirect support for a synovial joint.
Moving the forearm upward at the elbow or moving the wrist to move the hand toward the forearm are examples of flexion. Extension is the opposite of flexion in that the angle between the bones of a joint increases. Straightening a limb after flexion is an example of extension. Extension past the regular anatomical position is referred to as hyperextension. This includes moving the neck back to look upward, or bending the wrist so that the hand moves away from the forearm.
Abduction occurs when a bone moves away from the midline of the body. Examples of abduction are moving the arms or legs laterally to lift them straight out to the side. Adduction is the movement of a bone toward the midline of the body. Movement of the limbs inward after abduction is an example of adduction. Circumduction is the movement of a limb in a circular motion, as in moving the arm in a circular motion. Rotational movement is the movement of a bone as it rotates around its longitudinal axis.
Rotation can be toward the midline of the body, which is referred to as medial rotation , or away from the midline of the body, which is referred to as lateral rotation. Movement of the head from side to side is an example of rotation.
Some movements that cannot be classified as gliding, angular, or rotational are called special movements. Inversion involves the soles of the feet moving inward, toward the midline of the body. Eversion is the opposite of inversion, movement of the sole of the foot outward, away from the midline of the body. Protraction is the anterior movement of a bone in the horizontal plane. Retraction occurs as a joint moves back into position after protraction.
Protraction and retraction can be seen in the movement of the mandible as the jaw is thrust outwards and then back inwards. Elevation is the movement of a bone upward, such as when the shoulders are shrugged, lifting the scapulae. Depression is the opposite of elevation—movement downward of a bone, such as after the shoulders are shrugged and the scapulae return to their normal position from an elevated position.
Dorsiflexion is a bending at the ankle such that the toes are lifted toward the knee. Plantar flexion is a bending at the ankle when the heel is lifted, such as when standing on the toes. Supination is the movement of the radius and ulna bones of the forearm so that the palm faces forward.
Pronation is the opposite movement, in which the palm faces backward. Opposition is the movement of the thumb toward the fingers of the same hand, making it possible to grasp and hold objects. Synovial joints are further classified into six different categories on the basis of the shape and structure of the joint. The shape of the joint affects the type of movement permitted by the joint Figure These joints can be described as planar, hinge, pivot, condyloid, saddle, or ball-and-socket joints.
Planar joints have bones with articulating surfaces that are flat or slightly curved faces. These joints allow for gliding movements, and so the joints are sometimes referred to as gliding joints. The range of motion is limited in these joints and does not involve rotation.
Planar joints are found in the carpal bones in the hand and the tarsal bones of the foot, as well as between vertebrae Figure In hinge joints , the slightly rounded end of one bone fits into the slightly hollow end of the other bone. In this way, one bone moves while the other remains stationary, like the hinge of a door.
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