Chapter 9 Study Guide_Condensed_Final (1)

Chapter 9: Joints Learning Objectives: 1. Distinguish between the functional and structural classifications for joints. - Structural classifications of joints consider whether the adjacent bones are strongly anchored to each other by fibrous connective tissue or cartilage. Structural classifications of joints also depend on whether the adjacent bones articulate with each other within a joint cavity. The differences divide joints into three structural classifications: fibrous, cartilaginous, and synovial joints. o Fibrous joints – bones are connected by fibrous connective tissue. o Cartilaginous joints – bones are connected to hyaline cartilage or fibrocartilage. o Synovial joints – bones are not directly connected, but still encounter each other in a joint cavity that is filled with lubricating fluid. These are the most common joints in the body. - Functional classifications describe the degree of movement available between the bones. These degrees range from immobile, to slightly mobile, to freely moveable joints. Depending on their location, fibrous joints and cartilaginous joints are functionally classified as a synarthrosis (immobile joint) or an amphiarthrosis (slightly mobile joint). - Synovial joints are functionally classified as a diarthrosis joint (freely movable joint). 2. Describe the structural features and functional characteristics of fibrous joints. - At a fibrous joint, the bones are connected by dense fibrous connective tissue, so there is no joint cavity between them. These joints allow for very little to no movement, providing stability and strength to the skeletal system. The fibrous connective tissue in fibrous joints is very durable, allowing transmission of force between bones. Some fibrous joints are connected tightly to the adjacent bones, providing protection to internal organs. 3. Describe the different types of fibrous joints and give an example of each. - Suture – narrow fibrous joint that is found between most bones in the skull. The tight connection provides protection to the brain as there are no openings between the bones of the skull. An example of a suture are t he frontal and maxillary bones that consist of right and left halves joined together by sutures. These disappear by the eighth year of life, as the halves will fuse together and form a single bone. - Syndesmosis – fibrous joints that can be narrow or more widely separated, held together by a narrow band of connective tissue (ligament) or a wide sheet of connective tissue (interosseus membrane). An example of a syndemosis is the wide gap between the radius and ulna in the arm. This fibrous joint prevents the separation of the two bones but does not limit movement completely. - Gomphosis – narrow fibrous joint found between the roots of a tooth and the socket in the jaw it fits into. This type of joint is classified as a synarthrosis, because it is completely immobile.

4. Describe the structural features and functional characteristics of cartilaginous joints. - In cartilaginous joints, adjacent bones are connected by cartilage. Cartilage is both flexible and durable. These joints lack a joint cavity as they join the bones together only by hyaline cartilage or fibrocartilage. 5. Describe the different types of cartilaginous joints and give an example of each. - Synchondrosis - a cartilaginous joint where bones are joined together by hyaline cartilage. A synchondrosis could be temporary or permanent. o Temporary synchondrosis - epiphyseal plate (growth plate) of a growing long bone. o Permanent synchondrosis - the first sternocostal joint, where the first rib is anchored to the manubrium by its costal cartilage. - Symphysis - a cartilaginous joint where the bones are joined by fibrocartilage. Fibrocartilage is strong because it contains several bundles of thick collagen fibers, giving it the ability to resist pulling and bending forces. Gaps within a symphysis may be narrow or wide. An example of a symphysis is the pubic symphysis, the portions of the right and left hip bones are joined by fibrocartilage. 6. Describe the structural features and functional characteristics of synovial joints. - Synovial joints are the most common joints in the body. The key structural feature of a synovial joint is the presence of a joint cavity, the walls of the joint cavity are formed by the articular capsule, a fibrous connective tissue structure that is attached to each bone just outside the area of the bone’s articulating surface. Since the bones are not directly connected to each other, joint mobility is increased.

- Rotation – body movements that involve turning a body part around its own axis, or one bone rotating in relation to another bone. Rotation can occur at a pivot joint or a ball-and- socket joint. - Supination and pronation – supination is the motion in which rotation of the radius returns the bones to their parallel positions and moves the palm to the anterior facing position. Pronation is the motion that moves the forearm from the supinated position to the pronated (backward) position. The proximal radioulnar joint produces this movement. The proximal radioulnar joint is a pivot joint that allows for rotation of the head of the radius. - Dorsiflexion and plantar flexion – the only movements at the ankle joint, produced by a hinge joint. Dorsiflexion is the lifting of the front of the foot, so that the top of the foot moves toward the anterior leg. Plantar flexion is the lifting of the heel of the foot from the ground or pointing the toes downward. - Inversion and eversion – complex movements that involve the multiple plane joints among the tarsal bones of the posterior foot. Inversion is the turning of the foot to angle the bottom of the foot toward the midline. Eversion turns the bottom of the foot away from the midline. - Protraction and retraction – p rotraction of the scapula occurs when the shoulder is moved forward, as when pushing against something. Retraction of the scapula occurs when the scapula is being pulled posteriorly and medially, toward the vertebral column. Synovial joints are involved in these body movements. - Depression and elevation – elevation is the upward movement of the scapula and shoulder; downward movement is depression. The scapulothoracic joint allows these movements to occur. - Excursion – the side-to-side movement of the mandible. The temporomandibular joint (TMJ) allows for this movement. - Superior and inferior rotation – During superior rotation, the glenoid cavity moves upward as the medial end of the scapular spine moves downward. This movement is very important as it contributes to upper limb abduction. Inferior rotation occurs during limb adduction and involves the downward motion of the glenoid cavity with upward movement of the medial end of the scapular spine. Pivot joints condone these movements. - Opposition and reposition – Opposition is the thumb movement that brings the tip of the thumb in contact with the tip of a finger. Joint. Reposition is the returning of the thumb to its anatomical position next to the index finger. Carpometacarpal joints, a type of saddle joint, allow this movement. 9. Describe the structures that support and prevent excess movements at each joint. - Ligaments are the structures that support and prevent excess movements at each joint by limiting the range of motion at the joint. Ligaments are bands of flexible, yet durable, fibrous connective tissue that connect bones to other bones at a joint. They are classified based on shape and function.

10. Describe the two processes by which mesenchyme can give rise to bone. - Intramembranous ossification - mesenchymal cells convert into bone-producing cells that then generate bone tissue. The mesenchyme between the areas of bone production becomes the fibrous connective tissue that fills the spaces between the developing bones. - Endochondral ossification - mesenchyme accumulates and differentiates into hyaline cartilage, which forms a model of the future bone. The hyaline cartilage model is then gradually (over a span of years) displaced by bone. 11. Discuss the process by which joints of the limbs are formed. - The limbs initially develop as small limb buds that appear around the end of the 4 th week of development, on the sides of the embryo. In the sixth week, areas of mesenchyme within the bud begin to differentiate, as each limb bud continues to grow and elongate into the hyaline cartilage that will form models for each of the future bones.