Download Answers to What Did You Learn?

CHAPTER 9
Answers to “What Did You Learn?”
1.
Fibrous joint
2.
Synarthrosis
3.
The three types of fibrous joints are gomphosis, suture, and syndesmosis. A
gomphosis occurs between the roots of an individual tooth with the alveolus
(socket) of the mandible or the maxillae. A gomphosis is functionally classified
as a synarthrosis. A suture is an immovable fibrous joint that tightly binds bones
to each other. It occurs only between bones of the skull, and is functionally
classified as a synarthrosis. A syndesmosis holds bones together with
interosseous membranes, such as between the tibia and fibula, or radius and ulna.
Because slight movement is allowed, a syndesmosis is classified as an
amphiarthrosis.
4.
A symphysis is a cartilaginous joint with a broad, flat disc of fibrocartilage
wedged between the articulating bones. Because a symphysis allows slight
movement, it is functionally categorized as an amphiarthrosis.
5.
Functionally, all synovial joints are classified as diarthroses, since all synovial
joints are freely moveable. All synovial joints have an articular capsule, bones
covered with articular cartilage, a joint cavity that separates articulating bones, a
synovial membrane that secretes synovial fluid, nerves, blood vessels, and
supporting ligaments.
6.
The articular surfaces in the bones that form a saddle joint have convex and
concave regions that resemble the shape of a saddle. This joint permits the
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movement associated with the opposition of the thumb toward the fingers so
objects may be grasped. It has a greater range of movement than a condylar joint.
Condylar joints have an oval convex articulating surface on one bone that
interfaces with a concave articular surface on a second bone. This joint permits
movements at the metacarpophalangeal (MP) joints of fingers 2 through 5.
7.
(a) Flexion is a movement in an anterior-posterior plane that decreases the joint
angle. Flexion of the elbow occurs when the forearm is brought closer to the
anterior surface of the arm, thereby decreasing the joint angle. (b) Circumduction
is a sequence of movements in which the proximal end of an appendage remains
relatively stationary while the distal end makes a circular motion. The resulting
movement makes an imaginary cone shape [e.g., draw a circle on a blackboard
with a piece of chalk—shoulder is stationary while the hand moves].
(c) Opposition is the movement at the carpometacarpal joint, in which the thumb
moves toward the palmar tips of the fingers as it crosses the palm of the hand. It
is the movement that enables the hand to grasp objects.
8.
Each intervertebral disc consists of two components, the annulus fibrosus and the
nucleus pulposus. The anulus fibrosus is a tough outer layer of fibrocartilage that
covers each intervertebral disc. The anulus fibrosus contains collagen fibers that
attach the disc to the bodies of adjacent vertebrae. The nucleus pulposus is the
inner gelatinous core of the disc and is primarily composed of water with some
scattered reticular and elastic fibers.
9.
The anterior sternoclavicular ligament and the posterior sternoclavicular ligament
provide support and stability to the sternoclavicular joint at the sternal end. The
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costoclavicular ligament and the interclavicular ligament all limit the relative
movement of the clavicle at the acromial end.
10.
Most of the stability at the glenohumeral joint is provided by the rotator cuff
muscles (infraspinatus, subscapularis, supraspinatus, and teres minor) and their
associated tendons.
11.
The anular ligament surrounds the neck of the radius and binds the proximal head
of the radius to the ulna. The anular ligament helps hold the head of the radius in
place allowing for rotation of the radial head against the ulna for pronation and
supination of the forearm.
12.
The primary ligaments that support the hip joint are the iliofemoral ligament,
ischiofemoral ligament, and the pubofemoral ligament. The ligament of head of
femur, also called ligamentum teres, provides minimal support.
13.
The intracapsular ligaments of the knee are the anterior and posterior cruciate
ligaments. They cross each other in the form of an X. The anterior cruciate
ligament prevents hyperextension. It prevents the tibia from moving too far
anteriorly on the femur. The posterior cruciate ligament runs the anteroinferior
femur to the posterior side of the tibia. It becomes taut on flexion, and it prevents
hyperflexion of the knee joint. The posterior cruciate ligament prevents posterior
displacement of the tibia on the femur.
14.
The deltoid ligament binds the tibia to the foot on the medial side. This ligament
prevents overeversion of the foot. The multipart lateral ligament binds the fibula
to the foot on the lateral side. The lateral ligament prevents overinversion of the
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foot. It is not as strong as the deltoid ligament, and is more prone to sprains and
tears.
15.
Osteoarthritis is a type of arthritis where the articular cartilage breaks down,
typically due to wear-and-tear changes as a person ages. Osteoarthritis can also
be caused by repetitive use of a joint, so some athletes may develop osteoarthritis
at relatively younger ages.
16.
Joints begin to form by the sixth week of development.
Answers to “Content Review”
1.
Mobility and stability at joints depend on the structure or shape of articulating
bone surfaces, the amount of flexibility of the connective tissue that joins the
bones together, and the muscles, tendons, and ligaments associated with the
joint. There is an inverse relationship between joint mobility and joint
stability. The more mobile a joint, the less stable it is. Conversely, the more
stable a joint, the less mobile it is.
2.
A fibrous joint contains dense regular (fibrous) connective tissue to hold together
the ends of bones and bone parts. A cartilaginous joint has a pad of cartilage
wedged between the ends of articulating bones.
3.
A joint classified as synarthrosis is immobile. There are three types of
synarthroses: a gomphosis (a fibrous joint between the tooth and the alveolus of
the mandible or maxillae), a suture (a fibrous joint between the skull bones), and a
synchondrosis (a cartilaginous joint where a pad of hyaline cartilage is wedged
between the articulating bones).
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4.
Synovial fluid is [1] produced by the cells of the synovial membrane and [2] a
filtrate from blood plasma. Synovial fluid functions are: (1) lubricate the articular
cartilage on articulating bones, (2) nourish the articular cartilage’s chondrocytes,
and (3) act as a shock absorber, distributing stresses and forces evenly across the
articular surfaces when pressure in the joint suddenly increases.
5.
A hinge joint is a uniaxial joint that permits flexion and extension only. One bone
surface is convex, and the other bone surface is concave. The bones fit together
much like the hinge of a door. Examples of hinge joints are the elbow, knee, and
interphalangeal (IP) joints. A pivot joint also is a uniaxial joint. A pivot joint has
a rounded surface that fits into a concave surface of the other bone, and permits
rotation only. An example of a pivot joint is the atlantoaxial joint.
6.
Abduction is a movement of a body part away from the midline of the body, while
adduction is a medial movement of a body part toward the midline of the body.
Pronation is a rotational movement of the forearm whereby the palm of the hand
is turned to face posteriorly. Supination is a rotational movement of the forearm
whereby the palm of the hand is turned anteriorly.
7.
The glenohumeral joint is a ball-and-socket joint formed by the articulation of the
head of the humerus and the glenoid cavity of the scapula. The coracohumeral
ligament is a thickening of the superior part of the joint capsule while the
glenohumeral ligaments are three thickenings of the anterior part of the capsule.
The tendon for the long head of the biceps brachii travels within the articular
capsule and helps stabilize the humeral head in the joint. However, the main
stability for the joint comes from the rotator cuff muscles and their tendons.
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8.
The main supporting ligaments of the elbow joint are the radial collateral
ligament, which stabilizes the joint at its lateral surface, and the ulnar collateral
ligament, which stabilizes the medial side of the joint and extends from the medial
epicondyle of the humerus to the coronoid process of the ulna and posteriorly to
the olecranon. The anular ligament surrounds the neck of the radius and binds the
proximal head of the radius to the ulna.
9.
An articular capsule covers the distal surfaces of the tibia, the medial malleolus,
the lateral malleolus, and the talus to bind the tibia to the medial side of the foot
and assure correct positioning of the tibia and talus.
10.
The primary age-related changes in a joint are caused by the development of an
inflammatory or degenerative condition called osteoarthritis [degenerative
arthritis]. This condition results in damage to articular cartilages on the articular
surface of the bones. As the articular cartilage undergoes wear-and-tear and
degenerates, swelling of the joint, pain, and stiffness result.
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