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McKinley/O’Loughlin
Human Anatomy, 2nd Edition
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 individual teeth with the alveoli (sockets)
of both the mandible and the maxillae. A gomphosis is functionally classified as
a synarthrosis. Sutures are immovable fibrous joints that tightly bind bones to
each other. They occur only between bones of the skull, and are also functionally
classified as synarthroses. Syndesmoses hold bones together with interosseous
membranes, such as between the tibia and fibula, or radius and ulna. Because
slight movement is allowed, syndesmoses are classified as amphiarthroses.
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.
Synovial joints are freely movable articulations that provide for the widest range
of motion performed at any joint in the body. Functionally, all synovial joints are
classified as diarthroses, since all synovial joints are freely moveable. All
synovial joints have an articular capsule, articular cartilage, a joint cavity, nerves
and blood vessels, supporting ligaments, and synovial fluid.
6.
The articular surface in each bone that forms a saddle joint has two regions: one is
convex and the other concave, thus it is shaped like a saddle. This joint permits
the movement associated with the opposition of the thumb, and thus exhibits a
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
greater range of movement than a condylar joint. Condylar joints have an oval
convex articulating surface on one bone that interfaces with a similarly shaped
depression on the articular surface of the second bone.
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. (c) Opposition
is the movement of the thumb at the carpometacarpal joint, in which the thumb
moves across the palm to touch the palmar tips of the fingers on the same hand. It
is the movement that enables the hand to grasp objects.
8.
The annulus fibrosus contains collagen fibers that attach the disc to the bodies of
adjacent vertebrae, and surround an elastic, soft gelatinous core of the disc, called
the nucleus pulposus. The annulus fibrosus is a tough outer layer of fibrocartilage
that covers each intervertebral disc. The nucleus pulposus is composed of water
with some scattered reticular and elastic fibers.
9.
The anterior sternoclavicular ligament, the posterior sternoclavicular ligament, the
costoclavicular ligament, and the interclavicular ligament all limit the relative
movement of the clavicle.
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.
McKinley/O’Loughlin
11.
Human Anatomy, 2nd Edition
The annular ligament surrounds the neck of the radius and binds the proximal
head of the radius to the ulna. The annular ligament helps hold the head of the
radius in place and prevents it from slipping out of place.
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 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. The posterior cruciate ligament prevents the
femur from sliding off the anterior side of the tibia and prevents the tibia from
being displaced posteriorly.
14.
The deltoid ligament binds the tibia to the foot on the medial side. This ligament
prevents over eversion of the foot. The multipart lateral ligament binds the fibula
to the foot on the lateral side. The lateral ligament prevents over inversion of the
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 also can be
caused by repetitive use of a joint, so some atheletes may develop osteoarthritis at
relatively younger ages.
16.
Joints begin to form by the sixth week of development.
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
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. The more mobile a joint is, the less stable it is. Conversely, the more
stable a joint is, the less mobile it is.
2.
A fibrous joint contains dense regular (fibrous) connective tissue to hold bones
together. A cartilaginous joint has a pad of cartilage wedged between the
articulating bones.
3.
There are three types of synarthroses: a suture (a fibrous joint between the skull
bones), a gomphosis (a fibrous joint between the tooth and the alveolus of the
mandible or maxilla) and a synchondrosis (a cartilaginous joint where a pad of
hyaline cartilage is wedged between the articulating bones).
4.
Synovial fluid is produced by both the cells of the synovial membrane, and a
filtrate from blood plasma.
5.
A hinge joint is an 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 an 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 lateral movement of a body part away from the trunk of the body,
while adduction is a medial movement of a body part toward the trunk of the
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
body. Pronation is a rotational movement of the forearm where the radius and
ulna cross and form an “X”, and the palm of the hand faces posteriorly.
Supination is a rotational movement of the forearm where the radius and ulna are
parallel and the palm of the hand faces anteriorly.
7.
The glenohumeral joint is a ball-and-socket joint between the glenoid cavity of
the scapula and the head of the humerus. A coracohumeral ligament strengthens
the superior part of the articular capsule while glenohumeral ligaments strengthen
the anterior part of the capsule. The tendon for the long head of the biceps brachii
runs within the capsule and helps stabilize the humeral head. However, the main
stability for the joint comes from the rotator cuff muscles and their tendons.
8.
The main supporting ligaments of the elbow joint are the radial collateral
ligament, which stabilizes the lateral surface of the joint, and the ulnar collateral
ligament, which stabilizes the medial surface of the joint. The anular ligament
also binds the radius to the ulna and prevents the head of the radius from slipping
out of place in the joint.
9.
The articular capsule covers the distal surface of the tibia and the medial
malleolus, and the multipart deltoid ligaments bind the tibia to the medial side of
the foot to 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 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.