Download Answer Key: What Did You Learn

McKinley/O’Loughlin
Human Anatomy, 2nd Edition
CHAPTER 8
Answers to “What Did You Learn?”
1.
The lateral angle of the scapula contains the glenoid cavity.
2.
The intertubercular sulcus is a depression between the greater and lesser
tubercles of the humerus that contains the tendon of the long head of the
biceps brachii muscle.
3.
The trochlear notch of the ulna articulates with the trochlea of the humerus.
4.
The proximal end of the radius has a disc-shaped head that articulates with the
capitulum of the humerus and the radial notch of the ulna. It is the head that
participates in the elbow joint.
5.
Each os coxae forms through the fusion of an ilium, an ischium, and a pubis.
6.
The pelvic inlet is the superior opening enclosed by the pelvic brim. The pelvic
outlet is the inferior opening bounded by the coccyx, ischial tuberosities and the
inferior border of the pubic symphysis.
7.
The interosseous membrane extends between the interosseous borders of the tibia and
fibula. This membrane helps stabilize the positions of the two bones and provides
additional surface area for muscle attachment.
8.
The seven tarsal bones are the calcaneus, talus, navicular, three cuneiform bones
(medial cuneiform, intermediate cuneiform, and lateral cuneiform), and the
cuboid. The talus articulates with the leg, while the three cuneiform bones and
the cuboid bones articulate with the metatarsals of the foot.
9.
The apical ectodermal ridge signals the underlying tissue to grow and differentiate
into the components of the limb.
McKinley/O’Loughlin
10.
Human Anatomy, 2nd Edition
Separate fingers and toes are formed by the end of week 8.
Answers to “Content Review”
1.
The pectoral girdle consists of the clavicle and the scapula. Each pectoral girdle
supports one upper limb and provides attachment sites for many muscles that
move the limb. The pelvic girdle is composed a right and left ossa coxae only,
whereas the pelvis consists of the ossa coxae, the sacrum and the coccyx. The
pelvis protects and supports the viscera in the inferior part of the ventral body
cavity.
2.
The scapula is triangular in shape and has three borders. The superior border is
the horizontal edge of the scapula that is superior to the spine. The medial border
[sometimes called the vertebral border] is the scapular edge closest to the
vertebrae, while the lateral border [sometimes called the axillary border] is closest
to the axilla.
3.
The anatomical neck is an almost indistinct groove that marks the location of
the former epiphyseal plate. The anatomical neck is located between the head
and two prominent projections called the greater and lesser tubercles,
respectively. The surgical neck, a common fracture site of the humerus, is a
narrowing of the bone immediately distal to the tubercles, at the transition
from the head to the shaft.
4.
The eight carpal bones of the wrist are arranged in two rows of four bones
each. From the lateral to the medial side, the carpal bones of the proximal
row are the scaphoid, lunate, triquetrum, and pisiform bones. Again
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
beginning on the lateral side, the bones of the distal row of carpal bones are
the trapezium, trapezoid, capitate, and hamate bones.
5.
The glenoid cavity is a shallow, cup-shaped fossa on the lateral side of the scapula
where the head of the humerus articulates with the scapula. It has tubercles on its
superior and inferior edges that represent the attachment sites for muscles that
position the shoulder and arm. The acetabulum is a deep, curved depression on
the lateral surface of the os coxae where the ball-shaped head of the femur
articulates with the pelvis.
6.
Between the ages of 13 and 15 years, the ilium, ischium and pubis fuse to
form the os coxae of the pelvic girdle. The three bones that form the os coxae
all contribute a portion to the acetabulum. Thus, the acetabulum represents a
region where these bones have fused.
7.
The true pelvis lies inferior to the pelvic brim. It encloses the pelvic cavity and
forms a deep, inferior bowl that contains the pelvic organs. The false pelvis lies
superior to the pelvic brim. It is enclosed by the ala of the iliac bones. It forms
the inferior region of the abdominal cavity and houses abdominal organs.
8.
The fibula is a laterally placed bone in the leg that does not bear any weight, but
serves as a site for the attachment of several muscles. Additionally, its distal tip,
called the lateral malleolus extends laterally to the ankle joint where it provides
lateral stability to the ankle.
9.
The arches of the foot prevent the muscles, nerves, and blood vessels that supply
the inferior surface of the foot from being squeezed between the metatarsals and
the ground. In addition, the segmented structure of the foot can best support the
McKinley/O’Loughlin
Human Anatomy, 2nd Edition
weight of the body if the foot is arched, much like the strength exhibited in the
arch of a bridge.
10.
In the fourth week of development, limb buds appear as small ridges along the
lateral sides of the embryo. Upper limb buds appear early in the fourth week,
and lower limb buds appear a few days later. The limb buds have a core of
lateral plate mesoderm which forms bones, tendons, cartilage and connective
tissue. The lateral plate mesoderm is covered by layer of ectoderm, which
forms the epidermis. Early in fifth week, upper limb forms a paddle-shaped
hand plate. A foot plate forms in the lower limb bud in the sixth week.
Digital rays are longitudinal thickenings that will form digits in both the hand
plate [late sixth week] and foot plate [early seventh week]. Between the
digital rays, the tissue undergoes programmed cell death to form fingers and
toes [begins in the seventh week and is complete by the eighth week].