Download The Skeletal System: The Appendicular Skeleton

THE SKELETAL SYSTEM: THE APPENDICULAR SKELETON
A.
PECTORAL GIRDLE
What is the pectoral girdle?
The pectoral (shoulder) girdles attach the bones of the upper extremities
to the axial skeleton. Each girdle consists of a clavicle and a scapula.
Describe the clavicle.
The clavicle (collarbone) forms the anterior component of the pectoral
girdle.
It articulates medially with the manubrium of the sternum at the
sternoclavicular joint and articulates laterally with the acromion of the
scapula at the acromioclavicular joint.
What is the function of the clavicle?
The clavicle receives forces from the upper extremity and transfers them
to the axial skeleton.
As the only attachment of the upper extremity to the axial skeleton,
excessive forces, such as falling on one’s outstretched arms, causes all
force to be moved into the clavicle. As a result, this is the most broken
bone in the body.
Describe the scapula.
The scapula is the posterior component of the pectoral girdle. It is freely
positioned over the upper posterior rib cage by complex muscular attachments. There are no bony attachments between the scapula and the
axial skeleton.
What is the glenoid fossa?
The glenoid fossa or cavity, inferior to the acromion of the scapula, is a
shallow depression that receives the head of the humerus, forming the
glenohumeral joint.
What is the function of the scapula?
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In addition to forming the posterior portion of the pectoral girdle and giving
rise to the shoulder joint, the broad and flattened surfaces of the scapula
provide extensive areas for attachment of those muscles which move the
shoulder joint.
Why is it important that the pectoral girdle have only a single attachment to the
axial skeleton?
The pectoral girdles have no articulations with the vertebral column and
are attached to the axial skeleton only by the sternoclavicular joints.
Because of this, as well as the muscular attachments, the pectoral girdles
are not very stable.
However, lack of stability allows the shoulder joint to have free movements and thus allows it to move in all directions.
B.
IDENTIFY THE BONES OF THE UPPER EXTREMITIES
Identify the bones of the upper extremities and the major functions of the elbow-just pictures.
humerus
radius and ulna
trapezium, trapezoid, capitate, hamate (distal row of carpals, lateral to
medial)
scaphoid, lunate, triquetrum, pisiform (proximal row of carpals, lateral to
medial)
5 metacarpals (I – V)
phalanges
C.
PELVIC GIRDLE
Describe the pelvic girdle.
The pelvic (hip) girdle consists of two hipbones (coxal bones or os coxae),
in association with the sacrum and coccyx of the vertebral column.
What is the purpose?
It provides a strong and stable support for the lower extremities, on which
the weight of the body is carried.
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Name the joints that form the pelvic girdle.
The coxal bones are united to each other anteriorly at the pubic
symphysis and posteriorly at the right and left sacroiliac joints.
Name the components of the os coxa.
Each of the two coxal bones of the adult is a composite of three bones
seen in the neonate: 1) superior ilium, 2) inferior and anterior pubis,
3) inferior and posterior ischium.
What is the acetabulum?
The area where the three bones meet and fuse forms a deep lateral
fossa, called the acetabulum, which serves as the socket for articulation
with the head of the femur.
Describe each of the following:
Pelvis -- Together with the sacrum and coccyx, the two coxal bones form
the basin-like structure called the pelvis.
Pelvic brim -- The superior and inferior portions of the pelvis are
separated from each other by a plane that connects the sacral
promontory posteriorly and the pubic symphysis anteriorly. The
circumference of this plane is the brim.
False pelvis -- The portion of the pelvis above the pelvic brim is known as
the greater (false) pelvis.
True pelvis -- The portion of the pelvis below the pelvic brim is known as
the lesser (true) pelvis.
Pelvic inlet -- The superior opening of the lesser pelvis is called the pelvic
inlet.
Pelvic outlet -- The inferior opening of the lesser pelvis is called the pelvic
outlet.
Pelvic axis -- The pelvic axis is an imaginary line passing through the
lesser pelvis at right angles to the center of the planes of the pelvic
inlet and outlet. This represents the course taken by a child’s head
at birth as he or she passes through the birth canal.
D.
FEMALE VS. MALE PELVIS
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List the structural adaptations of the female pelvis for childbirth that makes it
different from the male pelvis.
In females, the:
1.
false pelvis is shallower
2.
pelvic inlet is larger and more oval
3.
pubic arch is greater than a 90 degree angle
4.
ilia are less vertical, being more flared laterally
5.
iliac fossae are shallower
6.
iliac crest is less curved
7.
acetabulum is smaller, related to size of the head of the
female femur (weight bearing comparing to males)
8.
obturator foramen is more oval
E.
IDENTIFY THE BONES OF THE LOWER EXTREMITIES
Identify bones of the lower extremities and the major features of the knee. --just
pictures
femur
patella
tibia and fibula
talus, calcaneus, navicular, cuboid, medial cuneiform, intermediate
cuneiform, lateral cuneiform
5 metatarsals (I-V)
14 phalanges
F.
ARCHES OF THE FOOT
Describe the following:
Medial longitudinal foot arch -- The medial (inner) longitudinal arch begins
at the calcaneus, rises to the talus, then descends through the
navicular, cuneiforms, and the head of the first three metatarsals.
Lateral longitudinal foot arch -- The lateral (outer) longitudinal arch begins
at the calcaneus, rises to the cuboid, then decreases through the
heads of the metatarsals IV and V.
Transverse foot arch -- The transverse arch is formed by the navicular,
three cuneiforms, and the five metatarsals, and passes from medial
to lateral.
What are their functions?
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The arches allow the foot to bear the weight of the body, provide ideal
distribution of weight across the hard and soft tissues of the foot, and
provide leverage while walking. They are not rigid, but rather yield then
spring back when the weight is removed.
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