Page 303 - Fundamentals of anatomy physiology
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Clinical Case Her teacher notices Jessica’s
lethargy and offers her a glass of
What’s Ailing the Birthday Girl? juice. Even her favorite juice does
not taste good to her.
Jessica just woke up from her nap at daycare. Earlier
this morning the class celebrated her fourth birth- When Jessica’s mother comes
day with cupcakes and singing. Now she feels like crying when to pick her up from daycare, the
she tries to roll over. She can’t seem to get moving out of her teacher pulls her aside for a quick
little cot. conference. “Jessica has not been
“Come on, Jessie, let’s play tag,” says her best friend. When participating in any play activities
Jessica finally gets to a sitting position on the side of the cot, this whole week,” reports the teacher. “Even today, on her birth-
she doesn’t feel like taking a single step. When she stands, she day, she refused to play tag. She takes a really long time getting
feels slow and clumsy. She certainly cannot run after her class- up from the floor after story circle. And she has been limping after
mates. She sits for a while at the coloring table. When she tries naptime. I wonder what’s going on?” What’s ailing Jessica? To
to reach across the table for crayons, she winces and withdraws
her hand. find out, turn to the Clinical Case Wrap-Up on p. 314.
An Introduction to Joints because it is based on the amount of movement possible, a
property known as the range of motion (ROM). Each functional
In this chapter we consider the ways bones interact wherever group is further subdivided primarily on the basis of the ana-
they interconnect. In the last two chapters, you learned the in- tomical structure of the joint (Table 9–1):
dividual bones of the skeleton. These bones provide strength,
support, and protection for softer tissues of the body. However, 1. An immovable joint is a synarthrosis (sin-ar-THRO. -sis; syn,
your daily life demands more of the skeleton—it must also together + arthros, joint). A synarthrosis can be fibrous or
facilitate and adapt to body movements. Think of your ac- cartilaginous, depending on the nature of the connection.
tivities in a typical day: You breathe, talk, walk, sit, stand, and Over time, the two bones may fuse.
change positions countless times. In each case, your skeleton
is directly involved. Movements can occur only at joints, or 2. A slightly movable joint is an amphiarthrosis (am-fe. -ar-
articulations, where two bones meet, because the bones of THRO. -sis; amphi, on both sides). An amphiarthrosis is
the skeleton are fairly inflexible. The characteristic structure of either fibrous or cartilaginous, depending on the nature of
a joint determines the type and amount of movement that may the connection between the opposing bones.
take place. Each joint reflects a compromise between the need
for strength and the need for mobility. 3. A freely movable joint is a diarthrosis (dı.-ar-THRO. -sis; dia,
through), or synovial joint. Diarthroses are subdivided ac-
In this chapter we compare the relationships between ar- cording to the movement permitted.
ticular form and function. We consider several examples that
range from relatively immobile but very strong joints (the in- The second classification scheme relies solely on the
tervertebral joints) to a highly mobile but relatively weak joint anatomy of the joint, without regard to the degree of move-
(the shoulder). ment permitted. Using this framework, we classify joints
as fibrous, cartilaginous, bony, or synovial. Bony joints form
9-1 Joints are categorized according when fibrous or cartilaginous joints ossify. The ossification
may be normal or abnormal, and may occur at various times
to their range of motion or structure in life.
Learning Outcome Contrast the major categories of joints, and explain The two classification schemes are loosely correlated. We
the relationship between structure and function for each category. see many anatomical patterns among immovable or slightly
movable joints, but there is only one type of freely movable
We use two classification methods to categorize joints. The first joint—synovial joints. All synovial joints are diarthroses. We
is the one we will use in this chapter. It is a functional scheme will use the functional classification rather than the anatomical
one because our primary interest is how joints work.
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