180
UNIT 2
Covering, Support, and Movement of the Body
6
they die, the surrounding matrix is resorbed. Osteocytes also act
as stress or strain “sensors” and respond to mechanical stimuli
(bone loading, bone deformation, weightlessness). Tey com-
municate this information to the cells responsible for bone re-
modeling (osteoblasts and osteoclasts) so that bone matrix can
be made or degraded as necessary to preserve calcium homeo-
stasis. We discuss the bone-destroying
osteoclast
on p. 187 when
we explore bone remodeling.
When actively depositing matrix, osteoblasts are cube
shaped. When inactive, they resemble the flattened osteogenic
cells or may differentiate into bone lining cells. When the os-
teoblasts become completely surrounded by the matrix being
secreted, they become osteocytes.
Osteocytes
Te spidery
osteocytes
(Figure 6.5) are mature
bone cells that occupy spaces (lacunae) that conform to their
shape. Osteocytes monitor and maintain the bone matrix. If
Table 6.1
Bone Markings
NAME OF
BONE MARKING
DESCRIPTION
ILLUSTRATIONS
Projections That Are Sites of Muscle and Ligament Attachment
Tuberosity
(too
0
be
˘
-ros
9
ı
˘
-te)
Large rounded projection; may be
roughened
 
Crest
Narrow ridge of bone; usually prominent
 
Trochanter
(tro-kan
9
ter)
Very large, blunt, irregularly shaped
process (the only examples are on the
femur)
 
Line
Narrow ridge of bone; less prominent
than a crest
 
Tubercle
(too
9
ber-kl)
Small rounded projection or process
 
Epicondyle
(ep
0
ı
˘
-kon
9
dıˉ l)
Raised area on or above a condyle
 
Spine
Sharp, slender, often pointed projection
 
Process
Any bony prominence
 
Projections That Help to Form Joints
Head
Bony expansion carried on a narrow neck
 
Facet
Smooth, nearly flat articular surface
 
Condyle
(kon
9
dıˉ l)
Rounded articular projection
 
Ramus
(ra
9
mus)
Armlike bar of bone
 
Depressions and Openings
For Passage of Blood Vessels and Nerves
 
Groove
Furrow
 
Fissure
Narrow, slitlike opening
 
Foramen
(fo-ra
9
men)
Round or oval opening through a bone
 
Notch
Indentation at the edge of a structure
 
Others
 
Meatus
(me-a
9
tus)
Canal-like passageway
 
Sinus
Cavity within a bone, filled with air and
lined with mucous membrane
 
Fossa
(fos
9
ah)
Shallow, basinlike depression in a bone,
often serving as an articular surface
 
Iliac
crest
Ischial
spine
Ischial
tuberosity
Coxal
bone
Trochanter
Femur
of
thigh
Intertrochanteric
line
Adductor
tubercle
Condyle
Medial
epicondyle
Vertebra
Spinous
process
Facet
Head
Facets
Rib
Condyle
Ramus
Mandible
Sinus
Groove
Notch
Fossa
Meatus
Inferior
orbital
fissure
Foramen
Skull
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