CHAPTER 7 SKELETAL
SYSTEM—AXIAL SKELETON
Orthopedics is the branch of
medicine—preservation and restoration of skeletal system, joints, etc.
The 206 bones of the body are
divided into 2 groups, the axial skeleton and the appendicular skeleton. See Figure 7.1 P. 196 and Table 7.1 P. 195
1. AXIAL SKELETON---imagine a
straight line through the head and down through the body to between the feet.
The axial skeleton lies around this line. It includes 80 bones:
Ribs
Sternum
Hyoid bone
Skull bones
Backbone (vertebrae)
Auditory ossicles
2. APPENDICULAR SKELETON---bones of the upper & lower limbs (arms & legs) plus the bones (girdles) that connect them to the axial skeleton. Includes 126 bones.
There are 5 principal types
of bones, based on shape:
1. Long bones---greater
length than width and consist of a diaphysis plus a variable number of
epiphyses. Most long bones have 2 epiphyses (1 at each end) but metacarpals,
metatarsals, and phalanges have only 1 and the femur has 4. The diaphyses of a
long bone are mostly compact bone and are slightly curved for greater strength.
A curved long bone absorbs the stress of the body weight at several different
points, so the stress is evenly distributed.
Examples: Bones of thighs, legs, arms,
forearms, fingers and toes
2. Short bones---somewhat
cube-shaped and nearly even in length and width. Mostly spongy bone with a
layer of compact bone covering the surface.
Examples: Wrist and ankle bones
3. Flat bones---generally thin
and composed of 2 nearly parallel plates of compact bone enclosing a layer of
spongy bone. Give protection and provide large areas for muscle attachment.
Examples: Cranial bones—their spongy bone is
called the diploe
Sternum and ribs
Scapulas
4. Irregular bones---complex
shape and do not fall into the first 3 categories.
Examples: Vertebrae and some facial bones
5. Sesamoid bones---small
bones that develop in tendons where considerable pressure develops. They
protect the tendon from excessive wear and tear and may direct pull. Variable
in number but the patellas are always present. If others are present, they are
very small.
One additional type of bone
is classified by location instead of shape:
Sutural or Wormian
bones---small bones within the joints (sutures)
of certain skull bones
BONE
SURFACE MARKINGS TABLE 7.2
P. 198
I.
AXIAL SKELETON---80 bones
A. Skull---22 bones
1. Cranial bones (8)
a. Frontal bone
b. Parietal bones (2)
c. Temporal bones (2)
d. Occipital bone
e. Sphenoid bone—articulates with all
other cranial bones--keystone
f. Ethmoid bone
2. Facial bones (14)
a. Nasal bones (2)
b. Maxillae (2)
c. Zygomatic bones (2)
d. Mandible—only moveable bone of the
skull
e. Lacrimal bones (2)
f.
g. Inferior nasal conchae (2)
h. Vomer
Cranial cavity
Orbits
Nasal cavity
Paranasal sinuses Figure 7.13 P. 211
Small cavities associated
with the ear
A suture is an immovable
joint formed only between skull bones. These joints consist only of CT at birth
(the “soft spots” in a baby’s head called fontanels). Four prominent sutures in
the typical adult skull are:
1. Coronal suture---between
frontal and parietal bones
2. Sagittal suture---between
the 2 parietal bones
3. Lambdoid suture---between
parietal and occipital
4. Squamous suture---between
parietal and temporal
Back to the fontanels—they
are there for 2 reasons:
1. To allow compression of baby’s head
during birth
2. To expand to allow rapid growth of the
brain during infancy
There may be many fontanels
between any of the skull bones but 6 are fairly constant.
Figure 7.14 P. 211
1. Anterior (frontal)—single
and largest
2. Posterior
(occipital)—single
3. Anterolateral
(sphenoid)—paired
4. Posterolateral
(mastoid)—paired
B. Hyoid bone---located in the neck between
the mandible and larynx---only bone in the body that does not articulate with
any other bone. It supports the tongue and allows for muscle attachment.
C. Auditory ossicles---3 in each ear, they
are the malleus, incus and stapes (hammer, anvil, and stirrup)
D. Vertebral column (26 bones)---also called
spine, backbone
1. Cervical vertebrae (7)
2. Thoracic vertebrae (12
3. Lumbar vertebrae (5)
4. Sacrum (5 fused vertebrae)
5. Coccyx (4 fused vertebrae)
Discs made of fibrocartilage
are found between vertebrae. These consist of 2 parts, an outer ring of
fibrocartilage called the annulus fibrosus, and an inner nucleus pulposus, made
of pulpy elastic CT.
The vertebral column develops
4 normal curves Figure 7.16 P. 213
·
Cervical curve
·
Thoracic curve
·
Lumbar curve
·
Sacral curve
E. Thorax (chest)
1. Sternum (breastbone)
a. Manubrium (superior)
b. Body (middle)
c. Xiphoid process (inferior)
2. Ribs (24 bones in pairs)---each articulates
posteriorly with
its corresponding thoracic vertebra
a. Ribs 1 - 7 are attached to the
sternum by costal
cartilages---these are
vertebrosternal ribs (true ribs)
b. Ribs 8 - 10 are attached to each
other and then
to the cartilage of rib
7---vertebrochondral ribs
(false ribs)
c. Ribs 11 & 12 are not attached
anteriorly---vertebral ribs (floating ribs)
CHAPTER 8
APPENDICULAR SKELETON
A. Shoulder girdle (pectoral
girdle)—attaches bones of the
arm to the axial skeleton
1. Clavicle (2)---collarbones
2. Scapula (2)---shoulder blades
B. Arms (upper extremeties)
1. Humerus (2)
2. Ulna (2)
3. Radius (2)
4. Carpal bones (16)---wrist
5. Metacarpals (10)---palm of hand
6. Phalanges (28)---finger bones
C. Pelvic girdle—connects leg bones to the
axial skeleton
1. Coxal, hip, or pelvic bones
(2)---these are formed as 3 bones fuse:
a.
b. Ischium
c. Pubis
D. Legs (lower extremeties)
1. Femur (2)
2. Tibia (2)
3. Fibula (2)
4.
Patella (2)---kneecap
5. Tarsals (14)---ankle
6. Metatarsals (10)---foot
7. Phalanges (28)---toes
Female and male skeletons
differ in a number of ways. Bones of the male are generally larger and heavier.
Articular ends are heavier in relation to the shafts. Heavier muscles of the
male result in larger points of attachment for muscles such as tuberosities,
lines and ridges.
The most significant
differences occur in the pelvis, mostly because the female pelvis is adapted
for childbearing
See Table
8.1 P. 244
CHAPTER 9 ARTICULATIONS
Bones
can't bend so body movements occur at joints
but
by
definition, a joint (arthrosis or articulation) is
Arthrology--study
of joints
Kinesiology---study
of motion of the human body. It involves bones, joints, and muscles.
Based
on two things:
Presence or absence of a space (sunovial
or joint cavity) between the articulating bones
Type of connective tissue that binds the
bones together
1.
Fibrous--NO joint cavity and bones held together by fibrous CT
2.
Cartilaginous--NO joint cavity and bones held together by cartilage
3.
Synovial--HAS a joint cavity and bones are surrounded by an articular capsule
and often also accessory ligaments
Based
on degree of movement.
1.
Synarthrosis--immovable
2.
Amphiarthrosis--slightly movable
3.
Diarthrosis--freely movable
FIBROUS JOINTS—no joint cavity, bones
connected by fibrous CT
1.
Suture--fibrous joint at birth, composed of a thin layer of dense fibrous
CT--unites bones of the skull--irregular interlocking edges. The functional
classification is synarthrosis (no movement). In adults sutures are often
completely united by bone--then called a synostosis (bony joint).
Examples:
Coronal suture
2.
Syndesmosis--fibrous joint in which there is considerably more fibrous tissue
than in a suture and the fit between bones is not as tight.
Example: Distal articulation of fibula and
tibia
3.
Gomphosis--fibrous joint in which a cone-shaped peg fits into a socket. The
functional classification is synarthrosis (no movement).
Example: Articulation of teeth with
jaw--the periodontal ligament is CT that binds the 2 together
CARTILAGINOUS JOINTS—no joint cavity, bones
connected by cartilage.
1.
Synchondrosis--cartilaginous joint connected by hyaline cartilage. Functional
classification is synarthrosis (no movement).
Example: Epiphyseal plate connecting
epiphysis and diaphysis of a growing bone--replaced by a synostosis as growth
ends
2.
Symphysis--cartilaginous joint in which the connecting material is a broad flat
disc of fibrocartilage. Functional classification is amphiarthrosis (slightly
movable).
Examples: Intervertebral discs, disc in
symphysis pubis
SYNOVIAL JOINTS –ALL ARE ALSO DIARTHROSES
These
have a space called the synovial (joint) cavity between articulating bones.
Articular cartilage (hyaline) covers the articulating surfaces but does not
bind bones together. It reduces friction and helps absorb shock.
Sleevelike
articular capsule surrounds the diarthrosis, encloses the synovial cavity and
unites the articulating bones. 2 layers:
1.
Outer fibrous capsule--dense irregular CT which attaches to the periosteum of
the articulating bones. It is flexible enough
to permit movement but strong enough to resist dislocation.
Many
fibrous capsules contain parallel bundles of fibers called ligaments which give
extra strength in holding bone to bone.
2.
Inner layer--synovial membrane.
Many
diarthroses also contain accessory ligaments--either extracapsular ligaments
(outside capsule) or intracapsular ligaments (inside capsule).
Collateral ligaments of knee--extracapsular
Cruciate ligaments of knee--intracapsular
Inside
some synovial joints are extr
1. Allows bones of different shape to fit
closely
2. Helps maintain stability of joint
3. Directs synovial fluid to areas of
greatest friction
4. Acts as a shock absorber
This
is what is usually damaged when we hear about torn cartilage in athletes.
Several types of nerve endings are associated with joints. Some of these carry pain impulses. Others report movement and degree of stretch.
Some components are avascular (such as articular cartilages) but branches of arteries supply ligaments & the articular capsule.
Also
associated with joints:
Bursae
are saclike structures similar to joint capsules with CT walls and a synovial
membrane lining. Located between skin & bone, tendons and bone, muscle
& bone, etc.—to cushion areas where friction develops. (Bursitis)
Tendon
sheaths are tubelike bursae that wrap around tendons to ease movement where
there is considerable pressure.
Movements
are usually described in relation to anatomical position.
1.
Gliding—flat surface of one bone slides over another--the positions of the
bones change but neither angular or rotational movement occurs. (Planar joints)
2.
Angular movements--one part of a structure is bent relative to another part,
changing the angle between the 2 parts.
a. Flexion--decreases the angle between the
surfaces of articulating bones--bending elbow
b. Extension--opposite of flexion (undoes
flexion)--increases the angle between the surfaces of the articulating
bones--straightening arm back
c. Lateral flexion/extension—bend right or
left at waist
d. Hyperextension--extending beyond
anatomical position--bending head forward is flexion, extension would return it
to anatomical position, hyperextension would bend it further back.
e. Abduction--movement of a body part away
from the midline (or spreading the fingers/toes apart)
f. Adduction--movement of a body part toward
the midline (or bringing fingers/toes together)
g. Circumduction---movement of the distal
end of a body part in a circle. Proximal end of a bone remains still while
distal end moves in a circle--combination of flexion, extension, abduction and
adduction--"winding up" for
3.
Rotation--turning of a structure around its long axis
(shaking
head "no")
Summary of Movements Table 9.1 P. 268
1.
Planar joint--articular surfaces are flat and side-to-side or back-and-forth
movements are possible (very little twisting or rotation). Nonaxial.
Joints between carpal bones
Joints between tarsal bones
Articulation of clavicle with sternum and
scapula
Articulation of ribs with vertebrae
2.
Hinge joint--convex surface of one bone fits into the concave surface of
another bone. Movement is in a single plane (monaxial) like a hinged
door--flexion and extension.
Knee
Elbow
Ankle
Interphalangeal joints
Articulation of occipital bone with the
atlas ("yes")
3.
Pivot joint--rounded or pointed surface
of one bone articulates within a ring formed partly by another bone and partly
by a ligament. Rotation is the primary movement--monaxial.
Articulation of the atlas with the dens of
the axis ("no")
Articulation of the proximal ends of the
radius and ulna--allows us to rotate the forearm
4.
Condyloid (ellipsoidal) joint--oval-shaped condyle of one bone fits into an
elliptical depression on another bone. Movement is in 2 planes (biaxial)--side-to-side
and back-and-forth.
Joint at wrist between radius and carpal
bones
Metacarpophalangeal joints of fingers (not
thumb)
5.
Saddle joint--articular surface of one bone is saddle-shaped and the articular
surface of the other bone is shaped like a rider in the saddle (with lots of
imagination). This is a modified condyloid
joint with somewhat freer movement. Biaxial.
Articulation of trapezium of carpus with
metacarpal of thumb
6.
Ball-and-socket (spheroid) joint--ball-like surface of one bone fits into a
cuplike depression of another bone. Movement is in 3 planes (multiaxial).
Hip joint
Shoulder joint
Several
factors contribute to holding a freely movable joint together and determine the
type & extent of motion (range of motion):
1.
Fit of articulating bones
Some interlock (hip joint)
Others fit in various ways & allow a
variety of motions
2.
Strength and tension of joint ligaments
Ligaments restrict the range of movement
and direct movement of the articulating bones
3.
Arrangement and tensions of muscles and tendons around joint
Muscle tension may reinforce ligaments
4.
Apposition of soft parts
When elbow is bent forearm and arm press
together and prevent further bending
5.
Disuse—long periods of disuse may restrict movement of joints
6.
Hormones
Relaxin--produced by placenta and ovaries
during pregnancy--relaxes symphysis pubis and ligaments in pelvic area,
allowing expansion of the pelvic outlet
Rotator cuff P. 276
Knee
P. 282 – 283
Arthroscopy P. 262
Arthroplasty P. 284