UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
LEARNING OUTCOMES:
7.1
7.2
Introduction
l.
Discuss the active tissues found in a bone.
2.
List the general functions of the skeletal system.
3.
Classify bones according to their shapes, and name an example from each group.
Bone Structure
4.
7.3
7.4
Bone Development and Growth
5.
Distinguish between intramembranous and endochondral bones, and explain how
such bones develop and grow.
6.
Describe the effects of sunlight, nutrition, hormonal secretions, and exercise on
bone development and growth.
Bone Function
7.
7.5
Describe the macroscopic and microscopic structure of a long bone, and list the
functions of these parts.
Discuss the major functions of bones.
Skeletal Organization
8.
Distinguish between the axial and appendicular skeletons, and name the major
parts of each.
7.6 Skull – 7.12 Lower Limb
7.13
9.
Locate and identify the bones and the major features of the bones that comprise
the skull, vertebral column, thoracic cage, pectoral girdle, upper limb, pelvic
girdle, and lower limb.
10.
Describe the differences between male and female skeletons.
Life-Span Changes
11.
Describe life-span changes in the skeletal system.
7-1
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.1
INTRODUCTION
A.
Organs of the Skeletal System:
1.
B.
General Functions of the Skeletal System:
1.
2.
3.
4.
C.
The skeletal system organs include the bones of the skeleton and the
structures that connect bones to other structures including:
a.
ligaments
b.
tendons and
c.
cartilages
support and protect softer tissues
provide points of attachment for muscles
house blood-producing cells
store inorganic salts
Classification of Bones by Shape: See Figure 7.1, page 202.
1.
Long bones consist of a shaft with two ends.
Examples include:
a.
thigh bone = femur
b.
upper arm bone = humerus
2.
Short bones are cube-like.
Examples include:
a.
wrist bones = carpals
b.
ankle bones = tarsals
3.
Flat bones are thin and usually curved.
Examples include:
a.
most skull bones
b.
breast bone = sternum
c.
shoulder blades = scapulae
d.
ribs.
e.
see 7.2 B below
4.
Irregular bones are not long short or flat.
Examples include:
a.
vertebrae
b.
auditory ossicles.
5.
Sesamoid bones develop within a tendon.
The patella is a human sesamoid bone.
7-2
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.2
BONE STRUCTURE
A.
Parts of a Long Bone
See Figure 7.2 page 203 and Figure 7.3a and b, page 204.
1.
Diaphysis = shaft.
a.
b.
2.
Epiphyses (pl) = expanded ends.
a.
b.
c.
3.
consist mainly of spongy bone
surrounded by a thin layer of compact bone.
proximal epiphysis vs. distal epiphysis
Epiphyseal line = remnant of epiphyseal disc/plate.
a.
4.
consists of a central medullary cavity (filled with yellow marrow)
surrounded by a thick collar of compact bone.
cartilage at the junction of the diaphysis and epiphyses (growth
plate).
Periosteum = outer fibrous protective covering of diaphysis.
a.
richly supplied with blood & lymph vessels nerves (nutrition):

5.
b.
Osteogenic layer contains osteoblasts (bone-forming cells) and
osteoclasts (bone-destroying cells)
c.
serves as insertion for tendons and ligaments.
Endosteum = inner lining of medullary cavity.
a.
6.
Nutrient Foramen = perforating canal allowing blood
vessels to enter and leave bone.
contains layer of osteoblasts & osteoclasts.
Articular cartilage = pad of hyaline cartilage on the epiphyses where
long bones articulate or join.
a.
"shock absorber".
7-3
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.2
BONE STRUCTURE:
LONG BONE STRUCTURE SUMMARY (Keyed at the end of this outline)
Long Bone Part
Description
Function
7-4
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.2
BONE STRUCTURE
B.
Flat bones
1.
2.
3.
*
C.
See Fig 7.3c page 204.
covered by periosteum-covered compact bone
surrounding endosteum-covered spongy bone.
In a flat bone the arrangement looks like a sandwich:
a.
spongy bone (meat) sandwiched between
b.
two layers of compact bone (bread).
Hematopoietic tissue (red marrow) is located in the spongy bone within
the epiphyses of long bones and flat bones.
Chemical Composition of Bone (both organic and inorganic)
1.
Organic components (35%):
a.
Cells:

osteoprogenitor cells
1.
derived from mesenchyme
2.
can undergo mitosis and become osteoblasts.

osteoblasts
1.
form bone matrix by secreting collagen
2.
cannot undergo mitosis.

osteocytes
See Fig 7.4 page 205 and
Fig 7.7 page 206.
1.
mature bone cells derived from osteoblasts
2.
principle bone cell
3.
cannot undergo mitosis
4.
maintain daily cellular activities (i.e. exchange of
nutrients & wastes with blood).

osteoclasts
See Fig 7.10 page 209.
1. functions in bone resorption (i.e. destruction of bone
matrix)
2.
important in development growth maintenance &
repair of bone.
b.
Osteoid

primarily collagen (90 % of bone protein) which gives
bone its high tensile strength

Other bone proteins include osteocalcin, osteonectin, and
osteopontin
o
Also contains glycolipids and glycoproteins
2.
Inorganic component (65%):
a.
Hydroxyapatite (mineral salts) which is primarily

calcium phosphate [Ca3(PO4)2.(OH)2] which

gives bone its hardness or rigidity.
7-5
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.2
BONE STRUCTURE
D.
Microscopic Structure of Compact Bone
1.
Compact Bone is solid dense and smooth.
2.
Structural unit = Osteon or Haversian system.
See Fig 7.4 and Fig 7.5 page 205.
a.
b.
c.
E.
Communicating canals within compact bone:

Canaliculi connect the lacunae of osteocytes

Perforating (Volkmann's) canals connect the blood &
nerve supply of adjacent osteons together.
1.
run at right angles to and connects adjacent central
canals (Haversian canals).
Microscopic Structure of Spongy (Cancellous) Bone
See Fig 7.3b and c page 204.
1.
2.
3.
7.3
elongated cylinders cemented together to form the long axis of a
bone
Components of Osteon (Haversian system):

osteocytes (spider-shaped bone cells that lie in "lacunae")
that have laid down a

matrix of collagen and calcium salts in

concentric lamellae (layers) around a

central canal (Haversian canal) containing

blood vessels and nerves
consists of poorly organized trabeculae (small needle-like pieces of bone)
with a lot of open space between them.
nourished by diffusion from nearby Haversian canals.
BONE DEVELOPMENT AND GROWTH (Osteogenesis/ossification)
A.
Introduction
1.
The "skeleton" of an embryo is composed of fibrous CT membranes
(formed from mesenchyme and hyaline cartilage) that are loosely shaped
like bones.
2.
This "skeleton" provides supporting structures for ossification to begin.
3.
At about 6-7 weeks gestation ossification begins and continues throughout
adulthood.
7-6
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.3
BONE DEVELOPMENT AND GROWTH
B.
Ossification follows one of two patterns:
See Fig 7.6 page 206 & See Table 7.1 page 207 for a summary.
Both mechanisms involve the replacement of preexisting CT with bone.
1.
Intramembranous Ossification is when a bone forms on or within a
fibrous CT membrane.
a.
2.
Flat bones are formed in this manner (i.e. skull bones clavicles)
Endochondral Ossification occurs when a bone is formed from a hyaline
cartilage model.
a.
b.
c.
d.
Most bones of the skeleton are formed in this manner.
Primary Ossification center hardens as fetus and infant.
Secondary Ossification centers develop in child and harden
during adolescence and early adulthood.
See Fig 7.8, page 207.
During infancy and childhood long bones lengthen entirely by growth at the
epiphyseal plates (called longitudinal growth) and all bones grow in thickness by
a process called appositional growth.
C.
Growth at the Epiphyseal Plate
1.
See Fig 7.9 page 208.
Structure of the Epiphyseal Plate or Disc (4 zones):
a.
Zone of resting cartilage

near epiphysis

small scattered chondrocytes

anchor plate to epiphysis.
b.
Zone of proliferating cartilage

larger chondrocytes that resemble a stack of coins

Chondrocytes divide to replace those that die at the
diaphyseal surface of the epiphysis.
c.
Zone of Hypertrophic cartilage

extremely large chondrocytes that are arranged in columns

maturing cells.
7-7
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.3
BONE DEVELOPMENT AND GROWTH
C.
Growth at the Epiphyseal Plate
1.
Structure of the Epiphyseal Plate or Disc (4 zones):
d.
2.
The epiphyseal plate allows for bone lengthening until adulthood. As a
child grows
a.
Cartilage cells are produced by mitosis on the epiphyseal side of
the plate
b.
They are then destroyed and replaced by bone on the diaphyseal
side of the plate.
*
Therefore the thickness of the plate remains almost constant while
the bone on the diaphyseal side increases in length.
c.
The cartilage of the epiphyseal plate is replaced by bone forming
the epiphyseal line.
d.
Ossification of most bones is completed by age 25.
*
D.
Zone of calcified cartilage

only a few cells thick

consists of dead cells because the matrix around them
became calcified

This calcified matrix is destroyed by osteoclasts.
Osteoclasts are large multinucleated cells that originate
from white blood cells called monocytes, and are
responsible for bone resorption. See Fig 7.10, page 209.
a.
secrete lysosomal enzymes that digest the organic
matrix
b.
secrete acids that decompose calcium salts into Ca2+
and PO4- ions which can then enter blood.

This matrix is then invaded by bone-building cells,
osteoblasts, which lay down bone on the calcified cartilage
that persists.

As a result the diaphyseal border of the plate is firmly
cemented to the bone of the diaphysis.
See box and Figure 7.11 on page 209 re: growth plate damage in
childhood and Ossification Timetable 7.2, page 209.
Bone Thickening / Appositional Growth
Along with increasing in length bones increase in thickness or diameter.
1.
occurs in osteogenic layer of periosteum
2.
Osteoblasts lay down matrix (compact bone) on outer surface.
3.
This is accompanied by osteoclasts destroying the bone matrix at the
endosteal surface.
7-8
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.3
BONE DEVELOPMENT AND GROWTH
E.
Homeostasis of Bone Tissue
1.
2.
F.
Once bones are formed, the actions of osteoclasts and osteoblasts
continually remodel them.
Bone remodeling occurs throughout life.
a.
Osteoclasts resorb bone
b.
Osteoblasts replace the bone
c.
These opposing processes are highly regulated so that total mass of
bone tissue in adult skeleton normally remains constant, even
though 3%-5% of bone calcium is exchanged each year.
Factors Affecting Bone Development Growth and Repair
A number of factors influence bone development, growth, and repair. These
include nutrition, exposure to sunlight, hormonal secretions, and physical
exercise.
1.
2.
3.
Nutrition
a.
Vitamin D greatly increases intestinal absorption of dietary
calcium & retards its urine loss.
o
Deficiency causes rickets in children and osteomalacia in
adults.
o
Vitamin D is found in dairy products
o
Vitamin D is synthesized in the skin with exposure to
sunlight.
b.
Vitamin A is required for bone resorption controls the activity
distribution and coordination of osteoblasts & osteoclasts during
development.
c.
Vitamin C helps maintain bone matrix (collagen synthesis)
o
Deficiency causes scurvy.
Exposure to sunlight – See F.1.a (above)
Hormonal Secretions:
a.
human Growth Hormone (hGH) from the pituitary gland is
responsible for the general growth of all tissues. In bone it:

Stimulates reproduction of cartilage cells at epiphyseal
plate.
i.
Hyposecretion in childhood results in pituitary
dwarfism.
ii.
Hypersecretion in childhood results in pituitary
gigantism.
iii.
Hypersecretion in adulthood results in acromegaly.
These disorders are discussed in greater detail in
Chapter 13.
7-9
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.3
BONE DEVELOPMENT AND GROWTH
F.
Factors Affecting Bone Development Growth and Repair
3.
Hormonal Secretions:
b.
c.
d.
4.
Physical Exercise
a.
b.
*
7.4
Thyroid hormones
 T4 = Thyroxine stimulates replacement of cartilage by bone in
epiphyseal plate.
 Calcitonin acts on several sites to decrease blood calcium levels
(see 7.4, C. 3. on next page)
Parathyroid Hormone (PTH)
 from parathyroid glands stimulates osteoclasts to resorb bone.
Sex hormones from the male and female gonads (testosterones
and estrogens, respectively)

are abundant at puberty and cause considerable long bone
growth (aid osteoblast activity and promote new bone
growth)

also degenerate cartilage cells in epiphyseal plate (i.e. close
epiphyseal plate).

Estrogen effect is greater than androgen effect
Physical stress stimulates bone growth = hypertrophy.
Lack of exercise = atrophy or bone tissue waste.
See Clinical Application 7.1, Fractures on pages 212-213.
BONE FUNCTION
A.
Support, Protection, and Movement
1.
Support:
a.
The bones in legs and pelvis support the trunk
b.
The atlas (1st vertebra) supports the skull etc.
2.
Protection of underlying organs
a.
The skull protects the brain
b.
The rib cage protects the heart and lungs etc.
3.
Body Movement – discussed in Chapters 8 and 9
a.
Skeletal muscles attached to bones by tendons.
b.
serve as levers to move bones.
B.
Blood Cell Formation - Hematopoiesis
a.
All blood cells are formed in the red marrow of certain bones.
7-10
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.4
BONE FUNCTION
C.
Inorganic Salt Storage
1.
2.
3.
Hydroxyapatite, which is primarily calcium phosphate [Ca3(PO4)2.(OH)2]
gives bone its hardness or rigidity.
Calcium is required for many metabolic processes, including
a.
muscle contraction
b.
nerve impulse conduction
Blood calcium homeostasis must be maintained
a.
Bone Remodeling directly affects blood calcium homeostasis
because the primary matrix of bone is calcium.
Recall that once a bone is formed it is continuously being remodeled
throughout life. This process involves the action of osteoblasts and
osteoclasts (see above) two hormones (calcitonin & parathyroid
hormone) and in turn affects blood calcium homeostasis. See Figure
7.13, page 211.
a.
Parathyroid hormone (PTH) which is secreted by the parathyroid
glands when blood calcium levels are low:

stimulates osteoclast activity (resorption of bone occurs)
which releases Ca2+ into the blood

causes kidney tubules to reabsorb Ca2+ back into the blood

causes intestinal mucosa to increase dietary absorption of
Ca2+ and therefore

causes an increase in blood calcium levels (back to
normal).
b.
Calcitonin which is secreted by the thyroid gland when blood
calcium levels are high:

inhibits bone resorption increases osteoblast activity (i.e.
causes a deposition of bone matrix)

causes the kidney tubules to secrete excess Ca2+ into the
urine and therefore

results in a decrease in blood calcium levels (back to
normal).
7-11
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.4
BONE FUNCTION
C.
Inorganic Salt Storage
3.
Blood Calcium Homeostasis: See Fig 7.13 page 211.
Add arrows to complete negative feedback loop below.
Thyroid Gland
Hormone: Calcitonin
1. Osteoclasts are inhibited.
2. Osteoblasts use excess
Ca++ to lay down bone
matrix.
3. Kidney tubules secrete
excess Ca++ into
urine.
Stimulus: ↑ blood Ca++
↓ blood Ca++
Normal Blood Ca++
Set Point = 8.4-10.3dL
↑ blood Ca++
Stimulus: ↓ blood Ca++
1. Osteoclasts resorb bone matrix.
2. Kidney tubules reabsorb Ca++
back into bloodstream.
3. Intestinal mucosa absorbs Ca++.
Parathyroid Glands
Parathyroid Hormone
7-12
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.5.
SKELETAL ORGANIZATION
A.
B.
C.
7.6
The skeletal system consists of 206 bones and joints that allow for the many
functions discussed above in the overview.
In the next sections we will not only name and locate the bones of the skeleton but
we will study the structure of each.
1.
That is that many bones contain holes that allow blood vessels and/or
nerves to pass through (i.e. foramina) and many bones have distinct
markings that allow for attachment of muscles and therefore movement.
2.
See Table 7.4, page 216: Terms used to describe skeletal structures.
The skeleton is divided into two major divisions: an axial and appendicular
portion.
1.
The axial skeleton includes the bones of the skull, hyoid bone, vertebral
column, and thoracic cage.
2.
The appendicular skeleton includes the limbs of the upper and lower
extremities and the bones that attach those limbs to the trunk (pectoral
and pelvic girdles).
3.
See Table 7.3 page 214 and Figure 7.15 page 215.
SKULL = cranium (brain case) and facial bones:
In addition to the figures presented in this chapter please refer to Human Skull Reference
Plates Twenty-Six through Fifty-Four on pages 254-268.
All the bones of the skull (except the mandible) are firmly interlocked along structures
called sutures.
*
*
A suture is the area where skull bones fuse together or articulate (join).
Sutural (wormian) bones are tiny bones within the skull that lie between major
skull bones. See Fig 7.14 page 214.
1.
Cranium = brain case or helmet. See Table 7.5 page 219.
The cranium is composed of eight bones including the frontal, occipital, sphenoid,
and ethmoid bones, along with a pair of parietal and temporal bones.
a.
Frontal bone = forehead.
○
articulates with parietal bones along coronal suture
See Fig 7.19 page 218.
○
forms superior portion of orbit
See Fig 7.18 page 217.
○
contains 2 frontal (paranasal) sinuses
See Fig 7.20 page 219.
7-13
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.6.
SKULL
1.
Cranium (continued)
b.
Parietal bones = behind frontal bone
o
bulging sides of skull.
o
Articulations: See Fig 7.19 page 218.
1.
anteriorly with frontal bones at coronal suture
2.
posteriorly with occipital bone at lambdoid suture
3.
laterally with temporal bones at squamous suture
4.
between bones at sagittal suture
c.
Occipital bone = base of skull.
See Fig. 7.19 page 218 and Fig 7.21 page 220.

articulates with paired parietal bones along the lambdoid suture

Foramen magnum ("large hole") = opening in occipital bone
where nerve fibers pass from brain into spinal cord

Occipital condyles = rounded processes on either side of foramen
magnum which articulate with the first vertebra (atlas).
d.
Temporal bones lie inferior to parietal bones at squamous suture.
See Fig. 7.19 page 218.

Zygomatic process = bar-like extension that meets the zygomatic
bone

External acoustic meatus = opening in tympanic region which
opens to the inner portions of the ear

Styloid process = needle-like extension (attachment for some neck
muscles)

Mastoid process = a rounded process that extends down from
mastoid region of temporal bone (attachment for neck muscles).

Mandibular fossa = depression where mandibular condyle
articulates.
e.
Sphenoid bone = butterfly shaped bone that spans the length of the
cranial floor.

lateral portions are wedged between many other skull bones =
"keystone". See Fig. 7.19 page 218.

contains two sphenoid (paranasal) sinuses
See Fig 7.20 page 219.

Sella turcica (Fig. 7.22, page 220 and Fig 7.25, page 222) =
portion of sphenoid bone which rises up and forms a saddle-shaped
mass that houses the pituitary gland.
7-14
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.6.
SKULL
1.
Cranium (continued)
f.
Ethmoid bone = complex shaped bone composed of two masses on either
side of the nasal cavity. See Fig. 7.23, page 221.

contains two ethmoid (paranasal) sinuses, See Fig 7.20 page 219.

Cribriform or horizontal plate connects two masses of ethmoid
bone horizontally. See Fig 7.23, page 221.

Perpendicular plate projects downward from cribriform plate to
form superior portion of nasal septum,
See Fig 7.17, page 217 and Fig 7.24, page 221.

Superior and middle nasal conchae = delicate scroll-shaped
plates that project into nasal cavity. See Fig 7.24, page 221
& Fig 7.17, page 217.

Crista galli = process that extends from horizontal plate that
serves as the attachment for meninges (membranes) that
surround the brain. See Fig 7.24b, page 221 and Fig 7.25,
page 222.
*
See Table 7.5, page 219 for summary of Cranial Bones.
2.
The facial skeleton shapes the face and provides attachment for various muscles
that move the jaw and control facial expressions.
See Fig 7.17 page 217, Fig 7.19 page 218, and Table 7.6, page 225.
a.
b.
c.
d.
e.
f.
g.
h.
Maxillary bones (maxillae) = upper jaw.

contains two maxillary (paranasal) sinuses. See Fig 7.20, p 219.
Palatine bones = complete posterior portion of hard palate

See Fig 7.26 page 222.

See box on page 222 re: Cleft palate.
Zygomatic bones = cheek bones.

temporal process projects posteriorly and articulates with the
zygomatic process of temporal bone. These two processes
compose the zygomatic arch. See Fig 7.17, page 217.
Lacrimal bones = median walls of orbit.

See details of orbit below.

Contains lacrimal foramen for tear drainage.
Nasal bones = bridge of nose.
Vomer = inferior portion of nasal septum.

The perpendicular plate of the ethmoid bone forms the superior
portion of nasal septum. See Fig 7.17 page 217.
Inferior Nasal Conchae
Mandible = lower jaw. See Fig 7.29, page 224.

largest strongest bone in the face

mandibular condyle articulates with the mandibular fossa of the
temporal bone at temporomandibular joint (TMJ).

only movable bone in the skull.
7-15
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.6.
7.7
SKULL
3.
Orbit – composed of seven bones. See Fig 7.18, page 217.
4.
Infantile Skull- differs from the adult skull in the following ways
a.
Fontanels

soft spots

allow “molding” of skull in birth canal
b
Large forehead and small face
c
Larger orbits
*
See Fig 7.31, page 226.
5.
Hyoid Bone See Fig 7.16, page 215.
a.
Location:
in neck between lower jaw and larynx
held in place by muscles and ligaments
b.
Function:
supports tongue
Vertebral Column: See Fig. 7.32, page 227 and Table 7.8, page 231.
1.
2.
3.
33 infantile or 26 adult irregular bones are divided into 5 regions:
a.
Cervical region = 7 vertebrae (bones) in neck
o
atlas
o
axis
See Fig 7.35, page 229.
b.
Thoracic region = 12 vertebrae in thoracic cavity.
c.
Lumbar region = 5 large vertebrae in abdominal cavity.
d.
Sacrum = 5 fused vertebrae that articulate with coxal bones of pelvis
See Fig 7.37, page 231.
e.
Coccyx = 4 vertebrae which makeup the tailbone.
See Fig 7.37, page 231.
4 Curvatures exist in the Sagittal plane.
a.
Primary curvatures
o
exist at birth
o
are concave anteriorly
o
thoracic curvature is in thoracic region
o
sacral curvature is in the sacral and coccygeal regions
b.
Secondary curvatures
o
develop during infancy
o
are convex anteriorly
o
cervical curvature is in cervical region

develops as baby starts to hold up head
o
lumbar curvature is in lumbar region

develops as baby begins to stand
Intervertebral disc = protective pad of fibrocartilage between individual vertebra
7-16
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.7
Vertebral Column
4.
A Typical Vertebra: See Fig 7.33 page 228.
a.
body = discoid shaped anterior region
b.
vertebral arch = posterior region

pedicle = short bony posterior projection

lamina = flattened plates that articulate posteriorly into spinous
process
c.
vertebral foramen = opening between body and vertebral arch through
which the spinal cord passes
d.
spinous process = midline posterior projection
e.
transverse processes = laterally from pedicle.
5.
Specific Structure of Vertebrae
See Figures 7.33 page 228, Fig 7.34, page 229, and Fig 7.36 page 230. In lab you
will be able to compare and contrast the structure of vertebra from different
regions of the spine.
*
See Clinical Application 7.2, page 232, Disorders of the Vertebral Column.
7.8
Thoracic Cage includes the ribs, sternum, thoracic vertebrae, and costal cartilages.
See Fig 7.38 page 233.
1.
Ribs:
a.
12 pairs

articulate anteriorly with sternum through costal (hyaline)
cartilage

articulate posteriorly with thoracic vertebrae

Three types:
1.
True ribs = upper 7 pairs that articulate directly with
sternum
2.
False ribs = remaining 5 pairs of ribs
3.
Floating ribs = 11th and 12th pair
These ribs do not articulate anteriorly.

Typical Rib Structure: Fig 7.39, page 234.
1.
Head
2.
Neck
3.
Tubercle
4.
Costal Angle
5.
Costal groove
6.
Body
2.
Sternum: See Fig 7.38a, page 233.
a.
Three parts:

manubrium = upper portion.
1.
resembles handle
2.
articulates with clavicle

body = middle vertical portion.
1.
site where most ribs articulate anteriorly

xiphoid process = lower extension from body.
7-17
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.9
Pectoral Girdle
The pectoral (shoulder) girdle connects the upper limbs to the rib cage and consists of
two pairs of bones.
See Fig 7.40, page 235.
1.
anterior clavicles (2) = collar bones:
a.
medial sternal ends
b.
lateral acromial ends
c.
provide attachments for many muscles
2.
posterior scapulae (2) = shoulder blades:
a.
b.
c.
d.
e.
f.
g.
h.
7.10
See Fig 7.41, page 235.
flattened triangular bones
glenoid cavity (fossa) = small fossa that articulates with the head
of the humerus
coracoid process = anterior projection of superior portion (looks
like a bent finger) attachment for biceps muscle
acromion = uppermost point of shoulder
spine = diagonal posterior extension
body = flattened triangular region
medial & lateral Border
inferior angle
Upper Limb: See Figure 7.42, page 236.
1.
humerus = upper arm bone: See Fig 7.43, page 237.
a.
b.
typical long bone
note location of:

proximal head

distal capitulum and trochlea (articulate with radius and ulna,
respectively)

greater/lesser tubercles

deltoid tuberosity

body

medial/lateral epicondyles

olecranon fossa
7-18
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.10
Upper Limb
2.
Radius = forearm bone on same side as thumb (lateral)
See Fig 7.44 page 238.
a.
3.
Note location of
o
head
o
neck
o
radial tuberosity
o
ulnar notch (distal)
o
styloid process (lateral prominence)
Ulna = forearm bone on same side as pinky (medial)
See Fig 7.44 page 238.
a.
Note location of
o
o
o
o
o
4.
Hand – wrist, palm, and fingers
See Fig 7.45, page 239.
a.
Carpus = 8 carpals (wrist, short) bones.
b.
Metacarpus = 5 metacarpals (hand, long) bones.
c.
Phalanges (plural) phalanx (singular) = finger bone or digit.
o
o
o
o
*
olecranon (process)= prominence of elbow
trochlear notch = receives trochlea of humerus
coronoid process (Fig 7.44b)
head (distal)
styloid process (medial prominence)
Thumb (pollex) = 2 phalanges
Fingers = 3 phalanges
Total per limb = 14 phalanges
See Fig 7.46, page 239 illustrating polydactyly, and box
describing the condition.
See Table 7.9, page 239 summarizing Bones of the Pectoral Girdle and Upper Limbs.
7-19
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.11
Pelvic Girdle = connects lower limbs to the vertebral column
See Fig 7.47, page 240.
1.
2.
Composed of a pair of coxal bones: coxae, hip bones
a.
which articulate:
o
anteriorly at the symphysis pubis, posteriorly with the
sacrum.
b.
Each coxal bone consists of 3 separate bones during childhood but these
bones are securely fused in adults:
See Fig 7.48, page 241.
2.
ischium = lowest L-shaped portion of coxal bone (i.e. area we sit
on).

Note ischial spine
3.
pubis = anterior portion of coxal bone, bladder rests upon it.
*
The pubis (coxal) bones articulate anteriorly at the pubic
symphysis (fibrocartilage disc).
See Fig 7.47a and c, page 240.
Pelvic brim is border between the greater (false) and lesser (true) pelvis.
Lesser (true) pelvis is passageway for fetus during birth.
Differences Between Male and Female Pelves
a.
b.
c.
d.
*
ilium = largest uppermost flaring portion of coxal bone.
iliac crest = prominence of the hip (i.e. hands on hips).

The socket that articulates with head of femur is called the
acetabulum.

The hole in each coxal bone is called the obturator
foramen.
True (Lesser, Lower) and False (Greater, Upper) Pelves
a.
b.
3.
1.
Female ilium is more flared.
Female has wider pubic arch.
Pelvic curvature is flatter in female.
See Figure 7.49, page 241.
See Table 7.10 page 242, Differences Between the Male and Female Skeletons.
7-20
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.12
Lower Limb
See Fig 7.50, page 243.
1.
Femur = thigh bone: See Fig 7.51, page 244.
a.
largest, longest, strongest bone in skeleton
b.
note the location of:
o
head
o
neck
o
greater & lesser trochanters
(attachment for thigh and buttocks muscle)
o
linea aspera
o
lateral & medial condyles (tibia)
o
epicondyles
o
patellar surface (patella).
2.
Patella = knee cap; a sesamoid bone.
3.
Tibia = shin bone:
See Fig 7.52 page 244.
a.
very strong
b.
note location of:
o
medial/lateral condyles
o
tibial tuberosity
o
medial malleolus (bulge of ankle).
4.
Fibula = thin bone lateral to tibia: See Fig 7.52 page 244.
a.
Note the location of:
o
head
o
lateral malleolus (lateral ankle bulge).
5.
Foot – ankle, instep, and toes: See Fig 7.53, page 245 and Fig 7.54, pages 246.
a.
Tarsus = 7 tarsal (ankle) bones.
Body weight is carried on 2 largest tarsals:
o
Talus = uppermost tarsal which articulates with the tibia
and fibula
o
Calcaneus = heel bone.
*
b.
Metatarsus = 5 metatarsal (foot) bones.
c.
Phalanges = toe bones or digits (14 total).
See Table 7.11, page 246 for summary of Bones of the Pelvic Girdle and Lower Limbs.
7-21
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
7.13
LIFE SPAN CHANGES
A.
Age related skeletal changes are apparent at the cellular and whole body level.
1.
Height begins to decrease incrementally at around age 33.
2.
Bone loss gradually exceeds bone replacement.

After menopause females lose bone more rapidly than males.

By age 70 bone loss between sexes is similar.
3.
Fractures increase as bones age.

See Table 7.12 page 247, Possible Reasons for Falls Among
Elderly.
OTHER INTERESTING TOPICS:
A.
B.
C.
Preventing Fragility Fractures. See Introduction, page 202.
Noncollagenous Proteins in Bone. See box, page 210.
Biomineralization. See box on page 213.
INNERCONNECTIONS of the skeletal system with other organ systems: See page 248.
CHAPTER SUMMARY – see pages 249-251.
CHAPTER ASSESSMENTS – see page 252.
INTEGRATIVE ASSESSMENTS/CRITICAL THINKING – see page 253.
HUMAN SKULL REFERENCE PLATES – see pages 254-268.
7-22
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
SUMMARY TABLE (See partial sample key at the end of the outline)
NAME OF
BONE:
SCIENTIFIC
COMMON
AXIAL OR
APPENDICULAR
SKELETON?
CLASSIFICATION BY SHAPE
HOW MANY IN
SKELETON?
SPECIAL
FEATURES OR
MARKINGS
SPECIFIC
ARTICULATION
(S)
SPECIAL
FUNCTIONS
7-23
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
SUMMARY TABLE (See partial sample key at the end of the outline)
NAME OF BONE:
SCIENTIFIC
COMMON
AXIAL OR
APPENDICULAR
SKELETON?
CLASSIFICATION
BY SHAPE
HOW MANY IN
SKELETON?
SPECIAL
FEATURES OR
MARKINGS
SPECIFIC
ARTICULATION
(S)
SPECIAL
FUNCTIONS
7-24
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
CHAPTER 7: THE SKELETAL SYSTEM
OVERVIEW OF LONG BONE STRUCTURE
LONG BONE PART
DESCRIPTION
FUNCTION
Diaphysis
long shaft of bone;
collar of compact bone
surrounding medullary
cavity filled with yellow
marrow (fat storage)
rigidity
Epiphyses
expanded ends of long bone;
spongy bone filled with red
bone marrow
hematopoiesis,
form synovial joints with other
long bones
Periosteum
dense fibrous CT that
surrounds outer surface of
bone; inner layer is
osteogenic layer composed
of osteoblasts & osteoclasts;
A nutrient foramen serves as
passageway for nutrient
artery to penetrate bone.
protection,
attachment site for muscles,
bone remodeling
Endosteum
inner lining of medullary
cavity with osteogenic layer
lining,
bone remodeling
Articular cartilage
covers epiphysis
shock absorber,
forms synovial joint
Nutrient
Foramen/Perforating Canal
Perforating canal allowing
blood vessels to enter and
leave bone
Nourishment
Epiphyseal Line
at junction of epiphysis and
diaphysis
remnant of epiphyseal (growth)
plate
7-25
UNIT 2 - CHAPTER 7: SKELETAL SYSTEM
CHAPTER 7: THE SKELETAL SYSTEM
SAMPLE OF BONE SUMMARY TABLES
NAME of bone:
SCIENTIFIC
SCAPULA
COMMON
SHOULDER BLADE
AXIAL OR
APPENDICULAR
SKELETON?
APPENDICULAR
AXIAL
APPENDICULAR
CLASSIFICATION
BY SHAPE
FLAT
FLAT
LONG
HOW MANY IN
SKELETON?
2
2
56
SPECIAL
FEATURES OR
MARKINGS
ACROMION
ARTICULATES
WITH CLAVICLE,
GLENOID FOSSA
ARTICULATES
WITH HEAD OF
HUMERUS,
CORACOID
PROCESS SERVES
AS ORIGIN FOR
BICEPS BRACHII,
TRIANGULAR
POSTERIOR SPINE
EXT. ACOUSTIC.
MEATUS FOR EAR
CANAL, MASTOID &
STYLOID
PROCESSES SERVE
AS ATTACHMENT
FOR NECK
MUSCLES,
ZYGOMATIC
PROCESS
ARTICULATES WITH
TEMPORAL
PROCESS OF
ZYGOMATIC TO
FORM ARCH
ARTICULATION
SEE ABOVE
SEE ABOVE
WITH ONE ANOTHER
TO FORM FINGERS
SPECIAL
FUNCTIONS
ATTACHMENT SITE
OF UPPER LIMBS,
HEMATOPOIESIS
PROVIDES INLET
FOR SOUND WAVES,
PROTECTION OF
SKULL
MANIPULATION
TEMPORAL
PHALANX
DIGIT (FINGER)
7-26