1. Fundamentals of Anatomy & Physiology
Eleventh Edition
Chapter 6
Bones and Bone Structure
Lecture Presentation by
Deborah A. Hutchinson
Seattle University
© 2018 Pearson Education, Inc.

2. Learning Outcomes
6-1 Describe the major functions of the skeletal system. 6-2 Classify bones according to shape and structure, giving examples of each type, and explain the functional significance of each of the major types of bone markings. 6-3 Identify the cell types in bone, and list their major functions. 6-4 Compare the structures and functions of compact bone and spongy bone. 6-5 Compare the mechanisms of endochondral ossification and intramembranous ossification.
© 2018 Pearson Education, Inc.

3. Learning Outcomes
6-6 Describe the remodeling and homeostatic mechanisms of the skeletal system. 6-7 Discuss the effects of exercise, nutrition, and hormones on bone development and on the skeletal system. 6-8 Explain the role of calcium as it relates to the skeletal system. 6-9 Describe the types of fractures, and explain how fractures heal Summarize the effects of the aging process on the skeletal system.
© 2018 Pearson Education, Inc.

4. 6-1 Functions of Skeletal System
Skeletal system includes
Bones of the skeleton
Cartilages, ligaments, and other connective tissues
Primary functions of the skeletal system
Support
Storage of minerals and lipids
Blood cell production
Protection
Leverage
Bones are classified by their
Shape
Structure
© 2018 Pearson Education, Inc.

5. Figure 6–1 A Classification of Bones by Shape.
Sutural Bones d
Flat Bones
Flat bones have thin, parallel surfaces. Flat
bones form the roof of the skull, the sternum
(breastbone), the ribs, and the scapulae
(shoulder blades). They provide protection for
underlying soft tissues and offer an extensive
surface area for the attachment
of skeletal muscles.
Sutural bones, or
Wormian bones, are
small, flat, oddly
shaped bones found
between the flat bones
of the skull. They range
in size from a grain of
sand to a quarter. Their
borders are like pieces
of a jigsaw puzzle.
Sutural bone
Sutures
Parietal bone
Posterior view
Sectional
view b
Irregular Bones e
Long Bones
Irregular bones have
complex shapes with
short, flat, notched, or
ridged surfaces. The
vertebrae that form the
spinal column, the bones
of the pelvis, and several
bones in the skull are
examples of irregular bones.
Long bones are relatively
long and slender. They are
located in the arm and
forearm, thigh and leg,
palms, soles, fingers, and
toes. The femur, the long
bone of the thigh, is the
largest and heaviest bone in
the body.
Vertebra
Humerus c
Short Bones f
Sesamoid Bones
Short bones are
boxlike in
appearance.
Examples of short
bones include the
carpal bones (wrists)
and tarsal bones
(ankles).
Sesamoid bones are
usually small, round, and
flat. They are found near
joints of the knees, hands,
and feet. Few people have
sesamoid bones at every
possible location, but
everyone has sesamoid
patellae (pa-TEL-ē;
singular, patella, a small
shallow dish), or kneecaps.
Carpal
bones
Patella
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6. 6-2 Classification of Bones
Bone markings (surface features)
Projections
Where muscles, tendons, and ligaments attach
At articulations with other bones
Openings and depressions
For passage of blood vessels and nerves
© 2018 Pearson Education, Inc.

7. Figure 6–2 An Introduction to Bone Markings (Part 1 of 2).
Openings
Sinus:
Chamber within
a bone, normally
filled with air
Foramen:
Rounded
passageway for
blood vessels
and/or nerves
Projections
Process:
Projection or
bump
Fissure:
Deep furrow,
cleft, or slit
Ramus:
Part of a bone
that forms an
angle with the
rest of the
structure
Meatus:
Passage or
channel,
especially the
opening of a canal
Skull, anterior view
Canal:
Duct or channel
Skull, lateral view
© 2018 Pearson Education, Inc.

8. Figure 6–2 An Introduction to Bone Markings (Part 2 of 2).
Projections where
muscles, tendons, or
ligaments attach
Projections for forming joints
Head:
Expanded articular
end of an epiphysis,
often separated from
the shaft by a
narrower neck (see
Figure 6–3a)
Trochanter:
Large, rough
projection
Crest:
Prominent
ridge
Spine:
Pointed
process
Neck:
Narrow connection
between the
epiphysis and
diaphysis (see
Figure 6–3a)
Head
Line:
Low ridge
Femur
Tubercle:
Small,
rounded
projection
Pelvis
Neck
Depressions
Facet:
Small, flat
articular surface
Sulcus:
Narrow
groove
Tuberosity:
Rough
projection
Fossa:
Shallow
depression
Humerus
Condyle:
Smooth, rounded
articular process
Trochlea:
Smooth, grooved
articular process
shaped like a pulley
Condyle
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9. 6-2 Classification of Bones
Epiphysis
Spongy
bone
Metaphysis
Compact
Medullary
cavity
Diaphysis
(shaft)
The structure of a representative
long bone (the femur) in longitudinal
section a
Structure of a long bone
Diaphysis (shaft)
Wall of compact bone
Central space called medullary cavity (marrow cavity)
Epiphysis (wide part at each end)
Mostly spongy bone (trabecular bone)
Metaphysis
Where diaphysis and epiphysis meet
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10. 6-2 Classification of Bones
Structure of flat bones
For example, parietal bones of the skull
Consist of spongy bone between two layers of compact bone (cortex)
Within the cranium, the layer of spongy bone is called the diploë
Cortex
(compact bone)
Diploë
(spongy bone)
The structure of a flat bone (the parietal bone) b
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11. 6-3 Bone Tissue Bone matrix
Calcium phosphate, Ca3(PO4)2 makes up almost two- thirds of bone mass
Interacts with calcium hydroxide, Ca(OH)2, to form crystals of hydroxyapatite, Ca10(PO4)6(OH)2
Incorporates other calcium salts such as calcium carbonate (CaCO3) and ions (e.g., magnesium)
A bone lacking a calcified matrix looks normal, but is very flexible
© 2018 Pearson Education, Inc.

12. 6-3 Bone Tissue Bone matrix Matrix proteins
About one-third of bone mass is collagen fibers
Bone cells
Make up only 2 percent of bone mass
Four types
Osteogenic cells
Osteoblasts
Osteocytes
Osteoclasts
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13. 6-3 Bone Tissue Osteogenic cells (osteoprogenitor cells)
Mesenchymal cells that divide to produce osteoblasts
Located in inner cellular layer of periosteum and in endosteum
Assist in fracture repair
Endosteum
Osteogenic
cell
Medullary
cavity
Osteogenic cell: Stem
cell whose divisions
produce osteoblasts a
© 2018 Pearson Education, Inc.

14. 6-3 Bone Tissue Osteoblasts
Immature cells that produce new bone matrix during osteogenesis (ossification)
Osteoid—matrix produced by osteoblasts that has not yet become calcified
Osteoblasts surrounded by bone matrix become osteocytes b
Osteoblast
Osteoid
Matrix
Osteoblast: Immature
bone cell that secretes
organic components of
matrix
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15. 6-3 Bone Tissue Osteocytes Mature bone cells that do not divide
Live in lacunae between layers of matrix
Have cytoplasmic extensions that pass through canaliculi
Two major functions
Maintain protein and mineral content of matrix
Help repair damaged bone c
Matrix
Osteocyte
Canaliculi
Osteocyte: Mature bone
cell that maintains the
bone matrix
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16. 6-3 Bone Tissue Osteoclasts Absorb and remove bone matrix
Large, multinucleate cells
Secrete acids and protein-digesting enzymes
Dissolve bone matrix and release stored minerals
This osteolysis is important in homeostasis
Derived from the same stem cells that produce monocytes and macrophages d
Medullary
cavity
Ruffled
border
Osteoclast
Matrix
Osteoclast: Multinucleate
cell that secretes acids and
enzymes to dissolve bone
matrix
© 2018 Pearson Education, Inc.

17. 6-4 Compact Bone and Spongy Bone
Osteon—functional unit of compact bone
Central canal contains blood vessel(s)
Perforating canals
Perpendicular to surface of bone
Carry blood vessels into deep bone and marrow
Lamellae—layers of bone matrix
Concentric lamellae surround central canal
Interstitial lamellae fill spaces between osteons
Circumferential lamellae are at outer and inner bone surfaces
© 2018 Pearson Education, Inc.

18. Figure 6–7a The Structure of Compact Bone.
Venule
Capillary
Central
canal
Periosteum
Circumferential
lamellae
Concentric
lamellae
Osteons
Concentric
lamellae
Perforating fibers
Interstitial
lamellae
Endosteum
Collagen
fiber
orientation
The orientation of collagen
fibers in adjacent lamellae
of an osteon b
Artery
Vein
Trabeculae of
spongy bone
(see Figure 6–8)
Central
canal
Arteriole
Perforating
canal a
The organization of osteons
and lamellae in compact bone
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19. 6-4 Compact Bone and Spongy Bone
Spongy bone lacks osteons
Matrix forms an open network of trabeculae
Lacks capillaries and venules
Red bone marrow fills spaces between trabeculae
Forms blood cells
Contains blood vessels that supply nutrients to osteocytes by diffusion
Yellow bone marrow
Found in other sites of spongy bone
Stores fat
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20. Figure 6–8 The Structure of Spongy Bone.
Canaliculi
opening
on surface
Trabeculae of
spongy bone
Lamellae
Endosteum
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21. 6-4 Compact Bone and Spongy Bone
Body weight (applied force)
Tension on lateral
side of shaft
Compression on
medial side of shaft
Weight-bearing bones
Trabeculae in epiphysis of femur transfer forces from pelvis to compact bone of femoral shaft
Medial side of shaft compresses
Causing tension on the lateral side
© 2018 Pearson Education, Inc.

22. 6-4 Compact Bone and Spongy Bone
Periosteum—membrane that covers outside of bones
Except within joint cavities
Outer, fibrous layer and inner, cellular layer
Fibers are interwoven with those of tendons
Perforating fibers—fibers that become incorporated into bone tissue
Increase strength of attachments
Functions of periosteum
Isolates bone from surrounding tissues
Provides a route for blood vessels and nerves
Participates in bone growth and repair
© 2018 Pearson Education, Inc.

23. Figure 6–10a The Periosteum and Endosteum.
Circumferential
lamellae
Periosteum
Fibrous layer
Cellular layer
Canaliculi
Osteocyte
in lacuna
Perforating
fibers a
The periosteum contains outer (fibrous) and
inner (cellular) layers. Collagen fibers of the
periosteum are continuous with those of the
bone, adjacent joint capsules, and attached
tendons and ligaments.
© 2018 Pearson Education, Inc.

24. 6-4 Compact Bone and Spongy Bone
Endosteum—incomplete cellular layer that lines medullary cavity
Active during bone growth, repair, and remodeling
Covers trabeculae of spongy bone
Lines central canals of compact bone
Consists of flattened layer of osteogenic cells
Endosteum
Osteoclast
Bone matrix
Osteocyte
Osteogenic
cell
Osteoid
Osteoblast
The endosteum is an incomplete
cellular layer containing osteoblasts,
osteogenic cells, and osteoclasts. b
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25. 6-5 Bone Formation and Growth
Bone development
Ossification (osteogenesis)—bone formation
Calcification—deposition of calcium salts
Occurs during ossification
Two forms of ossification
Endochondral ossification
How most bones form
Primary ossification center develops inside hyaline cartilage
Cartilage is gradually replaced by bone
Seven main steps
Intramembranous ossification
Some human bones grow until about age 25
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26. Figure 6–11 Endochondral Ossification.
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27. 6-5 Bone Formation and Growth
Interstitial growth—growth in length
Secondary ossification centers develop
Epiphyseal closure—completion of epiphyseal growth
Width of epiphyseal cartilages reveals timing of endochondral ossification
Former location of epiphyseal cartilage is visible on x-rays as an epiphyseal line
Remains after epiphyseal closure
© 2018 Pearson Education, Inc.

28. Figure 6–12a Bone Growth at Epiphyseal Cartilages.
An x-ray of growing epiphyseal cartilages (arrows) a
Epiphyseal lines in an adult (arrows) b
© 2018 Pearson Education, Inc.

29. 6-5 Bone Formation and Growth
Appositional growth—growth in width
Thickens and strengthens long bones
Layers of circumferential lamellae are added at outer surface
Deepest layers become replaced by osteons
During this process, osteoclasts slowly remove bone matrix at inner surface of bone
Enlarging medullary cavity
© 2018 Pearson Education, Inc.

30. 6-5 Bone Formation and Growth
Intramembranous ossification
Also called dermal ossification
Because it occurs in the dermis
Produces dermal bones such as mandible (lower jaw) and clavicles (collarbones)
Five main steps
© 2018 Pearson Education, Inc.

31. Figure 6–13 Intramembranous Ossification (Part 1 of 5).
Mesenchymal cells clus-
ter together, differentiate
into osteoblasts, and
start to secrete the
organic components of
the matrix. The resulting
osteoid then becomes
mineralized with calcium
salts forming bone
matrix.
Bone matrix
Osteoid
Mesenchymal cell
Ossification center
Parietal bone
Blood vessel
Frontal
bone
Osteoblast
Occipital bone
Intramembranous ossification
starts about the eighth week of
embryonic development. This
type of ossification occurs in
the deeper layers of the dermis,
forming dermal bones.
Mandible 2
As ossification proceeds,
some osteoblasts are
trapped inside bony pockets
where they differentiate into
osteocytes. The developing
bone grows outward from the
ossification center in small
struts called spicules.
Spicules
Osteocyte
© 2018 Pearson Education, Inc.

32. Figure 6–13 Intramembranous Ossification (Part 3 of 5).
Blood vessels begin to
branch within the region
and grow between the
spicules. The rate of bone
growth accelerates with
oxygen and a reliable
supply of nutrients. As
spicules interconnect,
they trap blood vessels
within the bone.
Blood vessel
trapped
within bone
matrix 4
Continued deposition of bone
by osteoblasts located close
to blood vessels results in a
plate of spongy bone with
blood vessels weaving
throughout.
© 2018 Pearson Education, Inc.

33. Figure 6–13 Intramembranous Ossification (Part 5 of 5).
Subsequent remodeling
around blood vessels
produces osteons typical
of compact bone.
Osteoblasts on the bone
surface along with
connective tissue around
the bone become the
periosteum.
Fibrous periosteum
Compact bone
Blood vessels
trapped within
bone matrix
Areas of spongy bone are
remodeled forming the
diploë and a thin covering
of compact bone.
Spongy bone
Compact bone
Cellular periosteum
© 2018 Pearson Education, Inc.

34. 6-5 Bone Formation and Growth
Blood supply to bones
Nutrient artery and vein
Most bones have one of each (some have more)
Pass through nutrient foramina in diaphysis
Metaphyseal vessels
Supply blood to epiphyseal cartilages
Where bone growth occurs
Periosteal vessels
Supply blood to superficial osteons
And to secondary ossification centers
Periosteum also contains
Network of lymphatic vessels
Sensory nerves
© 2018 Pearson Education, Inc.

35. Figure 6–14 The Blood Supply to a Mature Bone.
Vessels in Bone
Articular
cartilage
Epiphyseal
artery and vein
Metaphyseal
artery and vein
Branches of
nutrient artery
and vein
Periosteum
Compact
bone
Nutrient artery
and vein
Medullary
cavity
Periosteal
arteries and veins
Nutrient
foramen
Periosteum
Artery and vein in
perforating canal
Metaphysis
Metaphyseal
artery and vein
Epiphyseal
line
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36. 6-6 Bone Remodeling Bone remodeling Occurs throughout life
Functions in bone maintenance
By recycling and renewing bone matrix
Involves osteocytes, osteoblasts, and osteoclasts
Normally, activities are balanced
If removal is faster than replacement, bones weaken
If deposition predominates, bones strengthen
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37. 6-7 Exercise, Nutrition, and Hormones
Effects of exercise on bone
Mineral recycling allows bones to adapt to stress
Heavily stressed bones become thicker and stronger
Exercise, particularly weight-bearing exercise, stimulates osteoblasts
Bone degeneration
Bone degenerates quickly
Up to one-third of bone mass can be lost in a few weeks of inactivity
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38. 6-7 Exercise, Nutrition, and Hormones
Nutritional and hormonal effects on bone
Minerals
Calcium and phosphorus are required in the diet
Plus small amounts of magnesium, fluoride, iron, and manganese
Calcitriol and vitamin D3
Calcitriol is made in the kidneys
Essential for normal calcium and phosphate ion absorption in digestive tract
Synthesized from vitamin D3 (cholecalciferol)
© 2018 Pearson Education, Inc.

39. 6-7 Exercise, Nutrition, and Hormones
Nutritional and hormonal effects on bone
Vitamin C is required for collagen synthesis
And it stimulates osteoblast differentiation
Vitamin A stimulates osteoblast activity
Vitamins K and B12 are required for synthesis of bone proteins
Nutritional and hormonal effects on bone
Growth hormone and thyroxine stimulate bone growth
Sex hormones
Estrogen and testosterone stimulate osteoblasts
Parathyroid hormone and calcitonin maintain calcium ion homeostasis
© 2018 Pearson Education, Inc.

40. 6-8 Calcium Homeostasis The skeleton as a calcium reserve
Bones store 99 percent of the body’s calcium
In addition to other minerals
Calcium is the most abundant mineral in the body
Calcium ions are vital to many physiological processes
Organic
compounds
(mostly collagen)
33%
Total inorganic
components
67%
Composition of Bone
Bone Contains
Calcium 39%
Potassium 0.2%
Sodium 0.7%
Magnesium 0.4%
Carbonate 9.7%
Phosphate 17%
99% of the body’s phosphate
80% of the body’s carbonate
50% of the body’s magnesium
35% of the body’s sodium
4% of the body’s potassium
99% of the body’s calcium
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41. 6-8 Calcium Homeostasis Hormones and calcium ion balance
Calcium ion concentrations in body fluids must be closely regulated
Parathyroid hormone and calcitonin affect storage, absorption, and excretion of calcium ions in
Bones (storage)
Digestive tract (absorption)
Kidneys (excretion)
© 2018 Pearson Education, Inc.

42. 6-8 Calcium Homeostasis Parathyroid hormone (PTH)
Produced by parathyroid glands in neck
Increases blood calcium ion levels by
Stimulating osteoclast activity (indirectly)
Increasing intestinal absorption of calcium by enhancing calcitriol secretion by kidneys
Decreasing calcium excretion by kidneys
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43. 6-8 Calcium Homeostasis Calcitonin Secreted by C cells in thyroid
Decreases blood calcium ion levels by
Inhibiting osteoclast activity
Increasing calcium excretion and reducing calcitriol secretion by kidneys
Decreasing intestinal absorption of calcium
© 2018 Pearson Education, Inc.

44. Figure 6–16a Factors That Increase the Blood Calcium Ion Level.
Factors That Increase Blood Calcium Ion Level
These responses are triggered
when blood calcium ion level
decreases below 8.5 mg/dL.
Low Calcium Ion Level in Blood
(below 8.5 mg/dL)
Parathyroid Gland Response
Low calcium level causes the
parathyroid glands to secrete
parathyroid hormone (PTH).
PTH
Bone Response
Intestinal Response
Kidney Response
Osteoclasts stimulated to
release stored calcium ions
from bone
Intestinal
absorption
of calcium
increases
Kidneys
absorb
calcium ions
Osteoclast
more
Bone
calcitriol
Calcium released
Calcium absorbed
Calcium conserved
Ca2+
level in
blood
increases
Decreased calcium
loss in urine
© 2018 Pearson Education, Inc.

45. Figure 6–16b Factors That Increase the Blood Calcium Ion Level.
Factors That Decrease Blood Calcium Ion Level
Intestinal and kidney
responses are triggered when
blood calcium ion level rises
above 11 mg/dL.
High Calcium Ion Level in Blood
(above 11 mg/dL)
Thyroid Gland Response
C cells in the thyroid
gland secrete calcitonin.
Calcitonin
Bone Response
Intestinal Response
Kidney Response
Osteoclast activity
decreases; osteoblast
activity unaffected
Intestinal
absorption
of calcium
decreases
Kidneys
excrete
calcium ions
less
Osteoclast
calcitriol
Bone
Calcium release slowed
Calcium absorbed slowly
Calcium excreted
Ca2+
level in
blood
decreases
Increased calcium
loss in urine
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46. Fractures Cracks or breaks in bones due to physical stress
Open (compound) or closed (simple)
Transverse fracture
Spiral fracture
Displaced fracture
Compression
fracture
Pott’s fracture
Epiphyseal
fracture
Comminuted
fracture
Greenstick fracture
Colles fracture
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47. 6-9 Fracture Repair Fracture hematoma formation
Production of a large blood clot
Establishes a fibrous network
Bone cells in the area die
Fracture
hematoma
Fracture
hematoma
Dead bone
Bone fragments 1
Fracture hematoma
formation.
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48. Figure 6–17 Types of Fractures and Steps in Repair (Part 2 of 4).
Spongy bone of
internal callus
Cartilage of
external callus
Callus formation
Cells of endosteum and periosteum divide and migrate into fracture zone
Calluses stabilize the break
Internal callus develops in medullary cavity
External callus of cartilage and bone surrounds break
Spongy bone of
external callus
Periosteum 2
Callus formation.
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49. Figure 6–17 Types of Fractures and Steps in Repair (Part 3 of 4).
Spongy bone formation
Osteoblasts replace central cartilage of external callus with spongy bone
Internal callus
External callus 3
Spongy bone formation.
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50. Figure 6–17 Types of Fractures and Steps in Repair (Part 4 of 4).
Compact bone formation
Repaired bone may be slightly thicker and stronger than normal
External
callus 4
Compact bone
formation.
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51. 6-10 Effects of Aging on Skeletal System
Bones become thinner and weaker with age
Osteopenia—inadequate ossification (reduction of bone mass)
Begins between ages 30 and 40
Women lose 8 percent of bone mass per decade
Men lose 3 percent
Epiphyses, vertebrae, and jaws are most affected
Results in fragile limbs, reduced height, and tooth loss
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52. 6-10 Effects of Aging on Skeletal System
Osteoporosis—severe loss of bone mass
Compromises normal function
Over age 45, occurs in
29 percent of women
18 percent of men
Hormones and bone loss
Sex hormones help maintain bone mass
In women, osteoporosis accelerates after menopause
Spongy bone in osteoporosis
SEM × 21
Normal spongy bone
SEM × 25
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53. 6-10 Effects of Aging on Skeletal System
Cancer and bone loss
Cancerous tissues release osteoclast-activating factor
Stimulates osteoclasts
Produces severe osteoporosis
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