Transcript Document

6
Osseous Tissue
and Bone
Structure
PowerPoint® Lecture Presentations prepared by
Alexander G. Cheroske
Mesa Community College at Red Mountain
© 2011 Pearson Education, Inc.
Section 1: An Introduction to Bones
• Learning Outcomes
• 6.1 Classify bones according to their shapes,
identify the major types of bone markings,
and explain the functional significance of
surface features.
• 6.2 Identify the parts of a typical long bone,
and describe its internal structures.
• 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.
© 2011 Pearson Education, Inc.
Section 1: An Introduction to Bones
• Learning Outcomes
• 6.5 Explain the process of appositional bone
growth.
• 6.6 Explain the mechanisms of endochondral
ossification.
• 6.7 Explain the mechanisms of intramembranous
ossification.
• 6.8 CLINICAL MODULE Discuss various
abnormalities of bone formation and growth.
© 2011 Pearson Education, Inc.
Section 1: An Introduction to Bones
• Skeletal system components
• Bones (206 total)
• Divisions
1. Axial skeleton (126 bones)
•
Bones of skull, thorax, and vertebral column
•
Form longitudinal axis of body
2. Appendicular skeleton (80 bones)
•
Bones of the limbs and girdles that attach them
to the axial skeleton
• Cartilages
• Ligaments and other connective tissues
© 2011 Pearson Education, Inc.
Axial Skeleton
(126 Bones)
The axial skeleton
consists of the
bones of the skull,
thorax, and vertebral
column. These
elements form the
longitudinal axis of
the body.
Appendicular
Skeleton (80 Bones)
The adult skeletal
system, which can be
divided into the axial
skeleton and the
appendicular skeleton
The appendicular
skeleton includes
the bones of the
limbs and the
pectoral and pelvic
girdles that attach
the limbs to the
axial skeleton.
Figure 6 Section 1
© 2011 Pearson Education, Inc.
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Section 1: An Introduction to Bones
• Functions of the skeletal system
• Support (support for body, attachment for soft
tissues)
• Storage of minerals (calcium and phosphate)
• Calcium most abundant mineral in body (~2–4 lb)
• 98% stored in bones
• Blood cell production (all formed elements of blood)
• Protection (delicate tissues and organs surrounded
by bone)
• Leverage (act as levers with skeletal muscles to
move body)
© 2011 Pearson Education, Inc.
Module 6.1: Bone classification
• Six categories based on shape
1. Flat bones
•
Thin, roughly parallel surfaces
•
Examples: cranial bones, sternum
2. Sutural bones (Wormian bones)
•
Irregular bones formed between cranial bones
•
Number, size, and shape vary
3. Long bones
•
Relatively long and slender
•
Examples: various bones of the limbs
© 2011 Pearson Education, Inc.
Module 6.1: Bone classification
• Six categories based on shape (continued)
4. Irregular bones
•
Complex shapes
•
Examples: vertebrae, bones of pelvis, facial bones
5. Sesamoid bones
•
Small, flat, and somewhat shaped like sesame seed
•
Develop in tendons of knee, hands, and feet
•
Individual variation in location and number
6. Short bones
•
Small and boxy
•
Examples: bones of the wrist (carpals) and ankles (tarsals)
© 2011 Pearson Education, Inc.
Module 6.1: Bone classification
• Bone surface features
• Also known as bone markings
• External and internal features related to functions
• Elevations/projections for tendon and ligament
attachment
• Depressions/grooves/tunnels for blood vessels or
nerves to lie alongside or penetrate
© 2011 Pearson Education, Inc.
Module 6.1: Bone classification
• Skull surface features
• Canal or meatus (large passageway)
• Process (projection or bump)
• Sinus (chamber within bone, usually filled with
air)
• Foramen (small rounded passageway)
• Fissure (elongated cleft or gap)
© 2011 Pearson Education, Inc.
Module 6.1: Bone classification
• Humerus surface features
• Head (expanded proximal end that forms part of
joint)
• Tubercle (small, rounded projection)
• Sulcus (deep, narrow groove)
• Tuberosity (small, rough projection; may occupy
broad area)
• Diaphysis (shaft; elongated body)
• Trochlea (smooth, grooved articular process)
• Condyle (smooth, rounded articular process)
© 2011 Pearson Education, Inc.
Module 6.1: Bone classification
• Femur surface features
• Trochanter (large, rough projection)
• Head
• Neck (narrow connection between head and
diaphysis)
• Diaphysis
• Facet (small, flat articular surface)
• Condyle
© 2011 Pearson Education, Inc.
Module 6.1: Bone classification
• Pelvis surface features
• Crest (prominent ridge)
• Fossa (shallow depression or recess)
• Line (low ridge; more delicate than crest)
• Spine (pointed or narrow process)
• Ramus (extension that makes angle with rest of
structure)
© 2011 Pearson Education, Inc.
Module 6.1 Review
a. Define surface feature.
b. Identify the six broad categories for
classifying a bone according to shape.
c. Compare a tubercle with a tuberosity.
© 2011 Pearson Education, Inc.
Module 6.2: Typical long bone structure
• Long bone features
• Epiphysis (expanded ends)
• Consist largely of spongy bone (trabecular bone)
• Network of struts and plates
• Resists forces from various directions and directs body
weight to diaphysis and joints
• Outer covering of compact bone
• Strong, organized bone
• Articular cartilage
• Covers portions of epiphysis that form articulations
• Avascular and receives resources from synovial fluid
© 2011 Pearson Education, Inc.
Module 6.2: Typical long bone structure
• Long bone features (continued)
• Metaphysis (connects epiphysis to shaft)
• Diaphysis (shaft)
• Contains medullary cavity (marrow cavity)
• Filled with marrow
• Red bone marrow (red blood cell production)
• Yellow bone marrow (adipose storage)
© 2011 Pearson Education, Inc.
Coronal sections through a right femur, showing the boundaries of a long bone’s major
regions, plus the bone’s internal organization and how it distributes the forces applied
to the bone
Body weight
The epiphysis
(e-PIF-i-sis) is an
expanded area
found at each end
of the bone.
The metaphysis
(me-TAF-i-sis; meta,
between) is a narrow
zone that connects
the epiphysis to the
shaft of the bone.
The epiphysis consists
largely of spongy bone,
also called trabecular
bone. Spongy bone
consists of an open network
of struts and plates that
resembles latticework with
a thin covering, or cortex, of
compact bone.
(applied force)
The wall of the diaphysis
consists of a layer of
compact bone.
The diaphysis
(shaft) is long and
tubular.
The medullary cavity
(medulla, innermost part), or
marrow cavity, is a space
within the hollow shaft. In
Compression
life, it is filled with bone
on medial
marrow, a highly vascular
side of shaft
tissue. Red bone marrow
is highly vascular and
involved in the production
of blood cells. Yellow
bone marrow is adipose
tissue important in the
storage of energy reserves.
Tension
on lateral
side of
shaft
Metaphysis
Epiphysis
Figure 6.2
© 2011 Pearson Education, Inc.
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Module 6.2: Typical long bone structure
• Bone vasculature
• Growth and maintenance requires extensive blood
supply
• Vascular features
• Nutrient artery/vein (commonly one each/bone)
• Nutrient foramen (tunnel providing access to marrow
cavity)
• Also supplies osteons of compact bone with blood
• Metaphyseal artery/vein
• Carry blood to/from metaphysis
• Connects to epiphyseal arteries/veins
© 2011 Pearson Education, Inc.
A longitudinal section of the humerus, showing the extensive
|network of blood vessels in long bones
Epiphyseal artery
and vein
The metaphyseal artery (red) and
metaphyseal vein (blue) carry blood to
and from the area of the metaphysis and to
the epiphysis through epiphyseal arteries
and veins.
Metaphysis
Most bones have only one
nutrient artery (shown in
red) and one nutrient vein
(shown in blue), but a few
bones, including the femur,
have more than one of each.
Periosteum
A nutrient foramen is a
tunnel that penetrates the
diaphysis and provides
access for the nutrient artery
and/or vein. Branches of
these large vessels supply
the osteons of the
surrounding compact bone
before entering and
supplying the tissues of the
medullary cavity.
Medullary
cavity
Metaphyseal
artery and vein
An articular cartilage covers portions of
the epiphysis that articulate with other
bones. The cartilage is avascular, and it
relies primarily on diffusion from the
synovial fluid to obtain oxygen and
nutrients and eliminate wastes.
Compact
bone
Metaphysis
Figure 6.2
© 2011 Pearson Education, Inc.
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Module 6.2: Typical long bone structure
• Periosteum features
• Smaller blood vessels (supply superficial
osteons)
• Lymphatic vessels (collect lymph from bone
and osteons)
• Sensory nerves (innervate diaphysis, medullary
cavity, and epiphyses)
© 2011 Pearson Education, Inc.
Module 6.2 Review
a. List the major parts of a long bone.
b. Describe the function of the medullary cavity.
c. If articular cartilage is avascular, how is it
nourished?
© 2011 Pearson Education, Inc.
Module 6.3: Bone tissue
• Four bone cell types
1. Osteocytes (osteo-, bone + cyte, cell)
•
Mature bone cells that cannot divide
•
Most numerous bone cell type
•
Maintain protein and mineral content of adjacent
matrix
•
•
Dissolve matrix to release minerals
•
Rebuild matrix to deposit mineral crystals
Occupy lacunae (pocket)
•
Separated by layers of matrix (lamellae)
•
Connected with canaliculi
© 2011 Pearson Education, Inc.
Module 6.3: Bone tissue
• Four bone cell types (continued)
2. Osteoblasts (blast, precursor)
•
•
Produce new bony matrix (osteogenesis or
ossification)
•
Begins with release of proteins and other organic
components to produce unmineralized matrix (= osteoid)
•
Then assists in depositing calcium salts to convert osteoid
to bone
Become osteocytes once surrounded by bony
matrix
© 2011 Pearson Education, Inc.
The structures of osteocytes and osteoblasts within a
long bone
The layers of matrix
are called lamellae
(lah-MEL-lē; singular,
lamella, a thin plate).
Osteocytes account for most
of the cell population in bone.
Each osteocyte occupies a
lacuna, a pocket sandwiched
between layers of matrix.
Osteocytes cannot divide,
and a lacuna never contains
more than one osteocyte.
Narrow passageways
called canaliculi
penetrate the lamellae,
radiating through the
matrix and connecting
lacunae to one another
and to various blood
vessels that supply
nutrients.
Osteoblast
Osteoid
Figure 6.3
© 2011 Pearson Education, Inc.
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Module 6.3: Bone tissue
• Four bone cell types (continued)
3. Osteoprogenitor cells (progenitor, ancestor)
•
Mesenchymal (stem) cells that produce cells
that differentiate into osteoblasts
•
Important in fracture repair
•
Locations
•
Inner lining of periosteum
•
Lining endosteum in medullary cavity
•
Lining passageways containing blood vessels
© 2011 Pearson Education, Inc.
Module 6.3: Bone tissue
• Four bone cell types (continued)
4. Osteoclasts (clast, to break)
•
Remove and remodel bone matrix
•
Giant cells with 50+ nuclei
•
•
Derived from same stem cells as macrophages
Release acids and proteolytic enzymes to
dissolve matrix and release stored minerals
•
= Osteolysis (lysis, loosening)
© 2011 Pearson Education, Inc.
The structures of osteocytes and osteoblasts
within a long bone
Endosteum
Osteoprogenitor cell
Osteoclast
Figure 6.3
© 2011 Pearson Education, Inc.
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Module 6.3: Bone tissue
• Bone matrix
• Collagen fibers account for ~1/3 bone weight
• Provide flexibility
• Calcium phosphate (Ca3(PO4)2) accounts for
~2/3 bone weight
• Interacts with calcium hydroxide (Ca(OH)2) to
form crystals of hydroxyapatite
(Ca10(PO4)6(OH)2) salts
• Incorporates other salts (calcium carbonate, CaCO3)
and ions (Na, Mg2, F)
• Provides strength
© 2011 Pearson Education, Inc.
Figure 6.3
© 2011 Pearson Education, Inc.
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Module 6.3 Review
a. Define osteocyte, osteoblast, osteoprogenitor
cell, and osteoclast.
b. How would the compressive strength of a
bone be affected if the ratio of collagen to
hydroxyapatite increased?
c. If osteoclast activity exceeds osteoblast
activity in a bone, what would be the effect on
the bone?
© 2011 Pearson Education, Inc.
Module 6.4: Compact and spongy bone
• Compact bone
• Functional unit is osteon
• Organized concentric lamellae around a
central canal
• Osteocytes (in lacunae) lie between lamellae
• Central canal contains small blood vessels
• Canaliculi connect lacunae with each other and
central canal
• Strong along its length
© 2011 Pearson Education, Inc.
The structure of compact bone, as shown in
the shaft of a long bone
Capillary and venule
Central canal
Concentric lamellae
Canaliculi radiating
through the lamellae
interconnect the lacunae
of the osteons with one
another and with the
central canal.
Endosteum
Central canal
Periosteum
Circumferential
lamellae
Osteon
Vein
Compact bone
LM x 375
The osteocytes occupy lacunae that lie
between the lamellae. In preparing this
micrograph, a small piece of bone was
ground down until it was thin enough to
transmit light. In this process, the lacunae
and canaliculi are filled with bone dust, and
thus appear black.
Artery
Interstitial
lamellae
Central canal
Perforating canal
Figure 6.4
© 2011 Pearson Education, Inc.
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Module 6.4: Compact and spongy bone
• Typical long bone organization
• Periosteum (outermost layer)
• Compact bone (outer bone tissue layer)
• Circumferential lamellae (circum-, around + ferre, to bear)
• Outer and inner surfaces of compact bone layer
• Interstitial lamellae
• Fill spaces between osteons
• Osteons
• Contain central canals (parallel to bone surface)
• Connected by perforating canals (perpendicular)
• Spongy bone (innermost layer)
© 2011 Pearson Education, Inc.
Module 6.4: Compact and spongy bone
• Spongy bone
• Located where bones not heavily stressed or in
many directions
• Lamellae form struts and plates (trabeculae)
creating an open network
• Reduces weight of skeleton
• No blood vessels in matrix
• Nutrients reach osteons through canaliculi open to
trabeculae surfaces
© 2011 Pearson Education, Inc.
The structure of spongy bone, as shown in the head of the femur
Trabeculae of
spongy bone
Canaliculi
opening on
surface
Endosteum
Lamellae
Figure 6.4
© 2011 Pearson Education, Inc.
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– 4
Module 6.4 Review
a. Define osteon.
b. Compare the structures and functions of
compact bone and spongy bone.
c. A sample of bone has lamellae that are not
arranged in osteons. Is the sample more
likely from the epiphysis or from the
diaphysis?
© 2011 Pearson Education, Inc.
Module 6.5: Appositional bone growth
• Appositional bone growth
• Increases bone diameter of existing bones
• Does not form original bones
• Osteoprogenitor cells differentiate into osteoblasts that
add bone matrix under periosteum
• Adds successive layers of circumferential lamellae
• Trapped osteoblasts become osteocytes
• Deeper lamellae recycled and replaced by osteons
• Osteoclasts remove matrix at inner surface to enlarge
medullary cavity
© 2011 Pearson Education, Inc.
Increase in bone diameter resulting from appositional growth
Additional circumferential
lamellae are deposited, and
the bone continues to
increase in diameter.
Periosteum
Figure 6.5
© 2011 Pearson Education, Inc.
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Enlargement of the medullary cavity with increased bone diameter
resulting from appositional growth
Bone matrix is removed
by osteoclasts
Infant
Child
Bone deposited by
superficial osteoblasts
Young adult
Adult
Figure 6.5
© 2011 Pearson Education, Inc.
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Module 6.5: Appositional bone growth
• Periosteum
• Two layers
1. Fibrous outer layer
2. Cellular inner layer
• Functions
1. Isolate bone from surrounding tissues
2. Route for blood and nervous supply
3. Actively participate in bone growth and repair
© 2011 Pearson Education, Inc.
Module 6.5: Appositional bone growth
• Perforating fibers
• Created by osteoblasts in periosteum cellular
layer
• Strongly connect tendons, ligaments, and joint
capsules to bone through periosteum
© 2011 Pearson Education, Inc.
Structure of the periosteum
Circumferential
lamellae
Fibrous layer
of periosteum
Cellular layer
of periosteum
Canaliculi
Osteocyte
in lacuna
Perforating
fibers
Figure 6.5
© 2011 Pearson Education, Inc.
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Module 6.5: Appositional bone growth
• Endosteum
• Incomplete cellular layer lining medullary cavity
• Covers spongy bone and lines central canals
• Consists of simple layer of osteoprogenitor
cells
• Where incomplete, osteoclasts and osteoblasts
remodel matrix
© 2011 Pearson Education, Inc.
Structure of the endosteum
Endosteum
Osteoclast
Circumferential lamella
Osteocyte
Osteoprogenitor
cell
Osteoid
Osteoblast
Figure 6.5
© 2011 Pearson Education, Inc.
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Module 6.5 Review
a. Define appositional growth.
b. Distinguish between the periosteum and the
endosteum.
c. As a bone increases in diameter, what
happens to the medullary cavity?
© 2011 Pearson Education, Inc.
Module 6.6: Endochondral ossification
• Initial bone formation in embryo begins with
cartilage
• Replaced by bone through endochondral
(endo-, inside + chondros, cartilage)
ossification
•
Uses cartilage as small model
•
Bone grows in diameter and length
•
Diameter growth involves appositional bone
deposition
Animation: Early Endochondral Ossification
© 2011 Pearson Education, Inc.
Module 6.6: Endochondral ossification
• Steps of endochondral ossification
1. In shaft, chondrocytes enlarge and matrix ossifies
• Chrondrocytes die, leaving cavities within cartilage
2. Blood vessels grow around cartilage edge and
osteoblasts form to create a superficial layer of
bone
3. Blood vessels penetrate central region
• Allow entering fibroblasts to change into osteoblasts
• Spongy bone produced (primary ossification center)
and spreads toward bone ends
© 2011 Pearson Education, Inc.
Module 6.6: Endochondral ossification
• Steps of endochondral ossification (continued)
4. Medullary cavity created as cartilage replaced by
osseous tissue
• Bone grows in length and diameter
5. Secondary ossification centers form as
capillaries and osteoblasts migrate into epiphyses
6. Epiphyses fill with spongy bone
• Only articular cartilage (on epiphyses) and
epiphyseal cartilage (in metaphysis) remain
© 2011 Pearson Education, Inc.
The process of endochondral ossification
Hyaline cartilage
Articular cartilage
Epiphysis
Enlarging
chondrocytes within
calcifying matrix
Metaphysis
Epiphysis
Medullary
cavity
Blood
vessel
Diaphysis
Primary
ossification
center
Medullary
cavity
Epiphyseal
cartilage
Periosteum
Compact
bone
Diaphysis
Superficial
bone
Spongy
bone
Formation of an epiphyseal
cartilage between epiphysis
and diaphysis
Metaphysis
Bone
formation
Secondary
ossification
center
Hyaline cartilage
Enlargement of
chondrocytes
Spongy
bone
Formation of superficial
layer of bone
Production of spongy bone at
a primary ossification center
Further growth in length
and diameter
Formation of secondary
ossification centers
Figure 6.6
© 2011 Pearson Education, Inc.
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– 6
Module 6.6: Endochondral ossification
• Steps of endochondral ossification (continued)
7. Bone grows in length at epiphyseal cartilage
• Chondrocytes actively produce more cartilage on
epiphysis side
• Osteoblasts actively replace cartilage with bone on
shaft side
• As long as both processes are equally active, bone
lengthening continues
• At puberty, hormones increase bone growth and epiphyseal
cartilage is replaced
• Leaves epiphyseal line in adults
© 2011 Pearson Education, Inc.
The ossifying surface of an
epiphyseal cartilage
Epiphyseal
cartilage matrix
Cartilage cells undergoing
division and secreting
additional cartilage matrix
Articular cartilage
Spongy
bone
Epiphyseal
cartilage
Diaphysis
LM x 250
Medullary Osteoblasts Osteoid
cavity
Formation of an epiphyseal
cartilage between epiphysis
and diaphysis
© 2011 Pearson Education, Inc.
Figure 6.6
6
– 7
Module 6.6 Review
a. Define endochondral ossification.
b. In endochondral ossification, what is the
original source of osteoblasts?
c. How could x-rays of the femur be used to
determine whether a person has reached full
height?
© 2011 Pearson Education, Inc.
Module 6.7: Intramembranous ossification
• Begins as mesenchymal (stem) cells differentiate
into osteoblasts within embryonic or fibrous
connective tissue
• Normally occurs in deeper layers of dermis
•
= Dermal bones (or membrane bones)
• Examples:
•
Roofing bones of skull
•
Lower jaw
•
Collarbone
•
Sesamoid bones such as patella
© 2011 Pearson Education, Inc.
Module 6.7: Intramembranous ossification
• Steps of intramembranous ossification
•
Mesenchymal cells secrete osteoid matrix
•
•
Differentiate into osteoblasts
Osteoid matrix becomes mineralized
•
Forms ossification center
•
Bone grows out in small struts (spicules)
•
Osteoblasts become trapped and mature into
osteocytes
•
•
Mesenchymal cells produce more osteoblasts
Blood vessels enter and become trapped in
developing bone
© 2011 Pearson Education, Inc.
Osteocyte in lacuna
The process of intramembranous ossification
Bone matrix
Osteoblast
Osteoid
Embryonic connective tissue
Mesenchymal cell
Blood
vessel
LM x 32
Blood vessel
Osteoblasts
Spicules
The growth of developing bone outward from the ossification
center in small struts called spicules
Osteocytes
in lacunae
Osteoblast
layer
LM x 32
Spongy bone, the initial form of
intramembranous bone
Blood vessels
The growth and entrapment of
blood vessels within developing
bone
Figure 6.7
© 2011 Pearson Education, Inc.
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– 3
Module 6.7: Intramembranous ossification
• Further membranous bone development
•
Spongy bone formed initially
•
Remodeling around blood vessels forms
osteons of compact bone
•
Periosteum forms, lined with osteoblasts
•
Begins at approximately 8th week of
embryonic development
© 2011 Pearson Education, Inc.
16 weeks of development
10 weeks of development
Flat bones
of the skull
Intramembranous
ossification centers
that produce the
roofing bones of
the skull
Primary
ossification
centers of the
long bones of
the lower limb
Future
hip bone
Long bones
of the limbs
The extent of intramembranous and
endochondrial ossification occurring between
10 and 16 weeks of development
Figure 6.7
© 2011 Pearson Education, Inc.
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Module 6.7 Review
a. Define intramembranous ossification.
b. During intramembranous ossification, which
type(s) of tissue is (are) replaced by bone?
c. Explain the primary difference between
endochondral ossification and
intramembranous ossification.
© 2011 Pearson Education, Inc.
Module 6.8 CLINICAL MODULE: Abnormal
bone growth and development
• Endocrine and metabolic problems can affect the
skeletal system
•
Disorders causing shortened bones
•
•
Pituitary growth failure
•
Reduction in growth hormone leads to reduced epiphyseal
cartilage activity and short bones
•
Rare due to treatment with synthetic growth hormone
Achondroplasia
•
Epiphyseal cartilage grows unusually slowly
•
Limbs are short
•
Trunk is normal size
© 2011 Pearson Education, Inc.
Figure 6.8
© 2011 Pearson Education, Inc.
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Figure 6.8
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Module 6.8 CLINICAL MODULE: Abnormal
bone growth and development
• Disorders causing lengthened bones
•
•
Marfan syndrome
•
Excessive cartilage formation at epiphyseal
cartilage
•
Causes long, slender limbs
•
Other connective tissue abnormalities cause
cardiovascular issues
Gigantism
•
Overproduction of growth hormone before
puberty
© 2011 Pearson Education, Inc.
Figure 6.8
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Figure 6.8
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Module 6.8 CLINICAL MODULE: Abnormal
bone growth and development
• Other skeletal growth abnormalities
•
Fibrodysplasia ossificans progressiva (FOP)
•
Gene mutation that causes bone deposition
around skeletal muscles
•
•
Bones developing in unusual places = heterotopic
(hetero, place) or ectopic (ektos, outside)
Acromegaly
•
Growth hormone levels rise after epiphyseal plates
close
•
Bones get thicker
•
Especially those in face, jaw, and hands
© 2011 Pearson Education, Inc.
Figure 6.8
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Figure 6.8
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Module 6.8 CLINICAL MODULE: Review
a. Describe Marfan syndrome.
b. Compare gigantism with acromegaly.
c. Why is pituitary dwarfism less common today
in the United States?
© 2011 Pearson Education, Inc.
Section 2: Bone Physiology
• Learning Outcomes
• 6.9
Discuss the effects of hormones on bone
development, and explain the homeostatic
mechanisms involved.
• 6.10 CLINICAL MODULE Describe the types
of fractures, and explain how fractures
heal.
© 2011 Pearson Education, Inc.
Section 2: Bone Physiology
• Bones are important mineral reservoirs
• Mostly calcium but other ions as well
• Calcium
• Most abundant mineral in body
• 1–2 kg (2–4 lb)
• ~99% deposited in skeleton
• Variety of physiological functions
• Concentration variation greater than 30–35% affects
neuron and muscle function
• Normal daily fluctuations are <10%
© 2011 Pearson Education, Inc.
Bone Contains …
Composition of Bone
Calcium 39%
Potassium 0.2%
Sodium 0.7%
Organic
compounds
(mostly collagen)
33%
Magnesium 0.5%
99% of the body’s calcium
4% of the body’s potassium
35% of the body’s sodium
50% of the body’s magnesium
Carbonate 9.8%
80% of the body’s carbonate
Phosphate 17%
99% of the body’s phosphate
Total inorganic 67%
components
The importance of bones as mineral reservoirs
Figure 6 Section 2
© 2011 Pearson Education, Inc.
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Section 2: Bone Physiology
• Calcium (continued)
• Levels controlled by activities of:
• Intestines
• Absorb calcium and phosphate under hormonal control
• Bones
• Remodeling by osteoblasts and osteoclasts
• Kidneys
• Calcium and phosphate loss in urine under hormonal
control
© 2011 Pearson Education, Inc.
Module 6.9: Hormonal control of calcium
• Factors that increase blood calcium levels
• Parathyroid hormone (from parathyroid
glands)
• Responses
• Bones: stimulates osteoclasts to release calcium
• Intestines: enhances calcitriol effects and increases
calcium absorption
• Kidneys: increase release of hormone calcitriol, which
causes calcium reabsorption in kidneys
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Module 6.9: Hormonal control of calcium
• Factors that decrease blood calcium levels
• Calcitonin from thyroid gland C cells
• Responses
• Bone: decrease osteoclast activity
• Intestines: decreased absorption with decreasing PTH
and calcitriol
• Kidneys: inhibits calcitriol release and calcium
reabsorption
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Module 6.9: Hormonal control of calcium
• As a calcium reserve, skeleton has primary
role in calcium homeostasis
• Has direct effect on shape and length of bones
• Release of calcium into blood weakens bones
• Deposit of calcium salts strengthens bones
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Module 6.9 Review
a. Identify the hormones involved in stimulating
and inhibiting the release of calcium ions from
bone matrix.
b. What effect would increased PTH secretion
have on blood calcium levels?
c. How does calcitonin lower the calcium ion
concentration of blood?
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Module 6.10 CLINICAL MODULE: Fractures
• Fracture
• Crack or break due to extreme mechanical
stress
• Most heal as long as blood supply and cellular
parts of periosteum and endosteum survive
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Module 6.10 CLINICAL MODULE: Fractures
• Steps of fracture repair
1. Large blood clot (fracture hematoma)
develops
2. Calluses form
•
Internal callus (network of spongy bone uniting
inner edges)
•
External callus (cartilage and bone stabilizes
outer edges)
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Module 6.10 CLINICAL MODULE: Fractures
• Steps of fracture repair (continued)
3. Calluses replaced and dead bone removed
•
Spongy bone unites broken ends
•
Cartilage of external callus replaced by bone
4. Remodeling of healed bone
Animation: Steps in the Repair of a Fracture
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The events in the repair of a bone fracture
Spongy bone Cartilage
of internal of external
callus
callus
Fracture
hematoma
External
callus
Dead
bone
Bone
fragments
Spongy bone of
external callus
Internal
callus
External
callus
Periosteum
Formation of a fracture
hematoma
Formation of an internal
callus and an external
callus
Replacement of the
cartilage of the external
callus with bone
Remodeling over
time and
completion of
repair
Figure 6.10
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1
Module 6.10 CLINICAL MODULE: Fractures
• Types of fractures
• Categories
• Closed or simple (completely internal)
• Only seen on x-rays
• Open or compound (project through skin)
• More dangerous due to:
• Infection
• Uncontrolled bleeding
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Module 6.10 CLINICAL MODULE: Fractures
• Types of fractures (continued)
• Transverse
• Break shaft across long axis
• Spiral
• Produced by twisting stresses
• Spread along length of bone
• Displaced
• Produce new and abnormal bone arrangements
• Nondisplaced retain normal alignment
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Module 6.10 CLINICAL MODULE: Fractures
• Types of fractures (continued)
• Compression
• In vertebrae subjected to extreme stresses
• Greenstick
• One side of shaft broken, one side bent
• Generally occurs in children
• Comminuted
• Shatter affected area producing fragments
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Module 6.10 CLINICAL MODULE: Fractures
• Types of fractures (continued)
• Epiphyseal
• Where bone matrix is calcifying
• A clean transverse fracture of this type heals well
• If not monitored, breaks between epiphyseal plate
and cartilage can stop growth at site
• Pott
• At ankle and affects both leg bones
• Colles
• Break in distal radius
© 2011 Pearson Education, Inc.
Types of Fractures
Transverse
fractures, such as
this fracture of the
ulna, break a bone
shaft across its long
axis.
Comminuted
fractures, such as
this fracture of the
femur, shatter the
affected area into a
multitude of bony
fragments.
© 2011 Pearson Education, Inc.
Spiral fractures,
such as this
fracture of the
tibia, are produced
by twisting
stresses that
spread along the
length of the bone.
Displaced fractures
produce new and
abnormal bone arrangements;
nondisplaced
fractures retain the
normal alignment of
the bones or
fragments.
Compression fractures
occur in vertebrae
subjected to extreme
stresses, such as those
produced by the forces that
arise when you land on your
seat in a fall.
Epiphyseal fractures, such as this
fracture of the femur, tend to occur where
then bone matrix is undergoing calcification
and chondrocytes are dying. A clean
transverse fracture along this line generally
heals well. Unless carefully treated, fractures
between the epiphysis and the epiphyseal
cartilage can permanently stop growth at
this site.
A Pott
fracture occurs
at the ankle and
affects both
bones of the leg.
In a greenstick
fracture, such as this
fracture of the radius,
only one side of the
shaft is broken, and
the other is bent. This
type of fracture
generally occurs in
children, whose long
bones have yet to
ossify fully.
A Colles fracture, a
break in the distal
portion of the radius,
is typically the result
of reaching out to
cushion a fall.
Figure 6.10
5
Module 6.10 CLINICAL MODULE: Fractures
a. Define open fracture and closed fracture.
b. List the steps involved in fracture repair,
beginning just after the fracture occurs.
c. When during fracture repair does an external
callus form?
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