Upload
jeebusweebus
View
229
Download
0
Embed Size (px)
Citation preview
7/31/2019 Chapt 07 New
1/94
Chapter 7Lecture Outline
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
7-1
7/31/2019 Chapt 07 New
2/94
7-2
Bone Tissue
tissues and organs of the skeletalsystem
histology of osseous tissue
bone development
physiology of osseous tissue bone disorders
7/31/2019 Chapt 07 New
3/94
What are the Functions of theSkeletal System?
7-3
7/31/2019 Chapt 07 New
4/94
7-4
Functions of the Skeleton
support holds the body up, supports teeth movement limb movements, breathing, action of muscle
on bone
protection brain, spinal cord, heart, lungs
blood formationred bone marrowis the chief producerof blood cells
stores calcium and phosphate, influences blood levelsof Ca & P
acid-base balance buffers blood against excessive pHchanges
7/31/2019 Chapt 07 New
5/94
What is the Anatomy of aBone?
7-5
7/31/2019 Chapt 07 New
6/94
7-6
Bone Anatomy Most superficial
layer is theperiosteum.
Figure 7.5b
Periosteum
Endosteum
Perforating fibers
Perforating canal
Osteon
Lacuna
Nerve
Blood vessel
(b)
Spongy bone
Spicules
Centralcanal
Collagen
fibers
Concentric
lamellae
Circumferential
lamellae
Trabeculae
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
7/31/2019 Chapt 07 New
7/94
7-7
Bone Anatomy Most superficial
layer is thePeriosteum.
Next (deeper) isCompact Bone.
osteon
Figure 7.5b
Periosteum
Endosteum
Perforating fibers
Perforating canal
Osteon
Lacuna
Nerve
Blood vessel
(b)
Spongy bone
Spicules
Centralcanal
Collagen
fibers
Concentric
lamellae
Circumferential
lamellae
Trabeculae
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
7/31/2019 Chapt 07 New
8/94
7-8
Bone Anatomy Most superficial
layer is thePeriosteum.
Next (deeper) isCompact Bone.
osteon Next (deeper) is
Spongy Bone.
spicules
trabeculae
Figure 7.5b
Periosteum
Endosteum
Perforating fibers
Perforating canal
Osteon
Lacuna
Nerve
Blood vessel
(b)
Spongy bone
Spicules
Centralcanal
Collagen
fibers
Concentric
lamellae
Circumferential
lamellae
Trabeculae
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
7/31/2019 Chapt 07 New
9/94
7-9
Bone Anatomy Most superficial
layer is thePeriosteum.
Next (deeper) isCompact Bone.
osteon Next (deeper) is
Spongy Bone.
spicules
trabeculae
Deepest is the
Medullary Cavity.
not present insome bones
Figure 7.5b
Periosteum
Endosteum
Perforating fibers
Perforating canal
Osteon
Lacuna
Nerve
Blood vessel
(b)
Spongy bone
Spicules
Centralcanal
Collagen
fibers
Concentric
lamellae
Circumferential
lamellae
Trabeculae
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
7/31/2019 Chapt 07 New
10/94
Endosteum
The spongy bone is coated withreticular tissue (loose CTP) calledendosteum.
Recall that reticular tissue isassociated with Blood Cells.
7-10
7/31/2019 Chapt 07 New
11/94
7-11
Bone Marrow bone marrowoccupies the
medullary cavity of a long bone andsmall spaces amid the trabeculae ofspongy bone
red marrow(hemopoietictissue)- produces blood cells inreticular tissue
yellow marrowfound in adults
fat tissue
no longer produces blood
Figure 7.7
7/31/2019 Chapt 07 New
12/94
What Kinds of Cells areResponsible for Bones?
7-12
7/31/2019 Chapt 07 New
13/94
7-13
Histology of Osseous Tissue
four principal typesof bone cells osteogenic (osteoprogenator) cells
Osteogenic cell Osteoblast Osteocyte
(a) Osteocyte development
Nucleus Mitochondrion
Roughendoplasmicreticulum
Secretoryvesicles
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 7.4a
7/31/2019 Chapt 07 New
14/94
7-14
Histology of Osseous Tissue
four principal typesof bone cells osteogenic (osteoprogenator) cells
osteoblasts
Osteogenic cell Osteoblast Osteocyte
(a) Osteocyte development
Nucleus Mitochondrion
Roughendoplasmicreticulum
Secretoryvesicles
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 7.4a
7/31/2019 Chapt 07 New
15/94
7-15
Histology of Osseous Tissue
four principal typesof bone cells osteogenic (osteoprogenator) cells
osteoblasts
osteocytes
Osteogenic cell Osteoblast Osteocyte
(a) Osteocyte development
Nucleus Mitochondrion
Roughendoplasmicreticulum
Secretoryvesicles
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 7.4a
7/31/2019 Chapt 07 New
16/94
7-16
Histology of Osseous Tissue
four principal typesof bone cells osteogenic (osteoprogenator) cells
osteoblasts
osteocytes
osteoclasts
Osteogenic cell Osteoblast Osteocyte
(a) Osteocyte development
Nucleus Mitochondrion
Roughendoplasmicreticulum
Secretoryvesicles
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 7.4a
7/31/2019 Chapt 07 New
17/94
7-17
Histology of Osseous Tissue osteogenic (osteoprogenator) cells
only mitotic cells of bone (other than blood stem cells)
found in periosteum, endosteum
produce osteoblasts
osteoblasts bone forming cells
synthesize soft organic matter of matrix which hardens by mineraldeposition
are nonmitotic
osteocytes former osteoblasts that have become trapped
in the matrix lacunae tiny cavities where osteocytes reside canaliculi little channels that connect lacunae contribute to homeostatic mechanisms of bone density and Ca and P regulate bone remodeling
7/31/2019 Chapt 07 New
18/94
7/31/2019 Chapt 07 New
19/94
7/31/2019 Chapt 07 New
20/94
7-20
The Bone Matrix
Bone matrix is a compositecombines 2 structural materials
Collagen Fibersgive bone tensile strength with some degree offlexibility
Ground Substance (Calcium Phosphate crystals)givescompression strength
combines optimal mechanical properties of each component
7/31/2019 Chapt 07 New
21/94
7-21
The Bone Matrix What happens if one of the components is missing?
7/31/2019 Chapt 07 New
22/94
7/31/2019 Chapt 07 New
23/94
7-23
The Bone Matrix What happens if one of the components is missing?
Rickets (in children)/Osteomalacia (in adults)Disease causing soft bones due to deficiency ofcalcium salts
7/31/2019 Chapt 07 New
24/94
What Different Shapes ofBones are in our Bodies?
7-24
7/31/2019 Chapt 07 New
25/94
7-25
Shapes of Bones long bones
longer than wide
short bones equal in length and width
flat bones protect soft organs
irregular bones unusual shape
Figure 7.1
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Femur
Scapula
Sternum
Radius
Ulna
Irregular bonesFlat bones
Short bonesLong bones
Capitate(carpal) bone
Talus
7/31/2019 Chapt 07 New
26/94
What is the Structure ofLong Bones?
7-26
7/31/2019 Chapt 07 New
27/94
7-27
Structure of a Long Bone
epiphyses anddiaphysis
compact andspongy bone
Medullary cavity(marrow cavity)
articular cartilage
periosteum
Figure 7.2
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Living (b) Dried
Marrow cavity
Periosteum
Nutrient foramen
Site of endosteum
Compact bone
Spongy bone
Epiphysis
Epiphysis
Diaphysis
Articularcartilage
Epiphysealline
Red bonemarrow
Yellow bone marrow
Epiphysealline
Articularcartilage
7/31/2019 Chapt 07 New
28/94
7-28
General Features of Long Bones
diaphysis(shaft)
epiphyses- ends of a long bone
medullary cavity(marrow cavity) - space in the diaphysisthatcontains bone marrow
compact (dense) boneused in outer shell
spongy bone(cancellous bone) composed of spicules andtrabeculae
articular cartilagehyaline cartilage locatedwhere onebone meets another
7/31/2019 Chapt 07 New
29/94
7-29
Compact Bone Osteonbasic structural unit
of compact bone
concentric lamellaelike a tree trunk
central canalcarries
blood vessels andnerves
collagen fiberscorkscrew down the
matrix of the lamellagiving it a helicalarrangement
7/31/2019 Chapt 07 New
30/94
7-30
Compact Bone
not all of the matrix isorganized into osteons
circumferentiallamellae -inner and
outer boundaries ofdense bone runparallel to bone surface
interstitial lamellae
remains of old osteons
7/31/2019 Chapt 07 New
31/94
7-31
Spongy Bone
slivers of bone calledspicules
thin plates of bone calledtrabeculae
spaces between filled withbone marrow
provides strength withminimalweight
trabeculae develop along bones lines of stress
Spongy bone is also made of layers of lamellae,but NOT osteons NO central canals
7/31/2019 Chapt 07 New
32/94
7/31/2019 Chapt 07 New
33/94
7-33
Structure of a Flat Bone
sandwich-likeconstruction
two layers of compactbone enclosing amiddle layer of spongybone (no medullary cavity)
spongy bone absorbsshock
marrow spaces linedwith endosteum
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Suture
Outer compactbone
Spongy bone(diploe)
Inner compactbone
Trabeculae
Figure 7.3
7/31/2019 Chapt 07 New
34/94
How are Bones Made?
7-34
7/31/2019 Chapt 07 New
35/94
7-35
Bone Development
the formation of bone is calledossification (also known as osteogenesis)
two methods:
intramembranous ossification
endochondral ossification
7/31/2019 Chapt 07 New
36/94
7/31/2019 Chapt 07 New
37/94
7-37
Intramembranous Ossification Used to produce theflat bonesof the skull
bonesdevelop within a fibrous sheetsimilar to dermis
1. Some of the fibroblast-like cells in the sheet change theirbehavior: they differentiate into osteogenic cells.
7/31/2019 Chapt 07 New
38/94
7/31/2019 Chapt 07 New
39/94
7-39
Intramembranous Ossification Used to produce theflat bonesof the skull
bonesdevelop within a fibrous sheetsimilar to dermis
1. Some of the fibroblast-like cells in the sheet change theirbehavior: they differentiate into osteogenic cells.
2. The osteogenic cells produce osteoblasts. A periosteumdevelops to cover the outer surfaces.
3. The osteoblasts make spongy bone. Some of theosteoblasts become trapped in the bony matrix andbecome osteocytes. and endosteum develops to cover the
inner surfaces.
7/31/2019 Chapt 07 New
40/94
7-40
Intramembranous Ossification Used to produce theflat bonesof the skull
bonesdevelop within a fibrous sheetsimilar to dermis
1. Some of the fibroblast-like cells in the sheet change theirbehavior: they differentiate into osteogenic cells.
2. The osteogenic cells produce osteoblasts. A periosteumdevelops to cover the outer surfaces.
3. The osteoblasts make spongy bone. Some of theosteoblasts become trapped in the bony matrix andbecome osteocytes. and endosteum develops to cover the
inner surfaces.4. The spongy bone towards the surfaces of the bone gets
converted into compact bone by more osteoblasts.
7/31/2019 Chapt 07 New
41/94
7/31/2019 Chapt 07 New
42/94
7/31/2019 Chapt 07 New
43/94
7-43
Endochondral Ossification
bone developsfrom pre-existing hyaline cartilage model
most bones develop by this process
This is a 2 Step Process:
Step 1. Ossification of the Diaphysis to produce thePrimary Ossification Center:
a. Recall that hyaline cartilage is covered by perichondrium (denseirregular CTP). This is where cartilage stem cells live.
7/31/2019 Chapt 07 New
44/94
7-44
Endochondral OssificationThis is a 2 Step Process:
Step 1.Ossification of the diaphysis to produce theprimary ossification center:
a. Recall that hyaline cartilage is covered by perichondrium(dense irregular CTP). This is where cartilage stem cells live.These cartilage stem cells change their behavior: they
become osteogenic cells. We now say that the perichondriumis a periosteum.
7/31/2019 Chapt 07 New
45/94
7-45
Endochondral OssificationThis is a 2 Step Process:
Step 1.Ossification of the diaphysis to produce the primary ossificationcenter:
a. Recall that hyaline cartilage is covered by perichondrium (denseirregular CTP). This is where cartilage stem cells live. These cartilagestem cells change their behavior: they become osteogenic cells. Wenow say that the perichondrium is a periosteum.
b. The osteogenic cells produce osteoblasts. The osteoblastsstart producing bony matrix at the models outer surface,
creating a bony collar. The bony collar starts in the middleof the diaphysis then extends to either end.
E d h d l O ifi i
7/31/2019 Chapt 07 New
46/94
7-46
Endochondral OssificationThis is a 2 Step Process:
Step 1.Ossification of the diaphysis to produce the primary ossificationcenter:
a. Recall that hyaline cartilage is covered by perichondrium (dense irregularCTP). This is where cartilage stem cells live. These cartilage stem cellschange their behavior: they become osteogenic cells. We now say thatthe perichondrium is a periosteum.
b. The osteogenic cells produce osteoblasts. The osteoblasts startproducing bony matrix at the models outer surface, creating a bony
collar. The bony collar starts in the middle of the diaphysis then extendsto either end.
c. Chondrocytes deep inside the middle of the diaphysis of the
model now change their behavior: they undergo hypertrophy.
7/31/2019 Chapt 07 New
47/94
2 Ways Tissue can Grow
7-47
Hypertrophy
Proliferation
7/31/2019 Chapt 07 New
48/94
Hypertrophy of Chondrocytes
7-48
Chondrocytes EXPAND, but tissue size stays the same.
7/31/2019 Chapt 07 New
49/94
Hypertrophy of Chondrocytes
7-49
Chondrocytes EXPAND, but tissue size stays the same.
If Chondroblasts EXPAND, then Lacunae must EXPAND.
7/31/2019 Chapt 07 New
50/94
Hypertrophy of Chondrocytes
7-50
Chondrocytes EXPAND, but tissue size stays the same.
If Chondroblasts EXPAND, then Lacunae must EXPAND.If Lacunae EXPAND and tissue size stays the same,
then matrix must SHRINK
7/31/2019 Chapt 07 New
51/94
E d h d l O ifi ti
7/31/2019 Chapt 07 New
52/94
7-52
Endochondral OssificationStep 1.Ossification of the diaphysis to produce the primary ossification center:
a. Recall that hyaline cartilage is covered by perichondrium (dense irregular
CTP). This is where cartilage stem cells live. These cartilage stem cellschange their behavior: they become osteogenic cells. We now say thatthe perichondrium is a periosteum.
b. The osteogenic cells produce osteoblasts. The osteoblasts startproducing bony matrix at the models outer surface, creating a bony collar.
The bony collar starts in the middle of the diaphysis then extends to either
end.c. Chondrocytes deep inside the middle of the diaphysis of the model now
change their behavior: they undergo hypertrophy. As the cells enlarge, thecartilage matrix around them is reduced to thin walls. These walls becomecalcified NOT true bone. The calcified matrix causes the chondrocytesto die.
d. The calcified cartilage gets chewed up by osteoclasts thatinvade and the resulting cavity is invaded by blood vesselsand osteoblasts invade to produce true bone.
P i O ifi ti C t d
7/31/2019 Chapt 07 New
53/94
7-53
Primary Ossification Center andPrimary Marrow Cavity
Figure 7.10 (2-3)
Bony collar
Periosteum
2
Enlarging
chondrocytes
Primaryossificationcenter
Formation ofprimaryossification center,bony collar, andperiosteum
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Vascular invasion,formation of primarymarrow cavity, andappearance ofsecondaryossification center
3
Secondaryossificationcenter
Primarymarrowcavity
E d h d l O ifi ti
7/31/2019 Chapt 07 New
54/94
7-54
Endochondral Ossification
This is a 2 Step Process:
Step 1. Ossification of the diaphysis to form the primary ossificationcenter
Step 2. Ossification of the Epiphyses to form theSecondary Ossification Centers
E d h d l O ifi ti
7/31/2019 Chapt 07 New
55/94
7-55
Endochondral Ossification
This is a 2 Step Process:
Step 1. Ossification of the diaphysis to form the primary ossificationcenter
Step 2. Ossification of the Epiphyses to form the SecondaryOssification Centers
a. The bony collar extends over the epiphysis.
E d h d l O ifi ti
7/31/2019 Chapt 07 New
56/94
7-56
Endochondral Ossification
This is a 2 Step Process:
Step 1. Ossification of the diaphysis to form the primary ossificationcenter
Step 2. Ossification of the Epiphyses to form the SecondaryOssification Centers
a. The bony collar extends over the epiphysis.
b. Chondrocytes deep inside the epiphysis undergohypertrophy, the matrix becomes thin andcalcified, the cells die.
E d h d l O ifi ti
7/31/2019 Chapt 07 New
57/94
7-57
Endochondral Ossification
This is a 2 Step Process:
Step 1. Ossification of the diaphysis to form the primary ossificationcenter
Step 2. Ossification of the Epiphyses to form the SecondaryOssification Centers
a. The bony collar extends over the epiphysis.b. Chondrocytes deep inside the epiphysis undergo hypertrophy,
the matrix becomes thin and calcified, the cells die.
c. Osteoclasts invade and chew up the calcified
matrix, blood vessels invade then osteoblastsinvade to produce bone.
7/31/2019 Chapt 07 New
58/94
The Epiphyseal Plate is Essential
7/31/2019 Chapt 07 New
59/94
7-59
The Epiphyseal Plate is Essentialfor Bone Elongation
Figure 7.10 (4-6)
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Metaphysis
Diaphysis
Epiphysis
Cartilage
Metaphysis
Spongy bone
Marrow cavity
Compact bone
Periosteum
4 5 6
Secondarymarrow cavity
Bloodvessel
Secondaryossificationcenter
Bone at birth, withenlarged primarymarrow cavity andappearance ofsecondary marrowcavity in one epiphysis
Bone of child, withepiphyseal plate
Adult bone with asingle marrowcavity and closedepiphyseal plate
Epiphysealplate
Articularcartilage
Epiphysealline
Nutrientforamen
7/31/2019 Chapt 07 New
60/94
7/31/2019 Chapt 07 New
61/94
7/31/2019 Chapt 07 New
62/94
Interstitial Bone Growth
In bone elongation cartilage is replaced by bone
metaphysisis the name for the zone of
transition from cartilage to bone
7-62
Histology of Metaphysis
7/31/2019 Chapt 07 New
63/94
7-63
Histology of Metaphysis
Interstitial Growth is very similar to EndochondrialOssification.
Just one extra pre-step:
proliferation of chondrocytes prior to hypertrophy
Histology of Metaphysis
7/31/2019 Chapt 07 New
64/94
7-64
Histology of Metaphysis
Pneumonic: Remember: Pretty Hard CartilageOssifies
R stands for Reserve cartilage (the epiphyseal plate)
P stands for Proliferation Zone H stands for Hypertrophy Zone
C stands for Calcification Zone
O stands for Ossification Zone
Histology of Metaphysis
7/31/2019 Chapt 07 New
65/94
7-65
Histology of Metaphysis zone of reserve cartilage
typical hyaline cartilage farthest from marrow cavity
shows no sign of transforming into bone
zone of proliferation
chondrocytes multiply forming columns of flat lacunae
zone of hypertrophy
chondrocyteenlargement
matrix between lacunae becomes very thin
zone of calcification
mineral deposited in the matrix between columns of lacunae
zone of bone deposition (ossification)
chondrocytes die, osteoclasts dissolve the calcified cartilage,blood vessels enter, osteoblasts make bone
7/31/2019 Chapt 07 New
66/94
Fetal Skeleton at 12 Weeks
7/31/2019 Chapt 07 New
67/94
7-67
Fetal Skeleton at 12 Weeks
Figure 7.11
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Humerus
Ulna
Femur
Radius
Mandible
Scapula
Ribs
Pelvis Biophoto Associates/Photo Researchers, Inc.
Cranialbones
Vertebrae
7/31/2019 Chapt 07 New
68/94
What Causes Less Than
Typical Interstitial Growth?(Short Stature)
7-68
Dwarfism
7/31/2019 Chapt 07 New
69/94
7-69
Dwarfism
achondroplastic dwarfism long bones stop growing in
childhood Normal torso, short limbs
failure of cartilage growth in
metaphyses mutantdominant allele
pituitary dwarfism lack of growth hormone
normal proportions with shortstature
Figure 7.14
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
The McGraw-Hill Companies, Inc./Joe DeGrandis, photographer
7/31/2019 Chapt 07 New
70/94
7/31/2019 Chapt 07 New
71/94
Bone Remodeling
*Wolffs law of bone - architecture ofbone determined by mechanical stresses
Bone grows thickest where the most stress isfelt
Trabeculae and spicules align with the stressforce
Bone that does not feel as much stress growsthinner to minimize weight
7-71
Design of Spongy Bone
7/31/2019 Chapt 07 New
72/94
7-72
Design of Spongy Bone
Figure 7.6
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Greater trochanter
Compact bone
Head
Lines of stress
Shaft (diaphysis)
Trabeculae ofspongy bone
Robert Calentine/Visuals Unlimited
Calcium Homeostasis
7/31/2019 Chapt 07 New
73/94
7-73
Calcium Homeostasis
about 99% of bodys calcium stored in skeleton
hypocalcemia- blood calcium deficiency
causes excess excitability of muscle, tremors,spasms or tetany (inability to relax)
hypercalcemia- blood calcium excess
RARE
Symptoms: sluggish reflexes, depression
7/31/2019 Chapt 07 New
74/94
Calcium Homeostasis
7/31/2019 Chapt 07 New
75/94
7-75
Calcium Homeostasis hypercalcemiais rare
hypocalcemiahas a wide variety of causes
vitamin D deficiency
diarrhea
thyroid tumors
underactive parathyroids pregnancy and lactation
accidental removal of parathyroid glands during thyroid surgery
Homeostasis depends on a balance between dietaryintake, urinary and fecal loses, and exchanges betweenosseous tissue
Calcium Homeostasis
7/31/2019 Chapt 07 New
76/94
7-76
Calcium Homeostasis
regulated by three hormones:
Calcitriol := Vitamin D3 required to absorb Ca
Calcitonin:Decreases Blood Ca
Parathyroid hormone:Increases Blood Ca
Calcium Homeostasis
7/31/2019 Chapt 07 New
77/94
7-77
Calcium Homeostasis
regulated by three hormones:
Calcitriol := Vitamin D3 required to absorb Ca
Calcitonin:Decreases Blood Ca
Parathyroid hormone(PTH): Increases Blood Ca
Calcitriol(Activated Vitamin D3)
7/31/2019 Chapt 07 New
78/94
7-78
Ca c t o ( ct ated ta 3)
produced by sequential action of 3 organs:
skin liver kidneys
increases calcium absorption by small intestine
less calcium lost in urine
can also cause activation of osteoclasts: Ca released from bone
necessary for making bone
Deficiency causes abnormal softness of bones (rickets) inchildren and (osteomalacia)in adults
Calcitonin
7/31/2019 Chapt 07 New
79/94
7-79
Calcitonin
secreted bythyroid glandwhen blood calcium
concentration risestoo high
lowers blood calcium concentrationin two ways: osteoclast inhibition
osteoblast stimulation
important in children, MINOReffect in adults
reduces bone loss in women during pregnancy & lactation
Correction for Hypercalcemia
7/31/2019 Chapt 07 New
80/94
7-80
Co ect o o ype ca ce aCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Correction for hypercalcemia
Calcitoninsecretion
Blood Ca2+
excess
Blood Ca2+
returns tonormal
Reducedosteoclast
activity
Less boneresorption
Increasedosteoblast
activity
More bonedeposition
Figure 7.18a
Parathyroid Hormone (PTH)
7/31/2019 Chapt 07 New
81/94
7-81
Parathyroid Hormone (PTH) secreted by the parathyroid glandswhen sense low blood
calcium(glands found on the posterior surface of thyroid gland)
PTH raises calcium blood levelby four mechanisms raises the osteoclast population size
less calcium lost in urine
promotes synthesis of calcitriol in the kidneys inhibits bone deposition
PTH also helps build bone - sporadic injection or secretionof low levels of PTH causes bone deposition and can
increase bone mass
Correction for Hypocalcemia
7/31/2019 Chapt 07 New
82/94
7-82
Correction for HypocalcemiaCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(b) Correction for hypocalcemia
Blood Ca2+
deficiency
Parathyroidhormonesecretion
Increasedosteoclast
activity
Blood Ca2+
returns tonormal
More boneresorption
Less bonedeposition
Prevention ofhydroxyapatite
formation
More urinaryphosphateexcretion
Reducedosteoblast
activity
Conservationof calcium
Less urinarycalcium
excretion
Figure 7.18b
H l C t l f C l i
7/31/2019 Chapt 07 New
83/94
7-83
Hormonal Control of Calcium
calcitriol, calcitonin, and PTH maintain normalblood calcium concentration
Figure 7.17
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Calcium Intake and Excretion
Digestive tract
Kidneys
Fecal loss350 mg/day
Urinary loss650 mg/day
Calcitriol
CalcitriolPTH
Blood
Calcitonin(weak effect)
CalcitriolPTH
Bone
Absorption bydigestive tract
Filtrationby kidneys
Reabsorptionby kidneys
Deposition byosteoblasts
Resorption byosteoclasts
Dietary requirement1,000 mg/day
Ca2+
(9.210.4 mg/dL) HydroxyapatiteCa10(PO4)6(OH)2
Calcium carbonateCaCO3
Other Factors Affecting Bone
7/31/2019 Chapt 07 New
84/94
7-84
Other Factors Affecting Bone
Many hormones, vitamins, and growth factors affect
osseous tissue (examples:growth hormone, estrogen,and testosterone)
Use of anabolic steroidscauses growth to stop
epiphyseal plate closes prematurely Can result in abnormally short adult stature
Fractures and Their Repair
7/31/2019 Chapt 07 New
85/94
7-85
Fractures and Their Repair
fracturesclassified by structural characteristics
break in the skin =open fracture, akacompound fracture
displaced= ends of bones NOT aligned properly
direction of fracture line (linear=parallel to bone, vs. oblique, transverse)
number of pieces (1=incomplete, 2=complete, 3 or more=comminuted)
pathological fracture break in a bone weakened bysome other disease
bone cancer or osteoporosis
usually caused by stress that would NOT break a healthy bone
Types of Bone Fractures
7/31/2019 Chapt 07 New
86/94
7-86
yp
Figure 7.19
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(a) Nondisplaced
(c) Comminuted (d) Greenstick
a: Custom Medical Stock Photo, Inc.; c: Lester V. Bergman/Corbis; d: Custom Medical Stock Photo, Inc.
Healing of Fractures
7/31/2019 Chapt 07 New
87/94
7-87
gstages of healing bone fractures:
1. form blood clot (fracture hematoma) andform
granulation tissue blood capillaries, fibroblasts, macrophages, osteoclasts, and osteogenic
cells invade clot
2. soft callus formation formed by fibroblasts and chondroblasts depositing collagen and
fibrocartilage into granulation tissue
3. conversion to hard callus osteoblasts produce a bony collar in 6 weeks called a hard callus
acts as a temporary splint to join broken ends together
4. remodeling hard callus persists for 3 4 months
osteoclasts dissolve fragments of broken bone
osteoblasts deposit spongy bone to bridge to between the broken ends,later convert spongy compact bone, bone will be thicker in fracture area
uncomplicated fractures normally heal in 8 - 12 weeks, longer in elderly
7/31/2019 Chapt 07 New
88/94
7-88
Healing of Fractures
Figure 7.20
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fibrocartilage
Soft callusHematoma
Compact bone
1 2 3 4
Marrowcavity
Hematoma formationThe hematoma is convertedto granulation tissue by invasionof cells and blood capillaries.
Hard callus formationOsteoblasts deposit a temporarybony collar around the fracture tounite the broken pieces whileossification occurs.
Bone remodelingSmall bone fragments areremoved by osteoclasts, whileosteoblasts deposit spongybone and then convert it tocompact bone.
Soft callus formationDeposition of collagen andfibrocartilage converts granulationtissue to a soft callus.
Hardcallus
Spongy
bone
New bloodvessels
Treatment of Fractures
7/31/2019 Chapt 07 New
89/94
7-89
Treatment of Fractures Reduction = getting bones aligned properly
closed reductionbone fragments are manipulated intotheir normal positions without surgery
open reduction involves surgical exposure of the boneand the use of plates, screws, or pins to realign the
fragments
cast normally used to stabilize and immobilize healing bone
traction RARELY used ambulation (walking) encouraged to promote blood circulation/healing
to maintain alignment, may use traction in children to override muscles
electrical stimulation accelerates repair suppresses the effects of parathyroid hormone
orthopedics the branch of medicine that deals injuries and disorders of thebones, joints, and muscles
Fractures and Their Repairs
7/31/2019 Chapt 07 New
90/94
7-90
Fractures and Their Repairs
Figure 7.21
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
SIU/Visuals Unlimited; 7.22a: Michael Klein/Peter Arnold, Inc.
Osteoporosis
7/31/2019 Chapt 07 New
91/94
7-91
Osteoporosis osteoporosis the most common bone disease
severe loss of bone density
bones lose mass and become brittle affects spongy bone the most
subject to pathological fracturesof hip, wrist & vertebral column
kyphosis(widows hump) deformity of spine due to vertebral
bone loss, usually cervical vertebrae affected complications of loss of mobility are pneumonia and thrombosis
postmenopausal women at greatest risk begin to lose bone mass as early as 35 yoa
by age 70, average loss is 30% of bone mass in white women
risk factors - race, age, gender, smoking, diabetes mellitus, dietspoor in calcium, protein, vitamins C and D
best treatment isprevention- exercise and calcium intake
7/31/2019 Chapt 07 New
92/94
7/31/2019 Chapt 07 New
93/94
Osteoporosis
7/31/2019 Chapt 07 New
94/94
Osteopo os s estrogen maintains density in both sexes inhibits resorption
by osteoclasts testes and adrenals produce estrogen in men in women, rapid bone loss after menopause since estrogen blood
level drops below 30 ng/mL
osteoporosis is common in young female athletes with low
body fat causing them to stop ovulating and ovarianestrogen secretion is low
treatments estrogen replacement therapy (ERT) slows bone resorption, but
increases risk of breast cancer, stroke and heart disease
drugs Fosamax/Actonel destroys osteoclasts May cause loss of bone mass in mandible (lower jaw) and perhaps hip
PTH slows bone loss if given as daily injection Forteo (PTH derivative) increases density by 10% in 1 year
may promote bone cancer so use is limited to 2 years