biol 121 chp 6: the skeletal system: bone tissue
DESCRIPTION
This is a lecture presentation for my BIOL 121 Anatomy and Physiology I students on Chapter 6: The Skeletal System: Bone Tissue (Principles of Anatomy and Physiology, 14th Ed. by Tortora and Derrickson). Rob Swatski, Associate Professor of Biology, Harrisburg Area Community College - York Campus, York, PA. Email: [email protected] Please visit my website for more anatomy and biology learning resources: http://robswatski.virb.com/TRANSCRIPT
1
The Skeletal System: Bone Tissue
BIOL 121: A&P I Chapter 6
Rob Swatski Associate Professor of Biology
HACC – York Campus Textbook images - Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
2
3
Skeletal System Tissues
Bone Car)lage Dense CT Epithelium Adipose Nervous
4
5
FuncLons of Bone
Supports body
Protects so? )ssues
Muscle aAachment
site
6
FuncLons of Bone, cont.
Mineral storage &
homeostasis
Produces blood cells in red bone marrow
(hemopoiesis)
Energy storage in yellow bone marrow
7
8
Bone Marrow
9
10
Anatomy of a Long Bone
11
Anatomy of a Long Bone
Diaphysis
Epiphysis
Metaphysis
Epiphyseal plate
ArLcular carLlage
(b) Partially sectioned humerus
Medullary cavity in diaphysis
Compact bone
Spongy bone Epiphyseal line
Proximal epiphysis
Metaphysis
13
Anatomy of a Long Bone, cont.
Medullary (Marrow) cavity
Endosteum
Periosteum
Fibrous layer
Osteogenic layer
14
15
16
Histology of Bone Tissue
Compact bone
Spongy bone
Specialized bone cells
Extracellular matrix
17
18
Matrix
15% water, 30% collagen, 55% mineral salts
Calcium phosphate (hydroxyapa)te), calcium carbonate,
K, Mg
Collagen fiber skeleton
= tensile strength
CalcificaLon (MineralizaLon)
= hardness
19
20
4 Types of Bone Cells
Osteogenic cells
Osteoblasts
Osteocytes
Osteoclasts
21
Osteogenic Cells
= Osteoprogenitor cells
Undifferen)ated
Periosteum & endosteum
Develop into osteoblasts
22
Osteoblasts
Bone-‐building cells
Do not divide
Form bone matrix & secrete collagen fibers
Develop into osteocytes
23
Osteocytes
Mature bone cells
Maintain bone )ssue
No longer secrete matrix
24
25
Osteoclasts
Largest of the bone cells
Originate from fused monocytes
(wbc’s)
Bone resorpLon
26
27
Compact (Dense) Bone
Solid, hard, external layer
of bone
Forms diaphysis of long bones
Resists stresses of weight & movement
Arranged in units called osteons
28
Osteons
= Haversian systems
Osteocytes
Abundant vascular )ssue: blood vessels & lympha)cs
Nervous )ssue
(a) Osteons (haversian systems) in compact bone and trabeculae in spongy bone
Compact bone Spongy bone Periosteum
Medullary cavity
Outer circumferential lamellae
Interstitial lamellae Concentric
lamellae
Blood vessels
Canaliculi
Osteocyte
Lacuna
Periosteal vein Periosteal artery
Periosteum: Outer fibrous layer Inner osteogenic layer
Central canal
Compact bone
Spongy bone
Inner circumferential lamellae
Trabeculae
Medullary cavity
See Figure 6.3b for details
Perforating canal Perforating (Sharpey’s) fibers
Osteon
30
Osteon Histology
Concentric lamellae of matrix around central canal
Osteocytes inside lacunae
Canaliculi
IntersLLal lamellae
31
32
33
Spongy Bone No osteons
Consists of trabeculae
Supports red bone marrow
Reduces weight
Short, flat, irregular bones
Epiphyses of long bones
34
35
36
Blood Supply of Bone Periosteal arteries
Nutrient arteries
Epiphyseal arteries
Metaphyseal arteries
37
Bone FormaLon (OssificaLon)
Embryonic CT begins as mesenchyme
Template for ossifica)on
Intramembranous ossificaLon
Endochondral ossificaLon
38
39
Intramembranous OssificaLon
Forms flat bones of skull & mandible
“Jelly sandwich”
Mesenchyme à Osteogenic cells
Ossifica)on center
Osteoblasts à Matrix (Calcifica)on)
Osteoblasts à Osteocytes
Osteogenic cells
40
41 Osteoblasts
42
Intramembranous OssificaLon, cont.
Calcifying matrix joins to form trabeculae
Spongy bone forms around red bone marrow
Surface mesenchyme à Periosteum
Superficial spongy bone à Compact bone
43
Flat bone of skull
Mandible
Blood capillary
Ossification center
Mesenchyme
Osteoblast
Collagen fiber Development of ossification center: osteoblasts secrete organic extracellular matrix
1
Osteocyte in lacuna
Calcification: calcium and other mineral salts are deposited and extracellular matrix calcifies (hardens)
2
Canaliculus
Osteoblast
Newly calcified bone extracellular matrix
Mesenchyme condenses
Formation of trabeculae: extracellular matrix develops into trabeculae that fuse to form spongy bone
3
Blood vessel Spongy bone trabeculae
Osteoblast
Periosteum
Compact bone tissue
Spongy bone tissue
Compact bone tissue
Development of the periosteum: mesenchyme at the periphery of the bone develops into the periosteum
4
45
Endochondral OssificaLon
Forms longs bones
Replaces car)lage with bone
Six step process
Begins with forma)on of carLlage model
46
1. Development of CarLlage
Model
Originates from mesenchyme
Basic shape and length of bone
Hyaline car)lage & chondroblasts
Perichondrium
47
2. Growth of CarLlage Model
Chondrocytes divide & matrix forms
IntersLLal growth
ApposiLonal growth
Mid-‐region cells burst & lower pH
Destroys chondrocytes & triggers calcifica)on
48
3. Development of Primary OssificaLon
Center
Perichondrium à Periosteum
Forms periosteal bone collar
Nutrient artery penetrates center of bone model
Periosteal bud brings osteoblasts & osteoclasts to
center
49
50
4. Development of Medullary
Cavity
Osteoblasts deposit matrix over calcified car)lage
Form trabeculae of spongy bone
Osteoclasts form medullary cavity
51
5. Development of Secondary OssificaLon
Center Blood vessels enter uncalcified epiphyses
Spongy bone develops
52
6. FormaLon of ArLcular CarLlage
& Epiphyseal Plate
Epiphyseal car)lage does not ossify
Remains as arLcular carLlage
Epiphyseal (Growth) plate also remains as car)lage
Source of inters))al growth
Development of cartilage model: mesenchymal cells develop into chondroblasts, which form the cartilage model.
1
Proximal epiphysis
Diaphysis
Distal epiphysis
Hyaline cartilage
Perichondrium
Endochondral Ossification - Overview
Growth of cartilage model: growth occurs by cell division of chondrocytes.
2
Uncalcified extracellular matrix
Calcified extracellular matrix
Nutrient artery
Periosteum
Primary ossification center
Spongy bone
Development of primary ossification center: in this region of the diaphysis, bone tissue replaces most of the cartilage.
3
Uncalcified extracellular matrix
Development of the medullary (marrow) cavity: bone breakdown by osteoclasts forms the medullary cavity.
4
Calcified extracellular matrix
Periosteum
Medullary cavity
Nutrient artery and vein
Development of secondary ossification centers: these occur in the epiphyses of the bone.
5
Secondary ossification center
Uncalcified extracellular matrix
Epiphyseal artery and vein
Articular cartilage
Spongy bone
Epiphyseal plate
Formation of articular cartilage and epiphyseal plate: both structures consist of hyaline cartilage.
6
Endochondral Ossification – Overview, cont.
(b) Twelve-week fetus. The red areas represent bones that are forming (calcified). Clear areas represent cartilage (uncalcified).
56
Epiphyseal (Growth) Plate
Chondrocytes produce carLlage on epiphyseal side
Car)lage replaced by bone on diaphyseal side
Plate closes at age 18-‐25
Chondrocytes stop dividing
Bone replaces car)lage (epiphyseal line)
57
4 Zones of Epiphyseal Plate
Zone of ResLng CarLlage
Zone of ProliferaLng CarLlage
Zone of Hypertrophic CarLlage
Zone of Calcified CarLlage
Epiphysis
(c) Lengthwise growth of bone at epiphyseal plate
EPIPHYSEAL (GROWTH) PLATE:
Zone of resting cartilage Zone of proliferating cartilage Zone of hypertrophic cartilage
Zone of calcified cartilage
Diaphysis
Articular cartilage
New chondrocytes are formed
Old chondrocytes are replaced by bone
New diaphysis
59
Zone of ResLng CarLlage Anchors growth plate
to bone
60
Zone of ProliferaLng CarLlage
Rapid cell division (stacks of coins)
61
Zone of Hypertrophic CarLlage Cells enlarge &
remain in columns
62
Zone of Calcified CarLlage Thin zone – mostly
dead cells
Osteoblasts & osteoclasts ac)ve
63
Calcified CarLlage
Ridges in periosteum create groove for periosteal blood vessel.
1
Periosteal ridges
Periosteum
Periosteal blood vessel
Perforating canal
Groove
Periosteal ridges fuse, forming an endosteum-lined tunnel.
2
Endosteum
Tunnel
Osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon.
3
Endosteum
Bone grows outward as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels.
4
Circumferential lamellae Periosteum
New osteon
Central (haversian) canal
Ridges in periosteum create groove for periosteal blood vessel.
1
Periosteal ridges
Periosteum
Periosteal blood vessel
Perforating canal
Groove
Periosteal ridges fuse, forming an endosteum-lined tunnel.
2
Endosteum
Tunnel
Osteoblasts in endosteum build new concentric lamellae inward toward center of tunnel, forming a new osteon.
3
Endosteum
Bone grows outward as osteoblasts in periosteum build new circumferential lamellae. Osteon formation repeats as new periosteal ridges fold over blood vessels.
4
Circumferential lamellae
Periosteum
New osteon
Central (haversian) canal
Medullary cavity
Bone formed by osteoblasts
Bone destroyed by osteoclasts
Infant Child Young adult
Adult
(b) Macroscopic changes
70
Factors AffecLng Bone
Growth: Nutri&on
Calcium & Phosphorus
Vitamin C à collagen
Vitamins K & B12 à protein synthesis
71
Factors AffecLng Bone
Growth: Hormones
Insulinlike Growth Factors (IGFs)
Thyroid hormone, hGH, insulin
Estrogen & testosterone
72
Bone Homeostasis
Remodeling
Osteoclasts
Osteoblasts
73
OrthodonLcs
74
The Effects of Corsetry
75
Bone Fractures
Greens)ck
Impacted
Open
Comminuted
PoA
Colles’
Stress
Ulna
Greenstick
Radius
Wrist bones
Humerus
Impacted
Humerus
Open (Compound)
Radius
Ulna
Humerus
Comminuted
Tibia
Pott
Fibula
Ankle bones
Ulna
Colles’
Radius
Wrist bones
82
Fracture Repair
Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
Periosteum
Fracture hematoma
Fibrocartilaginous callus (soft)
Reactive phase: formation of fracture hematoma
1 Reparative phase: fibrocartilaginous callus formation
2a Reparative phase: bony callus formation
2b Bone remodeling phase
3
New blood vessel
Spongy bone trabeculae
Bony (hard) callus
Healed fracture
84
1. Reac&ve Phase: FormaLon of fracture hematoma (clot)
85
2. Repara&ve Phase: FibrocarLlaginous callus formaLon
86
3. Repara&ve Phase: Bony callus formaLon
87
4. Bone Remodeling Phase
88
Calcium Homeostasis & Bone Tissue
Skeleton = Calcium reservoir
Nerve & muscle fiber func)on
Blood clohng cascade
Enzyme func)on
9-‐11 mg Ca+2/100 ml plasma
89
Hormonal RegulaLon of
Ca+2 Parathyroid Hormone
(PTH)
Calcitriol
Calcitonin
STIMULUS
CONTROLLED CONDITION Blood calcium (Ca2+) level
RECEPTORS
CONTROL CENTER Parathyroid hormone gene
EFFECTORS
RESPONSE Increase in blood Ca2+ level
Osteoclasts increase
bone resorption
Kidneys retain Ca2+ in blood, excrete phosphate in urine, and produce calcitriol
Parathyroid gland cells
Return to homeostasis when response brings blood Ca2+ level back to normal
Disrupts homeostasis by decreasing
Detect lowered Ca2+ concentration which increases production of cyclic AMP
Input
Output Gene “turned on” which increases release of PTH
Osteoclasts Kidneys
91
How do they do this?
92
Aging & Bone Tissue
Demineraliza)on
Osteoporosis
Reduced protein synthesis
Less collagen
Less growth hormones
93
94
Disorders of Bone
OssificaLon
RickeAs
Osteomalacia
95 The End