7Microanatomy Lect: Bone & Histo (Chapter 8)

Front 1

Osteoblasts (OB) are Cuboidal to columnar bone building cells
Deposit ___ (clear region between cells), which then becomes ___ .

Back 1

-osteoid
-calcified bone

Front 2

Osteocytes (OC)

Back 2

Mature bone maintaining cell trapped in lacunae

Front 3

Osteoclasts (OCL)

Back 3

Large multinucleated cells responsible for bone resorption

Front 4

Calcium phosphate homeostasis is regulated by 3 hormones:

Back 4

parathyroid hormone (PTH)
calcitonin
calcitriol (vitamin D)

Front 5

Parathyroid hormone (PTH) does what? How?

Back 5

-increases bone resorption, increases serum Ca+ levels
-Binds to receptors on osteoblasts. Osteoblasts then secrete a protein (osteoclast-stimulating factor/RANKL), which binds to a receptor on osteoclasts/RANK, causing osteoclasts to resorb bone and thereby increase serum calcium concentration
-PTH inhibits OPG production; (OPG inhibits maturation of osteoclasts)
-PTH can, when given as a drug (Forteo, recombinant human PTH), act to build bond as a treatment for osteoporosis – this is counterintuitive and is not well understood by researchers.
-Can also cause osteocytes to resorb bone (osteocytic osteolysis)

Front 6

Calcitonin does what? Where?

Back 6

-inhibits osteoclasts --> decreased bone resorption --> inhibits Calcium release from bone --> decreases serum Ca+
-from the parafollicular cells of the thyroid

Front 7

Vitamin D :

Back 7

-Increases Ca++ and phosphate absorption in the gut
-increases bone resorption, taking Ca++ and phosphate from old bone in order to mineralize new bone
-reduced excretion of Ca++

Front 8

-In osteoporosis, bones ___
-Who is most at risk?
-Prevention & treatment should include:

Back 8

-lose mass (they lose organic matrix and the mineral component of bone)
-Postmenopausal women
-Weight bearing exercise
Vitamin D
Calcium intake early in life and throughout life
Vitamin K from green leafy vegetables

Front 9

-Estrogen maintains ___
-it inhibits ___
-Where is estrogen produced in men?

Back 9

-bone density in both sexes
-bone resorption
-testes and adrenals

Front 10

There is a rapid loss of bone density under what two conditions:

Back 10

-after menopause
-during periods of disuse during immobilizaton

Front 11

Bone, a specialized ___ tissue characterized by a ___ extracellular matrix

Back 11

-connective
-mineralized

Front 12

The predominant structural protein of bone

Back 12

Type I collagen

Front 13

Both collagen and the ground substance becomes mineralized with calcium phosphate in the form of

Back 13

hydroxyapatite crystals (Ca10 (PO4)OH 2 min

Front 14

vitamin K dependent Ca binding protein that is 15-20% of the non collagen protein of bone

Back 14

Osteocalcin (also called Gla protein and abrieviated MGP)

Front 15

Bone morphogenic proteins (BMPs) induce the differentiation of ___ into ___.
Recombinant BMP can be used by surgeons after spinal fusions and repair of bone defects

Back 15

-mesenchymal cells
-osteoblasts

Front 16

Back 16

Front 17

A bone (femur, radius, ulna, etc…) is made up of:
-
-
-
-
-
-

Back 17

Bone tissue
Hemopoieitic tissue
Fat tissue
Blood vessels
Nerves
Hyaline cartilage (synovial joints)

Front 18

Source of pain from a bone fracture

Back 18

Periosteal nerve

Front 19

Back 19

Front 20

Classification of the following bones:
-vertebrae
-skull
-carpals
-humerus

Back 20

-irregular
-flat
-short
-long

Front 21

What sites are used for marrow transplantation and biopsy?

Back 21

-iliac crest & sternum

Front 22

Site of developing blood cells and is found throughout the body during development and growth

Back 22

red bone marrow

Front 23

In the adult most of the red marrow is replace by ___ (except in the ___)

Back 23

-yellow (fatty) marrow
-sternum and iliac crest

Front 24

if the need arises (after blood loss) what can convert to red blood cell producing marrow?

Back 24

-yellow (fatty) marrow

Front 25

Types of bone tissue:
-Compact (___)
-Spongy (___, ___)

Back 25

-cortical
-cancellous, trabecular

Front 26

Under the microscope,
Both compact bone and the thicker trabeculae of spongy bone have ____

Back 26

Haversian systems

Front 27

Concentric lamellae and the Haversion canal constitute the

Back 27

Osteon

Front 28

Volkmann’s canals link

Back 28

Haversion canals

Front 29

interstitial lamellae are the result of ___ and lie between complete osteons

Back 29

bone remodeling

Front 30

Back 30

Front 31

Periosteum: covers external surfaces of bones; has two parts:
(1) an outer fibrous layer of ___
(2) an inner cellular layer of ___.

Back 31

-dense C.T.
-osteoprogenitor (The cells of the inner layer can differentiate into osteoblasts.)

Front 32

Endosteum: lines internal surfaces; thin layer of ___

Back 32

osteoprogenitor cells

Front 33

Collagen fibers of the periosteum run ___ to the surface of a bone

Back 33

parallel

Front 34

Sharpey’s fibers are ___ fibers found at the site of a ___ into bone. These fibers, which run through the periosteum, are continuous with the ___ of bone tissue

Back 34

-collagen
-tendon insertion
-collagen fibers

Front 35

Gound section or EM?

Back 35

Ground section

O – osteon

HC – Haversion canal

VC – Volkman’s canal

CL – circumferential lamellae

IL – interstitial lamellae

Front 36

What is it? Where is it? What is it doing?

Back 36

Osteocyte in lacunae
Osteocytes extend cytoplasmic processes into canaliculi
can be visualized in the electron micrograph

Front 37

Lacunae -

Back 37

a cavity, space, or depression, especially in a bone, containing cartilage or bone cells.

Front 38

Back 38

Front 39

Haversian systems (osteons) consist of:
___ made of collagen fibers and bone matrix, parallel collagen fibers

Back 39

-Concentric lamellae

Front 40

Haversian systems (osteons):
___ containing osteocytes located between or in the lamellae

Back 40

-Lacunae

Front 41

Haversian systems (osteons):
___ are small canals allowing the extended cytoplasmic processes of an osteocytes trapped in lacunae to make contact with other osteocytes and communicate via ___

Back 41

-Canaliculi
-gap junctions

Front 42

Haversian systems (osteons): The center of a Haversian system is an ___-lined canal containing blood vessels, nerves and loose connective tissue

Back 42

endosteum

Front 43

Haversian systems run ___ to the long axis of the bone. They are not restricted to compact bone and can also be observed in the thicker trabeculae of ___.

Back 43

-parallel
-spongy bone

Front 44

What provides communication between haversian systems and marrow cavity? They run ___ to Haversian systems

Back 44

-Volkmann's canals
-perpendicular

Front 45

Outer circumferential lamellae: located under

Back 45

periosteum

Front 46

Inner circumferential lamellae: located around

Back 46

marrow cavity

Front 47

Interstitial lamellae: remnants of remodeled

Back 47

Haversian systems

Front 48

Decalcified H & E Bone Section
Compare and contrast:
-# of cells/unit area
-matrix layered or not

Back 48

Immature bone (woven)
More cells
Matrix is not layered (osteons)
v.s.

Mature (lamellar) compact bone
Fewer osteocytes per unit area
Osteons with concentric lamellae
Interstitial lamellae

Front 49

In adults, ___ is found in the tooth sockets, near the sutures of the flat bones of the skull and at the insertions of some tendons.

Back 49

primary bone

Front 50

Two stages of bone formation

Back 50

primary and secondary

Front 51

Primary (___) bone:
Immature bone. characterized by an irregular array of ___ fibers, a low mineral content and a greater number of ___.

Back 51

-woven
-collagen
-osteocytes

Front 52

Secondary (lamellar) bone:
More typical of ___. Collagen fibers are numerous and organized into parallel or concentric ___ around ___

Back 52

-adults
-lamellae
-blood vessels

Front 53

Back 53

pink = bone
clear = osteoid

Front 54

-Arrows
-Light blue
-Dark blue

Multinucleated osteoclast on the resorption side of this trabecula has a ___ border, depression in bone is called ___; clear area surrounding this is rich in actin filaments for attachment to bone matrix

Back 54

Special Stain: Mallery-Azan

Arrows are pointing to inactive bone lining cells/osteoprogenitor cells (flat/thin morphology)

Light blue is calcified cartilage and dark blue is bone

Multinucleated osteoclast on the resorption side of this trabecula has a ruffled border, depression in bone is called Howship’s lacunae clear area surrounding this is rich in actin filaments for attachment to bone matrix

Front 55

Osteoprogenitor cells:
have a ___ cytoplasm, have a ___-like appearance and give rise to ___

Back 55

-basophilic
-fibroblast
-osteoblasts

Front 56

Osteoblasts:
secrete ___ (organic matrix); they are located at ___; they are ___ or columnar shaped cells

Back 56

-osteoid
-bone surfaces
-cuboidal

Front 57

Osteoclasts:
derived from the fusion of blood-derived ___ , thus creating large ___ cells

Back 57

-monocytes
-multinucleated

Front 58

Osteoclasts:
resorb bone matrix and in the process create depressions in the bone surface termed ___ . They are characterized by a ___ border at the bone resorbing end of the cell.

Back 58

-Howship's lacunae
-ruffled

Front 59

Osteoclasts:
Around the ruffled border is a region devoid of organelles, but rich in actin microfilaments. This ___ allows attachment of the osteoclast to the ___ and creates a microenvironment into which the cell secretes:

Back 59

-clear zone
-bone matrix
-H+ (via an H+ ATPase) & Cl-, which dissolves inorganic matrix
Lysosomal enzymes (collagenase, gelatinase, metalloproteinase) degrade organic matrix (collagen & other proteins).

Front 60

Bone Matrix
Organic (osteoid): collagen ___ fibers,___ and some ___ (sialoprotein and osteocalcin)
These proteins play a role in ___

Back 60

- type I
- proteoglycans
-glycoproteins
-binding Ca+

Front 61

Bone Matrix
Inorganic: calcium and phosphorus in the form of ___ and amorphous ___

Back 61

-hydroxyapatite crystals
-calcium phosphate

Front 62

Osteomalacia - ___ impaired; (soft bones) due to ___ deficiency, which causes deficient ___ absorption in the gut.

Back 62

-mineralization of bone matrix
-vitamin D
-calcium & phosphorus

Front 63

In children/growing bone vitamin D deficiency leads to

Back 63

Rickets

Front 64

Osteogenesis imperfecta, “Brittle Bone Disease”
Genetic disorder of ___ collagen characterized by repeated ___ after minor trauma, thin skin, weak tendons, and in certain subtypes blue sclerae

Back 64

-type I
-fractures

Front 65

Osteoporosis - decreased ___ - frequent problem of post-menopausal women. However, the___ in osteoporosis is normal. Can also occur in patients who are confined to bed for long periods. The bone is characterized by ___ than normal bone.

Back 65

-bone mass
-ratio of minerals to organic matrix
-spicules that are thinner

Front 66

Vitamin C deficiency
Poor bone growth and fracture repair due to impaired ___ synthesis

Back 66

collagen

Front 67

There are two distinct ways in which bones can develop:

Back 67

-Intramembranous ossification
-Endochondral ossification (within cartilage)

Front 68

Intramembranous Ossification
ECT – embyronic connective tissue
___ differentiate into osteoblasts.
This site of osteoblast formation becomes a ___ center

Back 68

-mesenchymal cells
-primary ossification

Front 69

Intramembranous Ossification
Osteoblast lay down ___, which encapsulates osteoblasts and calcifies. Osteoblasts become ___ located in lacunae. Spicules of ___ form and these grow together forming trabeculae.
Compact bone forms outer plates. Inner bone around the developing marrow cavity becomes spongy bone.

Back 69

-bone matrix
-osteocytes
-woven bone

Front 70

Endochondral ossification (___):
Mode of development of ___ and most short bones

Back 70

-within cartilage
- long bones

Front 71

Endochondral ossification
Hyaline cartilage model of bone, forms in the embryo and is ___ by bone during development.

Back 71

replaced
(NOTE: Hyaline cartilage does not become bone.)

Front 72

Endochondral ossification consists of two phases:

Back 72

-Hypertrophy and degeneration of chondrocytes
-Osteogenic bud of osteoprogenitor cells and blood vessels penetrates the space left by the dead chondrocytes

Front 73

Back 73

(1) Formation of hyaline cartilage model
Primary ossification center
(2) Bone collar formation is the first sign of ossification
(3) cartilage matrix in the shaft begins to calcify
(4) Blood vessel invasion and connective tissue cell erode the calcified cartilage, creating a primary marrow cavity
Osteoblasts secrete matrix on cartilage scaffold
Secondary ossification center

Front 74

Bone collar formation, is actually a form of ___, i.e. bone formation within the perichondrium.

Back 74

intramembranous bone formation

Front 75

Formation of the primary ossification center (pre- or postnatal)?

Back 75

prenatal; Formation of secondary ossification centers is postnatal

Front 76

Epiphyseal plate (connects epiphysis & diaphysis) – allows for ___

Back 76

Front 77

Bone formation is taking place at which surface of the epiphyseal plate?

Back 77

Bone formation is taking place at both the epiphyseal and diaphyseal surface of the epiphyseal plate. Growth rate is much greater on the diaphyseal side

Front 78

What advances and resorbs bone in a bone remodeling unit?

Back 78

Cutting cone (osteoclasts)

Front 79

What deposits new bone in a bone remodeling unit?

Back 79

Closing cone (osteoblast)

Front 80

In bone growth and remodeling does the epiphyseal plate enlarge or decrease in size?

Back 80

epiphyseal plate maintains a constant thickness during growth phase

Front 81

Growth in width (___)
due to bone formation by osteoprogenitor cells within the inner ___ around the diaphysis. This is actually a form of ___.
the marrow cavity increases in diameter due to the resorption of bone from internal surfaces by osteoclasts

Back 81

-appositional growth
-periosteum
-intramembranous ossification.

Front 82

Pituitary Dwarfism
Deficiency of ___ during the developing years leads to failure of ___.

Back 82

-growth hormone (somatotropin)
-bone growth

Front 83

Gigantism
Excess ___ during the developing years (prior to the closure epiphyseal plate) leads to an abnormal increase in the length of bones.

Back 83

growth hormone

Front 84

Acromegaly
Excess ___ in ___ leads to thickening of the bones since the growth (epiphyseal) plates have already closed.

Back 84

-growth hormone
-adulthood

Front 85

Fracture Repair (___ weeks):
1. A ___ forms at site of fracture

2. ___ (granulation tissue) of periosteum and endosteum proliferate

3. ___ forms in this connective tissue

4.___ forms at site by both endochondral and intramembranous bone formation

5. ___ (dense CT and cartilage) temporarily unites fracture

6. ___ from the periosteum divide and become ___, they invade the callus and deposit new bone

7. ___ occurs with healing (spongy bone is replaced with compact bone)

Back 85

-6-12
1. blood clot
2. connective tissue
3. hyaline cartilage
4. primary bone
5. bone callus
6. Osteoprogenitor cells --> osteoblasts
7. remodeling

Front 86

The interaction of the RANK receptor with RANK ligand (RANKL) is necessary for

Back 86

osteoclast differentiation