Histology Bone

Front 1

Bone is a ______ CT. (It is like cartilage but with _____.)

Back 1

Vascular
Blood

Front 2

What are the 4 types of bone cells?

Back 2

Osteoprogenitory cells
Osteoblasts
Osteoclasts
Osteocytes

Front 3

Osteoprogenitor cells-
Aka?
Give rise to?
Appearance and why?
Staining?

Back 3

Osteoprogenitor cells are also called preosteoblasts.

They give rise to osteoblasts.

Because they do not make bone matrix, they do not have many organelles and are flat in appearance.
Basophilic

Front 4

Where are osteoprogenitor cells located?

Back 4

On bone surfaces. (Like osteoblasts)

Front 5

These cells produce organic bone matrix (collagen and non-collagenous proteins).

Back 5

Osteoblasts

Front 6

Osteoblasts-
Appearance?
Staining?

Back 6

cuboidal cells with an abundance of rER and a prominent Golgi

Their cytoplasm stains eosinophilic, although osteoblasts in general are basophilic because you can see very little of their cytoplasm.

Front 7

Where are osteoblasts located?

Back 7

Located on bone surfaces, both inside and outside the bone.

Front 8

When does an osteoblast become an osteocyte?

Back 8

Once the osteoblast becomes surrounded by the matrix it has synthesized, it is called an osteocyte.

Front 9

What type of bone cell is the most prevalent? What type of collagen does it make?

Back 9

Osteoblasts

Make Type I and Type V Collagen.

Front 10

What happens to an osteocytes structure when it becomes an osteocyte?

Back 10

It loses many of its organelles. There is little rER of Golgi in an osteocyte.

Front 11

What does an osteocyte look like?

Back 11

These cells are flat or oval and lie in lacunae in the bone matrix bathed by extracellular fluid.

Front 12

Are osteocytes involved in the production of bone matrix?

Back 12

Not to any significant extent but they are involved in the maintenance of bone matrix.

Front 13

What type of bone cell has thin cytoplasmic processes that extend from the cell body? Why? Where do they go?

Back 13

Osteocytes.

Osteocytes have very thin cytoplasmic processes that extend from the cell body and make contact through gap junctions with other osteocytes. The processes run in tiny channels in the matrix called canaliculi. This is how bone cells get nutrition.

Front 14

What does an osteoblast secrete?

Back 14

Collagen, ground substance and osteoid.

Front 15

What is osteoid?

Back 15

ground substance plus fibers

Front 16

These bone cells are large and multinucleated.

Back 16

Osteoclasts

Front 17

Osteoclasts-
Function?
Formed from?
Location?

Back 17

Reabsorb bone matrix.
Formed from cells of the mononuclear/phagocytic line.
Found on bone surfaces.

Front 18

How do osteoclasts stain and why?

Back 18

Aciophilic and have a foamy cytoplasm.
Because they're making lots of lysosomes (which are release into the extracellular space) to actively reabsorb bone.

Front 19

Where are osteoclasts most active?

Back 19

Very active around the growth plate. (Seems counter-intuitive but as soon as bone is laid down it is gobbled back up so that you can put more down in its place to elongate the marrow cavity.)

Front 20

What separates bone from cartilage?

Back 20

Bone matrix

Front 21

What is the ground substance of bone?

Back 21

Osteoid (Organic Matrix)

Front 22

What is the Osteoid (Organic Matrix) made of?

Back 22

Proteoglycans and Glycoproteins (osteonectin).

Front 23

What GAGs are contained in the osteoid?

Back 23

Chondroitin Sulfate
Keratin Sulfate

Front 24

What non-collagenous proteins are in the Osteoid (Organic Matrix) and what are their functions?

Back 24

Osteonectin- anchors collagen to the bone mineral

Osteocalcin- a calcium-binding protein

Front 25

What is the Inorganic Matrix and how is it usually arranged?

Back 25

The osteoid when it becomes mineralized by the deposition of crystals of hydroxyapatite on the collagen fibers. The crystals tend to be oriented in the same direction as the collagen fibers.

Front 26

What type of Collagen Fibers are found in bone?

Back 26

Type I and Type V.

Front 27

Vitamin ____ is required for calcification.

Vitamin ____ is required for the synthesis of collagen.

Back 27

Vitamin D

Vitamin C

Front 28

Why is Vitamin D required in bone formation?

Back 28

Required for calcification.

Front 29

Why is Vitamin C required in bone formation?

Back 29

Required for the synthesis of collagen.

Front 30

What is the Periosteum?

Back 30

The vascular, noncalcified covering on the outside of a bone.

Front 31

Where is the Periosteum located?

Back 31

On the outside of a bone except at articular surfaces.

Front 32

What are Sharpey's Fibers?

Back 32

Type I Collagen fibers that anchor the periosteum to the bone as well as the periosteum to dense CT (deep fascia).

Front 33

How many layers are in the Periosteum and what are they?

Back 33

Two layers.
1) Outer Fibrous Layer
2) Inner Osteogenic Layer

Front 34

Outer Fibrous Layer

Back 34

Outer layer of Periosteum
Made of dense Type I collagen fibers and fibroblasts

Front 35

Inner Osteogenic Layer

Back 35

Inner layer of Periosteum
Made of osteoprogenitor cells and osteoblasts

Front 36

What is the Endosteum?

Back 36

The bone's cell lining that covers all the interior surfaces of bone (marrow cavity, Haversian canals, etc..)

Front 37

What types of cells are found in the Endosteum?

Back 37

The cells of the endosteum include osteoprogenitor cells and osteoblasts but not osteocytes.

Front 38

This is a thin, specialized CT that lines marrow cavities.

Back 38

Endosteum

Front 39

This area of bone is the source of osteoprogenitor cells and osteoblasts for bone growth and repair.

Back 39

Endosteum

Front 40

Histologically, how many types of bone are there and what are they?

Back 40

Two types.
1) Primary (immature, woven) bone
2) Secondary (mature, lamellar) bone

Front 41

Primary bone-
Collagen organization?
Staining?
Mineral content?
Cells?

Back 41

The collagen fibers run in random directions.
The matrix stains unevenly and may have basophilic regions.
Its mineral content is lower than secondary bone.
It has more cels per unit of calcified bone.

Front 42

When would you see Primary bone?

Back 42

You would see it if you were looking at a healing fracture.

Front 43

Secondary Bone-
Collagen organization?
Staining?
Types?

Back 43

There is an orderly arrangement of collagen fibers into concentric rings or lamellae.
The matrix stains deeply acidophilic.
Two types- Compact and Spongy

Front 44

Compact bone

Back 44

Dense, outer portion of bone

Front 45

Spongy bone

Back 45

meshwork of trabeculae in interior of bone

Front 46

What is an osteon?

Back 46

Circling of osteocytes around a central vessel

Front 47

What can connect Haversion canals?

Back 47

can connect neighboring vessels via Volkmanns Canal

Front 48

In spongy bone, what is the arrangement of trabeculae? How do these respond to stress?

Back 48

Trabeculae follow the lines of stress and can realign if the direction of stress changes.

Front 49

What makes up spongy bone?

Back 49

Made up of trabeculae which are organized to provide maximum strength.

Front 50

The long axis of the osteon is ____ to the long axis of the bone.

Back 50

Parallel

Front 51

If trabeculae are sufficiently thick, they can contain _____?

Back 51

Osteons

Front 52

Haversian System aka ?

Back 52

Osteon

Front 53

What is the organization of compact bone?

Back 53

Outer Circumferential Lamellae- below the periosteum
Inner Circumferential Lamella- adjacent or next to the marrow cavity
The rest of bone is organized as Haversian canal systems.

Front 54

What is in a Haversian Canal?
What lines it?
What surrounds it?

Back 54

Contains blood vessels and nerves.
Lined with endosteum.
Surrounded by rings of osteocytes and bone matrix

Front 55

What connects osteocytes of adjacent lamellae?

Back 55

Canaliculi

Front 56

What are interstitial lamellae and how are they formed?

Back 56

Irregularly shaped bits of Haversian systems in between completely formed systems.
Represent Haversian systems that have been destroyed by growth and remodeling.

Front 57

This completely surrounds the entire circumference of the bone just beneath the periosteum.

Back 57

Outer circumferential lamellae

Front 58

What are the two ways that bone forms in the fetus?

Back 58

Endochondrial Ossification
Intramembranous Ossification

Front 59

_____ ossification uses a cartilage model. ____ ossification does not.

Back 59

Endochondrial ossification
Intramembranous ossification

Front 60

Most bones of the body form by this method.

Back 60

Endochondrial Ossification (cartilage model)

Front 61

____ cartilage serves as a scaffold for bone development.

Back 61

Hyaline

Front 62

What are the step in endochondral ossification leading the the formation of the primary center of ossification?

Back 62

1) Mesenchyme condenses and differentiates into hyaline cartilage chondrocytes. These begin to lay down cartilage matrix.
2) The mesenchyme surrounding the cartilage model becomes the Perichondrium.
3) A bony collar forms under the periochondrium of the diaphysis. The perichondrium surrounding the bony collar becomes the Periosteum.
4) The matrix of the diaphysis becomes calcified and is partially reabsorbed.
5) The primary center of ossification is formed.

Front 63

How does the matrix become calcified in endochondral ossification?

Back 63

Chondrocytes of the diaphysis become hypertrophic and place alkaline phosphatase into the surrounding matrix. This blocks diffusion of nutrients and causes them to undergo apoptosis. The matrix in this area becomes calcified and is partially reabsorbed.

Front 64

How is the primary center of ossification formed in endochondral ossification?

Back 64

A periosteal bud of capillaries invades the degenerating cartilage matrix. Osteoprogenitor cells carried in by the periosteal bud differentiate into osteoblasts which lay down osteoid over degenerating cartilage matrix.

Front 65

Is all hyaline cartilage in endochondral ossification turned to bone?

Back 65

All hyaline cartilage in this model is eventually turned into bone EXCEPT at the epiphysis where it is now called articular cartilage.

Front 66

This is the main site of endochondral ossification.

Back 66

Diaphysis

Front 67

What condition is caused by a deformity of cartilage at the growth plate?

Back 67

Rickets

Front 68

Where is the secondary center of ossification formed?

Back 68

In the epiphyses.

Front 69

What persists between the epiphysis and diaphysis? What is it made of?

Back 69

Epiphyseal plate
Hyaline cartilage

Front 70

What are the five zones in the epiphyseal plate (from epiphysis to diaphysis)?

Back 70

1. Zone of resting (reserve) cartilage
2. Zone of Proliferation
3. Zone of hypertrophy
4. Zone of calcification
5. Zone of ossification

Front 71

Zone of resting cartilage

Back 71

Cells waiting to be called into action

Front 72

Zone of Proliferation

Back 72

Cells on active duty that are starting to divide.

Front 73

Zone of hypertrophy

Back 73

Chondrocytes in this zone make alkaline phosphatase which calcifies the cartilage matrix. The cartilage matrix is also reabsorbed, increasing the size of the lacunae.

Front 74

This Zone is where the most critical changes occur in the development of bones.

Back 74

Zone of Hypertrophy

Front 75

This is the zone where chondrocytes enlarge and begin to make alkaline phosphatase.

Back 75

Zone of Hypertrophy

Front 76

Zone of calcification

Back 76

Chondrocytes die and leave behind empty lacunae.
Bone is layed down in these zones by osteoblasts.

Front 77

Zone of ossification

Back 77

Osteoblasts lay down bone matrix over the spicules of calcified cartilage matrix

Front 78

What is the effect of growth hormone on the growth plate?

Back 78

Growth hormone has an anabolic effect on the cartilage of the growth plate. At puberty, increased amounts of sex hormones cause the growth plate to calcify. This is referred to as closure of the epiphyseal plate.

Front 79

What would result in excessive height/ short stature?

Back 79

Excess production of growth hormone before closure of the growth plate results in excessive growth in height. Growth hormone deficiency in children results in short stature.

Front 80

What bones are formed by Intramembranous Ossification?

Back 80

Frontal, Parietal and Occipital Bones.
Parts of the mandible and maxilla.

Front 81

What is responsible for producing the bony collar surrounding the cartilage model?

Back 81

Intramembranous ossification

Front 82

What are the five steps in Intramembranous Ossification?

Back 82

1) Mesenchyme condenses and mesenchymal cells differentiate into osteoblasts.
2) Osteoblasts produce osteoid, which becomes calcified. Spicules of bone are formed which grow and fuse together to form spongy bone.
3) Blood vessels invade the spaces of the spongy bone. The mesenchyme in the spaces gives rise to the bone marrow.
4)The mesenchyme that does not undergo ossification develops into the periosteum and the endosteum.
5) Over time, this primary bone is reabsorbed by osteoclasts and replaced with secondary bone.

Front 83

What is a BMU?

Back 83

Bone Multicellular Unit
Microscopic Unit on all bony surfaces where bone remodeling occurs throughout life. Couple resorption of osteoclasts with formation by osteoblasts in time and space.

Front 84

What kind of stimuli activate BMUs?

Back 84

Hormones
Trauma
Mechanical Usage

Front 85

What is the current theory on what signals the reabsorption of bone?

Back 85

It is thought that the signal to reabsorb bone is received and processed by osteoblasts, which then secrete a molecule that stimulates the osteoclasts.

Front 86

What happens in the process of fracture repair?

Back 86

1) Hemorrhage due to broken blood vessels in the fracture area and clot formation. Loss of blood supply leads to death of bone cells and destruction of bone matrix.
2) The periosteum and endosteum grow due to proliferation of osteogenic cells, forming a callus.
3) The osteogenic cells develop into bone cells that lay down primary bone, or cartilage cells that lay down hyaline cartilage.
4) The cartilage in the callus is replaced by primary bone in a manner similar to endochondral ossification.
5) The bony callus is eventually remodelled.

Front 87

In repairing a fracture, where do osteogenic cells develop into bone cells? Cartilage cells?

Back 87

Bone cells- deep in the callus where the blood supply is good.
Cartilage cells- near the surface of the callus where the blood supply is scarce.

Front 88

Osteomalacia
Characterized by?
Caused by?

Back 88

Characterized by deficient calcification of newly formed bone and decalcification of calcified bone. Caused by a calcium or vitamin D deficiency in adults.

Front 89

Osteoporosis

Back 89

Decrease in bone mass and quantity associated with a normal ratio of mineral to matrix. Due to decreased bone formation, increased bone resorption, or both.

Front 90

Why does osteoporosis occur in old age? immobile patients? post-menopausal women?

Back 90

Old age- diminished secretion of growth hormone
Immobile patients- lack of physical stress on bone
Post-menopausal women- diminished estrogen secretion

Front 91

Acromegaly

Back 91

excess pituitary growth hormone in adults characterized by very thick bones in the extremities and in parts of the facial skeleton.

Front 92

Osteosarcoma

Back 92

metastatic tumor of the bone

Front 93

Osteochondrodysplasia

Back 93

extreme bending of long bones