Exam 1 Flashcards - ACBS 400A

What is bone made up of?

both collagenous proteins (majority) & non-collagenous proteins

• non-collagenous proteins: proteoglycans (necessary for cell proliferation, mineral depositions, remodeling) & glycoproteins (necessary for mineral regulation)

minerals

water

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Define epiphysis.

end part of a long bone

initially growing separately from shaft

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Define diaphysis.

shaft or central part of long bone

contains mostly compact bone

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Define metaphysis.

region where epiphysis joins diaphysis

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Define epiphyseal/ growth plate.

hyaline cartilage plate in the metaphysis at each end of a long bone

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Define medullary space.

hollow part of bone that contains bone marrow

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Define trabecular/ cancellous/ spongy bone.

hierarchical, spongy, and porous material composed of hard & soft tissue components

found at epiphyses and metaphyses of long bone and in vertebral bodies

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Define compact/ cortical bone.

hard, dense outer later of all bones throughout body

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Define periosteum.

dense outer later of bone that contains vascular connective tissue enveloping bones expect at surfaces of joints

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Defie endosteum.

membrane lining inner surface of bony wall and bone marrow

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Define osteoblasts.

mononuclear cells that form new bone

come from mesenchymal cells in bone marrow

• primary ossification: formation of 1-cell thick layer covering surfaces undergoing remodeling

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Define osteoclasts.

large multi-nucleated cells at none surface and actively resorb bone

cytoplasm dense with non-membrane bound ribosomes and lysosomes

have ruffled edge on area in bone contact → very mobile

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Define osteocytes.

inactive and entrapped osteoblasts within bone matrix

maintains bone tissue

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Define osteoprogenitor.

germ cell aka stem cell that turns into other cells in bone

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Describe the structure of compact bones.

compact bone: where bony matrix is solid & filled with organic ground substance & inorganic salts

primary component of long bones to provide strong structural support

• ground substance: rich in mineralized calcium phosphate compound called hydroxyapatite

• osteon: cylindrical structures made up of layers of bone tissue called lamellae that surround a central canal

• Haversian/ central canals: any minute tube which forms a network in bone and contain blood vessels that run parallel to length of bone

• Volkmann/ perforating canals: channels that contain smaller blood vessels that run perpendicular to Haversian canals

  • connect Haversian canals to periosteum & medullary cavity

• Lacunae: small areas of holes in bone matrix where osteocytes reside

• Canaliculi: tunnels that form connections between neighboring osteocytes → where cytoplasmic projections go

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Describe the structure of trabecular bone.

trabecular bone: light, porous bone enclosing many large spaces in a honeycomb or spongy appearance (bone matrix)

most often found in long bones, ribs, skull, and vertebrae

often in epiphysis and metaphysis but can be in medullary space

forms matrix for bone marrow

• trabeculae: thin columns and plates of bone that create spongy structure along stress lines

  • provides flexibility and improves resistance to fracturing

• stores bone marrow, location of blood cell genesis, storage for minerals

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Describe the similarities and differences between periosteum and endosteum.

Similarities:

• both vascular connective tissue layers

• both contain osteoblasts and fibroblasts

Differences:

• periosteum: covers all bones except at articular surfaces of long bones (at cartilage)

  • has two layers (fibrous outer layer & inner connective tissue layer)

  • mature osteoblasts primary cells

  • nourishes compact bone & site of attachment for tendons and ligaments

• endosteum: present in all bones

  • singular loose connective tissue later

  • fibroblasts & hematopoietic cells primarily found here

  • used for growth, repair, and remodeling of bones

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Describe the differences between red bone marrow and yellow bone marrow.

Red bone marrow

• contains hematopoietic tissue that creates blood cells

• small % of marrow

• in young animals, located throughout most flat & long bones

  • will recede from long bones with maturity in trabecular spaces

• in adults, found in flat bones of vertebrae, sternum, ribs pelvis, along proximal (top) ends of humerus and femur

Yellow bone marrow

• contains mostly adipose tissue

• majority of marrow has potential to convert back to rend marrow under severe necessity

• located primarily in long bones

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What minerals and inorganic salts make up bone?

Minerals:

• calcium (Ca2+), phosphorus (phosphate ion), magnesium (Mg2+), sodium (Na+), potassium (K+), chloride (Cl-), fluoride (F-)

• most abundant: Ca2+ and phosphorus

Salts:

• citrate, hydroxyl, carbonate anions

General structure of bone mineral: hydroxyapatite crystals - (Ca10(PO4)6(OH)2)

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What type of collagens make up bones?

primarily composed of type I collagen

• synthesized mostly in osteoblasts

• osteoblasts make procollagen → hydroxylation with vit C (required) on proline and lysine groups → 3 collagen fibrils braid together to form tropocollagen → leaves osteoblasts

• tropocollagen: braided collagen fibrils that have improved strength and rigidity

  • 5 form microfibrils

• collagen matrix: microfibrils laid end to end in staggered formation in same direction in single bone metabolic unit

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Describe collagen breakdown.

• hydroxyproline: neutral heterocyclic protein amino acid that’s commonly found in bone & gelatin

  • digestion of bone collagen causes concentrations to rise in blood → used as diagnostic indication of bone destruction

• hydroxylysine: amino acid unique to collagen-like peptides

  • has covalent cross-link norleucine across adjacent collagen fibrils → stabilizes fibrils

    • creates banding pattern on collagen fibrils

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What is the function of osteocalcin?

protein found in bone

1. osteocalcin: protein found in extracellular matrix of bone and in serum of circulating blood

• produced solely by osteoblasts - vitamin K often present

• inhibits haphazard formation of hydroxyapatite precipitates and mineralization

• hemoattractant of leukocytes → also attracts osteoclasts to areas in need of resorption and remodeling

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What are the types of bone formation?

1. intramembranous ossification: bone formation within primitive connective tissue

2. endochondral ossification: pre-existing cartilage is turned into bone

3. ectopic bone formation: pathologic process in which connective tissues that aren’t usually turned into bone are ossified

L2 - bone formation & remodeling

Define mesenchyme.

intramembranous ossification

tissues characterized by primordial cell types surrounded by large amount of extracellular matrix (loose connective tissue)

condenses & becomes vascularized ding embryonic development

L2 - bone formation & remodeling

Define woven bone.

intramembranous ossification

early bone where collagen fibrils remain randomly interwoven

disorganized arrangement of collagen fibers

weaker and more flexible

rapidly formed

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Define osteoid.

unmineralized, organic portion of bone matrix that forms prior to the maturation of bone tissue

can be found in woven and lamellar bone

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Describe the process of intramembranous ossification.

begins in embryo development

1. formation of ossification spicules: mesenchymal cells form collagen fibrils → form matrix → conversion to osteoblasts

2. formation of extracellular matrix and trabeculae: osteoblasts combine fibrils with Ca2+ → calcification leads to formation of trabeculae

3. osteoid vascularization development: fibrils go from random to organized assortment → formation of lamellar layers around blood vessels

4. osteons and compact bone formation: outer layer connective tissue condenses into peroiranium → osteoblasts turn into fibroblasts

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Define hyaline cartilage.

translucent bluish white type of cartilage present in joints, respiratory tract, and immature skeleton

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Describe the process of endochondral ossification.

includes: bones in extremities, base of skull, vertebral column, pelvis

• starts as hyaline cartilage

• mesenchyme differentiates into chondrocytes → lay out in shape of being being formed

• chondrocytes secrete hyaline matrix of type II collagen

• osteoprogenitor cells in perichondrium lining in cartilage model is activated

• deposit thin collar of woven bone on outside of model

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What are centers of ossification?

within hyaline cartilage & are distinguished by enlargement of chondrocytes in particular areas of cartilaginous bone

• lacunae expand with thin strands of cartilage matrix separating adjacent ones → remaining matrix accumulates Ca2+ phosphate

• calcification causes hypertrophied chondrocytes do apoptosis

  • blood vessels form from new periosteum and invade these areas → new osteoprogenitor & other cells follow vessels → form osteoblasts that congregate on calcified cartilage spicules → deposit bone matrix

in horses & cows

• starts in diaphysis of long bones by 3rd month of fetal development

• secondary centers in epiphyses of long bones later

• expansion of epiphyseal ossification won’t replace area’s cartilage (articular surfaces)

• transverse disk of epiphyseal cartilage remains between sections (epiphyseal plate)

  • chondrocytes in area arranged into columns that allows growth in length of bone

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Define zone of proliferation.

formed by chondrocytes that are further from diaphysis

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Define zone of maturation.

formed by chondrocytes that have stopped dividing and have become enlarged

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Define zones of hypertrophy.

formed by hypertrophy and vacuolation of chondrocytes

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Define zone of provisional calcification.

formed by cartilaginous matrix surrounding cells beginning to calcify

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How do bones grow in length.

• diaphysial side chondrocytes go through apoptosis and degenerate → lacunae invaded by blood vessels and osteoprogenitor cells from marrow spaces

  • osteoblasts differentiate and form bars of calcified cartilage → thin layer of collagen matrix deposited on surface of calcified cartilage → good conditions leads to new bone matrix calcifying

  • osteoclasts resorb woven bone and calcified in metaphysis → osteoblasts move in to lay down type I collagen for lamellar bone

• zone of proliferation cells advance growth plate away from diaphysis

• process controlled by somatotropin hormone from pituitary

  • causes local production of insulin-like growth factor 1 (somatomedin) → encourages zone of proliferation chondrocytes to divide

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Describe growth plate closure.

once at mature length, cartilage creation slowly stops

• replacement of cartilage with bone at diaphysial side continues until entire growth plate cartilage is replaced by bone

• metaphysis does not technically exist until plate is closed

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How do bones grow in diameter?

• deposition of bone on outside surface between old bone and periosteum

• new bone laid down while old bone inside resorbed at same time of lengthening

• hyaline model shape never changes = rate of resorption & creation are equal

• stress can dictate mineral deposition & bone matrix thickness

• spongy bone stops earlier in thickening → space fills with bone marrow

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Define bone remodeling units (BRU).

small units of bone that undergo remodeling at any given time

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What are the four steps of bone remodeling.

1. activation

2. resorption

3. reversal

4. formation

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Describe the first step of bone remodeling.

activation: converts/inactive bone surface into that to be remodeled

• selective remodeling directed by a signal from bone

  • microfracture disrupt ordered collagen fibril orientation → disrupts normal electrical change through mineral crystals → initiates remodeling

  • bone deterioration elicits autocrine/paracrine factor secretion to initiate process

• quiet osteoblasts shrink in areas of bone needing remodeling → exposes bone matrix → osteoclasts move in → bind to bone on ruffled border

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Describe the second step of bone remodeling.

resorption

• osteoclasts release acids & proteolytic enzymes from ruffled border → dissolves bone matrix

• minerals & bone matrix broken down products absorbed via diffusion or other transport processes into osteoclasts

  • sent back out into ECF

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Describe the third step of bone remodeling.

reversal

• howship’s lacuna: hole created by osteoclasts during resorption

• needs insulin-like growth factor 2 and transforming growth factor (TGF) - beta

  • released during collagen matrix breakdown

  • activate cells lining surface to revert to osteoblasts

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Describe the fourth step of bone remodeling.

formation

• begins with deposition of osteoid by osteoblasts: consists mostly of type I collagen, proteoglycans, and smaller proteins found in mature bone

• lays osteoid down in lamellae with fibrils parallel to each other

  • compact bones goes from outer edges to center when filled until reach Haversian canal

  • different lamellae fibrils oriented at angles from each other

• trabecular bone deposited in curved sheets following hollow shape

• mineralization occurs after time delay but happens quick when activated

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What is a complete fracture? What are the different types of complete fractures?

complete: through entire bone

• transverse: straight line through bone

• oblique: line at an angle through bone

• spiral: corkscrew line through bone

• comminuted: more than 2 parts to fracture

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What is a incomplete fracture? What are the different types of incomplete fractures?

incomplete: not entirely through bone

• bowing: bone is bent

• buckle: fracture on concave side

• greenstick: fracture on convex side

• avulsion: bone fragment separates from the rest of the bone, often attached to ligament or tendon

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What is a displacement fracture?

ends of fracture not within same area, created a gap

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What are the different types of Salter-Harris fractures?

Type 1: through growth plate

Type 2: through growth plate & metaphysis

Type 3: through growth plate & epiphysis

Type 4: through all three elements

Type 5: crush injury of growth plate

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How do bones help maintain homeostasis?

remodeling moves mineral into ECF

bone helps as blood pH buffer

• releases cations in response to acidosis or anions in response to alkalosis

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What is osteocytic osteolysis?

osteocytic osteolysis: process of Ca2+ resorption from bone

parathyroid hormone (PTH) stimulates osteocytes to pump some fluid Ca2+ into ECF

• prevents osteoclasts from entering reversal phase & osteoblasts from laying new matrix

• if deficit severe, osteoclastic osteolysis initiated

  • persistent secretion of PTH → activates osteoclasts by shrinking osteoblasts to expose bone matrix

  • osteoblasts release paracrine factors: prostaglandin E2, IL-1, and IL-6 that stimulate osteoclasts

1,250dihydroxyvitamin D (vit D hormone) indirectly affects bone Ca2+ concentration

• increase efficiency of Ca2+ and phosphorus absorption absorption in intestine → blood concentration balanced → permits mineralization of bone matrix

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What is the function of calcitonin?

major Ca2+ regulating hormone

• secreted by C-cells in thyroid when Ca2+ blood levels too high

• acts on osteoclasts to inhibit bone resorption

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Fill in the blanks.

Mesenchymal cells differentiate into different cells depending on the method of ossification. In intramembranous ossification, they mostly become ______ while in endochondral ossification, it most commonly turns into _______.

intramembranous: osteoblasts

endochondral: chondrocytes

Assignment 1

Which of these is a hormone NOT directly related to osteocytic osteolysis?

A. calcitonin

B. 1,25-dihydroxyvitamin D

C. parathyroid hormone

D. osteocalcin

osteocalcin

Assignment 1

What amino acids are only found in bone?

hydroxylysine

hydroxyproline

Assignment 1

What is osteocalcin?

a protein that promotes mineralization of bone in proper orientation

Assignment 1

Describe the steps of bone remodeling.

1. activation: quiet osteoblasts shrink in areas of bone needing remodeling → exposes bone matrix → osteoclasts move in → bind to bone on ruffled border

2. resorption: osteoclasts release acids & proteolytic enzymes from ruffled border → dissolves bone matrix that then leaves depression in the bone → minerals & old matrix by-products absorbed via diffusion or other transport processes into osteoclasts → released into ECF

3. reversal: uses insulin-like growth factor 2 and transforming growth factor (TGF)- beta to activate lining surface cells to revert to osteoblasts

4. formation: deposition of osteoid by osteoblasts → form lamellae from outer edges to center → forms Haversian canal → calcified to strengthen & finish process of remodeling

Assignment 1

Fill in the blank.

The _________ is the model for bone formation during endochondral ossification.

hyaline cartilage

Assignment 1

What is the role of parathyroid hormone (PTH) in Ca2+ homeostasis?

prevents osteoclasts from entering reversal phase & osteoblasts from laying new matrix depending on if there is a Ca2+ deficit in the ECF

Assignment 1

In what type of bone can you find yellow marrow?

long bones

Assignment 1

On what side does the growth plate begin to close?

diaphyseal

Assignment 1

What is needed for the hydroxylation of procollagen to occur? Without this, procollagen cannot be stable as tropocollagen, and can’t form the bone matrix.

vitamin C

Assignment 1

Explain the process of bone repair after a fracture.

1. first the bone is broken due to some kind of trauma

2. this causes the blood supply to break & osteoprogenitor cells to tear

3. blood then pools into the area of the break, forming a hematoma, and osteocytes die

4. once area fills with blood, proinflammatory cytokines attract phagocytes into area to remove dead tissue & clot material

5. the space left now has cartilage beginning to fill in the hypoxic area to form a callus

6. fibrous tissue is created into the callus to strengthen it

7. woven bone begins to fill in the space to create a hard callus

8. finally, bone remodeling occurs & bone is repaired

Assignment 1

Generally, what is the majority of hydroxyapatite crystals (bone crystals) made of?

calcium & phosphate

Assignment 1

T/F: When bone is increasing in diameter, outside bone is created while inside bone is resorbed. This keeps the rate constant and allows room for bone marrow.

True

Assignment 1

T/F: The primary location of endochondral ossification is in the epiphysis of long bones. The secondary location later in the process is the diaphysis of the long bones.

False

Assignment 1

Fill in the blanks.

There are 2 connective tissue layers of bone. There is the ______ that is on the external aspect of the compact bone, and it nourishes it. Then there is the _______ that is on the internal aspect of the compact bone where the medullary cavity is found.

periosteum

endosteum

Assignment 1

Define zone of proliferation.

formed by chondrocytes that are further from diaphysis

Assignment 1

Define zone of maturation.

formed by chondrocytes that have stopped dividing & have become enlarged

Assignment 1

Define zone of provisional calcification.

formed by cartilaginous matrix surrounding cells beginning to calcify

Assignment 1

Define zone of hypertrophy,

formed by enlargement and vacuolation of chondrocytes

Assignment 1

Label this diagram.

Terms: Haversian canal, osteon, concentric lamellae, interstitial lamellae, volkmann canal, circumferential lamellae, periosteum

Assignment 1

Label this diagram.

Terms: metaphysis, periosteum, epiphyseal plate, spongy/trabecular bone, medullary cavity/space, compact/cortical bone, epiphysis, yellow marrow, diaphysis, endosteum, red bone marrow

Assignment 1

Label this diagram.

Terms: lamellae, lacuna, canaliculi, osteoblast, haversian canal, osteoblast, osteocyte

Assignment 1

What is the role of Vitamin D hormone of Ca2+ homeostasis?

increases efficiency of Ca2+ and phosphorus absorption in intestine

Quiz 1

What is the difference between red and yellow bone marrow?

red bone marrow is found in long bones and most flat bone, and it is the location of hematopoietic cell production

yellow bone marrow is found primarily in long bones, and it is a storage place for adipose tissue

Quiz 1

What are centers of ossification?

the locations in the hyaline cartilage model that ossify first

Quiz 1

Explain the process of collagen matrix formation.

1. first, osteoblasts synthesize procollagen

2. then, there is hydroxylation of proline and lysine groups with the help of vitamin C

3. this process helps stabilize procollagen for the development of helices

4. 3 procollagen are combined to form the tropocollagen

5. 5 of these combine to create a microfibril

6. finally, staggered microfibrils end to end then make up the collage matrix

Quiz 1

What is the purpose of the epiphyseal plate?

allow long bones room to grow in length as an animal matures

Quiz 1

State the function of osteoprogenitor cells, osteoclasts, osteoblasts, and osteocytes. Identify them in the picture.

A is osteoclasts

• large multi nucleated cells at bone surface and actively resorb bone

B is osteoblasts

• mononuclear cells that for new bone (ossification) and originate from mesenchymal cells in bone marrow

C is osteocytes

• inactive & entrapped osteoblasts within bone matrix

Osteoprogenitor cells

• germ cell that turns into other cells in bone

Quiz 1

What causes hyena disease?

vitamin A toxicosis in calves

Quiz 1

What is the difference between epiphyseal and diaphyseal ossification?

epiphyseal ossification won’t replace articular cartilage

diaphyseal ossification replaces all cartilage

Quiz 1

What is the difference between Haversian canals and Volkmann canals?

Haversian canals run parallel with the bone and are at the center of osteons

Volkmann canals run perpendicular to bone and feed the periosteum and medullary cavity

Quiz 1

Osteocalcin is produced by osteoblasts in the presence of vitamin K. What does it do?

Inhibits formation of hydroxyapatite precipitates and mineralization

Attracts osteoclasts to areas in need of resorption and remodeling

Quiz 1

Explain the process of growth plate closure.

1. first, diaphyseal side chondrocytes experience apoptosis

2. Then, blood vessels and osteoprogenitor cells invade into lacunae of marrow spaces in primary ossification zone

3. After invasion, osteoblasts then differentiate along calcified cartilage

4. They deposit collagen matrix on calcified cartilage

5. In favorable conditions, this matrix quickly calcifies and forms spongy bone in the metaphysis

6. As plate finishes its closure, osteoclasts move into metaphysis to resorb woven bone

7. At the same time of woven bone resorption, osteoblasts put down new bone matrix

8. By the end, the metaphysis has extended farther from diaphysis and growth plate has closed

Quiz 1

In what location does intramembranous ossification happen most often in fetal development?

skull

Quiz 1

Describe the anatomy of cartilage.

Cells

• chondrocytes are cells responsible for cartilage formation

• chondrocytes secrete a amorphous gel-like matrix: contains collagens, proteoglycans, and non-collagenous proteins

  • contains polysaccharides (chondroitin sulfates) complex

• young chondrocytes can divide after they come isolated in lacunae → daughter cells secrete new matrix between them & move apart in separate lacunae

Layers

• Perichondrium: dense fibrous layer lined by cells that have the capacity to secrete hyaline matrix

  • outer fibrous layer: provides protection, mechanical support, and attaches cartilage to other structures

  • inner cellular: involved in growth & maintenance of cartilage

• lacks nerves & blood vessels

• overall resistant to compression

L3

What are the different types of cartilages?

1. hyaline: bulk of cartilage found in animals

   1. found on ventral ends of ribs, in tracheal rings & larynx, articulating surfaces of bones, and in growth plates in growing animals

   2. randomly oriented but little elastin

2. elastic: relatively scare but found in external ear & epiglottis

   1. has a ton of elastic fibers embedded in it

   2. more flexible due to elastin fibers in ground substance in matrix

3. fibrocartilage: found at site of insertion of many larger ligaments onto bone, intervertebral disks, and symphysis of pubis

   1. proportion of dense collagen bundles oriented parallel

   2. cells occupy lacunae arranged in rows between coarse bundles of collagen

   3. collagen content of matrix greatly increased & collagen fibrils from thick though bundles aligned in 1 direction to improve tensile strength

L3

Describe the growth of cartilage.

• chondrocytes come from mesenchymal cells

  • undergo mitosis and spread out

  • continue to surround themselves with specialized mix of proteins to form interstitial matrix

• fine fibrils of collagen exist within matrix

  • originally secreted into matrix as tropocollagen by cells → aggregate & assemble themselves into collagen fibrils

L3

What is the difference between interstitial and appositional growth?

• interstitial: process of growth that occurs through the addition of new cells within existing tissue

  • involves mitosis

  • increases tissue size since add new cells

  • occurs throughout life

• appositional: process of growth that involves the addition of new cells to surface of the tissue

  • involves differentiation of stem cells

  • increases tissue size by increase in new layers

  • occurs during growth

L3

What are the types of collagen in cartilage?

1. type II: main collagen form in cartilage

   1. only found in cartilage

2. type IX: on surface of type II & doesn’t form fibrils

   1. functions to regulate spatial arrangement of type II

3. type X: found in chondrocytes within growth plates in long bones

L3

Define joints.

aka articulation

junction between any 2 bones

attaches bone to another → allows bones to move freely with little resistance

movement controlled & limited by action of muscles & by ligaments and tendons

types of joints: immovable & synovial

L3

Describe synovial joints.

contained in a capsule

• outer fibrous layer of collagen fibers that run from periosteum of 1 to bone another

  • lends side to side stability to joint

• ligaments are special extension of fibrous capsule

  • location on inside or outside of joint capsule

L3

Describe synovial fluid.

• inner surface of capsule composed of synovial membranes

  • involved in production of synovial fluid (viscous liquid with consistency similar to egg white)

• provides lubrication to joint

  • reduces wear on opposing surfaces

L3

Define ligaments.

tough, elastic bands of connective tissue that surround joint to give support & limit movement

connects bone together

L3

Define tendons.

another type of tough connective tissue thats on each side of a joint & attaches on each side of a joint

attaches to muscles that control movement of joint

connect muscles to bones

L3

Define bursas.

fluid-filled sacs between bones, ligaments, or other nearby structures

help cushion the friction in a joint

L3

Define menisci.

special areas of dense fibrocartilage that exist between articulating cartilage surfaces on some bones

most common in areas bearing weight

cushions compressive forces

L3

Name the different types of joints.

1. pivot

2. hinge

3. ball & socket

4. condyloid

5. plane

L3

Describe pivot joints.

• freely moveable joints that allows only rotary movement around a single axis

• moves in a rotation pattern within ring formed by 2nd bone & ligament

• allows for turning of head

• radius & ulna at elbow and carpus

L3

Describe hinge joints.

• primarily only allows movement in 1 plane, but can in small movements in other directions

  • up/down or side to side but can’t do both well

• toes, elbows, stifles, tarsi

L3

Describe ball and socket joints.

• joint where rounded surface of a bone moves within a depression on another bone

• allows greater freedom of movement

• shoulders and hips

L3