COHN EXAM 3

lectures 6-10

What is the true microscopic nature of these rings?

Contain tiny tunnels/canals despite solid appearance

What are the concentric rings of an osteon called?

Lamellae

What is the singular vs plural of lamella?

Lamella (singular), lamellae (plural)

How are lamellae arranged?

Nested concentric rings within each other

What central feature is present in each osteon?

A hole (central canal)

What are the two synonymous names for the central canal?

Central canal and Haversian canal

What structures are found within the Haversian canal?

Small artery and vein

What additional structure is often present in the Haversian canal?

Nerve

What size/type are the vessels in the Haversian canal?

Very small artery (near capillary) and vein

What results from packing osteons together?

Gaps between cylinders

What lamellae fill gaps between osteons?

Interstitial lamellae

What does “interstitial” mean in this context?

In-between

Where are interstitial lamellae located?

Between adjacent osteons

What lamellae cover the outer surface of bone?

Circumferential lamellae

Where are circumferential lamellae located?

Around entire outer circumference of diaphysis

What are the three types of lamellae?

Concentric, interstitial, circumferential

What is the outermost tissue covering bone?

Periosteum

What type of tissue is periosteum?

Connective tissue

What is one function of periosteum?

Attachment site for ligaments

Do ligaments attach directly to bone tissue?

No, they attach to periosteum

What connects periosteum firmly to bone?

Sharpey’s fibers

What are Sharpey’s fibers?

Deep penetrating connective tissue fibers

What analogy describes Sharpey’s fibers?

Strong Velcro-like attachment

Why must periosteum attachment be strong?

To support forceful ligament/tendon forces

What also attaches to periosteum besides ligaments?

Tendons

Why must tendon attachment be strong?

To withstand muscle force

What is another major function of periosteum?

Blood supply to bone

How do vessels initially interact with bone?

Run along periosteum

What happens after vessels travel along periosteum?

They perforate into bone

What is a perforating canal?

Canal allowing vessels into bone

What is another name for perforating canal?

Volkmann’s canal

What do Volkmann’s canals connect?

Adjacent Haversian canals

What overall pattern do canals form in bone?

Grid-like network

What runs longitudinally in bone?

Haversian canals

What runs transversely in bone?

Volkmann’s canals

Why is this vascular system important?

Enables blood flow throughout bone

Where else does a similar vascular network exist?

Epiphysis

What is a third function of periosteum?

Produces osteoblasts

What does “blast” indicate?

Building

What are osteoblasts?

Bone-building cells

Where are osteoblasts produced?

Inner surface of periosteum

Where do osteoblasts act?

Outer surface of circumferential lamellae

How does bone grow in length vs thickness?

Length stops ~early 20s; thickness can continue

What stimulates bone thickness growth?

Physical exercise

What happens to bone without use?

Atrophy

What is atrophy?

Shrinkage of tissue

What phrase describes bone physiology?

Use it or lose it

What are osteocytes?

Mature bone cells

How do osteocytes differ from osteoblasts?

Maintain bone, do not build new bone

What percentage of bone cells are osteocytes?

~99%

Where are osteocytes located?

Between lamellae

What space do osteocytes occupy?

Lacuna

What is plural of lacuna?

Lacunae

What are canaliculi?

Tiny canals connecting lacunae

What is the function of canaliculi?

Transport nutrients and oxygen

Why are canaliculi necessary?

Osteocytes are far from blood supply

How do osteocytes receive nutrients?

Through interconnected canaliculi network

What does this network connect?

Lacunae across osteons

Why is this system essential?

Allows cell survival in dense bone matrix

What is compact (cortical) bone?

Dense, solid outer bone tissue

Where is compact bone found?

Outer layer of all bones

Where is compact bone especially thick in long bones?

Diaphysis

What is the function of compact bone?

Strength, protection, resistance to bending/torsion

What are the two layers of periosteum?

Outer fibrous layer and inner cellular layer

What type of tissue is the outer periosteum layer?

Dense connective tissue

What is the inner periosteum layer also called?

Osteogenic layer

What is another function of periosteum?

Conduit for blood vessels and nerves

What type of growth does periosteum enable?

Appositional (thickness) growth

How are osteons oriented?

Parallel to long axis of bone

What is the function of concentric lamellae?

Resist twisting forces

What direction do Haversian canals run?

Longitudinal

Where are circumferential lamellae located?

Just deep to periosteum

What is the function of circumferential lamellae?

Contribute to bone thickness

What is the origin of interstitial lamellae?

Remnants of old osteons

Where are blood vessels located in periosteum?

Running along its surface

What do periosteal vessels do?

Supply bone and give rise to penetrating vessels

What vessels are in perforating canals?

Arteries and veins

What is the function of vessels in perforating canals?

Link periosteum to internal bone circulation

What vessels are in Haversian canals?

Longitudinal arteries and veins

What is the vascular pattern of bone?

Grid-like (longitudinal + perpendicular)

What is a lacuna?

Small cavity housing an osteocyte

How are osteocytes connected?

Through canaliculi

How are osteons arranged in compact bone?

Packed cylindrical units

How is blood distributed through bone?

Via Haversian and Volkmann's canals

What is the relationship between osteons and interstitial lamellae?

Interstitial lamellae fill spaces bet

What covers the outermost surface of all living bone?

Periosteum

Is the outermost tissue of bone actual bone tissue?

No, it is periosteum

What lies immediately deep to periosteum?

Compact (cortical) bone

What is the general location of spongy bone?

Always internal, never on surface

What are synonyms for spongy bone?

Spongy bone, trabecular bone, cancellous bone

What does spongy bone resemble structurally?

A sponge with threads and spaces

What happens when you drill through compact bone?

You reach spongy bone

Where is spongy bone found in flat bones?

Between two layers of compact bone

What analogy describes flat bone structure?

Sandwich (compact = bread, spongy = filling)

Can spongy bone be seen grossly?

Yes

Are spaces in living spongy bone empty?

No

What fills spaces in living spongy bone?

Red bone marrow

What is another name for red bone marrow?

Hematopoietic tissue

What happens to spaces in dead bone specimens?

Become air spaces

What are the small structural units of spongy bone?

Trabeculae