Lecture 5 - Bone and Cartilage Flashcards Preview

Histology (Emily) > Lecture 5 - Bone and Cartilage > Flashcards

Flashcards in Lecture 5 - Bone and Cartilage Deck (57):
1

What is cartilage made of?

Dense regular connective tissue, Types II Collagen

2

Chondrocytes

mature form of chondroblast; secrete collagen type II, have large golgi (washed out). Inside a space within the matrix called lacunae.

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What is it called when there are multiple cells in lacunae?

Isogenous groups

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Interstitial growth

from cell division of pre-existing chondrocytes; occurs only in early stages of cartilage formation = "cell nest.” Results in articular cartilages and epiphyseal plates of long bones.

5

Appositional growth

from chondrogenic cells in perichondrium. Results in formation of chondroblasts and or new chondrocytes. Results in new layer of cartilage matrix at periphery.

6

Where is hyaline found?

articular cartilage (joints), costal (ribs), fetal skeleton tissue, larynx, rings of trachea

7

What is hyaline composed of?

60-80% water
15% type II collagen for tensile & shear strength
10% proteoglycans for compressive strength
5% multiadhesive glycoproteins
and 5% chondrobalsts, chondrocytes, fibroblasts

8

What does hyaline have?

Perichondrium make up of dense irregular CT that makes membrane around hyaline and elastic cartilage. Perichondrium also has a cellular layer (chondrogenic layer) where chondroblasts reside.

9

What is the progression from fibroblast to isogenous groups?

Fibroblasts differentiate into chondroblasts

Chondroblasts mature into chondrocytes, which move towards the middle of the hyaline cartilage.

Form Isogenous groups/cell nest

10

Which is more flexible - hyaline or elastic cartilage?

Elastic

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What is Elastic cartilage made of?

Type II Collagen and Elastic Fibers

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Which has more isogenous groups - hyaline or elastic cartilage?

Elastic

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Where is elastic cartilage found?

external ear, epiglottis, elastic arteries

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Fibrocartilage - What is it made of?

Mix of dense irregular connective tissue and hyaline cartilage. Contains fibrocytes (making collagen I) and chondrocytes (making collagen II)

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Where is fibrocartilage found?

invertebral discs, annulus fibrosus, meniscus, tendons, ligaments

16

Is cartilage vascular or avascular?

avascular - limited capacity for repair.

17

What is bone made of?

Collagen I - Calcified connective tissue forms structural component of bones.

18

What are the two types of bone in a bone?

Compact bones in the middle, spongy bone at the ends.

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What are the functions of bones?

systems of levers, support, protection, bone marrow (in adults, mainly in flat bones), calcium & phosphate reservoir

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Epiphysis

end of bone (made of cancellous/spongy/trabecular bone). Can have bone marrow within spaces

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Diaphysis

shaft of bone (lamellar/compact bone) marrow cavity, bone marrow is mainly here. filled w/ hemopoetic tissue in kids, adipose tissue in adults (yellow marrow)

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Metaphysis

Small flanking region in bone between diaphysis and epiphysis.

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Epiphyseal line/plate

In youth, area of cartilage responsible for growth in bone lenth, inadults, cartilage is gone, but line remains.

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Periosteum

CT that covers outside of bone

Outer layer = fibrous, dense irregular CT + fibroblasts

Inner layer = cellular, osteogenic cells that become osteoblasts

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Sharpey's fibers

Type I collagen fibers that extend into bone tissue and are continuous with collagen fibers of ECM. Attach periosteum firmly to bone.

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Osteoprogenitor Cells

Found on bone surface, differentiate into osteoblasts. Derived from mesenchymal stem cells.

27

What is the transcription factor that triggers differentiation of osteoprogenitor cells?

Core binding factor alpha-1 (CBFA-1)

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Osteoblasts

Bone-producing cell found on the surface of bone. Synthesize collagen I and ground substances, trigger mineralization/calcification process.

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What do osteoblasts depend on?

Vitamin K and growth factors

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Osteocyte

Osteoblast once it becomes surrounded by matrix. Maintains bone matrix/mineral content.

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Bone-lining cell

Osteoprogenitor cells that are inactive, just cover bone surface.

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Osteoclast

Derived from hemopoietic stem cells (CFU-GM) and are responsible for the destruction and breakdown of bone. Large multinucleated cells with microvillus/ruffed border.

33

What transcription factors are needed for osteoclast formation?

C-fox, NFkB

34

What type of cytoplasm do osteoclasts have?

Acidophilic cytoplasm that releases hydrolytic enzymes.

35

Clear zone

Attachment site to bone (tight seal), prevents leaking

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Howship's lacuna

Depression of dissolving bone

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Endosteum

Inside bone

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Periosteum

Outside bone

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Osteon

Functional unit of bone, made of harversian canal and lamellae. Found in compact bone (few in spongy)

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Haversian Canal

Longitudinal channel that carries blood supply and nerves to the core of osteon.

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Volkmann's canal

connects adjacent Haversian canals

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Lamella

Layers of calcified fibrous tissue surrounding central canal (concentric circles); Arranged in perpendicular fashion to add length.

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Lacunae

Open spaces where cell resides

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Canaliculi

little channels that allow diffusion from haversian canal to osteocytes; for nutrient and communication.

Connects osteocytes to other cells and BVs.

Exchange of nutrients is a dertermining factor in the diameter of an osteon.

45

Bone Remodeling:

Balance of creation/destruction of bone; occurs all the time. Bone is very dynamic.

46

Sequence of bone remodeling.

(1) Osteoclasts remove Osteons - Leaving cutting cone.
(2) Osteoblasts lay down new matrix - Closing cone.
(3) Osteoclasts will phagocytize dead cells.

47

Bone Fracture Steps

(1) Formation of granulation tissue (loose CT). Damaged cells will release transmitters that will attract lots of inflammatory cells granulocytes. Proliferation of capillaries and fibroblasts.

(2) Formation of soft callus. (loose tissue is replaced by dense connective tissue (hyaline cartilage), then by fibrocartilage.

(3) Formation of bony callus: Cartilage is replaced by bone.

(4) Remodeling - Reformed by osteoblasts and osteoclasts.

48

What are the two ways to do bone formation?

1. Endochondrial Ossification
2. Intramembranous Endochondral Ossification

49

Endochondral Ossification

Perichondrium, where osteoprogenitors reside. As it expands and dies, the cartilage is calcified and replaced by osteoblasts and osteocytes. Vessels enter the bone.

Primary ossification center = Diaphysis

Secondary ossification center = help distinguish which bone is more mature.

Bone length grows due to chondrocytic division in epiphyseal plate.

50

Where does endochondral ossification occur?

All bones but flat bones.

51

Intramembranous Ossification

Flat bones

Mesenchymal cells differentiate directly to osteoblasts. First forms cancellous bone.

52

Interstitial Growth

Bone CANNOT grow interstitially by itself; the length increases by interstitial growth of hyaline cartilage within epiphyseal plate, so when the plate closes, no more growth!

53

Appositional Grown

Bone CAN increase it diameter by appositional growth = adding new bone to preexisting bony surface. Thickness both on the periosteum and endosteum. Can happy in people of all ages.

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Acromegaly

Growth of small bones by appositional growth continues too much - Overproduction of growth hormone after puberty.

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Gigantism

tumor occurs when epiphyseal plats are still open, lots of height growth - Overproduction of growth hormone during puberty.

56

Mutation knocks out sulfaction of carbohydrates; what structure does that affect the most?

Cartilege! It has a lot of sulfated fibers (this is the most dense regular CT! Very important!)

57

Myositis Ossificans occurs when in this type of cell differentiates into cartilage and bone producing cells (usually after trauma – what are they?

Satellite cells! Will differentiate into chondrocytes and osteoblasts