histology

Question 1

territorial vs inter-territorial matrix:

Answer 1

territorial - immediately surrounding isogenous groups

inter-territorial - between isogenous groups

Question 2

do chondrocytes have lacunae?

Answer 2

yes, but they are artifact

2 chondrocytes can occupy 1 lacunae

Question 3

cartilage characteristics:

Answer 3

avascular
connective tissue
low proliferation
chondrocytes found in lacunae
may/may not have a perichondrium
different functions/different types

Question 4

what are the 3 types of cartilage?

Answer 4

hyaline
elastic
fibrocartilage

Question 5

where is elastic cartilage found?

Answer 5

ears, nose, aorta, epliglottis

Question 6

where is fibrous cartilage found?

Answer 6

intervertebral discs, pubic symphysis, menisci

Question 7

where is hyaline cartilage found?

Answer 7

costal cartilage, articular joint cartilage

Question 8

which cartilages have a perichondrium?

Answer 8

elastic and hyaline (but not in joints)

Question 9

what is the lacunar rim?

Answer 9

inner layer of the territorial matrix
consists of loose collagen fibrils

Question 10

what is the territorial matrix composed of?

Answer 10

randomly arranged type II collagen fibrils surrounded by proteoglycans

Question 11

appositional vs interstitial growth

Answer 11

appositional
-growth from surface perichondrium cells
-mesenchymal cells/fibroblasts –> chondroblasts –> chondrocytes
-chondroblasts secrete matrix and become surrounded, becoming chondrocytes

interstitial
-growth from within the cartilage matrix
-chondrocytes divide - isogenous groups formed
-territorial and inter-territorial matrix

Question 12

what type of collagen in ECM of elastic and hyaline cartilage?

Answer 12

type II

Question 13

what type of collagen in ECM of fibrocartilage?

Answer 13

type I

Question 14

which cartilages have a perichondrium?

Answer 14

elastic and hyaline (unless its a joint)

Question 15

core protein of all cartilage proteoglycans?

Answer 15

aggregan

Question 16

what are the 2 glycosaminoglycans of cartilage proteoglycans?

Answer 16

keratan sulfate
chondroitin sulfate

Question 17

what molecule are the core proteins attached to?

Answer 17

hyaluronic acid

Question 18

describe bone composition:

Answer 18

organic (35%) - collagen
inorganic (65%) - hydroxyapatite (calcium and phosphorus)

Question 19

what part of bone lends more flexibility?

Answer 19

organic collagen

(mineralized/hydroxyapatite bone provides rigidity, i.e in ear ossicles)

Question 20

2 parts of bone:

Answer 20

cortical bone
-compact
-lamellar
-provides strength and rigidity, supports weight

cancellous
-trabecular
-spongy
-ion homeostasis

Question 21

what is the periosteum?

Answer 21

fibrous outer surface of bone
does not cover joint surfaces or tendon/ligament insertions
vascularized - inner layer contains osteoprogenitor cells

Question 22

where does the spongy bone end and bone marrow begin?

Answer 22

at edge of metaphysis and diaphysis (shaft)

Question 23

where is the growth plate located?

Answer 23

in between the metaphysis and epiphysis

contains hyaline cartilage

Question 24

what is the bone sandwich?

Answer 24

periosteum –> bone –> endosteum

Question 25

what are the 2 layers of the periosteum?

Answer 25

outer fibrous -sharpey's fibers extend into cortical bone -outside connects to tendons/ligaments inner cellular (cambrium) -deep to fibrous -contains osteoprogenitor cells -can differentiate into osteoblasts to produce new bone

Question 26

what are lacunae?

Answer 26

"lakes" that the osteocytes sit in

Question 27

what are canniculi?

Answer 27

projections that connect lacunae so that osteocytes can interact with each other

Question 28

describe the anatomy of the trabeculae?

Answer 28

endosteum covering (old osteoblasts) functional osteoblasts line outside osteoid underneath osteoblasts (new unmineralized bone that needs to be mineralized/matured) osteocytes in lacunae with canniculi

Question 29

where are the 2 places that osteoprogenitor cells are found?

Answer 29

inner layer of peristeum (periosteal cells) endosteum of trabeculae (endosteal cells)

Question 30

osteoblasts on a histology slide:

Answer 30

-polar cell with single nucleus -nucleus points away from working surface cuboidal in shape -basophilic stain with eosinophilic mineralized bone beneath it -prominent golgi and ER form a border around the trabeculae

Question 31

describe an osteocyte:

Answer 31

-osteoblast that gets trapped in osteoid -does not divide (no isogenic groups) -in lacunae w/ canniculi -connected via gap junctions -can't differentiate back -function as a network of sensory cells, control bone formation/resorption/homeostasis die and form microcracks --> leads to remodeling

Question 32

appearance of inactive osteoblasts:

Answer 32

thin, elongated cells inactive osteoblasts on bone surface that is not currently remodeling

Question 33

osteoclast origin:

Answer 33

hematopoetic formed from aggregated monocytes therefore, multi-nucleate

Question 34

osteoclast categorization:

Answer 34

polar cell multiple nuclei point away from working surface large compared to osteoblast vesicles (H+/hydrolytic enzymes) white space underneath on histo --> "eaten bone"

Question 35

osteoclasts vs megakaryocytes

Answer 35

osteoclasts have distinct, numerous nuclei whereas megakaryocytes have one nucleus with numerous nodules

Question 36

2 types of bone ossification:

Answer 36

echondral and intermembranous

Question 37

what bones undergo intramembranous ossification?

Answer 37

flat bones (i.e. skull, sternum) within a vascularized embryonic mesenchyme NOT the appendicular skeleton

Question 38

intramembranous ossification steps:

Answer 38

1. mesenchymal cells aggregate without a cartilage intermediate (Wnt, Shh, growth factors) 2. mesenchymal cells differentiate into osteoblasts (bone blastema) 3. osteoblasts deposit osteoid. calcium from the blood vessel is used in the mineralization process --> primary bone tissue formed

Question 38

intramembranous ossification steps:

Answer 38

1. mesenchymal cells aggregate without a cartilage intermediate (Wnt, Shh, growth factors) 2. mesenchymal cells differentiate into osteoblasts (bone blastema) 3. osteoblasts deposit osteoid. calcium from the blood vessel is used in the mineralization process --> primary bone tissue formed

Question 39

echondral ossification steps:

Answer 39

....

Question 40

what collagen do hypertrophic chondrocytes secrete?

Answer 40

collagen type X

Question 41

what collagen do proliferating chondrocytes secrete?

Answer 41

colagen type II

Question 42

what induces vascular invasion and osteoprogenitor recruitment?

Answer 42

VEGF

Question 43

what induces PTH expression and bone collar formation?

Answer 43

Ihh