May22 M2-Histo 1 Flashcards
cartilage def
specialized CT where ECM is firm
cartilate type in trachea
hyaline cartilage
hyaline cartilage charact + surrounded by what
- homogenous ECM, looks transparent
- don’t see collagen fibers
- surrounded by perichondrium (border) on both sides
cells in hyaline cartilage
- chondrocytes. found in clusters, forming groups called isogenous groups.
- isogenous groups are in spaces called lacunae
function of cartilage
provide support to adjacent tissues (in trachea, keeps trachea open, easier air circulation)
cartilage important charact
no blood vessels
3 types of cartilage and how make diff types
- hyaline
- elastic
- fibrocartilage
- made by variations in the constituents: CT fibers of the ECM and proteoglycans*
main components of ECM in cartilage
- fibers (type 2 collagen in elastic and hyaline + some other types of collagen)
- amorphous ground substance (proteoglycans and glycoproteins)
main fiber in hyaline and elastic cartilage ECM
type 2 collagen
main proteoglycan in cartilage ECM
chondroitin sulfate (SO4)
main glycoprotein in cartilage ECM
chondronectin
type 1 collagen is found where in the body
- loose and dense CT
- fibrocartilage
- bone
component specific to elastic cartilage
elastic fibers
structure of proteoglycans and what proteoglycans are bound to
- protein core (long linear protein) with lateral chondroitin sulfate side chains
- the core protein binds to a link protein, which binds to hyaluronic acid (perpendicular to protein core)
- so chondroitin sulfate is the name of a proteoglycan which has chondroitin sulfate side chains on a protein core*
chondroitin sulfate vs chondronectin composition in sugars and proteins
chondronectin = 90% proteins 10% sugars
chondroitin sulfate = 50% protein 50% sugars
most important proteoglycan in hyaline cartilage ECM and why
chondroitin sulfate. bound to water so large amount of water acting as cushions in the joint
how to diff between hyaline and elastic cartilage
Verhoeff Hematoxylin stain. stain elastic fibers
only way to differentiate
what elastic fibers allow in elastic cartilage
- subject to change and stretchy
- give elasticity to cartilage
disposition of elastic fibers in elastic cartilage
- form network around lacunae
- bit at the level of the perichondrium also
typical cell type of cartilage mature and immature form
- chondroblast (immature)
- chondrocyte (mature)
function of chondrocytes (in isogenous groups contained in lacunae)
secrete the ECM of the cartilage (type 2 collagen, hyaluronic acid, proteoglycans, glycoproteins, +/- elastic fibers
2 layers of perichondrium and charact
- fibrous perichondrium (outer) = collagen fibers in same directions + inactive fibrocytes, elongated cells
- chondrogenic perichondrium = clear cytoplasm, central nucleus, active site of chondroblast division and chondrocytes formation
chondroblast location in cartilage (hyaline for ex) and what they do
in chondrogenic perichondrium, make the chondrocytes
2 types of cell growth in cartilage (hyaline cartilage) and description
- appositional growth at the chondrogenic perichondrium (chondroblasts making chondrocytes pushing them in matrix)
- interstitial growth inside lacunae (division of chondrocytes)
most important type of growth in cartilage (hyaline and elastic) and why
appositional. if there’s a tear, it will repair cartilage. articular surfaces don’t have perichondrium so no repair
* interstitial growth doesn’t play a role in repair*
where cartilage persists in bone + type of cartilage
at articular surface
HYALINE cartilage on articular surfaces
cartilage at articular surface characteristics
- smooth surface facing synovial cavity bc NO PERICHONDRIUM (was only present when cartilage being made)
- isogenic groups organized in parallel lines
where fibrocartilage is found in the body (for example)
intervetebral (IV) discs
IV disc structure
- middle nucleus pulosus (with fibrocartilage on its periphery): gelatinous discoid mass of loose CT
- surrounding annulus fibrosus: dense CT
characteristics of fibrocartilage (how it is different). for ex fibrocartilage in nucleus pulposus of IV disc
- one chondrocyte per lacuna (no isogenous groups so NO INTERSTITIAL GROWTH)
- type 1 collagen* with the type 2 collagen (whereas elastic and hyaline = mostly type 2)
- chondrocyte fct = still ECM prod*
clinical importance of fibrocartilage
hold the nucleus pulposus so that it doesn’t herniate and compress spinal nerves, causing pain
bone constituents
- ECM: fibers (type 1 collagen), amorphous ground substance, calcified material (calcified ECM)
- cells: osteoprogenitor cells (SC) (pre-osteoblast), osteoblasts, osteocytes, osteoclasts
functions of osteocytes, osteoblasts and osteoclasts
- osteoblasts: synthesize organic components of the matrix
- osteocytes: inside lacunae
- osteoclasts: bone resorption and remodelling (+ are multinucleated). diff embryo origin from others, important in osteoporosis
osteoprogenitor cell in the bone: function + what do bone cells arise from
- gives rise to osteoblasts (NOT SC): make organic comp of ECM.
- osteoblasts become osteocytes when they become trapped in the ECM they’re producing
osteoprogenitor (pre-osteoblast), osteoblast, osteocytes originate from what cell
mesenchymal progenitor cell (will produce other things like CT)
osteoclasts originate from what cell
hematopoietic progenitor
steps to get osteoclast from a hematopoietic progenitor cell
- hematopoietic progenitor makes daughter cells
- daughter cells fuse under the influence of the RANKL protein
- after fusion, osteoclast formed
what cells produce RANKL which makes daughter cells of hematopoietic progenitor fuse (to make osteoclasts)
osteoprogenitor cells (pre-osteoblasts) and osteoblasts
substance that INHIBITS the formation of osteoclasts (inhibits the fusion of daughter cells of hematopoietic progenitor) + cells that make it
osteoprotegerin (OPG). produced by osteoblasts
components of the bone ECM produced by osteoblasts
- fibers (type 1 collagen)
- amorphous ground substance (proteoglycans and glycoproteins) (sialoprotein, osteocalcin)
- minerals (crystals of hydroxyapetite)
what allows the calcification of bone (calcification = formation of hydroxapetite)
- sialoprotein and osteocalcin (glycoproteins, by their presence)
- the ECM is saturated in calcium phosphate and, because of these proteins, calcium phosphate will make hydroxyapetite
what is added to bone to remove calcium (hydroxyapetite, calcium phosphate) to allow histo, patho studies (how do you decalcify bone)
either of
-5% nitric acid
-EDTA
+immerse bone in formalin
classification of bone (diff types of bone)
- primary bone (woven bone, nonlamellar)
2. secondary bone (lamellar): either compact (cortical) or spongy
charact of primary bone (woven bone)
- nonlamellar
- in embryo and fetus (first bone produced)
- random collagen fibril orientation
charact of secondary bone in general (compact or spongy)
- start to exist at birth
- lamellar
- oriented collagen fibrils (same orientation)
charact of compact (cortical) bone (a type of secondary bone)
outlines marrow cavities
charact of spongy bone (a type of secondary bone)
- cancellous (means has a porous structure), trabecular
- supports the marrow
where is compact bone (type of 2ndary bone) found in the body
diaphysis of long bones
most exterior region in compact (cortical) bone
periosteum (similar to perichondrium): involved in bone repair
structure interior to periosteum and parallel to it in compact bone
outer circumferential lamella (or system): 3-5 layers of osteocytes (dark, spider or ant like structures)
structure seen inside compact bone
Haversian systems (also called lamellae or osteon) (when bone cut cross section, are circular, cylindrical structures)
what is inside the lamellae (Hav systems)
layers of osteocytes
what is in the middle of a Hav system
Haversian canal
what is the name of the lamella that is between different Haversian systems (lamellae or osteons) but that is not circular, cylindrical ,organized and therefore not called a Hav system
interstitial lamellae (is old Haversian systems being destroyed or removed)
what layer separates bone from the BM and the marrow cavity
endostium (one layer of osteoblasts)
layer right beside the endostium
inner circumferential lamella (or system) (osteocytes running parallel to the endostium)
function of the Haversian canal
allows circulation of blood vessels to provide nutrients to the bone
Volkmann’s canals are what
canals inside Haversian systems* that run perpendicular to the main direction of bone (whereas Haversian canals and systems are parallel to the direction of bone)
Haversian systems (or osteons or lamellae): structures that ‘‘sandwich’’ them in the bone
inner and outer circumferential systems
what do we mean when we say that compact bone is lamellar and collagen fibers run in the same direction in it
inside a lamella, (interstitial, Hav system), all collagen fibers run in the same direction in this lamella (parallel to bone length and to Hav system orientation and Hav canal)
what structure determines the limit of the Haversian system (surrounds it and encloses it)
cement or cementing line
-deposited by osteoblasts at the beginning of the formation of each Haversian system
special characteristics of osteocytes in Haversian system (they form the lamellae (layers) of the system and each one is in a hole called lacuna)
- send cytoplasmic processes towards the Haversian canal (processes sitting in canaliculi/tunnels). the processes allow to bring nutrients and O2, and send wastes)
- do gap junctions with other osteocytes through these canaliculi: good communication between cells
main reason why primary bone (woven, nonlamellar) differs from secondary bone (lamellar)
in embryo and fetus + random collagen fibers orientation all disorganized + see blood vessels
where primary (woven) bone formation always occurs
in mesenchymal plate, in a piece of mesenchymal tissue with mesenchymal cells
how woven bone formation occurs
- mesenchymal cells layer (osteoprogenitor cells) makes a layer of osteoblasts
- some of these osteoblasts become osteocytes
- these osteocytes produce ECM to make the bone grow
- the gap made by an osteoblast that left to go embed itself in the ECM (become an osteocyte) is filled with a new osteoblast coming from a mesenchymal cell (osteoprogenitor cell)
osteocytes charact in woven bone
send cell processes sitting in canaliculi and these processes communicate with osteoblasts and with other osteocytes
bone that is also trabecular, other than primary woven bone
spongy (cancellous, trabecular bone), a type of 2ndary bone, that supports the marrow
where do you find trabecular (spongy) bone in the body
in the adult body, in the metaphysis and epiphysis of long bones
how does spongy bone (type of 2ndary bone) differ from primary, woven bone
in spongy bone, you have layers of lamellar bone with collagen fibers in the lamella running in the same direction (not the case in primary bone)
even though both are called trabecular bone
