Bone/Cartilage Histo Lab Flashcards
Cartilage is a specialized type of
specialized type of connective tissue
composed of chondrocytes embedded in a firm gel-like ground substance or matrix containing fibrous macromolecules
is cartilage vascular or avascular?
AVASCULAR
what is the main function of cartilage?
to support soft tissue
what are other functions of cartilage?
-shock absoprtion
-friction-free sliding surfaces for joints
-model for long bones during development
-essential for growth of long bones during childhood
what are the three types of cartilage?
hyaline
elastic
fibrocartilage
chondrocytes
-major cell type in cartilage
- reside within lucunae
- secrete components of ground substance
- appear quiescent but continue to interact with cart. matix
-required to maintain molecular integrity of matrix
cartilage components
chondrocytes
ground substance (chondroitin, collagen II)
chondroitin
cartilage ground substance contains chondroitin which gives tissue elasticity and flexibility
what type of collagen is in cartilage?
Collagen II
does cartilage sense injury/damage?
no
it is aneural (no sensation to injury or damage)
functions of cartilage
-resist compression forces
-enhances bone resilience
-provides support on boney areas -where there is a need for flexibility
-acts as a “shock absorber”
what does cartilage derive from?
mesoderm
where is hyaline cartilage found?
trachea
bronchi
larynx
nose
articular bone surfaces
ventral ends of ribs
transient skeleton model
epiphyseal growth plate
where is elastic cartilage found?
auricle of the ear
Eustachian tubes
epiglottis
larynx
where is fibrocartilage found?
intervertebral discs
pubic symphysis
some ligaments
meniscus
hyaline cartilage objects of identification
chondrocytes
perichondrium
interterritorial matrix
territorial matrix
septum
lacuna
isogenous group
elastic cartilage objects for identification
chondrocytes
isogenous group
perichondrium
elastic fibers
fibrocartilage objects for identification
chondrocytes
annulus fibrosus
symphysis pubis
nucleus pulposis
Fibrocartilage characterisitcs
-matrix is rich in Type I collagen fibers (as in dense connective tissue)
-contains Type II collagen fibrils (characteristic of all types of cartilage)
-fibers are more abundant than the ground substance
-fewer cells than in the other types of cartilage: cells are aligned in long rows between bundles of collagen
-NO perichondrium
hyaline cartilage characteristics
This is hyaline cartilage, with the following characteristics:
-chondrocytes in isogenous -groups/aggregates
-more cells in isogenous groups
-no large fibers
-most hydrated matrix
-“glassy”, transparent look
Which is the predominant type of collagen found in cartilage?
Collage II
In which region of the epiphyseal plate is active cell division and matrix production most prominent during endochondral ossification?
Zone of proliferating cartilage
Zone of proliferating cartilage is characterized by
-active cell division and matrix production
-Chondrocytes in this zone undergo rapid mitosis, leading to the longitudinal growth of the bone during endochondral ossification
What histological feature distinguishes fibrocartilage from hyaline cartilage?
Fibrocartilage is distinguished by its ABUNDANT COLLAGEN I FIBERS
Cartilage ground substance:
-not mineralized
-texture is like very firm Jello®
-contains proteoglycans and
-responsible for:
–the stiffness of cartilage
–incompressibility
–flexibility (compared to bone)
bone components
bone cells
-osteoprogenitor (stem)
-osteoblasts (formation)
-osteoclasts (resorption)
-osteocytes (mechanosensing)
extracellular organic matrix
extracellular inorganic matrix
osteoprogenitor cells
Stem cells of bone
-retain the ability to re-differentiate into osteoblasts
-reside in the bone canals, endosteum, periosteum, and marrow
-regulate the influx and efflux of mineral ions into and out of the bone matrix
-responsible for the formation of bone remodeling compartments
osteoblasts
Bone forming bone cells
-regulate osteoclastogenesis and osteocyte formation
-synthesize and secrete:
- osteoid: bone matrix
-alkaline phosphatase to regulate bone mineralization
-nucleators for bone mineralization
–dentin matrix protein (DMP-1)
–bone sialoprotein
- calcium and phosphate binding proteins to regulate deposition of mineral:
–osteocalcin
–osteonectin
osteoclasts
bone resorbing cells
- multinucleated cells derived from mononuclear monocyte-macrophage cells
- secrete:
—-hydrogen ions: acidify the resorption compartment beneath osteoclasts to dissolve the mineral component of the bone matrix
—-tartrate-resistant acid phosphatase (TRAP) + cathepsin K enzyme
—digest the proteinaceous matrix
osteocytes
mechanosensing bone cells
90% of bone cells
- terminally differentiated
- reside within canalicular system
- express osteocalcin/bone matrix proteins
bone extracellular organic matrix components
Type I Collagen
glycoproteins
growth factors: osteocalcin, osteonectin, bone sialoptrotein
how much of the bone volume is extracellular organic matrix?
over 90% of bone volume
bone extracellular inorganic matrix minerals
Calcium (99%)
Phosphorus (85%)
Magnesium
Sodium
function of extracellular organic matrix of bone
gives form
provides resistance
extracellular inorganic matrix functions
strength
stiffness
resistance to compressive forces
what part of bone is hydroxyapatite?
bone extracellular INORGANIC matrix
skeletal functions of bone
- provides body support and attachment of muscles and tendons
- body movement
- organ protection from injury
- houses and protects the bone marrow within its cavities
- reservoir of minerals such as calcium and phosphate
extraskeletal functions of bone
- hematopoiesis (including lymphopoiesis, myelopoiesis and megakaryopoiesis)
- endocrine function: bone regulates
-systemic mineral metabolism
-glucose and energy metabolism
-embryonic brain development and adult brain function
embryology of bone
mesodermal germ layer and neural crest
2 major processes to make bone
- intramembranous ossification: direct convertion of mesenchymal tissue to bone
- endochondral ossification: mesenchymal (neural crest) –> cartilage –> bone
What is the most common metabolic bone disease?
osteoporosis
in adult bone, collagen fibers are oriented:
parallel to each other
Which of the following cells in adult bone is derived from the same lineage as Kupffer cells of the liver?
osteoclasts
Which of the following phrases about intramembranous ossification is correct?
gives rise to spongy bone only
occurs directly within mesenchyme
requires an intermediate cartilage model
converts the epiphyseal plate to bone
is responsible for lengthening of long bones
occurs directly within mesenchyme
Which of the following structures represents the basic structural unit of compact bone?
interstitial lamella
trabecula
diaphysis
osteon
lacuna
OSTEON
The cells most active in the synthesis and secretion of osteoid are:
osteoblasts
most predominant type of collagen in bone
Collagen I
secreted by osteoblasts
The blood clot initially forms at the site of a bone fracture is next replaced by what?
hyaline cartilage and connective tissue
decrease in bone mass is due to…
increased osteoclasts
decrease osteoblasts
trabeculated/compact adult bone organization (lamellar, woven)
Lamellar/Lamellar
what growth process is responsible for the width of long bones?
intramembranous ossification
what growth process if responsible for the length of long bones?
endochondral ossification
Somatotropin
bone growth hormone
osteopetrosis
“marble bone disease”
failure of osteoclasts to resorb bone at normal rate
The proper assembly of collagen triple helices requires what kind of post-translational modification reactions?
hydroxylation
first step in fracture repair
formation of a hematoma
in healthy bone, caniliculi are most like to contain:
osteocytic processes
Chondrocyte
Resident cells of cartilage
Chondrocytes in hyaline cartilage produce type II collagen
hyaline cartilage function
Give supporting structure to airways, provide gliding surfaces for joints
hyaline cartilage location
Large airways of the respiratory tract, articular surfaces of bones
hyaline cartilage identification
- Contains a greater number of isogenous groups than elastic cartilage or fibrocartilage.
- Look for nearby pseudostratified ciliated columnar epithelium to hint that you’re in the respiratory tract
hyaline cartilage (larynx)
Hyaline cartilage (trachea)
isogenous group
A nest of chondrocytes, which all arose from the same parent cell
septum
A thin band of matrix that separates chondrocytes within the same isogenous group
territorial matrix
interterritorial matrix
lacuna
Territorial matrix: Darkly-staining regions of matrix that surround chondrocytes and isogenous groups.
Interterritorial matrix: Lighter staining matrix present between groups of cells. This matrix contains fewer glycosaminoglycans and more collagen than territorial matrix.
Lacuna: Cavities within that matrix that house chondrocytes
elastic cartilage function
Composed of elastic fibers, which allow the cartilage to provide strength and flexibilit
elastic cartilage location
earlobe and epiglottis
elastic cartilage identification
- look for darkly staining elastic fibers.
- Compared to hyaline cartilage, elastic cartilage has a higher ratio of cells to matrix, fewer isogenous groups, and more individual chondrocytes
elastic cartilage (earlobe)
elastic cartilage (epiglottis)
fibrocartilage function
- Provides higher tensile strength and firmer support than the other types of cartilage.
- Fibrocartilage in the intervertebral disks forms a ring of cartilage called the annulus fibrosus, which surrounds the soft nucleus pulposus on the interior
fibrocartilage location
pubic symphysis
intervertebral disc
fibrocartilage identification
- Fewer cells and more fibers present than hyaline or elastic cartilage
- Cells can be seen
arranged in rows between fibers.
fibrocartilage (pubic symphysis)
fibrocartilage (intervertebral disc)
perichondrium identification
- a layer of dense connective tissue that covers cartilage structures
- fibrocartilage is not
associated with a perichondrium
elastic cartilage perichondrium
hyaline cartilage perichardrium
spongy/trabecular bone location
interior marrow cavity of bone
spongy/trabecular bone identification
presents a porous bone structure, which is composed of thin supporting segments of
bone called trabeculae
what type of bone is this?
spongy/trabecular bone
compact/cortical bone location
outer portion of solid bone
compact/cortical bone identification
composed mainly of solid osteoid bone matrix, osteocytes, and connecting canals
what type of bone is this?
cortical/compact bone
osteoblast, osteoclast, osteocyte
Osteoblast: Responsible for secreting osteoid and building the solid bone matrix. These cells are dark
and exist on the edges of newly-forming bone. Once they become encased in the matrix, osteoblasts
become osteocytes.
Osteoclast: Large cells with multiple nuclei. Osteoclasts are responsible for breaking down the bone
matrix secreted by osteoblasts to facilitate bone remodeling.
Osteocyte: The main resident cells of bone. They maintain the bone matrix and are surrounded by
osteoid on all sides
osteoblast
secreting osteoid and building the solid bone matrix
osteoclast
breaking down the bone matrix to facilitate bone remodeling
osteocyte
maintain bone matrix and surrounded by osteoid on all sides
inner and outer circumferential lamellae & periosteum
Inner/outer circumferential lamellae: Parallel layers of bone that surround the inner and outer surfaces of compact bone
Periosteum: The outermost layer of bone. It contains blood vessels and nerves that serve the underlying
bone
osteon
functional unit of bone
consists of a central Haversian canal and concentric layers of surrounding bone lamellae
haversian canal
canals that run through compact bone parallel to the long axis
they contain blood vessels that support osteocytes and bone matrix
endosteum
thin layer of tissue that covers the innermost surfaces of bone, including the interior of the Haversian canals
interstitial lamellae
parallel layers of bone that fill the area between individual osteons
Volkman’s canal
canals that run through compact bone perpendicular to the long axis
connect haversian canals
intramembranous ossification
Osteoblasts deposit bone matrix directly, without cartilage models.
endochondral ossification
Cartilage models of bones are first laid down by chondroblasts, the osteoblasts replace the
cartilage with bone matrix.
Long bones increase in length by endochondral ossification and increase in width by intramembranous ossification
This process also forms flat bones, such as the bones of the skull
endochondral ossification zone of…
Zone of resting cartilage: Chondrocytes in this zone serve as a reservoir of cells
Zone of proliferation: Chondrocytes are actively dividing which creates columns of cells
Zone of maturation of hypertrophy: Chondrocytes stop dividing and begin to swell
Zone of calcification and cell death: The matrix begins to calcify and the chondrocytes die
Zone of ossification: Osteoblasts invade and begin creating woven bone on the calcified matrix
