Special CT - cartilage and bone (M2) Flashcards
2 types of cells in connective tissue
resident and wandering
what do resident cells include
fibroblasts
adipocytes
mesenchymal stem cells
fixed macrophages
what do wandering cells include
mast cells
plasma cells
free macrophages
other leukocytes (WBCs)
what is extracellular matrix (ECM) secreted by
resident cells
what makes up extracellular matrix
protein fibers:
- collagen fibers
- elastic fibers
- reticular fibers
ground substance:
- water
- glycosaminoglycans (GAGs)
- glycoproteins
- ions
what are resident cells derived from
mesenchymal stem cells
skin resident cells
fibroblasts
cartilage resident cells
chondroblasts, chondrocytes
bone resident cells
osteoblasts, osteocytes
fat resident cells
adipocytes
what are wandering cells part of and derived from
part of immune system.
derived from hematopoietic stem cells (blood), and respond to harmful agents and inflammation
types of wandering cells
mast cells
monocytes and macrophages
neutrophils, eosinophils, basophils
plasma cells
osteoclasts (bone)
what does collagen provide in the ECM
tensile strength to the tissue and anchoring of epithelial tissue
where is collagen synthesized and from what
Synthesized within resident cells - fibroblasts, chondroblasts, osteoblasts, etc.
Golgi complex packages into vesicles as procollagen and expels from cell via exocytosis.
procollagen –> collagen via enzymatic action
how many collagen types are there and what do they differ by
28 types.
differ by morphology and amino acid sequences
what are the 2 physical properties of collagen fibers
fibrillar - structural support - builds tissues.
non-fibrillar - anchors - maintains tissues.
about 90% of all collagen fibers in the human body are comprised of what types of collagen
types 1, 2, and 3 (fibrous collagen)
where is type 1 collagen found
dermis of skin, ligaments, bone, cornea
where is type 2 collagen found
assoc. with hyaline cartilage.
ex. articulating surfaces of bones, nose, trachea
what is type 3 collagen and where is it found
reticular collagen.
assoc. with highly cellular organs including liver, spleen, kidney
what are collagen type 4 and 7 assoc. with
epithelial basement membranes:
- type 4: basal lamina - mesh-like appearance of fibers.
- type 7: basement membrane anchoring fibrils
where is elastin secreted from and as what
secreted from resident cells of elastogenic tissues (ex. fibroblasts) as tropoelastin (soluble)
what does elastin provide for
increased flexibility of connective tissue
what do microfibrils provide
structural scaffold for deposition of tropoelastin (protein)
osmotic properties of ground substance
very high osmotic pressure (about 60 mmHg) of ECM contributes to high viscosity.
- viscous fluid (blood) –> gel/semisolid –> solid (bone).
- high viscosity restricts movement of pathogens throughout tissue
does ground substance have a high or low compressibility and why
low compressibility as GAGs molecules repel each other due to their opposing overall negative charge of the molecules, along with the high osmotic pressure (resists edema)
what 2 things does ground substance influence
fluid transport
metabolic exchange
proteoglycan aggregate
- hyaluronan base
- proteoglycan = protein + GAG
- proteins: core proteins bind to GAGs and linker proteins bind proteoglycan to hyaluronan base.
- common GAGs: heparan/heparan sulfate, dermatan/chondroitin sulfate, keratan sulfate
what is the perichondrium vital for
cartilage growth and maintenance
outer fibrous layer of perichondrium
contains dense connective tissue (+ fibroblasts).
+/- elastic fibers.
blood vessels allow for nourishment of cartilage and inner perichondral layer.
chondrogenic ‘cellular’ layer (inner) of perichondrium
membranous layer that is the thinner of the 2 layers.
contains chondrogenic cells that produce cartilage proper.
cartilage proper is internal and contains chrondroblasts that produce and secrete semisolid ECM.
lacunae are cavities within ECM that contain chrondrocytes
what are chrondrocytes
transformed chrondroblasts that become encapsulated within ECM.
deep in ECM.
larger than chrondroblasts
what are the 2 types of hyaline cartilage growth
interstitial growth
appositional growth
where does interstitial growth start from
center.
limited capacity
where does appositional growth start from
edge.
primary mech. of cartilage growth
3 types of cartilage
hyaline
elastic
fibrous/fibrocartilage
hyaline cartilage
most commonly found.
+ perichondrium (except on articulating bone surfaces).
found in tracheal bands, articulating bone surfaces, forming bone, ex. ribcage and trachea
elastic cartilage
+ perichondrium.
hyaline cartilage with elastic fibers.
found in external ear (pinna), epiglottis.
fibrous/fibrocartilage
no perichondrium –> not much growth.
more of a CT proper.
found in intervertebral discs and some symphyses, ex. hip bones and openings in skull
what can fibrocartilage withstand and what does it keep bones from doing
can withstand compression
keeps bones from fusing
qualities of long bones
greater in length than width and are most common in human.
found in upper and lower limbs.
load bearing
qualities of short bones
nearly equal width and length.
found in hands and feets.
how are bones classified
based on size and shape secondary to their function
qualities of flat bones
thin with smooth surface.
form many bones of the skull - frontal, parietal, occipital, lacrimal, nasal, vomer.
form scapula in shoulder, kneecaps, breastbones, and ribs.
qualities of irregular bones
complex shape.
form vertebrae, hip bones and some skull bones - temporal, zygomatic, maxilla, mandible, sphenoid, ethmoid, palatine, and inferior nasal concha.
3 regions of long bone
epiphysis
metaphysis
diaphysis
where is the epiphysis and what does it contain/is covered by
proximal and distal ends.
contains spongy bone and resists stress.
covered externally by thin layer of hyaline cartilage, ex. articular cartilage.
where is the metaphysis and what does it contain/is covered by
lies between epiphysis and diaphysis.
initially contains thin layer of hyaline cartilage, epiphyseal growth plate, that is eventually replaced by thin line of compact bone (epiphyseal line)
where is the diaphysis and what does it contain/is covered by
cylindrical shaft; middle section.
provides for majority of weight support and leverage.
what makes up compact (cortical) bone
dense with organic ground substance and inorganic salts that contain lacunae
what makes up cancellous (trabecular/spongy) bone
less dense and more porous than compact bone and contains bone marrow
osteoblasts
build bone.
derived from mesenchymal stem cells
osteocytes
maintenance.
derived from osteoblasts
osteoclasts
cleave bone.
derived from hematopoietic stem cells
osteoid
ECM of bone.
provides structural support.
has mixture of organic and inorganic components
organic components of osteoid
mainly comprised of collagen and proteoglycans - provides tensile strength and some flexibility.
supplied by osteoblasts
inorganic components of osteoid
comprised of calcium phosphate and calcium hydroxide that interact to form crystalline hydroxyapatite - provides for bone rigidity –> osteoid is mineralized after this process
functions of bone
protection from trauma.
movement via skeletal muscle attachment.
blood cell production (hematopoiesis) (red bone marrow in adults).
storage for mineral and energy reserves:
- calcium for muscle contraction, neurotransmitter release, clotting of blood, etc.
- phosphate for energy (ATP), phospholipids for cell membranes, DNA/RNA, etc.
what is periosteum and what is it connected to
tough, fibrous, outer connective tissue bilayer.
anchors blood vessels, nerves to bone surface and serves as attachment for ligaments
- outer fibrous
- inner osteogenic (cellular)
what are the sharpey (penetrating) fibers and what are they connected to
anchor periosteum to underlying bone
why is periosteum not found on articulating bone surfaces
don’t want growth of tissue / excessive tissue in joints
compact bone components
osteon (haversian system) is basic structural and functional unit that contains:
- haversian (central) canal
- concentric lamellae
- osteocytes
- lacunae
- canaliculi
non-osteon structures:
- volkmann (perforating) canals)
- circumferential lamellae
- interstitial lamellae
location of spongy bone compared to deep bone
deep
what are the parallel lamellae and trabecular lined with
thin endosteum and osteoblasts
where are lacunae and what do they contain
between parallel lamellae.
contain osteoclasts
what does the medullary cavity contain
bone marrow
intramembranous ossification
bone growth within membrane.
formation of flat and irregular bones .
derived from mesenchymal tissue
endochondral ossification
formation of long and short bones.
derived from hyaline cartilage
major events of endochondral ossification
- hyaline cartilage develops
- cartilage calcifies and bone collar forms
- primary ossification center forms in bone shaft (diaphysis) - blood vessels start to invade cartilage model
- secondary ossification center forms at ends of long bone (epiphyses)
- bone replaces cartilages except in articular area and epiphyseal plate (growth plate)
- interstitial growth continues into adolescence when epiphyseal plate ossifies (growth plate closes)
what is growth plate critical for
interstitial growth of long and short bones
what are the 5, distinct zones of the epiphyseal (growth) plate
- reserve (resting) cartilage
- proliferation
- maturation
- hypertrophy
- degeneration/calcified cartilage
- ossification
reserve (resting) cartilage zone
most distal from diaphysis.
contains healthy hyaline cartilage
proliferation zone
cartilage cells undergo mitotic division to form ‘stacks’ of cells secreting ECM.
easily stains with alcian blue (stains GAGs)
maturation zone
cessation of mitotic activty
hypertrophy zone
enlargement of chondrocytes
degeneration/calcified cartilage zone
ECM calcifies
ossification zone
zone closest to diaphysis where bone formation occurs.
zone invaded by blood vessels and osteogenic cells that secrete osteoid.
where and when does appositional growth of long bone occur
within the inner layer of the periosteum as osteoblasts secrete collagen and ECM that forms external circumferential lamellae
lifetime growth
what do osteoclasts do at the same time as appositional growth of long bone
reabsorb bone within medullary cavity –> widening it
steps of bone repair
- hematoma transforms into a connective tissue procallus containing fibroblasts that produce collagen that will reconnect the broken ends of the bone while regenerated blood vessels invade hematoma
- chondroblasts in the connective tissue assist to form a fibrocartilaginous (soft) callus
- osteoprogenitor cells invade this callus and replace it with bone (hard callus)
- osteoclasts remove any excess bone during remodeling to leave only a slight thickening in area of the fracture… trying to go back to the way it was pre-fracture
what is calcitonin
peptide hormone synthesized and secreted by thyroid gland parafollicular cells (“C” cells)
what does calcitonin cause
increased Ca2+ plasma levels –> inhibition of bone resorption (breakdown of bone).
- osteoclast activity decreased
- Ca2+ deposition in bone increased
what is parathyroid hormone (PTH) secreted by and in response to what
secreted by chief cells in parathyroid glands in response to decreased plasma Ca2+ levels
major actions of parathyroid hormone (PTH)
- increased Ca2+ reabsorption from urine in the kidneys (promote bone growth)
- formation of calcitriol hormone in the kidneys via enzymatic action, which stimulates Ca2+ (& Mg2+ and phosphate) absorption in the small intestine
- Ca2+ resorption from bone via increased osteoclast activity
what is calcitriol hormone
active form of vitamin D3
2 ways to acquire vitamin D3
dietary intake.
conversion of cholesterol derivative by UV light within keratinocytes
what happens to cholecalciferol in the liver
enzymatic action converts cholecalciferol to a pre-active form of vitamin D3
what does formation of calcitriol hormone stimulate
stimulates Ca2+ (& Mg2+ and phosphate) absorption in the small intestine
PTH and calcitriol effects on bone health
PTH and calcitriol potentiate each other on bone reabsorption.
calcitriol helps in remineralization of bone
how are plasma PTH levels affected by plasma Ca2+ levels
low plasma Ca2+ levels –> elevated plasma PTH levels.
increased plasma Ca2+ levels –> drop in plasma PTH levels.
how are plasma calcitonin levels affected by plasma Ca2+ levels
plasma calcitonin rise in response to increasing plasma Ca2+ levels
aging affects on bone
osteopenia vs. osteoporosis.
decreasing osteoblast activity and loss of vital minerals required for healthy bone.
decrease in certain hormones (ex. growth hormone, estrogen/testosterone, and vitamin D) (more pronounced in females).
osteoporosis management with bisphosphonates as it blocks osteoclast activity:
- alendronate
- ibandronate
- risedronate
- pamidronate
- bisphosphonate derivative: zoledronic acid
