Group 8/7/19 Flashcards
Learning issues
Learning issues:
- Anatomy of forearm (elbow to knuckles, bones, muscles, tendons, ligaments)
- Bones (structure, development, healing)
lateral epicondylitis cause and sign*
- cause: overuse of muscles that attach to the lateral epicondyle, called “tennis elbow. Microtears of the proximal attachment of the extensor muscles
- sign: pain over lateral epicondyle
medial epicondylitis cause and sign*
- similar to lateral, but at medial epicondyle
- called “golfer’s elbow”
anatomical snuffbox: appearance and composition involved*
- triangular depression of posterolateral wrist
- formed by abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus tendons
which bones develop from intramembraneous ossification vs. endochondral ossification*
- intramembraneous develops bones of calvarium, facial bones, and clavicle
- endochondral ossification develops bones of axial skeleton, appendicular skeleton, and base of skull
major difference between long vs. short bone growth
- long bones go through endochondral ossification and develop a primary and secondary ossification center
- short bones only develop a primary ossification center (except for the calcaneus, has secondary)
major structural parts of the long bone
- epiphyses are the swollen ends of bone
- diaphysis is the middle, shaft part
- compact bone envelopes
- spongy bone inside the swollen ends
- medullary cavity within the shaft
synostosis
process by which diaphysis fuses with epiphysis during long bone growth, stops the growth of the bone
bone matrix structure and function
- matrix has mineral calcium phosphate in the form of hydroxyapatite crystals, type 1 collagen, and other noncollagenous proteins
- makes it a hard tissue that provides support and protection
lacunae
spaces within the bone matrix
osteocyte, definition and location
- the mature bone cell enclosed by bone matrix that was previously secreted as an osteoblast
- located within the lacunae and canaliculi
canaliculi
tunnels within the mineralized matrix of bone that connect adjacent lacunae and allow contact between neighboring osteocytes
osteoprogenitor cells
derived from mesenchymal stem cells in the bone marrow, give rise to osteoblasts
osteoblasts: what are they, what do they differentiate from, what are measurers of their activity*
- cells that build bone by secreting type 1 collagen and catalyzing mineralization in alkaline environment via ALP (an enzyme), they make extracellular matrix of bone.
- differentiate from mesenchymal cells in the periosteum
- osteoblastic activity is measured by bone ALP, osteocalcin, propeptides of type 1 procollagen
osteoclasts function and origin*
- Dissolves (“crushes”) bones by secreting H+ and collagenases, resorbs bone
- Differentiates from fusion of monocyte/macrophage lineage precursors.
- Markedly acidophilic
types of bone
compact (dense) or spongy (cancellous)
compact bone
compact, dense layer that forms the outside of the bone
spongy bone
sponge-like meshwork that has trabeculae and forms the interior of the bone
periosteum
a sheath of dense fibrous connective tissue that covers the bone, except in areas where bones touch each other
contains osteoprogenitor cells
endosteum
- the lining tissue of the compact bone that faces the marrow cavity and the trabeculae of the spongy bone within the cavity
- contains osteoprogenitor cells that differentiate into osteoblasts
red bone marrow
contains blood cells and reticular cells and fibers that support the developing blood cells and vessels
yellow marrow
located in the marrow cavity, more common in adults
contains fat cells
osteon
mature bone is composed of cylindrical structural units called osteons (Haversian systems)
lamellae
circles within the osteon that surround the Haversian canal
Haversian canal
longitudinal canals at the center of the osteon that contains the vascular and nerve supply of the osteon
lamellar bone
another name for mature bone
perforating (Volkmann) canals
- span the lamellar bone horizontally
- allows blood vessels and nerves to travel between endosteal and periosteal surfaces
nutrient foramina
- openings in the bone through which blood vessels pass to reach the marrow
- arteries will use these to enter the marrow cavity and provide blood to bone shafts
nutrient arteries
- come from the periosteal buds during development
- supply diaphysis and epiphysis with blood
what is the major difference between endochondral and membranous ossification?*
- in endochondral ossification, a cartilaginous model of bone is first made by chondrocytes. Then osteoclasts and osteblasts replace the model with woven bone, which is remodeled to lamellar bone
- in membranous ossification, woven bone is formed directly without cartilage. Later, it’s remodeled to lamellar bone.
what will stimulate vs. inhibit osteoclast activity?*
- RANKL (RANK ligand that is secreted by osteoblasts) will stimulate RANK receptors on the osteoclasts.
- RANK receptors can be blocked by OPG (osteoprotegerin, a RANKL decoy receptor), to decrease osteoclast activity
parathyroid hormone function*
- secreted by the parathyroid glands, regulates calcium and phosphate levels in extracellular fluid.
- at low, intermittent levels, exerts anabolic effects (building bone) on osteoblasts and osteoclasts (indirect)
- chronically elevated levels of PTH can lead to hyperparathyroidism and cause catabolic effects
estrogen function*
inhibits apoptosis in bone-forming osteoblasts and induces apoptosis in bone-resorbing osteoclasts
causes closure of epiphyseal plates during puberty
estrogen deficiency effect*
elevated cycles of bone remodeling and bone resorption, which increases risk of osteoporosis
most commonly fractured carpal bone, cause, and effect*
- scaphoid, FOOSH
- complications of proximal scaphoid fractures include avascular necrosis and nonunion due to retrograde blood supply.
dislocation of which carpal bone can cause acute carpal tunnel syndrome?*
lunate
carpal tunnel syndrome: cause and signs*
cause: entrapment of median nerve in carpal tunnel (between transverse carpal ligament and carpal bones), causes nerve compression
signs: paresthesia, pain, numbness in median nerve. Thenar eminence atrophies, but still has sensation. Positive Tinel sign (percussion of wrist causes tingling), Phalen manuever (90 wrist flexion causes tingling)
thenar vs hypothenar eminence location*
thenar eminence is oval area under thumb; hypothenar eminence is oval area under pinky
thenar eminence innervation*
median nerve
thenar eminence muscles and actions*
OAF: Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis
OAF: Oppose, Abduct, and Flex
hypothenar eminence innervation*
ulnar nerve
hypothenar eminence muscles and actions*
OAF: Opponens digiti minimi, Abductor digiti minimi, Flexor digiti minimi brevis
OAF: Oppose, Abduct, Flex
muscles that abduct the fingers, and innervation*
DAB: dorsals abduct
dorsal interossei muscles, innervated by ulnar nerve
muscles that adduct the fingers, and innervation*
PAD: palmars adduct
palmar interossei muscles, innervated by ulnar nerve
what are the muscles that flex at the MCP joint, extend PIP and DIP joints, and their innervations?*
lumbrical muscles are on the metacarpal bones
1st and 2nd innervated by median; 3rd and 4th innervated by ulnar
osteoid
the initial unmineralized bone, will undergo mineralization triggered by matrix vesicles
how do osteoblast processes communicate with each other?
gap junctions
what forms in the bone under an osteoclast?
resorption bay (Howship lacuna)
calcitonin: what is it secreted by, and what is its effects?*
secreted by parafollicular cells of the thyroid gland.
Inhibits bone resportion, inhibiting effect of PTH on osteoclasts. Decreases elevated blood calcium levels to normal.
osteoblast cell morphology
cuboidal or polygonal, mononuclear cell; basophilic cytoplasm; negative Golgi
osteocyte cell morphology
small, oval, mononuclear cell; pale cytoplasm; long cell processes
osteoclast cell morphology
large, multinuclear cell; acidophilic cytoplasm; ruffled border; underlying Howship lacuna
how do osteoblasts modulate the local concentration of phosphate ions in the bone matrix?
osteoblasts regulate the activity of an enzyme TNAP, tissue nonspecific alkaline phosphatase, which hydrolyzes phosphate groups
what ions must increase in the extracellular matrix before mineralization can occur, and how does this happen?
- Ca2+ and PO4 ions must be accumulated in the extracellular matrix
- osteocalcin binds to Ca2+, higher Ca2+ concentration causes osteoblasts to secrete more TNAP, to increase phosphate ion concentration
two processes by which a bone fracture can repair
direct (primary) or indirect (secondary) bone healing
direct (primary) bone healing
fractured bone is surgically stabilized with compression plates, to restrict movement
bone undergoes internal remodeling. Osteoclast cutting cones cross fracture line, create longitudinal resorption canals, filled with osteoblasts
indirect (secondary) bone healing
involves periosteum and surrounding soft tissues, endochondral and intramembraneous ossification
will occur with nonrigid or semirigid bone fixation
process includes fracture hematoma -> soft callus -> hard callus -> bone remodeling
what is initially formed after a bone fracture?
fracture hematoma: collection of blood that surrounds the fractured ends of the bone
what does a fracture hematoma become next?
gradually replaced with granulation tissue, a loose connective tissue that has collagen type 3 and 2 fibers
what does the granulation tissue become next?
granulation tissue transforms into fibrocartilaginous soft callus, giving fracture site a stable, semirigid structure
what does the soft callus become next?
a hard callus: formed from osteoprogenitor cells from the periosteum, differentiate into osteoblasts, lay down osteoid. Initially is spongy bone, gradually replaced by compact bone. The hard callus is more solid and rigid.
bone remodeling
happens after the hard callus develops. Transforms the new woven bone into lamellar mature bone. Osteoclasts resorb the hard callus.
how long does bone healing usually take, what can expedite the process?
usually takes 6-12 to heal bone in healthy individuals
expedited by setting the bone (reapproximating the normal anatomic configuration), and holding the parts in place by internal fixation (pins, screws, plates) or external fixation (casts, pins, screws)
the junction between the diaphysis and epiphysis
metaphysis
what is used to connect the periosteum to the outer surface?
Sharpey fibers
what process elongates endochondral bone?
interstitial growth of cartilage on the epiphyseal growth plate
guyon canal syndrome*
- compression of the ulnar nerve at the wrist. Usually seen in cyclists due to pressure from handlebars
- Guyon canal includes the ulnar nerve and ulnar artery
when is clawing sign likely to be seen, what kind of nerve damage?*
distal lesions of median or ulnar nerves
“ulnar claw” location of lesion, presentation and context*
lesion of distal ulnar nerve
when the person asked to extend fingers, they aren’t able to extend the 4th and 5th digits
“popes blessing” location of lesion, presentation and context*
lesion of proximal median nerve
when the person asked to make a fist, they can’t flex their 1st-3rd digits
“median claw” location of lesion, presentation and context*
lesion of distal median nerve
when person asked to extend their fingers, their 2nd and 3rd digits remain flexed
“OK gesture” location of lesion, presentation and context*
lesion of proximal ulnar nerve
when person asked to make a fist, their 4th and 5th digits remain extended
de quervain tendosynovitis*
noninflammatory thickening of the abductor pollicis longus and extensor pollicis brevis tendons. Person has pain or tenderness at radial styloid. Positive Finkelstein test (pain at radial styloid with active or passive stretch of thumb tendons)
ganglion cyst*
fluid filled swelling overlying joint or tendon sheath, most commonly at dorsal side of wrist. Arises from herniation of dense connective tissue.
radial head subluxation (nursemaid’s elbow)*
common elbow injury in children under 5. Caused by a sudden pull on the arm, so immature annular ligament slips over the head of the radius. Injured arm held in flexed in pronated position.
bones of the wrist*
- start at the more proximal region, thumb side, move across, then from distal region back across
- “so long to pinky, here comes the thumb”: scaphoid, lunate, triquetrum, pisiform, hamate, capitate, trapezoid, trapezium
metacarpal neck fracture*
also called Boxer’s fracture. Common fracture caused by direct blow with a closed fist. Most commonly seen in 4th or 5th metacarpal.
which tendons are inside of the carpal tunnel, where is this located?*
- carpal tunnel is located in the middle of the plane of the wrist
- flexor digitorum profundus tendons are dorsal
- flexor digitorum superficialis tendons that are palmar
- median nerve and flexor policus longus tendons are lateral, towards the thumb side
