Unit 2 - Skeletal System Flashcards
Function of bone
Support: framework
Protection: surrounds organs
Leverage: muscle site attachments
blood cell production : ‘hematopoiesis’
mineral storage: esp. calcium (required for contraction, milk, clotting)
bone characteristics
2nd hardest body substance (enamel first)
can remodel and repair itself
made up of cells in matrix
bone cell life cycle
start as osteoblasts
produce matrix of collagen + ground substance
blasts harden the matrix by adding crystalline calcium and phosphate salts (ossification)
blasts become trapped in small spaces in matrix (lacunae)
blasts now considered ‘osteoctyes’
hormones controlling calcium
calcitonin: thyroid gland, prevents blood levels from getting too high by placing calcium in bones
parathyroid hormone: parathyroid glands, prevents blood levels from getting too low by removing calcium from bones
osteoblasts
form bone
- secrete matrix
- add minerals to ossify
osteocytes
blasts trapped in the ossified matrix
- revert back if needed (injury)
osteoclasts
eat away bone
- allow body to withdraw calcium for use
2 bone types
compact
cancellous (spongy)
parts of a long bone
compact bone
dense
shaft of long bones, outside of all
permeated by microscopic framework of tunnels, channels (nourish bone) surrounded by hard matrix
osteon/haversian system
functional + structural unit of compact bone
1-2 capillaries
around each central haversian canal are concentric rings of matrix (‘lamellae’)
small hollow cvaities (lacunae) between lamellae
series of tiny hollow tunnels (canaliculi) join central (haversian) canal to lacunae + lacunae to each other, nourish
groups of osteons in parallel arrangement
perforating volkmann’s canals penetrate bone and connect haversian canals to osteons
cancellous bone
continues on from compact bone, no clear demarcation
less histologically organized
trabeculae AKA spicules: series of branching plates of matrix, interconnect and make caves that store fat (bone marrow) - reduce weight of bone - supports from pulling forces - punctuated by lacunae and blood vessels (nourshment)
long bone
longer in one direction
levers, support, site for muscle attachment
parts of long bone
p 177
epiphyses
enlarged ends of long bones
primarily made of cancellous bone
diaphysis
shaft of long bones
mostly compact
epiphyseal plate (growth plate)
between epi + diaphysis
layer of dividing cartilage
ossifies with age, weak until then
periosteum
fibrous membrane covering compact bone (except at articular surfaces)
anchored by collagen fibers embedded in outer lamellae
fibrous outer layer + inner osteogenic layer (new bone-forming cell source)
important for healing and growth of diameter
endosteum
lines inner surface of bone
contains osteoblasts
assists healing
articular cartilage
smooth layer of hyaline cartilage on articular surfaces of epiphysis
reduces joint friction
short bones
cuboid
no marrow cavity, just cancellous
absorb shock
eg. tarsus
flat bones
protect organs
attachment for large muscle groups.
eg. ribsm scapula, pelvis, cranial
irregular bones
anything thats not long, short, or flat
sesamoid (embedded in tendon, eg patella, fabellae)
condyles
large round
mainly in femur, humerus, occipital
head
single spherical portion @ prxoimal epiphysis of humerus, femur, ribs
‘ball’ of ball and socket joints
united to shaft by a ‘neck’
facet
flat, allows for rocking
in carpal/tarsal, vertebrae
processes
general term for bumps, the greater the process the more powerful muscular pull
articulating processes: heads, condyles (smooth)
non articulating: site for attachment (rough surface)
eg. trochanter on femur, tubercle on humerus
foramen
hole for nerve/vessel to pass
except obturator foramen (largest in body) which exists to decrease pelvis weight
fossa
depressed area
usually for muscles/tendons
bone blood supply
from vessels in periosteum
penetrate through volkmanns canals (run at right angles to long bones) -> haversain canals (run parallel), allows for nutrition to osteocytes
nutrient foramen: large channel of blood vessels -> marrow
bone marrow
fills space in diaphysis of long and spicules of cancellous
red
yellow
red marrow
hematopoietic
young animals
smaller parts in older animals (end of long bones, pelvis, sternum)
yellow marrow
mostly adipose
adults
doesn’t make blood cells, but can revert to red if needed
endochondral bone formation
grows into and replaces cartilage framework
most common, how bones grow in fetus
begin ossifying at center of long bone (primary growth center)
epiphysis = secondary growth center
body lays down cartilage on epi side of growth plate, blasts ossify it on the diaphyseal side
epihyseal plates ossify too once animal mature (‘united anoconeal process’ = elbow problem in large dogs)
*why new puppies can’t have vigorous exercise
intramembranous bone formation
develops from fibrous tissue membranes
happens in some skull bones
fiber covers brain of fetus, then ossified
bone homeostasis
bones constantly remodelling
osteoclasts destroy bone (allows for rebuild)
blasts build bone
mineral levels controlled by hormones
bone building minerals + vitamins
calcium + phosphorous
magneisum
manganese
copper
Vit D, A
bone building hormones
parathyroid hormone
- increases blood calcium levels (stimulates release from bone)
- inhibits calcium excretion by kidneys
- stimulates calcium absorption in intestine
calcitriol (vit D)
- increases calcium
- inhibits calcium excretion by kidneys
- stimulates absorption of calcium by intestine
calcitonin
- decreases
- inhibits release of calcium from bone
- stimulates calcium excretion by kidneys
growth hormone:
- general tissue growth
- stimulates epiphyseal cartilage
- stimulates calcium excretion by kidneys
- stimulates calcium absorption by intestine
insulin
- bone formation
sex hormones (estrogen + testosterone)
- stop longitudinal growth by degenration epiphyseal plates
- bone formation
- estrogen prevents osteoporosis
glucocorticoids (cortisol + aldosterone)
- suppresses calcium absorption
- decreases blood calcium concentrations
- weakens bone
3 dog skull types
dolicocephalic: long (collie)
mesocephalic: moderate (lab)
brachycephalic: short (pug, also persian cats)
bracycephalic
defective teeth (over crowding)
difficulty breathing (distorted nasal bones)
shallow eye sockets
dystocia (difficult birth)
cornual process
horn in cattle that extends into frontal sinus
dehorning can result in frontal sinus being exposed to infection
horse turbinates
prone to bleeding when passing stomach tube through
spine developmental issues
spina bifida: cleft/space in dorsal part of vertebral column
hemi vertebrae: failure of vertebral body to ossify -> improperly formed.
curvature of spine
wobblers (cervical vertebral instability): narrowing of spinal canal in cervical region, compresses spinal cord, caused by genetics/growth rate
- common in horses and great danes
- signs: ataxia (uncoordination), looks wobbly
- can progress to paralysis
angular limb deformities in foals
congenital or acquired neonatal
- usually affects carpus
- can be distal radial physis/growth plate (tarsus)
- cause distal portion of limb to deviate either laterally or medially
premature closure of physis (growth plate)
usually radius and ulna
causes bowing
mandible species differences
dogs + cats: 2 sides united by cartilaginous joint ‘mandibular symphysis’.
horse: fused
scapula species differences
well developed in ungulates
poorly developed in carnivores
radius and ulna species differences
cat + dog: separate
horse + ruminants: fused
carpus species differences
generally 8 bones.
cat + dog: radial and intermediate fused.
ruminants: 1st missing, 2nd and 3rd fused
horse: 1st MAY be missing
metacarpal species differences
5, numbered 1-5 medial -> lateral
carnivore: MC 1 non-weight bearing
ruminants: MC 1 + 2 missing, 3 + 4 fused ‘cannon’, MC 5 vestigial (no digit)
horse: MC 1 + 5 missing, 2 + 4 reduced ‘splint’, MC 3 only weight supporting digit (cannon)
digits species differences
carnivores: 2 3 4 5 bear weight
ruminants: 3 4 bear weight, 2 5 vestigial remnants
horse: 3 bears weight (P1: long pastern, P2: short pastern, P3: coffin)
sesamoid bone - horse
proximal ones in fetlock region (distal MC and proximal phalanx junction)
distal one (‘navicular’) junction of middle and distal phalanx
femur species differences
trochlear tubercle: very prominent in horse (part of stay apparatus)
greater trochanter of horse divided into cranial and caudal
tibia/fibula species differences
carnivores: 2 distinct bones
ruminants: fibula poorly developed but head fused to tibia, distal epiphysis separate
horse: fibula poorly developed, head separate from tibia, distal epiphysis fused
tarsus species differences
2 rows, 5-7 bones
ruminant: central and T4 fused, T2 T3 separate
horse: T1 T2 fused
metatarsal species differences
carnivores: MT1 even smaller than MC1
ruminants: MT5 missing, MT 3 4 fused
feline: metatarsal much longer than metacarpals
digits
horse: distal phalanx (coffin) longer + less rounded
carnivores: 1st digit (dewcaw) usually absent, but MAY be present or even double
joints
union or junction of 2+ bones
arthro = joints
fibrous, cartilaginous, and synovial
fibrous joints
bones held together by fibrous tissue
no movement
often ossify with age (fibrous only when young)
eg. suture between skull bones
cartilaginous joints
bones held by cartilage
slight rocking/gliding movement
eg. intervertebral discs, pelvic symphysis, mandibular symphysis
synovial joint (diarthrodial) parts
freely moving
made of articular cartilage, joint cavity, joint capsule, ligaments
articular cartilage: covers ends of bones, cushioning, smooth (reduces friction)
joint cavity: space in joint with synovial fluid
joint capsule: 2 layers -
outer: fibrous tissue membrane
inner: synovial membrane, makes fluid
synovial fluid: transparent, lubricates joint
ligaments: bone to bone
- intracapsular: inside joint capsule
- extracapsular: outside capsule or forming part of capsule
meniscus: cartilaginous pad in stifle joint and in mandibular joint
synovial joint types
hinge/ginglymus joint: flex + extend, sagittal plane movement only (eg. elbow)
gliding/arthrodial: flex/extend + ad/abduction. rocking movement (eg. carpus).
pivot/trochoid: ‘no’ joint, rotates (eg. only in atlantoaxial joint)
ball + socket/spheroidal: all directions (eg. shoulder, hip)
anatomical vs common joint names
humeral = shoulder
cubital = elbow
carpus
metacarpophalangeal = fetlock
proximal interphalangeal = pastern
distal interphalangeal = coffin
coxal = hip
genual = stifle
tarsus = hock
joint movement types
flexion: decrease angle (bends)
extension: increase angle (straightens)
hyperextension: bending increases beyond a straight line (equine fetlock in normal standing position)
adduction: towards body
abduction: away from body
rotation: twisting on axis (eg. rotating wrist)
circumduction: only distal end of limb moves (eg. finger circles)
joint injuries
luxation (dislocation): one+ segments of joint out of place
- usually traumatic: includes stretching/tearing of ligaments
- can also have conformational/developmental component
subluxation: partial dislocation
- usually traumatic
sprain = ligaments stretched but joint not discolated
strain = tendon/muscle damage from stretching
cuts/punctures: loss of synovial fluid and high risk of infection
infections: traumatic or blood borne
- cause inflammation (arthritis)
arthritis:
- acute: from trauma/infection
usually involves 1 joint (eg. popped knees, traumatic carpitis)
- chronic: usually degenerative osteoarthritis. most common type. usually in older animals from chronic repeated stress (eg. hip dysplasia)
- common causes: trauma, immune mediated, infectious -> always causes severe lameness
joint disease
intervertebral disc disease: degeneration of 1+ discs, causes bulging of fibrous covering OR complete rupture of contents
- presses against spinal cord dorsal to disc
- usually occurs in thoracolumbar areas
- common in chondrodysplastic dogs (daschunds)
- cause pain, paralysis, numbness
- surgery or cage rest
osteochondrosis dissecans (OCD): problem with formation of bone under articular cartilage
- cartilage abnormally thickened, can separate
- makes partially attached ‘saucer-shaped’ flap which doesn’t reattach and heal because joint moves
- flap often torn loose -> floats in joint capsule
- flap can grow thanks to synovial fluid nourishing it
- usually shoulder (can be in elbow, stifle, hock)
- usually giant breeds (presents as puppies) and horses
- cause unknown, hereditary
- surgery or rest
humeroradioulnar dysplasia
- OCD one type
- ununited anconeal process another type:
- ossification failure of center of anconeal process - doesn’t fuse with ulna
- hereditary in large breed dogs
- unstable joint -> osteoarthritis can develop
- surgical removal of fragments
aseptic necrosis (legg-calve-perthe disease)
- spontaneous necrosis of femoral head
- unknown cause, very painful
- young small breed dogs
- surgery
hip dysplasia:
- multifactorial: combo of hereditary, injury as puppy, obesity, too-rapid growth
- acetabulum shallow, femoral head moves too much
- causes osteophyte (flattened femoral head) and osteoarthritis
- prevention: selective breeding, don’t over-feed large puppies, no slippery floors and excessive stairs for puppies
- NSAIDs, femoral head osteotomy, or hip replacement
patellar luxation:
- causes: hereditary in toy breeds, shallow femoral trochlea, medial luxation (cranial cruciate may rupture, some develop secondary arthritis)
- surgery or rest
rupture of cruciate ligaments of stifle:
- usually involves cranial cruciate in dogs
- often comes with rupture of medial collateral ligament
- joint instability can be demonstrated by ‘drawer sign’ = ability to slide tibia cranial to femur
fractures
simple: skin intact
compound: external wound (either bone protrudes or external wound intrudes)
comminuted: 2+ pieces.
incomplete/greenstick: bends and tears partially (young animals)
fracture healing
fix/immobilize
- fracture hematoma forms -> osteoblasts invade area and form callus -> calcium deposited, mineralizes callus -> initial healing complete -> months-years of remodeling to restore
