Skeletal System Flashcards
list the 5 functions of the skeletal system
- protection
- support
- locomotion
- mineral storage (Ca and P)
- blood cell formation (in bone marrow)
what are the two subsections of the skeleton?
- axial skeleton
2. appendicular skeleton
what does the axial skeleton contain?
all bones along or attached to the median plane, including the skull, vertebrae, ribs, and sternum
what does the appendicular skeleton contain?
bones of the limbs
how many cervical vertebrae do all mammals have?
7
how many cervical vertebrae do birds have? are they all separate?
14, but they’re all fused together
why do birds have a larger sternum?
to support breast muscles
list and describe the 5 bone shapes
- long bones: longer than they are wide, found in limbs
- short bones: more cube-shaped, found in carpus and tarsus
- flat bones: flatter than other bones, found in skull, sternum, ribs, scapula
- irregular bones: don’t fit with other classifications, usually unpaired, ex. vertebrae
- sesamoid bones: resemble sesame seeds, found in the patella and digits
describe pneumatic bones
contain air spaces called sinuses, lighter than others, avian skeleton has more than mammalian because flight
list and describe the 5 types of vertebrae
- cervical: most cranial, all mammals have 7
- thoracic: attached to/joined with ribs
- lumbar: lower back
- sacral: joined with pelvis, fused together
- caudal: most caudal, make up the tail
list the 8 basic vertebrae structures
- vertebral body
- spinous process
- pair of transverse processes
- pair of lamina
- pedicle
- pair of articular processes
- vertebral foramen
- transverse foramen
describe the location of the vertebral body
on the ventral side of the vertebrae, contains intervertebral disk
describe the spinous process
projects dorsally off vertebrae
where do the transverse processes project?
laterally off the vertebrae
what do the paired lamina do?
connect spinous process to transverse processes
what does the pedicle connect?
transverse processes to the vertebral body
describe the location of the paired articular processes
sit on the pedicle, where one vertebrae joins with the next
describe what the vertebral foremen contains
site of the spinal cord
describe the transverse foramen
holes in pedicle of cervical vertebrae, where blood vessels and nerves run through neck
where are transverse foramen found?
ONLY in cervical vertebrae!!
list the 3 types if bone cells
- osteoblasts
- osteoclasts
- osteocytes
give the function of osteoblasts
ossification, secrete hydroxyapatite, the mineral component of bone that makes bone hard
what is ossification?
formation of bone by osteoblasts
where are osteoblasts found?
found on the outside/lining bone surfaces so they can secrete bone on top of existing bone
describe osteocytes
mature bone cells, form when osteoblasts are surrounded by bone and become osteocyctes
describe the function of osteoclasts
resorption (breakdown of bone)
give the 6 structures specific to long bones
1, epiphysis
- diaphysis
- metaphysis
- epiphyseal plate
- epiphyseal line
- medullary cavity
describe the epiphysis
either end of a long bone (proximal epiphysis on top, distal epiphysis on bottom)
describe the diaphysis
the long shaft of a long bone
describe the metaphysis
connects epiphysis to diaphysis (proximal and distal end)
describe the epiphyseal plate and give the location
found in the meatphysis, is a layer of hyaline cartilage where growth of long bone occurs
describe the epiphyseal line
replaces epiphyseal plate when growth ceases, made up of compact bone
describe the medullary cavity
in center of diaphysis, does not contain bone, but bone marrow, and is hollow
describe red bone marrow
found in young animals, blood cell formation site
describe yellow bone marrow
found in adults, made of adipose (fat) tissue
list 3 structures found in all bones
- articular cartilage
- periosteum
- endosteum
describe articular cartilage
thin layer of hyaline cartilage that covers surfaces of a bone within a joint
describe the periosteum
covers the rest of the bone, 2 layers
list and describe the 2 layers of the periosteum
- superficial/outermost layer: dense irregular connective tissue, provides protection
- deep/inner layer: single layer of osteoblasts
describe the endosteum
lines internal surfaces of bone, thin layer of osteoblasts AND osteoclasts
list the 2 classifications when bone is classified by amount of extracellular matrix to amount of space
- spongy (cancellous) bone
2. compact bone
describe spongy bone
more space is found around matrix, made up of trabeculae, spaces between trabeculae contain red bone marrow and blood vessels, even as animal ages
what are trabeculae?
interconnecting rods of bone
describe compact bone
less space is found around matrix, more dense, found on the outside and is tougher, arranged in osteons
what are osteons?
the basic unit of compact bone, also called Haversian systems
list the 5 structures in osteons
- central canals
- lamellae
- lacunae
- canaliculi
- perforating canals
describe the central canals of osteons
contains blood vessels and nerves
describe the lamellae of osteons
circular plates of bone that surround the central canal
describe the lacunae of osteons
structures within the lamellae that house osteocytes
describe the canaliculi of osteons
tiny canals that connect lacunae
describe the perforating canals of osteons
connect central canals
what is calcification?
the deposition of calcium salts in any tissue other than bone
what is a functional result of calcification?
the os penis
what are centers of ossification?
location where ossification begins after calcification
what is intramembranous ossification?
occurs in a primitive connective tissue membrane (embryonic growth), how most flat bones are formed
what is endochondral ossification?
occurs in a hyaline cartilage model, which is already in the shape of the bone and gets replaced through the process; formation of limbs, as the connective tissue is now specialized and happens during fetal development
list the 5 zones in growth in length of a long bone in order
- resting zone
- zone of proliferation
- zone of hypertrophy
- zone of calcification
- zone of ossification
where is the resting zone located and what happens there?
at the epiphyseal plate, closest to the epiphysis; chondrocytes are at rest here
what happens in the zone of proliferation (2nd zone in long bone length growth)?
chondrocytes begin to divide rapidly, dividing chondrocytes form columns
what happens in the zone of hypertrophy (3rd zone in long bone length growth)?
chondrocytes enlarge
what happens in the zone of calacification (4th zone in long bone length growth)?
chondrocytes absorb bone matrix and die; blood vessels from diaphysis enter lacunae leftover from dead chondrocytes; osteoblasts differentiate from blood vessels
what happens in the zone of ossification (5th zone in long bone length growth)?
osteoblasts secrete bone; epiphysis has been pushed away from diaphysis to add length; happens on both ends of long bones
what 3 things affect the rate of bone growth?
- nutrition
- growth hormone
- sex hormones
how does nutrition affect bone growth?
malnutrition inhibits growth as cells don’t get enough nutrients to divide and grow
how does a calcium, phosphorus, or vitamin D deficiency affect bone growth?
osteoblasts can’t form hydroxyapatite, meaning they can’t form bone
what does a vitamin C deficiency impair?
Collagen synthesis
how does growth hormone affect rate of growth?
acts on liver to cause secretion of insulin-like growth factor (IGF)
what does IGF (insulin-like growth factor) do for rate of growth?
acts on chondrocytes to cause proliferation
how do sex hormone affect rate of growth? (2 ways)
testosterone and estrogen stimulate the secretion of growth hormone, resulting in a growth spurt during puberty, and they also stimulate the closure of the epiphyseal plate to cease growth
list the 7 steps of intramembranous ossification
- cells within a connective tissue membrane differentiate into osteoblasts
- osteoblasts begin to secrete bone and calcify surrounding tissue
- a center of ossification forms
- osteoblasts secrete bone around collagen fibers in connective tissue membrane, forming tiny trabeculae
- osteoblasts line the tiny trabeculae and secrete bone to thicken the trabeculae, forming true trabeculae
- spaces between trabeculae develop into red bone marrow
- periosteum forms and osteoblasts in the periosteum secrete compact bone around trabeculae
where does endochondral ossification take place?
in a hyaline cartilage model
list the 10 steps of endochondral ossification
- hyaline cartilage model forms
- cells on outside of model differentiate into osteoblasts and secrete bone along outside of cartilage model
- cells inside the model absorb bone matrix, become calcified, and die
- blood vessels enter cartilage model through lacunae left behind by dead cells
- osteoblasts will differentiate inside cartilage, start to secrete bone, and form a primary center of ossification
- osteoblasts continue to replace cartilage with bone
- osteoclasts form and break down bone to form medullary cavity
- red bone marrow develops in medullary cavity
- cartilage in epiphysis of model begins to absorb bone and secondary centers of ossification form
- osteoblasts continue to secrete bone until all cartilage has been replaced with bone
what 2 hormones regulate blood calcium homeostasis?
calcitonin and parathyroid hormone (PTH)
what causes the thyroid to secrete calcitonin?
high blood calcium levels
what does calcitonin do and how?
lowers blood calcium levels by targeting osteoclasts to reduce activity/resorption
what causes the parathyroid to release PTH?
low blood calcium levels
what does PTH do and how?
raises blood calcium levels by targeting osteoclasts to increase activity/resorption
what is hyperparathyroidism?
oversecretion of PTH, causes increased bone resorption leading to weakened bones
what is hypoparathyroidism?
undersecretion of PTH, leads to muscle cramping and twitching (tetany), major muscle contraction issues
list the 3 aspects of bone mechanics
- bone is not elastic
- bone is subjected to stresses
- bone is dynamic
what is the major reason for breaks and permanent bone stretching (of bone dynamics)?
bone is not elastic
list and describe the 4 types of stresses that bones are subjected to?
- compression: press together
- shearing: rub together
- bending: pressure
- torsion: pivoting
what is the implication of the fact that bone is dynamic?
it can repair and rebuild, the reason for normal bone healing
describe a simple fracture
skin over fracture is intact
describe an open fracture
skin over fracture is damaged and exposing fractured bone
describe a displaced fracture
broken ends of bone are out of alignment
describe a nondisplaced fracture
broken ends of bone remain in alignment
describe a complete fracture
bone is broken across entire length/width
describe an incomplete fracture
bone is not broken across entire length/width
describe a transverse fracture
bone broken perpendicular to axis
describe an oblique fracture
bone not broke perpendicular to axis
describe a spiral fracture
bone has twisted apart due to torsion stresses
describe a comminuted fracture
bone has splintered or been crushed into small fragments
communes have many parts
describe a segmental fracture
fracture in more than one part of the bone (segments)
describe an avulsed fracture
fragment is separated from rest of bone, common at ends of long bones
describe an impacted fracture
bone fragments are driven together due to compression stresses
describe a torus/buckle fracture
break in spongy bone causes bulging from inflammation
describe a greenstick fracture
bone is broke on one side and other side is only bent
what do torus and greenstick fractures have in common?
they are incomplete fractures, commonly found in young animals
list the 4 phases of normal bone healing
- hematoma formation
- callus formation
- callus ossification
- bone remodeling
describe the hematoma formation step of normal bone healing
hematoma forms due to broken blood vessels, and blood accumulates around broke ends of bone, blood clots around bone
describe the callus formation step of normal bone healing
chondroblasts secrete cartilage (inner callus) and osteoblasts secrete bone (outer callus) around outside of break and between broken ends of bone, the cartilage/bone mixture forms a callus to hold broken ends of bone in place
does the callus form if a bone isn’t in alignment? what does this mean?
yes, it forms whether the bone is in alignment or not, which is why we have to reset bones sometimes
describe the callus ossification step of normal bone healing
callus gets replaced with bone, similar to endochondral ossification
describe the bone remodeling step of normal bone healing
osteoblasts and osteoclasts secrete and breakdown bone to return it to its normal shape
how long does bone remodeling take and what factors affect it?
can take up to a year, and bone will still be slightly larger at break site, depends on blood supply, age, and damage to surrounding tissue
what is osteodistrophy?
any abnormality in bone development
give an example of osteodistrophy?
rickets (young animals)/osteomalacia (adults)
describe rickets/osteomalacia
inadequate mineralization of bone leads to softer bones, causing bow leggedness
what two things causes rickets/osteomalacia and which one is preventable?
hyperparathyroidism (nonpreventable) or a deficiency in vitamin D, P, or Ca (preventable)
what is osteoporosis?
porous bone, or loss of bone mass itself, causes brittle bones
what causes achondroplasia?
fusion of epiphyseal plates early in development means bone doesn’t continue to grow in height, only in width, leading to short stubby legs
what animals are bred for achondroplasia?
dachsunds, mini cattle, mini cats
