skeletal system Flashcards
what are the 4 components of the skeletal system
- bones
- cartilage
- ligaments
- other connective tissues
what are the 2 types of bones
- compact
- spongy
what is compact bone also known as
- dense or cortical bone
what type of bone makes up approximately 80% of total bone mass
compact bone
what type of bone makes up approximately 20% of total bone mass
spongy bone
where is spongy bone located
internal to compact bone
what is cartilage
semirigid connective tissue that is more flexible than bone
where can hyaline cartilage be located (4)
- costal cartilage (attaches ribs to sternum)
- articular cartilage (covers ends of some bones)
- epiphyseal plates (within growth plates)
- model during development for fetal skeleton formation
where can fibrocartilage be located (3)
- intervertebral discs
- pubic symphysis (cartilage between nomes of the pelvis)
- menisci (cartilage pads of knee joints)
what are ligaments
dense regular tissue connecting bone to bone
what are tendons
dense regular tissue connecting muscle to bone
what are the functions of bones (4)
- support and protection
- levers for movement
- hemopoiesis
- storage of mineral and energy reserves
how do bones provide structural support internally
they protect delicate tissue and organs from injury and trauma
how do bones act as levers for movement (2)
- they act as attachment sites for skeletal muscles, soft tissues and some organs
- attached muscles contract and exert a pull, altering the direction and magnitude of forces by skeletal muscles
where does hemopoiesis occur
in red bone marrow connective tissue
what minerals do bone store
calcium and phosphate
what does calcium do (body functions) (3)
- muscle contraction
- blood clotting
- release of neurotransmitter from nerve cells
what is the significance of phosphate in the body
important component of plasma membrane
what does the body do when it needs calcium or phosphate
some bone connective tissue is broken down
what are the 4 classes of bone
- long
- short
- flat
- irregular
what is elongated in long bones
cylindrical shaft (diaphysis)
describe long bones
greater in length than width
what is a specific type of seed-shaped short bones
sesamoid bones
describe short bones
length nearly equal to their width
what do flat bones provide
extensive surface areas for muscle attachment and protect underlying soft tissue
describe flat bones
flat, thin surfaces that may be slightly curved
describe irregular bones
complex shapes
what is the largest sesamoid bone
patella (kneecap)
what is the most common bone shape
long bone
what is the purpose of the diaphysis
provides for leverage and major weight support
what is the hollow, cylindrical space within the diaphysis called (long)
medullary cavity
what happens to the contents of the medullary cavity as a person ages (long)
in children, the cavity contains red bone marrow, it’s replaced by yellow bone marrow in adults
what is the expanded, knobby end of the bone called (long)
epiphysis
what are the 2 types of epiphyses
- proximal epiphysis
- distal epiphysis
what does the spongy bone in the epiphysis do
resists stress that is applied from many directions
what covers the joint surface
thin layer of hyaline cartilage called articular cartilage
what does the articular cartilage do
helps reduce friction and absorb shock in moveable joints
what is the region between the diaphysis and the epiphysis (long)
metaphysis
what is the epiphyseal plate made of (long)
a thin layer of hyaline cartilage
what is the function of the epiphyseal plate (long)
provides for the continued lengthwise growth of the bone
what is the remnant of the epiphyseal plate in adults (long)
epiphyseal line
what surfaces does the periosteum cover
the outer surface of the bone except articular cartilage
what are the 2 layers of the periosteum
- outer fibrous layer of dense regular tissue
- inner cellular layer
what does the outer fibrous layer of the periosteum do (3)
- protects the bone from surrounding structures
- anchors blood vessels and nerves to the surface of the bone
- serves as an attachment site for ligaments and tendons
what does the inner cellular layer of the periosteum include (3)
- osteoprogenitor cells
- osteoblasts
- osteoclasts
what anchors the periosteum to the bone
perforating fibers, collagen fibers, which run perpendicular to the diaphysis (long)
what types of bone do not have a medullary cavity (3)
- short
- flat
- irregular
what is the external surfaces of the bone composed of (short, flat and irregular)
compact bone
what is the internal surfaces of the bone composed of (short, flat and irregular)
entirely of spongy bone
what is the spongy bone in the flat bone of the skull called
diploë
are bones avascular
nope, they’re highly vascularized
what is the small opening in the bone called which contains the nutrients artery and vein
nutrient foramen
how many arteries enters the bone
1
how many veins enters the bone
1
what are the nerves in the bone mainly
sensory nerves which signal injuries to the skeleton
what is bone marrow
soft connective tissue
what are the 2 types of bone marrow
- yellow
- red
what is red bone marrow also known as
myeloid tissue
what does red bone marrow contain (3)
- reticular connective tissue
- developing blood cells
- adipocytes
where is red bone marrow located in children (2)
- spongy bone of most bones
- the medullary cavity of long bones
where does a change in bone marrow occur in adults (2)
- medullary cavities of long bones
- inner core of most epiphyses
how does the change in bone marrow occur (2)
- progressive decrease in developing blood cells
- increase in adipocytes
where do adults have red bone marrow (6)
- flat bones of the skull
- vertebrae
- ribs
- sternum
- ossa coxae (hip bones)
- proximal epiphyses of each humerus and femur
what happens to the erythrocyte numbers in a person with severe anemia
- insufficient oxygen reaching the cell triggers the conversion of yellow bone marrow into red bone marrow
- this facilitates the production of additional erythrocytes
what is the primary component of bone
bone connective tissue (osseus tissue)
what are the 2 components of bone
cells and extracellular matrix
what are the 4 types of cells in bone connective tissue
- osteoprogenitor cells
- osteoblasts
- osteocytes
- osteoclasts
what are osteoprogenitor cells
stem cells derived from mesenchyme
what happens when osteoprogenitor cells divide
they produce another stem cell along with a ‘committed cell’
what does the ‘committed cell’ matures to become
osteoblast
where are the stem cell products of osteoprogenitor cell division found
periosteum and endosteum
how are osteoblasts positioned on bone surfaces
side by side
what is the shape of active osteoblasts
cuboidal
what organelles are in abundance in osteoblasts (2)
- rough er
- golgi body
what is the function of osteoblasts
synthesizing and secreting osteoid
what is osteoid
the initial semisolid organic form of bone matrix
what does osteoid do as a result of salt crystal depositon
calcifies
what is the consequence of mineral deposition on osteoid
osteoblasts become entrapped within the matrix they produce, then they differentiate into osteocytes
what are osteocytes
mature bone cells derived from osteoblasts that have lost their bone-forming ability
what is maintained as osteoblasts become osteocytes
connections between osteocytes and original neighbouring osteoblasts
what are the 2 functions of osteocytes
- maintain the bone matrix
- detect mechanical stress on a bone
what may be the result of the detection of mechanical stress on a bone (osteocytes)
deposition of new bone matrix at the surface
how do osteoclasts appear
large, multinuclear, phagocytic
where are osteoclasts derived from
fused bone marrow cells similar to those that produce monocytes
what is the purpose of the ruffled border of osteoclasts
to increase their surface area exposure to the bone
where is an osteoclast located
in resorption lacuna
what is a resorption lacuna
depression or pit on the bone surface
what is the organic component of bone connective tissue
osteoid
what is osteoid composed of
- collagen
- semisolid ground substance of proteoglycans
- glycoproteins
what is the inorganic components of the bone matrix
salt crystals (primarily calcium phosphate)
what do the organic components of bone matrix give to the bone
- tensile strength
- overall flexibility
through resisting stretching and twisting
how are hydroxyapatite crystals formed
calcium phosphate and calcium hydroxide interaction
what do hydroxyapatite crystals do during calcification
incorporate other salts and ions such as sodium, magnesium, sulfate and fluoride
where do hydroxyapatite crystals deposit
around the long axis of collagen fibers in the extracellular matrix
what do hydroxyapatite crystals do to the bone’s matrix
- harden the bone matrix
- accounts for the rigidity/ relative inflexibility of bone that provides its compressional strength
what results in brittle bones
loss of protein/presence of abnormal protein
what results in soft bones
insufficient calcium
when does bone formation begin
when osteoblasts secrete osteoid
what is another name of calcification
mineralization
when is calcification initiated
when the concentration of calcium ions and phosphate ions reaches critical levels and precipitate out of solution, forming hydroxyapatite crystals
what does bone formation require (4)
- vitamin D
- vitamin C
- calcium
- phosphate
what happens when bones do not have hydroxyapatite crystals
the bone bends
what happens when bones do not have collagen
the bone breaks
describe bone resorption
bone matrix is destroyed by substances released from osteoclasts into the extracellular space adjacent to the bone
where are proteolytic enzymes released from
lysosomes within the osteoclasts
what is the role of the lysosomes in bone resorption
- it releases proteolytic enzymes
- the enzymes chemically digest the organic components (collagen fibers and proteoglycans)
what is the role of hydrochloric acid in bone resorption
it dissolves the mineral parts (calcium and phosphate) of the bone matrix
what are osteons (2)
- small, cylindrical figure
- basic functional and structural unit of mature compact bone
how are osteons oriented
parallel to the diaphysis of long bones
what are the 5 components of an osteon
- the central (haversian) canal
- concentric lamellae
- osteocytes
- lacunae
- canaliculi
what extends through the central canal
- blood vessels
- nerves
that supply the bone
what are concentric lamellae
rings of bone connective tissue
what does each lamella contains
collagen fibers, with adjacent collagen fibers oriented at an angle that is 90 degrees different from the next/previous lamella
what does the alternating pattern of collagen fiber direction gives to the bone
part of its strength and resilience
what are lacunae
small spaces that each house an osteocyte
what are canaliculi
tiny, interconnecting channels that extend from each lacuna, connect to other lacuna
what do canaliculi house
osteocyte cytoplasmic projections
what do osteocyte cytoplasmic projections permit
intercellular contact and communication of nutrients, minerals, gases and wastes
what are some structures of compact bone that are not a part of osteon proper (3)
- perforating canals
- circumferential lamellae
- interstitial lamellae
what do perforating canals form
a channel for a vascular and innervation connection among osteons
what are the 2 types of circumferential lamellae
- external
- internal
what are external circumferential lamellae
rings of bone immediately internal to the periosteum of the bone
what are internal circumferential lamellae
rings of bone immediately external to the endosteum
what are interstitial lamellae (2)
- the components of compact bone between osteons
- leftover parts of osteons that have been partially resorbed
what is the difference between spongy and compact bones
spongy bone contains no osteons
what is the structure of spongy bone
open lattice of narrow rods and plates of bone (trabeculae)
what fills in between the trabeculae
bone marrow
what does the meshwork of small bone pieces, trabeculae, provide
great resistance to stresses applied in many directions by distributing the stress throughout the entire framework
