Chapter 6: Bones and Bone Tissue Flashcards
what are the main organs of the skeletal system?
bones
functions of the skeletal system
protection, mineral storage, maintenance of acid-base homeostasis, blood cell formation, fat storage, movement, and support
the 5 different shapes of bones …
long, short, flat, irregular, and sesamoid bones
the layer that covers bones is…
the periosteum
the periosteum sits on top of…
hard, outer compact bone
compact bone
hard, dense bone tissue located on the exterior of a bone; composed of osteons
long bones
- longer than they are wide
- include most arm & leg bones (ex:humerus), as well as bones of hand, feet, fingers, and toes
short bones
- about as long as they are wide, roughly CUBE SHAPED
- includes carpals (wrist bones) / tarsals (ankle bones)
flat bones
- thin and broad
- include most skull bones, ribs, sternum, and pelvis bones
irregular bones
- irregular shape
- include the vertebrae and certain skull bones
sesamoid bones
- “sesame-shaped”
- small, relatively flat, and oval-shaped bones located within tendons
-includes the patella (kneecap)
spongy bone
bone tissue located inside the bone; composed of small trabeculae
honey-comb like sponge
diaphysis
shaft of long bone
epiphyses
the ends of the long bone (2 ends)
red bone marrow
contains blood stem cell (hematopoietic cells), which are responsible for generating blood cells (red blood cells, white blood cells, or platelets)
hematopoietic tissue
Tissue in which new blood cells are formed
yellow bone marrow
houses blood vessels and adipocytes (fat cells)
contains stem cells that can become cartilage, fat, or bone cells.
bone inorganic matrix composition:
composed primarily of calcium and phosphorus salts existing as hydroxyapatite crystals
hydroxyapatite crystals
a mineral that makes bone one of the HARDEST SUBSTANCES in the body
gives bone STRENGTH and ability to RESIST compression, which allows it to perform functions of support and protection
bone organic matrix composition:
also called osteoid (unmineralized, organic portion of bone matrix that forms prior to maturation of bone tissue)
mainly consists of COLLAGEN fibers and other ECM components
osteoid
the organic component of the ECM of osseous tissue
consists of collagen fibers, proteoglycans, glycoproteins, and bone-specific proteins
the 3 main types of cells found in bone are…
osteoblasts, osteocytes, osteoclasts
osteoblasts
responsible for bone deposition (make more bone)
osteocytes
are mature osteoblasts that have become surrounded by the ECM they have secreted
osteoclasts
responsible for bone resorption (break bone down)
composition of compact bone:
composed primarily of subunits called osteons that consist of rings of bone ECM called lamellae
osteons
the functional unit of compact bone
made up of rings of bone matrix called lamellae that surround a central canal
the 2 types of bone formation processes are…
ossification & osteogenesis
primary bone
first bone formed by both types of ossification is immature bone called primary bone or woven bone
consists of irregularly arranged collagen bundles, abundant osteocytes, and little inorganic matrix
secondary bone
the primary bone is resorbed by osteoclasts and replaced by mature secondary bone, also called lamellar bone
has fully formed lamellae with regularly arranged collagen bundles, parallel to one another, which makes it stronger than primary bone
majority of bones are completely ossified by age….
7
bone inorganic matrix
composed of inorganic bone salts, mainly hydroxyapatite
bone organic matrix
includes the collagen and ground substance
ground substance contains glycoproteins, proteoglycans, and glycosaminoglycans
intramembranous ossification
the process by which certain flat bones develop directly from sheets of mesenchymal connective tissue
involves the replacement of sheet-like connective tissue membranes with bony tissue
Ex: embryonic flat bone formation of skull, maxilla, mandible, clavicle, etc
primary ossification center
generally in the diaphysis of a long bone
secondary ossification center
generally in the epiphyses
describe spongy bone formation
Osteoblasts penetrate the disintegrating cartilage and replace it with spongy bone,
this forms a primary ossification center, after which the periosteum transforms, and finally compact bone forms
endochondral ossification
the replacement of hyaline cartilage with bony tissue
hyaline cartilage serves as a scaffold for the developing bone
longitudinal growth
process by which bones grow in length
where does longitudinal growth occur?
occurs at the epiphyseal plate in long bones, which consists of five zones of cells
5 zones of cells (from closest to epiphysis to closest to diaphysis)
zone of; reserve cartilage, proliferation, hypertrophy and maturation, calcification, ossification
zone of reserve cartilage
contains cells that are not directly involved in bone growth but that can be called upon to divide if needed
“reserved cells”
zone of proliferation
it has actively dividing chondrocytes in lacunae
Chrondrocytes are stacked in rows and creates a cartilage matrix
zone of hypertrophy and maturation
contains mature chondrocytes (older and larger)
In this zone, lipids, and glycogen accumulates, causing the cartilaginous matrix to calcify
zone of calcification
contains dead chondrocytes, some of which are calcified
zone of ossification
calcified chondrocytes and osteoblasts that build bone
chondrocytes
cells producing and maintaining the cartilage matrix.
vital in sustaining homeostasis in the joints, provides cushioning in joint movements
what happens when epiphyseal plate fully ossifies?
no further longitudinal bone growth is possible
epiphyseal plate “seals” closed and becomes epiphyseal line
apposition growth
- Bones grow in width
- process in which osteoblasts in the periosteum secrete new circumferential lamellae
what 3 hormones exert significant effect on bone growth?
growth hormone, testosterone, and estrogen
bone remodeling
a combination of the continual processes of bone deposition, carried out by osteoblasts, and bone resorption, carried out by osteoclasts
variables that influence bone remodeling (bone deposition/resorption)
- BONE TENSION/PRESSURE - tension triggers osteoblasts , pressure triggers osteoclasts
- HORMONES - vitamin D, testosterone, and estrogen generally lead to net bone deposition
- DIETARY FACTORS - adequate intake of calcium ions, vitamin D, vitamin C, vitamin K, and protein all influence bone remodeling
- PARATHYROID HORMONE - stimulates osteoclasts, calcium ion absorption in the intestines, and calcium ion retention by the kidneys. These effects increase the calcium concentration in the blood
fractures
a partial or complete break in the bone
the 2 types of fractures are…
simple (closed) and compound (open) fractures
simple fracture
just a crack in the bone, bone is still in place
compound (open) fracture
the bone is broken and some parts are kind of sticking out, not just a crack
describe how bone fractures heal
first, chondroblasts secrete cartilage, forming the soft callus…
Osteoblasts later replace the soft callus with a bone callus made of primary bone
soft callus
mixture of hyaline cartilage and collagenous connective tissue
first type of soft bone created post fracture, replaces the blood clot at the fracture site
Holds fractured bone together, but it’s not strong enough to be used in the way that bone would be used
bone callus
hard callus is actually bone, but it’s still softer than regular bone.
