Lessons 8 & 9 Osseous Tissue Flashcards
what is the difference between ligaments and tendons?
ligaments: attach bones together at joints
tendons: attach muscle to bone
what are some roles of the skeleton?
- support
- protection
- movement
- electrolyte and acid-base balance
- blood formation
- hormone secretion
what is the structure of a flat bone and an example?
thin curved plates, two external layers of compact bone and internal layer of spongy bone. an example is the skull, ribs, scapula…
where are short bones found?
in the wrist and ankle
where are irregular bones found?
in the vertebrae and in some skull bones
give some examples of long bones.
humerus, radius, ulna, femur, metacarpals, metatarsals, phalanges
where is spongy bone typically found?
in the center of ends and shafts of long bones, and in the middle of nearly all others. covered by compact bone!!
where is compact bone typically found in the long bone?
the outer shell of a long bone, encloses the marrow (medullary) cavity
what is the epiphyseal line? how does that differ from an epiphyseal plate?
line is a remnant of childhood growth zone. the plate is found in growing bones (composed of cartilage) and is the site of growth. line replaces plate.
what do osteogenic/osteoprogenitor cells do?
they are mesenchymal stem cells that give rise to osteoblasts (found in the endosteum and inner layer of the periosteum)
what do osteoblasts do?
produce bone matrix, performs osteogenesis promoting mineralization and calcification
under stress, mitotic division of osteoblasts is stimulated to produce more bone matrix
what are osteocytes? what do they do?
when osteoblasts get trapped in bone matrix (in lacunae) it becomes osteocytes.
maintains bone matrix and can sometimes reabsorb or deposit bone matrix. act as strain sensors (signals to strengthen the bone
what is osteocalcin?
hormone secreted by osteoblasts and osteocytes, body’s stress response by stimulating secretion of insulin and increasing insulin sensitivity
what do osteoclasts do?
performs osteolysis/resorption (breakdown of bone as part of bone remodeling)
**do not develop from osteogenic cells. produced by other types of cells (stem cells in bone marrow that give rise to macrophages)
what is the composition of osseous tissue matrix?
1/3 organic matter (synthesized by osteoblasts)
2/3 inorganic matter (provides support and strength)
you NEED both
what is vitamin D3’s function for bone health?
it absorbs calcium from your diet
what is rickets disease caused by?
mineral deficiency, specifically calcium from your diet, and can be from not enough UV light exposure (vitamin D3)
soft deformed bones
what is the difference between concentric lamellae, circumferential lamellae, and interstitial lamellae?
concentric: layers around a central (haversian) canal
circumferential: encircles the inner outer region of dense bone
interstitial: fill irregular regions between osteons
how does the spongy bone structure relate to mechanical stress?
spongy bone has greater surface area than compact bone meaning they are the first to be exposed to osteoclast breakdown
what is red bone marrow also known as?
myeloid tissue
produces RBCs!
how does homeostasis occur in bones (think in relation to osteoblasts and osteocytes)
- if there is more bone breakdown than building, bone becomes weaker
- if there is more bone building than breakdown, bone becomes stronger
what is ossification or osteogenesis?
the formation of bone
explain intramembranous ossification
- occurs in the dermis
- produces the flat bones of the skull
- osteoid tissue is deposited into embryonic mesenchyme
- osteoid tissue calcifies and traps osteoblasts -> osteocytes
- spongy bone forms with periosteum outside
- osteoblasts under periosteum fill between trabeculae, compact bone forms with spongy bone under
explain endochondral ossification
- develops from hyaline cartilage model
- produces most of bones in body
- mesenchyme forms hyaline cartilage model
- primary ossification center (center of long bone), periosteum, and bony collar underneath periosteum forms
- primary ossification center becomes vascular forming primary marrow cavity. osteoblasts enter and lines cavity, forms secondary ossification center
- long bone has enlarged primary marrow cavity at diaphysis, secondary marrow cavity in one epiphysis, and a second ossification center in the other epiphysis
- epiphyses fill with spongy bone and epiphyseal plate (cartilage) separating primary and secondary marrow cavities
- final adult bone will only have 1 marrow cavity, epiphyseal plate closes (becomes epiphyseal line)
what is the metaphysis?
the sides of the epiphyseal plate where cartilage is replaced by bone
what is the zone of reserve cartilage?
composed of resting chondrocytes
what do chondrocytes do?
they produce the cartilage matrix
what is the zone of cell proliferation?
multiplying chondrocytes forming lacunae
what is the zone of cell hypertrophy?
chondrocytes enlarge - no mitosis
what is the zone of calcification?
temporary mineral deposition between lacunae
what is the zone of bone deposition?
chondrocytes die, osteoblasts enter and deposit matrix to form concentric lamellae
what are the zones of the metaphysis? (superficial to deep)
- zone of reserve cartilage
- zone of cell proliferation
- zone of cell hypertrophy
- zone of calcification
- zone of bone deposition
how do you grow in height? think about the metaphysis zones
chondrocytes multiply in zone 2 (cell proliferation) and enlarges in zone 3 (hypertrophy), pushing zone 1 (reserve cartilage) towards the end of the bone, elongating it
what is the term for cartilage growth from inside?
interstitial growth
what is achondroplastic dwarfism?
the long bones stop growing in childhood, results in a normal torso with shortened limbs
caused by genetics (mutation)
what is pituitary dwarfism?
normal proportions with a short stature (think
caused by a lack of GH in the pituitary gland
what is appositional growth and how does it occur?
growth in diameter and thickness of bone, deposition of new tissue at the bone surface
intramembranous ossification
- as bone increases in diameter, marrow cavity widens as osteoclasts enlarge it by dissolving the inner surface bone tissue
what is wolff’s law of bone?
bone structure is determined by the stress put on it
bones grow larger in response to mechanical stress
how does mineralization occur? (mineral deposition)
calcium, phosphate, and other ions are taken from the blood and deposited into bone. osteoblasts produce collagen fibers around osteon that become encrusted with minerals, which attracts more calcium and phosphate
what is ectopic ossification?
when tissues become calcified when they shouldn’t be (produces heterotopic bones) ex. eye, brain, musces, tendons, arteries
what is a calculus?
a calcified mass in a soft organ
what are the 3 main types of heterotopic bones?
- myositis ossificans: rare genetic form causes muscles to ossify
- traumatic myositis: repeated trauma to soft tissue triggers ossification
- neurogenic heterotopic ossifications: frequent complication to spinal cord injury
what is fibrodysplasia ossificans progressiva (FOP)?
when the muscle and connective tissue ossifies. surgical removal can trigger more ossification, gene therapy is possible for treatment
what is mineral resorption?
process of dissolving bone, releasing minerals into the blood
performed by osteoclasts
what is hypocalcemia and what does it cause?
calcium deficiency, causes excessive excitability of the nervous system and muscles
what is hypercalcemia and what does it cause?
calcium excess, causes nerve and muscle cells to be less excitable than normal
what 3 hormones regulate calcium homeostasis?
- calcitriol
- calcitonin
- parathyroid hormone
what is calcitriol?
a form of vitamin D that INCREASES blood calcium levels by increasing calcium absorption in the body
what is calcitonin?
produced by cells of the thyroid gland, secreted when blood calcium is too high. LOWERS calcium levels
how? osteoclast inhibition and osteoblast stimulation
what is parathyroid hormone (PTH)?
secreted by parathyroid glands to INCREASE blood calcium levels
binds to osteoblasts and stimulates osteoclasts
which vitamins & hormones stimulate osteoblast activity?
vitamin A, vitamin C, estrogens, androgens, growth hormone, and thryoxine
