Ch7 Bone Tissue Flashcards
What is osseus (bone) tissue?
connective tissue w/ matrix hardened by minerals: Ca3(PO4)2
Individual bones =
bone tissue, marrow, blood, cartilage & periosteum
Individual bones:
continually ____ itself
strong, flexible ____ of body
continually REMODELS itself
strong, flexible FRAMEWORK of body
Describe cartilage
Forerunner of most bones, present in joints
What do ligaments do?
Connect bones at joints
What are the functions of the skeleton?
- Support
- Protection
- Movement
What is electrolyte balance composed of?
Calcium & phosphate ions
What does an acid-based balance do?
Buffers blood against pH changes
What is blood formation comprised of?
Red bone marrow - produces blood cells
Describe the different types of bones
- Long bones - levers acted upon by muscles
- Short bones - glide across one another
- Flat bones - protect soft organs
- Irregular bones - elaborate shapes
What are the general features of the long bone?
- Epiphyses & diaphysis
- Compact & spongy bone
- Marrow cavity
- Articular cartilage
- Periosteum
What are the general features of the flat bone?
2 layers of compact bone enclose middle layer of spongy bone
-both surfaces of flat bone covered with periosteum
Describe diploe
spongy layer in cranium
- absorbs shock
- marrow spaces lined w/ endosteum
What are the 4 principal types of bone cells?
- osteogenic cells
- osteoblasts
- osteocytes
- osteoclasts
What are osteoclasts?
bone-dissolving cells on bone surface
- develop from same bone marrow stem cells as blood cells (diff from other bone cells)
- large cells formed from fusion of stem cells
Bone matrix is comprised of
Organic and inorganic matter
What does the combination of organic and inorganic matter do?
Provides strength + resilience
(minerals resist compression, collagen resists tension”
Describe organic matter
synthesized by osteoblasts
- collagen, carbohydrate–protein complexes, (GAG, proteoglycans, & glycoproteins)
Describe inorganic matter
- 85% hydroxyapatite: crystallized Ca3(PO4)2 salt
- 10% CaCO3
- Other minerals (fluoride, sodium, potassium, magnesium)
By dry weight, what proportions are organic and inorganic bone matrix?
1/3 organic and 2/3 inorganic
Minerals resist _____, collagen resists ______
Minerals resist COMPRESSION, collagen resists TENSION
Describe rickets
Soft bones, defiency your of calcium salts
Define osteogenesis imperfecta
Brittle bone disease, lack of collagen
Describe osteon
Basic structural unit
Osteons are made up of cylinders formed from layers (______) of matrix around _____ canal
osteocytes connected by tiny cell processes in _______
Osteons are made up of cylinders formed from layers (LAMELLAE) of matrix around CENTRAL canal
osteocytes connected by tiny cell processes in CANALICULI
What is being demonstrated in each picture?
What are perforating (Volkmann) canals?
vascular canals perpendicularly joining central canals
Describe trabeculae
Thin plates of bones - spaces filled w/ red bone marrow
What do trabeculaes do and where do they develop?
Provides strength with minimal weight and develop along bone’s line of stress
Trabeculaes have…
Few osteons, no central canals
All osteocytes are…
Close to bone marrow
Amid trabeculae of spongy bone are…
Red marrow (myeloid tissue) and yellow marrow
What is red marrow (myeloid tissue)?
- hemopoietic tissue—produces blood cells; multiple tissues
- in adults: skull, vertebrae, ribs, sternum, part of pelvic girdle, heads of humerus & femur
What is yellow bone marrow in adults?
- most red marrow in long bones becomes fatty yellow marrow
- no longer produces blood
Describe ossification (osteogenesis)
Bone formation
What 2 methods does bone develop by in human fetuses and infants?
- Intramembranous ossification
- Endochondral ossification
Intramembranous Ossification happens in…
- Flat bones of skull & clavicle
- Mesenchymal cells become osteogenic cells
Describe endochondral ossification
Bone develops from pre-existing model (perichondrium & hyaline cartilage)
How do most bones develop?
From endochondral ossification
What happens during the formation of primary ossification center and marrow cavity in shaft of model?
- bony collar developed by osteoblasts
- chondrocytes swell & die
- stem cells give rise to osteoblasts/clasts
- bone laid down, marrow cavity created
Secondary ossification centers and marrow cavities form in….
Form in ends of bones (same process as primary)
Cartilage remains as…
Articular cartilage and epiphyseal (growth) plates
What do growth plates do?
Provides for increase in length of bone during childhood and adolescence
By early 20s, _______ is gone and primary & secondary __________ united
By early 20s, GROWTH PLATE is gone and primary & secondary MARROW CAVITIES united
What are the zones of metaphysis?
- Zone of Reserve Cartilage
- Zone of Cell Proliferation
- Zone of Cell Hypertrophy
- Zone of Calcification
- Zone of Bone Deposition
Bone increases in what when?
Bone increases in length in epiphyseal plate
What is left behind when cartilage is gone?
Epiphyseal line
Bone increases in ____ = ____ growth
Osteoblasts lay down ____ on_______ surface
osteoclasts _____ bone on ____ surface
parallel to surface, circumferential ________
Bone increases in WIDTH = APPOSITIONAL growth
Osteoblasts lay down MATRIX LAYERS on OUTER surface
osteoclasts DISSOLVE bone on INNER surface
parallel to surface, circumferential LAMELLAE
What percentage of bones is remodeled throughout life each year?
10% each year
Describe Wolf’s law of bone
architecture of bone determined by mechanical stresses
action of osteoblasts and osteoclasts
There is a greater density and mass of bone in…
Athletes or manual workers
Describe achondroplastic dwarfism
- long bones stop growing in childhood
- normal torso, short limbs
A failure of what in where is what causes achondroplastic dwarfism?
A failure of cartilage growth in metaphysis
What type of mutation and allele causes achondroplastic dwarfism?
Spontaneous mutation and dominant allele
Describe pituitary dwarfism
Lack of growth hormone, normal proportions with short stature
Describe mineral deposition (mineralization)
crystallization process; calcium phosphate (& other ions) taken from blood, deposited in bone tissue
(process of putting minerals into bones)
During mineral deposition, what do osteoblasts produce?
Collagen fibers that spiral length of osteon
What happens to fibers during mineral deposition?
Become entrusted with minerals & hardens matrix (calcium and phosphate (hydroxyapatite)
What is the process for when concentration must reach critical value for crystal formation to occur?
Solubility product
Where can abnormal calcification or ectopic ossification occur?
may occur in lungs, brain, eyes, muscles, or arteries (arteriosclerosis)
Define calculus?
Calcified mass in otherwise soft organ (where it shouldn’t be and in large amounts)
What is mineral resorption?
process of dissolving bone & releasing minerals into blood
Mineral resorption is performed by…
performed by osteoclasts at ruffled border
hydrogen pumps in membranes secrete H+ into space betw/ _______ & ________
(Cl- follow by _______ attraction)
HCl (pH 4) _______ bone minerals
acid phosphatase enzyme digests ______
hydrogen pumps in membranes secrete H+ into space betw/ OSTEOCLAST & BONE SURFACE
(Cl- follow by ELECTRICAL attraction)
HCl (pH 4) DISSOLVES bone minerals
acid phosphatase enzyme digests COLLAGEN
What do orthodontic appliances (braces) do?
Reposition teeth
tooth moves b/c ________ _______ bone ahead of tooth, where ______ on bone is greatest
________ slowly ______ bone in _______ zone behind tooth
tooth moves b/c OSTEOCLASTS DISSOLVE bone ahead of tooth, where PRESSURE on bone is greatest
OSTEOBLASTS slowly DEPOSIT bone in LOW-PRESSURE zone behind tooth
Phosphate are components of…
DNA, RNA, ATP, phospholipids; in pH buffers
Where is calcium needed?
needed in neuron communication, muscle contraction, blood clotting, exocytosis
What type of effect do changes in phosphate levels cause?
Little effect
Changes in calcium can be…
Serious
What is hypocalcemia?
w/ less Ca2+, Na+ channels _____ more easily, _____ cell & _____ neurons
Deficiency of blood calcium
w/ less Ca2+, Na+ channels OPEN more easily, ENTERS cell & EXCITES neurons
What does hypocalcemia cause?
Excitability of nervous system
Name examples of the excitability of the nervous system that hypocalcemia causes
- Muscle spasms, tremors, or letany
- Laryngospasm and suffocation
What is hypocalcemia?
Rare, excessive calcium in blood
Calcium homeostasis is regulated by what 3 hormones?
- Calcitriol
- Calcitonin
- Parathyroid Hormone
Describe calcitriol?
Form of vitamin D produced by sequential actions of skin, liver, & kidneys
- _____ keratinocytes use UV radiation to convert ______ to previtamin D3
- liver converts to _________
- _______ convert to calcitriol (most active form of vitamin D)
EPIDERMAL keratinocytes use UV radiation to convert STEROID to previtamin D3
liver converts to CALCIDIOL
KIDNEY convert to calcitriol (most active form of vitamin D)
What is the most active form of vitamin D?
Calcitriol
Calcitriol behaves as a hormone that raises _______ concentration
increases Ca2+ absorption by _______
increases Ca2+ resorption from _______
promotes kidney _______ of calcium ions, so less lost in ______
Calcitriol behaves as a hormone that raises BLOOD CALCIUM concentration
increases Ca2+ absorption by SMALL INTESTINE
increases Ca2+ resorption from SKELETON
promotes kidney REABSORPTION of calcium ions, so less lost in URINE
lack of ________: softness of bones in children (_______) or adults (________)
lack of VITAMIN D: softness of bones in children (RICKETS) or adults (OSTEOMALACIA)
Calcitonin is ______ by C (clear) cells of ________when _______ concentration rises too ______
Calcitonin is SECRETED by C (clear) cells of THYROID GLAND when CALCIUM concentration rises too HIGH
What does calcitonin do?
lowers blood calcium concentration
With calcitonin,
_________, reduce activity by up to 70%
less Ca2+ ________ from bones
__________; increase # & activity (deposits Ca2+ into _______)
With calcitonin,
OSTEOCLAST INHIBITION, reduce activity by up to 70%
less Ca2+ LIBERATED from bones
OSTEOBLAST STIMULATION; increase # & activity (deposits Ca2+ into SKELETON)
Calcitonin is
important in ______, weak effect in ______
________ more active in children
______ does not cause disease in adults
reduces bone loss in _______
Calcitonin is
important in CHILDREN, weak effect in ADULTS
OSTEOCLASTS more active in children
DEFICIENCY does not cause disease in adults
reduces bone loss in OSTEOPOROSIS
Parathyroid Hormone (PTH)
_______ by parathyroid glands on _______ surface of thyroid gland
PTH released w/ ____________ levels
Parathyroid Hormone (PTH)
SECRETED by parathyroid glands on POSTERIOR surface of thyroid gland
PTH released w/ LOW CALCIUM BLOOD levels
What does PTH do?
Raises blood calcium level
With PTH,
causes ________ to release factor RANKL – increase _______ population
promotes Ca2+ ________ by kidneys
promotes _________ in kidneys
inhibits _________ & __________ by osteoblasts
With PTH,
causes OSTEOBLASTS to release factor RANKL – increase OSTEOCLAST population
promotes Ca2+ REABSORPTION by kidneys
promotes CALCITRIOL SYNTHESIS in kidneys
inhibits COLLAGEN SYNTHESIS & BONE DEPOSITION by osteoblasts
Describe what calcitriol, calcitonin, and PTH do
Calcitriol - raises blood calcium concentration
Calcitonin - lowers blood calcium concentration
PTH- raises blood calcium levels
What other factors affect bone?
Hormones, vitamins, and growth factors
bone growth rapid in puberty & adolescence
surges of GH, estrogen, & testosterone occur; promote ________
stimulate osteogenic cells, matrix deposition by ________ & ________ in metaphyses
girls grow _____
boys grow _____
bone growth rapid in puberty & adolescence
surges of GH, estrogen, & testosterone occur; promote OSSIFICATION
stimulate osteogenic cells, matrix deposition by OSTEOBLASTS & CHONDROCYTES in metaphyses
girls grow FASTER
boys grow LONGER
What causes growth to stop and how?
- anabolic steroids cause growth to stop
- epiphyseal plate “closes” prematurely
- short adult stature
What was orthopedics originally?
originally treatment of skeletal deformities in children
What is orthopedics now?
prevention & correction of injuries & disorders of bones, joints, & muscles
What does orthopedics include?
includes design of artificial joints & limbs, treatment of athletic injuries
What are stress fractures? Give example
caused by abnormal trauma
Ex) falls, athletics, military combat, car accidents
What are pathological fractures? Give examples
break in bone weakened by disease
Ex) bone cancer or osteoporosis
How are fractures classified?
______ in skin?
multiple _____?
By structural characteristics
BREAK in skin?
multiple PIECES?
Name 4 types of bone fractures
- Nondisplaced
- Displaced
- Comminuted
- Greenstick
What are the 4 stages of healing of fractures?
Hematoma Formation –> Soft Callus Formation –> Hard Callus Formation –> Remodeling
What’s the difference between a closed reduction and an open reduction?
Closed reduction - no surgery (cast to heal)
Open reduction - surgical exposure of bone - use of plates, screws, or pints to realign fragments
Name and describe the most common bone disease
Osteoporosis - severe loss of bone density
What happens when you have osteoporosis?
Bones lose ____, become ______
affects ______ bone
subject to _____________of hip, wrist, vertebral column
Bones lose MASS, become BRITTLE
affects SPONGY bone
subject to PATHOLOGICAL FRACTURES of hip, wrist, vertebral column
What is the correct term for a widow’s hump? Define it.
Kyphosis - deformity of spine to due to vertebral bone loss
In osteoporosis, _________ maintains density in both sexes; inhibits ________ by osteoclasts
in women, rapid _______ after menopause since ovaries cease to secrete estrogen
In osteoporosis, ESTROGEN maintains density in both sexes; inhibits RESORPTION by osteoclasts
in women, rapid BONE LOSS after menopause since ovaries cease to secrete estrogen
Osteoporosis
Can occur in young female ________ w/ low _______ (might stop ovulating)
______ estrogen low
Osteoporosis
Can occur in young female ATHLETES w/ low BODY FAT (might stop ovulating)
OVARIAN estrogen low
¼ of women will have _______ due to osteoporosis by age ____________
¼ of women will have FRACTURE due to osteoporosis by age 70
What population has the greatest risk for osteoporosis?
begin to lose _______ as early as age ___
by age ____, average loss is ____% of bone mass
risk factors: race, age, gender, smoking, diabetes, calcium-poor diet, protein, vitamins ___ & __
Postmenopausal white women
begin to lose BONE MASS as early as age 35
by age 70, average loss is 30% of bone mass
risk factors: race, age, gender, smoking, diabetes, calcium-poor diet, protein, vitamins C & D
What can be used to treat osteoporosis?
Estrogen Replacement Therapy (ERT)
What does Estrogen Replacement Therapy (ERT) do? And what drugs are they?
slows bone resorption, but increases risk of breast cancer, stroke, heart disease
drugs: Fosamax, Boniva, Actonel, Reclast
How do ERT work?
By preventing you from getting worse
What is the best treatment for osteoporosis?
Prevention — exercise and good bone-building diet between ages 25-40
