Studied by 41 people
This study set covers the material from lecture (the rest of skeleton system, bone ossification, knee/joint, and part of the muscular system
Function of hormonal control of bone metabolism
to maintain blood calcium levels within a narrow range
What range is the blood calcium level kept between?
9-11 mg/ 100ml
The maintenance of blood calcium levels can be at the expense of the skeleton. (T/F)
true
What is calcium important for in the body?
muscle contraction, nerve pulse transmission, blood clotting, secretion of glands and near cells, and cell division
What is calcium vital for in the body?
muscle contraction (i.e. heart and lungs) and nerve pulse transmission
Parathyroid hormone (PTH)
most important hormone in bone metabolism
When is PTH secreted?
when the calcium level in the blood is too low
What is PTH secreted by?
parathyroid gland
hypocalcemia
low blood calcium levels
hypercalcemia
high blood calcium levels
What are the effects of PTH being released?
stimulates osteoclast reabsorption, increases calcium absorption in the intestine and reabsorption in the kidney
Osteoclasts reabsorbing bone allows for what?
the release of calcium into circulation (increase in blood calcium)
How does the absorption of calcium into the intestine happen?
through the activation of vitamin D in the kidney
In calcium homeostasis, what are the effectors?
osteoclasts, kidneys, and intestines
In calcium homeostasis, what is the efferent pathway?
the liver and kidneys
In calcium homeostasis, what is the control center?
the parathyroid gland
PTH activates vitamin D to D3 (T/F)
true
Osteoblasts are part of the calcium homeostasis process (T/F)
false
When is calcitonin secreted?
when calcium levels in the blood are too high
What is calcitonin secreted by?
parafollicular cells of the thyroid gland
calcitonin is only secreted once calcium levels exceed ___%
20
Calcitonin
inhibits osteoclasts and acts to accelerate bone deposition, decreasing calcium levels
Calcitonin’s effects are short lived and it does not have an important role in calcium homeostasis (T/F)
true
Calcium levels are homeostatically regulated, but bone metabolism is not. (T/F)
true
All people will have normal bone loss throughout life, with women being greater at risk. (T/F)
true
Osteoporosis
a disease where bone reabsorption is greater than bone deposition to the point that bones become porous and lighter
Peak bone mass generally occurs between what ages?
25-35
During osteoporosis the composition remains normal, but the bone mass is reduced. (T/F)
true
X-rays are unable to pick up on osteoporosis until what percent of bone mineral is lost?
30-50
Trabecular bone loss begins at what age?
20
What becomes more likely with trabecular bone loss?
compressional fractures of the vertebrae and hip fractures
The femoral neck is what percent trabecular bone?
45
The most important thing to prevent osteoporosis is to increase the consumption of what?
dietary calcium
What type of calcium is the best for preventing osteoporosis?
calcium (carbonate) with vitamin D
How much calcium do you need in a day?
1000-1200 mg
How much vitamin D do you need in a day?
500 IU
What is the second most influential factor on osteoporosis?
Estrogen and testosterone levels
Sex hormones like estrogen and testosterone _____ (promote/restrain) osteoclast activity
restrain
Testosterone decline is must more dramatic than estrogen decline (T/F)
false
Because estrogen declines sharply, women are more vulnerable to osteoporosis (T/F)
true
Amenorrhea
irregular menstruation of women
Why are women who menstruate less more likely to have calcium deficiency and osteoporosis?
they are not producing enough estrogen to stop bone mass loss
Estrogen and progesterone birth control
stops ovulation, but allows for estrogen intake
Progesterone only birth control
inhibits menstruation completely, no estrogen intake
How to minimize bone mass decline?
regular calcium intake and weight-bearing exercise
What outside factors can cause calcium loss?
smoking, excessive protein intake, and sodium chloride intake
The human skeleton is initially made up of what?
cartilage and fibrous membranes
In the human skeleton, cartilage eventually becomes bone (T/F)
false
Before ___ weeks the embryo’s skeleton is entirely fibrous membranes and cartilage
8
Intramembraneous ossification
bone develops from a fibrous connective tissue membrane producing the membrane bones
General steps for intramembraneous ossification
fibrous c.t. cells become osteoblast → formation of ossification center → mineralization of osteiod → trapped osteoblasts become osteocytes → formation of the rest of the bone elements
Intramembraneous ossification deals with osteoclasts (T/F)
false
Intramembraneous ossification is use to form what type of bones?
flat and irregular bones
Intramembraneous ossification can be used to form long bones, but usually is not (T/F)
false
Heterotopic bones
bones that develop in unusual places
Myositis ossificans
muscle inflammation causes bone deposition around the skeletal muscle
Fibrodysplasia ossificans progressiva
bone deposition that occurs outside the skeletal system and into connective tissue; congenital disease
Heterotopic bone is formed by the same process that membraneous bone is created (T/F)
false
fibrous connective tissue is made up of what types of connective tissues?
dense regular and dense irregular connective tissues
Endochondral ossification
hyaline cartilage is used as a model for bone construction, producing cartilage bones
What kind of bones does endochondral ossification form?
long bones and sesamoid bones
Mesenchymal cells
crowding together of connective tissue cells, differentiate into chondroblasts which make a cartilage matrix; young cells
The cartilage “model” does not grow in length or thickness (T/F)
false
General steps of endochondral ossification
cartilage cells under periosteum specialize into osteoblasts → cartilage cells enlarge and calcify → periosteal bud forms → osteoclasts break down new spongy bone (medullary cavity formation)
In endochondral ossification osteoblasts form the bone collar and produce bone that moves to the inside (T/F)
false
Does creation of a medullary cavity occur in the epiphysis of bones? (yes/no)
no
Bone collar
forms around the shaft of the forming bone, encasing the cartilage; for support
What signals the calcification of the matrix?
pH changes within the shaft
What makes up a periosteal bud?
vessels, nerve fibers, lymphatic, red marrow, osteoclasts, and osteoblasts
Osteoclast function in endochondral ossification
erode calcified cartilage matrix and new spongy bone, creating the medullary cavity
Osteoblast function in endochondral ossification
secrete osteoid that calcifies into hard, spongy bone
The secondary ossification centers in the epiphyses of long bones are formed _____ (before/after) birth
before
What places does hyaline cartilage remain after endochondral ossification
on the ends of bones where there is a junction (articulation) with another bone and between the diaphysis and epiphysis
Epiphyseal places (growth plates)
the hyaline cartilage that remains between the diaphysis and epiphysis of long bones, where growth of bones occurs after birth
Important hormone for bone growth after birth
human growth hormone (hGH)
Where is hGH secreted from?
the anterior pituitary gland
Bone growth is also affected by the release of what two hormones?
estrogen and testosterone
High levels of testosterone and estrogens induce ________.
the closure of the epiphyseal plate
Bone growth can occur in thickness, especially in response to stress (T/F)
true
Bone remodeling
microscopic areas of bone are continuously broken down, reabsorbed, and reconstructed
How does bone remodeling work?
“remodeling units” of adjacent osteoclasts and osteoblasts
Where does bone remodeling occur?
at the periosteal and endosteal surfaces of bone (internal and external surfaces of the bone)
Remodeling is uniform (T/F)
false
Remodeling occurs in some bone areas more frequently than others (T/F)
true
Example of bone remodeling
distal end of femur is totally replaced more than twice a year
No remodeling would cause only the bone ends to grow without shaping of the bone occurring as well (T/F)
true
When does bone remodeling occur?
through the lifetime of an individual
The rate of bone deposition increases with what?
injury or stress on the bone
Large bony projections occur where heavy, active muscles attach (T/F)
true
Why does bone remodeling occur?
to respond to mechanical and gravitational forces
Atrophy in bones increases with what?
when bones are not stressed by weight bearing exercise or stretch of muscles
Why does bone remodeling occur?
to maintain calcium homeostasis in extracellular fluid
Malformation of bones is a reflection of a malfunction of what bodily system?
the endocrine system
Giantism
over secretion of hGH (hyper hGH) before puberty
Dwarfism
under secretion of hGH (hypo hGH) before puberty
Achondroplastic dwarfism
genetic; only affects the epiphyseal plates of long bones, no response to hGH; normal size of head and torso
Acromegaly
hypersecretion of hGH just after puberty, increased thickness of bones
The knee joint is not enclosed anteriorly by the joint capsule (T/F)
false
What makes up the joint capsule?
fibrous dense irregular connective tissue and inner synovial membrane
The joint capsule ____ the joint cavity
forms
Note 
Flashcard (123)