Calcium and phosphate Flashcards
what is the normal Ca ions concentration in blood plasma
2.4 mmol/L
how does calcium is present in blood plasma
50 % are free Ca ions. unbound to anything, most important form for body function
40% is bound with plasma protein
10% is bound with citrate or phosphate
in which form the Ca can diffuse easily through membrane
free form
in which form Ca is not able to diffuse through capillary membrane
when bind with plasma protein so it stay in circulation
in what form Ca can diffuse through capillary membrane and is easier to use by cell
when bind with citrate or phosphate
what is the tissue that is a large reservoir for calcium and phosphate
bone
which absorption between phosphate and calcium is more efficient
phosphate
what are the 2 form of phosphate in blood plasma after absorption
form of HPO4 (1.05 mmol/L) and H2PO4 (0,26 mmol/L)
what happen with phosphate when the extracellular fluid is more acide
concentration of HPO3 decrease with relative increase of H2PO4
the excretion rate of phosphate is regulated by what
phosphate concentration in plasma and by parathyroid hormone
what is the crital value of phosphate concentration and what happen if it reach it
1mmol/L, all phosphate are reabsorbed and theres no loss into urine
what happen if phosphate concentration is above critical value
excretion in urine is proportional to the increase of phosphate concentration.
the bone are also a reservoir of _ in the _ form
phosphate in the ionic form
up to 30% of bone tissue hase organic matrix composed of
Collagen fibers (majority) that give tensile strength. Ground substance (mionority) including extracellular fluid, chondroitin and
hyaluronic acid (HA).
The rest of bones chemical structure is inorganic salt crystals composed of:
Hydroxyapatite which has the chemical structure consistiong of calcium and phosphate Ca10(PO4)6(OH)2. Many other types of salts of magnesium, sodium, potassium and carbonate ions.
what give the compressional strength to the bone
Hydroxyapatite which has the chemical structure consistiong of calcium and phosphate Ca10(PO4)6(OH)2
the bonne tissue is also surround in a extracellular fluid that contain what
exchangeable Ca and PO4- ions
what are the 2 type of cell that live in bone
osteoclast and osteoblast
which type of cell on the bone secretes collagen monomer and ground substance
osteoblast
what is the ground surface secretes by osteoblast in the pas
proteoglycan
osteoclast is a large _ cell in bone _
phagocytic, marrow
what happen when osteoclast developed
it sends out villus-like projections toward the bone to form a
ruffled border adjacent to the bone.
what are the 2 substances secretes by the villus
- Proteolytic enzymes (released from lysosomes of osteoclast) to digest and dissolve organic matrix.
o 2. Citric acid and lactic acid (released from mitochondria) to dissolve bone salts.
proteolytic enzyme are release from what
lysosome of osteoclast
role of proteolytic enzyme
digest and dissolve organic mattrix
role of citric acid and lactic acid
dissolve bone salt
citric acid and lactic acid are release from
mitochondria
shat is the name of new area of bone deposited
osteon
when does the deposition of new bone stops
when the bone mass begins to encroach the blood vessels
what is the significance of bone remodelling
The new bone replaces the old bone mass that is relatively brittle and weak so that the
normal toughness of bone can be maintained.
because the bone deposition rate is (proportional/ non proportional) to the _ on the bone it can adjust bone _ according to the degree of bone stress
proportional, compressional stress, strength
what does compressional stress can produce
piezoelectric effect
what is piezoelectric effect
it develops a negative electrical potential in the compressed area and a positive potential elsewhere in the bone.
what does piezoelectric effect promote
Promotes osteoblastic activity at the negative end of the current flow, ➔ Increases the deposition at compression sites.
what maximally activate osteoblast
fracture
what can be a good indicator of the rate of bone deposition and why
alkaline phosphatase in the blood,because when the osteoblasts are depositing bone matrix they secrete large amount of alkaline phosphatase that diffuses into blood.
which vitamin pays a keys role in regulating calcium and phosphate ions, role of liver and kidney
vitamin D
how does vitamin D3 is form in the skin
7-dehydrocholesterol by ultraviolet rays from the sun.
which hormone is required to promote conversion of 25-hydroxycholecalciferol to calcitriol
parathyroid hormone
in the liver there is a direct/indirect negative feedback to keeps the process slow to preserve vitamin D
direct
in the kidney there a direct/indirect negative feedback
indirect
the formation of calcitriol is inversely affected by
calcium concentration in plasma
what happen when Ca ions concentration in blood is too high
it suppress secretion of parathyroid hormone from parathyroid gland. so there is less calcitriol formation
what is a high concentration of CA ions in kidney
above 9-10 mg/dl
what happen when calcitriol is too low in the kidney
body will excrete Ca
how does calcitriol promotes absorption of calcium by intestinal tract
By increasing the formation of calcium-binding protein in intestinal epithelial cells ➔ promotes the transport of calcium through cell membrane by facilitated diffusion.
By promoting the formation of calcium stimulated ATPase (enzyme) in the border of the intestinal epithelial cells and increasing alkaline phosphatase in the epithelial cells. This converts calcium into an easy to absorb phosphate form.
What is the effect of calcitriol on phosphate ions?
It enhance absorption of phosphate ions in gastrointestinal tract. Thus, Ca2+ ions and phosphate ions are co-transported since they interact with each other.
what happen when calcium ion concentration is 50% below normal
- The membranes of cells become more permeable to sodium (Na+) which allows for easy initiation of membrane action potential.
- The nerve fibers become very excitable and elicit spontaneous nerve impulses to the peripheral skeletal muscles which causes tetanic muscle contraction (tetany).
what can hyperalcemia can cause
- Depress of nervous system.
- Reflex of CNS becomes sluggish.
- Decreases QT interval of the heart.
- Constipation.
- Lack of appetite.
T/F Phosphate ions can go extremely low, or 2 - 3 fold above normal without consequence.
T
parathyroid gland is composed of which cell
chief cell and oxyphil cells
role of chief cell
Synthesize and secrete parathyroid hormone.
parathyroid hormone are synthesized and secrete from
chief cell
which cell in parathyroid gland is absent in many animal and young human
oxyphil cell
What is the effect of PTH on on calcium and phosphate ions excretion by kidney?
- PTH will decrease the excretion of calcium in the urine by increasing the tubular reabsorption of calcium ( as well as magnesium, hydrogen ) by kidney.
- PTH will increase excretion of phosphate in the urine because parathyroid hormone
reduces the tubular reabsorption of phosphate ions (and Na , K , and amino acids ).
what are the 2 phase where PTH will increase absorption of Ca2+ ions and phosphate ions from bones
Rapid phase of calcium and phosphate absorption (Osteolysis) begins in minutes and increases progressively for several hours.
Slow phase of bone absorption and calcium phosphate release
where does parathyroid hormone cause absorption of bone salt
vicinity of existing osteocyte and vicinity of osteoblast along bone surface
what does spare the bone from extracellular fluid
The osteocytic membrane system
What is the effect on calcium and phosphate concentration on extracellular fluid?
Increase of blood calcium concentrationDecrease of blood phosphate concentration ( even though the phosphate absorptions from bone and intestine are increased )
increase of blood calcium is caused by
Increasing the absorption of calcium from bone,
Decreasing the excretion of Ca2+ ions in urine and increasing reabsorption of Ca
by kidney,
Increasing vitamin D for promoting absorption of Ca2+ ions by intestine.
decrease of blood phosphate concentration is caused by
excessive phosphate excretion in
urine.
slight (increase/decrease) of Ca concentration cause. (increase/decrease) of secretion rate of parathyroid hormone
decrease, increase
parathyroid gland will enlarged if
decrease of Ca2+ ions concentration persists,
in pregnancy or lactation ( Ca2+ ions are used for milk production ).
(increase/decrease of Ca2+ ions concentration above normal causes decreased activity and size of
parathyroid glands.
increase
what is calcitonin
large polypeptide hormones
calcitonin is synthesize and secrete from
synthesized and secreted from C cell in thyroid gland (not parathyroid glands) in
human being.
do calcitonin is synthesize and secrete from parathyroid gland
no
calcitonin reduced blood Ca concentration by
Short term effect to decrease absorption of osteoclasts.
Long term effect to decrease the production of new osteoclasts, ➔ in turn,
depress the formation of osteoblasts, ➔ reduce both osteoclastic and
osteoblastic activities.
why does calcitonin has only a weak effect on blood Ca in adult
because the initial reduction of Ca2+ ions resulted from by calcitonin will cause powerful stimulation of
secretion of parathyroid hormone,
in adult, the daily absorption and deposition rate of Ca ions are (smalll/large( and has (small/large) effect on blood Ca ions concentration
small, small
How is calcitonin secretion regulated?
Increase of blood calcium concentration (10%) causes increase of secretion rate of
calcitonin (twice or more).
Calcitonin is the second hormonal feed-back mechanism for controlling blood Ca2+ ions
(increase/decrease) of blood calcium concentration (10%) cause (increase/decrease) of secretion rate of calcitonin
increase, increase
what is the second hormonal feedback mechanism for controlling blood ca ions
calcitonin
difference between calcitonin and parathyroid feedback
Calcitonin mechanism operates more rapidly. Time for reaching to peak activity:
For calcitonin: in < 1 hour.
For parathyroid hormone: in > 3 to 4 hours.
Calcitonin mechanism acts weakly and as a short-term regulator of Ca2+ ions concentration but parathyroid hormone is more potent and acts over prolonged period of 17 time.
what is the first line of defense that prevent uncontrolled Ca ions in blood plasma
buffer system of exchangeable salts of bone
what is the buffer system
A small percent (<1%) of total bone calcium are exchangeable Ca2+
ions. They can go back and forth to blood plasma or bone extremely fast
how does the buffer react if there is a slight increase of Ca ions in extracellular fluid above normal
it will cause immediate deposition of exchangeable calcium ions into the bone. Now, the Ca2+ ions concentration in extracellular fluid can return to normal.
how does the buffer react if there is a slight decrease of Ca ions in extracellular fluid below normal
the extracellular calcium concentration is too low then the exchangeable calcium can release into the extracellular fluid.
