Calcium

Approximately 99% of the calcium of the body is present in the inorganic matrix of bone as _________

Hydroxyapatite

This is an intracellular calcium-binding proteins________

calmodulin

What is the shortest name of the 1,25-dihydroxyvitamin/ 1,25-dihydroxycholecalciferol

Calcitriol

Calcium serves two primary functions in the body which are?

structural integrity of bones and teeth, and messenger or regulatory ion.

What are the 3 forms of calcium?

Ionized calcium, complexed calcium, protein bound

The kidney normally reabsorbs __ or more of filtered calcium?

98%

The principal stimulator of calcium reabsorption in the distal convoluted tubule is__________.??

parathyroid hormone

Reabsorption of calcium in the distal convoluted tubule is an active transcellular process requiring the presence of calcium channes? Which are

calcium-binding proteins

What are the example of calcium-binding proteins?

calbindins, a Ca?*-ATPase, and Ca2+

The ___________of the urine is a better indicator of calcium excretion

Ca/Cr ratio

The ___________________ is best measured in a fasting animal to eliminate, the role of dietary calcium on renal calcium excretion.

Fractional calcium excretion

The _________excretion is a good measurement of daily calcium loss and may be used to investigate calcium balance.

24-hour calcium

There are two components of calcium absorption from the intestinal tract, namely?

Saturable and non-saturable

About 70% of filtered calcium is reabsorbed in the __________________________

proximal convoluted tubules

The ______________________also absorbs about 20% of the filtered calcium.

thick ascending loop of Henle

the _________________, which reabsorbs approximately 10% of the filtered calcium.

distal convoluted tubule

Saturable transport is a ___________, ___________process and occurs predominantly in the duodenal segment

carrier-mediated, vitamin D-dependent

The _________requires influx of calcium into intestinal epithelial cells via Calcium channels, movement and buffering in the cytoplasm, and basolateral exit by a Cat-ATPase.

Saturable transport

The____________________ occurs throughout the small intestine and is the main mechanism for calcium absorption in animals deficient in vitamin D

nonsaturable calcium transport.

Fractional intestinal calcium absorption is approximately ____ in adult animals and can exceed __ during increased demand for real-cium.

20-40%, 60%

Fractional absorption is increased during?

pregnancy, lactation, growth, and when animals are fed low-calcium diets.

Factors which increase intestinal calcium absorption, directly or indirectly, due to stimulation of 1,25-dihydroxyvitamin D synthesis, include:

parathyroid hormone, growth hormone, testos-terone, estrogen, and furosemide.

Factors that reduce intestinal absorption of calcium, include:

glucocorticoids, thyroid hormones, chronic acidosis.

two sources of Ca? in bone

mobilizable calcium salts and hydroxyapatite crystals

hydroxyapatite crystals that require digestion by ______ before Cal+ can be released from bone.

osteoclasts