CalciumNormal calcium level9 – 11 mg/dl9.4 mg/dl or 2.4 mmol /L

Calcium importantContraction of skeletal musclesContraction of smooth musclesCardiac muscle contractionTransmission of nervous impulsesClotting of bloodSecretory activity of the glands

CalciumExcitable tissues are very sensitive to changed calcium levelHypercalcemia→ depression and sluggishness of

nervous tissueHypocalcemia → increased excitability of nervous

tissue99 % calcium in the bones

Reservoir and store (buffer calcium level in ECF)0.1 % in the extra cellular fluid1 % in the intracellular fluid

Phosphate85 % stored in bones14-15 % in the ICFLess than 1 % in ECF

Three forms of calciumBound to plasma proteins41 %Nondiffusible Non ionizable

Bound to citrates, oxalates, phosphates etc9 %Diffusible Nonionizable

50 % ionic calcium IonicDiffusibleFunctionally the most important calcium

PhosphateHPO4

-- 1.05mmol/L

H2PO4- 0.26 mmol/L

↓ pH → ↑ H2PO4-

↑ pH → ↑ HPO4—

Phosphate level expressed as total quantity of phosphorus in mg/dl

Normal levels Children 4-5 mg/dlAdults 3-4 mg/dl

Hypocalcemia and tetanyHypocalcemia → ↑ excitability of nervous tissue↑ neuronal cell membrane permeability to Na+ Easy initiation of depolarization and action

potential50 % reduction in Calcium level → spontaneous

nervous impulses → propagation to skeletal muscles → spontaneous tetanic contraction of the skeletal muscles Tetany

TetanyInitially spontaneous tetanic contraction of

the muscles of hand and forearm i.e. carpopedal spasm develops

Tetany develops at calcium level of about 6 mg/dl

Lethal at 4 mg/dl levelLatent tetany at level between 6 and 8Minor stimulus causes nervous discharge

HypercalcemiaLevel 12 mg/dl

Depression of nervous systemSluggish reflexesDecreased QT interval of heartLack of appetiteConstipation

Level 17 mg/dlPrecipitation of calcium in all the tissues

Calcium absorption and excretionDaily intake 1000 mgSecretion in GIT secretions 250 mgAbsorption 350 mgExcretion in the feces 900 mgNet absorption 100 mgExcretion in urine 100 mgCa ++ like all other bivalent cations are

very poly absorbedIts absorption requires activated vitamin

D

Renal excretion of CalciumDaily excretion 100 mg99 % of filtered calcium absorbed

PCT. LH, DCT and CDDaily filtration 9980 mg Daily absorption 9880 mgHypocalcemia No excretionHypercalcemia proportionate excretion

Renal excretion of PhosphateThreshold substanceNo excretion if level is below 1 mmol/LHigher level proportionate excretion