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A Seminar
on Calcium Metabolism
contentsIntroductionRole of calciumNormal values,Types,Sources,Daily requirementsAbsorption,Distribution,ExcretionRegulation of blood calcium levelsApplied physiologyImportance of calcium in ProsthodonticsConclusionReferences
Introduction
Most abundant mineral in the body
Calcium interacts with phosphorous forming Calcium phosphate
Role of Calcium
1. Neuronal ActivityCalcium is necessary –
-- For transmission of impulses from pre synaptic to post synaptic region
-- For the release of neurotransmitter from synaptic vescicle
2 Muscular ActivityCalcium mediates excitation-contraction coupling of muscle fibers
Skeletal Muscle - Calcium binds with Troponin c and Tropomyosin
Smooth Muscle – in place of Troponin Calcium binds with Calmodulin
3. Hemostasis
Necessary for activation of clotting factors in blood coagulation
4. Formation of bone and teeth
5. Membrane stabilization
6. Secretary activity of glands
7. Activation of enzymes
Normal Values
Total body Calcium – 1100g(1.5 % of total body weight)
Out of this - 99% in bone
- 4-5 g in soft tissues
- approx 1g in extra cellular fluid
Normal Serum Calcium
- 9-11 mg%
Types 1. Diffusible
Ionised calcium- physiologically active form (50%)
Non Ionised Calcium- Calcium complexed with anions (9%)
2. Non Diffusible (41%)Calcium bound to albuminPhysiologically inactive
Sources Milk, Egg, Fish ,Leafy Vegetables, Cereals
Daily Requirement
Adult - 500 -800mg per day
Children - 1200mg per day
Pregnancy and Lactation -1500mg per day
After age of 50 tendency for osteoporosis may be prevented by-
Calcium (1500mg/day)+ Vitamin D (20mg/day)
Absorption of CalciumMainly from 1st and 2nd part of Duodenum
Absorbed against a concentration gradient
Requires a carrier protein- Calbindin helped by calcium dependent ATPase
Factors Increasing•Vitamin D•Calcitriol•Parathyroid Hormone•Amino Acids..lysine,Arginine
Factors Decreasing• Phytates•Oxalates•Malabsorption Syndrome•High Phosphate content
Factors affecting Absorption
Regulation of Blood Calcium Levels
Three hormones that regulates blood calcium levels
1. Parathyroid hormone
2. 1,25-dihydroxycholecalciferol
3. Calcitonin
1. Parathyroid Hormone(PTH)A polypeptide secreted by chief cells of parathyroid gland
Synthesised from a precursor Prepro-PTH
Acts via activation of adenylyl cyclase
Actions
a. Action on Bones
Increases plasma calcium concentration by promoting bone resorption
Occurs in 2 Phases
Rapid Phase (Early Phase)-Osteolysis
Slow Phase- Activation of Osteoclasts
b. Action on Kidneys
Increases renal tubular reabsorption of calcium
Occurs mainly in the distal tubules, collecting tubules, collecting duct and to a lesser extent in ascending loop of Henle
c. Action on GIT
Increases calcium absorption from intestine-by increasing the formation of 1,25 dihydroxycholecalciferol
2. 1,25 – dihydroxycholecalciferol
Activated form of Vitamin D
Increases calcium absorption from intestine
3. Calcitonin
A peptide hormone secreted by C cells of thyroid gland
Reduces Blood calcium level by acting on-
Bone-deposition of calcium
Kidney-Increases calcium Excretion
Intestine-Prevents Calcium Absorption
Applied Physiology1.Hypoparathyroidism
Decreased secretion of PTH- Hypocalcemia(calcium <8.5mg/dl)
Hypocalcemic tetany – neuromuscular hyper excitability- Occurs if the plasma calcium level falls below 6mg%
Signs and symptoms • Carpopedal Spasm -Trousseau’s Sign(Figure)
• Laryngeal Stridor• ECG Changes• Can be detected by 1, Trousseau’s Sign 2, Chvostek’s Sign 3. Erb Sign
2. Hyperparathyroidism
Increased secretion of PTH-Hyper calcemia
Radiology of hyperparathyroidism
OsteoporosisBone disease characterised by loss of bone matrix and minerals
Due to excessive bone resorption and decreased bone deposition.
Risk factors
1.sedentary life
2.genetic factors
3.early menopause/ ovariectomy
4.excessive alcohol intake
5.prolonged medication with corticosteroids.
6.hypothyroidism,cushings syndrome,
acromegaly, hypogonadism.
3. RicketsBone disease occurring in children due to vitamin D deficiency
4.Osteomalacia(Adult Rickets)
5.Renal OsteodystrophyA consequence of chronic renal failure related to calcium metabolism
Importance of calcium in Prosthodontics
Necessary for the normal growth of bone and teeth.
In osteoporosis, - RRR will be more- affect denture retention – frequent relining is needed
Amount and density of available bone in edentulos site is the primary determining factor in predicting the success of an implant.