Damion Francis MSc.
TMRI-ERU
Chemical elements required by living organisms other than C, H, O, N
Naturally occurring in foods and must be taken in the diet
Comprise of 4% of the body weight Classified according to the amount needed by the
body
Macrominerals- required in large proportions by the body (≥100mg)
Includes: calcium, phosphorus, magnesium, etc. Microminerals (Trace elements)- required in
relatively small amount by the body These include iron, zinc, cobalt and manganese
BONE Bone is made up of an inorganic mass of minerals
with a protein matrix (collagen) Major component is calcium and phosphate along
with a other minerals and trace minerals Concurring with biological theory increase in fruit
and vegetable intakes was associated with stronger bones in several studies
The exchange of Ca and P between the extracellular matrix and body fluids are regulated by the parathyroid hormone (PTH) and vitamin D
Bone has two growth phases: Formation of a protein matrix (collagen produced by
osteoblasts) which can be calcified Calcification (calcium phosphate is precipitated from serum)
Remodeling involves the building of bone by osteoblasts which are then broken down by osteoclasts
Subsequently rebuilt by osteoblast mainly through the production of hydroxyapatite (Ca10(PO4)6OH2), the primary inorganic constituent of bone and teeth
The apatites develops and mature into calcified crystals increasing bone density
Teeth Mineralization of cementum and dentin is similar to
bone Calcification of enamel differs from the above
mentioned Mineralization and matrix formation occur
alongside enamel development Mineral content of enamel is 95-97% with only a
trace of organic matrix
Enamel development begins with the differentiation of cells of the oral epithelium
Thickens to form a protruded inner enamel epithelium
Results in formation of ameloblasts which secretes enamel proteins such as amelogenin
Also involved in transport of calcium and phosphate in enamel matrix
Enamel proteins such as amelogenin mediate the formation of hydroxyapatite crystals from calcium and phosphate through enamel biomineralization
Protein fraction in developing enamel is an aggregate of small proteins most of which are phosphoproteins
Once enamel is completely mineralized only phosphopeptides remain (phosphorus and 1 or 2 aa)
Adult body contains 1-1.5kg of ca Function
Deposit in soft tissue to harden them Plays part in controlling heart action, skeletal
muscle & excitability of the nerve Has role in blood clotting (prothrombin &
thrombin) Enzyme cofactor (pancreatic lipase) Chromosomal movement before meiosis
MetabolismAbsorbed mainly in upper small intestineFacilitated by vit. D, proteins, acid pHReduced by phytic acid, oxalic acidTransported as free ion or bound to
albumin
Blood levels are regulated by PTH, calcitonin (thyroid gland), and active vit. D
storage deposit of calcium is bone trabuculae in long bones
Bones are metabolically active but can calcium can be withdrawn when needed
Approximately 250 – 1000mg of calcium enters and leave the bone daily
Homeostasis is maintained from dynamism between blood levels and bone
Diet and resorption contributes to the blood levels which act as a reserve
Osteoid formation is directly regulated by amount of calcium from diet
Calcium balance is obtained when there is sufficient calcium absorbed to meet body requirements for growth and tissue regeneration
Negative balance when insufficient consumed and body mobilize calcium from bone to maintain necessary blood levels
PTH ACTIVATED VITAMIN D CALCITONIN
BONE KIDNEY SMALL INTESTINE
THREE HORMONE AND THREE ORGANS
principal regulator of [Ca] in ECF by [Ca] and [Pi]
If blood levels of iCa 0.1 mg/dl, secretion of PTH is
Kidney reacts quickly to changes in PTH minute to minute adjustments of blood Ca
PTH acts on distal nephron to urinary excretion of Ca
steroid hormone regulate specific gene expression following
interaction with its intracellular receptor biologically active form is 1,25-dihydroxy vitamin
D3 (1,25-(OH)2D3, also termed calcitriol) calcitriol functions primarily to regulate calcium
and phosphorous homeostasis
Parafollicular cells of thyroid gland in response of hypercalcaemia Decrease osteoclast activity Stimulating a distal tubular - mediated calciuresis
Other hormones affect Ca balance - including prostaglandins that mobilize Ca, various growth factors, growth hormone, somatomedins, thyroid hormones (decrease skeletal mass), sex steroids which help maintain bone mass, adrenal cortical hormones
Sources
dairy product, fortified flour, egg,leafy vegetable, fish, cabbage, broccoli
Requirement
Adult 500mg/day, Pregnancy 1200mg/day
excreted in urine and feces Deficiency
Rickets in children & Osteomalacia in adult
Food Calcium
Small Intestine Feces
Blood
UrineBonesTeeth
Unabsorbed calcium Alkaline pHOxalic acidPhytic AcidSome FibersLaxatives
Body needAcid pHVitamin CVitamin DLactoseCertain amino acids
Calcitonin (thyroid hormone)Sufficient Vitamin DWeight-bearing exercise
Parathyroid hormone Inadequate/ excess vit. DBone immobilization
Positive calcium balance Negative calcium balance
Inadequate intake, impaired absorption and increased loss include:Incomplete calcification of teethTooth and bone malformationsIncreased susceptibility to dental cariesExcessive periodontal bone resorptionIncreased tooth mobility and premature
tooth lossIncreased risk of hemorrhage
Less than 500mg calcium associated with higher risk of gingival detachment
Decreased bone mineral density (cementum and dentin)
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