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

http://content.nejm.org/content/vol332/issue5/images/large/06f1.jpeg

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)