2. excitability of cell membranes
neuromuscular transmission and muscle
contraction
releasing of transmitters from synapses
“second messenger”
stimulates secretory activity of exocrine
glands and releasing of hormones
contractility of myocardium
blood coagulation
4. 99% of skeletal calcium forms stable bone (not
exchangeable with the Ca in extracellular fluid)
1% is in the form of releasable pool of Ca
Balance of deposition and resorption
Osteoblasts – bone-forming cells responsible for
bone deposition
◦ Secrete type I collagen
◦ Differentiate into osteocytes
Osteoclasts – “bone-eating” cells that resorb the
previously formed bone
5.
6.
7. Free is physiologically active
regulated by the combined actions of
parathyroid hormone and calcitriol
Changes in plasma [albumin] can alter
total [calcium]
‘adjusted/corrected [calcium]’ for any
abnormality of [albumin
adjusted [calcium] mmol/l=
(measured [calcium] + 0.02(40 –
[albumin g/l]))
9. Stimulation
◦ PTH (not directly – through stimulation of osteoblasts)
◦ 1,25 Dihydrocholecalciferol (not directly – through
stimulation of osteoblasts)
◦ IL-6, IL-11
Inhibition
◦ Calcitonin (directly – receptors)
◦ Estrogens (by inhibiting production of certain
cytokines)
◦ TGF-β (tranforming growth factor)
◦ PGE2(prostaglandin)
10. Parathyroid glands
polypeptide of 84 amino acids
stimulus for secretion – low plasma calcium
function – to INCREASE plasma calcium
activation of osteoclasts – stimulates
absorption of Ca, P from bones
decreases excretion of Ca by kidneys
increases excretion of P by kidneys
stimulates conversion of vitamin D to
calcitriol (vitamin D hormon) in kidneys
11. Parafollicular cells of thyroid gland (C-cells)
peptide of 32 amino acids
stimulus for secretion – high plasma calcium (food
intake – gastrin, CCK, glucagon)
function – to DECREASE plasma calcium and
phosphates
inhibits osteolysis – decreases absorption of
Ca, P from bones
stimulates incorporation of Ca, P to bones
decreases absorption of Ca, P in kidneys
decreases the effect of PTH on bones – PTH
antagonist
12. Hypovitaminosis
RICKETS (rachitis)– children
OSTEOMALACIA - adults ( less calcium)
◦ Osteoporosis is decrease of bone mass (matrix and
minerals)
Hypervitaminosis
Tissue and organs calcification
Loss of body weight
Kidney function failure
13. Age/ sex Ca (mg)
1-3 350
4-6 450
7-10 550
11-18 M 1000
11-18 F 800
19 + 700
14. Milk – 100 ml =120mg
Cheese – 15gm = 110mg
Yoghurt pot – 80gm = 160mg
Other sources
◦ Fish
◦ Meat
◦ Bread
◦ Cereal
◦ Broccoli
16. Absorption is taking place from the first and second part of
duodenum against concentration gradients
Absorption required a carrier protein , helped by Ca-dependent
ATPase
Increased absorption-
- calcitriol , active form of Vit-D
- PTH
- acidic pH
- Lys and Arg
Inhibiting absorption -
- phytic acid
- oxalates
- phosphate
- Mg
caffeine
-