The calcium in the human body is maintained in a balanced distribution. Explain the calcium distribution and balance under normal conditions.
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Muhammad Soobadar
Calcium is important mineral in the body and serves various functions namely: nerve impulse transmission, muscular contraction, blood coagulation, hormone secretion, and intercellular adhesion . Its level in ECF that we measure is kept within tight range as any disbalance can have profound effect and lead to pathology.
The total amount of calcium in the human body ranges from 1000 to 1200 g. Approximately 99% of body calcium resides in the skeleton; the other 1% is present in the extracellular and intracellular spaces. Total serum calcium consists of ionized, protein bound,and complexed fractions (approximately 48%, 46%, and 7%, respectively).
It is regulated by interplay of intestine ,kidneys and bones all working under effect of hormones to achieve homeostasis. Dietary intake is essential to replenish stores
99% of total ca is stored in bone and small fraction in extracellular 40% of it bound to albumin with 50 % available as ionized calcium and reminder is complexed with anions like biocarbonate and phosphate . Intercellular ca is free found in higher concentration than extra cellular space .
gradient maintained by energy dependent membrane ca Atpase .
intracellular is key of signaling pathway with cells
Serum range 2.1-2.5 from gut and bone .
The total amount of ca+ ranges from 1 to 1.2 kg, 99% of which is in the skeleton. In the serum, the amount is 8.9-10.1 mg/dl (2.2-2.25 mmol/L). In the serum, nearly 48% is ionized, 46% protein bound, and 7% complexed. Daily filtred calcium in a person with normal filtration is about 10 grams. 100-200 mg is excreted in the urine. The absorption from the intestine is influenced by many factors. PTH is a key regulator that increases absorption either directly or indirectly. Vitamin D increases which is activated to 1,25 hydroxy vitamin D, promotes calcium absorption from the intestines as well. In the kidney, around 60-70% of filtered calcium is reabsorbed. 20% is reabsorbed in the TAL-thick portion, 10% in DCT and around 5% n the collecting duct.
under normal conditions: the calcium in the human body is maintained in a balanced distribution.
Total body content of calcium is 1-1.2kg, distributed 99% in bone (as hydroxyapatite, 1% of which is freely exchangable with ECF), 1% in ICF & ECF (where it is present as ionized free form, bound to plasma proteins mainly albumin, complexed as calcium phosphate & citrate, …)
Under normal conditions S.Ca is mentained within normal range due to balance between total intake, GIT absorption & net loss (in feces and urine)
Daily intake ranges 800-1000mg where net 20% (~200mg is absorbed via the GIT mainly through passive paracellular route- tight junction- with direct relation to intestinal surface area and transit time, then excreted via the kidney), 800mg lost in stool.
The kidney is responsible for reabsorption of 99% of filtered Ca, mainly through paracellular route- in PCT& CTALH-, less but significant through active transcellular route- in DCT &CD under control of PTH-.
calcium distribution and balance under normal conditions:
the highest percentile of calcium is located in the bones and calcium balance is regulated by the action of calcium absorption by intestine, reabsorption by the kidneys.
the absorption of calcium intestine it depends the vitamin D and PTH.
Distribution
The total amount of calcium in the human body ranges from 1000 to 1200 g. Approximately 99% of body calcium resides in the skeleton; the other 1% is present in the extracellular and intracellular spaces.
Total serum calcium consists of ionized, protein bound,and complexed fractions (approximately 48%, 46%, and 7%, respectively).
Balance:
Calcium balance is tightly regulated by the concerted action of calcium absorption in the intestine, reabsorption in the kidney, and exchange from bone, which are all under the control of the calciotropic hormones that are released upon a demand for calcium. In healthy adults, approximately 800–1000 mg of calcium should be ingested daily.
When 1 g of calcium is ingested in the diet, approximately 800 mg is excreted in the feces and 200 mg in the urine. Approximately 400 mg of the usual 1000 mg dietary calcium intake is absorbed by the intestine, and calcium loss by way of intestinal secretions is approximately 200 mg/d. Therefore, a net absorption of calcium is approximately 200 mg/d (20%) . Although serum calcium levels can be maintained in the normal range by bone resorption, dietary intake is the only source by which the body can replenish stores of calcium in bone.
Distribution
There is 1.0 – 1.2 Kg of Ca in human body, mainly in the bones (99%),
90% of the remaining is intracellular and 10% is extracellular (in extracellular space and plasma)
the extracellular in turn is 48% ionized, 46% protein bound, and 7% is complexed with other molecules
Balance
To achieve a balance, intake must equals output
Ca is absorbed from intestine via paracellular and transcellular pathways
the absorption in intestine is under VitD3 and PTH control
Ca is freely filtered then most of it is reabsorbed in the proximal tubules, mainly with solvent drag.
in the ascending loop of Henle Ca is reabsorbed via paracellular pathways driven by lumen positivity.
in the distal tubule (where the control of Ca reabsorption occur) Ca undergoes reabsorption via transcellular pathways, controlled by PTH
.99% of the total body calcium is located in bone,
The other 1% is present in the extracellular and intracellular spaces. Approximately 1% of the calcium in the skeleton is freely exchangeable with calcium in the extracellular fluid compartment.
Total serum calcium consists of ionized, protein bound,and complexed fractions (approximately 48%, 46%, and 7%, respectively)
Calcium balance:
Calcium absorption from the intestine.
Calcium reabsorption from the kidneys.
Calcium exchange from the bone, under control of calcitropic hormone like pth vit calcitonin
There are two routes for the absorption of calciumacross the intestinal epithelium: the paracellular pathway (i.e., between the cells) and the transcellular route (i.e., through the cell)
98%–99% of the filtered load ofcalcium is reabsorbed by the renal tubules. Approximately 60%–70% of the filtered calcium is reabsorbed in the proximal convoluted tubule, 20% in the loop of Henle, 10% by the distal convoluted tubule, and 5% by the collecting duct. The terminal nephron, although responsible for the reabsorption of only 5%–10% of the filtered calcium load, is the major site for regulation of calcium excretion
Calcium distribution · The total amount of range from 1000-1200 g: 99% stored in the bone.1% in the extr/intracellular spaces. · 1% of stored calcium are freely exchangeable with the intra/extracellular calcium. Calcium balance 1. Calcium absorption from the intestine. 2. Calcium reabsorption from the kidneys. 3. Calcium exchange from the bone, under influence of calcitropic hormone.
The total amount of calcium in the human body ranges from 1000 to 1200 g. Approximately 99% of body calcium resides in the skeleton; the other 1% is present in the extracellular and intracellular spaces. Although .99% of the total body calcium is located in bone, calcium is a critical cation in both the extracellular and intracellular spaces. Approximately 1% of the calcium in the skeleton is freely exchangeable with calcium in the extracellular fluid compartment. Serum calcium concentration is held in a very narrow range in both spaces. Calcium serves a vital role in nerve impulse transmission, muscular contraction, blood coagulation, hormone secretion, and intercellular adhesion .
Calcium balance is tightly regulated by the concerted action of calcium absorption in the intestine, reabsorption in the kidney, and exchange from bone, which are all under the control of the calciotropic hormones that are released upon a demand for calcium .In healthy adults, approximately 800–1000 mg of calcium should be ingested daily. This amount will vary depending on the amount of dairy product consumed.
When 1 g of calcium is ingested in the diet, approximately 800 mg is excreted in the feces and 200 mg in the urine. Approximately 400 mg of the usual 1000 mg dietary calcium intake is absorbed by the intestine, and calcium loss by way of intestinal secretions is approximately 200 mg/d. Therefore, a net absorption of cal- cium is approximately 200 mg/d (20%) .Although serum calcium levels can be maintained in the normal range by bone resorption, dietary intake is the only source by which the body can replenish stores of calcium in bone.
The Calcium content in the body is about 1000-1200 g, 99%in the bone and 1%in the EC and IC spaces.
The total s. Ca composed of ionized Ca, protein bound and complexed Ca(48%,46%,7%)respectively.
Calcium balance kept through GI absorption as 800-1000mg of calcium ingested daily, 800mg excreted in feces and 200 in urine, the net absorption of calcium is 200mg/day it absorbed exclusively from duodenum, jeujenum and ileum through mainly paracellular(which is depend on dietary calcium and 1,25 vitD) and transcellular pathways.
Renal absorption which is about 60-70% in Proximal tubule from ultrafiltrate(through paracellular transport) , 20%in the loop of henle(paracellular and transcellular pathways) and 10%in distal conveluted tubule (paracellular) and 5%in collecting duct.
Also calcium balance depends also on exchange from bone.
The calcium in the human body is maintained in a balanced distribution. Explain the calcium distribution and balance under normal conditions.
total amount from 1000-1200 g.
99% of body calcium resides in the skeleton and 1% is present outside .
Calcium is absorbed in the upper Part of small intestine. There is 2 pathways that get the Calcium absorbed: passive and active .( paracellular and transcellular )
Calcium Distribution and balance Calcium distribution
The total amount of human body range from 1000-1200 g.
99% stored in the bone.
1% in the extr/intracellular spaces.
1% of stored calcium are freely exchangeable with the intra/extracellular calcium.
Calcium function as
Nerve impulse transmission.
muscular contraction.
Blood coagulation.
Hormone secretion.
Intracellular adhesions.
Calcium balance
Calcium balance is kepted by;
Calcium absorption from the intestine.
Calcium reabsorption from the kidneys.
Calcium exchange from the bone, under influence of calcitropic hormone.
In healthy adult approximately 800-1000 mg should be ingested daily.
For every 1 g absorbed, 800 mg excreted in the faeces, and 200 mg in te urine.
From every 1000 mg ingested in the diet;
400 absorbed by the intestine.
200 mg excreted by the intestine.
The remaining 200 mg will absorbed.
Dietary calcium is the main source for calcium store repletion.
Calcium absorbed exclusively in the deoudenum, jejumun, and ileum.
There are 2 routes for calcium absorbtion;
Paracellular pathway, is the passive pathway so, most of calcium absorbed is this pathway, and dietary calcium laod will be absorbed via this route, and it is indirectly regulated by calcitriol in the tight junction.
Transcellular pathway; minimum amount absorbed via this route, as luminal calcium are usually high.
Calcium is around 99% stored in Bones and 1 % being found in fluids inside the cells and in Extracellular fluids. We consume about 800-1000 mg in Calcium per Day. Most of the Calcium we consume is not absorbed by the Body and instead excreted in our Feces and Urine. Only 20% of Calcium we consume is absorbed and used by the Body.
Gastrointestinal Tract:
Calcium is mainly absorbed in the upper Part of small intestine. There is 2 Way that get the Calcium absorbed: Paracellular and Transcellular (The main way). Calcitriol is the main regulator. Calcitriol induce more expression of Calbindin D9k in enterocyte . The main Factor that influence Calcium absorption is calcium amount -(inverse Relationship).
Calcium lost by feces is approximately 800 mg/day.
Renal
Normal Kidney filter up to 10 g Calcium each day and reabsorb up to 99% of them. Calcium excretion in Urine range between 100-300 mg/day.
Calcium Reabsorption in the proximal convoluted tubule happens mainly through passive diffusion and solvent drag. About 80% of Calcium reabsoption in this segmet of the nephron occurs through passive pathways. The remaining 20% is actively transported through a 2 step process, regulated mainly by parathyroid hormone and calitonin. In the loop of Henle, no calcium is reabsorbed in the thin Segment, but 20% of the filtered calcium is reabsorbed in the thick ascending limb. The bulk of calcium reabsorption in this segment occurs through the paracellular pathway and is proportional to the electrochemical driving force.
Distribution of ionizable calcium accounts for 48% of total blood calcium, while protein binding accounts for 46%, and complexed calcium, such as calcium citrate and calcium phosphate, makes up the remaining 7%.
The skeleton contains 99% of the body’s calcium, whereas the extracellular and intracellular compartments each contain just 1% of the mineral.
Calcium is one of the most important components of the body.
The total quantity of calcium found in a human body might vary anywhere from 1000 mg to 1200 mg or 800 mg to 1200 mg per day.
Gastrointestinal Calcium Absorption:
The combined action of calcium absorption in the gut, reabsorption in the kidney, and exchange from bone are closely controlled by calciotropic hormones produced when calcium is needed. Healthy individuals need 800–1000 mg of calcium daily. This depends on dairy consumption.
800 mg in stools and 200 mg in urine. The gut absorbs 400 mg of the typical 1000 mg of dietary calcium, whereas intestinal secretions lose 200 mg/d. Hence, calcium absorption nets 200 mg/d (20%).
Renal Regulation :
Humans with a GFR of 170 liters per 24 hours filter 10 g of calcium each day. The renal tubules resorb 98%–99% of the filtered calcium load because the urine excretes 100–200 mg each day. The proximal convoluted tubule resorbs 60%–70% of filtered calcium, the loop of Henle 20%, the distal 10%, and the collecting duct 5%. The terminal nephron regulates calcium excretion even though it reabsorbs just 5–10% of the filtered calcium burden.
CALCIUM one of the essential element in body
Total amount of ca , in the human body ranges from 1000mg -1200mg
RDA 800- 1200 mg /d
Distribution :- total serum calcium consists of ionizable 48% , protein bound 46% complexed fractio 7% such as ca citrate and ca phosphate
.
99% of body calcium resides in the skeleton and 1% is present in the extracellular and intracellular spaces Function of ca. not only skeleton formation but essential in neve conductivity . neuromuscular transmission , hormones and enzymes activity and blood clotting GIT absorption of ca . via tow pathways
1- paracellular pathway >>>passive
2- intracellular pathway>>active the regulation of absorption affected by calcitriol which mainly control active transport Renal regulation of calcium balance
In human who have a GFR 170 liters per 24h roughly 10g of ca is filtered per day the amount of ca. excreted in the urine usually rang from 100mg t0 200mg /d Hence 98% -99% of filtered ca. is reabsorbed by renal tubules
1-) 60-70% of filtered ca reabsorbed in proximal convoluted tubule
passively paracellular 80% of ca. reabsorbed in PCT and about 10-15% active reabsorbed regulated by PTH and Calcitonin
2-) 20% in loop of Henle ( TAL) through both transcellular and paracellular routes
But the bulk of ca reabsorption through paracellular pathway affected by electrochemical driving force
### also calcium transport in TAL influenced by calcium sensing receptor ( CaSR )
10% by distal convoluted tubule actively transports divided into 3 step of influx , the diffusion and extruded
5%by collecting duct
Calcium is important mineral in the body and serves various functions namely: nerve impulse transmission, muscular contraction, blood coagulation, hormone secretion, and intercellular adhesion . Its level in ECF that we measure is kept within tight range as any disbalance can have profound effect and lead to pathology.
The total amount of calcium in the human body ranges from 1000 to 1200 g. Approximately 99% of body calcium resides in the skeleton; the other 1% is present in the extracellular and intracellular spaces.
Total serum calcium consists of ionized, protein bound,and complexed fractions (approximately 48%, 46%, and 7%, respectively).
It is regulated by interplay of intestine ,kidneys and bones all working under effect of hormones to achieve homeostasis. Dietary intake is essential to replenish stores
99% of total ca is stored in bone and small fraction in extracellular 40% of it bound to albumin with 50 % available as ionized calcium and reminder is complexed with anions like biocarbonate and phosphate . Intercellular ca is free found in higher concentration than extra cellular space .
gradient maintained by energy dependent membrane ca Atpase .
intracellular is key of signaling pathway with cells
Serum range 2.1-2.5 from gut and bone .
The total amount of ca+ ranges from 1 to 1.2 kg, 99% of which is in the skeleton. In the serum, the amount is 8.9-10.1 mg/dl (2.2-2.25 mmol/L). In the serum, nearly 48% is ionized, 46% protein bound, and 7% complexed. Daily filtred calcium in a person with normal filtration is about 10 grams. 100-200 mg is excreted in the urine. The absorption from the intestine is influenced by many factors. PTH is a key regulator that increases absorption either directly or indirectly. Vitamin D increases which is activated to 1,25 hydroxy vitamin D, promotes calcium absorption from the intestines as well. In the kidney, around 60-70% of filtered calcium is reabsorbed. 20% is reabsorbed in the TAL-thick portion, 10% in DCT and around 5% n the collecting duct.
under normal conditions: the calcium in the human body is maintained in a balanced distribution.
calcium distribution and balance under normal conditions:
the highest percentile of calcium is located in the bones and calcium balance is regulated by the action of calcium absorption by intestine, reabsorption by the kidneys.
the absorption of calcium intestine it depends the vitamin D and PTH.
Distribution
The total amount of calcium in the human body ranges from 1000 to 1200 g. Approximately 99% of body calcium resides in the skeleton; the other 1% is present in the extracellular and intracellular spaces.
Total serum calcium consists of ionized, protein bound,and complexed fractions (approximately 48%, 46%, and 7%, respectively).
Balance:
Calcium balance is tightly regulated by the concerted action of calcium absorption in the intestine, reabsorption in the kidney, and exchange from bone, which are all under the control of the calciotropic hormones that are released upon a demand for calcium. In healthy adults, approximately 800–1000 mg of calcium should be ingested daily.
When 1 g of calcium is ingested in the diet, approximately 800 mg is excreted in the feces and 200 mg in the urine. Approximately 400 mg of the usual 1000 mg dietary calcium intake is absorbed by the intestine, and calcium loss by way of intestinal secretions is approximately 200 mg/d. Therefore, a net absorption of calcium is approximately 200 mg/d (20%) . Although serum calcium levels can be maintained in the normal range by bone resorption, dietary intake is the only source by which the body can replenish stores of calcium in bone.
Distribution
There is 1.0 – 1.2 Kg of Ca in human body, mainly in the bones (99%),
90% of the remaining is intracellular and 10% is extracellular (in extracellular space and plasma)
the extracellular in turn is 48% ionized, 46% protein bound, and 7% is complexed with other molecules
Balance
To achieve a balance, intake must equals output
Ca is absorbed from intestine via paracellular and transcellular pathways
the absorption in intestine is under VitD3 and PTH control
Ca is freely filtered then most of it is reabsorbed in the proximal tubules, mainly with solvent drag.
in the ascending loop of Henle Ca is reabsorbed via paracellular pathways driven by lumen positivity.
in the distal tubule (where the control of Ca reabsorption occur) Ca undergoes reabsorption via transcellular pathways, controlled by PTH
Calcium distribution:
Calcium balance:
Calcium distribution:
Total serum calcium consists of :
Calcium balance:
Under control of calciotropic hormone in different body parts:
Ca absorption in the intestine.
Depend on the length of the bowel segment & the transient time the food bolus.
Routes of the absorption:
*Paracellular:
passive
the predominant route of absorption
indirectly influenced by calcitriol (increased permeability of tight junction).
*Transcellular:
active
calcitriol is the main regulatory factor (increased synthesis of calbindin).
Reabsorption in the kidney
Exchange from bone: ~ 1% of Ca in the skeleton is freely exchangeable with the Ca in the ECF compartment.
Calcium distribution
· The total amount of range from 1000-1200 g: 99% stored in the bone.1% in the extr/intracellular spaces.
· 1% of stored calcium are freely exchangeable with the intra/extracellular calcium.
Calcium balance
1. Calcium absorption from the intestine.
2. Calcium reabsorption from the kidneys.
3. Calcium exchange from the bone, under influence of calcitropic hormone.
The total amount of calcium in the human body ranges from 1000 to 1200 g. Approximately 99% of body calcium resides in the skeleton; the other 1% is present in the extracellular and intracellular spaces. Although .99% of the total body calcium is located in bone, calcium is a critical cation in both the extracellular and intracellular spaces. Approximately 1% of the calcium in the skeleton is freely exchangeable with calcium in the extracellular fluid compartment. Serum calcium concentration is held in a very narrow range in both spaces. Calcium serves a vital role in nerve impulse transmission, muscular contraction, blood coagulation, hormone secretion, and intercellular adhesion .
Calcium balance is tightly regulated by the concerted action of calcium absorption in the intestine, reabsorption in the kidney, and exchange from bone, which are all under the control of the calciotropic hormones that are released upon a demand for calcium .In healthy adults, approximately 800–1000 mg of calcium should be ingested daily. This amount will vary depending on the amount of dairy product consumed.
When 1 g of calcium is ingested in the diet, approximately 800 mg is excreted in the feces and 200 mg in the urine. Approximately 400 mg of the usual 1000 mg dietary calcium intake is absorbed by the intestine, and calcium loss by way of intestinal secretions is approximately 200 mg/d. Therefore, a net absorption of cal- cium is approximately 200 mg/d (20%) .Although serum calcium levels can be maintained in the normal range by bone resorption, dietary intake is the only source by which the body can replenish stores of calcium in bone.
The calcium distribution in the body:
The total amount of range from 1000-1200 g. 99% stored in the bone.
1% in the extr/intracellular spaces.
1% of stored calcium are freely exchangeable with the intra/extracellular calcium.
Calcium balance in normal individual
Calcium absorption from the intestine.
Calcium reabsorption from the kidneys.
Calcium exchange from the bone, under control of calcitropic hormone like pth vit calcitonin
The Calcium content in the body is about 1000-1200 g, 99%in the bone and 1%in the EC and IC spaces.
The total s. Ca composed of ionized Ca, protein bound and complexed Ca(48%,46%,7%)respectively.
Calcium balance kept through GI absorption as 800-1000mg of calcium ingested daily, 800mg excreted in feces and 200 in urine, the net absorption of calcium is 200mg/day it absorbed exclusively from duodenum, jeujenum and ileum through mainly paracellular(which is depend on dietary calcium and 1,25 vitD) and transcellular pathways.
Renal absorption which is about 60-70% in Proximal tubule from ultrafiltrate(through paracellular transport) , 20%in the loop of henle(paracellular and transcellular pathways) and 10%in distal conveluted tubule (paracellular) and 5%in collecting duct.
Also calcium balance depends also on exchange from bone.
The calcium in the human body is maintained in a balanced distribution. Explain the calcium distribution and balance under normal conditions.
Calcium Distribution and balance
Calcium distribution
Calcium balance
Calcium is around 99% stored in Bones and 1 % being found in fluids inside the cells and in Extracellular fluids. We consume about 800-1000 mg in Calcium per Day. Most of the Calcium we consume is not absorbed by the Body and instead excreted in our Feces and Urine. Only 20% of Calcium we consume is absorbed and used by the Body.
Gastrointestinal Tract:
Calcium is mainly absorbed in the upper Part of small intestine. There is 2 Way that get the Calcium absorbed: Paracellular and Transcellular (The main way). Calcitriol is the main regulator. Calcitriol induce more expression of Calbindin D9k in enterocyte . The main Factor that influence Calcium absorption is calcium amount -(inverse Relationship).
Calcium lost by feces is approximately 800 mg/day.
Renal
Normal Kidney filter up to 10 g Calcium each day and reabsorb up to 99% of them. Calcium excretion in Urine range between 100-300 mg/day.
Calcium Reabsorption in the proximal convoluted tubule happens mainly through passive diffusion and solvent drag. About 80% of Calcium reabsoption in this segmet of the nephron occurs through passive pathways. The remaining 20% is actively transported through a 2 step process, regulated mainly by parathyroid hormone and calitonin. In the loop of Henle, no calcium is reabsorbed in the thin Segment, but 20% of the filtered calcium is reabsorbed in the thick ascending limb. The bulk of calcium reabsorption in this segment occurs through the paracellular pathway and is proportional to the electrochemical driving force.
Distribution of ionizable calcium accounts for 48% of total blood calcium, while protein binding accounts for 46%, and complexed calcium, such as calcium citrate and calcium phosphate, makes up the remaining 7%.
The skeleton contains 99% of the body’s calcium, whereas the extracellular and intracellular compartments each contain just 1% of the mineral.
Calcium is one of the most important components of the body.
The total quantity of calcium found in a human body might vary anywhere from 1000 mg to 1200 mg or 800 mg to 1200 mg per day.
Gastrointestinal Calcium Absorption:
The combined action of calcium absorption in the gut, reabsorption in the kidney, and exchange from bone are closely controlled by calciotropic hormones produced when calcium is needed. Healthy individuals need 800–1000 mg of calcium daily. This depends on dairy consumption.
800 mg in stools and 200 mg in urine. The gut absorbs 400 mg of the typical 1000 mg of dietary calcium, whereas intestinal secretions lose 200 mg/d. Hence, calcium absorption nets 200 mg/d (20%).
Renal Regulation :
Humans with a GFR of 170 liters per 24 hours filter 10 g of calcium each day. The renal tubules resorb 98%–99% of the filtered calcium load because the urine excretes 100–200 mg each day. The proximal convoluted tubule resorbs 60%–70% of filtered calcium, the loop of Henle 20%, the distal 10%, and the collecting duct 5%. The terminal nephron regulates calcium excretion even though it reabsorbs just 5–10% of the filtered calcium burden.
The calcium in the human body is maintained in a balanced distribution. Explain the calcium distribution and balance under normal conditions.
CALCIUM one of the essential element in body
Total amount of ca , in the human body ranges from 1000mg -1200mg
RDA 800- 1200 mg /d
Distribution :- total serum calcium consists of ionizable 48% , protein bound 46% complexed fractio 7% such as ca citrate and ca phosphate
.
99% of body calcium resides in the skeleton and 1% is present in the extracellular and intracellular spaces
Function of ca. not only skeleton formation but essential in neve conductivity . neuromuscular transmission , hormones and enzymes activity and blood clotting
GIT absorption of ca . via tow pathways
1- paracellular pathway >>>passive
2- intracellular pathway>>active the regulation of absorption affected by calcitriol which mainly control active transport
Renal regulation of calcium balance
In human who have a GFR 170 liters per 24h roughly 10g of ca is filtered per day the amount of ca. excreted in the urine usually rang from 100mg t0 200mg /d
Hence 98% -99% of filtered ca. is reabsorbed by renal tubules
1-) 60-70% of filtered ca reabsorbed in proximal convoluted tubule
passively paracellular 80% of ca. reabsorbed in PCT and about 10-15% active reabsorbed regulated by PTH and Calcitonin
2-) 20% in loop of Henle ( TAL) through both transcellular and paracellular routes
But the bulk of ca reabsorption through paracellular pathway affected by electrochemical driving force
### also calcium transport in TAL influenced by calcium sensing receptor ( CaSR )
10% by distal convoluted tubule actively transports divided into 3 step of influx , the diffusion and extruded
5%by collecting duct
The calcium in the human body is maintained in a balanced distribution. Explain the calcium distribution and balance under normal conditions.