Define about the paracellular route - calcium, Biology

Assignment Help:

Define about the Paracellular Route - Calcium?

It involves passive Ca transport through the tight junctions between mucosal cells. The salient features include:

  • It is independent of nutritional and physiological regulation.
  • It is concentration-dependent and occurs when there is an increased intake or a person is taking supplements.
  • It occurs throughout the small intestine, ileum being the important site.

Thus, we can say that most Ca absorption takes place in the small intestine. There is some evidence, which suggests that not more than 4% (8 mg) of dietary Ca is absorbed by the colon per day. The unabsorbed component which appears in the faeces together with the unabsorbed component of digestive juice calcium is known as endogenous faecal calcium. The faeces, therefore, contain unabsorbed dietary calcium and digestive juice calcium that was not reabsorbed. True absorbed calcium is the total amount of calcium absorbed from the calcium pool in the intestines and therefore contains both dietary and digestive juice components.

Net absorbed calcium is the difference between dietary calcium and, faecal calcium and is numerically the same as true absorbed calcium minus endogenous faecal calcium. At zero calcium intake, all the faecal calcium is endogenous and represents the digestive juice calcium which has not been reabsorbed; net absorbed calcium at this intake is therefore negative to the extent of about 200 mg (5 mmol). When the intake reaches about 200mg (5 mmol), dietary and faecal calcium becomes equal and net absorbed calcium is zero. As calcium intake increases, net absorbed calcium also increases, steeply at first but then, as the active transport becomes saturated, more slowly until the slope of absorbed or ingested calcium approaches linearity with an ultimate gradient of about 5 -10%. True absorption is an inverse function of calcium intake, falling from some 70 % at very low intakes to about 35% at high intakes. There are several factors which influence the amount of calcium absorbed through the intestine. These factors can thus be related to the bioavailability of calcium. The subsequent discussion will look at these factors in detail. But first we shall look at the excretion of unabsorbed calcium.


Related Discussions:- Define about the paracellular route - calcium

Determine the toe corticospinal interneuron, Which of the following is true...

Which of the following is true for a toe corticospinal interneuron that produces action potentials during movements of the big toe of the left foot? A. A portion of its axon is

Perceptual disorders, Perceptual Disorders The procedure actually const...

Perceptual Disorders The procedure actually constitute a sub-battery and include tests of the subject's ability to recognise shapes by touch and identifies numbers written on t

Adaptations, Adaptations Every organism can live and reproduce within a...

Adaptations Every organism can live and reproduce within a certain range of climatic conditions. Organisms that live in hot or cold environments have behavioural and physiologi

What are the functions of fibers, Of which substance do elastic fibers of t...

Of which substance do elastic fibers of the connective tissue are made? What are some functions of these fibers? The elastic fibers are made of a protein called elastin. Ela

What is the meaning of chelicifore, What is the meaning of Chelicifore? ...

What is the meaning of Chelicifore? These feeding mouthparts are found on most, pycnogonads. Though the proboscis is the main feeding structure in these animals when chelicifor

Bioclimatology effect of climate on distribution of organism, Bioclimatolog...

Bioclimatology: This is the study of effect of climate on distribution of organisms. Bioclimatology is the inter-disciplinary field of science which studies the interactions betwe

Metalimnion - summer stratification, Metalimnion - Summer Stratification ...

Metalimnion - Summer Stratification This zone lies below the epilimnion and above the hypolimnion and thus forms the intermediate layer which is non-circulating. The metalimni

How do calcium ions participate in muscle contraction, How do calcium ions ...

How do calcium ions participate in muscle contraction? Why do both muscle contraction and muscle relaxation spend energy? In the muscle cells calcium ions are kept within the s

Describe fourth heart sound in details, Describe Fourth Heart Sound in deta...

Describe Fourth Heart Sound in details? S 4 is generated during the atrial-filling phase. It is a low frequency event. LVS, is best heard over apex. Mechanism of S 4 generat

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd