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

Biotechnology, How does bisulfite sequencing work ?

How does bisulfite sequencing work ?

What are the major structures within the cell nucleus, Within the cell nucl...

Within the cell nucleus the major structures are: the nucleolus, an optically dense region, spherical shaped, where there are concentrated ribosomal RNA (rRNA) associated to protei

How b and t cells recognize antigen are true explain, Which of the followin...

Which of the following statements about how B and T cells recognize antigen are true? a. B cells only recognize antigen presented by class I or class II MHC molecules. b. Both cell

Nervous system control of blood pressure, Q. Nervous System control of bloo...

Q. Nervous System control of blood pressure? Most nervous controls are achieved via involuntary reflex arcs involving pressoreceptors, the vasomotor centers of the medulla, and

Function of adenosine in consciousness, Q. Function of Adenosine in conscio...

Q. Function of Adenosine in consciousness? The adenosine plays a major role in inducing sleep. Injections of adenosine promote sleep and decrease wakefulness. Conversely, adeno

Define about oxygen molecule, How many pairs of electrons do the two oxygen...

How many pairs of electrons do the two oxygen atoms in an oxygen molecule share with each  other? Explain your answer. The oxygen atoms share two pairs of electrons, sinc

Name the molecules make active transport through membranes, Which are the m...

Which are the molecules that make possible active transport through membranes? Active transport is made by exact membrane proteins. These proteins are called "pumps" because

A healthy potted pitcher plant, A healthy potted pitcher plant when kept in...

A healthy potted pitcher plant when kept in a green house with favourable conditions of light, temperature, soil and water showed poor growth although there was no infection. Give

Investigation of aortic regurgitation by serial testing, Q. Investigation o...

Q. Investigation of aortic regurgitation by Serial Testing? Serial testing is indicated in asymptomatic patients with severe AR and preserved LV function since LV dysfunction m

What is phellogen, What is phellogen? What is its function? Phellogen, ...

What is phellogen? What is its function? Phellogen, also called as cork cambium, is the meristematic plant tissue responsible for the formation of the periderm (the covering of

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