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

Formation of aqueous humour, Formation of Aqueous  Humour It  is  unive...

Formation of Aqueous  Humour It  is  universally accepted that the aqueous  is  produced  by  the  ciliary processes. Although a great deal of  research has been done on the fo

What is root cap, What is root cap? Root cap is a protective structure ...

What is root cap? Root cap is a protective structure located in the tip of the growing root. It defends the meristematic tissue of the root forming a cap that surrounds the tip

What are the chemical bonds of the dna molecule, Q. What are the chemical b...

Q. What are the chemical bonds of the DNA molecule that are broken for replication process to occur? During the DNA replication process, hydrogen bonds between the nitrogen- co

Types of retaining structure, What are the types of evaluation of lateral e...

What are the types of evaluation of lateral earth forces acting on retaining structures? This section seeks to introduce you to the evaluation of lateral earth forces acting on

Determine balanced diet for celiac disease, Determine Balanced Diet For Cel...

Determine Balanced Diet For Celiac Disease? Energy: initially the children are seen to be malnourished, thus 100-120 Kcal/kg body weight/day with gradual increase to 150 Kcal

Two biotic factors could affect an antelope, What two biotic factors could ...

What two biotic factors could affect an antelope living in the Serengeti? The biotic factors that may affect an antelope living in the Serengeti could be:predation by carnivore

Define synthesis of hormones - vitamin c, Define Synthesis of Hormones - Vi...

Define Synthesis of Hormones - Vitamin C? Ascorbate is involved in the amidation, thereby conferring stability to hormones such as thyrotropin releasing hormone, adrenocorticot

State in brief about the zinc, State in brief about the Zinc    It is c...

State in brief about the Zinc    It is concerned with the functioning of sulphydryl compounds, such as cysteine, in regulation of redox potential within the cell. Zinc is somet

Find the electric potential, (a) Find the electric potential, taking zero a...

(a) Find the electric potential, taking zero at infinity, at the upper right corner (the corner without a charge) of the rectangle in the figure. (Let y = 3.7 cm and x = 6.7 cm.)

Inorganic and organic substances, Q. Living beings are made of inorganic an...

Q. Living beings are made of inorganic and organic substances. According to the molecular complexity how can each of those substances be classified? Inorganic substances, mole

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