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Of our total iron intake,

  • About 10 % to 15 % comes from meat, fish, and poultry as heme
  • About 85 % to 90% comes from grains and vegetables as non-heme iron

Absorption of heme iron

Most of the iron from digested food is absorbed through the duodenal villi.

Heme iron is moved across the cell membrane into the cytoplasm by facilitated transport through heme transporters.

(From SlideShare)

Proteolytic enzymes in the cytosol release the #"Fe"^"2+"# ions, which enter a common pool with non-heme iron.

Absorption of non-heme iron

To be absorbed, non-heme iron must be in the #"Fe"^"2+"# form. Any iron in the #"Fe"^"3+"# form is first reduced to #"Fe"^"2+"# by a ferric reductase.

Intestinal absorption
(From ResearchGate)

A protein called divalent metal transporter 1 (DMT1) then transports the iron into the cell through the cell membrane.

The cell can then either

  • store the #"Fe"^"2+"# by complexing it as ferritin or
  • release the #"Fe"^"2+"# into the body via the iron exporter, ferroportin

The enzyme hephaestin helps ferroportin transfer iron across the cell wall.

The #"Fe"^"2+"# ions are again oxidized to #"Fe"^"3+"# and bound to plasma transferrin for transport throughout the body.


Open-heart surgery is any type of surgery where the chest is cut open and surgery is performed on the muscles, valves, or arteries of the heart.


Yes, doctors temporarily stop the heart to perform surgery on it. They place the patient on a heart-lung bypass machine, to stop the blood from flowing to the heart. This automatically stops pumping action of heart muscles.

How is open-heart surgery performed?

  1. The patient is given general anesthesia. This will make sure the patient is asleep and pain-free.

  2. The surgeon makes an 8- to 10-inch cut in the chest.

  3. The surgeon cuts through all or part of the patient’s breastbone to expose the heart.

  4. Once the heart is visible, the patient may be connected to a heart-lung bypass machine. The machine moves blood away from the heart so that the surgeon can operate.

  5. The surgeon performs the required procedure like attaching a graft vessel to bypass a blocked artery in heart wall, or replacing a heart valve, etc.

  6. The surgeon allows blood to flow back in heart after the procedure; closes the breastbone with wire.

  7. The cut is stitched up.

What are some of the risks to open heart surgery?

There are a lot of risks in a open heart surgery. Making it one of the most deadliest surgerys to perform.

Some common risks are,

  • Heart Attack/ Stroke
  • Chest Pain or low fever
  • Chest wound infection



Here's my understanding of the mechanism.


Hydrochloric acid is produced by the parietal cells in the stomach.


These cells secrete about 60 mL #"HCl"# per hour at a concentration of
roughly 0.16 mol/L.

This is about #3 × 10^6# times the concentration of #"H"^"+"# ions in blood.

Thus, the secretion of hydrochloric acid depends on active transport.

The key player is a proton pump #bb((1)"# located in the cell membrane.

The dissociation of water within the cell generates #"H"^"+"# and #"OH"^"-"# ions.

The #"OH"^"-"# ions combine with #"CO"_2# to form #"HCO"_3^"-"# and are transported out of the cell by anion exchange for #"Cl"^"-"color(white)(l)bb((2))# .

The #"Cl"^"-"# ions are transported out of the cell by conductance channels #bb((3))#.

The proton pump removes #"H"^"+"# ions from the cell in exchange for #"K"^"+"# ions. This effectively recycles the #"K"^"+"# ions.

The net effect is that one #"H"^"+"# ion and one #"Cl"^"-"# ion leave the cell for each water molecule that dissociates.


About half a minute....


Once you swallow Alcohol (Ethanol, and preferably in an alcoholic drink of some sorts) it arrives in your stomach. As it is a standard, small metabolite it doesn't need digestion and passes the stomach lining, to be taken up in the bloodstream straight away.

The RATE at which this occurs varies for everybody and depends on a lot of physiological factors: amount of alcohol ingested at first swallow, nature of alcoholic drink, gender, condition of the stomach-lining, contents of the stomach (food), current blood-composition, presence of prescribed drugs, body weight, etc.

As the heart pumps our total volume of blood around in approx. 1 minute, it will take roughly about 30 seconds for the first molecules of alcohol to pass the Brain-Blood Barrier and affect the Neurons.

The satisfaction of that first sip isn't due to Alcohol, though: it has more to do with our built-in Reward System.

The effect of alcohol is negligible at first of course due to the low concentration, but with the passing of minutes it becomes more and more noticeable: In 2009 a research group from the University of Heidelberg reported a noticeable effect within 6 minutes:


The strength of the effect depends on the type of beverage:

This graph represents the alcohol concentration in Blood of course, but as stated, it reaches the brain straight away from there....

Myopia is defined as a refractive error,where parallel light rays coming from infinity,after getting refracted meets in front of the neurosensory layer of retina with accommodation at rest.


But it is not necessary that a myopic eye has to be bigger in size.

Basically,myopia can result from the following cases,

1 . AXIAL MYOPIA : This a condition where the eye ball is larger in size due to faulty (limitless) growth during the development,as a result normal visual axis of #24 mm# is increased and after refraction light falls in front of retina.

2 . CURVATURAL MYOPIA : This is a condition where,corneal curvature is increased than normal(i.e radius of curvature is decreased),as a result,refractive power of cornea increases and light rays meet,infront of retina.

3 . POSITIONAL MYOPIA : This is a condition where,the lens is abnormally placed infront of its normal location,as a result focal point is found in front of the retina.

4 . INDEX MYOPIA : This happens in old age(associated with cataract),when the refractive index of lens increases,resulting in increased power of lens,so that light rays meet infront of fovea.

Now,the above classification is etiological classification,there is another clinical classification as well,which has three subtypes,

A . Congenital Myopia

B . Developmental Myopia

C . Pathological or degenerative Myopia

Some important Symptoms are :

  1. Blurring of vision

  2. Asthenopic symptoms

  3. Half closed eyes in order to allow parallel light rays passing only.(basis of pin hole test)

Some important signs are:

  1. Deep anterior chamber

  2. Papillary Crescent formation surrounding the optic disc

  3. Foster Fuchs spot(due to stretching of choroid as occurs due to retinal enlargement results in subretinal hemorrhage)

the last two are found with the help of fundoscopy.

Treatment :

OPTICAL : Using concave lens in glass or contact lens,once the power is adapted properly.


SURGICAL : Using Photorefractive Keratotomy, LASIK (LASER in situ Keratomileusis)

Surgical correction of myopia is very popular now a days than optical correction.

Hope this will help you!

Well nasal cavity has got a lot of roles to perform,but I am not going to discuss all of them in details,here,as you wanted I am just mentioning two major roles only.

1 . It acts as the passage between the external nasal openings and the internal nares, through which air passes to the trachea via the pharynx. During this passage, entry of dust particles and microorganism is prevented by means of nasal hairs present in the vestibule of nose and also by MUCOCILIARY BARRIER of nasal cavity.

2 . Nasal cavity contains several bipolar olfactory cells on the roof and the adjoining areas of nasal cavity, which helps in olfaction i.e smell.

I am just giving you few word about what other roles the nasal cavity serves.

A .The nasolacrimal duct opens in the inferior meatus of nasal cavity, which drains tear fluid from lacrimal sac

B . It contains opening of different para nasal air sinuses,during inspiration air enters into them which acts as resonating chambers.

C . It also has some role in moistening the air entering into the trachea, specially in dry weather, as dry air is harmful for our body.


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