Mohammed Laher asked:
Cows eat grass and drink water and produce pure, wholesome milk which resides in the body close to the the intestines. Yet the smell does not penetrate the milk. How?
We put this question to biologist Andrew...
Andrew - Well, if we just move back from the question and think about what the intestines have to do. So intestines have to get all the stuff out that grass partially digested into the body but only the bits we want. So they mustnít get out all the bacteria which could be toxic. You donít want to get it into your bloodstream and get septicaemia. You donít want to get any toxins that are on the food. So, your gut really is a very, very clever system that only transport and get what it wants. So, some of that is done by osmosis. So the concentration of different molecules draws the water out and some of it is done actively. So energy tends to pour food out. Of course, you then have the blood system actually, not a tiny gap before you ended up with the other while you make the milk. Of course, the cells there are very carefully putting the right things in that milk, not just anything they come across. So, if you didnít have a good barrier with your intestines, you would be getting really sick over time. So it wouldnít just be going in milk. It would be going everywhere. Actually, if we think about the milk, for the one thing you probably donít think about is you do get infections in others or in people in breasts and you get mastitis. This is a real problem for people with breastfeeding because you got this milk which is very good for growing bacteria. You get this really sore infections and itís really unpleasant for the mother. Of course, the solution today is just antibiotics but you do have to make sure you donít get bacteria in there because they have these horrible side effects.
Kat - And also, there are some bacteria in milk and thatís presumably why we pasteurise it so that we donít get sick from drinking it.
Andrew - Yeah. But they can come in different stage. They can come in through the pumps and stuff like that. What you give to a baby also come from many of the immunities from the mother as well. So, itís a complicated product, milk.
Is what a "fluke of nature"? Is this a question about physiology? Biochemistry? Mammalian evolution? AndroidNeox, Sun, 4th Sep 2016
Milk is produced by the mammary glands.
Different glands in our bodies produce substances as diverse as sweat, insulin, prolactin, saliva, oxytocin, milk, bile, adrenalin, stomach acid, tears, earwax and pituitary hormone, all from the same basic mix of starting materials in the blood.