Question Corner

Drinking hot liquid

QUESTION:Why is it that we are able to drink very hot liquid but the same burns our skin if poured on the body?

R.Srinivasan, Hosur

ANSWER :Physiologically, alimentary canal (gastrointestinal tract) is lined with mucous layer. Mucous contains mucin protein and water. Mucous is secreted by mucous glands present on the epithelium. Mucous, is present not only inside the alimentary canal, but also lines the respiratory and urinogenital tracts. This mucous lining primarily acts as a protective barrier and protects the underlying living cells from pathogens and from other physical and chemical hazards.

When we drink very hot liquid this mucous lining protects the living cells beneath it from getting burnt. This happens mainly due to liquid water molecules in mucous. Water molecules have high enthapy (E) and boiling point. This property of water molecules in mucous enables it to act as a heat absorbent and prevent the penetration of heat beneath it.

Our skin is also involved in protection of underlying tisues and organs from external environmental hazards. Skin is composed of a superficial layer (the epidermis) and a deeper layer (the dermis). Dermis consists of living cells while, epidermis consists of many cell layers and most of the layers are made up of satiated, denucleated, keratinized dead cells. These layers act as physical barriers against the invasion of pathogens and harmful substances. But these stratified layers are not as effective as the mucous in the heat production mechanism. Because, these layers are dry in nature and contain no water molecules to absorb heat, and are permeable, when hot substances are poured on the skin, the dry horny layers manage to give little protection to the living cells from the heat.

R.Muhuntan, Coimbatore, T.N

Cause of cyclone

QUESTION: The East Coast is more often affected than the West Coast due to low pressure from Bay of Bengal. Why is it so? Does geographical area of the sea has anything to do with this?

S.Devarajan, Madurai,T.N

ANSWER:Predominantly low pressure disturbances or cyclones develop all around the world between latitude 10 degrees to 15 degrees north and between latitude 10 degrees to 15 degrees South, initially move westwards and recurve towards the poles. They require long sea travel to intensify. Sea surface temperature should be around 27.5 degrees centigrade, ocean currents and sun's position count for satisfying these conditions.

After the establishment of SW-monsoon all over the country, the disturbances form over the head Bay and do not have sufficient sea travel to strengthen. Cyclones are rare during this period.

During October, November and first half of December, south Arabian Sea has cold waters running north to south and the South Bay warm with cross equatorial flow bringing warm water across the equator. Moreover remnants of typhoons moving westwards across the Gulf of Thailand into the Andaman sea concentrate into cyclones.

The Orissa cyclone (October 29, 1999) initially moved into north Andaman Sea as a marginal cyclone from lower Burma (Myanmar) and intensified into a super cyclone before striking Paradip.

In November, severe cyclones that cut across the south peninsula from Bay to Arabian sea as a depression reconcentrate as a cyclone in the Arabian Sea. One such cyclone, crossing Tamil Nadu south of Nagapattinam, emerged into the Arabian sea, reconcentrated as a cyclone, moved a 1000 km towards the Arabian peninsula, took an anticlockwise loop turn, to return and strike Mangalore (November 22, 1977).On an average for every six disturbances in Bay one disturbance occurs in the Arabian sea. Geographical area of the ocean alone does not count for the genesis of cyclones.

C.Ranganathan,Trichy, T.N.

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