That irresistible urge to sneeze . . . . We have all been in social situations where it would be best if we didn’t. Pinch our noses. Press under our noses. Hold our breath. But no, the sneeze is an irresistible force.
Sneezing is a poorly understood mechanism - a response to irritation in the nasal passages. Physiological mechanisms that are poorly understood often receive complex names; doctors call sneezing sternutation.
It is known that patients with sinusitis or cystic fibrosis - both diseases which affect the respiratory tract - have problems clearing their noses as a result of sneezing. Some American researchers decided to study this on humans and mice.
They blew a standardised puff of air onto the mucous lining of the nose, and recorded the response of the nose lining to this stimulus. In patients with sinusitis and cystic fibrosis, the nose lining responded much less to this stimulation
The nose is lined with a kind of moving carpet made of one of the key specialised cells to learn for Science GCSE: ciliated epithelial cells. [“Epithelium” is the word used for thin linings in the body made up of a layer or a few layers of cells;] “ciliated” means there are lots of small ‘hairs’, or cilia. In the nose, these clear foreign matter from the respiratory tract by sweeping it up to the back of the throat, where it can be swallowed and fall into the acid bath of the stomach.
Think of this lining as a microscopic version of a continuously active shag pile carpet. This moving carpet, normally idling in first gear, switched into overdrive in the study and stayed in that active state for a couple of minutes. In patients with sinusitis and cystic fibrosis this response was much less marked.
The researchers repeated their experiments outside the body to examine the biochemistry behind the response. They grew small sheets of mucosal cells taken from their subjects and demonstrated that these sheets showed the same response in vitro (in the laboratory; literally ‘in glass’) as in vivo (‘in life’, or in this case in the noses of the subjects). The study identified that the diseased patients had an atypical response of biochemical energy stores (ATP) in the ciliated epithelial cells of the nose lining. This may lead to the development of novel therapies for sinusitis and cystic fibrosis.
But have you ever seen a whale sneeze? This clip shows a whale sneezing when a small fire is lit in its mouth and the smoke irritates it. But it is from the Walt Disney film "Pinocchio."
In fact, whales are voluntary breathers. That is, they are very aware of when they take a breath so that they do not accidentally breathe in while underwater. Humans, and all land based mammals, are involuntary breathers: most of the time, you are not aware of when you are breathing.
In whales, the respiratory tract (blowhole/nostril to lungs) is entirely separate from the alimentary tract (mouth to gut). This allows a whale to swim with its mouth open underwater collecting krill without getting water into its lungs. Land mammals have a crossroads in these two systems: in the pharynx, the space at the back of your mouth where you see your uvula (the dingle dangle), air can enter the lungs from either the mouth or the nose and, accidentally, food can get into your nose or your larynx. Those who are that way inclined can take advantage of this crossroads to perform the feat of snorting apple juice, milk and other liquids out of their nostrils – I don’t recommend doing this at home, at least not when your parents are watching!
This is a clip of a whale sneezing; well, the tourist got too close. You can also take a look at the original paper or this related article in National Geographic.
Would you like more Biology explained, or a private tutor? Why not book a lesson with Maths and Science tutor Tony D? Feel free to visit his profile page on Tutorfair’s website.