Context: A new study has suggested that the responses to the SARS-CoV-2 virus in the nose and throat might help determine who will develop severe disease.

Key Finding of the study:

  • SARS-CoV-2, like other respiratory coronaviruses, enters through the mouth or nose.
  • Initially replicates within the epithelial cells of the human nasopharynx region generating an upper respiratory infection over several days.
    • The respiratory epithelium is the tissue that lines the respiratory tract.
  • Failed nasal epithelial anti-viral immunity may underlie and precede severe COVID-19.
  • Why some people get more sick than others has been one of the most puzzling aspects of this virus from the beginning.
    • Everyone with severe COVID-19 had a blunted interferon response early on in their epithelial cells, and were never able to ramp up a defense.
  • Despite equivalent viral loads, in people with mild or moderate COVID-19, the epithelial cells express anti-viral/interferon-responsive genes, whereas the cells in patients with severe COVID-19 have muted anti-viral responses.

Related Facts

Types of Muscle Tissue:

  • Skeletal muscle – the specialised tissue that is attached to bones and allows movement.
  • Smooth muscle – located in various internal structures including the digestive tract, uterus and blood vessels such as arteries. 
  • Cardiac muscle – the muscle specific to the heart.

Facial muscle tissue:

  • The facial muscles are a group of striated skeletal muscles supplied by the facial nerve (cranial nerve VII) that, among other things, control facial expression. 
  • These muscles are also called mimetic muscles.