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.
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.