Posted in Psychology & Medicine

Viscera: Thyroid

(Learn more about the organs of the human bodies in other posts in the Viscera series here:

There lies a small, butterfly-shaped organ called the thyroid gland in your neck, just in front of your windpipe above the clavicles. The thyroid may not seem important given its small size, but it has the important function of controlling the body’s rate of metabolism. Metabolism is a group of chemical reactions your body relies on to function as a lifeform. Chemicals such as glucose are processed by various enzymes – biological catalysts that encourage chemical reactions – and converted in to fuel (such as ATP) that cells can use for numerous bodily functions. The thyroid produces the thyroid hormones, thyroxine and triiodothyronine, to fine-tune the rate at which these reactions occur.


To see the function of the thyroid gland, we can look at two types of diseases: hyperthyroidism and hypothyroidism.

In hyperthyroidism, the thyroid is overactive and produces too much thyroxine. This causes the body’s metabolic rate to speed up, causing increased heart rate, weight loss, sweating, tremors and sensitivity to heat. Depending on the cause, the eyes may be affected as well, causing them to protrude forwards, giving a rather scary appearance. This disease may happen for various reasons, but the most common cause is Grave’s disease, where antibodies lock on to receptors in the thyroid to stimulate thyroxine production, much like a stuck key on a keyboard.


Hypothyroidism is the direct opposite syndrome caused by an underactive thyroid. This causes a reduction in metabolic rate, leading to weight gain, tiredness (due to lack of energy), slow heart rate and cold intolerance. It can also be caused by an autoimmune disorder (called Hashimoto’s thyroiditis), or more commonly due to iodine deficiency, as the thyroid uses up iodine to produce thyroid hormones.

Both diseases may cause the thyroid to grow to an abnormal size, which is called goitre (seen as a large neck lump). The treatment is usually adjusting the total level of thyroid hormone produced by removing parts of or all of the thyroid, or replacing thyroid hormone if needed via medication.


Because the thyroid uses iodine to make hormones, thyroid diseases such as thyroid cancer can be treated using an interesting method. If you inject radioactive iodine into the patient, it will make its way to the thyroid gland, which actively collects the iodine from the blood. Overactive thyroid tissue (such as in Grave’s or thyroid cancer) take up iodine at a faster rate. The iodine then delivers a focussed dose of radiation to the thyroid, leaving the other tissues in the body unharmed. This method is used for both first-line treatment of hyperthyroidism and to clean-up remaining cancer cells after thyroid surgery.


Posted in Psychology & Medicine

Cranial Nerves

Nerves can be divided broadly as spinal nerves and cranial nerves: the latter which is directly from the brain. There are 12 pairs of cranial nerves:

  1. CN IOlfactory nerve (smell)
  2. CN IIOptic nerve (sight)
  3. CN IIIOculomotor nerve (eye movements, control of pupil and lens)
  4. CN IVTrochlear nerve (eye movements)
  5. CN VTrigeminal nerve (sensory information from face and mouth, chewing)
  6. CN VIAbducens nerve (eye movements)
  7. CN VIIFacial nerve (taste, tear and salivary glands secretion, facial expressions)
  8. CN VIIIVestibulocochlear nerve (hearing and sense of balance)
  9. CN IXGlossopharyngeal nerve (taste, swallowing, parotid gland secretion, sensory information from oral cavity, information about blood)
  10. CN XVagus nerve (sensory and motor signals to and from many internal organs, glands and muscles)
  11. CN XIAccessory nerve (movement of SCM and trapezius, which are neck/shoulder muscles)
  12. CN XIIHypoglossal nerve (tongue movements)

As there are so many nerves and the names are all varied, there is a simple (yet very obscene) mnemonic to help medical students remember the names and order of nerves:

Oh, Oh, Oh, To Touch And Feel Virgin Girls’ Vaginas And Hymens
Oh, Oh, Oh, To Touch And Feel A Girl’s Very Soft Hands
(where vestibulocochlear -> auditory)

It is also worth noting the mnemonic for the types of nerves is:

Some Say Marry Money, But My Brother Says Big Boobs Matter More

Perhaps the only way to survive medical school is through humour.