Doctor Joshua’s Physiology 101 lesson

Tonsils are not actually glands, it’s a common misconception. Tonsils are lymphatic tissue, like lymph nodes. Another very common misconception is that lymph nodes are glands (”swollen glands”) - when in fact they are not. The thyroid is a gland, the pancreas is a gland, even the skin is a gland (in fact, the skin is the biggest gland in the human body) - but lymph nodes and tonsils are not.

Glands are organs that produce some hormone or other substance that they supply to other parts of the body. There are two main types of glands:

1. Endocrine glands produce hormones that are transported by blood to other parts of the body, transmitting a “signal” for other tissues to act upon. Example: The thyroid gland

2. Exocrine glands have ducts, through which they excrete their product into the outside world (even the passages of the digestive system are effectively outside the human body even though they definitely seem to be located on the inside for any practical purposes of daily life)
Example: salivary glands

Additionally, two other ways exist for transmitting such signals:

3. Paracrine: the signaling substances affect the neighboring cells within the same organ
4. Autocrine: a cell is producing signals affecting itself, i.e. within the same cell

That’s it for Physiology 101 for today..