Salivary glands

Why this matters

Saliva is the fluid every impression, restoration, radiograph and periodontal measurement is made in, and a salivary gland is the only exocrine organ you can inspect, palpate and watch the output of at a routine check-up. Three doors on the mucosa, one gland you can milk, one lip that is the standard biopsy site for an autoimmune disease.

The big picture

One design, repeated at every scale. A secretory end-piece makes an almost isotonic fluid, a duct chain strips salt out of it without letting water follow, and a contractile basket holds the whole thing in shape. Change the mix of cells in the end-piece and the length of the duct chain and you have every salivary gland in the head, major and minor.

The 15 cards in this lesson

1. 01A salivary gland is an end-piece, a duct chain and a myoepithelial basket — and the list of glands is not closed
2. 02Calibre increases downstream and the epithelium changes with it — that is the whole map
3. 03Four cues identify a serous or mucous end-piece, and the fixative made two of them
4. 04The demilune argument: one rat paper with no stated sample size, and a critique published where nobody could see it
5. 05Three major glands, and the evidence behind each claim is not the same strength
6. 06The stripes are folded membrane with mitochondria wedged between the folds, not fibres
7. 07Sparse is not absent — and the one human duct dataset has typographically corrupt dispersions
8. 08Myoepithelial cells hold the gland in shape; the one direct experiment says they do not squeeze it empty
9. 09Two limbs, three knockouts: the water follows chloride, and the protein comes out of granules
10. 10Minor glands are about 8% of the volume and carry four times the parotid's sIgA concentration
11. 11The mouth is not one fluid compartment, and the site gradient is far steeper than the stimulation effect
12. 12The resting-saliva percentages only fit inside 100% at the very bottom of their own quoted range
13. 13A bud that branched, canalised and was then innervated — and the acinus maintains itself by copying itself
14. 14Clinical alert — in the lesson
15. 15Clinical alert — in the lesson

You have got it when

You can (1) name end-piece, intercalated duct, striated duct and excretory duct and say what each does; (2) read serous, mucous and seromucous off an H and E slide by four cues in order, and name the two the fixative made; (3) say what the evidence for and against the serous demilune shows; (4) say what myoepithelial cells do and what the one direct experiment says they do not; and (5) separate the salivary…