Anatomy of a Trichome

Trichomes, those little tiny crystal-like hairs that cover the buds of the cannabis plant, hold all the good stuff. Different methods of hash-making focus on isolating these sticky little parts of the cannabis plant because they house the majority of its resin. Nearly every part of the cannabis plant has at least a little Tetrahydrocannabinol (THC) in it. Leaves have around 4%, while buds have up to 25% or 30% of dry weight. The trichomes cover all parts of the buds, from the interior stems to the surrounding leaves. Scientists used to think that THC and other cannabinoids were made in the green plant tissue and transported out to the trichomes during flowering, but after intensive research, they realised the trichomes themselves make the cannabinoids and terpenes. Trichomes grow off a leaf, around the flower of a female plant, or a bract. A bract houses the seeds in a fertilized plant and has a high density of trichomes. Looking closely, you’ll see different types of these glands, all oozing resin during flowering, but the biggest ones are the capitate stalked trichomes At about 50 to 100 micrometres wide, trichomes are very small. Zoom in close enough (get yourself a portable microscope with LED lights) and you can see the individual cells that make up the structure.

Capitate stalked trichomes have two main parts: the stalk and the gland head

The epidermal cells hold up the mature trichome forming the outside of the stalk and a continuous layer extends over the entire bract surface. The hypodermal cells on the inside of the stalk constantly transport nutrients to the gland head. The basal cell at the top of the stalk holds on to the gland head. As the flower matures, and as mature flowers dry, this connection weakens and gland heads tend to fall off. At the base of the gland head are stipe cells, which hold up the secretory cells, that take the nutrients from the phloem and turn them into precursors for cannabinoid and terpenoid metabolism. The theory is that these precursors get transported to the secretory vesicles above and are converted into cannabinoids and terpenoids once they’re there. As the gland head churns out its product, the resin gets deposited up close to the cuticle (the outer layers of trichome surface). The cuticle thickens, getting richer and richer in oil as flowering progresses. The essential oils, including THC, mostly accumulate on the outer layer of the gland head, but also on the outer layer of the epidermal cells that cover the entire bract, or any trichome-dense area. Resinous THC also accumulates in the fibrillar matrices of the secretory vesicles. Inside these vesicles there is some THC, but also high amounts of terpenoids, which are less viscous. 

adapted from The Anatomy of a Trichome