Mushroom Anatomy & Physiology - The structure and function of a mushroom

Mushroom Anatomy & Physiology - The structure and function of a mushroom

Mushrooms are the “fruiting bodies” produced by certain types of fungi during their reproductive phase. Of the approximately 144,000 distinct species of fungus science has identified, about 14,000 of those produce mushrooms, and that may be less than 10 percent of the total number. Mushrooms come in many different sizes and shapes, but their basic anatomy and physiological function is similar for all of them.

Mushrooms Anatomy - An Overview

Mushrooms are the part of the fungus that helps them spread their reproductive spores around. We’ll go through the basic anatomy of a mushroom, top to bottom, before discussing its physiology and life cycle.

Mushroom Parts


The cap (also called a Pileus) is the often umbrella-shaped top of the mushroom. This familiar shape has an important purpose; to protect the delicate spores from rain and sun while they are developing.


The underside of the cap is usually lined with gills (also known as lamellae), thin ribbed membranes radiating out from the center. These gills produce incredible numbers of spores and hold onto them until they are ready to be released.

Some mushrooms do not have gills, but instead have ridges, toothlike structures, or spongelike pores. Despite their appearance, the purpose of these structures is much the same as gills.


The stem (also known as a stipe) is the long plantlike stalk holding up the cap. These can vary widely in length and girth, but the purpose is the same. The stem lifts the spore-producing part of the mushroom up out of the ground to aid with spore dispersal.


The annulus is a fleshy ring around the stalk in many mushrooms. This part is the remnant of a protective partial veil that covers spore-producing gills until the end of their development. As the mushroom cap unfurls and the stalk grows, this veil is torn away to expose the spore-filled gill structure.


The volva is a cup-like structure found at the bottom of many gilled mushrooms. This part of the mushroom is the remnant of an early protective structure called a universal veil which protects mushrooms early in their development. As the mushroom grows vertically, it ruptures this universal veil, leaving behind the volva and some patchy markings on the cap.


The mycelium is the largely unseen part of the mushroom, a dense network of interconnected filaments called hyphae that absorb moisture and nutrients from their surroundings. Mycelial networks grow and expand until they have thoroughly colonized their environment, at which point they grow mushrooms to spread their spores to new environments.

Mushrooms Physiology


For the purposes of reproduction, it can be helpful to think of mushrooms as the “fruit” of the fungus, which would make spores the “seeds” of the fungus. Spores are microscopic reproductive cells capable of forming a new mushroom by themselves, as most mushrooms are capable of reproducing asexually.

Mushrooms can produce trillions of spores under the right conditions, and have evolved to disperse them by a vast range of methods, whether by wind or water or with the unwitting help of insects and other creatures. Some mushrooms even eject spores out in a dusty cloud when something bumps into them!


When a spore finds fertile ground where it can begin growing, it starts sending out tiny strands of filamentous hyphae, similar in some ways to a plant’s root system. But where roots absorb simple nutrients using the movement of water through their cell walls, hyphae excrete enzymes which break down complex organic chemicals into more simple compounds. This process is vital to the decomposition of living things and the soil cycle, making nutrients available for new life.


As hyphae grow and expand, they intersect with each other and create a dense network of nutrient absorption called a mycelium. Mycelia can connect with other mycelia, and many types of fungus form symbiotic relationships with trees and other living things, allowing for the transfer of water, nutrients and information throughout a complex ecological web that connects many species over vast distances.


When a mycelium has fully colonized an area, it may create mushrooms to spread its spores to new areas. Hyphae at the outer edge of the mycelium will form into tiny balls called primordia. These primordia soon become less ball-shaped and elongate into pins These pins will be the beginnings of the mushroom caps. Depending on the species and local conditions, this process may take anywhere from days to a couple of weeks.


Fruiting is the phase where the mushroom grows into its familiar form. Over the course of 5-12 days, the emerging mushroom grows up and out, and as the stalk grows, the cap first breaks free from the universal veil, and finally from the partial veil, revealing the spores on the underside of the cap.


Among the many thousands of mushroom species you will find a fantastic variety of shapes, sizes and colors. But their anatomy and physiology all have quite a bit in common, and it’s important to know about this fascinating fungal family that plays such an important role in the web of life.