What Are Pores? - Definition & Function

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  • 0:00 What Is a Pore?
  • 0:42 Mammal and Bird Skin
  • 2:40 Feeding, Ambulatory,…
  • 4:26 Respiratory, Sensory,…
  • 5:18 Plants & Porous Mediums
  • 5:59 Lesson Summary
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Lesson Transcript
Instructor: Sarah Phenix
In this lesson, we'll explore what pores are as well as the many unexpected functions that they serve. You'll learn that humans aren't the only organisms with pores. Sponges, insects, rocks, and fish all have some form of this much underappreciated little structure.

What Is a Pore?

I'm sure you quite familiar with the idea of what a pore is. After all, everyone, at one time or another, has dealt with the annoyance of a clogged pore resulting in a pimple, but did you know that pores aren't exclusive to humans?

The term 'pore' is really just a general reference to any tiny opening in the skin or surface of an organism or structure, which means that most everything has some form of a pore. Plants, animals, humans, and even rocks have pores, but they don't all function in the same way. So, let's take a moment to explore some of the varied functions that pores can serve.

Mammal & Bird Skin

Let's start off by looking at the pores that everyone is familiar with, the pores of our skin. Mammals (like humans, cats, dogs, monkeys, etc.) all have two types of pores that exist in various proportions, depending on the species. Sweat ducts are pores that excrete sweat, while hair follicles are pores that body hairs pass through.

Your sweat glands are essentially a biological A/C system, responsible for cooling our bodies by secreting watery sweat, which evaporates in the air and cools our skin. Our hair follicles, on the other hand, are the pores that hairs grow in, as well as the opening that allows them to protrude from our skin. Did you know that hair follicles are also the very same pores used by oil producing sebaceous glands? I know that, more often than not, people blame these little pores for blemishes and pimples, but they actually serve a really important purpose - they moisturize your skin as well as offer a level of water repellency via the oily secretions. This is why areas like your face (that have many fine hairs) as well as the hair on your head get so greasy when not washed. Each hair follicle has its own sebaceous gland attached to it. These glands are analogous to a birds preen glands, which secrete oils that they disperse throughout their feathers when they preen, giving them the water-proofing quality with which we are so familiar.

Lactiferous ducts, or lactating ducts, are another type of specialized skin pore that all mammals (referring to organisms with mammary glands, or milk producing glands) have, which secrete milk to feed their young. Men have lactiferous ducts as well, however, they are underdeveloped, and they lack the necessary hormones in the appropriate quantities to actually produce and secrete milk.

Feeding, Ambulatory, & Reproductive Pores

Sponges have little water intake pores, called ostia, that they use to draw water into their tissue for feeding. Once the water enters through these pores, it passes into either little canals, called radial canals, or into a main cavity, called the spongocoel, where little filtering cells sit. These filtering cells snatch little organic particulate out of the water. Sponges are such amazing natural water purifiers that they can filter up to 20,000 times their own volume in water.

Starfish, sea urchin, and sea cucumbers all belong to a group of organisms called echinoderms. Echino means spiny and derms refers to the skin. These creatures utilize a water intake pore, called a madreporite, that they use to flood a series of internal tubules which provide them with a hydrostatic (meaning a fluid-balanced) skeleton. Did you know that this is actually how they move their little tube feet? They flood their hydrostatic skeleton, filling little canals running the length of their bodies as well as their hundreds of tube feet, with water that they then swing in an ambulatory (walking) motion via muscle contractions. Pretty cool, huh?

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