Back To CourseMCAT Prep: Help and Review
89 chapters | 942 lessons
As a member, you'll also get unlimited access to over 70,000 lessons in math, English, science, history, and more. Plus, get practice tests, quizzes, and personalized coaching to help you succeed.Free 5-day trial
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.
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.
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?
Insects, spiders, crustaceans, and many parasites, like tapeworms, have gonadopores, or reproductive pores, on the outside of their body. In males, this pore forms the ejaculatory duct, or the passageway that sperm exits the body, whereas in females, it is the oviduct, or the passageway from the ovaries to the outside of the body.
Gastropods, like terrestrial snails and slugs, have little breathing pores, called pneumostomes, which they use to draw air into their single lung for oxygen intake.
Some pores are used to sense the environment, such as the little pores that dot the nose of a shark, called ampullae of Lorenzini, that allow them to sense temperature gradients as well as electrical impulses, such as the muscle contractions of prey swimming nearby. The lateral line is a similar organ, formed by a series of pores that enable fish to sense vibration and movement in their watery environment.
Cells have both passive channels, such as those used in the process of osmosis and diffusion, and active channels, which require energy to actively transport ions or water across the plasma membrane.
Yup, that's right, even plants and rocks have pores! Plants have little pores along their leaves and stems, called stomata, that they use to draw air in for use in photosynthesis and respiration. They then release their metabolic wastes (oxygen and water) back through the pores and out into the environment.
Porous mediums, such as rocks, ceramics, and cement, as well as things like wood and bone, all have little pores or tiny spaces that air and water may pass through. Some of these, such as those used as building materials, require some form of sealing from the elements to protect them from degrading over time.
Pores are tiny little openings in the exterior surface of an organism's skin or a structure. In mammals and birds, pores take the form sweat ducts, hair follicles, and lactiferous ducts in mammals and preen glands in birds. While these pores tend to be secretory, not all function in this way.
Pores fill a variety of specialized functions, such as:
Cells have their own system of pores that may either be passive (as in the case of osmosis and diffusion channels) or active (such as ion and water channels). Materials, such as wood, cement, brick, rocks, and bone are also considered porous, as they have many tiny spaces within their structural matrix through which water and air can pass.
To unlock this lesson you must be a Study.com Member.
Create your account
Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.
To learn more, visit our Earning Credit Page
Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.
Back To CourseMCAT Prep: Help and Review
89 chapters | 942 lessons