Accessory structures to the integumentary system include things like hair, nails, and sweat glands.

Hair

Our hair no longer functions the way fur does. Fur is used to keep animals warm but human hair is way too thin for that. Even though our hair is mostly vestigial, it still has many uses. 

-The hair on our head protects us from sunburns

-The hair in our noses protects us from dust, insects, and other invaders

-The hair in our ears keeps things out and vibrates with sound

-The hair on your skin helps with sensation

Nails

Nails are also made of keratin. 

The nail body forms on what is called the nail bed.

Many animals have claws that serve different purposes. Our nails are not used as claws. One function of our nails is to protect the tips of our fingers and toes.

One of the main purposes of our nails is to give our fingertips backing to press our sensory cells against while picking up small/fine objects. This backing provides us with heightened sensitivity allowing humans to do fine/precise tasks.

Student Activity:

Try squeezing a pencil between your fingers on the first part of the digits that does not have a nail. Squeeze the pencil, move it around. Then squeeze it between your fingertips. You will notice how much more sensitive you are to gripping things between your fingertips. This is due to the nails providing a hard backing to press your sensory cells against.

Class discussion:

Why do we get wrinkly when we have been in water for a long period of time?

Does our whole body, all of our skin get wrinkly, when sitting in water for a long time?

Only our hands and feet get wrinkly when sitting in water for an extended amount of time. Many people refer to it as "pruney".

Our body does this so we will have better grip when in water. When your hands become pruney they have better grip to grab things like fish or other wet and slippery objects. Pruney feet also give you better grip on slippery things like wet rocks.

Sweat Glands

Sweat glands are very important for homeostasis. They help with thermoregulation or temperature control.

The human body needs to stay 98 degrees Fahrenheit. When our temperature begins to drop from 98 degrees, it burns calories and heats our self up. We are little furnaces burning calories all the time. If the temperature drops too much our muscles start to shiver which causes more calorie burn and an increase in heat production.

In many ways it is easier to warm up than it is to cool off. Just think about winter vs summer. On a cold day you can just wear a jacket. You can add more layers if it is really cold. But when it is a very hot day, there is only so many layers of cloths you can take off. You can wear shorts and a tank top, but what if that isnt enough? It is hard to stay cool.

Sweat is our bodies best way to cool off. It is vital that we stay 98 degrees. If we go over 98 degrees that is heatstroke. Sweat works by coating the outside of our skin and as the skin heats the sweat it evaporates off our body and as the sweat evaporates it takes the heat with it. Most of the time sweat can effectively prevent heatstroke. 

Sweat glands are known as Sudoriferous glands.

There are two types of sudoriferous sweat glands

-Eccrine

-Apocrine

Eccrine sweat glands

-Eccrine sweat glands are found all over the surface of the skin. These are the glands that secrete the normal sweat for thermoregulation. They are found all over the body but are most abundant on the palms of the hand, the soles of the feet, and the forehead.

-The sweat from eccrine glands is mostly made of water and salt. It does also contain a small amount of antibodies, trace amounts of metabolic waste, and dermacidin (an antimicrobial peptide).

Apocrine sweat glands

The apocrine sweat glands are located in the armpits and genital regions. These glands are larger and deeper. They empty the sweat directly into the hair follicle of these densely haired areas. The sweat secreted from the apocrine sweat glands contains water and salt like the eccrine glands but it also contains organic compounds that make the sweat thicker. These organic compounds are broken down by bacteria which creates a smell. This is why the armpits and genital regions develop a smell with the sweat.

It is thought that the purpose of the apocrine sweat glands has to do with the not understood, human pheromone response. 

Hormones are chemical messages within the body. We send hormones throughout the body to communicate.Unlike hormones, Pheromones are messages that are meant for outside the body. Pheromones are a chemical message that animals use to send signals to each other. For example, when ants walk they leave a pheromone trail on the ground. When the antennae of the other ants touch the pheromone it sends a message to their brain that says to keep walking in that direction. Another example is when a female cat is in heat (ovulating and ready to reproduce) she emits a pheromone scent that attracts male cats.

As far as we know, the human pheromone system is vestigial and does not work. We cannot find any working receptors in our olfactory (sense of smell) that respond to pheromones. So it is thought that the heavy sweat from the apocrine glands use to play a role in pheromones in our ancestors. 

This heavy sweat is why armpits and genitals develop a smell.

Sebaceous Glands

Sebaceous glands are not sweat glands but are oil glands. These glands are found all over the body. They secrete a lipid oil that helps lubricate the body and waterproof the skin and hair. They excrete an oil called sebum. This oil helps keep our skin from drying out. It prevents water loss. Also because it is a hydrophobic lipid it creates a water proof layer over our body. 

Modern humans tend to wash off our skin oil often which makes us run the risk of having dry skin.

Sebaceous glands are controlled by hormones that do not develop in the body until puberty. 

Student Research:

Most of us do not like body odor. You should now understand why you develop body odor in your armpits. But do you fully understand the measures we go through to prevent it? Some of us use deodorant and some of us use antiperspirant. 

In pairs, take 15 minutes to search and answer these questions.

1) What is the difference between deodorant and antiperspirant?

2) How does a deodorant work?

3) How does an aluminum based antiperspirant work?

4) Is an aluminum based antiperspirant bad for you?

5) What are some alternative deodorants and antiperspirants

When you are done, we will discuss the answers as a class