Introduction to the Integumentary System

Functions of the WHOLE Integumentary System

Before we dive into any organ system in this class, it is important to learn the system’s overall functions. What does this system bring to all the other systems in the body?  You can see this list of 7 things here, take a moment to read them. I’m not going to explain each one on this slide. Each of these overall functions is addressed in the minilectures on the integumentary systemThe body system that includes the skin, hair, nails, and associated glands.. After you’ve viewed all the minilectures, return to this slide. Then, ask yourself which anatomical structures contribute to these overall functions. 

Layers of the Cutaneous Membrane

Before we go any further, it’s important to review those levels of organizationThe structured arrangement of biological systems. from Chapter 1.  We said that the body is made up of the 11 organ systemsGroups of organs that work together to perform functions., the integumentary system being one of them.  Recall that organ systems are made up of organs. The skinThe body’s largest organ, providing protection and regulation., also called the cutaneous membrane, is one of those organs.  Students often get confused here and think that the term integumentary system equals skin.  The integumentary system is skin, hair, nailsHard, keratinized structures that protect the fingertips and enhance fine motor skills., sweat glands, and other associated organs.  That being said, the skin, or the cutaneous membrane is the organ on which we will spend the most time.

The cutaneous membrane consists of 2 or 3 layers, depending on who you ask.  The epidermisThe outermost layer of the skin, made of stratified squamous epithelium., known as the hard candy shell, covers all superficialNear the surface of the body. surfaces of the body. The dermisThe thick inner layer of the skin that contains blood vessels, nerves, and connective tissue. acts like a gelatinous body stocking.  The hypodermisThe layer beneath the dermis, composed of connective and adipose tissue, providing insulation and cu, made of adipose tissue (fat), is not present everywhere. For example, it is absent on the posterior face of your hands and the superiorAbove or toward the upper part of the body. face of your feet.  And so, some people don’t consider the hypodermis to be an official layer of the cutaneous membrane. 

Tissues of the Cutaneous Membrane

You might be looking at this slide thinking that I have a duplicate but I do not. The layers of the cutaneous membrane include the epidermis, dermis, and possibly hypodermis. These are specific to the cutaneous membrane, which is why they get the name layer. This slide is about the tissues that are found in those layers. You have to remember that there are only 4 tissues in the human body. They are epithelial, connective tissue, muscular tissue, and nervous tissue. 

Within these categories there are finite subcategories which we are continually addressing in the lab portion of our class. The epidermis is open to the outside. Therefore, it is made of an epithelial tissue because it lines in open space. The tissue is called stratified squamous epithelial tissue. That name stratified squamous can be used in many places in the body. This occurs where there is more than one layer of egg-shaped cellsThe basic structural and functional units of life.. Here we can apply a more specific name to these stratified squamous epithelial cells and we can call them keratinocytesThe most abundant cells in the epidermis, responsible for producing keratin..

This is because they contain a lot of the fibrous protein keratinA strong, fibrous protein that forms the structure of skin, hair, and nails. which is a waterproofing protein.  The dermis actually has two layers both of which are connective tissue. The more superficial layer of the dermis contains areolar connective tissue. The deeper, larger layer of the dermis contains dense irregular connective tissue. It is worthwhile to dig into chapter 5 and revisit our lab where we addressed these tissues. As you may have guessed the hypodermis is composed of adipose fat which is also a connective tissue.

Be very careful on the quiz. Read each question carefully. Note whether they are asking you for the layer or the tissue.

The Rule of Nines

Let’s first address the degree of burns and how they relate to the layers of the cutaneous membrane.  I have suffered some pretty severe sunburns in my lifetime. Having Scandinavian heritage, I am pasty white. I burn to a crisp when the sun hits my skin. A little burn that you might get from the sun is considered a first degree burn. A little burn from touching your finger to the hot part of the toaster is also a first degree burn. They damage only the epidermis. They don’t require medical attention. The epidermis is constantly regenerating itself and will heal in time. Second degree burns are so named because they reach down into the dermis. This is significant because there are two places in the dermis where there are blood vessels.  Blood vessels are necessary if you want to see any healing to the burn.  To make new cells, you need glucoseA simple sugar that is the main source of energy for cells. and oxygen. These elements provide the energyThe capacity to do work or cause change. required to do it. 

A very light second degree burn will burn away the more superficial network of blood vessels. This type of burn still has the ability to regenerate. The deeper network of blood vessels is still present. A deepAway from the surface of the body. second degree burn would burn the dermis completely removing all of the blood vessels in the area. Most tissue of the dermis is capable of regenerating if the burn does not extend over a large surface area. This regeneration requires enough time. A third degree burn is also called a full thickness burn. It burns the full thickness of the cutaneous membrane. It removes the epidermis, dermis, and the hypodermis if present.

The rule of ninesA method used to estimate the percentage of body surface area affected by burns. is used in assessing burn victims.  This rule takes the proportion of skin in an area and designates a percentage of coverage.  Real Quick: Face is 9%.  Arms are 9% each.  Legs are 18% each.  Trunk of body is 18% and the left over 1% is the genitals. Think for a moment about taking someone’s skin off and spreading it out on a table.  Now put all the pieces together like a puzzle to make a shape you can measure.  By doing this, you are able to think of what percent of the organ, of skin, has been damaged.  In adults, if the front of the lower limb is burned, it covers roughly 9% of the skin.   Think about other organs…could you lose 9% of your heart? Kidney? Liver?  Most consider things critical when 25% or more of the skin surface has suffered a full-thickness burnAnother term for a third-degree burn, affecting all skin layers and possibly deeper tissues..  So….a leg and an arm.  Burns on the face put you in critical condition. So do burns on the posterior face of the hands. Burns on the superior face of the feet also indicate a critical condition.   Hmmmm….those correspond to the areas that don’t have that hypodermis layer.