The Integumentary System
When we first started our series on the Human Body, we started with the skeletal system which serves as the structural frame that supports the entire body. From there we have looked a numerous systems as if we were building a human body on the skeleton. Today we will look at the system that holds everything together on the skeletons – the Integumentary System.
Surprisingly, many people have never heard of the Integumentary system or that it contains the largest organ in the human body.
The Integumentary system consists of the covering of tissue that holds everything in and protects it from the outside environment, namely the skin, hair and nails.
I. Hair – Hair grows from the hair follicles in our skin and it consists of three basic layers:
A. Medulla – The medulla is the inner most layer of a hair and is also referred to as the pith or marrow of the hair. The medulla is composed of several rows of cells. Naturally blonde hair, as well as some other thin hairs, lack a medulla. The coarser the hair, the more rows of cells can be found in the medulla.
B. Cortex – The cortex is the middle layer of a hair and makes up over 80% of the total weight of the hair. It is composed of long narrow cells which contain fibrous proteins. Melanin pigments which determine the color of the hair are found in the cortex. The strength and elasticity of a hair is maintained by the cortex.
C. Cuticle – The cuticle is the outer layer of a hair. It is composed of a single layer of transparent cells that overlap each other much like the shingles on a roof. It serves to protect the cortex layer beneath it. The cuticle layer is directly affected by the pH of whatever it comes in contact with. A high pH (alkaline solution such as many soaps and shampoos) makes the cuticle layers expand, which will allow fluids to infiltrate into the cortex. Lower pH (acidic solutions) cause the cuticle layer to contract and harden, preventing anything from infiltrating into the cortex.
II. Nails – The human body has nails on the end of the fingers and toes. They are a hardened layer of protein called keratin that grows out from the skin at the base of the nail. The main function of the nails is to protect the nerve rich tips of the fingers and toes. Most people look at their nails and think of just the cuticle and the hardened nail itself, but there is much more to the nail than just those two parts.
A. Germinal Matrix – The germinal matrix is the layer of tissue underneath the nail bed. It produces the cells that become the nail bed.
1. Lunula – At the base of the nail can be seen a white crescent shape feature knows as the lunula. This is the visible part of the germinal matrix.
B. Nail Bed – The nail bed is a layer of skin that lies on top of the germinal layer and directly below the nail plate. This layer of skin moves forward as the nail grows out. The nail bed often becomes thinner with age. As it thins, the small ridges will appear on the nail, running the length of the nail. These ridges are caused by the matrix crests below with are what connect the two layers of the skin to each other.
C. Nail Plate – The nail plate, also known as the nail body, is the hardened plate that covers the top tip of the fingers and toes. Basically, this is the part that some people put polish on. It is composed of layers of dead cells that flatten and harden into the nail as we know it. The nail plate is fairly translucent and appears pink because of the tissue and capillaries beneath it.
D. Nail Root – The nail root is the part of the nail that is set in the skin at the base of the nail. It is formed by the matrix layer immediately below it.
E. Nail Sinus – The term sinus generally means cavity or hollow. In this case, it refers to the cavity in which the nail root sets in to.
F. Eponychium – The eponychium is a thin layer of epithelium cells that runs across the top of the base of the nail plate. Most people refer to it as the cuticle. It forms a protective seal at the base of the nail plate as well as laying down a thin protective layer of dead cells on the top of the nail plate as it grows out.
G. Distal Edge – The distal edge, also known as the free margin, is the outer tip of the nail plate. This is the part of the nail that you actually clip.
H. Hyponychium – The hyponychium is the layer of skin immediately below the distal edge of the nail and is more commonly referred to as the quick.
I. Nail Groove – The nail groove is the groove along both sides of the nail plate.
III. Skin – if you ask most people what the largest organ in the human body is, you will get answers that include the lungs, liver, intestines, etc. However, to their amazement, the skin is actually the larges organ in the human body. The skin consists of three layers:
A. Epidermis – The epidermis is the outer layer of skin. The cells of the epidermis contain a large amount of keratin, the same protein that forms the hair and nails. This makes the epidermis tougher and more durable than most other tissues in the body. The epidermis layer is thickest (~0.06 inches) at the soles of the feet and palms of the hands, and thinnest (~0.002 inches) at the eyelids. The epidermis also contains three types of specialized cells:
1. Melanocytes – Melanocytes are cells that contain the pigment melanin which determine a person’s skin color. The more melanin in a person’s melanocytes, the darker their skin tone and the lesser amount of melanin results in a lighter skin tone.
2. Langerhans Cells – Langerhans cells, first discovered in 1868, are involved with the immune system and fighting pathogens on the surface of the skin.
3. Merkel Cells – Merkel cells are a oval shaped sensory cells that function with the recognition of light touch, shapes and textures.
The epidermis is divided in to 5 layers:
4. Stratum Basale – The stratum basale is the lowest layer of the epidermis. It is composed of a single layer of basophilic cells.
5. Stratum Spinosum – The stratum spinosum is the second layer of the dermis. It is composed of the spinosum layer with consists of prickle cells. Prickle cells form intercellular connections making skin stronger. They also produce keratin.
6. Stratum Granulosum – The stratum granulosum is the middle layer of the epidermis. The cells of this layer contain granules that can be easily seen under a microscope.
7. Stratum Lucidum – The stratum lucidum is a very thin layer of translucent dead cells. It is only present in thicker areas of the epidermis. This layer helps reduce frictional and shear forces between the stratum lucidum and stratum corneum to help prevent tearing of the skin.
8. Stratum Corneum – The stratum corneum is the outer most layer of the epidermis and composed of dead flat cells that arise from the stratum granulosum and stratum lucidum. The dead cells are held together by a type of glue. The stratum corneum serves as the first layer of defense and protection from pathogens, insects, toxic substances, excessive water loss and many other things that could cause the body harm. If you’ve ever heard of the saying, ‘beauty is only skin deep’, realize that our outer beauty is nothing more than a layer of dead cells.
B. Dermis – The dermis is the middle layer of the skin. The dermis contains collagen and elastin fibers that help strengthen the skin and keep it elastic and pliable. Unlike the epidermis, the dermis contains blood vessels. These blood vessels dilate and constrict in conjunction with the outside temperatures the body is exposed to. The dermis is divided into two layers:
1. Reticular – The reticular layer is the lower and thicker layer of the dermis. It is characterized by thick collagen fibers.
2. Papillary – The papillary layer is the upper and thinner layer of the dermis and is characterized by a narrower arrangement of collagen fibers.
C. Subcutaneous Tissue – Also known as the hypodermis or hypoderm or superficial fascia, the subcutaneous tissue is the lowest layer of the skin. This layer contains larger blood vessels and nerves than those found in the dermis. It is characterized by the loose connective tissue and quantities of fat that is stored here.
The Integumentary system, like so many of the other systems in the human body is complex and many faceted. And when you put all of these systems together it forms one of the most amazingly designed bodies in all of creation.
The human body could not survive without all of these systems in place and functioning. And yet evolutionists want you to believe that all of this is a mere product of random chance mutations that occurred over time. The disordered became ordered. The simple became complex. Life arose from non-life. Information and intelligence arose from nothingness.
Every one of these facets of evolution defy the very laws of science that all scientists profess to believe in. And evolutionists call biblical creationism a blind faith. I don’t know about you, but when look at the complexity of the human body; I see the wondrous works of an omniscient Designer who created man in His own image.
Then God said, “Let us make man in our image, after our likeness. And let them have dominion over the fish of the sea and over the birds of the heavens and over the livestock and over all the earth and over every creeping thing that creeps on the earth.” So God created man in his own image, in the image of God he created him; male and female he created them. Genesis 1:26-27
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