Where is the stratum spinosum

There are more species of insects than any other species combined. This surely illustrates that insects have the selecti.. Genes are the blueprint of our bodies, a blueprint that creates a variety of proteins essential to any organism's surviv.. Freshwater ecosystem is comprised of four major constituents, namely elements and compounds, plants, consumers, and deco.. Physiology is the study of how living organisms function. Thus, human physiology deals specifically with the physiologic..

This tutorial recognizes the importance of food as a source of energy that will fuel many biological processes. A good d.. Skip to content Main Navigation Search. Dictionary Articles Tutorials Biology Forum. The deepest layer of the skin is called the subcutaneous layer, the subcutis, or the hypodermis.

Like the dermis, the layer contains blood vessels and nerves for much the same reasons. Importantly, the subcutis contains a layer of fat. This layer of fat works alongside the blood vessels to maintain an appropriate body temperature. The layer of fat here acts as a cushion against physical trauma to internal organs, muscles, and bones.

Additionally, the body will turn to this fat in times of starvation to provide power to its various processes, especially brain function.

Layers of cutaneous membranes skin : This image details features of the epidermal and dermal layers of the skin. The epidermis includes five main layers: the stratum corneum, stratum lucidium, stratum granulosum, stratum spinosum, and stratum germinativum. The epidermis is the outermost layer of our skin. It is the layer we see with our eyes. It contains no blood supply of its own—which is why you can shave your skin and not cause any bleeding despite losing many cells in the process.

The epidermis is itself divided into at least four separate parts. A fifth part is present in some areas of our body. In order from the deepest layer of the epidermis to the most superficial, these layers strata are the:. Skin overview : Skin layers, of both hairy and hairless skin. Human skin: This image details the parts of the integumentary system.

The stratum basale, also called the stratum germinativum, is the basal base layer of the epidermis. This layer is one of the most important layers of our skin. This is because it contains the only cells of the epidermis that can divide via the process of mitosis, which means that skin cells germinate here, hence the word germinativum. In this layer, the most numerous cells of the epidermis, called keratinocytes, arise thanks to mitosis.

Keratinocytes produce the most important protein of the epidermis. This protein is appropriately called keratin. Keratin makes our skin tough and provides us with much-needed protection from microorganisms, physical harm, and chemical irritation.

Millions of these new cells arise in the stratum basale on a daily basis. The newly produced cells push older cells into the upper layers of the epidermis with time.

As these older cells move up toward the surface, they change their shape, nuclear, and chemical composition. These changes are, in part, what give the strata their unique characteristics. The stratum basale is primarily made up of basal keratinocyte cells, which can be considered the stem cells of the epidermis. They divide to form the keratinocytes of the stratum spinosum, which migrate superficially.

From the stratum basale, the keratinocytes move into the stratum spinosum, a layer so called because its cells are spiny-shaped cells. From there the keratinocytes move into the next layer, called the stratum granulosum. This layer gets its name from the fact that the cells located here contain many granules.

The keratinocytes produce a lot of keratin in this layer—they become filled with keratin. This process is known as keratinization. The keratinocytes become flatter, more brittle, and lose their nuclei in the stratum granulosum as well.

Once the keratinocytes leave the stratum granulosum, they die and help form the stratum lucidum. This death occurs largely as a result of the distance the keratinocytes find themselves from the rich blood supply the cells of the stratum basale lie on top off. Devoid of nutrients and oxygen, the keratinocytes die as they are pushed towards the surface of our skin. This layer is only easily found in certain hairless parts of our body, namely the palms of our hands and the soles of our feet. Meaning, the places where our skin is usually the thickest.

From the stratum lucidum, the keratinocytes enter the next layer, called the stratum corneum the horny layer filled with cornified cells.

This the only layer of skin we see with our eyes. The keratinocytes in this layer are called corneocytes. They are devoid of almost all of their water and they are completely devoid of a nucleus at this point.

They are dead skin cells filled with the tough protein keratin. In essence, they are a protein mass more so than they are a cell.

The corneocytes serve as a hard protective layer against environmental trauma, such as abrasions, light, heat, chemicals, and microorganism. Melanocytes produce the skin coloring or pigment known as melanin , which gives skin its tan or brown color and helps protect the deeper layers of the skin from the harmful effects of the sun. Sun exposure causes melanocytes to increase production of melanin in order to protect the skin from damaging ultraviolet rays, producing a suntan.

Patches of melanin in the skin cause birthmarks, freckles and age spots. Melanoma develops when melanocytes undergo malignant transformation. Merkel cells, which are tactile cells of neuroectodermal origin , are also located in the basal layer of the epidermis. The squamous cell layer is located above the basal layer, and is also known as the stratum spinosum or "spiny layer" due to the fact that the cells are held together with spiny projections.

Within this layer are the basal cells that have been pushed upward, however these maturing cells are now called squamous cells, or keratinocytes. Keratinocytes produce keratin , a tough, protective protein that makes up the majority of the structure of the skin, hair , and nails. The squamous cell layer is the thickest layer of the epidermis, and is involved in the transfer of certain substances in and out of the body.

The squamous cell layer also contains cells called Langerhans cells. These cells attach themselves to antigens that invade damaged skin and alert the immune system to their presence. The keratinocytes from the squamous layer are then pushed up through two thin epidermal layers called the stratum granulosum and the stratum lucidum. As these cells move further towards the surface of the skin, they get bigger and flatter and adhere together, and then eventually become dehydrated and die.

This process results in the cells fusing together into layers of tough, durable material, which continue to migrate up to the surface of the skin.