Unit 2 Flashcards
(25 cards)
How do we know that fingerprints are unique?
There is a lot known about the process of friction ridges forming in the womb and that information shows a lot of random environmental factors that would be nearly impossible to replicate. For example, the growth of tissues pushes the skin in different directions and the skin pushes up against other things in the womb.
This is also held true in practice: The FBI has millions of fingerprints in NGI with no known matches to other people. Over 100 years of comparisons haven’t shown true identical fingerprints.
Prints are unique for the same reason people are: Variation is the norm, not the exception.
Name the types of secretory glands
Eccrine, Sebaceous, and Apocrine
Eccrine Glands
The most abundant gland type in the skin. Also present in friction ridge skin (the dermal layer). Sweat from these glands is composed of mostly water, salt, urea, amino acids, and proteins.
Apocrine Glands
Typically located where coarse hair is found (armpits, pubic hair regions). They are larger glands that secrete thicker fluid which can include proteins, carbohydrates, cholesterol, etc. Not located on friction ridge skin.
Sebaceous Glands
Found in areas where fine body hair is located and seems to lubricate hair and retain body heat. Secretes sebum rather than sweat. This is a generally thicker fluid composed of lipids (fats) and cholesterol. Not located on friction ridge skin.
What are amino acids?
Amino acids are building blocks that bind together to become proteins, which helps the body perform simple functions. Proteins can be part of the immune system, help grow muscle, and many other simple functions.
What are lipids?
Lipids are more of an oily or fatty substance. They can be used to store energy. Or, as a hormone, can help cells communicate.
What are 3 levels of attachment ensuring persistence of friction ridges?
First level: The topography between the dermis and epidermis, which includes dermal papillae, anastomoses, and anchored sweat glands. These structures provide re-enforcement between layers.
Second level: The basement membrane zone provides a fibrous connective sheet between the dermis and epidermis (via hemidesmosomes)
Third level: Cell-to-cell attachments which maintain the surface template from the time cells reproduce at the basal layer. These attachments are desmosomes and focal tight junctions.
Name and describe the cell-to-cell attachments in the epidermis
Desmosomes- anchoring sites that attach sections of cell membranes like cement
Focal tight junctions- areas of the cell membranes that fuse together (like welding)
What are the 3 anatomical layers of skin?
Epidermis, dermis, hypodermis
Describe the epidermis
The outermost layer of skin. It provides protection, and the friction ridge portion allows for grip by providing friction.
Describe the dermis
Positioned beneath the epidermis and provides structural support and nutrients to the epidermis. It is a fibrous tissue layer containing collagen and elastic tissues; it also contains glands, blood vessels, and nerve endings.
Describe the hypodermis
Positioned beneath the dermis and consists mostly of fat. Provides insulation and cushioning.
What are the layers of the epidermis?
The deepest layer is where new cells are formed and is called the stratum basal. Above that is the stratum spinosum, the stratum granulosum, the stratum lucidem and the uppermost layer, the stratum corneum.
Briefly describe the skin cell life cycle as it moves through the layers of the skin
The overall goal of the skin cell’s life cycle is to fill with keratin which will harden the cells to provide protection. The entire cycle takes about 28 days. New cells are formed at the stratum basal which acts as a blueprint for the friction ridges on the top layer. As they move upwards through the layers they are going to gradually flatten out. They are bound together by a substance called desmosome so they move upward in unison as new cell growth pushes them upwards. In the stratum spinosum, the cells are increasing production of keratin and reinforcing their attachments to each other. In the stratum granulosum, the cells prepare to fill with keratin and start to form a waterproof barrier to protect the skin. In the stratum lucidem, cells complete cell death and start to harden, so that by the time cells reach the stratum corneum they are hardened and keratinized. The stratum corneum is quite thick for protection. Cells have a brick and mortar appearance and eventually at the very top of the stratum corneum, the cell connections wear down and dead cells are shed.
What types of cells are in the skin?
Mostly keratinocytes, which just means cells that are rich in keratin. Keratin is the substance found in your nails and hair that gives them strength. Skin also has melanocytes which produce melanin and provide protection from the sun. There are also Langerhans cells which participate in the body’s immune response, and Merkel cells which provide sensory function in the deepest layer of the epidermis.
How is homeostasis maintained by the layers of the skin?
Cell communication regulates the rate of cell replication in the basal layer. This is achieved through the use of signals, like chalone monitoring, and gap junctions, which allow cells in the layer to move simultaneously. This essentially regulates cell death as well as cell production to maintain homeostasis.
What is the area between the dermis and epidermis and what does it do?
The basement membrane, aka the basal lamina. It provides structural support and acts as a filter for nutrients to pass to the epidermis.
Describe the informal layer of the skin.
The informal layer is known as the suprabasal layer and exists along primary ridges above the stratum basal. Its purpose is to allow for increased cell production to make up for the extra stress primary ridges endure.
In the suprabasal layer, cells become what is known as “transient amplifying cells” which can replicate several times before beginning to mature.
Define minutiae
The details and characteristics of a single ridge, such as when it begins, ends, and branches.
When do fingerprints form?
At roughly 12 weeks gestation in the womb.
What foundation for the basis of fingerprint analysis provides individualization?
The fact that they are permanent (persistent) and unique (highly discriminatory).
Does everybody have fingerprints?
Barring any severe injury, disease, or rare genetic condition, most everybody has fingerprints.
How does a scar form?
If injury reaches the cell-producing layer of the skin, it interrupts the blueprint of the friction ridge skin so that blueprint will be re-formed. A blood clot will form while the immune system triggers the healing process. The cells in the production layer produce new cells to heal over the wound, but those cells will follow the shape of the wound. The skin’s tissue puckers together to speed up the process which can give a puckered appearance at the surface. As the new cells are formed they re-form their connections to each other and start regular cell production.
Sometimes we see scars as black voids or white voids because the new epidermis can sit below the level of its surrounding ridges. The appearance of a scar in an impression can show some variability just like any other skin feature due to the transferring of a 3-dimensional object to a 2-dimensional surface.
