Review Questions Flashcards
What are the layers of the epidermis?
It is a stratified squamous kenatinized epithelium comprised of layers of keratinocytes (make keratin).
The layers of epidermis include (from deep to superficial): the stratum basale; the stratum spinosum; the stratum granulosum; and the stratum corneum.
How long does it take to replace your epidermis? Where are new cells formed?
Your entire skin is replaced approximately evey month.
In the basal part of the epithelium
What is the stratum basale? What shape are the cells?
The stratum basale is the deepest layer of the epidermis. It is one cell layer thick with all cells touching the basal lamina and attached to it by hemidesmosomes. These cells are cuboidal in shape and are mitotic.
Name functions of stratum basale cells?
They form stem cells for generation and replacement of the keratinocytes. These cells have basophilic cytoplasm because of lots of ribosomes synthesizing keratin. These cells also contain pigment granules (melanosomes) that are produced by melanocytes, but phagocytosed by keratinocytes.
What are the functions of the melanosomes?
To protect the nuclei of the stem cells from UV damage
What is the stratum spinosum?
This is the thickest layer. It is comprised keratinocytes that have been generated by the basal cells and that lose attachment to basement membrane.
What connects cells in the stratum spinosum?
These cells are connected to one another by desmosomes that give the cells the appearance of spines when they shrink away from one-another. The intermediate filament (keratin) groups into tonofibrils that attach to desmosomes and hold cells together.
What is the stratum granulosum?
The cells of the stratum granulosum layer contain basophilic granules of keratohyalin (clumps of protiens including filaggrin) that hold tonofibrils together.
The cells assume a more flattened shape but still have a nucleus. In thick skin, there is a very thin, highly eosinophilic layer at the superficial transition area called the stratum lucidum.
What is the function of lamellar bodies in the stratum granulosum?
They produce a barrier to water movement through the skin (out or in).
What is the stratum corneum?
Most superficial layer; consists of dead cells filled with keratin and no nuclei.
There are still desmosomes (hold cells of the deeper layers together) while superficial do not have desmosomes. There is lipids (from the lamellar bodies) between cells that form a water barrier
What is the additional layer in thick skin?
Stratum lucidum
It is between the granular and cornified layer. Has flattened cells with no organelles
Where do melanocytes come from? What colors do eumelanin and pheomelanin make? Where do melanocytes produce melanin?
These are cells that derive from from neural crest cells. They have processes that contact up to 30 keratinocytes. The processes of the melanocytes are phagocytosed by keratinocytes that metabolize the product into a pigmented product.
Eumelanin: color of black or brown hair
Pheomelanin: red hair
Produce melanin in the melanosomes.
What is the function of melanin? Why are there differences in skin color? How?
Melanin protects cells (DNA) from UV radiation; The color of skin does not depend on the number of melanocytes but rather the rate and of transfer to the keratinocytes and density within the keratinocytes.
What layer are melanocytes found?
BASAL LAYER
What are Langerhans cells?
These are phagocytic and antigen processing cells (they present antigen to T-Lympocytes). They are pale staining with many processes, called dendrites (despite the fact that these are not neural). They are mostly found in stratum spinosum (found in all layers)
What are the functions of the Langerhans?
Responsible for skin immune reactions, including allergic reactions.
What are Merkel’s cells?
Modified keratinocytes that are in the BASAL LAYER;
Function as sensory receptors for fine touch and discrimination of form and texture
Describe papillary layer of the dermis
Has loose CT with a lot of blood vessels
Makes papillae (rete pegs) that stick up into the epidermis and increase contact area. The papillae are responsible for fingerprints. This layer contains nerves, fibroblasts and macrophages.
Describe reticular layer of the dermis
Has dense irregular CT with more collagen & elastin fibers than papillary layer.
The sweat glands stick down and through this layer.
Structure of the hypodermis?
This is made of loose CT with fat, nerves and sweat glands. It acts as a shock absorber and allows skin to slide over underlying structures. It is also known as the superficial fascia
Describe structure of a hair follicle
Has a root sheath with a bulb at the bottom of the tube.
The hair matrix (the growing part) surrounds the papilla and melanocytes provides hair color. The hair shaft is made of medulla (inner layer), cortex (middle layer) and cuticle (outer layer, highly keratinzed and roof shingle appearance).
How is the hair follicle nourished?
There is a dermal papilla that enters the bulb and nourishes it (made from part of the dermis)
What are the functions of the sebaceous (oil) glands in hair follicles?
The sebaceous (oil) glands that empty into the follicle. Lubricate hair and skin
What kind of glands are sebaceous glands?
Holocrine glands and secrete an oily secretion.
What are the functions of the arrector pilli muscles?
arrector pilli muscles (smooth, involuntary) contract to lift hair up and cause goosebumps.
What is the structure of eccrine sweat glands and where are they found?
These are simple coiled tubular glands found in the deep dermis and hypodermis. They empty by coiled tubular glands and secrete via MEROCRINE secretion.
What is the function of eccrine sweat glands?
In addition to their function in evaporative cooling, they secrete salt, urea and lactate. There are myoepithelial cells to help expel secretions.
What are apocrine sweat glands and where are they found?
These are simple coiled tubular glands found in the axilla and anogenital region. The lumen is large because secretions are stored in the lumen. They use merocrine sectetion and, although the secretions themselves are generally odorless, bacterial action causes the odor.
What are “azurophilic granules”?
Azurophilic granules are lysosomes that are present in all granulocytes. They can also be seen in monocytes.
What is the structure of the mammary glands?
These are compound tubuloacinar glands that develop along the “milk line”. The use apocrine (lipids) and merocrine (antibodies, proteins and sugars).
What happens to mammary glands when hormones kick in?
Under the influence of hormones (including prolactin) the ductal system becomes more complex and develops secretory aveoli (simple cuboidal or columnar epithelium with myoepithelium). Milk is released into lactiferous ducts (simple cuboidal) then lactiferous sinuses. Oxitocin stimulates the myoepithelium to eject milk (“letdown”).
What are keratinocytes?
Keratinocytes are the dominent cells of the epidermis (they make keratin).
What kind of epithelium lines the nasal cavity, trachea and main stem bronchi?
Pseudostratified columnar epithelium w/cilia and goblet cells.
What is the function of the olfactory epithelium?
Provides a sense of smell
What are the functions of the nasal mucosa?
It warms and moistens air and traps particles in the air. It also contains olfactory epithelium.
What is the direction of movement of cilia in the nasal cavity and the trachea?
The cilia move mucous and particles toward the oropharynx.
What is the epithelium over the vocal cords?
The vocal cords have non-keratinized stratified squamous epithelium
What is the structure of trachea? What kind of cartilage does it have and in what shape?
The trachea has a typical respiratory epithelium. The submucosa contains hyaline cartilage in a “C” shape which is open posteriorly. There is smooth muscle that is particularly prominent posteriory, where there is also a lot of fibroelastic tissue (helps with dilation and narrowing of trachea.
The entire organ is surrounded by an adventitia.
What is the lamina propria? What kind of tissue is in the lamina propria?
It is submucosal connective tissue that has a rich blood supply! There is lymphoid tissue that is particularly prominent in the lamina propria (MALT).
What is the function of the seromucous glands in the submucosa of the trachea and bronchi?
They drain through ducts into the lumen.