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BISC 125 Integumentary System


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What are components of the integumentary system?
Skin, glands, hair, and nails
What are the functions of the integumentary system?
Mechanical protection (keranized epithelium); water barrier (protects C.T. from fluid evaporation); regulation of body temperature (blood supply); immune defense (lymphocytes in subepithelial C.T.); excretion of salts (sweat glands); sythesis of vitamin D; sensory awareness (large plexus of nerve fibers); sexual signaling; and indicator of health (skin complexion)
What are the layers of skin (starting with outermost)?
Epidermis, dermis, and hypodermis
What are the five epidermal layers of thick skin (starting with innermost)?
Stratum basale, stratum spinosum, stratum granulosum, stratum lucium, stratum corneum
What are the two layers of the dermis?
The papillary layer (top layer) and the reticular layer
What is another name for the superficial fascia (or subcutaneous layer)?
The hypodermis
What is the hypodermis composed of?
Loose C.T. and lots of blood vessels
Which type of skin (thick or thin) has hair follicles?
Thin skin
What are keratinocytes?
The most numerous skin cell; produces keratin, an intermediate filament protein
What are melanocytes?
Make up about 10% of epidermal cells; derived from neural crest cell (melanoblasts), so it has a dendritic shape. They produce melanin, injecting it into keratinocytes via cytocrine secretion.
What are Merkel cells?
Pressure receptors in the epidermis; contacts myelinated nerve fibers projecting from the dermis into the epidermis (associated with nerve plate)
What are Langerhan's cells?
Come from bone marrow precursor; are dendritic-shaped antigen-presenting cells (part of the reticuloendothelial system); They DO NOT junction with keratinocytes-can move around
Where do Langerhan's cells go when they leave the epithelium?
They pass into the C.T., then travel through lymphatic capillaries to lymph nodes via afferent lymphatic vessels
When are Langerhan's cells particularily used as antigen-presenting cells to interact with T-cells?
During the initiation of cutaneous hypersensitivity reactions
What cells are found in the stratum basale?
Keratinocytes, Merkel cells, and melanocytes
How do keratinocytes in the stratum basale join the basal lamina?
Using hemidesmosomes
Why is the stratum basale also called the stratum germaninativum?
Because there is an abundance of stem cells and a lot of mitotic activity
How many cell layers thick are the three cellular layers of the epidermis?
Basale, one cell layer; spinosum and granulosum, several layers
What are the "spines" in the stratum spinosum?
Keratinocytes are joined by bridges of cytoplasm (desmosomes), and shrinkage artifact causes cells to appear to have spines
What cells are in the stratum spinosum?
Keratinocytes and Langerhan's cells
In what layer do keratinocytes die?
The stratum granulosum
What layer of the epidermis has a glycolipid coating (water barrier of epidermis)?
The stratum lucium
What are the layers of the epidermis of thin skin?
The stratum basale, stratum spinosum, and stratum corneum
What does the papillary layer of the dermis contain?
Loose C.T., papillae (bumps where it meets the basal lamina of the epidermis), lymphocytes, macrophages, and nerves
What do the papillae of the dermis contain?
Capillary loops and special nerve endings
What is the reticular layer of the dermis composed of?
Dense irregular C.T.; collagen and elastic fibers
Which layer of the dermis contains sweat and sebaceous glands (and hair follicles)?
The reticular layer
What layer of the skin contains circulatory elements that help regulate body temperature?
The dermis
How does the vascular plexus in the dermis carry blood (starting in the papilla)?
Capillaries (within dermal papilla) to subpapillary plexus to the cutaneous plexus to the hypodermic/subcutaneous plexus (in hypodermis); there they nourish adipose tissue, sweat glands, and deeper segment of hair follicles
Why are Langer's lines important?
Cutting with these tension lines in skin reduces scarring
What does the hypodermic layer contain?
Loose C.T., subcutaneous fat, vascular and nervous elements, and portions of sweat glands and hair follicles
What are the two types of sweat glands?
Eccrine and apocrine glands
What type of secretion do eccrine and apocrine glands use?
Merocrine secretion
What is the structure of eccrine glands?
Prominent secretory and ductal cells; coiled tubular shape
What allows sweat glands to contract (allows "sweating")?
Myoepithelial cells innervated by sympathetic nerves
Where are myoepithelial cells located in sweat glands?
Between the basal lamina and clear cells
Which sweat glands are sensitive to aldosterone?
Eccrine sweat glands (excretory portion partially reabsorbs NaCl and water under aldosterone influence)
When do apocrine sweat glands become active?
During puberty; the secretion is broken down by bacteria and results in BO
Where is the secretory portion of apocrine sweat glands located?
In the dermis and the hypodermis
Where do apocrine sweat glands open up to (where do the secretions come to the surface)?
In the hair follicle
What are the differences between eccrine and apocrine sweat glands?
Apocrine glands are bigger (secretory acini are larger)and less numerous
What is the only (modified) apocrine gland that actually uses aprocrine secretion?
Mammary glands; other modified apocrine glands are ceruminous (ear wax) and moll (eye crud)
What is a pilosebaceous gland?
A sebaceous gland associated with a hair follicle
What type of secretion do sebaceous glands employ?
Holocrine secretion
How do sebaceous glands expel their secretory material?
Use arrector pili muscle (smooth); NO myoepithelial cells
What do sebaceous glands secrete?
A waxy, sebaceous material; oily secretion released on surface of hair and epidermis
Where is the secretory portion of sebaceous glands?
In the dermis
What are the two components of the hair follicle?
The epithelial component (shaft, bulb) and the dermal papilla (has blood vessels feeding epithelial cells)
What does the arrector pili muscle do?
It's contractions cause goosebumps and squeezes sebaceous glands (empties them)
What does aging do to the integumentary system?
Loss of elasticity, loss of vascularity, reduction in sweat gland output, thinning of skin
Why must the skin be slit halfway through the dermis during skin grafting?
It leaves hair follicles and epithelial cells to produce a new dermis.

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