Med A&P Exam 1 Essays

Why is extreme anatomical variation very seldomly seen in living individuals? What essential concept does this illustrate? Create an original example (not from your book or from lecture) illustrating the reason extreme anatomical variation in tissues is not conducive to life.

o   Anatomical variation is rare because the human body is extremely well-adapted to life, and each structure has an intended ‘job.’

o   An extreme change of structure will disrupt critical physiological functions require to sustain life and can lead to death.

o   This illustrates the essential concept of complementarity, meaning that function reflects structure and that what a structure can do depends on its specific form.

o   An example: changing the arrangement of the contents of the heart, like the muscles or tissues, can cause them to run in random directions, which is extremely harmful because the heart is extremely coordinated. The heart may have issues pumping blood and can lead to death

Discuss why connective tissue polarity may be difficult or impossible to determine.

o   Connective and epithelial tissues are organized differently

o   Epithelial tissues are tightly packed and have polarity with clear apical (faces lumen) and basal (faces attachment) surfaces

o   Connective tissue contains cells surrounded by an extracellular matrix, which consists of matter that is much more dispersed, like that of ground substance and fibers (collagen, elastic, reticular), which surround cells and they lack clear apical and basal surfaces

o   Because these cells are more dispersed and contain lots of ‘in-between’ material, rather than a much simpler sheet, it is difficult to identity polarity for connective tissue

Would you expect the matrix in either dermal layer to be acidic, basic or neutral? Explain your answer. Be sure to fully describe the pH scale.

o   I would expect the dermis to lean more towards a slightly basic pH of about 7.1-7.4, though basic pH’s range from 7.01-14 (fewer H+ ions)

o   The epidermis, which is avascular, maintains an acidic environment of about 4-6, though acidic pH’s range from 0-6.99 (more H+ ions) due to the secretions by the eccrine glands (lactic acid/sweat) onto the stratum corneum to slow bacterial growth.

o   The eccrine glands do not secrete anything into the dermis and do not contribute to its environment. It is likely slightly basic, possibly having a pH relatively near 7.4 because that is the pH of blood, which because the dermis has varying vascularity, is constantly circulated through the dermis.

o   A neutral pH is seven, and due to the circulation of blood, the dermis veers more towards a slightly basic environment, though it is very close to neutral

Are glands in your stomach that produce stomach acids considered to be exocrine or endocrine? Explain your answer.

o   Endocrine glands are internal secretions into the blood or extracellular space

o   Exocrine glands are external secretions onto an epithelial body surface

o   The digestive tract is lined with mucosal membranes running from the mouth and continues through to the stomach. Considering this, the stomach is kept separate from the blood/extracellular space and is technically an outside space that resides within the body.

o   This means that the stomach acid is technically being secreted to an outside body surface, and are exocrine glands.

 

Considering the integumentary system, list the structure(s) at each hierarchical level of the integument, and then list the corresponding function at each level as the result of such structure.

Atomic/Molecular (Chemical level)

o   keratin, collagen, melanin, carotene, hemoglobin

o   Function: keeps the skin strong and protects the skin from the sun. Also produces skin color

Cellular:

o   Keratinocytes, melanocytes, Langerhans cells, Merkel cells, fibroblasts, macrophages, mast cells

o   Function: produces cells that protect and add strength to the skin and assist in supporting the immune system

Tissue:

o   Epidermis

• Keratinized stratified squamous epithelium

o   Dermis

• Dense irregular/areolar

o   Function: protects the skin from abrasion/corrosion, as well as longitudinal stress. Also keeps the skin hydrated.

Organ:

o   Skin

• Stratum Basale, spinosum, granulosum, lucidum, corneum (epidermis)

• Papillary/reticular layer (dermis)

o   Function: provides a waterproof seal, flexibility, and protection from the external environment

Organ system/organism:

o   Integumentary system

• Skin, hair, nails, sweat glands (eccrine/apocrine/mammary), sebaceous glands

o   Function: protection, body temperature regulation, cutaneous sensation, metabolic functions, blood reservoir, excretion

Which skin appendage is most necessary for life? Explain.

o   Sweat glands are the most necessary because of their various protective functions

o   Eccrine sweat glands allow for thermoregulation by the release of true sweat, containing 99% water, Nitrogenous wastes, lactic acid, and antibacterials, which cool the body down when evaporated.

o   Sweat maintains an acidic environment on the stratum corneum (pH 4-6), which slows bacterial growth, so these glands assist in fighting pathogens

o   Apocrine sweat glands, such as ceruminous glands, produce ear wax, which contain a mix of oil and sweat to protect the ear from foreign objects.

o   Mammary glands provide milk, which is essential for growing infants.

Most soaps are basic (alkaline). Why would overuse of soap be problematic on the skin? Which processes would be affected? Be sure to include the structures involved.

o   This may interfere with the skin’s chemical barrier (stratum corneum)

o   The skin maintains an acidic environment, especially with skin secretions, through the eccrine glands, like sweat/lactic acid which slows bacterial growth (pH 4-6)

o   If the skin is repeatedly exposed to this soap, the work of the eccrine glands to produce sweat would not be effective and the acidic environment of the epidermis would be disrupted, thus the protective function of the skin would be affected.

o   It also strips the skin of sebum, which is produced by the sebaceous glands. Because sebum acts as an antibacterial, this too can make the skin more susceptible to infection

If the epidermis only was damaged, would healing be faster or slower than damage to the dermis only? Why?

o   The epidermis heals much faster than the dermis

o   The epidermis has a fast regeneration time due to the presence of epithelial tissue

o   The stratum Basale is made of active mitotic stem cells and would repair the damaged cells very quickly

o   The dermis is made of connective tissue, which contains fibroblasts

o   Fibroblasts produce the matrix, which contains both ground substance and fibers, making it a bit more complex than epithelial tissue

o   Because of the vascularity of the connective tissue, the body would also need to repair the broken blood vessels.

o   The complexity of the connective tissue would likely take more time to replenish, especially since they do not contain the active mitotic stem cells like the epithelial tissue

During your consultation with Stacey, a pre-operative patient, she asks why the IV meant to keep her hydrated during surgery will not contain pure water. Fully explain the implications of pure water infusion with regarding to the skin specifically.

o   Water moves according to osmosis, meaning it moves from an area of low solute concentration to an area of high solute concentration (it dilutes)

o   Because cells have a much higher concentration of solutes as opposed to its surroundings, the water would move across the semipermeable membrane of cells and it can cause them to burst (lysis). Water likes to equalize concentrations, but it can be detrimental in this case (hypotonic environment)

o   Some examples of how this can be damaging:

o   Keratinocytes: strengthen the skin, if cells burst, the skin will have a harder time protecting the body, which plays a big part in protecting

o   Melanocytes: protect the skin from UV, if burst, skin would not be able to be protected from sun

o   Langerhans’s cells (Macrophages): if these burst, they can no longer function in support of the immune system, leaving a patient vulnerable to infection

o   Even if these cells do not burst, the swelling in general can be a major problem, because once a structure if affected, so does its function

o   E.g. if the cells within the eccrine glands have swollen, as well as those around it, it may prevent the glands from secreting sweat and will disrupt her ability to thermoregulate

11. Discuss all the functions of the integument. Be sure to list and discuss specific structures that contribute to each function.

Protection

o   Chemical barrier: skin secretions/sweat (eccrine glands), melanin (melanocytes), antibiotic substances

o   Physical barrier: tight junctions, desmosomes, keratin (keratinocytes)

o   Biological barrier: Langerhans’s cells (activates immune system), macrophages (eating pathogens)

Body temperature regulation

o   Blood vessel constriction/dilation

o   Evaporative cooling of sweat (sweat released eccrine glands)

Cutaneous sensation

o   Sensory receptors (Merkel cells/Meissner’s corpuscle)

Metabolic functions

o   Synthesis of vitamin D from circulating cholesterol (through blood vessels)

Blood reservoir

o   Dermis vascular supply holds about 5% of total blood volume

Excretion

o   Release of salts, nitrogenous waste, lactic acid (Eccrine sweat glands)

o   Release of fatty acids, protein (Apocrine sweat glands)