Layers & Structure
This layer of the epidermis is the only one that is mitotically active and contains the melanocytes that transfer pigment to neighboring cells.
Stratum Basale
All humans have approximately the same number of melanocytes. What two factors then determine how dark an individual’s skin can become?
Genetics & Environment
The keratin in nails is harder than the keratin in the stratum corneum. What does this difference imply about the degree of disulfide bonding (chemical cross links)?
There is a higher degree of cross-linking
Sebaceous glands are holocrine. Describe exactly what happens to the secretory cell during sebum release.
Entire cell fills with sebum and then disintegrates, releasing its contents?
During the inflammatory phase of wound healing, blood vessels dilate and become more permeable. What three things are able to move in with the blood?
Oxygen, nutrients and immune cells
The border between the epidermis and dermis is uneven and this structural feature contributes to both nutrition of the epidermis and the formation of fingerprints.
Epidermal ridges and dermal papillae
Distinguish between eumelanin and pheomelanin in terms of color
eumelanin (brown-black, widespread) versus pheomelanin (red-yellow)
The hair bulge is a critical region for two reasons related to growth and pigmentation. Identify both.
Stem cells for hair growth and the presence of melanocytes that determine hair color
Although traditionally called “apocrine,” the scent glands of the axillary and genital regions are actually merocrine in their mode of secretion. What does this mean at the cellular level?
secretion by exocytosis without loss of cytoplasm
These corpuscles are concentrated in dermal papillae and detect light touch and texture
What are Meissner’s corpuscles
This layer is present only in thick skin and lies between the stratum granulosum and stratum corneum
Stratum Lucidum
Melanin is packaged into melanosomes and transferred to keratinocytes. Once inside the keratinocyte, where does the pigment preferentially accumulate? Why?
Surrounding the nucleus to protect DNA
Match how the cross-sectional shape of the hair follicle determines whether hair is straight, wavy, or curly/coily.
What is round follicle → straight;
oval → wavy;
flat/ribbon-shaped → curly or coily?
Compare the primary stimulus and the composition of the secretion of eccrine versus apocrine sweat glands.
temperature regulation with watery, salty secretion (eccrine) versus emotional/pubertal activation with protein- and lipid-rich secretion (apocrine)
These corpuscles detect deep pressure and vibration.
Pacinian corpuscles
Although the hypodermis is not technically part of the skin, it performs two critical functions related to thermoregulation and structural support. Name both.
Insulation (via adipose) and binding the skin to underlying tissues
A patient presents with yellowish skin. Give two completely different physiological or dietary causes
carotene accumulation from diet and jaundice.
Which gland it associated with the hair follicle?
Sebaceous glands
Ceruminous glands and mammary glands are both modified sweat glands. What is the functional product of each and the adaptive advantage of that product
earwax (traps pathogens/debris) and milk (nourishes offspring
When core body temperature rises, two distinct effector responses involving the integument are activated. Identify both and explain how each lowers temperature.
Eccrine sweating (evaporative cooling) and dermal vasodilation (radiation of heat)
This is not part of the skin but contains the major blood vessels that feed it.
The hypodermic/ subcutaneous
Why can increased melanin production be both protective and potentially limiting for vitamin D synthesis?
Tradeoff: protection of DNA from UV damage versus reduced UV-B penetration needed to convert 7-dehydrocholesterol into vitamin D₃
A patient suffers permanent hair loss in a region after a deep burn. Which specific structure within the follicle must have been destroyed for the loss to be permanent?
The Hair Bulge
Why does the presence of sebum on the skin surface reduce water loss?
sebum creates an additional lipid barrier
A full-thickness burn destroys both the epidermis and dermis over a large area. Explain why such burns often require skin grafting rather than relying on regeneration from the wound edges alone.
The loss of the stratum basale over a large area (Prevents simple closure of wound by mitosis)