Skin AN

What is keratin?

A protein that helps the epidermis protect from abrasions/penetration and stay waterproof.

What are keratohyalin granules?

Produced in the stratum granulosum; help form keratin in the stratum corneum and stratum lucidum.

What are lamellar granules?

Produced in the stratum granulosum; secrete lipids that waterproof our skin.

What are desmosomes?

Connect keratinocytes in our epidermis.

What is melanin?

A pigment that shields keratinocytes from UV radiation.

What are dendritic (Langerhans) cells?

Cells that ingest foreign substances and activate our immune system.

What is a callus?

Occurs when keratinocytes undergo significant friction.

What are melanocytes?

Cells that produce pigment.

What are keratinocytes?

Most abundant cells in the epidermis.

What are tactile (Merkel) cells?

Cells that sense light touch.

What is the stratum corneum?

Top/superficial layer of the epidermis.

What is the stratum lucidum?

2nd layer of the epidermis.

What is the stratum granulosum?

3rd layer of the epidermis.

What is the stratum spinosum?

4th layer of the epidermis.

What is the stratum basale?

Bottom (5th) layer of the epidermis.

What makes up 90% of epidermal cells?

Keratinocytes.

Which cells activate our immune system?

Langerhans cells.

Which cells are also known as dendritic cells?

Langerhans cells.

Which cells are also known as tactile epithelial cells?

Merkel cells.

As these cells approach the stratum corneum, they flatten and die.

Keratinocytes.

Which cells are formed in the bone marrow and migrate to the stratum spinosum of the epidermis?

Langerhans cells.

Friction stimulates the production of these cells, forming calluses.

Keratinocytes.

Which cells ingest foreign substances?

Langerhans cells.

Which cells are only found in the stratum basale?

Melanocytes.

Which cells are present at the junction between the epidermis and dermis?

Merkel cells.

Which cells produce a pigment that covers keratinocytes, blocking UV radiation?

Melanocytes.

Which cells produce a pigment that determines hair, skin, and eye color?

Melanocytes.

Which cells produce a protein that helps the epidermis protect from abrasions/penetration and stay waterproof?

Keratinocytes.

Which cells produce keratin?

Keratinocytes.

Which cells produce melanin?

Melanocytes.

Which cells are produced in the stratum basale but get pushed upward by new cells beneath them?

Keratinocytes.

Which cells sense light touch?

Merkel cells.

Which cells exist in similar numbers in all humans?

Melanocytes.

Which cells are spider-shaped?

Melanocytes.

Which cells are shed by the millions daily?

Keratinocytes.

Which layer of the epidermis is made of dead cells?

Stratum corneum, stratum lucidum.

Which layers of the epidermis are made of living cells?

Stratum granulosum, stratum spinosum, stratum basale.

Which layer is called the “clear” layer?

Stratum lucidum.

Which layer makes up ¾ of the thickness of the epidermis?

Stratum corneum.

Which layer contains 20 to 30 layers of squamous, anucleate keratinocytes?

Stratum corneum.

Which layer has cells that are dead and shed continuously?

Stratum corneum.

Which layer consists of a single row of stem cells that rapidly undergo mitosis?

Stratum basale.

Which layer constantly creates keratinocytes and pushes the higher layers upward?

Stratum basale.

Which layer is the deepest epidermal layer?

Stratum basale.

Which layer is found only in thick skin?

Stratum lucidum.

Which layer has cells full of keratin, protecting against abrasion and penetration while waterproofing the skin?

Stratum corneum.

In which layer do keratinocytes appear spiny due to desmosomes?

Stratum spinosum.

Which layer is where cells lose their nuclei?

Stratum lucidum.

Which layer makes up the outer layer of your skin?

Stratum corneum.

Which layer is right above and attached to the dermis?

Stratum basale.

Which is the most superficial epidermal layer?

Stratum corneum.

In which layer are keratohyalin granules formed?

Stratum granulosum.

In which layer are lamellar bodies formed?

Stratum granulosum.

Which layer contains melanocytes?

Stratum basale.

Which layer contains Langerhans cells?

Stratum spinosum.

What are the 2 main layers of the skin, and which layer is not technically part of the skin?

Epidermis and dermis; the hypodermis (subcutaneous layer) is not technically part of the skin.

What is the relationship between melanocytes and skin color?

All people have about the same number of melanocytes; differences in skin color are due to the amount and type of melanin produced.

What is the function of the acid mantle on the skin?

It is a thin, slightly acidic film on the surface of the skin that acts as a barrier against bacteria, viruses, and contaminants.

What is the relationship between UV rays and vitamin D?

UV rays stimulate the skin to produce vitamin D, which is important for calcium absorption and bone health.

What is the relationship between hair texture and hair follicle shape?

Round follicles produce straight hair, oval follicles produce wavy hair, and flat/ribbon-like follicles produce curly hair.

What are considered the skin appendages?

Hair, nails, sweat glands, and sebaceous (oil) glands.

Skin is what fraction of your body weight?

About 7%.

How many layers are in the dermis, and what are they?

2 layers — papillary layer and reticular layer.

How many layers are in the epidermis, and what are they (from deep to superficial)?

5 layers — stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), stratum corneum.

What is the main characteristic of the stratum basale?

Single row of mitotic stem cells (site of keratinocyte production, contains melanocytes and Merkel cells).

What is the main characteristic of the stratum spinosum?

Keratinocytes appear spiny due to desmosomes; contains Langerhans cells.

What is the main characteristic of the stratum granulosum?

Contains keratohyalin granules (keratin formation) and lamellar bodies (waterproofing lipids).

What is the main characteristic of the stratum lucidum?

Clear layer of dead keratinocytes; found only in thick skin.

What is the main characteristic of the stratum corneum?

20–30 layers of dead, flat, keratin-filled keratinocytes; provides barrier and waterproofing.

Which layer(s) contain dead keratinocytes?

Stratum lucidum and stratum corneum.

Which layer(s) contain cells undergoing mitosis?

Stratum basale.

Which layer appears “spiny” and why?

Stratum spinosum, because desmosomes hold keratinocytes together, creating a spiny look.

What is the function of Langerhans cells?

Ingest foreign substances and activate the immune system.

What is the function of Merkel cells?

Sense light touch (mechanoreceptors).

Which cells are formed in the bone marrow?

Langerhans cells.

What is the most common epidermal cell?

Keratinocytes.

Which cells are stimulated by friction?

Keratinocytes (leading to callus formation).

What is the function of lamellar bodies?

Secrete lipids that waterproof the skin.

What is in sweat?

Water, salts (NaCl), vitamin C, antibodies, metabolic wastes, lactic acid, and dermcidin (antimicrobial peptide).

What type of tissue is the epidermis made of?

Keratinized stratified squamous epithelium.

What type of tissue is the dermis made of?

Connective tissue (areolar in papillary layer, dense irregular in reticular layer).

Which layer has “squamous anucleate” cells, and what does that mean?

Stratum corneum; the keratinocytes are flat (squamous) and without nuclei (anucleate) because they are dead.

What structure contracts to raise hair on end?

Arrector pili muscle

What structure creates fingerprints?

Dermal papillae

What structure absorbs shock?

Hypodermis (subcutaneous fat)

What is the tunnel that hair grows from?

Hair follicle

What senses heavy touch?

Pacinian corpuscles (lamellar corpuscles)

What senses pain?

Free nerve endings

What are two ways skin responds to cold to maintain body warmth?

Arrector pili contraction (goosebumps) & Vasoconstriction (narrowing blood vessels)

What is the function of sebum?

Lubricates and waterproofs skin/hair, antibacterial properties

Example of skin as a physical barrier?

Stratum corneum (keratin & dead cells block pathogens/abrasion)

Example of skin as a chemical barrier?

Acid mantle (low pH, sweat, sebum slow bacteria growth)

Example of skin as a biological barrier?

Langerhans cells & macrophages (immune defense)

What are the three main types of skin cancer?

Basal cell carcinoma, Squamous cell carcinoma, Melanoma