Session 10: Tissues of the skin

Question 1

List the 5 layers of epidermis and briefly describe each.

Answer 1

1. Stratum corneum
   - flattened cells devoid w/ organelles and filled w/ mature keratin
2. Stratum lucidum
   - homogenous layer
3. Stratum granulosum
   - numerous, dense basophilic granules = keratohyline granules
4. Stratum spinosum
   - ‘prickly’ appearance
5. Stratum basale
   - cuboidal cells that rest on a basement membrane

Question 2

Name the 4 different cell types that occur in the epidermis and describe briefly the function of each.

Answer 2

1. Keratinocytes
   - concerned w/ production of keratin
2. Melanocytes
   - produce melanin
   - responsible for skin pigmentation
   - protection against UV light
   - dendritic
   - transfer melanin to stratum spinosum
3. Langerhans cells
   - represents macrophage-monocyte system
   - act as antigen-presenting cells
   - migrate to lymph nodes after stimulation
   - cell mediated immune response
   - delayed hypersensitivity reactions
4. Merkel’s cells
   - sensory receptors
   - mechanoreceptor
   - ass. w/ afferent nerve fiber
   - in stratum basale

Question 3

Describe the process of keratinisation in 3 detailed steps.

Answer 3

1. Basal cells:
   -synthesize
   tonofilaments
2. Spinosous layer:
   -synthesis of tonofilaments into tonofibrils and keratohyaline granules; as well as lamellar bodies
3. Stratum granulosum;
   -lamellar bodies = discharged
   -keratohyaline granules in cytoplasm
   -keratohylaline granules + tonofibrils form keratin
   -changing of the cells include loss of organelles

Question 4

What are the 2 components of the water barrier and what is each made of?

Answer 4

1. Cell envelope
   * insoluble proteins deposited on the inner surface of the plasma membrane
2. Lipid envelope
   * layer of lipid attached to outer plasma membrane

Question 5

What is the epidermis-dermis junction?

Answer 5

An uneven boundary consisting of dermal papillae, epidermal ridges and dermal ridges.

Question 6

Name the 5 nerve receptors, their location and function.

Answer 6

1. Free nerve endings
   * stratum granulosum
   - receptor for fine touch, heat, cold, pain
   - mechanoreceptor in hair follicle
2. Ruffini’s corpuscles
   - mechanoreceptor
3. Pacinian corpuscles
   * deeper dermis + hypodermis
   - vibration and pressure receptor
4. Meissner’s corpuscles
   * papillary dermis
   - light touch receptor
5. Merkel’s corpuscles
   * basal layer
   - mechanoreceptor

Question 7

List the 4 structures in the skin that contribute to temp. control.

Answer 7

1. Sebaceous glands
2. Eccrine sweat glands
3. Apocrine sweat glands
4. Hair follicles

Question 8

Compare the apocrine and eccrine sweat glands.

Answer 8

• Refer to table

Question 9

Where is the nail root of the nail found?

Answer 9

In the matrix

Question 10

What is the lunula of the nail?

Answer 10

The white area near the nail root

Question 11

What is the eponychium of the nail?

Answer 11

The proximal “nailfold”

Question 12

What is the hyponychium of the nail?

Answer 12

The skin underneath the free edge of the nail.

Question 13

What are the 6 general functions of the skin?

Answer 13

1. Homeostasis maintenance   
 (water loss, temp.)
2. Endocrine secretion of hormones
3. Exocrine secretion of substances
4. Sensory info about the environ.
5. Immunologic 
6. Barrier against environment

Question 14

What is the difference between thick and thin skin?

Answer 14

In thin skin, stratum lucidum is absent.