Anatomy and Physiology of the Skin and Soft Tissues

Question 1

Layers of Skin

Answer 1

1.  Epidermis
      Stratum corneum
      Stratum lucidum
      Stratum granulosum
      Stratum spinosum
      Stratum basale
2.  Basement membrane - dermal epidermal junction
3.  Dermis

Question 2

Where do you find stratum lucidum?

Answer 2

Only in the sole of the feet, the palm of the hands and on the fingertips

Question 3

How thick is stratum granulosum?

Answer 3

Only 2-5 cell layer thick (usually 3)

Question 4

What cells are found in stratum granulosum?

Answer 4

Keratinocytes and Langerhans cells. These cells are also found in the stratum spinosum.

Question 5

What are desmosomes?

Answer 5

Desmosomes are proteins that connect the cells on the sides (both the lateral sides and above and below sides)

Question 6

What are the cells in the epidermis?

Answer 6

Keratinocytes, Merkel cells, Langerhans cells, melanocytes

Question 7

What is special about the stratum basale?

Answer 7

It is the only metabolically active layer of the epidermis. Also called stratum germinosum. This layer contains the keratinocytes, melanocytes and Merkel cells. It is a single layer of epidermal cells.

Question 8

What are keratinocytes?

Answer 8

Made up 80% to 90% of cells in the epidermis. The terminally differentiated keratinocytes are called corneocytes: flattened cells, no nucleus or cytoplasm. The keratinocytes differentiate into corneocytes in the stratum granulosum.

Question 9

What are Merkel cells?

Answer 9

One of the 4 cell types found in the epidermis of the skin, associated with touch receptors. These cells are attached to keratinocytes by desmosomes.

Question 10

What are Langerhans cells?

Answer 10

One of the 4 cell types found in the epidermis. These cells are in the stratum spinosum and are bone marrow-derived and important in the immune function of the skin.

Question 11

What are the functions of the epidermis?

Answer 11

1. Protect from water loss
2. Provides a mechanical barrier to the invasion of bacteria and other pathogens (acid mantle, shedding of skins to keep bioburden at a tolerable level)
3. Protects from shear, friction and toxic irritants
4. Synthesis of vitamin D
5. Provides pigmentation

Question 12

what is the basement membrane zone?

Answer 12

The basement membrane zone is the dermal-epidermal junction.

Question 13

What does the basement membrane contain?

Answer 13

1. Fibronectin (an adhesive glycoprotein)
2. Type IV collagen (a non-fiber forming collagen)
3. Heparin Sulfate proteoglycan
4. Glycosaminoglycan

Question 14

What is the function of the basement membrane zone?

Answer 14

It anchors the epidermis to the dermis with the Retes ridges or Rete pegs which are protrusions of epidermis into the dermis. The height of these ridges tends to decline with age: 55% from 3rd to 9th decades of life.

Question 15

What is the dermis?

Answer 15

The dermis is the 2nd layer of the skin, below the epidermis. It is 2 mm - 4 mm thick. It is the bulkiness layer of the skin. It is vascularized and innervated.

Question 16

What are the major proteins in the dermis?

Answer 16

The major proteins in the dermis are collagen and elastin.

Question 17

What are the two different areas of the dermis?

Answer 17

Papillary dermis and Reticular dermis

Question 18

What is the papillary dermis?

Answer 18

The papillary dermis in the top portion of the dermis where the dermis interweaves with the rete ridges from the epidermis. The papillary dermis and the rete ridges combine to form the dermal papillae. In the dermal papillae, there is a small capillary loop which supplies oxygen and nutrients to the epidermis.
There are also pain touch receptors in the papillary dermis.

Question 19

What composed the papillary dermis?

Answer 19

The papillary dermis is composed of collagen and reticular fibers.

Question 20

What is the reticular dermis?

Answer 20

The reticular dermis is the lower portion of the dermis. It is composed of collagen and cutaneous blood vessels.

Question 21

What are the main dermal cells?

Answer 21

Fibroblast, Macrophages, Lymphocytes, Mast cells

Question 22

What are fibroblasts?

Answer 22

Fibroblasts are the main connective tissue cells. They synthesize collagen, elastin and other extracellular matrix proteins.

Question 23

What are macrophages?

Answer 23

The macrophages are monocytes that have differentiated and migrated into the tissues. They phagocytize bacteria and cellular debris and waste.

Question 24

What are lymphocytes?

Answer 24

Lymphocytes are white blood cells which help to mediate the immune response in the skin.

Question 25

What are mast cells?

Answer 25

Mast cells are effector cells in an allergic reaction. They are primarily distributed in the papillary dermis, near blood vessels and nerves. They are also involved in the presence of subacute and chronic inflammatory disease. They are a part of the skin immune system.

Question 26

What are the dermal appendages?

Answer 26

1. hair
2. sweat glands
3. sebaceous glands

Question 27

What are the proteins in the dermis?

Answer 27

The main protein in the dermis is collagen, primarily type I and to a lesser extent, type III

Question 28

What are the different types of collagen?

Answer 28

Type 1: found in tendons, ligaments, bones, skin
Type 2: found in cartilages
Type 3: found in arteries, intestines, uterus
Type 4: found in basement membranes

Question 29

What is the name of the layer below the dermis?

Answer 29

Hypodermis or Subcutaneous layer

Question 30

What is in the subcutaneous layer?

Answer 30

Subcutaneous fascia, subcutaneous fat.

Question 31

What is the function of the subcutaneous tissue?

Answer 31

The hypodermis provides insulation for the body and additional cushioning to the body. It is composed of loose connective tissue and fat cells. It is also a ready reserve source of energy.

Question 32

Which tissue requires the greatest demand for oxygen and thus the most sensitive to ischemia?

Answer 32

Muscle

Question 33

What does the blood supply to the skin come from?

Answer 33

The blood vessels are found in the subcutaneous layer and form a plexus just below the dermis. These give rise to another plexus that supplies the capillaries in the dermal papillae.

Question 34

What is the turnover time for the skin?

Answer 34

26 - 42 days

Question 35

How often is a complete epidermal renewal?

Answer 35

a complete epidermal renewal occurs about every 2 months

Question 36

What are the epidermal appendages?

Answer 36

Hair, nail, glands. These appendages start from the epidermis and extend into the dermis.

Question 37

What are the sebaceous glands?

Answer 37

The sebaceous glands are glands that secrete sebum into the hair follicles. The sebum is an oil that keeps skin moist and soft and acts as a barrier against foreign substances. The sebaceous glands are found in the skin in all parts of the body except for the palms of the hands and soles of the feet.

Question 38

What are the functions of hair?

Answer 38

Hair follicles are found everywhere except in the palms and the soles. Hair contributes to the regulation of body temperatures, enhancement of sensation and providing protection.

Question 39

What are eccrine and apocrine glands?

Answer 39

Eccrine glands produce sweat to help regulate body temperature and assist with the elimination of waste products. Apocrine glands produce thicker sweat, found in the axilla and pubic area, responsible for “body odor” when mixed with bacteria on the skin surface.