L06 - Skin as a major organ - WIP

Question 1

What are the 4 general classes of tissues of the body?

Answer 1

1. Epithelia
2. CT
3. Muscles
4. NS

Question 2

What factors can affect skin colour?

Answer 2

• Ethnicity
• Site of the body
• Exposure to radiation (UV)
• Drugs

Question 3

What factors can affect hairiness of the body?

Answer 3

• Site of the body
• gender
• Age
• Medical conditions (alopecia)

Question 4

What factors can affect the laxity of wrinkling of hair?

Answer 4

• Ethnicity
• -> affects hair colour
• -> character of hair (laxity/ wrinkling/ coiling)
• Site of anatomical location of hair can affect its laxity or coiling

Question 5

What are the two general types of skin?

Answer 5

1. Hairy skin (covers most of the body’s surfaces)

2. Glaborous skin (palms/ soles of feet)

Question 6

Functions of the skin?

Answer 6

• Protects against excessive water loss
• Barrier function
• Insulation
• Thermoregulation
• Sensation
• Synthesis of vitamin D
• Protection of vitamin B folates
• Psychosexual communication

Question 7

What are the 3 gross layers of the skin?

Answer 7

1. Epidermis - epithelial layer
2. Dermis - superficial CT layer
3. Hypodermis - deep CT layer

Question 8

What is the histological classification of epithelium of the skin?

Answer 8

Keratinised stratified squamous epithelium

Question 9

What are the different layers of the epidermis/

Answer 9

1. Stratum corneum (horny layer)
2. Stratum granulosum (granular layer)
3. Stratum spinosum (prickle cell layer)
4. Stratum basale (basal layer)

Question 10

Where does keratinocyte mitosis mainly occur in the epidermal layer?

Answer 10

In the basal layer

Question 11

Describe the movement of keratinocytes through the epidermis

Answer 11

1. Keratinocytes mitosis in basal laye
2. Daughter keratinocytes move upwards to form the prickle cell layer
3. Terminal differentiation begins in the prickle cell layer and keratinocytes lose their ability to divide
4. Keratinocytes synthesise keratin (heterodimeric fibrous proteins) which contribute to the strength of the epidermis

Question 12

What are prickle cells joined by?

Answer 12

Prickle like desmosomes (intercellular junctions)

Question 13

What happens to the keratinocytes in the granular layer of the epidermis?

Answer 13

• Keratinocytes lose their plasma membrane (PBL)
• Keratinocytes begin differentiating into corneocytes, the main cells of the stratum corenum
• Contains keratohyalin granules

Question 14

What are the main cells of the stratum corneum?

Answer 14

Corneocytes

Question 15

Keratohyalin granules are aggregations of…?

Answer 15

1. Keratins
2. Other fibrous proteins (e.g. involucrin, filaggrin)
3. Enxymes which
   - degrade the PBL (phospholipase)
   - cross link proteins including
   - filaggrin, which aggregates keratins
   - involucrin, which forms a major part of the corneocyte envelope

Question 16

What is the stratum corneum layer made up of?

Answer 16

Made up of layer of flattened corneocytes

- Major role in skin barrier function

Question 17

What is the approximate transit time of a keratinocyte from the basal layer to the stratum corneum?

Answer 17

30-40 days

Question 18

What are some cells other than keratinocytes which can be found in the epidermis?

Answer 18

1. Melanocytes

2. Langerhans cells

Question 19

What is the origin of melanocytes?

Answer 19

Dendritic cells of neural crest origin

Question 20

What is the origin of Langerhans cells?

Answer 20

Dendritic cells of bone marrow origin

Question 21

Where can melanocytes be found?

Answer 21

They occur at intervals along the basal layer of the epidermis

Question 22

Where can Langerhans cells be found?

Answer 22

Scattered throughout the prickle cell layer

Question 23

What is the function of melanocytes?

Answer 23

• Produce melanin, the main pigment that gives the skin its colour
• Produce more melanin but are not increased in number in black or tanned skin

Question 24

What is the function of Langerhans cells?

Answer 24

• Mediate immune reactions, e.g. allergic contact dermatitis
• Highly specialised capacity to present antigens to T lymphocytes

Question 25

What are some of the causes of acne?

Answer 25

• Abnormal differentiation of sebaceous gland ducts which become obstructed
• Infection with normally harmless skin bacteria
• Increased sebum production
• These changes in sebaceous glands occur at puberty

Question 26

Where are sebaceous glands most abundant?

Answer 26

On the face (typical site of acne)

Question 27

What is hyperhidrosis?

Answer 27

Increased sweating

• May affect only the palms and soles
• Wet hands/ feet
• Cause usually unknown