Clinical Lecture: Skin Histology

Question 1

What are the functions of the skin?

Answer 1

• Moisture control
  
  • Barrier to Pathogens
  • Barrier to UV
  • Metabolic function e.g. Vitamin D synthesis
  • Thermoregulation
  • Sensory Organ
  • Rapid repair of injuries

Question 2

What are the 3 main layers of the skin?

Answer 2

• The epidermis is a continuously proliferating stratified squamous epithelium that produces keratin. It is direct contact with the outside. There are no blood vessels and it is constantly being spared.
  
  • The dermis is split into a papillary dermis and a reticular dermis. It is made up of fibrous and fibro adipose tissue that supports the epidermis. It contains blood vessels, nerves and sensory receptors. There are also muscles
  • The subcutis is largely made of adipose tissue, supporting fibrous bands and large blood vessels

Question 3

What are the layers of the epidermis?

Answer 3

1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidem - found only in thick skin such as the sole of the foot and the palms
5. Startum Corenum

Question 4

Give examples of the cells in the epidermis?

Answer 4

• Keratinocytes
  
  • Melanocytes - produce keratin. Have an irregular nucleus.
  • Langerhans cells - are intraepidermal antigen presenting cells (histocytes); Seen in all levels of the epidermis but are most noticeable in the prickle cell layer; they are also in the dermis; they particularly cluster around small blood vessels

Question 5

Give examples of skin appendages.

Answer 5

• Sebaceous glands - secrete sebum. Two types associated wit hair follicles- ones that secrete into the hair follicle and one that secrete directly onto the skin
  - Hair follicles - start in subcutaneous tissue through the dermis and epidermis. Made of a bulb, follicle and shaft
  - Arrector pilli muscles - function is to make the hair stand on end or lay down flat
  - Eccrine gland - thermoregulatory function and produce sweat
  - Apocrine gland - have a function in producing odours

Question 6

What is the function of a Meissner corpuscle?

Answer 6

Found in the papillary dermis (beneath the epidermis)and detect touch and vibration. They are fast adapting. Small encapsulated encapsulated receptors found in the papillary dermis of they finger tips, sole of the feet, nipples, eyelids, lips and genitalia

Question 7

What is the function of a Pacinian corpuscle?

Answer 7

Pacinian corpuscle - large encapsulated sensory receptors found in the deep layer of the skin, ligaments and joint capsules. They are responsive to pressure, coarse touch and rapid vibrations. They are fast adapting.

Each lamellae is composed to flatten Schwann cells and endoneural fibroblasts. There is fluid between each layer and delicate collagen layers and occasional capillaries.

Question 8

What is a Merkel cell?

Answer 8

• They are associated with a an myelinated nerve forming a Merkle cell neurite complex.
• hey are commonly found in innervated clusters around hair follicles. These cells are thought to function as slowly adapting mechanoreceptors that mediate the senses of touch and hair movement.
• Intraepidermal receptors for touch
• They are rounded without processes
• Found in the basal layer of the dermis

Question 9

What are Ruffin’s endings?

Answer 9

Ruffini endings are slow adapting, encapsulated receptors that respond to skin stretch and are present in both the glabrous and hairy skin.

Question 10

What is the difference between a first, second and third degree burn?

Answer 10

First degree burn is a superficial burn that only affects the epidermis. It does not extend into the dermis or subcutis. It is painful and do resolve quickly. An example is sun burn - thermal injury from the sun.

		Second degree burn - the epidermis is lost. The burn has travelled through into the dermis. Depending how deep it goes depends on how painful it is. Partial thickness burn. 

		Third degree burns most serious in terms of sickness. It has travelled all the way through the epidermis and dermis. It gets more superficial towards the end. It is a full-thickness burn. It jay not be painful and there may be damaged nerve fibres and pain fibres. This can be serious as patients may underestimate the damage.