Anatomy and Function of Skin Flashcards
List the 4 layers of the skin.
What other 3 structures are found in the skin?
Epidermis
Basement membrane
Dermis
Subcutaneous tissue
Glands
Hair follicles
Capillaries
List the 4 layers of the epidermis, from outer to inner.
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
What is the embryological origin of the skin?
Ectoderm
Describe the embryological development of the skin. This occurs at 5 different stages.
Consider:
a) When are the skin layers formed?
b) How are additional skin structures formed?
c) Where do melanocytes come from?
Week 5:
-Single layer of cuboidal epithelium
Week 7:
- Periderm (single layer of squamous epithelium)
- Basal layer of cuboidal epithelium
Month 3:
- Epidermal proliferation into dermis forms hair follicles and sweat glands
- Cells in epithelial root sheath proliferate to form a sebaceous gland bud
Month 4:
- Periderm of squamous epithelium
- Intermediate layer of several cell layers
- Basal layer of cuboidal epithelium
Early foetal period:
-Melanoblasts invade epidermis from the neural crest
What is the normal pH of the skin?
Why?
pH 5.4
Presence of lactic acid, amino acids
What is the most important immune cell in the skin?
Where is it usually found?
Briefly describe its function.
Langerhans cells
Location: stratum basale
Function:
Antigen presentation to T cells in local lymph nodes
List the 3 functions of the skin.
Give 3 examples of each.
1. Protection, e.g. PHYSICAL: Mechnical impact Pressure IMMUNOLOGICAL: Micro-organisms
- Regulation, e.g.
Temperature
Fluid balance
Vitamin D - Sensation, e.g.
Temperature
Touch
Pain
Briefly describe the effects of UV light on the skin. (4)
- Direct cellular damage, e.g.
a. Photoaging
b. DNA damage
c. Carcinogenesis
d. Loss of normal protective function against UV - Altered immunological functions
- Impaired DNA repair
a. p53 mutations may lead to cancer - Long term skin changes
List 7 long term skin changes as a result of UV light damage.
Loss of skin elasticity Increased fragility of skin Abnormal pigmentation Haemorrhage of blood vessels Wrinkles Premature aging Easy bruising
List 5 types of receptor in the skin.
Consider their structure.
Encapsulated nerve endings:
- Meissner corpuscles
- Ruffini’s corpuscles
- Pacinian corpuscles
Free nerve endings:
- Merkel cells
- Free nerve endings
Consider the 3 types of encapsulated receptors in the skin. For each, what is its:
a) Location?
b) Function?
Meissner corpuscles
Location: below basement membrane
Function: light touch
Ruffini’s corpuscles
Location: dermis
Function: deep pressure; stretching
Pacinian corpuscles
Location: deep dermis
Function: deep touch; rapid deformation of skin; proprioception
Consider the 2 types of free nerve ending receptors in the skin. For each, what is their:
a) Location?
b) Function?
Merkel cells
Location: stratum basale
Function: gentle/localised pressure
Free nerve endings
Location: throughout skin
Function: pain; temperature
Describe the process of vitamin D synthesis in the skin. (2)
- Solar UBV photons are absorbed by 7-dehydrocholesterol in skin
a. This is converted to pre-vitamin D3 - Pre-vitamin D3 is converted into active vitamin D3 in the plasma membrane of skin cells
List 4 long term consequences associated with vitamin D deficiency.
Increased risk of common cancers
Increased risk of autoimmune disease
Increased risk of infectious disease
Increased risk of cardiovascular disease
Describe the process of allergy in the skin. (3)
- Irritants/allergenic compounds are taken up by Langerhans cells, which migrate to lymph nodes
- Langerhans cells present antigens to T cells
- T cells then mount an immune response against the allergen
What is the difference between initial exposure and repeat exposure in skin allergy?
Initial sensitisation: takes 10-14 days for a reaction to occur
Repeat exposure: reaction occurs within hours
