L06 - Skin as a major organ - WIP Flashcards
- Look at slides for histoloty - Draw pilosebaceous unit
What are the 4 general classes of tissues of the body?
- Epithelia
- CT
- Muscles
- NS
What factors can affect skin colour?
- Ethnicity
- Site of the body
- Exposure to radiation (UV)
- Drugs
What factors can affect hairiness of the body?
- Site of the body
- gender
- Age
- Medical conditions (alopecia)
What factors can affect the laxity of wrinkling of hair?
- Ethnicity
- -> affects hair colour
- -> character of hair (laxity/ wrinkling/ coiling)
- Site of anatomical location of hair can affect its laxity or coiling
What are the two general types of skin?
- Hairy skin (covers most of the body’s surfaces)
2. Glaborous skin (palms/ soles of feet)
Functions of the skin?
- Protects against excessive water loss
- Barrier function
- Insulation
- Thermoregulation
- Sensation
- Synthesis of vitamin D
- Protection of vitamin B folates
- Psychosexual communication
What are the 3 gross layers of the skin?
- Epidermis - epithelial layer
- Dermis - superficial CT layer
- Hypodermis - deep CT layer
What is the histological classification of epithelium of the skin?
Keratinised stratified squamous epithelium
What are the different layers of the epidermis/
- Stratum corneum (horny layer)
- Stratum granulosum (granular layer)
- Stratum spinosum (prickle cell layer)
- Stratum basale (basal layer)
Where does keratinocyte mitosis mainly occur in the epidermal layer?
In the basal layer
Describe the movement of keratinocytes through the epidermis
- Keratinocytes mitosis in basal laye
- Daughter keratinocytes move upwards to form the prickle cell layer
- Terminal differentiation begins in the prickle cell layer and keratinocytes lose their ability to divide
- Keratinocytes synthesise keratin (heterodimeric fibrous proteins) which contribute to the strength of the epidermis
What are prickle cells joined by?
Prickle like desmosomes (intercellular junctions)
What happens to the keratinocytes in the granular layer of the epidermis?
- Keratinocytes lose their plasma membrane (PBL)
- Keratinocytes begin differentiating into corneocytes, the main cells of the stratum corenum
- Contains keratohyalin granules
What are the main cells of the stratum corneum?
Corneocytes
Keratohyalin granules are aggregations of…?
- Keratins
- Other fibrous proteins (e.g. involucrin, filaggrin)
- Enxymes which
- degrade the PBL (phospholipase)
- cross link proteins including
- filaggrin, which aggregates keratins
- involucrin, which forms a major part of the corneocyte envelope
What is the stratum corneum layer made up of?
Made up of layer of flattened corneocytes
- Major role in skin barrier function
What is the approximate transit time of a keratinocyte from the basal layer to the stratum corneum?
30-40 days
What are some cells other than keratinocytes which can be found in the epidermis?
- Melanocytes
2. Langerhans cells
What is the origin of melanocytes?
Dendritic cells of neural crest origin
What is the origin of Langerhans cells?
Dendritic cells of bone marrow origin
Where can melanocytes be found?
They occur at intervals along the basal layer of the epidermis
Where can Langerhans cells be found?
Scattered throughout the prickle cell layer
What is the function of melanocytes?
- 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
What is the function of Langerhans cells?
- Mediate immune reactions, e.g. allergic contact dermatitis
- Highly specialised capacity to present antigens to T lymphocytes
What are some of the causes of acne?
- 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
Where are sebaceous glands most abundant?
On the face (typical site of acne)
What is hyperhidrosis?
Increased sweating
- May affect only the palms and soles
- Wet hands/ feet
- Cause usually unknown
