Week 4 Skin, epithelium & connective tissue Flashcards
3 Layers of skin
- Epidermis - stratified epithelium
- Dermis - connective tissue
- Subcutis - fat
4 Layers of epidermis
- Stratum Corneum
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basale
3 Importance of the dermo-epidermal junction (DEJ)
- Adhesion
- Cellular migration
- Cellular signalling
What are the 2 major protein fibres in dermis? What are their main functions?
- Collagen - tensile strength
2. Elastin - Elasticity
Main functions of the subcutis layer
- Energy reserve (adipose tissue)
- Cushion effect
- Insulation
4 Classes of pilosebaceous unit and their locations
- Terminal - scalp, beard
- Vellus - majority of skin
- Apopilosebaceous - axilla, groin
- Sebaceous - face, chest, back
3 phases of cyclical hair growth
- Anagen - growing
- Catagen - regressing
- Telogen - resting (hair shedding occurs)
What is the type of skin that doesn’t contain any pilosebaceous unit? Characteristics? Example?
Glabrous skin
- non-hair bearing
- lack of hair follicles and sebaceous gland
e. g. palm, sole
Characteristics of sebaceous gland
- Large and well-developed in fetus
- size rapidly reduced after birth
- Regain of function at puberty
2 Types of sweat glands
- Eccrine - entire body surface
2. Apocrine - axilla, genitalia, mammary areas
2 Types of perspiration
- Insensible perspiration - passive evaporation from skin surface
- Active sweating - mainly through eccrine glands
4 Functions of nail
- Mechanical protection
- Enhance sensory discrimination
- Dexterity (scratching/grooming)
- Cosmetic accessory
What are the skin appendages?
- Hair
- Nail
- Adnexal structures - pilosebaceous unit, eccrine glands, apocrine glands
4 Components of the pilosebaceous unit
- Hair shaft
- Hair follicle
- Sebaceous gland
- Arrector pili muscle
Origin of skin (development)
Ectoderm: nervous system, epidermis
Mesoderm: dermis, skin appendages
7 Functions of skin
- Mechanical barrier
- UV protection
- Thermoregulation
- IMmunity
- Sensation - innate + adaptive
- Endocrine - production of vitamin D
- Communication
6 Functions of epithelium
- Cover surfaces and cavities of body2
- Protection
- Secretion
- Absorption (e.g. digestive epithelium)
- Transport
- Sensory
5 Common properties of epithelium
- Avascular
- Little/no intercellular matrix
- Junctional structures
- Rest on basement membrane
- Contains cytokeratin
What is the basement membrane made up of?
Basal lamina (type IV collagen) + Reticular lamina (type I collagen)
2 types of special epithelia
- Pseudostratified ciliated columnar epithelium with globet cells (in respiratory epithelium)
- Transitional epithelium - allow changes in shape
(e. g. in bladder)
Special types of simple epithelium (single layer)
- Mesothelium: lining of pleural and abdominal cavities, surfaces of internal organs
- Endothelium: lining of all blood vessels and lymphatics
Specializations at different surfaces of epithelium
- Apical surface: microvilli / cilia
- Lateral surface: junctional complex
- Basal surface: adhesion to basal lamina/anchoring junction(actin or hemidesmosomes)/basal membrane infolding (interdigitation)
What is a single cell gland? Where is it found?
Goblet cell
found in tracheal and intestinal epithelium
3 Modes of secretion
- Merocrine
- Apocrine
- Holocrine
5 types of exocrine glands
- Simple tubular
- Simple coiled tubular
- Simple branched tubular
- Simple branched acinar
- Compound tubuloacinar
5 Main functions of connective tissue
- Support epithelium
- Protection
- Connect tissues/organs
- Tissue repair
- Extracellular matrix is important in regulating behaviour in cells
What is the extracellular matrix (ECM) of connective tissue composed of?
- Ground substance
2. Fibrous components
What makes up the gel-like ground substance of connective tissue?
- Proteoglycans
2. Glycoproteins
3 Types of fibers in ECM of connective tissue
- Collagen fibers (type I collagen)
- Elastic fibers (elastin)
- Reticular fibers (type III collagen)
3 Broad types of connective tissue
- Connective tissue proper
- Specialized connective tissue (e.g. adipose tissue, blood, lymphatics, cartilage, bone)
- Embryonic connective tissue
3 criteria for classification of connective tissue`
1. Abundance of fibers: loose/dense 2. Arrangement of fibers: irregular/regular 3. Nature of fibers: white (collagen) / yellow (elastin)
6 Common types of cells found in connective tissue and their functions
- Fibroblasts: synthesize fibres and ground substance
- Macrophages: phagocytosis
- Plasma cells: antibody production
- Mast cells: release histamine
- Fat cells: storage of fat
- Leukocytes: defense
2 types of adipose tissue
- Unilocular adipose tissue (white) - 1 large fat vacuole, common in adults
- Multiocular adipose tissue (brown) - several fat vacuoles in each cell, important for baby
3 types of specialized connective tissues
- Cartilage and bone
- Adipose
- Haemopoietic tissue