Week 4 - Tissues of the body Flashcards
What makes up the cell cytoskeleton?
- Actin microfilaments
- Microtubules
- Intermmediate filaments
What are actin microfilaments?
Polar, double stranded helical array of G actin (7nm diameter)
What are microtubules in cell cytoskeleton?
Dimers of alpha and beta tubulin arraged as hollow cylinders (25nm diameter)
Require MTOC for assembly
What are intermmediate filaments?
Rope-like twisted fibres of various proteins (10nm diameter)
What are all of these parts?
What are centrioles?
Groupings of microtubules arranged in 9 + 0 pattern
Organise assembly of microtubules which help movement of chromosomes during cell division
What are the properties of tight junctions (zona occludens)?
- Pentalaminar (5 layered)
- Continuous line of intramembranous particles (occludins, claudins, junctional adhesion molecule (JAM)
- Prevent movement of membrane from apical surface to lateral cell surface
- Limit movement of water and molecules through intercellular space
What are the properties of adherent junctions (zona adherens)?
- 20nm gap
- Cell adhesion molecules (cadherins, integrins, selectins, immunoglobulin superfamily)
- Provide mechanical stability by linking cytoskeleton of adjacent cells
What are the properties of desmosomes (macula adherens)?
- 20nm gap
- Discoid
- Desmocollin and desmoglein between cells
- Intracellular attachment plaques
- Link to intermediate filaments in cytoplasm
- Perpendicular to basement membrane
What are the properties of hemidesmosomes?
Face basement membrane
What are the properties of gap junctions (communicating junction)?
- Allow direct communication between adjacent cells
- Allow passage of ions, AA’s, sugars, secon messengers and metabolites
- Permits coordinated cell activity
- Made of pretieins (connexions) which assemble into channels (connexons)
What are the properties of ground substance?
- Occupies large volume for small mass
- Hydrophilic
- GAGs (glycosaminoglycans)
- Acidic
- Negatively charged hydroxyl, carboxyl and sulphydryl groups
What are the 3 types of fibrous molecules and their properties?
Collagen
- Tensile strength
- Secreted as tropocollagen and extracellularly polymerised to form collagen
Reticulin
- Type 3 collagen - branched
Elastin
- Stretch and elastic recoil
- Tropoelastin polymerises to elastin
- Requires fibrillin for assembly
What are the 2 different types of structural glycoproteins and their properties?
Filamentous
- Fibrillin (microfibrils 8-12nm) - links to elastin
- Fibronectin - deposition and orientation of collagen and its links to cells via integrin
Non-filamentous (links cells and ECM)
- Laminin - major basement membrane component
- Entactin - binds laminin to type 4 collagen
- Tenascin - binds to integrins
What separates epithelia from underlying ECM?
Basement membranes
What are the 3 surface specialisations of epithelia?
- Ciliated
- Microvilli
- Keratinised
What are the 4 different shapes of epithelial cells?
- Squamous
- Cuboidal
- Columnar
- Transitional
What are the 3 different layer types of epithelia?
- Simple
- Stratified
- Pseudostratified
Where are simple squamous epithelial cells found?
Terminal air sacs and part of kidney tubules
Where are simple squamous mesothelial cells found?
Linings of body cavities and covering organs within
Where are simple squamous endothelial cells found?
Lining of blood vessels and lymphatics
What are the properties of stratified squamous cells?
May be keratinised or non-keratinised
Where are stratified cuboidal cells found?
Some dubts of sweat glands
Where are stratified columnar cells found?
Ducts of mammary glands and larger ducts of salivary glands
Where are simple cuboidal cells found?
Many glands and portions of their ducts
Where are simple columnar cells found?
Gall bladder, surface of stomach, uterus and oviduct
Where is transitional eputhelium found?
Urinary tract, pelvis of kidney, ureter, bladder and part of urethra
Where are pseudostratified ciliated columnar epithelial cells found?
Respiratory passages to bronchioles, male reproductive tract from efferent ducts to vas deferens
What is the funciton of simple epithelia?
Absorption
What is the function of stratified epithelium?
Protective
What are other functions of epithelium?
- Secretion
- Sensory perception
- Movement of materials
- Wound repair
What are the properties of microvilli?
- Apical plasma membrane
- Increase surface area
- Core of microfilaments
- Anchored in terminal web
What are the properties of cilia?
- Apical surface
- Very numerous
- Transport material across surface
- Microtubules
What are the properties of stereocilia?
- Non-motile
- Microfilament core - modified microvilli
What is the function of basal infoldings?
Increase surface area
What are exocrine glands?
Secrete out of body via ducts
What are endocrine glands?
Do not have ducts but secrete directly into the body, into blood capillaries
How can exocrine glands be classified?
- Tubular
- Acinar
- Tubulo-acinar
- Simple
- Compound
What are the different types of secretions from serous, mucous and mixed glands?
Serous = watery fluid
Mucous = more viscous containing mucin
Mixed = micture of serous and mucous fluids
What are eccrine glands?
Glandular cells aren’t injured upon secretion
How do apocrine glands work?
- Secretion gathers at outer apical end of secretory cell
- Is pinched off with a portion of the cellcytoplasm
- Most of cell is unaffected
- Cycle repeats after refractory period
How do holocrine glands work?
- Accumulation of secretion within cell cytoplasm
- Cells die
- Dead cells dischargedwith secretion contained in them
How do endocrine cells store their products?
- Intracellular storage
- In form of intracytoplasmic storage granules
- Secreted directly into blood capillaries
- Extracellular storage
- Within an intercellular follicle surrounded by secretory cells
- Secretes into follicle
- Re-uptake into cytoplasm
- Secretion into capillaries in contact with basal ends of secretory cells
What is the function of the basement membrane?
- Controls spread of disease and infection
- Boundary between epithelia (basal lamina), muscle and nerve (external lamina) and connective (support) tissue
- Condensed layer of ECM
- Impenetrable barrier but permits flwo of nutrients and metabolites (molecular sieve)
- Constituents = heparan sulphate, type 4 collagen, fibronectin, laminin, enactin
What are the characteristic of connective tissue?
- Cells often separated by ECM
- Contains blood vessels and nerves
- Cells may communicate
- Cells often have slow turnover
- Cells interact with ECm (adhesion molecules)
What is the most important cell in connective tissue?
Fibroblasts
What cells are derived from mesenchyme?
- Fibroblasts (responsible from synthesis and maintenance of ECM)
- Adipocytes
- Defence cells
How do you classify connective tissue?
- Mesenchyme (embryonic)
- Loose areolar
- Dense (mechanical support) –> iregular or regular
- Reticular
- Adipose
What are connective tissue diseases example?
- Elhers-Danlos syndrome
- Marfans syndrome
- Scurvy
- Homocystinuria
- Mucopolysaccharidoses
- Fibroma
What are the components of cartilage?
- Ground substance
- Fibres
- Type 2 collagen - hyaline cartilage
- Type 2 + 1 collagen - fibrocartilage
- Type 2 + elastic - elastic cartilage
- Chondroblasts (secrete matrix)
- Chondrocytes (maintain matrix)
How is cartilaged maintained and grown?
- Matrix permeable to water
- Delivers oxygen and nutrients
- Waste products removed
- Mainly non-vascular
- Relies on diffusion
- Grows by intersaitital and appositional growth
What are the 3 types of cartilage and their properties?
- Hyaline
- Articular surfaces, tracheal rings etc.
- Fibrocartilage
- Intervertebral discs, pubic symphysis
- Elastic cartilage
- External ear, auditory canal, epiglottis etc.
