lecture 6: epithelial cell surface specialisations

cytoskeleton

• Actin/microfilaments

  • Found in the periphery of the cell

  • At the plasma membrane

  • When 2 cells divide (undergoing mitosis) --> cytokinesis

  • Found in the surface specialisations

  • Found in some cells e.g. muscle cells; skeletal and caridean muscles cells actin and myosin come together to form sarcomeres(contractile units)

• Microtubules

  • Surface specialisations

  • Cells undergoing mitosis (forms the mitotic spindle and at the centromeres)

• Intermediate filaments

  • Around the nucleus

  • Skin cells

microtubules

cilia

• Surface specialisation on eppithelial cells

• Ovaduct

• Fallopian tube

• Trachea

• One cilium is composed of cytoskeleton (inside the epithial lians)

• Cilia is made up of microtubules

• Image above shows transverse cross sections

• About 10 microns in length

• Microtubles/cilia come up through the plasma membrane to create the increase SA to V ratio

• Point; movement

• They sweep

• 9 + 2 microtubule doublet arrangement

electron micrograph

cilia light micrograph

• Pseudo stratified as all the epithelial cells touch the basement membrane

cilia florescence microscopy image

• Actin is on the periphery of the cell therefore actin is the red in the image;  keeps the integrity of the cell

• Microtubules present as well

• Nucleus is in the middle

actin microfilaments; electron micrograph

• Shows a small part of one cell

• 4 cells in this electron micrograph

• Cytoskeleton is highly organised to the periphery of the cell

• 1 micron in length

• Forms little fingers at the edge of the cell

• Actin microfilaments stick into the plasma membrane of the cell; forming microvilli

• Microvilli create large surface area to volume ratio

• Places where you would find lots of microvilli;

  • Small intestine; simple columnar epithelial cell with microvilli allowing for the absorption of food

actin microfilaments

• Proximal convolute tubule of the kidney

• Needs lots and lots of absorption

• Needs to reabsorb 70% of the plasma ultrafiltrate that gets filtered through the glomerulus back to the body

• If the microvilli didn’t work we would loose all of our blood and filtrate and water to our urine

• We can see the microvilli in the 'brush border'

• The carbohydrates that are studded into the membrane are picking up the colour on the stain (pink circular area surrounding the lumen)

trachea

• Sits posterior to the esophagus

• Purple is the thick band of purple

• Epithelium is the cells lining the trachea

• Simple, columnar cells with cilia

• Pseudostratified epithelium

• cilia sweeps the mucus up