Cells and Tissues
Learning Objectives:
o Describe the composition of the cell membrane and correlate it with its function
o Describe the ultrastructure of eukaryotic cell organelles and correlate with their locations, morphologies, and functions
o Name and identify three cellular inclusions
o Describe the ultrastructural morphologies and makeup of three cytoskeletal fiber types
o Name the four main tissue types
Iowa Virtual Slidebox: Liver (466)
Start at low or moderate magnification on your microscope or digital slide. Look for small circular blue or purple structures within the broader pink background. What are these? Can you see a membrane encircling these structures?
These purple (basophilic) structures are nuclei within the pink (eosinophilic) liver cell (hepatocyte). You can see the border of the nuclear membrane in these hepatocytes. Additionally, you can see the cell membrane of the hepatocyte itself!
Zoom in through successive objectives until you reach 40x. Zoom in on one nucleus. You may have to zoom in to several before finding denser blue patch within the purple circle. What is this? Why is it denser? What does the presence of this structure tell you about the activity of this cell?
This is the nucleolus. Its presence means that this cell is actively transcribing DNA into RNA. The presence of a nucleolus means that a cell is actively producing proteins.
Clinical Correlation: What might the presence of a nucleolus in a cell that does not normally have one tell you about that cell?
This might suggest that a cell that does not normally produce proteins is doing so – for example, in a tumor cell, a nucleolus indicates activity.
SLU Slide 40: Pancreas
Iowa Virtual Slidebox: Pancreas (1463)
Start at low magnification, eventually moving up to 10x. Look at a secretory cell and notice its stratified color. What might this stratification tell you about the composition of the cell? Do you see any other cells within this preparation that are darker, but not stratified? What does that indicate about their concentration of that same cellular structure?
Stratification in color indicates that part of the cell is basophilic (more acidic) and the other part is acidophilic (more basic). In this case, the apical surface of the cells secrete a fluid rich in bicarbonate, which is secreted into the duodenum and neutralizes stomach acid. Cells that lack this stratification in color may not have the same function as the stratified cells (indeed, in the pancreas, there are exocrine cells that secrete digestive enzymes, and endocrine cells that secrete hormones into the blood).
No Slide:
Clinical Correlation: Necrosis is a pathological type of cell death that results from severe damage to cellular and organelle membrane. Can you think of a particular membrane within the cell that, if damaged, will result in further damage to cellular contents?
Damage to the lysosomal membrane will result in the release of enzymes into the cytoplasm which will lyse cytoplasmic proteins.
The relative amounts of organelles within a cell can give some indication of that cell’s major function within the body. For example, pancreatic Beta cells have an abundance of juxtanuclear golgi complexes and a moderate amount of rough endoplasmic reticulum. Based on what the Golgi apparatus and rER do within a cell, what can be inferred about the function of a Beta cell?
The arrangement of the Golgi apparatus (which packages proteins into membrane-bound vesicles) and rER (where proteins are assembled by ribosomes and then transported through the cell) indicates that the Beta cells are actively producing proteins for extracellular release.