Histology Flashcards
What colour do nerve cells stain?
Brown
What colour dye is haematoxylin?
Blue
What colour dye is eosin?
Pink
How is tissue preserved?
First preserved by fixing it in formalin which is an aqueous solution of the gas formaldehyde, this prevents the tissue from rotting.
The samples of tissue to be examined are then embedded in paraffin, a process which involves the extraction of water and a number of other substances from the tissues
How thick are the tissue slices typically?
4 microns
What do you do to examine bone?
Demineralise it, so that you can produce thin sections
Or grind it down to produce a thick slice
What substances within tissues don’t stain?
Glycosaminoglycan extra-cellular jelly
What stain is used to highlight sugars?
Periodic Acid Schiff (PAS)
What colour is the stain of PAS?
Magenta
What stain is used to highlight elastic tissue?
Van Gieson
What colour does Van Gieson stain?
Brown
What stain is used to highlight mucins?
Alcian blue
What colour does Alcian blue stain?
Blue
What size are lymphocytes?
About 10 micrometers in diameter, with very little cytoplasm
What size are motor neurons?
About 100 micrometers wide, with axons up to 1 meter in length
Different shapes of cells …
Spherical/Rounded
Polygonal
Fusiform
Squamous (flattened)
Cuboidal
Columnar
Which cells are generally smaller, dormant/metabolically inactive cells or metabolically active cells and why?
A dormant cell, as they do not need to maintain an elaborate cellular mechanical machinery in order to exist, it only needs a small number of mitochondria, little endoplasmic reticulum.
What do metabolically active cells often contain?
Nucleoli, which are specialisations within the nucleus of the cell and are sites of DNA transcription into RNA
What is the lifespan of the cells that line your intestines?
Several days, probably around 4-5 days
What is the lifespan of red blood cells?
120 days before they are removed
What is the lifespan of cells of your skin and connective tissues?
About a few months
What is the lifespan of cells that make up bones and tendons?
Years
What is the lifespan of skeletal muscle cells?
They have limited regeneration, they last most of your adult life
Which cells have almost no capacity to regenerate?
Nerves
Brain
Cardiac muscle (heart)
Stem cells of germ cells
How big is the nucleolus?
1-3 microns in diameter
What is euchromatin?
Lighter areas
What is heterochromatin?
Darker areas
What is mitochondria?
Organelle which is the site of oxidative phosphorylation and other biochemical processes
Have their own DNA
Have a double membrane, outer membrane is smooth,
inner membrane is a complex series of folds called cristae
Where is the mitochondrial matrix found?
Between the folds of the inner membrane
What occurs in the outer mitochondrial membrane?
Lipid synthesis
Fatty acid metabolism
What occurs in the inner mitochondrial membrane?
Respiratory chain
ATP production
What occurs at the mitochondrial matrix?
Krebs cycle
What occurs at the mitochondrial inter-membranous space?
Nucleotide phosphorylation (conversion of ADP to ATP)
What does the rough endoplasmic reticulum do?
Assembles proteins
Site of protein synthesis
Highly folded flattened membrane sheets studded with ribosomes
What does the smooth endoplasmic reticulum do?
Site of membrane lipid synthesis
Site where synthesised proteins are processed
Highly folded flattened membrane sheets, without ribosomes
What is the Golgi apparatus?
Series of parallel stacks of membranes
Site at which macromolecules that have been synthesised in the ER are processed and stored
Frequently not visible on light microscopy, but plasma cells have a very visible Golgi apparatus
What are plasma cells?
Activated b-lymphocytes
Produce antibodies
Nucleus is located towards the edge of the cell (eccentric nucleus)
Prominent pattern of enchomatin and heterochromatin
Pale area near the nucleus known as perinuclear hoff which is the Golgi apparatus of the plasma cell
What does the cis-face of the Golgi apparatus do?
Receives transport vesicles from the SER and phosphorylates some proteins
What does the medial Golgi do?
Forms complex oligosaccharides by adding sugars to lipids and peptides
What does the trans Golgi network do?
Site of proteolysis
Site in which macromolecules are sorted into vesicles which bud from the surface
What are vesicles?
Very small spherical membrane-bound organelles used by cells for transport of materials, storage and exchanging cell membrane between different compartments within the cell
What are lysosomes?
Derived from the Golgi apparatus
Site at which proteins are degraded
Formed by the fusion of two vesicles, hydrolase vesicles which contain the enzymes that can degrade proteins at a low pH and endosomes which bear a hydrogen ATPase on their membrane, pumps hydrogen ions into the reside lowering its internal pH
Insion of these two vesicles produces an endolysosome, in which there is both the ability to lower the pH and
enzymes which can degrade proteins at low pH
What occurs to protect the cell from lysosomes?
Spatial separation between enzymes which lower pH and enzymes which degrade proteins at a low pH
What are peroxisomes?
Very small vesicles, generally 0.5 microns in diameter
They contain enzymes which oxidise long chain fatty acids
What is the cytoskeleton?
Supports the cells shape
Contains microfilements (5mm in diameter) and made of actin
What is actin?
Present in cells as a globular g-protein, polymerises into filamentous f-actin
Forms a bracing mesh underneath the cell membrane to maintain the cells shape
When cells divide a mesh work of microtubules formed from tubulin develops and is used to act as a scaffold for chromosomes during mitosis and meiosis
In what cell can’t tubulin proteins be found in?
Erythrocytes, as they don’t divide
What are intermediate filaments?
10nm diameter
Anchored to transmembrane proteins
Intermediate filaments spread tensile forces through the tissues
Where are cytokeratins commonly found?
Epithelial cells
Where is desmin commonly found?
Myocytes (muscles)
Where are glial fibrillary acidic protein commonly said?
Astrocytic glial cells
Where are neurofilament proteins commonly found?
Neurons
Where are nuclear laminar commonly found?
Nuclei of all cells
Where is vimentin commonly found?
Mesodermal cells
What is lipofuscin?
Membrane bound orange-brown pigment
Formed as a result of peroxidation of lipids in older cells
Commonly fond in hearts and livers of older patients
What are lipids?
Accumulates in cells with non-membrane-bound vacuoles
Appear as empty white spaces in cells
Normally found accumulating in adipocytes or fat cells, abnormally found in the liver
What is interstitial fluid made of?
Water
Salts in solution
Range of different peptides and proteins
What is extracellular solid material made of?
Fibrillar proteins (collagen or elastin)
Glycosaminoglycan jelly
Inorganic salts such as calcium accumulate
What is a chromatin?
Nuclear DNA + Proteins
