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Study Notes

Histology is the science of microscopic study of normal body tissues.
It studies normal tissues to understand diseased cells.
Normal tissues and diseased ones are studied in pathology.
The building blocks of a living organism are cells.
Cells grouped together form tissues.
Tissues combined make organs.
Organs and systems form whole organisms.
Microscopes are needed to study cells as they cannot be seen with the naked eye.
There are two main types of microscopy: light microscopy and electron microscopy.

Magnification power refers to the ability to enlarge an image.
The human eye has zero magnification.
Resolution power is the smallest distance between two points that can be distinguished as separate.
The resolution power of the human eye is 0.2 mm
Light microscopes have a magnification power of up to 1500 times and resolution of 0.2 micrometers.
Electron Microscopes have a much higher magnification power (up to 150,000 times) and resolution (0.2 nanometers).

Tissues are typically uncolored (colorless) when viewed under light microscopes.
Special stains are used to visualize and differentiate structures within tissues.
Hematoxylin (H) is a basic stain that stains acidic structures blue.
Eosin (E) is an acidic stain that stains basic structures pink or red.
Staining mixes like H&E are used to produce a variety of colors.
Special stains target particular structures not visible with H&E.

The cell membrane, also known as the plasma membrane or plasmalemma, is a thin structure that encloses the cell.
Its thickness is 8-10 nanometers.
Viewed through a light microscope it appears as a thin line.
Viewed through an electron microscope it appears as a trilaminar structure with three layers.
It consists of phospholipids, proteins, and carbohydrates.
Phospholipids have a hydrophilic head and hydrophobic tails, forming a bilayer.
Proteins can be integral (embedded in the membrane) or peripheral (attached to the membrane).
Carbohydrates are attached to proteins (glycoproteins) or lipids (glycolipids) and form the glycocalyx.

Cholesterol is a lipid molecule that is incorporated into the lipid bilayer.
It helps stabilize the membrane and regulate its fluidity at varying temperatures.

Membrane proteins have various functions, including transport, signaling, and structural roles.
Types of membrane proteins include integral, peripheral, and transmembrane proteins.
Integral proteins are embedded in the membrane.
Peripheral proteins are loosely attached to the membrane.
Transmembrane proteins extend across the entire membrane.

The ER is a network of membrane channels extending throughout the cytoplasm.
It is categorized into smooth and rough ER, distinguished by the presence or absence of ribosomes.
Rough ER has ribosomes on its surface responsible for protein synthesis.
Smooth ER lacks ribosomes and is involved in lipid synthesis, detoxification, and calcium storage.