Microscopy and Cell Structure: Study Notes for Anatomy & Physiology

Microscopy in Anatomy & Physiology

Microscope Parts and Their Functions

The microscope is an essential tool in anatomy and physiology for observing cells and tissues at high magnification. Understanding its components and their functions is crucial for accurate laboratory work.

• Arm: Supports the tube and connects it to the base.

• Base: The bottom support of the microscope.

• Condenser unit (and knob): Focuses light onto the specimen.

• Course focus knob: Moves the stage up and down for general focusing.

• Fine focus knob: Allows precise focusing after using the coarse knob.

• Illuminator (and on/off or power switch): Provides the light source.

• Iris diaphragm (and lever): Adjusts the amount of light reaching the specimen.

• Mechanical stage control knobs: Move the slide on the stage.

• Objective lens: Magnifies the specimen (may be scanning, low, or high power).

• Ocular (eyepiece): The lens you look through, usually 10x magnification.

• Rheostat (dimmer switch): Adjusts light intensity.

• Rotating nose piece: Holds and rotates objective lenses.

• Stage: Platform where the slide is placed.

Microscope Calculations and Usage

Proper use of the microscope involves understanding magnification and field of view.

• Total Magnification: Calculated by multiplying the objective lens power by the ocular lens power. Formula: $\text{Total Magnification} = \text{Objective Lens Magnification} \times \text{Ocular Lens Magnification}$

• Field of View: The visible area when looking through the microscope; decreases as magnification increases.

• Depth of Field: The thickness of the specimen that is in focus at one time.

• Working Distance: The distance between the objective lens and the specimen.

Microscope Lab Activity

Students should be able to identify all parts of the microscope on a diagram and explain their functions. Practice calculating total magnification and understanding how field of view and depth of field change with different lenses.

Cell Structure and Organelles

Overview of Cell Organelles

Cells contain specialized structures called organelles, each with distinct functions necessary for cell survival and activity.

• Centrosome (contains a pair of Centrioles): Organizes microtubules during cell division.

• Chromatin: DNA and protein complex; condenses to form chromosomes during cell division.

• Cilia: Hair-like projections for movement or sensing the environment.

• Cytosol: Fluid portion of the cytoplasm.

• Cytoskeleton: Network of protein filaments for cell shape and movement.

• Flagella: Long, whip-like structures for cell movement.

• Golgi Body (Golgi Apparatus): Modifies, sorts, and packages proteins and lipids.

• Lysosomes: Contain digestive enzymes for breaking down waste.

• Microvilli: Increase surface area for absorption.

• Mitochondria: Produce ATP, the cell’s energy currency.

• Nucleolus: Site of ribosome synthesis within the nucleus.

• Nuclear envelope: Double membrane surrounding the nucleus.

• Nuclear pore: Openings in the nuclear envelope for transport.

• Nucleus: Contains genetic material (DNA); controls cell activities.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

• Plasma membrane (cell membrane): Regulates entry and exit of substances.

• Ribosomes (free or bound): Synthesize proteins.

• Rough Endoplasmic Reticulum: Studded with ribosomes; synthesizes proteins.

• Smooth Endoplasmic Reticulum: Synthesizes lipids and detoxifies chemicals.

• Vesicle: Membrane-bound sacs for storage or transport.

Cell Division and Phases

Cell division is essential for growth, repair, and reproduction. The process involves several distinct phases.

• Interphase: Cell grows and DNA replicates.

• Prophase: Chromatin condenses into chromosomes; nuclear envelope breaks down.

• Metaphase: Chromosomes align at the cell’s equator.

• Anaphase: Sister chromatids separate and move to opposite poles.

• Telophase: Nuclear envelopes reform; chromosomes decondense.

Additional info: Students should be able to identify these phases on microscope slides and describe the key events in each phase.

Cell Transport Mechanisms

Diffusion and Osmosis

Cells exchange substances with their environment through various transport mechanisms.

• Diffusion: Movement of molecules from high to low concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Solute: Substance dissolved in a solution.

• Solvent: Substance that dissolves the solute (usually water in biological systems).

• Hypotonic solution: Lower solute concentration than the cell; water enters the cell, causing swelling.

• Hypertonic solution: Higher solute concentration than the cell; water leaves the cell, causing shrinkage.

• Isotonic solution: Equal solute concentration; no net water movement.

Formula for Osmosis:

$J = -D \frac{dC}{dx}$ Where: J = flux (rate of movement) D = diffusion coefficient dC/dx = concentration gradient

Example: Placing a cell in a hypotonic solution will cause it to swell due to water influx; in a hypertonic solution, it will shrink due to water efflux.

Additional info: Lab experiments often use dialysis tubing or animal cells to demonstrate osmosis and the effects of different solutions.

Summary Table: Cell Organelles and Functions

Organelle	Main Function
Centrosome	Organizes microtubules during cell division
Chromatin	Contains genetic material; condenses to form chromosomes
Mitochondria	Produces ATP (energy)
Golgi Apparatus	Modifies and packages proteins
Lysosome	Digests cellular waste
Ribosome	Protein synthesis
Plasma Membrane	Controls entry/exit of substances
Endoplasmic Reticulum (Rough/Smooth)	Protein and lipid synthesis
Nucleus	Contains DNA; regulates cell activities