Introduction to the Human Body: Directional Terms, Planes of Section, Microscopy, and Diffusion
Core idea: directional terms come in opposite pairs. Learning them as paired terms helps recall both members of each pair.
Opposite-term pairs:
Anterior – Posterior
Ventral – Dorsal
Superior – Inferior
Lateral – Medial
Proximal – Distal
Table 1.1: Directional Terms and Definitions (selected terms and definitions)
Superior: Describes a position above or higher than another part of the body on the head, neck, or trunk.
Inferior: Describes a position below or lower than another part of the body on the head, neck, or trunk.
Anterior: Describes a position toward the front of the body.
Posterior: Describes a position toward the back of the body.
Ventral: Describes a position toward the front of the body.
Dorsal: Describes a position toward the back of the body.
Proximal: Describes a position on a limb that is nearer to the point of attachment to the trunk of the body.
Distal: Describes a position on a limb that is farther from the point of attachment or the trunk of the body.
Medial: Describes a direction toward the middle of the body.
Lateral: Describes a direction toward the side of the body.
Ipsilateral: Occurring on the same side of the body.
Contralateral: Occurring on opposite sides of the body.
Superficial: Describes a position closer to the surface of the body.
Deep: Describes a position farther from the surface of the body.
Step 1 (sticky-note activity): Write each statement with a blank for the directional term and place sticky notes on the described body structures.
An example has been completed: a) The left wrist is distal to the left elbow. (sticky note on the left wrist)
Other items in Step 1 include: b) The right knee is ___ to the right ankle. c) The left ear is ___ to the mouth. d) The nose is ___ to the right eye. e) The patella is ___ to the patella (knee cap). And the patella is ___ to the patella. (Note: one sticky note is used for the pair of terms relating to the skin of the knee.)
Step 2: Complete a sticky note for each directional term in Table 1.1 that was not used in Step 1. You should end up with a total of 14 sticky notes on the model or partner.
Rationale: Understanding the anatomical position and directional terms underpins clear communication in clinical settings and avoid misidentification of structures.
Scenario 1 (clarity and rewording):
You encounter a caregiver’s note about a patient’s arm: "The patient's arm closest to me is painful to the touch above their elbow. Just below that painful spot, on the other side of the same arm, they have a circular rash."
Tasks:
Mark all unclear areas or areas where you might mistake the wrong structure.
Rewrite the instructions so the caregiver on the next shift can understand exactly where to assess.
Scenario 2 (describing a location over the phone):
You must describe an arm injury to medical personnel on the scene so they can locate it accurately on arrival.
Emphasis on using precise directional terms to convey a location that cannot be seen directly by the recipient.
Planes of Section
This activity targets LO 1.3 and 1.4 and explains how anatomists visualize internal structures via planes of section.
Key definitions:
Frontal (coronal) plane: divides the body into anterior and posterior sections.
Transverse plane: divides the body into superior and inferior sections.
Sagittal plane: divides the body into right and left halves.
Midsagittal (median) plane: sagittal plane that passes through the midline, creating equal left and right halves.
Parasagittal plane: sagittal plane that divides the body unequally; there are infinitely many parasagittal planes.
Materials used in the activity include a dissection tray, forceps, gummies, scalpel, and whole/pre-sectioned brains for viewing. A two-step process uses gummy bears to illustrate planes of section and to trace features.
Table 1.2 (Anatomical Planes of Section of the Body):
Sketches of resulting gummy bear sections and Associated Directional Terms (e.g., Left and Right; Parasagittal; Frontal/Coronal; Transverse).
Example: A midsagittal plane yields equal left and right sections and is associated with terms describing left-right symmetry.
Activity steps:
Step 1: Examine Figure 1.1 showing the three primary planes.
Step 2: Section gummy bears with different planes (frontal, sagittal, transverse).
Step 3: Compare your sections with a partner.
Step 4: In Table 1.2, lay out two section diagrams and trace key features to aid later interpretation.
Step 5: In the final column, write the directional terms associated with the resulting sections.
Step 6: Dispose of specimens per instructor directions.
CT context (Table 1.3 reference):
For brain studies, identify which plane of section has been used for each CT scan and match brain samples A–D to the CT images.
Computed Tomography (CT) Scans and Diffusion Context
CT scans explain rapid cross-sectional imaging using X-rays. A CT scan consists of a series of X-ray images taken as the machine moves along the body, which are stacked by a computer to generate a 3D visualization.
Key imaging characteristics:
Superior for dense structures like bone; soft tissues may be less distinct due to lower density contrast.
Contrast agents (injectable or ingested) improve visualization of soft tissues, blood vessels, and heart.
Common clinical uses:
Investigating complex bone fractures
Screening for tumors or lesions in the abdomen/pelvis (abdominopelvic cavity)
Imaging head or lungs to assess injuries, tumors, or blood flow issues
The Microscope (Activity 4.1): Parts and Handling
What a compound microscope is: uses multiple lenses to magnify objects; there are multiple lenses, and many labs are shared.
Handling and care:
Carry with two hands: one hand under the base, the other gripping the arm; always two hands.
Clean before and after use with lens paper; avoid using other materials that could scratch lenses.
Do not disassemble or repair—alert the instructor if something is broken.
Basic optical components:
Objective lenses: multiple lenses with different magnifications; each shows a magnification power, e.g., a lens labeled 10!\times.
Ocular lens (eyepiece): usually 10!\times magnification.
Total magnification is the product of objective and ocular magnifications: M{\text{total}} = M{\text{objective}} \times M_{\text{ocular}}.
Example: with a 10x objective and a 10x ocular, total magnification is M_{\text{total}} = 10 \times 10 = 100.
Field of view decreases as magnification increases; higher magnification narrows the visible area.
Other microscope components:
Condenser: concentrates and directs light toward the slide; does not directly magnify.
Diaphragm (in condenser): adjusts the amount of light passing through the condenser to control illumination.
Illumination: light source (illuminator) provides light that travels through the condenser to the slide.
Step-by-step lab practices:
Step 1: Record the magnification of each objective; calculate total magnification for each objective with a 10x ocular: total magnifications
Example format: Objective magnification: \text{mag}_{obj} = 4, 10, 40, 100;\text{ Ocular magnification} = 10.
Total magnifications: M{\text{total}} = \text{mag}{obj} \times 10.
Step 2: Focus knob exercise using a magnifying lens to feel coarse and fine focusing effects; observe how distance between lens and object changes focus.
Step 3: Repeat focusing with different objects to observe how optimal focal distance varies with object size and depth.
Step 4–6: Practice with actual microscope—start with the lowest power objective in place; then adjust using coarse focus, followed by fine focus to refine clarity.
The role of light in microscopy:
Condenser role: collects and directs light to the slide; diaphragm controls light intensity.
A well-focused setup yields a sharp image while minimizing aberrations and glare.
Slide Preparation and Wet Mounts (Activity 4.3)
Materials:
Clean slide, coverslip, methylene blue stain, saline, filter paper or towels, toothpicks, discard containers for biohazard waste.
Procedure overview:
1) Place a small drop of saline on the slide.
2) Gently scrape the inside of your cheek with a toothpick to collect epithelial cells.
3) Swirl the toothpick in the saline to release cells; discard toothpick in biohazard waste.
4) Add a tiny drop of methylene blue stain to the saline on the slide and stir gently with a new toothpick; discard toothpick in biohazard waste.
5) Place the coverslip at an angle to reduce air bubbles and slowly lay it down to avoid trapping air; blot edge with filter paper to remove excess liquid.
6) View the slide using the microscope following the low-to-high magnification approach.
7) Record the appearance of the field, total magnification used, and working distance at the chosen magnification.
8) Dispose of slides per instructor directions (e.g., bleach solution for slides, sharps waste for coverslips).Histology staining basics (Digging Deeper):
Hematoxylin and eosin (H&E) are two common stains used together.
Hematoxylin: basic, positively charged; stains acidic structures blue (e.g., DNA, ribosomes).
Eosin: acidic; stains basic structures pink.
Other stains: Giemsa (blood/bone marrow), Masson's trichrome (collagen fibers).
Learning connections:
Histology highlights tissue architecture; staining enhances contrast to identify cellular components and tissue organization.
Diffusion Through Two Media (Activity 5.1)
Topic: Diffusion is influenced by molecular size and the medium through which diffusion occurs.
Key concepts:
Solute: the substance that diffuses (e.g., potassium permanganate, methylene blue).
Solvent: the medium in which diffusion occurs (e.g., water, agar).
Diffusion rate depends on both solute size and the properties of the solvent or medium (e.g., density, porosity).
Molecules used in the experiment (Table 5.1):
Potassium permanganate (KMnO₄): purple dye; molecular weight M_{KMnO4} = 158\ \text{amu}. (solite)
Methylene blue: blue dye; approximate molecular weight around M_{MB} \approx 336\ \text{amu}. (solute; diffusion in two media)
Water (H₂O): the universal solvent; molecular weight M_{H2O} = 18\ \text{amu}. (solvent)
Agar: semi-solid polysaccharide used as a diffusion medium.
Experimental setup:
Diffusion mediums: distilled water vs. agar (1% w/v semi-solid).
Compare diffusion of KMnO₄ and methylene blue in these media.
Predictions (Step 1): formulate expected diffusion rates for each solute in each medium and how they differ across solvents.
Example prompts to predict: which solute diffuses fastest in water? Will diffusion rates differ between KMnO₄ in water vs KMnO₄ in agar? KMnO₄ in agar vs methylene blue in agar?
Procedure steps (Key actions):
Step 2: Prepare a half-filled Petri dish with distilled water; allow the surface to settle.
Step 3: Add KMnO₄ crystal near the center just above the intersection of two graph-paper lines.
Step 4: Measure the diameter of the purple dye at 1-minute intervals for 10 minutes; record in Table 5.2.
Step 5: Create a split agar plate by drawing a line along the bottom; place agar in the plate; create wells on either side of the line using the dropper to carve depressions.
Step 6: Refill wells with methylene blue and KMnO₄ as instructed.
Step 7: Record the clock time for 0 min and compute clock times for 15, 30, 45, and 60 minutes.
Step 8: At each interval, measure the diffusion distance from the edge of the well.
Step 9–11: After data collection, compare hypotheses with observations and reflect on any surprises; consider the influence of molecular size and medium properties on diffusion.
Data collection and analysis (Tables 5.2 and 5.3):
Table 5.2: Time interval vs. diameter of purple KMnO₄ dye (in mm) for up to 10 minutes.
Table 5.3: Data collection for diffusion experiments with clock times (0, 15, 30, 45, 60 minutes) and diameters for methylene blue and KMnO₄.
Practical takeaways:
Diffusion in denser media (agar) typically slows diffusion relative to diffusion in water due to reduced molecular mobility.
Larger molecules diffuse more slowly than smaller molecules in the same medium, all else equal, but the medium properties can modify this relationship.
Connections, Practical Implications, and Ethical Considerations
Qualitative skills emphasized:
Interpreting anatomical planes, maintaining precise language in medical communication, and describing locations with directional terms.
Understanding how imaging modalities (CT) and histological staining reveal structure and pathology relevant to diagnosis and treatment.
Practical implications:
Proper conventional terminology in clinical notes reduces miscommunication and improves patient safety.
Accurate plane identification and anatomical orientation play a critical role in planning surgical approaches and interpreting radiologic images.
Ethical and professional considerations:
Safe handling and disposal of biological materials (biohazard waste) during cheek cell slides; use of gloves when handling preserved brain specimens if provided; washing hands after handling specimens.
Avoiding miscommunication that could lead to incorrect treatments, especially in emergency scenarios described in Scenario 1 and Scenario 2.
Summary of Key Formulas and Numerical References
Total magnification in microscopy:
M{\text{total}} = M{\text{objective}} \times M_{\text{ocular}}
Example: with a 10x objective and a 10x ocular: M_{\text{total}} = 10 \times 10 = 100.
Common objective magnifications (Table 4.1 reference):
Scanning power: 4\times
Low power: 10\times
High power: 40\times
Oil immersion: 100\times
Specimen sizes and molecular weights (Table 5.1 references):
Potassium permanganate: M_{KMnO4} = 158\ \text{amu} (solute)
Methylene blue: approx. M_{MB} \approx 336\ \text{amu} (solute)
Water: M_{H2O} = 18\ \text{amu} (solvent)
Agar: polysaccharide medium (no simple single molecular weight)
References to Lab Activities and Tables (as described in the transcript)
Activity 1.2: Directional Terms and the pairwise relationships; Table 1.1; sticky-note checks; scenarios for clinical communication.
Activity 1.3: Planes of Section; Figure 1.1; Table 1.2; Table 1.3 (Brain CT plane matching).
Activity 4.1: Parts of the Microscope; Table 4.1; Figures 4.1–4.6; concepts of magnification, field of view, condenser, and diaphragm.
Activity 4.3: Slide Preparation; cheek cell wet mount; methylene blue staining; wet-mount technique (Figure 4.8); histology basics (H&E staining).
Activity 5.1: Diffusion through Two Media; Table 5.1 (molecule properties); Table 5.2 (observations); Table 5.3 (data collection);
discussion of diffusion in water vs. agar.