Required Practical: Dissecting Mass Transport Systems

External Observation: Identify the front of the heart by locating the coronary arteries, which typically run diagonally across the ventricles, and distinguish the atria as small, darker flaps at the top.

Initial Incisions: Use a scalpel or heavy-duty dissection scissors to make vertical cuts through the walls of the left and right ventricles to expose the internal chambers.

Internal Identification: Use forceps and a mounted needle to probe the atrioventricular valves (tricuspid and bicuspid) and locate the origins of the aorta and pulmonary artery.

Safety Protocols: Always wear gloves, eye protection, and a lab coat to prevent contamination; ensure all cuts are made away from the body and fingers are kept clear of the blade path.

Scalpel vs. Scissors: A scalpel is ideal for precise, shallow initial cuts, whereas dissection scissors are often more effective for cutting through thick, tough cardiac muscle without damaging underlying structures.

Arteries vs. Veins: During dissection, arteries (like the aorta) can be identified by their thick, elastic walls that remain open, while veins (like the vena cava) have thinner walls and often appear collapsed.

Biological Drawings: When recording observations, use a sharp HB pencil to draw clear, continuous lines without any shading or sketching; ensure all labels are horizontal and connected to the structure by a straight line without an arrowhead.

Tool Specificity: In exam answers, always name the specific tool for the task; use 'forceps' for lifting tissue, 'scalpel' for making incisions, and 'mounted needle' for pointing or probing.

Functional Justification: If asked to explain an observation, always link the structure to its function (e.g., 'The left ventricle wall is thicker to generate the high pressure needed to pump blood to the extremities').

Magnification: Always include a scale bar or calculate the magnification of your drawing to provide a sense of the actual size of the specimen.

Orientation Error: Students often confuse the left and right sides of the heart; remember that 'left' and 'right' refer to the specimen's perspective, meaning the left ventricle will be on the right side of the diagram when viewed from the front.

Damaging Valves: Applying too much pressure or cutting too deeply during the initial incision can accidentally sever the delicate chordae tendineae (heartstrings) or valve flaps.

Incomplete Cleaning: Failing to wash away clotted blood from the chambers can obscure the view of the valves and the entrances to the major blood vessels.

Shading in Drawings: A common mistake in biological drawings is using artistic shading to show depth; scientific diagrams must use stippling or simple lines to indicate texture instead.