Biology 11–12 · Year 11

Mammalian heart dissection: chambers, valves and wall thickness

Module 2: Organisation of Living Things (Transport)

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

A double circulation needs a pump with two sides of unequal strength and one-way valves, and the structure of a real heart shows each of those features.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

Sharp instruments
Microorganisms on raw animal tissue
Distress at dissection

Controls

Eye protection with sharp tools; cut away from the body
Gloves; wash boards and instruments in hot water and detergent, then disinfect them and the bench; wash hands before leaving; never store tissue in a food refrigerator
Offer an alternative task to any learner who opts out

Note

The heart is bought from a butcher or an abattoir; disinfectant per RiskAssess (https://www.riskassess.com.au/). NSW permits the dissection of animal parts bought from a butcher, supermarket or abattoir, no learner can be compelled to dissect, and any other source needs Schools Animal Care and Ethics Committee approval (https://education.nsw.gov.au/teaching-and-learning/animals-in-schools/animals-in-schools-issues/dissection-of-animals); the Department's Animals in Schools framework sets out the school's wider obligations (https://education.nsw.gov.au/teaching-and-learning/animals-in-schools).

What you need

Sheep or bovine heart from a butcher with vessels attached where possible, 1 per group
Dissection board; scalpel; scissors; forceps; probe; ruler; gloves; eye protection
Disinfectant for benches; paper towel; waste bag

How to do it

Identify the vessels entering and leaving the heart by wall thickness (arteries thick and rubbery, veins thin) and probe each to see which chamber it enters.
Locate the atria and ventricles and decide which side is left and which is right from wall firmness.
Make a longitudinal cut through the aorta and left ventricle to the apex, open the chamber, and examine the valve between atrium and ventricle and the semilunar valve at the aorta.
Repeat on the right side.
Measure and record the wall thickness of the left ventricle, right ventricle and an atrium with the ruler, and calculate the ratio of left to right ventricular wall thickness.
Draw the opened heart, labelling chambers, valves and vessels; disinfect and wash hands.

What you should see

The left ventricle wall is markedly thicker than the right, and both ventricles are thicker than the atria; flaps of the atrioventricular valves are tethered by cords, and the semilunar valves are pockets that close when the probe pushes back toward the ventricle. The learner knows it worked when the measured left to right wall ratio is greater than one and each of the four chambers and four valves has been located.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

The heart has one pump; it has two sides serving two circuits.
The right side is weaker because it is smaller; it pumps the same volume a shorter distance at lower pressure.
Valves are muscles that open and close actively; they are passive flaps moved by pressure differences.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Biology Stage 6 Syllabus (2017), current: Year 11 taught to the end of 2026 and Year 12 to Term 3 2027BIO11-9 BIO11/12-4 BIO11/12-7
Biology 11–12 Syllabus (2025), Year 11 focus area Cells to systems; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11-02
Biology 11–12 Syllabus (2025), Year 11 Working scientifically; new syllabus not yet taught: Year 11 from Term 1 2027, Year 12 from Term 4 2027BI-11WS-04 BI-11WS-07
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

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