SheepHeartDissectionAnswerKey-1.pdf - Sheep Heart Dissection ... - Free Printable

Let’s go step by step to solve this sheep heart dissection worksheet.

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Step 1: Identify the four chambers of the heart.

The heart has four chambers:
- Two on top (atria) — they receive blood.
- Two on bottom (ventricles) — they pump blood out.

In a sheep heart, just like in humans:
- Right atrium → receives deoxygenated blood from body
- Left atrium → receives oxygenated blood from lungs
- Right ventricle → pumps blood to lungs
- Left ventricle → pumps blood to body

So for question 1:

> The four chambers are:
> Right atrium, Left atrium, Right ventricle, Left ventricle

*(Note: Order may vary depending on how you list them, but all four must be named correctly.)*

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Step 2: Find the thickest chamber and explain why.

Look at the heart — the left ventricle is usually much thicker than the others.

Why? Because it has to pump blood all the way around the whole body (systemic circulation), which takes more force. The right ventricle only pumps to the lungs (pulmonary circulation), which is closer and easier.

So for question 2:

> Thickest chamber = Left ventricle
> Reason = It pumps blood to the entire body, so it needs stronger muscle.

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Step 3: Compare thickness of walls between atria and ventricles.

Atria have thin walls because they only push blood down into the ventricles — short distance, low pressure.

Ventricles have thick walls because they pump blood far away — either to lungs or body.

So for question 3:

> Atrial walls are thinner than ventricular walls.
> Why? Atria only send blood to nearby ventricles; ventricles send blood far away.

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Step 4: Feel the difference between pulmonary artery and aorta.

When you feel inside the heart:

- Pulmonary artery comes from the right ventricle → goes to lungs
- Aorta comes from the left ventricle → goes to body

You can tell them apart by where they connect:
- If you insert a probe into the vessel coming off the right side → it’s pulmonary artery
- If you insert into the big vessel coming off the left side → it’s aorta

Also, the aorta is usually bigger and tougher.

For question 4:

> Insert probe into vessel from right ventricle → leads to lungs → that’s pulmonary artery
> Insert probe into vessel from left ventricle → leads to body → that’s aorta

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Step 5: Locate valves and their functions.

Valves prevent backflow of blood.

There are two main types we care about here:

- Tricuspid valve → between right atrium and right ventricle
- Bicuspid (mitral) valve → between left atrium and left ventricle

Also:
- Pulmonary valve → between right ventricle and pulmonary artery
- Aortic valve → between left ventricle and aorta

But the question asks specifically about the ones between atria and ventricles.

So for question 5:

> Valve between right atrium and right ventricle = Tricuspid valve
> Valve between left atrium and left ventricle = Bicuspid (or Mitral) valve

Function: They open to let blood flow down, then close to stop it from flowing back up.

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Step 6: Trace blood flow through the heart.

Start with deoxygenated blood returning from body → enters right atrium → goes to right ventricle → pumped to lungs via pulmonary artery → becomes oxygenated → returns to left atrium → goes to left ventricle → pumped out to body via aorta.

So fill in blanks:

> Deoxygenated blood enters the right atrium from the vena cava.
> It flows through the tricuspid valve into the right ventricle.
> Then it is pumped through the pulmonary valve into the pulmonary artery to the lungs.
> Oxygenated blood returns via the pulmonary veins to the left atrium.
> Flows through the bicuspid/mitral valve into the left ventricle.
> Pumped through the aortic valve into the aorta to the body.

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Step 7: Label structures using word bank.

Word bank includes:
- Superior vena cava
- Inferior vena cava
- Right atrium
- Left atrium
- Right ventricle
- Left ventricle
- Pulmonary artery
- Pulmonary vein(s)
- Aorta
- Tricuspid valve
- Bicuspid/Mitral valve
- Chordae tendineae
- Papillary muscles
- Interventricular septum

Use these to label diagram based on location.

Example labels (based on typical sheep heart orientation):

Top part (receiving blood):
- Superior/inferior vena cava → entering right atrium
- Pulmonary veins → entering left atrium

Middle section:
- Right atrium → connected to right ventricle via tricuspid valve
- Left atrium → connected to left ventricle via bicuspid valve

Bottom pumping sections:
- Right ventricle → sends blood to pulmonary artery
- Left ventricle → sends blood to aorta

Inside:
- Chordae tendineae = string-like things holding valves
- Papillary muscles = little bumps attached to chordae
- Interventricular septum = wall separating left and right ventricles

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Final Answers Filled In:

1. Four chambers:
Right atrium, Left atrium, Right ventricle, Left ventricle

2. Thickest chamber:
Left ventricle
Reason: It pumps blood to the entire body, requiring more strength.

3. Wall comparison:
Atrial walls are thinner than ventricular walls.
Why? Atria only move blood locally; ventricles pump blood long distances.

4. Probe test:
- From right ventricle → pulmonary artery → leads to lungs
- From left ventricle → aorta → leads to body

5. Valves:
- Between right atrium & ventricle: Tricuspid valve
- Between left atrium & ventricle: Bicuspid (Mitral) valve
Function: Prevent backflow of blood into atria when ventricles contract.

6. Blood flow path:
Deoxygenated blood enters the right atrium from the vena cava.
Flows through the tricuspid valve into the right ventricle.
Pumped through the pulmonary valve into the pulmonary artery to the lungs.
Oxygenated blood returns via pulmonary veins to the left atrium.
Flows through the bicuspid/mitral valve into the left ventricle.
Pumped through the aortic valve into the aorta to the body.

7. Diagram labeling (example key points):
- Top vessels: superior/inferior vena cava → right atrium
- Other top vessels: pulmonary veins → left atrium
- Lower chambers: right/left ventricles
- Big outgoing vessel from left: aorta
- Outgoing from right: pulmonary artery
- Strings inside: chordae tendineae
- Muscles attached: papillary muscles
- Wall between ventricles: interventricular septum

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Final Answer:
All answers filled as above according to standard sheep heart anatomy and function.