---
title: "Interventricular Septum | Anatomy and Physiology I"
description: "Interventricular septum in Anatomy and Physiology I: the wall between the heart’s ventricles that keeps blood moving in the right direction and supports pumping."
canonical: "https://fiveable.me/anatomy-physiology/key-terms/interventricular-septum"
type: "key-term"
subject: "Anatomy and Physiology I"
unit: "Unit 19"
---

# Interventricular Septum | Anatomy and Physiology I

## Definition

The interventricular septum is the muscular wall that separates the right and left ventricles of the heart. In Anatomy and Physiology I, it matters for heart structure, fetal development, and septal defects.

## What It Is

The interventricular septum is the wall between the heart’s two ventricles, the lower chambers that pump blood out of the heart. In Anatomy and Physiology I, you usually hear about it when you are mapping out the chambers of the heart or tracing how blood moves through the cardiac cycle.

It has a muscular part and a smaller membranous part. The muscular portion makes up most of the septum and gives the wall most of its thickness and strength. The membranous portion is thinner and is a common site for congenital septal defects because thin tissue is more likely to fail to close fully during development.

Functionally, the septum keeps the right and left ventricles separated so blood can be pumped through two different circuits without mixing. The right ventricle sends deoxygenated blood to the lungs, while the left ventricle sends oxygenated blood to the body. The septum helps preserve that separation and also provides a sturdy wall for the powerful contraction of the ventricles.

It is not just a divider. The interventricular septum also carries part of the heart’s electrical conduction pathway, including branches of the bundle of His that help coordinate ventricular contraction. That means the septum matters for both anatomy and physiology, not just for labeling a picture.

During cardiac development, the interventricular septum forms as the embryonic heart changes from a simple tube into a four-chambered pump. If the septum does not form or close correctly, blood can pass between ventricles. That is why this structure shows up again when you study congenital heart disease, especially ventricular septal defects.

## Why It Matters

The interventricular septum shows up anywhere you need to explain how the heart stays divided into a right pump and a left pump. Without it, the two ventricles would not work as separate chambers, and blood flow would lose its normal pressure pattern and direction.

This term also connects structure to function in a very A&P way. The left ventricle has a thicker wall because it has to pump blood through the entire body, and the septum helps form that shared ventricular boundary. When you look at a heart diagram, the septum is one of the easiest ways to orient yourself and tell where the ventricles are.

The developmental side matters too. When the septum forms incorrectly, the result can be a septal defect, often a ventricular septal defect, which can change blood flow and strain the heart. That gives the term real clinical weight, since a small gap in the septum can affect oxygen delivery and workload on the heart.

This is also one of those terms that ties together several units: heart anatomy, embryology, and conduction. If you can explain the interventricular septum, you can usually explain more than one part of a heart unit at once.

## Connections

### Ventricular Septum

This is the broader structure name for the wall that divides the ventricles. In many A&P contexts, interventricular septum and ventricular septum are used interchangeably, but the idea is the same: a partition between the two lower chambers. If you see either term on a diagram label, you are looking for the divider between right and left ventricles.

### Septal Defect

A septal defect is what happens when a septum does not form or close correctly. For the interventricular septum, that can mean blood passes between the ventricles instead of staying in the correct circulation. This term connects anatomy to a clinical outcome, so it often appears in case studies or questions about congenital heart disease.

### [Atrioventricular Septum](/anatomy-physiology/key-terms/atrioventricular-septum)

The atrioventricular septum is a different part of the heart that separates atria from ventricles, not right from left ventricles. It is easy to mix up because both terms include "septum" and both appear in heart development. Keeping them straight helps when you are tracking which chambers are being separated during fetal heart formation.

### Cardiac Development

The interventricular septum is one step in the larger process of cardiac development, where the simple embryonic heart tube becomes a four-chambered organ. If development is altered at the wrong time, the septum may not close completely. This makes the term useful in embryology questions that ask you to connect a structure to a stage of formation.

## On the AP Exam

A diagram label question may point to the wall between the ventricles and ask you to identify the interventricular septum. A short-answer item might ask why blood does not normally mix between the right and left ventricles, and you would mention this septum.

You may also see it in a congenital heart defect question, where you trace what happens if the septum has a hole or does not fully form. In a development unit, you could be asked to connect the septum to the embryo turning a single heart tube into a four-chambered heart. If the course includes lab models or heart dissections, this is one of the major internal landmarks you should be able to point out quickly.

## interventricular septum vs Atrial Septum

The atrial septum separates the right and left atria, while the interventricular septum separates the right and left ventricles. They are both partitions in the heart, but they divide different chambers and are linked to different defects. If a question says ventricles, think interventricular septum. If it says atria, think atrial septum.

## Key Takeaways

- The interventricular septum is the wall that separates the right and left ventricles of the heart.
- Its muscular portion makes up most of the wall, while the membranous portion is thinner and more likely to be involved in defects.
- The septum keeps oxygen-poor and oxygen-rich blood in separate pumping circuits.
- It also helps organize the heart’s electrical conduction so the ventricles contract in a coordinated way.
- If the septum does not form correctly during development, a septal defect can alter blood flow and create a congenital heart problem.

## FAQs

### What is the interventricular septum in Anatomy and Physiology I?

It is the wall that divides the heart’s right and left ventricles. In A&P, you study it as part of heart anatomy, blood flow, and fetal development. It keeps the two ventricular chambers separate so the pulmonary and systemic circuits stay distinct.

### Is the interventricular septum the same as the ventricular septum?

In most Anatomy and Physiology I contexts, yes, they refer to the same wall between the ventricles. "Interventricular" just makes it extra clear that the septum is between the ventricles. If a question uses either term, look for the divider between the lower chambers.

### What happens if there is a defect in the interventricular septum?

A hole or incomplete closure can let blood move between the ventricles, which is called a septal defect, often a ventricular septal defect. That can affect oxygen delivery and make the heart work harder. In class, this often comes up in congenital heart disease examples.

### Why is the interventricular septum important in heart development?

The septum forms as the embryo’s simple heart tube becomes a four-chambered heart. If the muscular or membranous parts do not form or fuse correctly, the ventricles may not stay fully separated. That is why it shows up in embryology and defect discussions, not just anatomy labels.

## Related Study Guides

- [19.5 Development of the Heart ](/anatomy-physiology/unit-19/5-development-heart/study-guide/TbeMMLg8CcS41duk)
- [19.1 Heart Anatomy ](/anatomy-physiology/unit-19/1-heart-anatomy/study-guide/rkGmPKJ0SjTIT3Kf)

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