Welcome to Lesson 2 on an Introduction to Anatomy and Physiology

Levels of Organization and Divisions of the Abdomen

Lesson Goals

By the end of this lesson you will be able to: 

1. Identify the levels of organization of the human body

2. Identify the 3 major anatomical planes

3. Identify the 4 quadrant and 9 region system for describing locations of anatomical structures

Vocabulary

Sagittal plane-plane running down the middle of the body and dividing the body into right and left sections

Coronal plane-plane dividing the body into anterior and posterior sections

Transverse plane-plane dividing the body into superior and inferior sections

Transpyloric plane-the superior transverse plane used in the 9 abdominal region system

Transtubercular plane-the inferior transverse plane used in 9 abdominal region system

Epigastric–term that means above the stomach

Hypochondriac-term used in the 9 abdominal regions to identify structures superior and lateral to the stomach

Lumbar-term meaning the region of the low back and also used in the 9 abdominal region system for describing the location of structures lateral to the umbilicus

Umbilicus-the naval which indicates the center of the abdomen

Iliac-term meaning the lower lateral abdominal regions

Inguinal-term sometimes used in the 9 abdominal regions indicating the lower lateral abdomen

Hypogastric-term meaning below the stomach

Levels of Organization

The body is organized according to levels of complexity. The lowest level of complexity is the atom. The highest level of complexity is the organism. 

Here are the levels from lowest to highest complexity:

• Atom
• Molecule
• Cell
• Organ
• Organ System
• Organism (human body)

Anatomical Planes

A plane is a 2 dimensional object that can divide the body into 2 sections. Anatomical planes are used for studying slices of the body. For example, magnetic resonance

imaging (MRI) can “slice” the body into sections to look for abnormalities.

The anatomical planes divide the body in various ways.

The sagittal plane divides the body into right and left sections.

The coronal plane divides the body into anterior and posterior sections and the transverse plane divides the body into superior and inferior sections.

Abdominal Divisions

Abdominal divisions are used to describe the locations of pain, injuries and abnormalities in the abdominal area.

There are essentially 2 ways to divide the abdomen which include the 4 quadrant method and the 9 abdominal regions method.

For the 4 quadrant method, a sagittal and transverse plane intersect at the umbilicus. The quadrants are the right and left upper quadrants and right and left lower quadrants.

It is good to know some of the organs in each quadrant. For example, the gallbladder is in the right upper quadrant, the appendix in the right lower quadrant and the spleen is in the left upper quadrant.

The 9 abdominal regions are a bit more complex.

Four planes are needed to divide the abdomen into 9 equal sections. There are 2 parasagittal planes (sometimes called lateral lines) and 2 transverse planes. The superior transverse plane is called the transpyloric plane and the inferior plane is called the transtubercular plane. The center of the 9 regions is the umbilicus. The 3 superior regions are the epigastric and right and left hypochondriac. The middle regions are the umbilical and right and left lumbar.

The lower regions are the hypogastric and right and left iliac or inguinal.

Study the anatomical planes and abdominal divisions in the image below:

https://commons.wikimedia.org/wiki/File:Planes_of_Body.jpg

https://commons.wikimedia.org/wiki/File:Abdominal_Quadrant_Regions.jpg