Long Description Examples - Complex Images

Example 1: Carbon Cycle

When describing a complex diagram such as the one in Figure 11, focus on the data and not on the extraneous visual elements. You may need to combine a data table with a short text description to capture all the information in the image.

Carbon Cycle described below
Figure 11. Carbon Cycle (Adapted from "Effective Practices for Description of Science Content Within Digital Talking Books)"
Carbon Cycle Text Description

The figure is a diagram titled "Carbon Cycle."

Colorful pictures depict farms, forests, rivers, oceans, and industry. Four long arrows encircle the diagram, representing the cycle of carbon. Smaller arrows illustrate storage of carbon and fluxes in carbon through Earth's atmosphere, oceans, and land. Amounts are measured in GtC (gigatons of carbon).

Carbon storage and annual fluxes in carbon are depicted in Tables 2 and 3.

Table 2. Carbon Storage

Storage Area

GtC

Atmosphere

750

Vegetation

610

Fossil fuels and cement production

4,000

Soils

1,480

Surface ocean

1,020

Deep ocean

38,100

Marine biota

3

Underwater dissolved organic carbon

less than 700

Ocean sediments

150

Note. Adapted from "Effective Practices for Description of Science Content Within Digital Talking Books"

 

Table 3. Fluxes in Carbon

Flux

GtC

Atmosphere to vegetation

121.3

Vegetation to atmosphere

60.0

Soils to atmosphere

60.0

Forest fires to atmosphere

1.6

Atmosphere to evergreen forest

0.5

Fossil fuels and cement production to atmosphere

5.5

Note. Adapted from "Effective Practices for Description of Science Content Within Digital Talking Books"

Example 2: Oxygen Transfer

This example of an illustrated chemical reaction (similar to a flowchart) is from BIOL 141. The long description for this image was created by Sonya Woods based on advice from the DIAGRAM Center. This image is essentially a flowchart in which the processes can be explained in order of occurrence. The description was then sent to a content expert (the course instructor) for revision. The revised description was put into the course. The alt text is, "Illustration of oxygen transfer in the lungs described below."

illustration of oxygen transfer in the lungs described below
Figure 12. The Exchange of Oxygen and Carbon Dioxide. (Adapted from Human Anatomy and Physiology (9th ed.), by E. Marieb and K. Hoehn, 2013, Pearson Education, Inc. )
The Exchange of Oxygen and Carbon Dioxide Text Description

There are two illustrations, one showing oxygen release and carbon dioxide pickup at the tissues and one showing oxygen pickup and carbon dioxide release to the lungs, summarizing the gas exchanges that occur.

First Illustration: Oxygen Release and Carbon Dioxide Pickup at the Tissues

The first illustration shows tissue cells and blood plasma separated by interstitial fluid. Arrows of various thicknesses that correspond proportionately to the amounts of carbon dioxide and oxygen being moved show carbon dioxide moving from the tissue cells into the interstitial fluid and then into the blood plasma, showing the reactions for oxygen release (red arrows) and carbon dioxide pickup (blue arrows) at the tissues. Carbon dioxide can be transported from the tissues to the cells in three different forms: dissolved in plasma, chemically bound to hemoglobin, and as bicarbonate ions in plasma. This first illustration shows the reactions involved in carbon dioxide transport. These are the reactions:

  • A medium blue arrow shows carbon dioxide moving from the interstitial fluid into the plasma, where it is dissolved in plasma. Between 7% and 10% of carbon dioxide is transported in this way.
  • A narrow blue arrow shows carbon dioxide moving from the interstitial fluid into the plasma, where carbon dioxide and water combine to form carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions. These hydrogen ions bind to plasma proteins.
  • A narrow blue arrow shows carbon dioxide moving from the tissue cell into the interstitial fluid.
  • A thick blue arrow shows carbon dioxide moving from the interstitial fluid into a red blood cell with this reaction: Carbon dioxide and water are quickly converted by the action of the enzyme carbonic anhydrase into carbonic acid, which dissociates into bicarbonate ions and hydrogen ions. (This reaction in the red blood cells occurs much more quickly than the same reaction in the plasma shown previously.) These bicarbonate ions move quickly out of the red blood cell into the blood plasma while at the same time chloride ions move from the blood plasma into the red blood cell. This chloride shift acts to balance the loss of the negative bicarbonate ions from the red blood cell. About 70% of the carbon dioxide is transported in the form of bicarbonate ions.
  • A narrow blue arrow shows carbon dioxide moving from the tissue cell into the interstitial fluid.
  • A medium thick blue arrow shows carbon dioxide moving from the interstitial fluid into the red blood cell and combining with hemoglobin, which yields carbamino-hemoglobin (HbCO2). About 20% of carbon dioxide is transported as carbamino-hemoglobin.
  • Also illustrated within the red blood cell is the release of oxygen, which will diffuse into the interstitial tissues. Oxygen is carried on the hemoglobin of the red blood cell as oxyhemoglobin. This oxygen is unloaded from the oxyhemoglobin. Once it has unloaded its oxygen molecules, oxyhemoglobin is called deoxyhemoglobin.
  • A large red arrow shows oxygen moving from the red blood cell into the interstitial fluid, and then oxygen is shown by a narrow red arrow to be moving into the tissue cell.
  • A narrow red arrow shows oxygen that has dissolved in plasma moving into the interstitial fluid and then into the tissue cell.

Second Illustration: Oxygen Pickup and Carbon Dioxide Release to the Lungs

The second illustration shows the alveolus (in the lungs) and blood plasma separated by fused basement membranes. Red and blue arrows of varying thicknesses show the reactions for oxygen pickup (red arrows) and carbon dioxide release (blue arrows) in the lungs. The reactions are listed:

  • A medium-size blue arrow shows carbon dioxide that has been dissolved in the plasma moving from the plasma into the alveolus. Dissolved carbon dioxide moves by simple diffusion into the lungs, where it is released (expired).
  • A narrow blue arrow shows hydrogen ions combining with bicarbonate ions to yield carbonic acid, which dissociates into water and carbon dioxide. The carbon dioxide moves into the alveolus (lungs), where it is released. This reaction occurs slowly.
  • A narrow black arrow shows the chloride shift reversed. As bicarbonate ions move quickly into the red blood cells, chloride ions move out of the red blood cells. These bicarbonate ions are converted first to carbonic acid. Due to the action of the enzyme carbonic anhydrase, carbonic acid quickly breaks down into water and carbon dioxide.
  • A thick blue arrow shows the carbon dioxide moving into the alveolus (lungs). Most of the carbon dioxide transported from the red blood cells into the lungs is released by this reaction.
  • A medium blue arrow shows carbon dioxide moving into the alveolus (lungs) as a result of carbamino-hemoglobin dissociating into hemoglobin and carbon dioxide.
  • A thick red arrow shows oxygen moving from the alveolus (lungs) into the red blood cell, where oxygen combines with deoxyhemoglobin to form oxyhemoglobin; 98.5% of the oxygen carried from the lungs to the tissues is in the form of oxyhemoglobin.
  • A narrow red arrow shows oxygen moving from the alveolus into the blood plasma, where it is dissolved. Only 1.5% of the oxygen carried from the lungs to the tissues is dissolved in the plasma.

 

 

Example 3: Dropout Model

The diagram in Figure 13 comes from HIED 840 and is one of several similar diagrams illustrating the factors that lead to a student dropping out of college. The long description uses a list structure.The alt text is, "model of undergraduate drop out process described below."

model of undergraduate drop out process described below
Figure 13. Spady's Empirical Model of the Undergraduate Dropout Process (Adapted from The Value of a Model, by Dr. James Fredericks Volkwein.)
Spady's Empirical Model of the Undergraduate Dropout Process Text Description

The diagram shows dimensions of connectedness that contribute to the undergraduate dropout process and how they relate to each other, with indicators for factors that were significant for both sexes, women only, or men only.

Dimensions of connection:

  • Family background relates to
    • academic potential, normative congruence, and social integration for both sexes;
    • grade performance and institutional commitment for men only; and
    • intellectual development and structural relations (friendship support) for women only.
  • Academic potential relates to
    • grade performance for both sexes and
    • social integration for women only.
  • Grade performance relates to
    • satisfaction and dropout decisions for both sexes.
  • Satisfaction relates to
    • institutional commitment for both sexes.
  • Normative congruence relates to
    • grade performance, intellectual development, social integration, dropout decisions, and institutional commitment for both sexes.
  • Structural relations (friendship support) relates to
    • grade performance, intellectual development, social integration, and dropout decisions for both sexes;
    • institutional commitment for women only; and
    • satisfaction for men only.
  • Intellectual development relates to
    • satisfaction and institutional commitment for both sexes,
    • dropout decisions for women only, and
    • social integration for men only.
  • Social integration relates to
    • institutional commitment for both sexes and
    • dropout decisions for men only.
  • Institutional commitment relates to
    • dropout decisions and normative congruence for both sexes.

 

Updated September, 2020