IGCSE Biology 5 Views 1 Answers
Identify in diagrams and images the internal and external intercostal muscles
Identify in diagrams and images the internal and external intercostal muscles
Answer
The intercostal muscles, which play a crucial role in the mechanics of breathing, are divided into three main groups: external intercostal muscles, internal intercostal muscles, and innermost intercostal muscles. Below is a detailed description of the internal and external intercostal muscles, including their locations, functions, and orientations.
External Intercostal Muscles
- Location: The external intercostal muscles are situated on the outer surface of the ribs. They extend from the lower border of one rib to the upper border of the rib below.
- Orientation: The fibers run diagonally downward and forward (inferomedially) towards the center of the body.
- Function: These muscles are primarily involved in inhalation. When they contract, they elevate the ribs, expanding the thoracic cavity and allowing air to be drawn into the lungs.
- Diagram Reference: Diagrams typically show these muscles as superficial layers covering the ribs, often highlighted in a lighter color compared to deeper muscles.
Internal Intercostal Muscles
- Location: The internal intercostal muscles lie deeper than the external intercostals. They also extend between adjacent ribs but start from the lateral edge of the costal groove of one rib and insert into the superior border of the rib below.
- Orientation: The fibers run at right angles to those of the external intercostals, moving upward and inward (superolaterally).
- Function: These muscles are mainly involved in forced expiration. During exhalation, they help depress the ribs and reduce the volume of the thoracic cavity, pushing air out of the lungs.
- Diagram Reference: In anatomical diagrams, these muscles are often depicted beneath the external intercostals, typically shown in a darker color to indicate their deeper position.
Summary Table
| Muscle Type | Location | Orientation | Primary Function |
|---|---|---|---|
| External Intercostals | Superficial layer over ribs | Downward and forward (inferomedial) | Elevates ribs (inhalation) |
| Internal Intercostals | Deep layer beneath externals | Upward and inward (superolateral) | Depresses ribs (forced expiration) |
Visual Representation
To visualize these muscles:
- Look for anatomical diagrams that illustrate the thoracic cavity and label both muscle types.
- Diagrams typically show external intercostals in a lighter shade on top and internal intercostals in a darker shade underneath.
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