THE DIAPHRAGM

The diaphragm is the primary muscle used in the process of inspiration, or inhalation. It is a dome-shaped sheet of muscle (and connective tissue) that is inserted into the lower ribs. Lying at the base of the thorax (chest), it separates the abdominal cavity from the thoracic cavity. The diaphragm can clearly be seen separating the two cavities (label 16) in the coronal image below. It is a thin, skeletal muscle that can contract voluntarily. 

During inhalation the diaphragm contracts & flattens, increasing the space for the lungs to fill with air. During exhalation the diaphragm relaxes and its dome shape increases, decreasing the thoracic volume and thereby assisting the lungs to empty.

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These are seen below as:

• aorta (label 4)
• oesophagus (label 3)
• Inferior vena cava (label 10)

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See anterior view of the abdomen below: The oesophagus (label 7) and aorta (label 25) can be seen going through the diaphragm. The vena cava is seen on the right side as a hole in the diaphragm (label 10).

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Additional resources:

1. Watch the The Diaphragm gross-anatomy video in Acland's Anatomy

Navigate to Trunk > MSK structures of the Trunk > 3.2.6 Diaphragm (4:14min)

For access you need to be logged in to the library: go to https://guides.lib.monash.edu/mnhs/anatomy_resources then click on Aclands video atlas then type in "diaphragm" to the search bar (the video is the top result).

Checklist to consider:

1. Note the central tendon of the diaphragm
2. Observe the location of the 3 main holes in the diaphragm - the aortic opening, the eosophageal hiatus and vena caval foramen

You do NOT have to learn about the diaphragmatic attachments, muscles or crura.

The structures traversing the diaphragm include:

Match the structures below with their corresponding letters (in image above):

The cartilage in the above specimen is found at label 5. It is called articular cartilage as it is found at the articulating surfaces of synovial joints (you will learn more about this in Weeks 3 & 4). An articulating surface is two (or more) apposing bones. Cartilage is present here to prevent damage to underlying bone, amongst other functions.

The cartilage here is one of 3 types of cartilage.

Match the type of cartilage to the locations.

Below, is a para-sagittal cross-section through the foot. 

Observe all the articulating bones via the shiny white cartilage present on the apposing surfaces. 

Approximately how many bones can you see in this cross-section?

Identify the spongy (trabecular/cancellous) bone components. Some obvious spongy bone is indicated by label 1. Spongy bone is composed of a network of bony struts, and filled with bone marrow.

Compact (cortical) bone is seen at the periphery of bone, and is solid, dense bone.

Bone is a highly vascular tissue: different bones of the skeleton have different amounts of blood supply.  Some, such as the bones of the toes, have abundant blood supply; some bones have a moderate blood supply, such as the tibia; while others, such as the head of the femur in the hip joint have a limited blood supply.

Bone marrow is the flexible connective tissue in the internal cavities in bones and is a major source of mesenchymal stem cells. It is comprised mainly of blood cells and adipose tissue. 

Which of the following is true of bone marrow? It contains mesenchymal stem cells which are:

What plane of section is this (image above)?

Which of the following may be found in the abdomen?

Where does the oesophagus sit compared with the trachea?

Choose the organs from the list below that you might find in the thorax:

What view is the image above?