Today’s Blog outlines the basic anatomy of your lungs, diaphragm, thorax, circulatory system, and heart…to be followed by a tour of your pelvic floor. It is my hope that you will learn to love anatomy, because it is ‘neat and tidy’ and makes logical, tactile sense once explained and felt.
PART ONE: THE THORAX AND THE THORACIC DIAPHRAGM
The Thorax consists of the ribcage, two scapulae (i.e., shoulder blades), two clavicles (i.e., collarbones), a sternum (i.e., breastbone) and your thoracic spine, which has twelve vertebrae. The ribcage has 24 ribs (12 on each side), attaching to your thoracic spine at the back, and to your sternum at the front.
You can think of the ribcage in two sections: a) the top half, R1-7 (i.e., upper ribcage), and b) the bottom half, R8-12 (i.e., lower ribcage).
Dividing the ribcage more or less in half in this way highlights the different functions of its upper and lower parts, including the different ways that breath and alignment effect and integrate your upper body.
The True Ribs (i.e., R1-7), or top seven ribs, are the least mobile of the ribcage, favoring stability for protection of the lungs and heart. They are called ‘true’ because they connect directly to the sternum via a shortened cartilage pathway. They connect snuggly into the spine and sternum, designed to ‘serve and protect’ as a container for heart and lungs.
In contrast, the False Ribs (i.e. R8-10) and Floating Ribs (i.e. R 11-12) are more mobile, designed to accommodate the movements of the diaphragm during respiration, and spinal movement of everyday life. False Ribs attach to the sternum only indirectly via extended and elongated costal cartilage where as your Floating Ribs, so-called because although they attach at the back to the T11-12 vertebrae, they do not attach to the front to the sternum at all. They are, in this way, said to ‘float’!
The Thoracic Diaphragm is the chief respiratory muscle of the body, shaped like a dome. It is located approximately halfway down the ribcage at the junction of the thoracic and abdominal cavities, around T7-8. The top surface (i.e. superior surface) of the diaphragm is convex, protruding into the thorax like a mushroom top or parachute. It is spoken of as the floor of the thoracic cavity, housing the heart and lungs above it. The inferior or underside of the diaphragm is concave, like the inside of an umbrella. This inner concave surface is spoken of as the roof of the abdominal cavity. It includes the liver, stomach, kidneys, bladder, reproductive organs, intestines, colon, etc. Body fat and continuous layers of fascia are also located in the abdominal cavity as well, acting as packing material that shape and contain the contents of your torso.
Anatomical Structure and Attachments of the Diaphragm is much like a circle with a circumference and a centre, so you can think of it as being in two parts: 1) the peripheral and (muscular) part and 2) the central (tendinous) part.
The Muscular Part: The muscular part of the diaphragm converges from its periphery towards toward the tendinous centre. In the photograph above, the white central depicts the tendonous part, while the darker periphery depicts the muscular part of the diaphragm.
Central-Tendinous Part: The Central Tendon of the diaphragm is a strong, wide, sheet-like connective tissue called aponeurosis. It is situated slightly closer to the front of the thorax while the posterior muscular fibers are located more to the back. The heart sits on top of the diaphragm, attached via this aponeurosis, which is then fused with the pericardium that covers the heart.
With inspiration, the diaphragm descends along the insides of the ribcage, much like an elevator descending into the basement. With expiration, the diaphragm rises, much like a bubble for example. The diaphragm essentially pushes and pulls the lungs during respiration. As it descends during inhalation, the diaphragm also widens. As the diaphragm rises, it then narrows.
This vertical motion can be visualized as an elevator or pump (hence, the ‘respiratory pump’). As mentioned, since the heart sits on top of the diaphragm, it also moves down and up along with your diaphragm, when you breathe.
Three major vessels of the body penetrate the diaphragm are the aorta, inferior vena cava, and esophagus. So each time the diaphragm moves up and down along its vertical axis, it squeezes or pumps our major vessels, helping to move our blood, oxygen and waster products through the body. When we breathe shallowly and without this diaphragmatic ease, this ‘flushing’ of our vital life forces becomes sub-optimal.
IMAGERY AND SHAPE OF THE DIAPHRAGM
We know that the shape of the thoracic diaphragm is domelike or round. Its convex shape is much like a mushroom, parachute, umbrella or jellyfish. A cloak or cape is also an appropriate image because the diaphragm is lower at the back than the front. The top right side of the diaphragm is higher than the left to accommodate our large liver that sits underneath it on the right. The left side of the diaphragm is lower to accommodate the heart that sits on top of it, slightly left from centre. Like all of us, the torso is lop-sided or imperfectly symmetrical!
|Image #1: The Diaphragm is convex like a dome.|
|Image #2: Imagine the ropes of a skydiver’s parachute are the crura tendons of a diaphragm. These tendons attach above to the parachute/diaphragm, and below to the skydiver/lumbar spine. The skydiver pulls on the ropes parachute/diaphragm and the chute billows outward like the diaphragm descends on the inhalation.
Imagine that the crura attach as low as the inner sacrum and tailbone, rather than just on the lumbar spine. Dropping the diaphragmatic attachment down enhances the descent of the diaphragm upon inhaling. Slide the diaphragm all the way down into your pelvic bowl as you inhale!
|Image #3: Imagine the diaphragm like an elevator or hydraulic pump, sliding down and up inside an elevator shaft, pressure chamber aka thoracic cavity.|
Attachments of the Diaphragm
The muscular fibers of the diaphragm have three distinct attachments to the torso. Part of the diaphragm attaches to the inner surface of the lower part of the sternum, and another part attaches to the inside of the bottom six ribs. At the back, the diaphragm attaches to the last thoracic vertebra (T12) and the first few lumbar vertebrae (L1-L3) via two long, tendons, call the right and left crura (singular, crus). Both of these attachments then merge into a single tendon to blend with the anterior longitudinal ligament of the spine. This anterior longitudinal ligament lays on the front of the vertebral bodies along the full length of the front spine, as if a long piece of wide, thick tape. The ligament is there to help prevent the vertebrae from shearing forward.
The diaphragm as our main respiratory muscle is fundamentally connected to our deep hip flexor (psoas), quadratus lumborum, i.e. lower back muscle) and our deepest abdominal (transversus abdominis TA) because of their close proximity at the lumbar spine and lower ribcage. With their attachments so close to each other, these muscles mutually influence each other, as well as the quality of your breathing and functional posture. Your breathing also directly affects these muscles.
For example, when your breathing is shallow because of stress – physical or emotional – your diaphragm will tend to tighten, decreasing its ability to fully descend and rise during each inhalation and exhalation. You can feel its tension in your solar plexus, as if a cramp or burn.
When natural, vertical diaphragmatic movement is restricted, your organs will not be massaged; your blood and oxygen flow will therefore be decreased; the exchange of oxygen and waste products will be decreased; and your ribcage will stiffen. Conversely, the stiffer your spine and ribcage become due to stress breathing and inactivity, the less deeply you can breath, because there is no freedom in your structure for the diaphragm to move with ease.
So there you go, it is a negative feedback loop! The very structure of our breathing mechanism ensures that we stay alive! It invites us to notice the contrast between ‘joy and pain’, so that we can make conscious and healthy choices to live by!