Diaphragm: Structure, Functions, Disorders Practice Problems and FAQs

You might have got hiccups sometimes!! Hiccups are those odd, little sounds that occasionally come out of your mouth. One hiccup is funny. Twice is hilarious. But think about more than two hiccups. It is very annoying. Right? So when will you get hiccups? We usually get hiccups when we eat very fast, when we eat some very spicy foods or when we swallow air while chewing gum. It can also happen when we get nervous or too excited. These are some of the common causes for hiccups.

Can you tell me then what should be the scientific reason behind this? Let’s find it out. Normally, the diaphragm contracts when we breathe in air to lungs, and it relaxes when we breathe out air through the nose and mouth. Our diaphragm, however, can spasm if something irritates it, causing us to suddenly inhale air into the throat and then into the voice box. Now the vocal cords quickly close and as a result, it produces the distinctive 'hic!' sound. 

So hiccups are actually a very common disorder of the diaphragm. Now it is clear that hiccups are caused by the irritation that happens in the nerve that connects the brain and diaphragm. Some hiccups may last long which is not good for our health. The hiccups that last a while are due to the disorders of the central nervous system. Here in this article we are going to discuss more about the diaphragm which gives us hiccups.

Table of contents

• Diaphragm 
• Structure of diaphragm
• Functions of diaphragm
• Disorders of diaphragm 
• Practice Problems
• FAQs

Diaphragm 

The major muscle used for respiration is the diaphragm, which is situated below the lungs. This diaphragm is called thoracic diaphragm, because it is present in the thoracic region. It is a crucial anatomical landmark that divides the thorax, or chest, from the abdomen.

It is a large, dome-shaped muscle that frequently contracts rhythmically, involuntarily and continually. The diaphragm flattens and tightens during inhalation, and the chest cavity expands. A vacuum is created by the contraction which draws air into the lungs. The diaphragm relaxes and achieves its dome-like structure during exhalation. This results in the forcing out of air from the lungs.

Structure of diaphragm

The diaphragm is a sheet of muscles and tendons. It is made up of the sternal, costal, and lumbar muscles. All of these components have unique origins and all insert into the primary tendon of diaphragm. The diaphragm has the appearance of two domes. The liver is placed on the right side of the diaphragm, which causes it to be slightly more inferior than the left. Due to the push from the heart, the left side of the diaphragm may also be partially placed inferiorly. The pericardium causes this depression between the two domes of the diaphragm. The membrane that surrounds the heart is called the pericardium.

Surfaces of diaphragm

The two surfaces of the thoracic diaphragm face the thoracic cavity and the abdominal cavity. They are called the thoracic part and abdominal part of the diaphragm respectively. 

Thoracic diaphragm

The thoracic diaphragm is in contact with the serous membranes of the heart and lungs. A serous membrane is the smooth tissue membrane made of mesothelium that lines the interior of body cavities as well as the organs. The serous membrane of the heart is pericardium and that of lungs is pleura. 

Abdominal diaphragm

It is in contact with three organs, which are the liver, spleen and stomach. These organs are present in the abdominal cavity. 

Openings of diaphragm

There are several openings in the diaphragm, because it holds the function of providing passage for structures from the thorax to the abdomen. The openings are caval opening, oesophageal hiatus and aortic hiatus. Hiatus is an opening or slit or gap in anatomy. So all these openings allow the inferior vena cava, vagus nerves, oesophagus, descending aorta and other important structures to pass through the diaphragm.

Esophageal opening

The most portion of the digestive system is controlled by the oesophagus and vagus nerve. So both the oesophagus and vagus nerve pass through the esophageal opening. 

Aortic opening

The main artery of the human body is the aorta. It transports blood from the heart. Aorta passes through the aortic opening. The main vessel of the lymphatic system, the thoracic duct also passes through the same opening.

Caval opening

A large vein that transports the blood from the organs like the legs, feet, and organs in the abdomen and pelvis to the heart, which is the inferior vena cava, passes through the caval opening. 

Muscles of diaphragm 

Mammalian diaphragm is considered as a respiratory muscle. The crural and costal muscles of the diaphragm should be considered as two separate muscles that work together in synchrony during respiration. However, in certain situations like swallowing and emesis (process of vomiting) it might diverge the activity of these two muscle regions.

Crural muscles

Crus means leg in Latin. Since the muscles are in the shape of a leg, they are named as crural muscles. The origin of crura is from the front bodies and intervertebral fibrocartilage (lies within the vertebral column between adjacent vertebrae) of the lumbar vertebrae (the five vertebrae between the rib cage and the pelvis). The crural muscles are believed to be developed from the mesentery of the oesophagus. Mesentery is considered as a fold of membrane that normally attaches the intestine to the abdominal wall and holds it in its place. But later it was found that crural myoblasts can be either oesophageal or body wall in origin.

Coastal muscles 

Myoblasts of coastal muscles originate from the body wall. It is believed to be derived from the third, fourth and fifth cervical segments and then invaded into the two pleuroperitoneal membranes. They are named as coastal muscles as they are connected with the respiratory process just like the intercostal muscles.

Blood supply to diaphragm 

The blood supply to respiratory diaphragm comes from various arteries. Subcostal arteries and five pairs of intercostal arteries supply the blood to the costal portion of the diaphragm. The distal descending thoracic aorta gives rise to the bilateral subcostal arteries, which are small arteries. The blood vessels known as the intercostal artery are responsible for directing blood flow to the intercostal space, which is a region between the ribs.

The important source of vascular supply to the diaphragm is the inferior phrenic arteries. The left diaphragmatic crus (an elongated part of an anatomical structure), which is connected to the inferior surface of the diaphragm, is where the left inferior phrenic artery ascends. From this point, it travels posteriorly to the oesophagus and then runs anteriorly along the margin of esophageal hiatus. The right inferior phrenic artery travels anteriorly along the vena cava hiatus and behind the inferior vena cava. Superior phrenic arteries are the last source of blood supply. They supply blood to the superior surface of the diaphragm.

Nerves of diaphragm 

In order to facilitate breathing, the phrenic nerve is essential for the respiratory system. It is the only nerve in the neural system that gives diaphragm motor function or ability to move. Diaphragm expands and contracts as a result of the signals it delivers.

The sympathetic motor output is also modulated after the phrenic afferents are activated. The phrenic afferents also aid in somatosensation (mixed sensation) of the diaphragm, which increases awareness of breathing while awake.

Functions of diaphragm

The major functions of a diaphragm includes the respiration, increasing intra-abdominal pressure, providing passageway from thorax to abdomen etc.

Respiration 

One of the major respiratory muscles is the diaphragm. The diaphragm flattens when the muscle fibres contract. This will increase volume of the thoracic cavity and as a result the intrapulmonary pressure decreases. Now the air enters the lungs. When the diaphragm relaxes, the volume of the thoracic cavity decreases and there will be an increase in the intrapulmonary pressure. Hence the air flows out of the lungs.

Increasing intra-abdominal pressure

The diaphragm helps to raise intra-abdominal pressure when it works with the anterolateral abdominal muscles. This is required for processes including vomiting, defecating, urinating, and parturition (childbirth).

Providing passageway from thorax to abdomen

Diaphragm also provides passage for certain structures like vena cava, oesophagus, vagus nerves and aorta to pass from thorax to the abdomen. 

Disorders of diaphragm

The diaphragm can be impacted by a variety of health issues. Some of them are hiatal hernia, diaphragmatic hernia, cramps and spasms, diaphragmatic flutter, and phrenic nerve damage. Let’s discuss more about these health issues.

Hiatal hernia

When the upper portion of the stomach bulges through the esophageal opening of the diaphragm, then this condition is known as a hiatal hernia. This can be caused by age related changes in the diaphragm, long-term strain or hard lifting that puts chronic pressure on nearby muscles, injuries or by birth defects. Hiatal hernia can be usually seen in people with the age more than 50 and also in obese people. 

Diaphragmatic hernia

When at least one abdominal organ bulges into the chest through an opening in the diaphragm, this condition is known as a diaphragmatic hernia. It is of two types as follows:

Congenital diaphragmatic hernia 

Sometimes the condition of diaphragmatic hernia is present from birth. Hence this condition is known as a congenital diaphragmatic hernia (CDH). 

Acquired diaphragmatic hernia

A diaphragmatic hernia can also be brought on by surgical or accident-related injuries. It is known as an acquired diaphragmatic hernia (ADH) as it is acquired in the life of an individual.

Cramps and spasms

Chest pain and shortness of breath brought on by a diaphragmatic cramp or spasm might be misinterpreted for heart attacks. During a diaphragm spasm, some people may suffer sweating and anxiety or they find it difficult to breathe fully.

Diaphragmatic flutter

A rare illness known as diaphragmatic flutter which is the repeated involuntary contractions of the diaphragm is sometimes misdiagnosed as a spasm. An individual may experience the fluttering as a pulsing sensation in the abdomen wall.

Phrenic nerve damage

The phrenic nerve can be damaged by a number of problems, including multiple sclerosis, autoimmune diseases, traumatic injuries, lung cancer or adjacent lymph node cancer, spinal cord conditions, and viral illnesses. The diaphragm may become dysfunctional or paralysed as a result of this damage. But symptoms aren't usually present with phrenic nerve injury.

Practice Problems

Q 1. Which of the following statements is/are wrong about the thoracic diaphragm?

I) The diaphragm is a sheet of muscles and tendons.
II) The diaphragm has the appearance of two domes.
III) The pericardium causes the depression between the two domes.
IV) The thoracic diaphragm is in contact with the serous membranes of the heart and lungs
V) The serous membrane of the heart is pleura and that of lungs is pericardium.

a. I and II
b. I and V
c. V only
d. III only

Answer: The major muscle used for respiration is the diaphragm, which is situated below the lungs. This diaphragm is called thoracic diaphragm, because it is present in the thoracic region. The diaphragm is a sheet of muscles and tendons. It is a large, dome-shaped muscle that frequently contracts rhythmically, involuntarily and continually. The liver is placed on the right side of the diaphragm, which causes it to be slightly more inferior than the left. Due to the push from the heart, the left side of the diaphragm may also be partially placed inferiorly. The pericardium causes the depression between the two domes. A serous membrane is a smooth tissue membrane made of mesothelium that lines the interior of body cavities as well as their organs. The serous membrane of the heart is pericardium and that of lungs is pleura. Hence the correct option is c.

Q 2. Match the following:

a. I - A, II - B, III - C
b. I - A, II - C, III - B
c. I - C, II - B, III - A
d. I - B, II - C, III - A

Answer: There are several openings in the diaphragm, because it holds the function of providing passage for structures from the thorax to the abdomen. These openings allow the inferior vena cava, oesophagus, vagus nerves, descending aorta and other structures to pass through the diaphragm. The most portion of the digestive system is controlled by the oesophagus and vagus nerve. So both the oesophagus and vagus nerve pass through the esophageal opening. The main artery of the human body is the aorta. It transports blood from the heart. Aorta passes through the aortic opening. The main vessel of the lymphatic system, the thoracic duct also passes through the same opening. A large vein that transports the blood to the heart, which is the inferior vena cava, passes through the caval opening. Hence the correct option is b. 

Q 3. What is a hiatal hernia?
Answer: When the upper portion of the stomach bulges through the esophageal opening of the diaphragm, then this condition is known as a hiatal hernia. This can be caused by age related changes in the diaphragm, long-term strain or hard lifting that puts chronic pressure on nearby muscles, injuries or by birth defects. Hiatal hernia can be usually seen in people with the age more than 50 and also in obese people. 

Q 4. What are the major functions of diaphragm?
Answer: The major functions of a diaphragm includes the respiration, increasing intra-abdominal pressure, providing passageway from thorax to abdomen etc. The diaphragm flattens and the air enters the lungs. When the diaphragm relaxes the air flows out of the lungs. In order to facilitate breathing, the phrenic nerve is essential to the respiratory system. It is the only nerve in the neural system that gives the diaphragm motor function or ability to move. The diaphragm helps to raise intra-abdominal pressure when it works with the anterolateral abdominal muscles. This is required for processes including vomiting, defecating, urinating, and parturition (childbirth). Diaphragm also provides passage for certain structures like vena cava, oesophagus, vagus nerve and aorta to pass from thorax to the abdomen. 

FAQs

Q 1. What is pelvic diaphragm?
Answer: The pelvic diaphragm is a thin and wide muscular layer of tissue. It forms the inferior border of the abdominopelvic cavity (abdominal cavity and the pelvic cavity). Pelvic diaphragm is composed of a broad and funnel shaped sling of fascia and muscle. It spans from one lateral sidewall to the other, from the pubis to the coccyx. 

Q 2. What are the dos and don'ts while having hiccups?
Answer: There are many things which we can do ourselves to stop hiccups. Some of them are as follows: 

• Taking a breath into a paper bag.
• Lean forward and bring your knees to your chest.
• Drink some ice-cold water.
• Sugar should be swallowed.
• Take a bite of a lemon or taste some vinegar.
• Hold your breath for some time.

Now there are some things we should not do while having hiccups. They are as follows:

• Avoid alcoholic, carbonated, and hot beverages.
• Avoid smoking and chewing gum because doing so can make you inhale air.
• Avoid eating spicy food.
• Don't consume meals too fast.
• Never consume something really cold just after something which is very hot.

 Q 3. What signs would point to a paralysed diaphragm?
Answer: The loss of control of one or both sides of the diaphragm is known as diaphragm paralysis. As a result the lung capacity is reduced. Shortness of breath, headaches, bluish lips and fingers, fatigue, sleeplessness, and overall trouble in breathing are all possible symptoms of diaphragm paralysis.

Q 4. What is a diaphragmatic plication?
Answer: A surgical treatment called a diaphragmatic plication is performed to treat diaphragmatic paralysis or eventrations (protrusion of contents in the abdomen through a defect in the abdominal wall). By repositioning or reshaping the dome of the diaphragm, this procedure aims to increase the capacity of the lung to expand, as a result it reduces the breathing difficulties.

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