Is the diaphragm made of two muscles?

Is the diaphragm made of two muscles?

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Is there a 'crural' and 'costal' parts of the diaphragm as suggested in this paper or is it just a single muscle?

Thoracic Diaphragm

Thoracic diaphragm is the large muscle that separates the chest cavity from the abdominal cavity in mammals and is the principal muscle of respiration. As the diaphragm contracts and moves downward, the lungs expand and air moves into them. As the diaphragm relaxes and moves upward, the lungs contract and air is forced out of them.

The origins of the diaphragm are found along the lumbar vertebrae of the spine and the inferior border of the ribs and sternum. Openings in the diaphragm allow the esophagus, phrenic and vagus nerves, descending aorta, and inferior vena cava to pass between the thoracic and abdominal cavities. The lungs are enclosed in the thoracic cavity by the rib cage on the front, back, and sides with the diaphragm forming the floor of the cavity.

Structure and Functions of Thoracic Diaphragm

Structurally, the diaphragm consists of two parts: the peripheral muscle and central tendon. The peripheral muscle is made up of many radial muscle fibers, originating on the ribs, sternum, and spine that converge on the central tendon. The central tendon a flat aponeurosis made of dense collagen fibers acts as the tough insertion point of the muscles. When air is drawn into the lungs, the muscles in the diaphragm contract, and pull the central tendon inferiorly into the abdominal cavity. This enlarges the thorax and allows air to inflate the lungs.

Serving as the inferior aspect of the thorax, it is the means by which the chest cavity volume is increased. In order to expand the thorax, increase the vertical dimension of the chest, and decrease the air pressure in the thoracic cavity, this sheet of muscle has to flatten out by contracting.

Diaphragm sometimes contracts involuntarily due to certain irritations these contractions can happen because we eat too quickly, drink carbonated beverages, experience some acid indigestion, or are dealing with a stressful day. If air is inhaled at these times of contraction, the space between the vocal cords at the back of the throat closes suddenly producing the noise we call hiccups. Short-lived hiccuping episodes are very common. Longer-term hiccups (lasting for days) can occur as well and are usually caused by irritated nerves, though medical attention would be needed in order to rule out other health concerns.

Diaphragm functions in breathing. During inhalation, the diaphragm contracts and moves in the inferior direction, thus enlarging the volume of the thoracic cavity. This reduces intra-thoracic pressure: In other words, enlarging the cavity creates suction that draws air into the lungs. It is also involved in non-respiratory functions, helping to expel vomit, feces, and urine from the body by increasing intra-abdominal pressure, aiding in childbirth, and preventing acid reflux by exerting pressure on the esophagus as it passes through the esophageal hiatus.


The diaphragm is the dome-shaped sheet of muscle and tendon that serves as the main muscle of respiration and plays a vital role in the breathing process. Also known as the thoracic diaphragm, it serves as an important anatomical landmark that separates the thorax, or chest, from the abdomen. The origins of the diaphragm are found along the lumbar vertebrae of the spine and the inferior border of the ribs and sternum. Openings in the diaphragm allow the esophagus, phrenic and vagus nerves, descending aorta, and inferior vena cava to pass between the thoracic and abdominal cavities. Continue Scrolling To Read More Below.

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The lungs are enclosed in the thoracic cavity by the rib cage on the front, back, and sides with the diaphragm forming the floor of the cavity. When we inhale, the diaphragm contracts and is drawn inferiorly into the abdominal cavity until it is flat. At the same time, the external intercostal muscles between the ribs elevate the anterior rib cage like the handle of a bucket. The thoracic cavity becomes deeper and larger, drawing in air from the atmosphere. During exhalation, the rib cage drops to its resting position while the diaphragm relaxes and elevates to its dome-shaped position in the thorax. Air within the lungs is forced out of the body as the size of the thoracic cavity decreases.

Structurally, the diaphragm consists of two parts: the peripheral muscle and central tendon. The peripheral muscle is made up of many radial muscle fibers — originating on the ribs, sternum, and spine — that converge on the central tendon. The central tendon — a flat aponeurosis made of dense collagen fibers — acts as the tough insertion point of the muscles. When air is drawn into the lungs, the muscles in the diaphragm contract, and pull the central tendon inferiorly into the abdominal cavity. This enlarges the thorax and allows air to inflate the lungs.

The peripheral muscle can be further divided by its origins into the sternal, costal, and lumbar regions. The sternal region is made up of two small muscular segments that attach to the posterior aspect of the xiphoid process. The costal region is made up of several wide muscle segments whose origins are found on the internal surface of the inferior six ribs and costal cartilages. The lumbar region has its origins on the lumbar vertebra by way of two pillars of tendon called the musculotendinous crura. These pillars wrap around the aorta as it passes through the diaphragm to form the aortic hiatus.

The diaphragm sometimes contracts involuntarily due to certain irritations these contractions can happen because we eat too quickly, drink carbonated beverages, experience some acid indigestion, or are dealing with a stressful day. If air is inhaled at these times of contraction, the space between the vocal cords at the back of the throat closes suddenly, producing the noise we call hiccups. Short-lived hiccuping episodes are very common. Longer-term hiccups (lasting for days) can occur as well and are usually caused by irritated nerves, though medical attention would be needed in order to rule out other health concerns.


The diaphragm plays an integral role in respiration (breathing). Most of the time, the diaphragm moves involuntarily.

Your thoracic diaphragm also plays a role in helping the movement of muscles during childbirth, having a bowel movement, urinating, and lifting heavy objects. This muscle also helps maintain the flow of lymphatic fluid throughout the body.  

Diaphragmatic Movement

When the diaphragm is activated by a nerve, it contracts and flattens. This action decreases pressure and increases the space in the thoracic cavity, allowing your lungs to expand as you inhale. When the diaphragm relaxes, your chest cavity becomes smaller and your lungs release air.  

Your diaphragm contracts rhythmically and involuntarily (such as during sleep) due to signals from your brain. You can also voluntarily contract your diaphragm to hold your breath, to breathe more deeply or faster, or to exert your muscles.  

Diaphragmatic breathing is a technique that is used to strengthen the diaphragm, allowing more air to enter and exit the lungs without tiring the chest muscles. This is also referred to as "belly breathing" and is often used by singers.  

Breathing: Grade 9 Understanding for IGCSE Biology 2.46 2.47

Breathing is the movement of air in and out of the lungs. It is a small point but you must be careful with your language in answering questions in this topic. Meaning is lost if words are not used correctly: for example often candidates write than “oxygen is breathed in and carbon dioxide breathed out….” Can you see why this is not correct and actually muddles your understanding of the process?

(Please don’t confuse breathing with gas exchange which is the diffusion of oxygen and carbon dioxide in and out of the blood, nor with respiration which is a series of chemical reactions happening in all cells in which food molecules are oxidised to release energy for the cell)

So back to breathing – the movement of air in and out of the lungs…..

1) What is the pathway air follows to get from the atmosphere and into the alveoli in the lung?

The trachea is the main tube that carries air into the lungs. It has a ciliated epithelium lining – these cilia waft mucus and foreign particles up to the top of the trachea and then the mucus is swallowed into the stomach and any bacteria trapped in the mucus are killed. The trachea is also strengthened by C-shaped rings of cartilage that prevent the tube collapsing when the air pressure inside drops. The trachea branches into two tubes called bronchi, one going to each lung. The bronchi branch over and over again into smaller tubes called bronchioles and ultimately the smallest bronchioles end in a cluster of microscopic air sacs called alveoli. This whole structure is called the Bronchial Tree.

2) What causes air to move in and out of the lungs in breathing?

The movement of air into and out of the lungs is brought about by the action of two muscles: the diaphragm, a dome-shaped muscle that separates the thorax from the abdomen, and the two sets of intercostal muscles. This is an easy area to get confused as there are plenty of similar words and precision in explanation is vital to clear understanding…..

Breathing in (Inhalation) is the active stage in breathing. This means that under normal condition it is the stage in which the muscles contract. During inhalation, the diaphragm contracts. This contraction causes it to change shape from the dome-shape at rest to a flattened shape. This change in shape of the diaphragm increases the volume of the thorax (in fact it is the volume of the pleural space between the two pleural membranes that is significant but we might skip over this for simplicity….).

If the volume of a gas increases, the pressure decreases (Boyle’s Law I seem to remember from boring Physics lessons a long time ago). If the pressure in the thorax decreases, it may drop below atmospheric pressure and so air can be pushed into the alveoli through the bronchial tree by the higher atmospheric pressure.

Breathing out (Exhalation) is a passive process. The diaphragm is a most unusual muscle as it is very elastic. This means that when it relaxes, it springs back to its original dome-shape through elastic recoil. This movement decreases the volume of the thorox, thus increasing the pressure and if the pressure rises above atmospheric pressure, air will be pushed out of the alveoli.

3) What role do the Intercostal muscles play in breathing?

The intercostal muscles are two sets of muscles that are found between the ribs. Contraction of these muscles can either pull the rib cage up and out, or push the rib cage down and in. The muscles on the outside are called the external intercostal muscles and the ones on the inside are called internal intercostal muscles.

When you are breathing at rest the rib cage does not move at all. (I hope everyone reading this post is calm, relaxed and not hyperventilating in panic over upcoming exams….) As you are breathing at rest the only muscle involved is the diaphragm (see section above) as you are only moving about half a litre of air in and out with each breath. But there are situations in which this tidal volume has to increase and that is when the intercostal muscles come into their own.

The two sets of intercostal muscles are antagonistic – when one contracts the other relaxes.

If you need to take a big breath in, the external intercostals will contract at the same time as the diaphragm. The external intercostals pull the ribcage up and out, thus increasing even further the volume of the thorax, thus dropping the air pressure even more in the thorax, allowing more air to come in. When you come to breathe out, the external intercostal muscles will relax and gravity will allow the ribcage to fall back down to its original position.

But I hear you say…. “What happens if you are lying down or upside down? How can the ribcage get back to its original position without the help of gravity?” Well don’t worry – you have the internal intercostals which in extreme situations will contract during exhalation to push the ribcage down and in…

I suggest you draw up a table to summarise the process of breathing. Give inhalation and exhalation a column each, and the rows of the table should be diaphragm, external intercostals, internal intercostals… Tweet me a photo of your table if you want me to have a look…

Associated Conditions

Diaphragm Spasms: Sometimes, the diaphragm spasms causing harmless hiccups may last for days or weeks, indicating some underlying health condition. Sometimes, this abnormally contracted muscle may make it difficult to breathe deeply, leading to other problems [24] .

Paralyzed Diaphragm: A trauma to the phrenic nerves, lung or lymph node cancer, injury or surgical trauma to the diaphragm, certain spinal cord conditions and neuropathic diseases may weaken or paralyze the diaphragm (one or both sides). Since the two halves can work on their own, one side being collapsed does not hamper the functioning of the other side. However, it still interferes with the lungs’ ability to take in air, as the muscle cannot contract to its full capacity [25] .

Elevated Diaphragm: Sometimes, the sheet muscle may elevate a little higher towards the chest cavity due to some abnormality in the tissues and organs around it. Possible causes include blood clotting or infection within the lungs, pulmonary fibrosis, a collapsed lung [26] , and abdominal tumor [27] .

Diaphragmatic Hernia: A birth defect, occurring as a fetus is developing in the mother’s womb, it causes the abdominal organs to move up an abnormal hole in the diaphragm [28] . Such cases usually need a diaphragm repair surgery once the baby is born. Tests like ultrasound and x-ray help with the diagnosis.

Diaphragmatic Eventration: Another congenital malformation, it causes the diaphragmatic muscles to partially be replaced with some thin membranous fibroelastic tissues [29] .

Other Conditions that Might Affect the Diaphragm: Abdominal bloating may put pressure on the diaphragm, preventing it from contracting properly, leading to a feeling of tightness, irritation, pain when breathing in, and shortness of breath [30] . An accidental injury to the abdomen or chest may rupture the sheet muscle, leading to a number of complications.

Axial Muscles of the Abdominal Wall, and Thorax

It is a complex job to balance the body on two feet and walk upright. The muscles of the vertebral column, thorax, and abdominal wall extend, flex, and stabilize different parts of the body’s trunk. The deep muscles of the core of the body help maintain posture as well as carry out other functions. The brain sends out electrical impulses to these various muscle groups to control posture by alternate contraction and relaxation. This is necessary so that no single muscle group becomes fatigued too quickly. If any one group fails to function, body posture will be compromised.

Muscles of the Abdomen

There are four pairs of abdominal muscles that cover the anterior and lateral abdominal region and meet at the anterior midline. These muscles of the anterolateral abdominal wall can be divided into four groups: the external obliques, the internal obliques, the transversus abdominis, and the rectus abdominis ((Figure) and (Figure)).

Muscles of the Abdomen
Movement Target Target motion direction Prime mover Origin Insertion
Twisting at waist also bending to the side Vertebral column Supination lateral flexion External obliques internal obliques Ribs 5–12 ilium Ribs 7–10 linea alba ilium
Squeezing abdomen during forceful exhalations, defecation, urination, and childbirth Abdominal cavity Compression Transversus abdominus Ilium ribs 5–10 Sternum linea alba pubis
Sitting up Vertebral column Flexion Rectus abdominis Pubis Sternum ribs 5 and 7
Bending to the side Vertebral column Lateral flexion Quadratus lumborum Ilium ribs 5–10 Rib 12 vertebrae L1–L4

There are three flat skeletal muscles in the antero-lateral wall of the abdomen. The external oblique , closest to the surface, extend inferiorly and medially, in the direction of sliding one’s four fingers into pants pockets. Perpendicular to it is the intermediate internal oblique , extending superiorly and medially, the direction the thumbs usually go when the other fingers are in the pants pocket. The deep muscle, the transversus abdominis , is arranged transversely around the abdomen, similar to the front of a belt on a pair of pants. This arrangement of three bands of muscles in different orientations allows various movements and rotations of the trunk. The three layers of muscle also help to protect the internal abdominal organs in an area where there is no bone.

The linea alba is a white, fibrous band that is made of the bilateral rectus sheaths that join at the anterior midline of the body. These enclose the rectus abdominis muscles (a pair of long, linear muscles, commonly called the “sit-up” muscles) that originate at the pubic crest and symphysis, and extend the length of the body’s trunk. Each muscle is segmented by three transverse bands of collagen fibers called the tendinous intersections . This results in the look of “six-pack abs,” as each segment hypertrophies on individuals at the gym who do many sit-ups.

The posterior abdominal wall is formed by the lumbar vertebrae, parts of the ilia of the hip bones, psoas major and iliacus muscles, and quadratus lumborum muscle. This part of the core plays a key role in stabilizing the rest of the body and maintaining posture.

Physical Therapists Those who have a muscle or joint injury will most likely be sent to a physical therapist (PT) after seeing their regular doctor. PTs have a master’s degree or doctorate, and are highly trained experts in the mechanics of body movements. Many PTs also specialize in sports injuries.

If you injured your shoulder while you were kayaking, the first thing a physical therapist would do during your first visit is to assess the functionality of the joint. The range of motion of a particular joint refers to the normal movements the joint performs. The PT will ask you to abduct and adduct, circumduct, and flex and extend the arm. The PT will note the shoulder’s degree of function, and based on the assessment of the injury, will create an appropriate physical therapy plan.

The first step in physical therapy will probably be applying a heat pack to the injured site, which acts much like a warm-up to draw blood to the area, to enhance healing. You will be instructed to do a series of exercises to continue the therapy at home, followed by icing, to decrease inflammation and swelling, which will continue for several weeks. When physical therapy is complete, the PT will do an exit exam and send a detailed report on the improved range of motion and return of normal limb function to your doctor. Gradually, as the injury heals, the shoulder will begin to function correctly. A PT works closely with patients to help them get back to their normal level of physical activity.

Muscles of the Thorax

The muscles of the chest serve to facilitate breathing by changing the size of the thoracic cavity ((Figure)). When you inhale, your chest rises because the cavity expands. Alternately, when you exhale, your chest falls because the thoracic cavity decreases in size.

Muscles of the Thorax
Movement Target Target motion direction Prime mover Origin Insertion
Inhalation exhalation Thoracic cavity Compression expansion Diaphragm Sternum ribs 6–12 lumbar vertebrae Central tendon
Inhalationexhalation Ribs Elevation (expands thoracic cavity) External intercostals Rib superior to each intercostal muscle Rib inferior to each intercostal muscle
Forced exhalation Ribs Movement along superior/inferior axis to bring ribs closer together Internal intercostals Rib inferior to each intercostal muscle Rib superior to each intercostal muscle

The Diaphragm

The change in volume of the thoracic cavity during breathing is due to the alternate contraction and relaxation of the diaphragm ((Figure)). It separates the thoracic and abdominal cavities, and is dome-shaped at rest. The superior surface of the diaphragm is convex, creating the elevated floor of the thoracic cavity. The inferior surface is concave, creating the curved roof of the abdominal cavity.

Defecating, urination, and even childbirth involve cooperation between the diaphragm and abdominal muscles (this cooperation is referred to as the “Valsalva maneuver”). You hold your breath by a steady contraction of the diaphragm this stabilizes the volume and pressure of the peritoneal cavity. When the abdominal muscles contract, the pressure cannot push the diaphragm up, so it increases pressure on the intestinal tract (defecation), urinary tract (urination), or reproductive tract (childbirth).

The inferior surface of the pericardial sac and the inferior surfaces of the pleural membranes (parietal pleura) fuse onto the central tendon of the diaphragm. To the sides of the tendon are the skeletal muscle portions of the diaphragm, which insert into the tendon while having a number of origins including the xiphoid process of the sternum anteriorly, the inferior six ribs and their cartilages laterally, and the lumbar vertebrae and 12th ribs posteriorly.

The diaphragm also includes three openings for the passage of structures between the thorax and the abdomen. The inferior vena cava passes through the caval opening , and the esophagus and attached nerves pass through the esophageal hiatus. The aorta, thoracic duct, and azygous vein pass through the aortic hiatus of the posterior diaphragm.

The Intercostal Muscles

There are three sets of muscles, called intercostal muscles , which span each of the intercostal spaces. The principal role of the intercostal muscles is to assist in breathing by changing the dimensions of the rib cage ((Figure)).

The 11 pairs of superficial external intercostal muscles aid in inspiration of air during breathing because when they contract, they raise the rib cage, which expands it. The 11 pairs of internal intercostal muscles, just under the externals, are used for expiration because they draw the ribs together to constrict the rib cage. The innermost intercostal muscles are the deepest, and they act as synergists for the action of the internal intercostals.

Muscles of the Pelvic Floor and Perineum

The pelvic floor is a muscular sheet that defines the inferior portion of the pelvic cavity. The pelvic diaphragm , spanning anteriorly to posteriorly from the pubis to the coccyx, comprises the levator ani and the ischiococcygeus. Its openings include the anal canal and urethra, and the vagina in women.

The large levator ani consists of two skeletal muscles, the pubococcygeus and the iliococcygeus ((Figure)). The levator ani is considered the most important muscle of the pelvic floor because it supports the pelvic viscera. It resists the pressure produced by contraction of the abdominal muscles so that the pressure is applied to the colon to aid in defecation and to the uterus to aid in childbirth (assisted by the ischiococcygeus , which pulls the coccyx anteriorly). This muscle also creates skeletal muscle sphincters at the urethra and anus.

The perineum is the diamond-shaped space between the pubic symphysis (anteriorly), the coccyx (posteriorly), and the ischial tuberosities (laterally), lying just inferior to the pelvic diaphragm (levator ani and coccygeus). Divided transversely into triangles, the anterior is the urogenital triangle , which includes the external genitals. The posterior is the anal triangle , which contains the anus ((Figure)). The perineum is also divided into superficial and deep layers with some of the muscles common to men and women ((Figure)). Women also have the compressor urethrae and the sphincter urethrovaginalis , which function to close the vagina. In men, there is the deep transverse perineal muscle that plays a role in ejaculation.

Chapter Review

Made of skin, fascia, and four pairs of muscle, the anterior abdominal wall protects the organs located in the abdomen and moves the vertebral column. These muscles include the rectus abdominis, which extends through the entire length of the trunk, the external oblique, the internal oblique, and the transversus abdominus. The quadratus lumborum forms the posterior abdominal wall.

The muscles of the thorax play a large role in breathing, especially the dome-shaped diaphragm. When it contracts and flattens, the volume inside the pleural cavities increases, which decreases the pressure within them. As a result, air will flow into the lungs. The external and internal intercostal muscles span the space between the ribs and help change the shape of the rib cage and the volume-pressure ratio inside the pleural cavities during inspiration and expiration.

The perineum muscles play roles in urination in both sexes, ejaculation in men, and vaginal contraction in women. The pelvic floor muscles support the pelvic organs, resist intra-abdominal pressure, and work as sphincters for the urethra, rectum, and vagina.

Review Questions

Which of the following abdominal muscles is not a part of the anterior abdominal wall?

  1. quadratus lumborum
  2. rectus abdominis
  3. interior oblique
  4. exterior oblique

Which muscle pair plays a role in respiration?

  1. intertransversarii, interspinales
  2. semispinalis cervicis, semispinalis thoracis
  3. trapezius, rhomboids
  4. diaphragm, scalene
  1. a small muscle that helps with compression of the abdominal organs
  2. a long tendon that runs down the middle of the rectus abdominis
  3. a long band of collagen fibers that connects the hip to the knee
  4. another name for the tendinous inscription

Critical Thinking Questions

Describe the fascicle arrangement in the muscles of the abdominal wall. How do they relate to each other?

Arranged into layers, the muscles of the abdominal wall are the internal and external obliques, which run on diagonals, the rectus abdominis, which runs straight down the midline of the body, and the transversus abdominis, which wraps across the trunk of the body.

What are some similarities and differences between the diaphragm and the pelvic diaphragm?

Both diaphragms are thin sheets of skeletal muscle that horizontally span areas of the trunk. The diaphragm separating the thoracic and abdominal cavities is the primary muscle of breathing. The pelvic diaphragm, consisting of two paired muscles, the coccygeus and the levator ani, forms the pelvic floor at the inferior end of the trunk.


Respiratory muscles

The lungs have no skeletal muscles of their own. The work of breathing is done by the diaphragm, the muscles between the ribs (intercostal muscles), the muscles in the neck, and the abdominal muscles.

The diaphragm, a dome-shaped sheet of muscle that separates the chest cavity from the abdomen, is the most important muscle used for breathing in (called inhalation or inspiration). The diaphragm is attached to the base of the sternum, the lower parts of the rib cage, and the spine. As the diaphragm contracts, it increases the length and diameter of the chest cavity and thus expands the lungs. The intercostal muscles help move the rib cage and thus assist in breathing.

The process of breathing out (called exhalation or expiration) is usually passive when a person is not exercising. The elasticity of the lungs and chest wall, which are actively stretched during inhalation, causes them to return to their resting shape and to expel air out of the lungs when inspiratory muscles are relaxed. Therefore, when a person is at rest, no effort is needed to breathe out. During vigorous exercise, however, a number of muscles participate in exhalation. The abdominal muscles are the most important of these. Abdominal muscles contract, raise abdominal pressure, and push a relaxed diaphragm against the lungs, causing air to be pushed out.

The muscles used in breathing can contract only if the nerves connecting them to the brain are intact. In some neck and back injuries, the spinal cord can be severed, which breaks the nervous system connection between the brain and the muscles, and the person will die unless artificially ventilated.

Diaphragm’s Role in Breathing

When the diaphragm contracts and moves lower, the chest cavity enlarges, reducing the pressure inside the lungs. To equalize the pressure, air enters the lungs. When the diaphragm relaxes and moves back up, the elasticity of the lungs and chest wall pushes air out of the lungs.

Causes of Diaphragmatic Paralysis

Diaphragmatic paralysis is almost always due to problems with the nerves. Less frequently it is due to muscle problems affecting the diaphragm. Sometimes it arises for unknown reasons but at times it is termed idiopathic due to inadequate investigations.


Tumors may compress the phrenic nerve and malignant tumors (cancer) can also destroy the nerve. This is mainly seen with :

  • Bronchial carcinoma – most common cause
  • Metastatic lung cancer
  • Mediastinal tumors
  • Cervical spine tumors

Nerve disease

Disruption of nerve impulses to the diaphragm are the main reason for paralysis. Tumors, and in particularly bronchial carcinoma, are the most common causes of phrenic nerve damage that leads to diaphragmatic paralysis but other causes may include :

    where diseases of the cervical vertebrae causes nerve root compression (pinched nerve).
  • Trauma to the nerve with birth injuries or motor vehicle accidents.
  • Surgery that leads to accidental damage of the phrenic nerve. Mainly occurs with thoracic surgery.
  • Stretching of the nerves with an aortic aneurysm or other mediastinal masses.
  • Herpes zoster (shingles) which is a reactivation of the infection caused by varicella zoster (chickenpox virus). where the protective insulating sheath around the nerve is destroyed by the immune system.
  • Guillian-Barre syndrome is an autoimmune disorder where the body’s immune system specifically acts against nerves.
  • Amyotrophic lateral sclerosis (ALS) also known as Lou Gehrig’s disease where there is gradual loss of the nerve cells due to biochemical, genetic or autoimmune factors.
  • Polio where a viral infection disrupts the nervous system leading to muscle weakness. Post-polio syndrome that may arise years after recovering may also lead to diaphragmatic paralysis.

There are various other causes of peripheral neuropathy which is damage or disease of the nerves outside the brain and spinal cord that may lead to paralysis of the diaphragm. This includes diseases that may not specifically affect the nerves such as connective tissue diseases like systemic lupus erythematosus (SLE).

Muscle disease

Some diseases that affect the muscles of the body may also involve the diaphragm. These conditions are not specific for the diaphragm and there may be other areas affected with muscle weakness or even paralysis. Disorders of the muscle that may lead to diaphragmatic paralysis includes :

  • Injury to the diaphragm with severe trauma or during surgery.
  • Muscular dystrophy where the muscle becomes prone to damage due to deficiencies of certain proteins.
  • Polymyositis is disease where there is inflammation of the muscle leading to muscle weakness which appears to be due to autoimmune factors.

As with nerve diseases, certain inflammatory conditions may affect various tissues in the body and also involve the diaphragm.

Is the diaphragm made of two muscles? - Biology

in resting condition the vocal cords lie at the anacute angle to one another enclosing the glottis between their edges the larynx is called abducted. no sound is produced but at the time of sound production the vocal cords are regulated by action of set laryngeal muscles attached to the cartilage of the larynx and become parallel to each other the vocal cords come closer and glottis size is decreased .this is called chink of glottis now the foul air is passed through them under pressure from the lungs the glottis being narrow the air concentrates and increase the pressure behind the vocal cords ,which start vibrating and sound is produced larynx condition called adducted, containing the vocal cords the larynx also enable vocalized by manipulating these cords to vibrate at a desired pitch when air is passed through the larynx the pitch of the voice is highly dependent upon the elasticity and tension in these true voice cords when the angle of the thorid cartilage decrease in male during puberty.

A trachea

it is the short tube about 10 to 11 cm in length thin-walled tubular structure which turns run downwards through the neck in font of oesophagus extend up to 5 to vertebra it is supported by 16 to 20 dorsally in complete C-shaped cartilage tracheal ring which prevents its collapsing. it is lined by pseudo stratified ciliated epithelium with mucus secreting goblets cell the mucous and debris upward into the pharynx.
where on its swallowed when the upper trachea or pharynx become blocked so as to cut off airways .as from swelling of the tissue a small incision is made in the throat and into the trachea in an opening called tracheotomy which allows air to pass into the windpipe.

Primary bronchi

trachea in the posterior bifuracte into two bronchi right branch is about 2.5 cm in length and left bronchus is about 5 cm in length looks small thin-walled tubular structure formed by the division of trachea at the level 5 the thoracic vertebra near the heart. these are also supported buy cartilage ting each primary bronchus enters the lungs of its won side through the hilus and from a bronchial intercome.


the diaphragm is a thin muscular wall lies in between thoracic cavity and abdominal cavity. the intercostal and abdominal muscles are responsible for contacting and expanding the thoracic cavity to effect respiration .the ribs serve a structure support for the whole thoracic arrangement and pleural membranes help provide lubrication for the respiratory organs so that they are not chafed during respiration.


lungs are of soft elastic and spongy organ present in air tight thoracic cavity one either side of the heart .It is surrounded thin transparent two-layered peritoneal sac it inner and outer layer is respectively called visceral pleural and parietal pleuron the pleura of the thorax are the serous membranes which enclose the upper chest cavity the parietal pleuron is the exterior layer of the pulmonary pleural sac ,which connects to the thorax wall the mediastinal membrane and the diaphragm muscles.

2 plural membrane are continuous over the primary bronchus .at the hilum between this layer there is narrow pleural cavity filled a watery pleural fluid which performs three functions:-

1 allows free frictionless movement of leather and the lungs expanded,
2 protect the lungs from mechanical shocks,
3 keeps the pleura tog,

each lung is conical shaped having an upper narrow apex and lower broader base. its outer convex posterior semi lunar shaped and inner concave surfaces are called costal diaphragmatic and mediastinal ,surface through which blood and primary bronchus and nerves enter the lung.

each lung is donated organs and is divided externally into lobes by transverse and oblique grooves called fissure .the left lung divided into 2 lobes superior and inferior lobes while the right lungs is divided into 3 lobes superior middle and inferior lobes the right and left lungs are each enclosed in pleural sac and are separated by mediastinum membrane which extends from the vertebral column in back to the sternum in front between, the lungs is space for the heart this cavity is more pronounced on the left lungs which are slightly concave and is called cardiac notch the pericardium of the heart is in direct contact with the pleural lining of the lungs and is attached to the centrally placed tendinous portion of the diaphragmatic muscles.

Bronchial intercom

its network present inside the lungs formed by the division nad re-division of primary bronchus the bronchi are the tubes which carry air from the trachea to the inner recess of the lungs ,where it is can transfer oxygen to the blood in small air sac called alveoli. two main bronchi the right and left bronchus branch off the low end of the trachea in what is called tracheal bifurcation on the brounchus extends into each of the rights and left lungs right bronchus inside the lungs divides into three bronchi extends into each of the right and left lungs right bronchus inside the lungs divided into three smaller branches called secondary bronchi one bronchi to each lungs lobes.

Bronchial intercom

Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.

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Luke Smith

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Things to remember
  1. trachea in the posterior bifuracte into two bronchii right brounch is about 2.5 cm in length
  2. left bronchus is about 5 cm in length looks small thin walled tubular structure formed by the division of trachea
  3. diaphragm is a thin muscluar wall lies in between throcic cavity
  4. abodominal cavity the intercostal and abodominal muscles are responsible for contacting
  5. lungs are of soft elastic and spongy ogan present in air tight throcic cavity one either side of heart It is surrounded thin transparent two layered peritoneal sac it inner
  6. outer layer are respitively called visceral pleural
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.

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