What are lungs? Function and Embryonic development of lungs along with the diseases related to lungs

LUNGS

introduction

There are some needs of the body that must and should be fulfilled for its proper and optimum working. Bodies for their proper and normal functions require some materials from the external environment and oxygen is one of them. Oxygen is very crucial for the body as it is involved in many metabolic reactions of the body but the thing is that is not produced in the body and must be supplied from the outside environment. So the pathway that is responsible for the movement of this oxygen in the body is known by the name of respiratory system and in respiratory system there must be some organ at which all of the gaseous exchange must be taking place as it is not just enough to simply take oxygen in the body after taking in into the body it must be diffused into the blood so that it can reach its target site in the body and the structure in the body that is part of respiratory system and is responsible for this gaseous exchange goes by the name of lungs. In simple words the function of the lungs is the gaseous exchange between the body of the organism and its environment. They also makes the ability of speech possible as the voice is produced when air from the lungs vibrates the voice box and it is actually lungs where the oxygenation of the deoxygenated blood takes place it is not the heart that takes out carbon dioxide fro m the blood and pours oxygen in it is the function of the lungs the heart just simply supply the oxygenated blood in the body that it revives from the lungs. Lungs are spongy air filled organs and its precursor from where it is developed during the embryonic development is the foregut. In human and other organism that have lungs they are protected by a double serous membranous layer that goes by the name of pleura and between these two layers there is fluid that is known as the pleural fluid and this pleural membrane aids optimal functioning of the lungs during the process of breathing where as the pleural fluid acts as a lubricant that protects the lungs from any sort of friction that might damage the lungs and also allows pleura to slide effortlessly against each other during the respiratory movements. Both of the lungs hold the heart tight between them and thus by it protects it. Like that of the kidneys lungs have a hilum and it the point in the lungs where all of the structures enter or leave the lungs such as it acts as a entry or exit point for the lungs. The trachea and the bronchi airways form an upside down Y and therefore because of this Y shape it is also known as the bronchial tree. In humans and other mammals there is a pair of lungs that is present in the thoracic cavity and are protected by the ribs and between the ribs and the lungs there are the intercostal muscles lungs are conical in shape if we talk about the sides and the anatomical boundaries of the lungs than we can say that it have 

• costal surface
• medial surface 
• apex 
• base 
• anterior boundary
• posterior boundary 
• inferior boundary 

Lungs gets functional after birth such that when the lungs are formed in the fetus is held in the fluid filled amniotic sac and so they do not function to breath blood is also diverted from the lungs through the ductus arteriosus however at the time of the birth air begins to pass through the lungs and hence the diversionary duct closes so that the lungs can begin to respire therefore is is very important for a newly born baby to cry because the first cry of the baby inflates its lungs with air and it for the first time that newly born baby inhales air through its own lungs. like nephrons are the structural and the functional unit of the kidneys the structural and functional unit of lungs where all of the respiratory activities or gaseous exchange takes place goes by the name of the alveoli and combined in both of the lungs there are about 300-500 million alveoli. The left and the right lungs are not identical to each other there are differences between the left and the right lungs. Each lungs is divided into lobes and these lobes are formed by the unfolding of the pleura as fissures and if you observe lungs from outside it will look like there are cuts on the lungs that are basically the lobes that are separated from each other. The right lung as compared to the left lung is slightly heavier as it have three lobe whereas the left lung have two lobes such that the right lung have a upper middle and a lower lobe that are separated by fissures. The mediastinal surface of the right lung is indented by a number of nearby structure such as heart such that the heart sits in an impression that is known as the cardiac impression. The average weight of right lung in males and females is 150-720 grams and 100-560 grams respectively and this value may differ in different people whereas the weight of the left lung in males and females is about 110-660 grams 100-515 grams respectively and also this valve varies according to persons. The left lung is divided into three lobes that are the upper and the lower lobe and they are also separated by fissures. The combined weight of both of the lungs is about 1.3 kg lungs are brownish or grey in color. Lungs in human body is present in the thoracic cavity and they are present on each side of the mediastinum. Below the lungs there is a muscular structure that is known as the diaphragm that aids the lungs during the respiratory activities such as during the relaxation and the contraction of the lungs. In an adult human when the lungs are fully inflated the total inside capacity of lungs is about 5 litres which is also known as the tidal volume or the total lung capacity normally when we are resting or sleeping the gaseous exchange is only about half a litre the gaseous exchanging volume that the volume of air that is taken inside the lungs and is than expelled is about 3.5 while out of total 5 litres of air 1.5 litres of air always remains in the lungs and it is known as the residual volume and it presents the lungs from collapsing as the lungs would be collapsed if there would be no air in it. Typically a man's lungs can hold more air than a women such that at rest male and female lungs can hold around 1.5 pints of air and 0.6-0.8 pints of air respectively such that it is also studied that in healthy people without any sort of chronic lung disorder and even at maximum exercise we only use 70% of the lung capacity. Adults typically take 15 - 20 breaths per minute where as the breathing rate of newly born baby is about 40 times per min but in adults this rate increase with that of physical activity such that the breathing rate depends upon the oxygen levels in the blood less the oxygen in blood more frequent will be breathing and vice versa. For any organ to work properly there are some supplies given to that organ that must be given properly and should be regulated and without which that organ can't work properly and same is the condition with the lungs and these supply demands of any organ are the

• blood supply 
• nervous supply 
• lymphatic supply 

if we talk about the blood supply of the lungs than lets consider the arteries that supply oxygenated blood to the lungs and they are as following

• the oxygenated blood supply for the lungs itself is provided by the bronchial arteries 
• where as the deoxygentaed blood coming into lungs for the oxygenation comes from the pulmonary artery 

as lungs have two types of blood supply or circulation as they as

• pulmonary circulation 
• bronchial circulation 

if we talk about the venous blood supply of the lungs than the venous blood of the bronchi is carried out by the bronchial veins
where as if we talk about the nervous supply or the innervation of the lungs than we can describe it as that lungs are supplied by the nerves of the autonomic nervous system such that it gets input from the parasympathetic nervous system and it occurs through the vagus nerve. The action of breathing takes place because of nerve signal sent by the respiratory center in the brain-stem along with the phrenic nerve from the central plexus of the diaphragm

embryonic development of lungs

The precursor of the lungs from which they develop during the time of embrogeneis is the foregut such that the lungs begins to develop as an out-pouching of the foregut such as they arise from the laryngotracheal groove and than continues to mature but they gets inflate for the first time after the birth as during the embryo or fetus state all of the requirements of the developing baby is completed by its mother. At the end of the 4th week of the embryonic development the lung bud divide into two bronchial buds that are the 

• left bronchial bud 
• right bronchial bud 

and at the start of the 4th week of the embryonic development many important structures of the respiratory system such as the trachea larynx and bronchi starts to develop and during the 5th week there is formation of the lobes of the left and the right lungs such that the left and right bronchial buds that were formed during the 4th week of embryonic development starts to form secondary bronchial buds that would ultimately would be converted into buds such that the right bud branches into three secondary bronchial buds that would than form the three buds of the right lung and same is the case with the left lung such that the left bronchial buds branches into two secondary bronchial bud that would ultimately form the two lobe of the left lung from the sixth to the sixteenth week the major elements of the lungs appear except for the alveoli. The developing lung is particularly vulnerable to changes in the levels of vitamin A if there is a deficiency of vitamin A during the time of development of lung than there would be negative and unwanted changes in the epithelial lining of the lung and also in the lung parenchyma that is all the functional part of the lungs and this is among one of the importance of vitamin A during the time of embryonic development. There are a of major changes that occur in newly born baby and these occurs after few hours of birth such that at the time of birth the newly born baby's lungs are filled with fluid secreted by the lungs as they are also non inflated after birth the infant's central nervous system reacts to sudden environmental changes and this triggers the first breath and this occurs about 10 seconds after delivery and first cry of the baby is the indication of the inflation of lungs with air     

function of lungs

The main and the most important function of the lungs is the gaseous exchange between the body and the external environment it is also involved in speech formation as the air that vibrated the voice box comes from the lungs if we consider the respiratory pathway than it is as following 

• external nostrils 
• nasal cavity 
• internal nostrils 
• pharynx 
• larynx 
• trachea
• primary bronchi 
• secondary bronchi 
• tertiary bronchi 
• terminal bronchioles 
• respiratory bronchioles 
• alveolar duct 
• alveoli sacs 
• alveoli 

There are about 30 thousand bronchioles in each lungs and they are so tiny that they have the thickness of a hair. The trachea and the bronchi airways form an upside down Y and because of this Y shape it is often called as the bronchial tree. Such that the external air from the outside is drawn into the body through the external nostrils than after that in nasal cavity at the level of nasal cavity the incoming air is warmed to the temperature of the body and there is also trapping of dust or any other unwanted particles through the hairs and the mucus after which the air moves into the pharynx which is a muscular passage and is common for both food and air after which it goes into the larynx which is also known as the voice box of the body after which air goes into trachea and hence passing through the bronchi and bronchioles it ultimately reaches the alveoli where all the gaseous exchange takes place such that carbon dioxide diffuses out of the blood and the oxygen diffuses into the blood and this only occurs at the level of alveoli because of its some specific and peculiar properties and also the fact that alveoli are surrounded by blood rich capillaries and they are the site of oxygenation of the blood after the blood revives the oxygen it goes into the heart so that is can be pumped into the body after a cycle of gaseous exchange takes place the air is removed through the same passage and more fresh air is taken in to carry out this process again and again. Lungs also have protective system that protects it from any harmful material that may be present in the air such that for this purpose there are hair like structures present in the whole respiratory tract that are known as the cilia that beat rhythmically and carry mucus. The dust particles and bacteria in the inhaled that escapes from the nasal cavity are caught up by the surface of the respiratory tract and they are removed out of the body by the rhythmic upward beating action of the cilia lungs posses several characteristics which protect it against infections such as goblet cells secretes mucous and the there is also secretion of the immunoglobulin A by the lining of the lungs there is also release of adaptive immune system cells defensins antiproteases and antioxidants. 

disorders of the lungs

Despite of the normal regulated activities of the lung many abnormalities can occur in lung it can be because of any reason anything that interferes with the normal functions of the lung can cause a abnormality there can be a lot of reasons as a result of which a person can get a lung sickness and some of the are as following

• bacteria or bacterial infection  
• viral infections 
• fungus 
• polluted air 
• inhaling for a long time in stagnant air 
• cigarette 
• tobacco 
• second hand smoke 
• chemical 
• allergic reactions 
• genetic disorders 
• pollen 
• dust 

there are some specific symptoms that are shown in the body or that appears as a result of lung disorder of lung disease and some of these general symptoms are as following 

• chronic cough 
• breath shortness
• chronic mucus 
• chest pain 
• trouble breathing 
• feeling like you are not getting enough air 
• constant cough 
• coughing blood
• coughing mucous 
• pain or discomfort while breathing 
• wheezing 
• over production of mucous

there are various test that are used to detect any type of abnormality in the lungs and these test are as following 

• magnetic resonance imaging 
• rigid bronchoscopy 
• flexible bronchoscopy 
• lung biopsy 
• sputum cytology 
• sputum culture 
• spirometry 
• pulmonary functional test 
• computed tomography 
• arterial blood gas test 
• complete blood test 
• chest x rays
• exhaled nitric oxide test 
• lung diffusion capacity 
• pulse oximetry 
• spirometry 
• mucus sample 

where as many treatments or methods used to treat lung disorders or problems are as following 

• lung resection 
• vasodilators 
• chemotherapy 
• radio therapy 
• lung transplant 
• continuous positive airway pressure 
• mechanical ventilation corticosteriods  
• bronchodilators 
• antiviral drug 
• antibiotics 
• pleurocentesis
• chest tube 
• video assisted thorascopic surgery 
• thoracotomy 
• antibiotics 
• anti viral medications 
• anti fungal medications 
• anti inflammatory medications 
• inhaled bronchodilators 

also there are some ways through which we can detoxify or clean our lung or also some preventive measures that we can following to have healthy lungs and they are as following 

• steam therapy 
• controlled coughing 
• exercise 
• drain mucus from the lungs 
• green tea 
• anti inflammatory foods 
• chest percussion 
• avoid smoking 
• avoid second hand smoke 
• avoid pollution 
• wear mask in case of pollution 
• check your home for molds and if there are any than get rid of them 
• don't chew tobacco 
• get regular health check ups 

these were the symptoms treatments or precautions of lung disorders but the lung disorders are as following 

• asthma 
• chronic obstructive pulmonary disease 
• bronchitis 
• pneumonia 
• tuberculosis
• pneumothorax 
• severe acute respiratory syndrome 
• pulmonary embolism 
• pulmonary hypertension 
• pertussis 
• mesothelioma 
• influenza
• hypersensitivity pneumonitis  
• histoplasmosis 
• coccidioidomycosis 
• lung cancer 
• acute respiratory distress syndrome 
• interstitial lung disease
• cystic fibrosis 
• lymphangioleiomyomatosis
• bronchiectasis 
• pleural effusion 
• pleurisy 
• obesity hypoventilation syndrome 
• sarcoidosis 
• pulmonary fibrosis 
• acute bronchitis 
• chronic bronchitis 
• emphysema 

emphysema

It is a condition in which there is rupturing of the inner walls of the alveoli creating larger air spaces that reduces the surface area of the lungs which in turn reduces the oxygen that reaches the bloodstream when you exhale the damaged alveoli don't work properly and the air becomes trapped that leaves no room for fresh oxygen rich air to enter most of the people that are suffering from emphysema also suffer from the chronic bronchitis it is more common among smokers as the substances present in the smoke of tobacco weakens the walls of the alveoli and the irritant substances of the smoke generally causes smokers cough and that burst the already weakened alveoli and also a result of constant coughing the absorbing surface of the lung is greatly reduced  and hence the person suffering from the emphysema can't oxygenate his blood properly and least excretion of air with more concentration of carbon dioxide makes him breathless and exhausted some of the common symptoms of emphysema are as following 

• frequent lung infection 
• over production of mucus 
• wheezing 
• anxiety
• sleeping problems 

the main causes of emphysema are 

• tobacco smoke 
• marijuana smoke 
• air pollution 
• dust 
• chemical fumes 

this condition is generally treated with 

• antibiotics
• inhaled steroids
• bronchodilators 
• pulmonary rehabilitation 
• supplementary oxygen    
• lung volume reduction surgery 

bronchitis

In this condition there is an inflammation of the bronchial tubes that carries the air to the lungs it is further divided into two types that are 

• chronic bronchitis 
• acute bronchitis 

some of the common symptoms bronchitis that may be chronic or may be acute are as following 

• cough 
• over production of mucus 
• fatigue 
• shortness of breath
• fever 
• chills 
• chest discomfort 

the major cause of bronchitis mainly in case of chronic bronchitis is smoking there is one cause that would be associated with all of the respiratory disorders and it is smoking or it may be caused as a result of airborne chemicals or by 

• dust 
• certain fumes  
• burning coal 
• fire smoke 
• air pollution 

pulmonary fibrosis

It is a condition of lungs that occurs when lung tissues become damages or scarred such as this thickened stiff tissues where there as damage before makes it difficult for the lungs to work properly such that at that point the lungs would constrict and there would be less space for the air to pass the lungs damage caused by pulmonary fibrosis cannot be repaired but by the use of different medications and therapies can sometimes help to ease symptoms and improve quality of life some of the symptoms are that associated with this disorder are as following 

• shortness of breath 
• dry cough 
• fatigue 
• unexpected weight loss
• aching muscles and joints