respiratory system- organs and their function

What is Breathing? The oxygen of the inhaled air is absorbed by the blood in the lungs where it combines with the hemoglobin present in the red blood cells. the oxygen is carried from the lungs to the body tissues or cells where the oxygen is utilized and carbon dioxide is released. breathing is also called external respiration.it is a physical process. It involves inhalation and exhalation.

Respiration occurs in three phases

1. Breathing,
2. Gaseous transport and,
3. Cellular respiration.

breathing is a physical process that inhalation oxygen from the air and carbon dioxide from the lungs called breathing. the average breathing rate in an adult man at rest is about 15 to 18 times per minute. rate of breathing increases with increased physical activity. thus we breathe faster to produce more energy.

The process of releasing energy from food is called respiration. in this process, oxygen burns the food in the cells of the body to release energy and waste product like carbon dioxide and water which are eliminated from the body as waste products. 

The process of respiration takes place inside of the body so it is also called cellular respiration. it provided energy to the cells. respiration is necessary for the life process which keeps the organism alive. In human many organs take part in the process of respiration.

The two bronchi lead into the right and left lungs respectively. each bronchus is further divided into smaller and smaller branches called bronchioles. in the end, these bronchioles are the microscopic air sacs called alveoli. each lung contains millions of alveoli (singular alveolus). the walls of the alveoli are very thin. these are richly supplied with blood capillaries covering their walls. it in the alveoli that oxygen is taken into the body and carbon dioxide is eliminated. the walls of the alveoli are extremely thin and moist for allowing faster diffusion of gases.

In human beings air (oxygen) taken into the body through the nostrils. from here, the air passes through the throat and into the lungs. within the lungs, the passage divided into smaller tubes which finally terminate in a balloon-like structure which is called alveoli. the alveoli provide a surface where the exchange of gases can take place. the wall of the alveoli contains an extensive network of blood vessels. when we breathe in, our ribs and flatten our diaphragm and the chest cavity becomes larger as a result. air is sucked into the lungs and fills the expanded alveoli. the blood brings carbon dioxide from the rest of the body for release into the alveoli and the oxygen in the alveolar air taken up by the blood in the alveolar blood vessels to be transported to all cells in the body. during the breath cycle, when air is taken in and let out the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released. the respiratory pigment is present in the red blood corpuscles. carbon dioxide is more soluble in water than oxygen is and hence is mostly transported in the dissolved form in our blood.  

Respiratory organs:

1. Nose,                       
2. Nasal cavity,  
3. Trachea, Bronchi, 
4. Lungs and, 
5. Diaphragm.

The nose: The nose is the point of entry for air.it has two openings called nostrils, each leading nasal chamber. the nostrils have a hairy lining to prevent dust particles from reaching into the lungs. the lining of the nasal chamber has mucus which too traps germs and dust. the nasal chamber warms and moistens the air entering into the lungs. the inner lining f nose also has some special cells for the smell.

The pharynx: From the nose, the air passes behind the mouth into the pharynx or throat. which is a common passage for air and food. It leads to an air tube called a windpipe or trachea.

The larynx: The upper end of the trachea has a voice box called the larynx. it contains two ligamentous folds called vocal cords (air expelled forcibly through the vocal cords vibrates them to produce sound). The front opening (glottis) of the windpipe is guarded by a muscular flap called epiglottis. the epiglottis closes the windpipe at the time of swallowing of food. incomplete closure by the epiglottis during swallowing causes coughing as the food wrongly enters the windpipe.

Trachea (windpipe): The trachea runs down the neck and divides into two smaller tubes called bronchi (singular bronchus) at its lower end. the two bronchi are connected to the two lungs. the wall of the trachea is strengthened by C- shaped rings of cartilage to prevent it from collapsing. the inner linings of the trachea, bronchi, and bronchioles have ciliated epithelium. the continuous movement of the cilia pushes out the unwanted particles that may be present in the inhaled air.

The lungs: The lungs are a pair of pink and spongy, elastic organs protected by the rib cage. the left lungs are slightly smaller with two lobes and the right lung has 3 lobes. the lungs rest on a diaphragm. the diaphragm is a sheet of muscle below the lungs. it helps in breathing in and breathing out. this is a muscular sheet that internally divides the body into two cavities-the chest cavity or thoracic cavity above, and the abdominal cavity below. the lungs are protected from outside by two membranes called the outer and inner pleura. the space between the two membranes is filled with fluid. this fluid acts as a shock absorber and so protects the lungs.

Gaseous exchange in the lungs:

The proportion of oxygen, carbon dioxide, and water vapor in the inhaled air and exhaled air as:

Inhaled air:

Component       Inhaled air   

                                                                                 
carbon dioxide-                           0.04%     

Nitrogen-                                      79%   

                                                                                                                   
                          Exhaled air:

Oxygen-                                      16.4%

carbon dioxide-                          4.4%

water vapor-                                a lot.

Types of respiration:

There are two types of respiration.some organism use oxygen to break down glucose completely into carbon dioxide and water, some use other pathways that do not involve oxygen. The first step is the break-down of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. this process takes place in the cytoplasm, the pyruvate may be converted into ethanol and carbon dioxide. this process takes place in yeast during fermentation. since this process takes place in the absence of oxygen it is called Anaerobic respiration.

1. Anaerobic respiration: respiration that does not utilize oxygen.
2. Aerobic respiration: respiration that utilizes oxygen

Respiration process: The process of releasing energy from food is called respiration. in this process, oxygen burns the food in the cells of the body to release energy and waste product like carbon dioxide and water which are eliminated from the body as waste products. the process of respiration takes place inside of the body so it is also called cellular respiration. it provided energy to the cells. respiration is necessary for the life process which keeps the organism alive. respiration is a biochemical process of oxidation of food. the process of respiration takes place in mitochondria in the cells where food is oxidized and releases energy.

Phases in respiration:

Food    +   Oxygen    →  Carbon dioxide    +   water   +   Energy.
Energy stored in cellular respiration:

all the energy released during respiration is not used immediately by the organism. it is stored in the form of ATP molecules in the cells of the body and used by the organism when required.

ADP     +     Phosphate     +      Energy      →        ATP.

Energy release:                                                                           
The energy released during this process is 30.5 KJ/mole. the energy released by ATP is used in the cells for the contraction of muscles, protein synthesis, conduction of nerve impulses, and many other activities.

Anaerobic respiration:                                                                                                                             
Break down of pyruvate using oxygen takes place in the mitochondria. this process breaks up the 3 - carbon pyruvate molecule to give 3 molecules of carbon dioxide and water. since this process takes place in the presence of oxygen, it is called aerobic respiration. the release of energy in this process is a lot greater than the anaerobic process. aerobic organisms need to ensure that there is a sufficient intake of oxygen.

Glucose 1 molecule (glycolysis/in the cytoplasm) → Pyruvate, (pyruvic acid 2 molecules) 
(Oxygen(Kreb's cycle)/mitocondria) → 6 CO2 (Carbon dioxide) +  6 H2O (water) +  38 ATP (Energy).

Functions of the respiratory system: 

Breathing is a physical process that inhalation oxygen from the air and carbon dioxide from the lungs called breathing. the average breathing rate in an adult man at rest is about 15 to 18 times per minute. rate of breathing increases with increased physical activity. thus we breathe faster to produce more energy.

The respiratory system performs the following function:

1. Oxygen is taken inside the body,
2. carbon dioxide expelled from the body,
3. respiration,
4. exhaled water vapor,
5. exhaled waste substances.

What causes muscle cramps?
When the lack of oxygen in our muscle cells, another pathway for the breakdown of pyruvate is taken. the pyruvate is converted into lactic acid which is also a 3 carbon molecule. this build-up of lactic acid in our muscles during sudden activity causes cramps.
Some common respiratory diseases: respiratory diseases caused by smoking

Respiratory diseases examples:

1. Bronchitis,
2. Asthama,
3. Pneumonia,
4. Tuberculosis.

Gaseous transport:

ATP is the energy currency for cellular processes. the energy released during the process of respiration is used to make an ATP molecule from ADP and inorganic phosphate.

ADP ( Adenosine Di-Phosphate) is present in the cells and low energy content. whereas ATP (Adenosine Tri-phosphate) high energy content present in the cells. and Inorganic phosphate is a substance that contains a phosphate group and made up of phosphorus and oxygen and present in the cells.ADP contains 2 phosphate group and ATP contains 3 phosphate groups.

Energy stored:

  

ATP     →     ADP            +     phosphate     +       Energy. 

ADP can be converted to ATP by absorbing energy produced during respiration and ATP can be converted back to ADP releasing energy to be used by the cells again.