respiratory system
INTRODUCTION
It is a system consisting of respiratory passage and respiratory organs. Respiratory organs are a pair of lungs.
Respiratory passage:- It is a passage that takes air from outside to the respiratory surface of lungs. It is consists of a pair of nostrils, nasal cavity, apair of internal nares, pharnx, larynx, trachea, bronchi and their branches and the respiratory surface of lungs, i.e. alveoli
Structures involved in respiratory passage:-
- External nostrils:- A pair of external nostrils represent the first part of respiratory passage. These are the holes of our nose opening out above the upper lips. These lead into nasal chamber of nasal cavity through the nasal passage.
- Nasal chambers:- These are also two in number. The epithelial lining of cavities is known as respiratory epithelium. It has pseudostratified, ciliated, columnar, epithelium with sensory neural epithelium and goblet cells which secret mucus. It is richly supplied with blood vessels.
- Mucus from goblet cells and glands makes the surface sticky for trapping dust particles present in the inspired air.
- Moisture from the epithelium also makes the air humid.
- It brings the temperature of the incoming air, upto the body temperature.
3. Internal nares:- These are posterior openings of the nasal cavities that lead into the nasopharynx.
4. Nasopharynx:- Internal nares open into a part of pharynx known as nasopharynx. It is a portion of pharynx. Only air passes through nasopharynx. It open into the trachea through glottis of larynx region. Glottis is the opening at the upper part of larynx. Pharynx is common passage for both food and air. The pharynx opens through larynx region into trachea.
5.Larynx:- it is also known as sound/voice box because it helps in the production of sound. It is made up of cartilage, present at the upper part of trachea. Its upper part has an opening, i.e glottis. During swallowing, this glottis can be covered by epiglottis which is a leaf-shaped cartilaginous structure made up of elastic cartilage. Epiglottis is the covering or lid of glottis to prevent the entry of food into the larynx during swallowing.
6. Trachea:- It is also known as wind pipe. It is straight tube extending upto the mid-thoracic cavity, commonly called chest cavity. This tube finally divides into right and left primary bronchi at the level of 5th thoracic vertebra. It is lined by incomplete cartilaginous rings to prevent it from collapsing during inspiration.
- Bronchi (plural), bronchus (singular):- Each bronchus undergoes repeated divisions to form its branches. These are secondary, tertiary bronchi and bronchioles. Bronchioles are the terminal branching of bronchi. Finally, bronchioles give rise to a number of very thin, well-supplied with blood vessels, irregular walled balloon-like structures called alveoli. The walls of the bronchi and initial bronchioles are supported by incomplete cartilaginous rings.
- Alveoli:- Bronchioles open into the alveolar ducts i.e a tube-like structure which lead into expanded passages, the atria which open into the alveolar sacs or air sacs. There are about 300 million of alveoli in two lungs. The membrane of alveoli is very thin, irregular and richy supplied with blood vessels. Due to very close contact of blood vessels with alveoli, the exchange of gases takes place easily.
Surfactant:- A surface active agent- lecithin secreted by type II alveolar epithelial cells, reduces surface tension between the alveolar fluid and air. It prevents collapsing of lungs alveoli.
Lead to lead to lead to
Bronchioles → Alveolar ducts → Atria → Alveolar sacs.
Lungs:- A pair of lungs is present in humans, lie in an air-tight chamber known as thoracic cavity or chest cavity. This cavity is formed dorsally by the vertebral column, ventrally by the sternum, laterally by the ribs. It is closed below by the diaphragm which is a dome-shaped structure
Made up of muscles and separates thoracic cavity from abdominal cavity.
- Membranes enclose the lungs:- Each lung is enclosed by two membranes known as pleura or pleural membranes. The outer pleural membrane is in close contact with the thoracic cavity whereas inner pleural membrane is in close contact with the lung surface. In between these two membranes, a narrow space is present known as pleural cavity. This pleural cavity is filled with a fluid secreted by pleural membranes known as pleural fluid.
- Functions of pleural fluid:– It lubricates the pleural membranes so that they may slide over each other without friction during breathing. If fluid is not present, then there will be damage to the membranes which finally affects the breathing.
- Internal structure of lungs:– The right lung is shorter by about 2.5 cm due to raised position of diaphragm on the right side to accommodate liver. The left lung is longer. It is, however, narrower than the right lung because it contains a cardiac notch for accommodating asymmetrically placed heart. Left lung is divisible by an oblique fissure into two lobes, left superior and left inferior. Right lung has two fissures, horizontal and oblique. They divide the right lung into 3 lobes – right superior, right middle and right inferior. The lobes are divided internally into segments and segments into lobules. Internally, lungs are made up of branching network of bronchi, bronchioles and alveoli. Network of bronchi include primary, secondary and tertiary bronchi. Alveoli are the main sites where actual diffusion of gases O2 and CO2 takes place between blood and atmospheric air.
Two parts of human respiratory system are:-
Conducting Part | Exchange or respiratory part |
This part consists of external nostrils, nasal chamber, internal nares, nasopharynx, trachea, bronchi and bronchioles (upto terminal bronchioles) Functions:- · Conducts air from external nostrils upto bronchioles. · Clears the incoming air by trapping dust particles present in it. · Makes the incoming air humid by providing moisture produced by epithelium of nasal cavities. · It brings the temperature of air upto the body temperature. | It includes alveoli and their ducts,
Function It is the main site of human respiratory system where diffusion of gases O2 and CO2 occurs.
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Steps involve in respiration:- Respiration is a complex process which occurs in number of steps.
These are:-
- Breathing:- It is simply the inhalation of atmospheric air and exhalation of CO2 rich alveolar air. It is also known as pulmonary ventilation.
2. Diffusion of gases between alveoli and blood:- Diffusion of gases O2 and CO2 takes place across the alveolar membrane to the blood capillaries surrounding it. The membrane is very thin and richly supplied with blood capillaries
- Transport of gases:- Blood is the medium for transport of gases O2 and CO2 , which transports O2 to the body cells from alveoli and CO2 from the body cells to alveoli.
- Diffusion of gases between blood and tissues:- O2 diffuses from blood to tissues and CO2 diffuses from tissues to blood.
- Utilisation of O2:- O2 is used by the body cells for the release of energy. Breakdown of glucose occurs in presence of O2 which produces CO2 water and energy. This is also known as cellular respiration as it occurs inside the cells. It is a biochemical reaction. The CO2 produced is eliminated out of the body.
Reaction involved is:-
C6 H12 O6 + 6O2 6CO2 + 6H2 O + Energy
Glucose Oxygen Eliminated Water Utilised to
(Present inside out of the perform bodily
the cells) body activities
Funfacts:
- The lungs are the only organs in the human body that can float on water.
- An average adult takes about 15 to 20 breaths per minute, totaling about 20,000 breaths per day.
- The right lung is larger and has three lobes, while the left lung has two lobes to make room for the heart.
- The total surface area of the lungs is roughly the same size as a tennis court.
- The lungs contain around 300 to 500 million alveoli, the tiny air sacs where gas exchange occurs.
- If the airways of the lungs were stretched out, they would cover about 1,500 miles.
- The diaphragm, a dome-shaped muscle below the lungs, plays a crucial role in breathing by contracting and relaxing.
- The lungs are part of the respiratory system, which also includes the trachea, bronchi, and diaphragm.
- The lungs help regulate the pH level of the blood by controlling the levels of carbon dioxide.
- During vigorous exercise, the lungs can move up to 100 liters of air per minute.
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