Human Respiratory System Class 10
All organisms use respiration as a beneficial process for release of energy. It is basically an oxidation process of food substances within the tissues to form CO2, and water with consequent release of energy. The energy produced is stored in the form of ATP (Adenosine Triphosphate, energy currency of cell) and CO2 and water are considered as the byproduct of this respiration process.
- Intake of oxygen from the environment.
- Stepwise oxidation of food with the help of incoming oxygen.
- Elimination of carbon dioxide produced as a byproduct in the process of oxidation.
- Release of small amount of energy during oxidation.
- Storing of energy so that it can released in useful forms (such as ATP).
Types of Respiration
There are mainly two types of respiration
It is the process in which intake of molecular oxygen and release of carbon dioxide occur simultaneously. The organisms that follow aerobic respiration are termed as aerobes.
Aerobic respiration occur in two ways
1. Direct Respiration
It involves the exchange of environmental oxygen with the carbon dioxide in the body cells without the use of respiratory organs or blood. For example; It occurs in aerobic bacteria, protists, plants, sponges, coelenterates, flatworms, roundworms and most arthropods.
2. Indirect Respiration
It occurs by the aid of special organs like skin, buccopharyngeal living cells, gills, lungs and blood. For example; It occurs in crustaceans, amphibians (frogs toads), many annelids, molluscs, reptiles, birds, mammals etc.
Phases of Indirect Aerobic Respiration Indirect respiration includes following two phases, i.e., external and internal respiration. These two phases are preceded by: preliminary phase called breathing.
It refers to the intake of oxygen by the blood from water or air into the respiratory organs and removal of carbon dioxide from it.
Internal Respiration (cellular respiration)
It includes following four processes.
- Uptake of oxygen by tissue cells from the blood via tissue fluid.
- Oxidation of food to provide energy, water and CO2 in tissue cells,
- Storage of energy produced by oxidation process in the form of phosphate bonds of ATP.
- Release of CO2 into the blood by tissue cells via tissue fluid.
It is the process in which energy is produced without the usage of oxygen. In this the organisms that carry out anaerobic respiration (called anacrobes), may or may not produce carbon dioxide.
For example, Yeast produce ethanol or ethyl alcohol. and CO2 (i.e., without using oxygen) by oxidising glucose.
C6H12O6 ——> 2C2H5OH + 2CO2 +Energy
Glucose Ethanol or Ethyl alcohol
Also some bacteria metabolise glucose to form lactic acid without using oxygen and without producing carbon dioxide.
C6H12O6 ——> 2CH3CHOHCOOH + Energy
Glucose Lactic acid
Anaerobic respiration is also known as fermentation. The flow chart showing oxidation of glucose in respiration is given below
various Organs of Human Respiratory System
The human respiratory system consists of various organs. The lungs is the main organ where exchange of respiratory gases, i.e., CO2 and O2 takes place. Various organs of the human respiratory system are
These are the holes of the nose through which air enters inside the body. These are paired openings that open into two nasal cavities.
The two nasal cavities are separated from each other by a thin, cartilaginous median vertical partition called nasal septum.
It comprises of nasopharynx, oropharynx and laryngopharynx. The pharynx provides passage to both air and food.
It is also called voice-box. Until puberty there is little difference in the size of the larynx in man and woman. Thereafter, it grows larger and becomes prominent in man, and is called Adam’s apple (in man.)
It is basically the upper part of trachea and allow the air to pass through it to reach trachea.
Trachea (wind pipe)
The larynx leads into a long tube, the trachea or wind pipe, bearing rings of hyaline cartilage which are incomplete posteriorly. At its lower end, the trachea bifurcates into a pair of primary bronchi, which enter the right and left lungs. Bronchi are reinforced to prevent their collapse and are lined with ciliated epithelium and mucous producing cells. These bronchi are further branched into small tubes and bronchioles. They are terminated into grape like sac clusters called alveoli. Alveoli This is surrounded by a network of thin walled capillaries.
These are paired structure located in the thoracic cavity, (i.e., one on either side of the heart.) The thoracic cavity is closed below by the diaphragm. Each lung is enclosed in two membranes called the pleurae. The lungs are soft, spongy and elastic organs, which are pinkish in colour. The Upper most portion of each lung is called the apex and the interior most portion is called the base.
Movement of Air through Respiratory System
Nostrils – Pharynx (throat) → Larynx (voice box)→ Trachea (wind pipe) → Bronchioles → Bronchi → alveoli → Blood capillaries → Tissues.
Mechanism of Respiration
Respiration occurs in three major steps namely breathing, exchange of gases and transport of gases. Breathing involves the inward (inspiration) movement of oxygen and outward (expiration) movement of carbon dioxide. Gaseous exchange is the process of exchange of gases between the alveoli (primary site of exchange) and the blood due to the difference in partial pressure of gases at different sites.
After gaseous exchange, O2 and CO2 are transported to their target sites in various forms. Oxygen is transported in dissolved state (30%) as oxyhaemoglobin (97%) to various body tissues. Likewise, CO, is transported in dissolved state (7%), as bicarbonate ions (70%) and as carbaminohaemoglobin (23%) to the lungs.
It is the process by which the chemical energy of “food” molecules is released and partially captured in the form of ATP. Carbohydrates, fats and proteins can all be used as fuels in it. Glucose is most commonly used example to examine the reactions and pathways involved with it. The process of ATP production in respiration is called oxidative phosphorylation.
There are four stages of cellular respiration namely glycolysis, Kreb’s cycle, electron transport chain (ETC) and oxidative phosphosylation.
Types Cellular Respiration
Oxidation of glucose (6C) to pyruvate (3C) Occur in the Cytosol of the cell.
Oxidation of acetyl CoA ; aerobic process. Occur in the mitochondria of the cell.
Passage of electrons to its ultimate acceptor by a series of coenzymes and cytochromes. Occur in mitochondria or chloroplast of the cell.