The Respiratory System

Respiration is a process of releasing energy by breaking down glucose for carrying out life processes.

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \xrightarrow{\text{enzymes}} 6\text{CO}_2 + 6\text{H}_2\text{O} + \underset{\text{chemical energy}}{38 \text{ ATP}} + \underset{\text{heat energy}}{420 \text{ kcal}}$

The energy liberated in respiration is in the form of ATP (adenosine triphosphate).

1. Synthesis of proteins from amino acids
2. Production of enzymes

1. False
   Corrected Statement— Strenuous physical exercise may cause fatigue due to accumulation of lactic acid.
2. True
3. False
   Corrected Statement— Breathing and gaseous transport are first two steps of the four step respiration process in humans and animals.
4. True
5. False
   Corrected Statement— Cellular respiration means chemical changes occurring inside the cell.

1. During inhalation, the ribs move upwards and outwards due to contraction of the external intercostal muscles stretched between them. This enlarges the chest cavity.
2. The diaphragm flattens, expanding the chest cavity lengthwise. This increases the volume and decreases the pressure inside the lungs. Air is then drawn in from outside to equalize the pressure.

1. At higher altitudes, the density of air is less and amount of oxygen is also less. This causes deficiency of oxygen in the body which further results in dizziness and unsteady vision.
2. Lime water is used in most experiments on respiration as lime water turns milky when it comes in contact with carbon dioxide. It is thus an easy way to detect carbon dioxide.
3. Animals lead an active life where physical movement is involved and have complex organ systems that require constant energy supply. Hence, respiration rate is higher in animals than in plants to meet the higher energy requirements.

The mistake in the diagram is that the balloons are expanded and air is rushing in when the rubber sheet is pushed upwards. In the correct experiment, when the sheet is pushed upward, the volume is decreased, pressure inside the jar increases and balloons collapse due to air rushing out.

Contracts

Reason — During inspiration, the chest is expanded and the diaphragm contracts.

Alveoli

Reason — Alveoli is the part of respiratory system where the gaseous exchange occurs.

Loss in dry weight

Reason — Respiration burns glucose to form carbon dioxide (which escapes) and releases energy. This leads to loss in dry weight.

Lactic acid

Reason — The product of anaerobic respiration in animals is lactic acid. No CO₂ is produced.

Skeletal muscles

Reason — Anaerobic respiration in animals mostly occurs in skeletal muscles when they have to work very fast with insufficient oxygen.

Larynx

Reason — Larynx or voice box is called as Adam's apple.

Alveolus

Reason — Alveolus is the basic structural and functional unit of a lung as the gaseous exchange occurs in alveolus.

Pleura

Reason — The lungs are protected by pleural membrane and pleural fluid.

Diaphragm

Reason — The muscular sheet which separates the thoracic and abdominal chamber of the human body is Diaphragm.

Goblet cells

Reason — Goblet cells make mucus which traps dust particles.

Both contract

Reason — During inspiration the diaphragm contracts and moves downward, increasing the vertical space in the thoracic cavity. The external intercostal muscles also contract, pulling the ribs upward and outward, increasing the volume of the chest cavity. This increases the thoracic volume and reduces pressure, allowing air to flow into the lungs.

Both A and R are False.

Reason — The combination of carbon dioxide with haemoglobin forms carbaminohaemoglobin, not carboxyhaemoglobin. Carboxyhaemoglobin is formed when carbon monoxide (CO) binds with haemoglobin not CO₂.
RBCs carry carbon dioxide as carbaminohaemoglobin. Carboxyhaemoglobin is not involved in normal CO₂ transport; it is formed due to CO poisoning.

A is False and R is True.

Reason — The epiglottis does not guard the oesophagus. Instead, it guards the entrance to the trachea (windpipe). During swallowing, it closes the tracheal opening to prevent food from entering the windpipe.
The epiglottis covers the glottis (opening of the trachea) during swallowing to send food into the oesophagus.

A is True and R is False.

Reason — The pulmonary artery originates from the right ventricle of the heart. It carries deoxygenated blood to the lungs for oxygenation. It is the only artery that carries deoxygenated blood.
The right ventricle pumps deoxygenated blood, not oxygenated. The pulmonary vein does not carry blood from the heart to the lungs; it carries oxygenated blood from the lungs to the left atrium of the heart.

Both A and R are True.

Reason — During inspiration, the diaphragm contracts and moves downward, becoming flat. This increases the volume of the thoracic cavity, allowing air to flow into the lungs. During expiration, the diaphragm relaxes and returns to its dome-shaped position. This reduces thoracic volume and pushes air out of the lungs.

A is False and R is True.

Reason — Asphyxiation may result due to several causes such as strangulation, drowning or any obstruction in the respiratory tract. It does not happen due to carbon monoxide.
Asphyxiation involves accumulation of more carbon dioxide and Hypoxia is the deficiency of oxygen reaching the tissues.

(a) ATP

(b) Oxy-haemoglobin

(c) Pharynx

(d) Diaphragm

(e) Carbamino-haemoglobin

(a) Epiglottis

(b) Capillaries

(c) Diaphragm

(d) Red Blood Cells (RBCs)

(e) Ribs

(f) Air sacs / Alveoli

(a) Aerobic respiration and Anaerobic respiration

(b) Glycosis and Krebs Cycle

(c) Inhalation and Exhalation

(d) Glucose and Oxygen

(e) Dead Air space (150 ml) and Alveolar air (350 ml)

Nose → Pharynx → Larynx → Trachea → Bronchi → Lungs

The following table depicts the gas composition in percentage:

The Nose helps to breathe and smell. The nasal chamber opens at the back into a wide cavity, called Pharynx situated at the back of the mouth. It leads into an air tube, called Trachea and the Oesophagus located dorsally behind the windpipe. The entrance to the windpipe is guarded by a flap called Epiglottis which closes at the time of swallowing food.

(a) Alveoli and gaseous diffusion.

(b) Mitochondria and cellular respiration.

(c) Epiglottis and swallowing food.

(d) Pleura and protection of the lungs.

(e) Diaphragm and breathing.

(f) 'C' shaped cartilage rings and support and strengthen trachea.

(a) Ciliated epithelium lining the respiratory tract — The entire lining of the larynx, trachea, bronchi and bronchioles is formed of ciliated epithelium. It is the protective inner lining of the respiratory passage. It helps in motion, driving any fluid that is on them.

(b) Mitochondria — In mitochondria, pyruvic acid is further broken down step by step in a cyclic manner in the presence of oxygen.

(c) Diaphragm — Diaphragm contributes to the enlargement of the chest cavity lengthwise.

(d) Intercostal muscles — The muscles help the inward and outward movement of ribs enlarging the chest cavity all around.

(e) Pleural fluid — It provides lubrication for free movement of the contracting and expanding lungs.

Breathing rate can increase under the following circumstances:

1. Accumulation of carbon dioxide in blood.
2. Vigorous physical exercise.

During breathing, the air expelled out is always warmer or at the body temperature. It can be felt by breathing out the air on our own hand. One can feel the warmth of the air expelled out during breathing.

The nasal cavity is lined by ciliated epithelium and mucous glands. The mucous glands secrete mucous. The ciliated epithelium is present on the entire lining of the trachea, larynx, bronchioles and bronchi. The constant motion of cilia and mucous trap dust, micro-organisms, pollen and other minute particles present in the air. In this way, the respiratory passage is kept free of dust particles.

We inhale air containing much oxygen and very little carbon dioxide and exhale air containing less of oxygen and more of carbon dioxide. Therefore, the statement “We breathe in oxygen and breathe out carbon dioxide” is wrong.

(a) Aerobic respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP + 420 kcal

(b) Anaerobic respiration in plants
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2ATP

(c) Anaerobic respiration in animals
C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + 2ATP

(d) Photosynthesis
6CO₂ + 12H₂O $\xrightarrow[\text{chlorophyll}]{\text{sunlight}}$ C₆H₁₂O₆ + 6H₂O + 6O₂↑

(e) Phosphorylation
ADP + P_i (inorganic phosphate) → ATP

(a) Respiration — Respiration is the biochemical process of releasing energy by breaking down glucose for carrying out life processes.

(b) Hypoxia — Hypoxia is the deficiency of oxygen reaching the tissue. It may occur due to over crowding with poor ventilation or at high altitudes.

(c) Asphyxiation — Asphyxiation is a condition in which the blood becomes more venous by accumulation of more carbon dioxide and the oxygen supply is diminished.

(d) Breathing — Breathing is a physical process in which the atmospheric air is taken in and forced out of the oxygen-absorbing organs, the lungs.

(e) Vital capacity — Vital Capacity is defined as the volume of air that can be taken in and expelled out by maximum inspiration and expiration. It is 4500 ml.

(a) Aerobic and anaerobic respiration (end products of the process)

(b) Respiration and photosynthesis (gas released)

(c) Photosynthesis and respiration (reactants)

(d) Respiration and breathing (organs involved)

(e) Tidal volume and residual volume (quantity of air)

(a) Breathing through the nose is said to be healthier than through the mouth because the external part of the nose bears two nostrils separated by a cartilaginous septum. The hairs present in the nostrils prevent large particles from entering the respiratory system. So, always breathe through the nose and not through the mouth.

(b) Not all air is expelled from the lungs during expiration. A certain volume of air (about 1500 ml), known as the residual volume, remains in the lungs after a normal breath out. This residual volume maintains some oxygen in the alveoli, contributing to continued gaseous exchange.

(c) A person feel breathlessness at higher altitudes because as we go higher up, the air we breathe in decreases in pressure accompanied by a gradual decrease in oxygen content.

(d) We shiver and our teeth chatter when it is very cold in winter in order to increase the heat production in the body. To maintain the temperature of the body constant in extremely cold conditions, the production of heat is increased through heightened metabolic rate and greater muscular activity and shivering and teeth chattering involves a lot of muscular activity.

(a) The two muscles that help in breathing are — intercostal muscles and abdominal muscles.

(b) When the intercostal muscles stretch between the ribs, they move outwards and inwards causing them to enlarge the chest cavity.

(c) The overall chemical equation for the process of respiration in humans is as given below:

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \xrightarrow{\text{enzymes}} 6\text{CO}_2 + 6\text{H}_2\text{O} + \underset{\text{chemical energy}}{38 \text{ ATP}} + \underset{\text{heat energy}}{420 \text{ kcal}}$

(d) The meanings of Residual air and Dead air space are as follows:

1. Residual Air — Even after forcibly breathing out, some air always remains in the lungs. This air is referred to as residual air. The volume of this air is 1500mL.
2. Dead air space — Some tidal air is remaining in the respiratory passages such as bronchi and trachea. Here no gas diffusion takes place. This volume is referred to as dead air space and its volume is 150mL.

The path taken by the transpired air through the nostrils until it reaches the air sacs is as follows:

Nose → Pharynx → Larynx → Trachea → Bronchi

(a) Ribs — The ribs move upwards and outwards due to the contraction of the external intercostal muscles stretched between them thus enlarging the chest cavity all around. (The internal intercostal muscles are relaxed).

(b) Diaphragm — The diaphragm contracts and flattens from the dome shaped outline to an almost horizontal plane and thus contributes to the enlargement of the chest cavity lengthwise.

(c) Abdominal muscles — It helps to increase the size of the thoracic cavity through the motion of the diaphragm which assists in inspiration.

(i) The parts numbered 1-4 are:

• 1 → Thin walls of capillary
• 2 → Red blood corpuscles
• 3 → Plasma
• 4 → Thin wall of alveoli

(ii) Arrows at 5 & 6 indicate diffusion of carbon dioxide outside and diffusion of oxygen inside respectively.

(a) The process is anaerobic respiration.

(b) The reaction is applicable to animals only.

(c) The reaction may occur in skeletal muscular tissues.

(i) Anaerobic respiration in plants - 5

(ii) End-products in aerobic respiration - 4

(iii) Reaction occurring in liver - 2

(iv) Anaerobic respiration in animals - 1

(v) Storage in the liver – 3

(b) The corresponding reaction number is as follows:

(i) Aerobic respiration - 4

(ii) Change taking place in the liver - 3

(iii) Anaerobic respiration in yeast - 5

(iv) Change taking place in a plant storage organ, e.g., potato - 2

(v) Anaerobic respiration in animals - 1

1. Tidal volume — It is the air breathed in and out in a normal quiet breathing. The tidal volume(TV) is 500mL.
2. Inspiratory reserve volume — Air that can be drawn in forcibly over and above the tidal air is known as inspiratory reserve volume. It is referred to as IRV or complemental air and is 3000mL.
3. Expiratory reserve volume — It is the air that can be expelled out forcibly after a normal expiration. It is referred to as ERV or supplemental air and is 1000mL.
4. Vital capacity (VC) — It is the volume of air that can be inhaled and exhaled by maximum inspiration and expiration respectively and is about 4500mL.
5. Residual volume (RV) — Even after forcible expiration, there is some air left in the lungs and is referred to as residual volume. It is about 1500mL.

(a) The given figure shows respiratory system and lungs.

(b) Labelled guidelines 1 to 6 are :

• 1 → Trachea
• 2 → Left lung
• 3 → Bronchus
• 4 → Rib cage
• 5 → Pleural fluid
• 6 → Diaphragm

(c) Two advantages of C-shaped cartilaginous rings of trachea are:

• Provide strength to trachea.
• Provide flexibility and keep the trachea distended permanently.

(d) Pleural fluid

(e) Alveoli

(a) Breathing.

(b) Inspiration and expiration.

(c) The parts represent:

1. Lungs
2. Diaphragm
3. Chest cavity

(d) In the chest cavity, enclosed within the rib cage.