Chapter # 10 [Gaseous Exchange]

GASEOUS EXCHANGE

GASEOUS EXCHANGE IN PLANTS

 

Define Photosynthesis. Also write balanced chemical equation.

PHOTOSYNTHESIS

It is the process by which plant prepare their own food by the help of chlorophyll and in the presence of sunlight.

OR

Photosynthesis is a process in which plant absorb CO₂ from the atmosphere and convert it with the absorbed water into glucose in the presence of sunlight.

6CO₂ + 6H₂O                      ⟶       C₆H₁₂O₆ + 6O₂

 

Distinguish between respiration and photosynthesis.

 

Respiration	Photosynthesis
It is catabolic process.	It is anabolic process
It involved in the breakdown of food into inorganic substances.	It involves in the synthesis of food from simple inorganic substances.
Light energy is not required.	Light energy is required.
Oxygen gas is involved.	Carbon dioxide gas is involved.
Chlorophyll is not required.	Chlorophyll is required.
Takes place all the time throughout the life.	Takes place in the day time only.

 

Write note on stomata.

STOMATA

Stomata are the microscopic openings located at the epidermis of leaves. These openings are actually the site of gaseous exchange in plants.

Each stoma is formed by two guard cells. Guard cells are chlorophyllus cells that have thick inner and thin outer cell wall. In fact, the opening and closing of stomata depends upon the turgidity of these guard cells.

During daytime, due to the accumulation of photosynthetic solute, the turgidity of guard cell increase. Thus, stomata are opened and the process of taking in carbon dioxide and giving out of oxygen gas begins until it becomes dark.

 

GASEOUS EXCHANGE IN ANIMALS

In humans and other higher animals the exchange of gases is carried out by the respiratory system. We can divide the respiratory system in two parts i.e. the air passageway and the lungs.

 

Explain Human Respiratory System.

HUMAN RESPIRATORY SYSTEM

The passage of air consists of the following parts;

·        The nose encloses the nasal cavity. It opens to the outside through the openings called external nostrils. The nasal cavity is divided into two portions by a wall. Each portion is lined by fine hairs and mucous which filter the dust particles from the air. The mucous also moistens and warms the incoming air and keeps its temperature nearly equal to that of the body.

·        The nasal cavity opens into the pharynx by means of two small openings called internal nostrils.

·        Pharynx is a muscular passage and is common to both food and air. The air goes from the pharynx into the larynx.

·        The larynx is a box, made of cartilage which is present between pharynx and trachea. Larynx continues to the trachea, which is also called the windpipe.

·        Windpipe It is about 12 cm long tubes that lies in front of the esophagus. There are C-shaped cartilaginous rings in the wall of trachea which prevents the collapsing. On entering the chest cavity, the trachea divides into two tubes called bronchi.

·        The bronchi also have cartilaginous plates in their walls. Each bronchus enters into the lung of its side and then divides into smaller branches and fine tubes called bronchioles.

·        The bronchioles progressively lose the cartilages as they become narrower. The bronchioles end as fine tubules called the alveolar ducts. Each alveolar duct opens into alveoli.

·        The alveoli form the respiratory surface in human body. Each alveolus is lined by single layer of epithelial cells.

·        The pulmonary artery from the heart containing deoxygenated blood enters the lungs and branches into arterioles and then into capillaries which surround the alveoli. These then join together to form the venules which form pulmonary vein. The pulmonary vein carries the oxygenated blood back to the heart.

 

Write a short note on Lungs.

LUNGS

Lungs are the respiratory organs. Each lung is soft, spongy and pinkish in appearance, surrounded by Pleural membrane. The space between pleural membranes is surrounded by fluid that behaves like a lubricant. The left lung is slightly smaller and has two lobes and the right lung is bigger with three lobes. They are spongy and elastic organs. The lungs also have blood vessels that are the branches of the pulmonary arteries and veins.

Lungs are guarded by a cage formed by flat sternum bone, 12 pairs of ribs from front to back, attached with intercoastal muscles. Diaphragm is the separation layer of muscles between lungs and abdominal cavity.

Each lung is made up of alveoli which are the microscopic structures that are made up of only one layer of cells. Alveoli are responsible for gaseous exchange.

 

How does the sound produce?

The larynx is also called the voice box. Two pairs of fibrous bands called vocal cords are stretched across the larynx. When the air passes through them, the vocal cords vibrate and produce sounds.

 

Describe the mechanism of breathing in man.

The mechanism of breathing consists of two phases which are inspiration and expiration.

 

INSPIRATION

The inhalation of gases is called inspiration.

During inspiration, the rib muscles contract and ribs are raised. At the same time, diaphragm contracts and is lowered. These movements increase the area of the thoracic cavity, which reduces the pressure on lungs so the lungs expand and the air pressure decreases. As a result, the air from outside rushes into the lungs to equalize the pressure on both sides.

 

 

EXPIRATION

The excretion of impure air from lungs is called Expiration OR Exhalation.

 

The rib muscles relax bringing the ribs back to the original position. The diaphragm muscles also relax and it gets its shape. This reduces the space in the chest cavity and increases the pressure on lungs. The lungs contract and the air is expelled out of them.

 

How the gaseous exchange does occur in Alveoli?

GASEOUS EXCHANGE IN ALVEOLI

In alveoli, oxygen brought in the air is taken up by the Hemoglobin of RBCs of blood and the carbon dioxide is given out to the air present in alveoli. This involves diffusion.

 

Draw a chart to show the composition of inspired and expired air.

 

Components	Inspired air %	Expired Air %
Oxygen	21	16
Carbon dioxide	0.03	4
Nitrogen	79	79
Water vapours	Variable	Saturated
Temperature	Atmospheric temperature	37OC

 

Define anaerobic respiration.

ANAEROBIC RESPIRATION

It is the type of respiration that occurs in the absence of oxygen. During anaerobic respiration, the muscle cell breaks glucose into lactic acid in the absence of oxygen. Usually, in animals, it occurs when there’s scarcity of oxygen or if a person is doing exercise.

 

What do you know about artificial ventilator?

ARTIFICIAL VENTILATOR

Artificial ventilator is a machine that works like lungs when patient’s breathing becomes difficult.  Through this machine, the oxygen rich air is directly supplied to the trachea through a tube inserted in the mouth up to wind pipe.

 

Discuss the following respiratory disorders.

·       Bronchitis

·       Emphysema

·       Pneumonia

·       Asthma

·       Lung cancer

 

BRONCHITIS
The inflammation of the bronchi or bronchioles is called Bronchitis.

 

CAUSES

·        Excessive mucus secretions,

·        Swelling of tubular walls and narrowing of tubes,

·        Viral or bacterial or exposure to chemical irritants

 

TYPES

There are two major types of bronchitis i.e. acute and chronic.

 

The acute bronchitis usually lasts about two weeks and patients recover with no permanent damage to the bronchi or bronchioles.

In chronic bronchitis, the bronchi develop chronic inflammation. It usually lasts for three months to two years.

 

SIGNS AND SYMPTOMS

·        Cough,

·        Mild wheezing,

·        Fever,

·        Chills and

·        Shortness of breath

 

EMPHYSEMA

Emphysema is the destruction of the walls of the alveoli.

 

 

CAUSES

·        Exposure to pollutants

 

SIGN AND SYMPTOMS

·        Shortness of breath,

·        Fatigue,

·        Recurrent respiratory infections and weight loss.

 

EFFECT

·        Cough

·        Cough with phlegm production

 

PNEUMONIA

Pneumonia is an infection of lungs. If this infection affects both lungs then, it is called double pneumonia.

 

CAUSES

·        Bacteria Streptococcus pneumoniae

·        Some viral (influenza virus) and fungal infections may also lead to pneumonia.

 

SIGN AND SYMPTOMS

·        Cold followed by a high fever,

·        Shivering,

·        Cough with sputum

 

ASTHMA

Asthma is a form of allergy which is characterized as inflammation of the bronchi with more mucous production and narrowing of the airways.

 

CAUSES

·        Allergens (allergy causing factors)

o   Dust

o   Smoke

o   Perfumes

o   Pollens

 

SIGN AND SYMPTOMS

·        Shortness of breath

·        Wheezing (whistling sound when breathing out),

·        Cough and chest tightness.

 

LUNG CANCER

The abnormal and uncontrolled cell divisions in the tissues of the lung are called lung cancer.

The cells continue to divide without any control and form tumors.

 

CAUSES

·        Carcinogens (such as those in cigarette smoke),

·        Ionizing radiation

·        Viral infection.

·        Smoking

 

SIGN AND SYMPTOMS

·        Shortness of breath,

·        Coughing (including coughing up blood) and

·        Weight loss.