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GASEOUS EXCHANGE
1: Definition: Taking in of oxygen and giving out of carbon dioxide is called as
gaseous exchange.
Thera are two types of gaseous exchange are called as:
1: Gaseous Exchange in Plants
2: Gaseous exchange in humans
EXPLANATION:
1: Gaseous Exchange in Plants: Plants have no organ system for the exchange of
gases with the environment. Every cell of the plant body exchange gases with
environment by its own.
i: Gaseous Exchange in leaf: The leaf and the young stems have stomata in their
epidermis. The gaseous exchange occurs through these stomata. The inner cells of
leaves (mesophyll) and stems also have air spaces among them, which help in
exchange of gases.
i: Process During Day time: when mesophyll cells of leaves are
carrying out photosynthesis and respiration occurs side by side , the
oxygen produced in photosynthesis is utilized in cellular respiration.
Similarly the carbon dioxide produced during cellular respiration is
utilized in photosynthesis.
ii: Process during Night time: When there is no photosynthesis
occurring, the leaf cells get oxygen from the environment and release
carbon dioxide through stomata.
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2: Gaseous Exchange in Humans: The air passageway consists of the
parts through which the outside air comes in the lungs and after the
exchange of gases it goes out. This passage of air consists of the
following parts.
The nose encloses the nasal cavity. It opens to the outside through the
openings called the 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 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. It extends to the opening of the esophagus and the
larynx. The air goes from the pharynx into the larynx. We know that
glottis is a narrow opening at the floor of pharynx which leads into
larynx. The larynx is a box, made of cartilage. It is present between
pharynx and trachea. It is also called the voice box. Two pairs of fibrous
bands called vocal cords are stretched across the larynx. The vocal cords
vibrate when the air passes through them. This vibration produces sounds.
Larynx continues to the trachea, which is also called the windpipe. It is
about 12 cm long tube which lies in front of the esophagus. There are C-
shaped cartilaginous rings in the wall of trachea. The cartilages keep the
trachea from collapsing even when there is no air in it.
On entering the chest cavity, the trachea divides into two smaller tubes
called bronchi (Singular: bronchus). The bronchi also have cartilaginous
plates in their walls. Each bronchus enters into the lung of its side and
then divides into smaller branches. The bronchi continue dividing in the
lungs until they make several 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 a cluster of pouches called alveoli. The alveoli
form the respiratory surface in human body. Each alveolus is a sac-like
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structure lined by a single layer of epithelial cells. It is bound on the
outside by a network of capillaries (Fig: 10.3). 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 oxygenated blood back to
the heart.
2: The lungs: All the alveoli on one side constitute a lung. There is a pair
of lungs in the thoracic cavity. The chest wall is made up of 12 pairs of
ribs and the rib muscles called intercoastal muscles. A thick muscular
structure, called diaphragm, is present below the lungs. 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. Each
lung is enclosed by two membranes called the outer pleural membrane
and the inner pleural membrane. The membranes enclose a fluid which
provides lubrication for the free expanding and contracting of the
lungs.

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GASEOUS EXCHANGE 1: Definition: Taking in of oxygen and giving out of carbon dioxide is called as gaseous exchange. Thera are two types of gaseous exchange are called as: 1: Gaseous Exchange in Plants 2: Gaseous exchange in humans EXPLANATION: 1: Gaseous Exchange in Plants: Plants have no organ system for the exchange of gases with the environment. Every cell of the plant body exchange gases with environment by its own. i: Gaseous Exchange in leaf: The leaf and the young stems have stomata in their epidermis. The gaseous exchange occurs through these stomata. The inner cells of leaves (mesophyll) and stems also have air spaces among them, which help in exchange of gases. i: Process During Day time: when mesophyll cells of leaves are carrying out photosynthesis and respiration occurs side by side , the oxygen produced in photosynthesis is utilized in cellular respiration. Similarly the carbon dioxide produced during cellular respiration is utilized in photosynthesis. ii: Process during Night time: When there is no photosynthesis occurring, the leaf cells get oxygen from the environment and release carbon dioxide through stomata. 2: Gaseous Exchange in Humans: The air passageway consists of the parts through which the outside air comes in the lungs and after the exchange of gases it goes out. This passage of air consists of the following parts. The nose encloses the nasal cavity. It opens to the outside through the openings called the 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 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. It extends to the opening of the esophagus and the larynx. The air goes from the pharynx into the larynx. We know that glottis is a narrow opening at the floor of pharynx which leads into larynx. The larynx is a box, made of cartilage. It is present between pharynx and trachea. It is also called the voice box. Two pairs of fibrous bands called vocal cords are stretched across the larynx. The vocal cords vibrate when the air passes through them. This vibration produces sounds. Larynx continues to the trachea, which is also called the windpipe. It is about 12 cm long tube which lies in front of the esophagus. There are Cshaped cartilaginous rings in the wall of trachea. The cartilages keep the trachea from collapsing even when there is no air in it. On entering the chest cavity, the trachea divides into two smaller tubes called bronchi (Singular: bronchus). The bronchi also have cartilaginous plates in their walls. Each bronchus enters into the lung of its side and then divides into smaller branches. The bronchi continue dividing in the lungs until they make several 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 a cluster of pouches called alveoli. The alveoli form the respiratory surface in human body. Each alveolus is a sac-like structure lined by a single layer of epithelial cells. It is bound on the outside by a network of capillaries (Fig: 10.3). 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 oxygenated blood back to the heart. 2: The lungs: All the alveoli on one side constitute a lung. There is a pair of lungs in the thoracic cavity. The chest wall is made up of 12 pairs of ribs and the rib muscles called intercoastal muscles. A thick muscular structure, called diaphragm, is present below the lungs. 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. Each lung is enclosed by two membranes called the outer pleural membrane and the inner pleural membrane. The membranes enclose a fluid which provides lubrication for the free expanding and contracting of the lungs. Name: Description: ...
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