Breathing and Exchange of Gases -1 Flashcards
what is breathing?
This process of exchange of O2
from
the atmosphere with CO2
produced by the cells is called breathing.commonly known as respiration
how do lower invertebreates breathe?
Mechanisms of breathing vary among different groups of animals
depending mainly on their habitats and levels of organisation. Lower
invertebrates like sponges, coelenterates, flatworms, etc., exchange O2
with CO2
by simple diffusion over their entire body surface.
how do other invertbereates breathe
Earthworms
use their moist cuticle(on skin for diffusion through skin surface) and insects have a network of tubes (tracheal
tubes) to transport atmospheric air within the body.They respire through book gills,booklungs and spiracles.
Special vascularised
structures called gills are used by most of the aquatic arthropods and
molluscs (feather liek gills)whereas vascularised bags called lungs are used by the
terrestrial forms for the exchange of gases.
how do vertebreates breathe
Among vertebrates, fishes
use gills whereas reptiles, birds and mammals respire through lungs.
Amphibians like frogs can respire through their moist skin also.(gills in larval stage)
Mammals have a well developed respiratory system.
explain human respiratory system till larynx
We have a pair of external nostrils opening out above the upper lips.
It leads to a nasal chamber through the nasal passage. The nasal
chamber opens into the pharynx, a portion of which is the common
passage for food and air. The pharynx opens through the larynx region
into the trachea. Larynx is a cartilaginous box which helps in sound
production and hence called the sound box.
what is the functionof epiglottis
During swallowing glottis
can be covered by a thin elastic cartilaginous flap called epiglottis to
prevent the entry of food into the larynx.
explain human respiratory systemfrom trachea ot alveoli
Trachea is a straight tube
extending up to the mid-thoracic cavity, which divides at the level of
5th thoracic vertebra into a right and left primary bronchi. Each bronchi
undergoes repeated divisions to form the secondary and tertiary bronchi
and bronchioles ending up in very thin terminal bronchioles. The
tracheae, primary, secondary and tertiary bronchi, and initial
bronchioles are supported by incomplete cartilaginous rings. Each
terminal bronchiole gives rise to a number of very thin, irregular-walled
and vascularised bag-like structures called alveoli.
describe lungs
The branching
network of bronchi, bronchioles and alveoli comprise the lungs (Figure
17.1). We have two lungs which are covered by a double layered membrane called pleura,
with pleural fluid between them. It reduces friction on the lung-surface.
The outer pleural membrane is in close contact with the thoracic lining whereas the inner pleural membrane is in contact with the lung
surface.These collectively reduce friction on lung’s surface. it also acts as a shock absorber
what is the conducting part and echanging part of repiratory system
The part starting with the external nostrils up to the terminal
bronchioles constitute the conducting part whereas the alveoli and their
ducts form the respiratory or exchange part of the respiratory system.
The conducting part transports the atmospheric air to the alveoli, clears
it from foreign particles, humidifies and also brings the air to body
temperature. Exchange part is the site of actual diffusion of O2
and CO2
between blood and atmospheric air.
where are the lungs placed?
The lungs are situated in the thoracic chamber which is anatomically
an air-tight chamber. The thoracic chamber is formed dorsally by the
vertebral column, ventrally by the sternum, laterally by the ribs and on
the lower side by the dome-shaped diaphragm. The anatomical setup of
lungs in thorax is such that any change in the volume of the thoracic
cavity will be reflected in the lung (pulmonary) cavity. Such an
arrangement is essential for breathing, as we cannot directly alter the
pulmonary volume.
list the steps of respiratio
(i) Breathing or pulmonary ventilation by which atmospheric air
is drawn in and CO2
rich alveolar air is released out.
(ii) Diffusion of gases (O2
and CO2) across alveolar membrane.
(iii) Transport of gases by the blood.
(iv) Diffusion of O2
and CO2
between blood and tissues.
(v) Utilisation of O2
by the cells for catabolic reactions and resultant
release of CO2
explain the two processes of breathing
Breathing involves two stages : inspiration during which atmospheric
air is drawn in and expiration by which the alveolar air is released out.
The movement of air into and out of the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere.
Inspiration can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. Similarly, expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure.
which muscles help in breathing
The diaphragm and a specialised set of muscles – external and
internal intercostals between the ribs, help in generation of such gradients.
explain inspiration
Inspiration is initiated by the contraction of diaphragm which increases
the volume of thoracic chamber in the antero-posterior axis. The
contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of
the thoracic chamber in the dorso-ventral axis.
The overall increase in the thoracic volume
causes a similar increase in pulmonary
volume. An increase in pulmonary volume
decreases the intra-pulmonary pressure to less
than the atmospheric pressure which forces
the air from outside to move into the lungs,
i.e., inspiration
explain expiration
Relaxation of
the diaphragm and the inter-costal muscles
returns the diaphragm and sternum to their
normal positions and reduce the thoracic
volume and thereby the pulmonary volume.
This leads to an increase in intra-pulmonary
pressure to slightly above the atmospheric
pressure causing the expulsion of air from the
lungs, i.e., expiration (Figure 17.2b).
