Respiration is the oxidation of nutrients in the living cells to coelenterates, flatworms etc).
release energy for biological work. • Skin or moist cuticle (cutaneous respiration): E.g.
Breathing is the exchange of O2 from the atmosphere with earthworms, leech, amphibians etc.
CO2 produced by the cells. • Tracheal tubes: E.g. insects, centipede, millipede, spider.
RESPIRATORY ORGANS • Gills (Branchial respiration): E.g. fishes, tadpoles, prawn.
• General body surface: E.g. lower invertebrates (sponges, • Lungs (Pulmonary respiration): E.g. most vertebrates.
HUMAN RESPIRATORY SYSTEM
It consists of a pair of air passages (air tract) and lungs. - A cartilaginous Larynx (sound box or voice box) helps in
sound production.
- During swallowing, epiglottis (a thin elastic cartilaginous
flap) closes glottis to prevent entry of food into larynx.
- Trachea, all bronchi and initial bronchioles are supported
by incomplete cartilaginous half rings.
2. Lungs
- Lungs situate in thoracic chamber and rest on diaphragm.
- Right lung has 3 lobes and left lung has 2 lobes.
- Lungs are covered by double-layered pleura (outer
parietal pleura and inner visceral pleura).
- The pleural fluid present in between these 2 layers
lubricates the surface of the lungs and prevents friction
1. Air passages between the membranes.
- Lungs= Bronchi + bronchioles + alveoli.
- Conducting part which transports the atmospheric air into
- Alveoli and their ducts form the respiratory or exchange
the alveoli, clears it from foreign particles, humidifies and
brings the air to body temperature. part of the respiratory system.
External nostrils → nasal passage → nasal chamber - Alveoli are the structural and functional units of lungs.
(cavity) → pharynx → glottis → larynx → trachea → Steps of respiration
primary bronchi → secondary bronchi → tertiary bronchi 1. Pulmonary ventilation (breathing).
→ bronchioles → terminal bronchioles → respiratory 2. Gas exchange between lung alveoli & blood.
bronchiole → alveolar duct. 3. Gas transport (O2 transport & CO2 transport).
- Each terminal bronchiole gives rise to many very thin and 4. Gas exchange between blood & tissues.
vascularised alveoli (in lungs). 5. Cellular or tissue respiration.
MECHANISM OF BREATHING (INSPIRATION & EXPIRATION)
a. Inspiration b. Expiration
- Active intake of air from atmosphere into lungs. - Passive expelling of air from the lungs.
- During this, the diaphragm contracts (flattens) causing an - During this, intercostal muscles & diaphragm relax
increase in vertical thoracic volume (antero-posterior axis). causing a decrease in thoracic volume and thereby
- Contraction of external intercostal muscles (muscles pulmonary volume. So, air moves out.
found between ribs) lifts up the ribs and sternum causing - During forceful expiration, abdominal muscles and
an increase in thoracic volume in the dorso-ventral axis. internal inter-costal muscles contract.
- Increase in thoracic volume reduces thoracic pressure. So, Respiratory volumes and capacities
lungs expand. Thus, pulmonary volume increases resulting • Tidal volume (TV): Volume of air inspired or expired
in decrease of intra-pulmonary pressure to less than the during a normal respiration. It is about 500 ml. i.e., 6000-
atmospheric pressure. So, air moves into lungs. 8000 ml per minute.
• Inspiratory reserve volume (IRV) or complemental air:
Additional volume of air that can inspire by forceful
inspiration. It is 2500-3000 ml.
• Expiratory reserve volume (ERV) or supplemental air:
Additional volume of air that can expire by a forceful
expiration. It is 1000-1100 ml.
• Residual volume (RV): Volume of air remaining in lungs
after a forcible expiration. It is 1100-1200 ml.
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release energy for biological work. • Skin or moist cuticle (cutaneous respiration): E.g.
Breathing is the exchange of O2 from the atmosphere with earthworms, leech, amphibians etc.
CO2 produced by the cells. • Tracheal tubes: E.g. insects, centipede, millipede, spider.
RESPIRATORY ORGANS • Gills (Branchial respiration): E.g. fishes, tadpoles, prawn.
• General body surface: E.g. lower invertebrates (sponges, • Lungs (Pulmonary respiration): E.g. most vertebrates.
HUMAN RESPIRATORY SYSTEM
It consists of a pair of air passages (air tract) and lungs. - A cartilaginous Larynx (sound box or voice box) helps in
sound production.
- During swallowing, epiglottis (a thin elastic cartilaginous
flap) closes glottis to prevent entry of food into larynx.
- Trachea, all bronchi and initial bronchioles are supported
by incomplete cartilaginous half rings.
2. Lungs
- Lungs situate in thoracic chamber and rest on diaphragm.
- Right lung has 3 lobes and left lung has 2 lobes.
- Lungs are covered by double-layered pleura (outer
parietal pleura and inner visceral pleura).
- The pleural fluid present in between these 2 layers
lubricates the surface of the lungs and prevents friction
1. Air passages between the membranes.
- Lungs= Bronchi + bronchioles + alveoli.
- Conducting part which transports the atmospheric air into
- Alveoli and their ducts form the respiratory or exchange
the alveoli, clears it from foreign particles, humidifies and
brings the air to body temperature. part of the respiratory system.
External nostrils → nasal passage → nasal chamber - Alveoli are the structural and functional units of lungs.
(cavity) → pharynx → glottis → larynx → trachea → Steps of respiration
primary bronchi → secondary bronchi → tertiary bronchi 1. Pulmonary ventilation (breathing).
→ bronchioles → terminal bronchioles → respiratory 2. Gas exchange between lung alveoli & blood.
bronchiole → alveolar duct. 3. Gas transport (O2 transport & CO2 transport).
- Each terminal bronchiole gives rise to many very thin and 4. Gas exchange between blood & tissues.
vascularised alveoli (in lungs). 5. Cellular or tissue respiration.
MECHANISM OF BREATHING (INSPIRATION & EXPIRATION)
a. Inspiration b. Expiration
- Active intake of air from atmosphere into lungs. - Passive expelling of air from the lungs.
- During this, the diaphragm contracts (flattens) causing an - During this, intercostal muscles & diaphragm relax
increase in vertical thoracic volume (antero-posterior axis). causing a decrease in thoracic volume and thereby
- Contraction of external intercostal muscles (muscles pulmonary volume. So, air moves out.
found between ribs) lifts up the ribs and sternum causing - During forceful expiration, abdominal muscles and
an increase in thoracic volume in the dorso-ventral axis. internal inter-costal muscles contract.
- Increase in thoracic volume reduces thoracic pressure. So, Respiratory volumes and capacities
lungs expand. Thus, pulmonary volume increases resulting • Tidal volume (TV): Volume of air inspired or expired
in decrease of intra-pulmonary pressure to less than the during a normal respiration. It is about 500 ml. i.e., 6000-
atmospheric pressure. So, air moves into lungs. 8000 ml per minute.
• Inspiratory reserve volume (IRV) or complemental air:
Additional volume of air that can inspire by forceful
inspiration. It is 2500-3000 ml.
• Expiratory reserve volume (ERV) or supplemental air:
Additional volume of air that can expire by a forceful
expiration. It is 1000-1100 ml.
• Residual volume (RV): Volume of air remaining in lungs
after a forcible expiration. It is 1100-1200 ml.
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