Breathing and Exchange of Gases

Vocabulary flashcards covering human respiratory anatomy, breathing mechanisms, lung volumes, gas transport, regulation, and disorders.

Breathing (Respiration)

The process of exchange of $O_2$ from the atmosphere with $CO_2$ produced by the cells, involving physical, chemical, and biological processes.

Branchial respiration

A form of respiration where aquatic arthropods (prawns/crustaceans) and molluscs use vascularized structures called gills.

Pulmonary respiration

Respiration used by terrestrial forms through vascularised bags called lungs.

Cutaneous respiration

The mode of respiration used by frogs where they can respire through their skin.

Thoracic vertebra (5th)

The point at which the trachea divides into the right and left primary bronchi.

Larynx

A cartilaginous box that helps in sound production and is consequently called the sound box.

Pleural membrane

A double layered wall surrounding the lungs filled with pleural fluid that reduces friction on the lung surface.

Conducting part

The section of the respiratory system from the external nostrils to the terminal bronchioles that hummidifies air, clears foreign particles, and brings air to body temperature.

Respiratory/Exchange part

Comprising the alveoli and their ducts, this is the site of actual diffusion of $O_2$ and $CO_2$ between blood and atmospheric air.

Inspiration

The process where atmospheric air is moved in due to negative pressure in the lungs, involving the contraction of the diaphragm and external intercostal muscles.

Expiration

The process where alveolar air is released out as intrapulmonary pressure becomes higher than atmospheric pressure due to the relaxation of the diaphragm and intercostal muscles.

Spirometer

An instrument used to estimate the volume of air involved in breathing movements, helping in clinical assessment of pulmonary functions.

Tidal Volume (TV)

The volume of air inspired or expired during a normal respiration, being approximately $500\,ml$ ($6000$ to $8000\,ml$ per minute).

Inspiratory Reserve Volume (IRV)

The additional volume of air a person can inspire by a forcible inspiration, averaging $2500\,ml$ to $3000\,ml$.

Expiratory Reserve Volume (ERV)

The additional volume of air a person can expire forcefully, averaging $1000\,ml$ to $1100\,ml$.

Residual Volume (RV)

The volume of air remaining in the lungs even after forceful expiration, averaging $1100\,ml$ to $1200\,ml$.

Inspiratory Capacity (IC)

The total volume of air a person can inspire after a normal expiration, calculated as $TV+IRV$.

Expiratory Capacity (EC)

Defined in the text as the total volume of air a person can inspire after a normal expiration, calculated as $TV+IRV$.

Functional Residual Capacity (FRC)

The volume of air that remains in the lungs after a normal expiration, calculated as $ERV+RV$.

Vital Capacity (VC)

The maximum volume of air a person can breathe in or out after a forced expiration or inhalation, calculated as $ERV+TV+IRV$.

Total Lung Capacity (TLC)

The total volume of air accommodated in the lungs at the end of a forced inspiration, calculated as $RV+TV+ERV+IRV$ or $VC+RV$.

Partial pressure

The pressure contributed by an individual gas in a mixture of gases, denoted as $pO_2$ and $pCO_2$.

Diffusion membrane

A barrier less than $1\,mm$ thick made of three layers: thin squamous epithelium of alveoli, endothelium of alveolar capillaries, and basement substance.

Oxyhaemoglobin

A reversible complex formed when oxygen binds with hemoglobin (Hb); each Hb molecule can carry four $O_2$ molecules.

Oxygen dissociation curve

A graph plotting the percentage saturation of hemoglobin with $O_2$ against $pO_2$, which is sigmoid in shape.

Carbamino haemoglobin

The form of $CO_2$ (about $20-25\%$) carried by hemoglobin, favored by high $pCO_2$ and low $pO_2$ in tissues.

Carbonic anhydrase

An enzyme in RBCs and plasma that facilitates the reaction: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons HCO_3^- + H^+$.

Respiratory rhythm centre

The primary center responsible for respiratory regulation, located in the medulla region of the brain.

Pneumotaxic centre

A centre in the pons region of the brain that can reduce the duration of inspiration and alter the respiratory rate.

Asthma

A respiratory disorder characterized by wheeziness and difficulty breathing due to inflammation of the bronchi and bronchioles.

Emphysema

A chronic disorder caused by cigarette smoking where alveolar walls are damaged, decreasing the respiratory surface area.

Fibrosis

The proliferation of fibrous tissue leading to serious lung damage, often resulting from long exposure to dust in industries like stone breaking.