Breathing and Exchange of Gases

Comprehensive Question and Answer practice flashcards covering human respiration, respiratory structures, pulmonary mechanics, volumes and capacities, gaseous exchange, saturation curves, transport of gases, neural/chemical regulation, and respiratory disorders based on the lecture.

What is respiration as defined in human physiology?

Respiration is a physiochemical process in which oxygen ($O_2$) is used to break down nutrients like glucose ($C_6H_{12}O_6$) to produce water ($H_2O$), carbon dioxide ($CO_2$), and energy ($ATP$).

What are the five main steps involved in respiration?

The five steps are: 1) Breathing (inhalation and exhalation), 2) External respiration, 3) Internal respiration, 4) Exchange of gases, and 5) Cellular respiration.

What is external respiration?

External respiration is the exchange of gases ($O_2$ and $CO_2$) between the lungs (alveoli) and the blood vessels.

What is internal respiration?

Internal respiration is the exchange of gases between blood vessels and the body cells/tissues.

How is respiration categorized based on organism habitat?

Respiration performed in water is termed brachial respiration (e.g., via gills), whereas respiration performed on land using lungs is termed pulmonary respiration.

Which lower animal groups perform gas exchange via simple diffusion over their general body surface?

Porifera, Coelenterata, Ctenophora, Platyhelminthes, and Aschelminthes.

By what mechanism do earthworms (Annelida) perform respiration?

Earthworms respire through their moist cuticle.

What specialized respiratory structures are found in Arthropoda?

Arthropods utilize book lungs, book gills, or a tracheal system for respiration.

How do Echinoderms perform respiration?

Echinoderms respire using tube feet connected to their water canal system.

Which vertebrate classes perform pulmonary respiration using lungs?

Reptiles, Aves, Mammals, and adult Amphibians (which can also use skin and buccopharynx).

What is the function of the epiglotis during swallowing?

The epiglotis is a cartilaginous flap that covers the trachea (windpipe) during swallowing to prevent the entry of food into the respiratory tract.

At what anatomical level does the trachea divide into right and left primary bronchi?

The trachea divides into primary bronchi at the level of the $5^{\text{th}}$ thoracic vertebra.

How far along the bronchial tree are cartilaginous rings present?

Incomplete cartilaginous rings are present from the trachea down to the initial bronchioles.

What is the structural and functional unit of the human lungs where gas exchange occurs?

The alveoli (singular: alveolus).

What is the double-layered membrane enclosing the human lungs called?

The pleural membrane, consisting of an outer peripheral/parietal pleura and an inner visceral pleura, containing pleural fluid.

Which human lung features the cardiac notch?

The left lung.

What anatomical structures demarcate the boundaries of the thoracic chamber?

Ventrally by the sternum, dorsally by the vertebral column, laterally by the ribs, and inferiorly by the dome-shaped diaphragm.

What structures constitute the conducting zone of the human respiratory system?

The conducting zone extends from the external nostrils up to the terminal bronchioles.

What structures constitute the respiratory (exchange) zone of the human respiratory system?

The alveolar ducts and the alveoli.

How does the diaphragm move during inhalation?

The diaphragm contracts and moves downwards, becoming flat-shaped to increase thoracic volume.

How do the ribs and sternum move during inhalation?

The external intercostal muscles pull the ribs and sternum upwards and outwards.

What structural changes occur to the diaphragm and ribs during exhalation?

The diaphragm relaxes, moves upwards to resume its dome shape, and the ribs move downwards and inwards.

What is the normal breathing rate of a healthy adult human?

An adult human respires $12$ to $16$ times per minute.

What clinical instrument is used to measure respiratory volumes and capacities?

A spirometer.

What is Tidal Volume ($TV$) and its normal average value?

Tidal Volume is the volume of air inhaled or exhaled during normal respiration, averaging approximately $500\,mL$ per breath ($6000$ to $8000\,mL$ per minute).

What is Inspiratory Reserve Volume ($IRV$) and its normal range?

Inspiratory Reserve Volume is the additional volume of air a person can forcefully inhale after a normal inhalation, ranging from $2500\,mL$ to $3000\,mL$.

What is Expiratory Reserve Volume ($ERV$) and its normal range?

Expiratory Reserve Volume is the additional volume of air a person can forcefully exhale after a normal exhalation, ranging from $1000\,mL$ to $1100\,mL$.

What is Residual Volume ($RV$) and its normal range?

Residual Volume is the volume of air remaining in the lungs even after a forceful exhalation, ranging from $1100\,mL$ to $1200\,mL$.

What is the formula and definition for Inspiratory Capacity ($IC$)?

Inspiratory Capacity is the total volume of air a person can inhale after normal exhalation; $IC = TV + IRV$.

What is the formula and definition for Expiratory Capacity ($EC$)?

Expiratory Capacity is the total volume of air a person can exhale after normal inhalation; $EC = TV + ERV$.

What is the formula and definition for Functional Residual Capacity ($FRC$)?

Functional Residual Capacity is the volume of air remaining in the lungs after normal exhalation; $FRC = ERV + RV$.

What is the formula and definition for Vital Capacity ($VC$)?

Vital Capacity is the maximum volume of air a person can exhale after a forceful inhalation; $VC = TV + IRV + ERV$.

What is the formula and definition for Total Lung Capacity ($TLC$)?

Total Lung Capacity is the total volume of air accommodated in the lungs at the end of a forced inhalation; $TLC = VC + RV$ or $TLC = TV + IRV + ERV + RV$.

What three structural layers form the diffusion membrane of the alveoli?

1) Simple squamous epithelium of the alveolus, 2) Endothelium of alveolar capillaries, and 3) The basement membrane situated between them.

How does the solubility of carbon dioxide ($CO_2$) compare to oxygen ($O_2$) across the respiratory membrane?

Carbon dioxide ($CO_2$) is $20$ to $25$ times more soluble than oxygen ($O_2$).

What are the partial pressures of $O_2$ ($PO_2$) and $CO_2$ ($PCO_2$) in atmospheric air vs alveoli?

In atmospheric air: $PO_2 = 159\,mmHg$ and $PCO_2 = 0.3\,mmHg$. In alveoli: $PO_2 = 104\,mmHg$ and $PCO_2 = 40\,mmHg$.

What are the partial pressures of $O_2$ ($PO_2$) and $CO_2$ ($PCO_2$) in oxygenated blood?

$PO_2 = 95\,mmHg$ and $PCO_2 = 40\,mmHg$.

What are the partial pressures of $O_2$ ($PO_2$) and $CO_2$ ($PCO_2$) in deoxygenated blood and body tissues?

$PO_2 = 40\,mmHg$ and $PCO_2 = 45\,mmHg$.

In what percentages is oxygen ($O_2$) transported in human blood?

About $97\%$ of $O_2$ is transported bound to hemoglobin in red blood cells, while $3\%$ is carried dissolved in blood plasma.

How many oxygen molecules can bind to a single hemoglobin molecule?

One hemoglobin molecule can carry up to $4$ molecules of oxygen ($O_2$).

How much oxygen ($O_2$) is delivered to tissues by every $100\,mL$ of oxygenated blood under normal conditions?

Every $100\,mL$ of oxygenated blood delivers approximately $5\,mL$ of $O_2$ to the tissues.

What shape is the oxygen-hemoglobin dissociation curve?

A sigmoid (S-shaped) curve.

Which factors shift the oxygen-hemoglobin dissociation curve to the right (promoting dissociation)?

Low $PO_2$, high $PCO_2$, high $H^+$ concentration (low pH), and increased temperature.

Which factors shift the oxygen-hemoglobin dissociation curve to the left (promoting association)?

High $PO_2$, low $PCO_2$, low $H^+$ concentration (high pH), and decreased temperature.

By what three modes is carbon dioxide ($CO_2$) transported in the blood?

1) As bicarbonate ions ($70\%$), 2) Bound to hemoglobin as carbamino-hemoglobin ($20\%$ to $25\%$), and 3) Dissolved in plasma ($7\%$).

How much carbon dioxide ($CO_2$) is delivered to the alveoli by every $100\,mL$ of deoxygenated blood?

Every $100\,mL$ of deoxygenated blood delivers approximately $4\,mL$ of $CO_2$ to the alveoli.

Which enzyme inside RBCs facilitates the conversion of $CO_2$ and $H_2O$ into carbonic acid ($H_2CO_3$) and bicarbonate ions?

Carbonic anhydrase.

Where is the primary Respiratory Rhythm Center ($RRC$) located in the brain?

In the medulla (medulla oblongata) region of the brainstem.

What is the location and function of the Pneumotaxic Center?

Located in the pons region of the brainstem; it acts as a switch-off center that reduces the duration of inhalation to alter the breathing rate.

Where are chemoreceptors located and what chemical alterations do they sense?

Central chemoreceptors are in the medulla, while peripheral chemoreceptors are in the aortic arch (aortic bodies) and carotid arteries (carotid bodies); they detect increases in $CO_2$ and $H^+$ concentrations.

What characterizes Asthma as a respiratory disorder?

Asthma is an allergic disorder causing difficulty in breathing and wheezing due to inflammation of the bronchi and bronchioles.

What is Emphysema, and what primary factor damages the alveolar walls in this condition?

Emphysema is a chronic disorder in which alveolar walls are damaged, reducing the respiratory surface area; it is primarily caused by cigarette smoking.

What causes Occupational Respiratory Disorders like pulmonary fibrosis?

Inhalation of industrial dust (e.g., in stone-grinding, mining, or coal industries) causes chronic inflammation and proliferation of fibrous tissue (fibrosis) in the lungs.