Respiratory System Physiology Review

Four processes of rspirations

pulmonary ventilation,rxternal respiration,transport, internal respiration

pulmonary ventilation

gas exchange between lungs and blood

External respiration

Gas exchange between the alveoli of the lungs and the blood; O₂ enters blood, CO₂ leaves.

Transport (of respiratory gases)

Movement of O₂ and CO₂ through the bloodstream between lungs and tissues.

Internal respiration

Gas exchange between systemic blood and body tissues; O₂ leaves blood, CO₂ enters.

Conducting zone

All respiratory passageways from the nostrils through the terminal bronchioles that conduct, warm, filter, and humidify air.

Respiratory zone

Regions where gas exchange occurs: respiratory bronchioles, alveolar ducts, and alveoli.

Surfactant

Detergent-like secretion of type II alveolar cells that lowers alveolar surface tension to prevent collapse.

Nose / Nasal cavity

Structures that filter, warm, and moisten incoming air and house olfactory receptors and resonance chambers for speech.

Pharynx

Muscular passageway (naso-, oro-, laryngopharynx) serving as a route for both air and food.

Larynx

Cartilaginous organ that routes food and air, provides an open airway, and produces voice.

Structures of upper respiratory system

nose,pharynx,larynx

Pressure relationships in thoracic cavity

atmospheric pressure,intrapulmonary pressure, intrapleural pressure, transpulmoanry pressure

Atmospheric pressure (Patm)

Pressure exerted by air surrounding the body, approximately 760 mm Hg at sea level.

Intrapulmonary pressure (Ppul)

Pressure within the alveoli; fluctuates with breathing but equalizes with Patm between breaths.

Intrapleural pressure (Pip)

Pressure within the pleural cavity; always negative relative to Ppul to keep lungs expanded.

Transpulmonary pressure

Difference between Ppul and Pip; the pressure that keeps the lungs from collapsing.

Inspiration

Active phase of breathing in which the diaphragm and external intercostals contract, increasing thoracic volume and drawing air into the lungs.

Expiration

Passive (quiet) phase of breathing out when inspiratory muscles relax, thoracic volume decreases, and air flows out; forced expiration uses abdominal and internal intercostal muscles.

Factors affecting pulmonary ventilation

airway resistance,alveolar surface,lung complaince

Airway resistance

Opposition to airflow within respiratory passages; rises with bronchoconstriction (e.g., asthma).

Alveolar surface tension

Attractive force of liquid molecules in alveoli; reduced by surfactant to prevent collapse.

Lung compliance

Ease with which lungs and thoracic wall expand; decreased by fibrosis, low surfactant, or rigid thoracic cage.

Atelectasis

Lung collapse due to blocked bronchioles or pneumothorax allowing air into pleural cavity.

Asthma

Inflammatory airway disorder characterized by bronchospasm and reversible airflow obstruction.

Chronic obstructive pulmonary disease (COPD)

Progressive, largely irreversible airflow limitation encompassing emphysema and chronic bronchitis.

Emphysema

Type of COPD marked by alveolar wall destruction and enlarged air spaces, reducing gas-exchange surface area.

Chronic bronchitis

Type of COPD involving chronic inflammation and excess mucus production in the bronchi.

Partial pressure gradient

Difference in gas partial pressures that drives diffusion of O₂ and CO₂ during respiration.

external respiration

o2 moves from alveoli to blood co 2 from blood to alveoli

internal respiration

o2 moves from blood to tissues co2 mobes from blood to tissues

Ventilation-perfusion coupling

Automatic matching of airflow (ventilation) with blood flow (perfusion) in the lungs for efficient gas exchange.

transport of oxygen and carbon dioxde in blood

oxygen-Hemoglobin bound to oxygen; accounts for about 98.5 % of transported O₂. affinity influenced by po2,oh,temperaure,pco2,and bpg

transport of oxygen and carbon dioxide and blood-carbon dioxide

Hemoglobin after it releases oxygen to tissues. 7-10% dissolvedof plasma 30% bound to hemoglobin

chemeical stimuli for respiration

co2-primary driver increased co2 lowers ph,stimulates central chemoreceptors,o2-detected by peripheral chemorecoetors an dbecomes major stimulus if po2 less than 60 mg and h+-also affects respiratory rate via chemoreceptors

Bicarbonate ion (HCO₃⁻)

Primary form (≈70 %) in which CO₂ is transported in blood, formed in RBCs via carbonic anhydrase.

2,3-Bisphosphoglycerate (BPG)

RBC metabolite that decreases hemoglobin’s affinity for O₂, enhancing O₂ release to tissues.

Central chemoreceptors

Medulla oblongata receptors sensitive to elevated CO₂ (and reduced pH) in cerebrospinal fluid, driving ventilation.

Peripheral chemoreceptors

Carotid and aortic body receptors that monitor arterial O₂, CO₂, and pH; trigger increased breathing when PaO₂ < 60 mm Hg.

Carbonic anhydrase

Enzyme in RBCs that rapidly converts CO₂ and water to carbonic acid, facilitating bicarbonate formation.

Type II alveolar cells

Alveolar epithelial cells that secrete surfactant and contribute to alveolar fluid homeostasis.

Bronchioles

Small airways arising from tertiary bronchi; include terminal and respiratory bronchioles.

Alveoli

Tiny air sacs forming the main sites of gas exchange in the lungs.