Respiratory System and Gas Exchange

Ventilation in respiratory systems

Ventilation is the process of bringing oxygenated water or air into contact with a gas-exchange organ.

Exchange of oxygen and carbon dioxide

To maintain cellular respiration and remove waste gases.

Gas exchange in Cnidarians and Platyhelminthes

By diffusion directly across the body surface due to being only a few cell layers thick.

Cutaneous respiration

Gas exchange through moist, thin, permeable skin, as seen in amphibians.

Gills

Feathery structures that extract oxygen from water or air.

Types of gills

External gills and internal gills.

Limitation of external gills

They are easily damaged and require energy to move for gas exchange.

Protection of internal gills in fish

The operculum.

Countercurrent exchange in fish gills

Oxygen diffuses from water into capillaries along a pressure gradient.

Flow-through ventilation

Water moves one way over gills, keeping them in contact with oxygen-rich water.

Gas exchange in insects

Through spiracles leading to tracheae and finer tracheoles delivering oxygen to each cell.

Function of vertebrate lungs

By negative pressure filling—air moves into lungs due to lower pressure inside than outside.

Boyle's Law

Gas pressure and volume are inversely related.

Major structures of the vertebrate respiratory system

Nose, nasal cavity, pharynx, larynx, trachea, bronchi (and branches), lungs (with alveoli), paranasal sinuses.

Functions of the nose

Provides an airway, moistens/warms air, filters air, assists speech, and houses olfactory receptors.

Nasal septum composition

Vomer bone, perpendicular plate of ethmoid, and cartilage.

Tissues lining the nasal cavity

Olfactory mucosa (with smell receptors) and respiratory mucosa (with ciliated pseudostratified columnar epithelium and goblet cells).

Regions of the pharynx

Nasopharynx, oropharynx, laryngopharynx.

Structures in the nasopharynx

Uvula, pharyngeal tonsil (adenoid), auditory tubes.

Tonsils in the oropharynx

Palatine tonsils and lingual tonsil.

Functions of the larynx

Open airway, routes food/air, and voice production.

Adam's Apple

The thyroid cartilage.

Function of the epiglottis

Prevents food from entering the larynx during swallowing.

Function of true vocal cords

Produce sound by vibrating as air passes through.

Function of false vocal cords

Help close the glottis during swallowing.

Lining of the trachea

Ciliated respiratory mucosa with goblet cells.

Support of the trachea

16-20 C-shaped hyaline cartilage rings.

bronchial tree

Branched airways from trachea to alveoli.

right primary bronchus

It is wider, shorter, and more vertical.

terminal bronchioles

Smallest bronchioles leading to alveolar ducts.

surfactant

A chemical that reduces surface tension in alveoli.

alveoli

Covered externally by pulmonary capillaries for gas exchange.

mediastinum

What separates the right and left lungs.

lung apex

The pointed top just below the clavicle.

hilum

Entry point for pulmonary vessels and bronchi.

layers of pleura

Parietal (thoracic wall) and visceral (lung surface).

pleural cavity

Contains pleural fluid to reduce friction.

two phases of breathing

Inspiration and expiration.

atmospheric pressure (Patm)

760 mm Hg at sea level.

intrapulmonary pressure (Ppul)

Pressure inside alveoli; equalizes with Patm.

intrapleural pressure (Pip)

Pressure in pleural cavity; always ~4 mm Hg less than Ppul.

muscles aiding quiet inspiration

Diaphragm and external intercostals.

passive expiration

Caused by relaxation of muscles and lung elasticity.

external respiration

Gas exchange between alveoli and blood.

internal respiration

Gas exchange between blood and tissue cells.

oxygen transport in blood

Mostly bound to hemoglobin; small amount dissolved in plasma.

oxyhemoglobin (HbO2)

Oxygen bound to hemoglobin.

CO2 transport in blood

10% dissolved in plasma, 20% bound to hemoglobin, 70% as bicarbonate.

enzyme converting CO2 to bicarbonate

Carbonic anhydrase.

regulation of respiration in the brain

Medulla oblongata and pons.

inspiratory center

Sends signals to contract diaphragm and intercostals.

pneumotaxic center

Regulates breathing rhythm by inhibiting the medulla.

pulmonary irritant reflexes

Accumulation of debris leads to coughing and sneezing.

inflation reflex

Lung stretch receptors send signals to inhibit inspiration.

hyperventilation

Rapid breathing due to high CO2 levels in the blood.

atelectasis

A collapsed lung.

COPD

Chronic Obstructive Pulmonary Disease—long-term airflow obstruction.

bronchitis

Inflammation of bronchi, excess mucus production.

emphysema

Alveolar destruction from long-term chemical exposure.

asthma

Narrowed airways leading to wheezing and labored breathing.

common cold

Infection by the Rhino Virus.

rhinitis, laryngitis, and sinusitis

Inflammation of the mucosa in the nose, larynx, and sinuses.

influenza

A viral infection of the respiratory system.

pneumonia

Inflammation of alveoli with fluid and pathogen buildup.