Chapter 23: The Respiratory System

Comprehensive vocabulary flashcards covering the structural organization, histology, mechanics of ventilation, gas transport, neurological control, and clinical pathologies of the respiratory system from Chapter 23.

Conducting Zone

The functional division of the respiratory system that transports air from the external nose through the terminal bronchioles without participating in gas exchange (Slide 2).

Respiratory Zone

The microscopic functional division of the respiratory system where pulmonary gas exchange occurs, comprising respiratory bronchioles, alveolar ducts, and alveoli (Slide 2).

Upper Respiratory Tract (URT)

The structural division of the respiratory system consisting of the nose, nasal cavity, paranasal sinuses, pharynx, and larynx (Slide 2, 3).

Lower Respiratory Tract (LRT)

The structural division of the respiratory system consisting of the trachea, bronchi, bronchioles, alveolar ducts, and alveoli (Slide 2, 3).

Structural differences between right and left lungs

The right lung possesses three lobes (superior, middle, and inferior), whereas the left lung possesses two lobes (superior and inferior) and an indentation called the cardiac notch (Slide 4).

Three layers of the respiratory mucosa

An epithelium, an underlying basement membrane, and an areolar connective tissue vascular layer known as the lamina propria (Slide 5).

Epithelial transition along the respiratory tract

The mucosal lining becomes progressively thinner: pseudostratified ciliated columnar $\rightarrow$ simple ciliated columnar $\rightarrow$ simple cuboidal $\rightarrow$ simple squamous (Slide 5).

Nonkeratinized stratified squamous epithelium in the airway

A protective mucosal lining found in friction-prone areas of the pharynx and larynx, structured to resist abrasion from swallowed food (Slide 5).

Goblet Cells

Unicellular exocrine glands distributed throughout the majority of the respiratory tract epithelium that synthesize and secrete mucin (Slide 6).

Mucin

A protein secreted by goblet cells that increases the viscosity and stickiness of mucus to trap inhaled particulates, dust, and pathogens (Slide 6).

Antimicrobial substances in respiratory secretions

Lysozymes (antibacterial enzymes), defensins (antimicrobial proteins), and immunoglobulin A ($\text{IgA}$ antibodies) (Slide 6).

Airway regions lined by pseudostratified ciliated columnar epithelium

The nasal cavity, paranasal sinuses, nasopharynx, inferior larynx, trachea, main (primary) bronchi, and lobar (secondary) bronchi (Slide 7).

Airway regions lined by simple ciliated columnar epithelium

The segmental (tertiary) bronchi, smaller bronchi, and large conducting bronchioles (Slide 7).

Airway regions lined by simple cuboidal epithelium

The terminal bronchioles and respiratory bronchioles (Slide 7).

Airway regions lined by simple squamous epithelium

The alveolar ducts and alveoli, presenting a microscopic diffusion barrier for rapid gas exchange (Slide 7).

Anatomic framework of the external nose

Paired nasal bones forming the bridge, lateral and alar hyaline cartilages forming the anterior framework, and dense irregular connective tissue forming the nares (nostrils) (Slide 9, 10).

Primary functions of the nasal cavity

Conditioning incoming air by warming, cleansing (filtering), and humidifying it before passage into the lower respiratory tract (Slide 9).

Muscular wall of the pharynx

Skeletal muscle that provides distensibility during food ingestion and contracts to force the food bolus into the esophagus (Slide 11).

Nasopharynx

The superior segment of the pharynx positioned directly behind the nasal cavity and superior to the soft palate (Slide 11).

Oropharynx

The middle pharyngeal division extending from the soft palate to the upper margin of the epiglottis, located directly posterior to the oral cavity (Slide 11).

Laryngopharynx

The inferior pharyngeal segment extending from the epiglottis down to the cricoid cartilage, where it merges with the esophagus (Slide 11).

Major functions of the larynx

Conducting air, phonation via true vocal folds, preventing food aspiration through epiglottic closure, and increasing intra-abdominal pressure during the Valsalva maneuver (Slide 12).

Valsalva Maneuver

A technique of forced exhalation against a closed glottis or pinched airway that markedly raises intrathoracic and intra-abdominal pressures during defecation, heavy lifting, and childbirth (Slide 13).

Trachea

A flexible, patent windpipe anterior to the esophagus supported by $15\text{--}20$ C-shaped hyaline cartilage rings that connects the larynx to the primary bronchi (Slide 15).

Carina

An internal, mucosal ridge located at the bifurcation of the trachea into the primary bronchi; populated by sensitive sensory receptors that initiate a violent cough reflex (Slide 15).

Structural hierarchy of the bronchial tree

Main (primary) bronchi $\rightarrow$ lobar (secondary) bronchi $\rightarrow$ segmental (tertiary) bronchi $\rightarrow$ smaller bronchi $\rightarrow$ bronchioles $\rightarrow$ terminal bronchioles (Slide 16).

Bronchial tree

Highly Branched system of air conducting passages, from main bronchi to Alvioli (Slide 16)

Main bronchi

The primary branches of the bronchial tree that inferiorly and laterally into each lung (Slide 16).

Lobar bronchi

The secondary branches that extend directly into each individual lobe of the lungs (Slide 16).

Segmental bronchi

The tertiary branches supply distinct bronchopulmonary segments (Slide 16).

Structural distinction between bronchi and bronchioles

Bronchi contain hyaline cartilage plates and modest smooth muscle; bronchioles lack cartilage entirely and have a relatively thick ring of smooth muscle (Slide 17).

Bronchoconstriction (parasympathetic)

Decrease in airflow(Slide 17)

Terminal bronchioles

Last portion of conducting pathways, leads into respiratory bronchial, and then the respiratory zone starts (slide 17)

Bronchodilation(sympathetic)

Increase in airflow(slide 17)

Respiratory zone

Contain respiratory bronchioles, alveolar ducts, alveoli (slide 18)

Alveolar sacs

Composed of a cluster of alveoli

Alveolus

Small, saccular outpocketing

Airflow sequence within the respiratory zone

Terminal bronchiole $\rightarrow$ respiratory bronchiole $\rightarrow$ alveolar duct $\rightarrow$ alveolar sac $\rightarrow$ alveoli (Slide 19).

Type I Alveolar Cells

Simple squamous epithelial cells that line $95\%$ of the alveolar wall, forming the extremely thin diffusion barrier of the respiratory membrane (Slide 20).

Type II Alveolar Cells

Cuboidal septal cells within alveoli that synthesize and secrete pulmonary surfactant to lower surface tension (Slide 20).

Alveolar Macrophages

Phagocytic white blood cells (dust cells) that migrate through alveolar spaces engulfing inhaled debris, dust, and microorganisms (Slide 20).

Pulmonary Surfactant

An oily phospholipid-protein secretion that breaks hydrogen bonding at the liquid-air interface of alveoli, preventing alveolar collapse during expiration (Slide 20).

Vagus nerve

Innervates smooth muscles and glands in lungs

Bronchioles innervation

Dually innervated (parasympathetic + sympathetic),

Parasympathetic causes Bronchoconstriction(Decrease in the flow of air into and out of lungs)

Sympathetic causes bronchodilation( increase in flow of air into and out of lungs)

Pleural membranes

Serous coverings comprising the visceral pleura (adhering tightly to the lung surface) and parietal pleura (lining the thoracic wall and superior diaphragm), continuous at the hilum (Slide 23).

Pleura epithelium

Simple squamous epithelium and a thin layer of areolar connective tissue

Function of serous fluid in the pleural cavity

Lubricates the pleural layers to minimize frictional abrasion during breathing and creates surface tension that keeps the lungs expanded against the thoracic wall (Slide 23).

Inflation

A result of physical changes of the chest wall, muscles pull the lungs down and out

Exhalation

Muscle relax, elastic tissue of the lungs allows them to recoil and come back into their relaxed shape

Atmospheric pressure (760 mmHg)

The pressure gasses in the air exert in the environment, standard value is 760 MMHG, as altitude changes so does atmospheric pressure

Intrapulmonary pressure

Associated with alveolar volume, collective volume of alveoli within the lungs

Intrapleural pressure

Pressure exerted within the pleurall cavity

Respiration

General term used for the exchange of respiratory gases, oxygen, and carbon dioxide

Four integrated processes of respiration

Continuous and simultaneously

Pulmonary ventilation (breathing), pulmonary gas exchange (alveolar exchange), gas transport (movement in blood), and tissue gas exchange (systemic delivery) (Slide 28).

Boyle's law in pulmonary ventilation

States that pressure is inversely proportional to volume ($P \propto 1/V$); altering thoracic cavity volume creates pressure gradients relative to atmospheric pressure that drive air into or out of the lungs (Slide 24, 25).

Standard respiratory pressures during quiet breathing

Atmospheric pressure is $760\,\text{mm Hg}$; intrapulmonary pressure drops to $759\,\text{mm Hg}$ during inspiration and rises to $761\,\text{mm Hg}$ during expiration; intrapleural pressure remains subatmospheric ($\sim 756\,\text{mm Hg}$) (Slide 25, 26, 27).

Muscle actions during quiet inspiration

The diaphragm and external intercostals contract, expanding thoracic cavity volume, lowering intrapulmonary pressure, and drawing $\sim 500\,\text{mL}$ of air inward (Slide 26).

ventilation

Replacing air in a space with fresh air

Pulmonary ventilation

Movement of air into and out of the lungs

2 cyclic processes, inspiration/expiration

Cerebrum

Consciously controls breathing

Brain stem

Unconsciously control breathing

Respiratory center

Located in brain stem

Receptors role

Detect stimuli and relay information to respiratory center

Medullary Respiratory Center

Autonomic nuclei in the medulla oblongata(Brainstem) that regulate respiratory rate via contractions of breathing muscles: via the phrenic nerves (to the diaphragm) and intercostal nerves (to external intercostals) (Slide 31).

Pontine Respiratory Center

(Pneumotaxic center) relay nerve signals to the medullary respiratory center to ensure smooth, rhythmic transitions between inspiration and expiration,

Central Chemoreceptors

Sensory neurons in the ventrolateral medulla that monitor $H^+$ concentration and $pH$ changes within the cerebrospinal fluid driven by arterial hypercapnia (Slide 32).

Peripheral Chemoreceptors

Sensory receptors located in the carotid and aortic bodies that detect arterial blood alterations in $pH$, $P_{CO_2}$, and pronounced reductions in $P_{O_2}$, Kidney failure, diabetes(ketoacidosis)

Hypercapnia

High CO2 = Low P

Alter breathing

Caused by chemoreceptors sending nerve signals to respiratory center

Erythrocyte adaptations for gas exchange

A biconcave disc morphology offering elevated surface area, absence of nuclei and organelles, and approximately $280\text{ million}$ hemoglobin molecules per erythrocyte (Slide 34).

Hemoglobin

Red pigmented protein, transports O2 + CO2

Oxygenated blood

Maximally loaded with oxygen, light red

Deoxygenated blood

Oxygen is lost, and carbon dioxide is gained during tissue gas exchange, dark red

Heme groups

Contain Fe2+ that weakly bind O2

Globins

Weakly bind Co2

Gas transport

Movement of respiratory gasses within the blood between lungs and systemic cells of body tissues

Oxygen transport in blood

Has two factors: oxygen solubility coefficient, presence of hemoglobin

Modes of oxygen transport in the blood

Approximately $98\%$ is carried chemically bound to the iron ($Fe^{2+}$) of hemoglobin inside erythrocytes, while $2\%$ dissolves directly in blood plasma due to low solubility (Slide 36).

Modes of carbon dioxide transport in the blood

Approximately $70\%$ circulates as bicarbonate ($HCO_3^-$) dissolved in plasma, $23\%$ binds to the globin chains of hemoglobin, and $7\%$ dissolves directly in plasma (Slide 36).

Carbon dioxide as a waste product

Product of cellular respiration, but does not depend on hemoglobin to be transported in blood. Instead, carbon dioxide has three means of blood transport.

Systemic capillaries : Carbonic anhydrase

Catalyzes reactions involving carbonate

Systemic capillaries : Conversion of Co2 to bicarbonate (HCO3-)

H2CO3 (carbonic acid) disassociates into bicarbonate (HCO3-) and H+

Systemic capillaries : Function of HB in conversion

The heme in HB will bind the H+ to prevent pH changes, but the bicarbonate diffuses out to RBC and into blood plasma

Pulmonary capillaries : conversion of bicarbonate back to CO2

Carbonate anhydrase Catalyzes reactions involving carbonate(H2CO3), We can convert bicarbonate back to carbon dioxide at pulmonary capillaries, hydrogen is released from hemoglobin and bicarbonate(HCO3-) re-enter the blood

Pulmonary Capillaries : Carbon dioxide diffusion

Carbon dioxide will diffuse out of red blood cells into blood and then diffuse into the alveolus

Cooperative binding of hemoglobin

Hb molecule physically changes shape by binding to O², CO², H+, this bonding will influence its ability to bond or release the other two substances

Three compounds hemoglobin can transport

Oxygen – Attached to iron on heme

Carbon dioxide – Bound to globin

Hydrogen- Bound to globin

2 Variables that influence hemoglobin’s binding and release of oxygen

Temperature and presence of 2,3 – BPG

End goal→more O² to tissues

Temperature influence on hemoglobin

metabolic activities = Increase in body temperature→ Hemoglobin becomes more flexible= More oxygen is released during tissue gas exchange

Presence of 2,3-BPG

2,3 bisphosphoglycerate is produced inside of RBCs

Excessed produced during exercise and leaves the cells to bind to Hb

Can be stimulated by GH, testosterone or low O² levels and change in altitude

During exercise

Muscles consume large amounts of O² + produce large amounts of CO²

Pulmonary ventilation (breathing/excercise)

Increases depth of breathing (hyperpnea), but rate remains the same

Higher brain centers that send neural signals to stimulate respiratory center

Limbic system (conscious anticipation of exercising)

Proprioceptors (detect movement)

Cerebral cortex promotes muscular → signals to respiratory center

Clinical application of Henry’s Law: hyperbaric Oxygenation

Pressure usage to dissolve more O² in blood

Treatment for patients w/ anaerobic bacterial infections (tetanus/gangrene)

Anaerobic bacteria die in presence of O²

Hyperbaric chamber

Pressure raised to 3-4 atmospheres so tissues absorb more O² (higher oxygen levels, results to acceleration of tissue healing rate)

Used to treat heart disorders, carbon monoxide poisoning, cerebral edema, bone infections, gas embolisms, and crush injuries

Henry's Law

A gas law establishing that the quantity of a gas dissolving into a liquid is directly proportional to the pressure of that gas over the liquid ('High Pressure = High Dissolving')

Low pressure → gas comes out of the liquid.

Restrictive Lung Diseases : reduced distensibility (stretch) of the lungs

Lungs cannot expand fully, making it hard to breathe in

Restrictive Lung Diseases : intrinsic(pulmonary causes)

From inflammatory processes in lung tissue by diseases

Restrictive Lung Diseases: Extrinsic (causes external from lungs)

Neuromuscular disorders or obesity are two examples of

Pneumothorax

Pulmonary fibrosis

Pneumothorax(collapsed lung)

Air outside lungs, within cavity

Due to smoking, asthma, cystic fibrosis, Tracheostomy

Penetrative/blunt trauma

Needle decompression as solution