The Respiratory System ACCURATE !

What are the two main structural areas of the respiratory tract?

The upper respiratory tract (nose to pharynx) and the lower respiratory tract (larynx to lungs)

What are the two main functional zones of the respiratory tract?

The conducting zone, which warms, humidifies, and conducts air (pulmonary ventilation), and the respiratory zone, which performs gas exchange at the respiratory epithelium (alveolar ventilation)

What is external respiration?

The exchange of gases between the body and the external environment, involving pulmonary ventilation and alveolar gas diffusion

What is internal respiration?

The exchange of gases between the blood and body tissues—oxygen moves into tissues while carbon dioxide moves out

What is cellular respiration?

The production of ATP from glucose oxidation through glycolysis, the Krebs cycle, and oxidative phosphorylation within cells

List the main functions of the respiratory system.

(1) External respiration, (2) Transport of gases by blood, (3) Internal respiration, (4) Sound production (phonation), (5) Olfactory assistance, (6) Protection via mucus/cilia/cough, (7) Warming & moistening of air, (8) Acid

What is the primary function of the respiratory system?

Internal respiration, which supplies oxygen to and removes carbon dioxide from body tissues

How does the conducting zone differ from the respiratory zone?

The conducting zone involves bulk airflow (no gas exchange) and ends at terminal bronchioles, while the respiratory zone begins at respiratory bronchioles and is where diffusion of O₂ and CO₂ occurs

What is pulmonary ventilation?

The bulk flow of air into and out of the lungs, often referred to as the “act of breathing”

What is alveolar ventilation?

The diffusion of gases across the respiratory epithelium at the alveoli, responsible for gas exchange

Why is alveolar ventilation important?

Because pulmonary ventilation alone doesn’t bring oxygen into the bloodstream diffusion across alveoli is necessary for O₂ to enter blood

What is perfusion in the respiratory context?

The amount of blood flowing through lung capillaries that participates in gas exchange

What factors influence gas exchange?

Pressure gradients (difference in gas levels), solubility of gases in plasma, and perfusion (blood availability at alveoli)

What are the four paranasal sinuses?

Frontal, Ethmoid, Maxillary, and Sphenoid sinuses

What are the main functions of the paranasal sinuses?

Secrete mucus to filter pathogens, warm and moisten air, lighten the skull, assist in voice resonance, and secrete immune components like IgA and lysozyme

What kind of tissue lines the nasal cavity?

Ciliated pseudostratified columnar epithelium containing goblet cells

What are the functions of the nasal cavity lining?

Warms and moistens incoming air, traps foreign particles, and supports olfaction by bringing odorants to olfactory epithelium

What are nasal conchae (turbinates)?

Curved bony structures (superior, middle, inferior) that increase air turbulence in the nasal cavity, enhancing filtration and humidification

What is the larynx?

A cartilaginous structure connecting the pharynx to the trachea that routes air and food properly and produces sound

What happens in the larynx during swallowing?

The epiglottis covers the trachea to prevent food from entering the airway

What are the two largest cartilages of the larynx?

The thyroid cartilage (forms the Adam’s apple) and the cricoid cartilage (only one that completely encircles the larynx)

What is the role of the cricoid cartilage?

Serves as the attachment site for vocal cord muscles and supports the airway structure

How are sounds produced in the larynx?

Air passes through and vibrates the vocal cords, with sound pitch determined by the length and tension of the cords

When are vocal cords open vs. closed?

Open during breathing to allow air passage, and open/close rapidly during speech to produce sound

What is the trachea?

A tubular structure that transports air from the neck into the thoracic cavity, branching into the right and left primary bronchi

What are the three tissue layers of the trachea?

Mucosa (inner), Submucosa (middle), and Adventitia (outer)

What characterizes the mucosa of the trachea?

Ciliated pseudostratified columnar epithelium with goblet (mucus

What is found in the submucosa of the trachea?

Dense connective tissue, glandular epithelium, hyaline cartilage C

What is the trachealis muscle?

The smooth muscle at the posterior trachea that adjusts the width of the airway for airflow regulation

What characterizes the adventitia layer of the trachea?

Loose connective tissue containing collagen, nerve endings, and small blood vessels (vasa vasorum)

Into what does the trachea branch?

Into two primary (1°) bronchi — the right and left

How does the left primary bronchus differ from the right?

It is more horizontal due to the heart’s position

How do bronchi branch as they enter the lungs?

Primary bronchi → secondary (lobar) bronchi → tertiary (segmental) bronchi → bronchioles → terminal bronchioles

When do bronchi become bronchioles?

When cartilage disappears the more branching, the less cartilage and more smooth muscle

What are alveoli?

Thin epithelial sacs where gas exchange occurs between air and blood

What are the three major cell types in alveoli?

Type I alveolar cells (simple squamous gas exchange), Type II alveolar cells (simple cuboidal secrete surfactant), and alveolar macrophages (phagocytize debris and microbes)

What is the function of surfactant?

Reduces surface tension within alveoli to prevent collapse during exhalation

What is the respiratory membrane composed of?

Type I alveolar cells, their basement membrane, fused with the capillary endothelium and its basement membrane

How large is the total alveolar surface area?

Approximately 1,400 square feet (about half a tennis court), maximizing gas diffusion

What is pulmonary ventilation?

The movement of air into and out of the lungs by bulk flow, driven by pressure differences

What causes air movement in and out of the lungs?

Air always moves from areas of high pressure to low pressure

What are the three main pressures involved in ventilation?

Atmospheric pressure (outside air), Intrapulmonary pressure (inside lungs), and Intrapleural pressure (in pleural cavity)

How does Boyle’s Law relate to ventilation?

In a closed system, volume and pressure are inversely proportional—when lung volume increases, pressure decreases, drawing air in

What happens during inspiration?

The diaphragm and external intercostal muscles contract, increasing thoracic volume and decreasing intrapulmonary and intrapleural pressures

What happens during expiration?

The diaphragm and external intercostals relax, decreasing thoracic volume and increasing intrapulmonary and intrapleural pressures

What muscles are active in forced expiration?

Internal intercostals (narrow cavity) and abdominal muscles (push diaphragm upward to increase pressure)

Why do intrapulmonary and intrapleural pressures change together?

Because the pleural membranes move synchronously, maintaining a constant pressure difference

What are the five muscles of inspiration?

Diaphragm, external intercostals, sternocleidomastoid, scalenes, and pectoralis minor

What are the four muscles of expiration?

Diaphragm, internal intercostals, abdominals, and quadratus lumborum

What determines airway resistance?

The size of the airway’s lumen

wider airways have less resistance, narrower airways have more

Which part of the respiratory tract has the most resistance?

The bronchioles, due to their small diameter and smooth muscle control

How does the autonomic nervous system affect bronchioles?

Sympathetic division causes bronchodilation (wider airways), parasympathetic division causes bronchoconstriction (narrower airways)

What is surface tension in alveoli?

The cohesive attraction between water molecules that resists expansion and can cause alveolar collapse

How is alveolar surface tension reduced?

Type II alveolar cells secrete surfactant, which disrupts hydrogen bonding in alveolar fluid

Where does pulmonary gas exchange occur?

At the respiratory membrane between alveolar air and capillary blood

Where does systemic gas exchange occur?

Between capillary blood and body tissues

How do gases move during pulmonary exchange?

O₂ diffuses into blood (higher alveolar PO₂), CO₂ diffuses out (higher blood PCO₂)

How do gases move during systemic exchange?

O₂ diffuses into tissues (higher blood PO₂), CO₂ diffuses into blood (higher tissue PCO₂)

What determines direction of gas diffusion?

Partial pressure gradients (high → low)

What is alveolar perfusion?

The blood flow through pulmonary capillaries available for gas exchange

What happens when ventilation and perfusion are unequal?

Low ventilation = insufficient O₂ high ventilation = insufficient blood flow for exchange

What protein primarily transports oxygen and carbon dioxide?

Hemoglobin in red blood cells

How many gas molecules can one hemoglobin carry?

Four gas molecules (one per heme group), allowing ~1 billion per RBC

How is CO₂ transported in the blood?

7% dissolved in plasma, 23% bound to hemoglobin, 70% converted into bicarbonate (HCO₃⁻) and H⁺ ions

Which brain structures regulate respiration?

The medulla oblongata and the pons

What does the medullary respiratory center do?

Sets the basic respiratory rhythm through its ventral and dorsal respiratory groups

What is the function of the ventral respiratory group (VRG)?

Generates signals for forced inspiration and expiration primary driver of respiration

What is the function of the dorsal respiratory group (DRG)?

Controls contraction of diaphragm and intercostals for normal inspiration modifies VRG output via feedback

What are the roles of the pontine respiratory centers?

Coordinate smooth respiratory muscle contractions between inhalation and exhalation

What is the pneumotaxic center?

Inhibits the DRG to end inspiration and regulate breathing rate with physical effort

What is the apneustic center?

Activates the DRG to prolong inspiration, particularly for deep breathing

What do chemoreceptors in the medulla detect?

Changes in pH and CO₂ levels in cerebrospinal fluid (no direct O₂ receptors)

Where are peripheral chemoreceptors located?

In the carotid and aortic bodies, monitoring blood pH and CO₂

How does signal number affect breathing?

Increased signal number increases breathing rate

How does signal strength affect breathing?

Increased signal strength increases breathing depth

What is hyperpnea?

An increased breathing rate and depth

occurs during exercise or hyperventilation

How does exercise affect respiration?

Breathing rate and depth rise to meet metabolic demand, balancing O₂ intake and CO₂ output

What happens during hyperventilation?

Breathing rate increases without need

CO₂ levels drop (hypocapnia), altering blood pH

What is COPD?

Chronic obstructive pulmonary disease: a group of irreversible lung disorders reducing airflow and gas exchange

What are the two main types of COPD?

Emphysema and chronic bronchitis

What happens in emphysema?

Alveoli weaken and rupture, reducing surface area for gas exchange

results in shortness of breath and barrel chest

What happens in chronic bronchitis?

Chronic inflammation of bronchi increases mucus production, leading to persistent productive cough

What is the leading cause of COPD?

Cigarette smoking

What are the three main types of lung cancer?

Adenocarcinoma (bronchial glands/alveolar cells), Squamous cell carcinoma (bronchial epithelium), and Small cell carcinoma (primary bronchi)

Why is early detection important in lung cancer?

It greatly improves survival outcomes

What happens when the respiratory membrane thickens?

Gas diffusion slows, reducing oxygen exchange

What happens when alveolar surface area decreases?

Less area for diffusion → decreased gas exchange efficiency

What is asthma?

A condition where environmental triggers cause sudden airway inflammation and constriction

What relieves asthma symptoms?

Bronchodilator inhalers that expand bronchioles and improve airflow

What is tuberculosis (TB)?

A bacterial infection caused by Mycobacterium tuberculosis, most commonly affecting the lungs and killing ~1.3 million people per year

Why is TB dangerous?

It forms resistant granulomas in lung tissue, impeding gas exchange

What are the. 4 functions of Nose/ Nasal Cavity 

1. warm and moisten air

2. trap and filter foreign particle (ciliated pseudostratified epithelium)

3. olfaction

4. voice resonation

Nasopharynx

directly behind the nasal cavity

• It only transports air 

• the uvula blocks this structure during swallowing 

Oropharynx

Directly behind the Oral cavity

• It transport air AND FOOD 

• the palatine tonsils are found here 

Laryngopharynx

is splits into the larynx & the esophagus

• It transports (larynx) air and Food ( esophagus) 

• The epiglottis covers the glottis ( lumen) of the larynx during swallowing 

Alveolar contributions

• type I alveolar cells (simple squamous epithelium)

• The basement membrane (of the Type I alveolar cells )