Respiratory

Respiratory System Disorders

Emphysema

• Characterized by the enlargement of alveoli as adjacent chambers break through.

• Chronic inflammation promotes the formation of lung fibrosis.

• Airways tend to collapse during the expiration phase of breathing.

• Patients expend a significant amount of energy to exhale due to the compromised airflow.

• Overinflation of the lungs results in a permanently expanded chest, often resembling a barrel shape.

• Cyanosis (bluish discoloration of the skin due to lack of oxygen) appears late in the disease progression.

Chronic Bronchitis

• The mucosa (the mucous membrane) of the lower respiratory passages becomes severely inflamed.

• There is an increase in mucus production, which can lead to pooled mucus that impairs both ventilation and gas exchange.

• The risk of lung infections increases substantially.

• Pneumonia is common among individuals suffering from chronic bronchitis.

• Early signs of the condition include hypoxia (deficiency in the amount of oxygen reaching tissues) and cyanosis.

Respiratory Disorders: Chronic Obstructive Pulmonary Disease (COPD)

• COPD includes conditions such as chronic bronchitis and emphysema.

• It is one of the leading causes of death and disability in the United States.

• Common features and implications of COPD include:

  • A typical patient almost always has a history of smoking, which is a major contributing factor.

  • Patients experience labored breathing (dyspnea), which becomes progressively more severe over time.

  • Coughing and frequent pulmonary infections are prevalent among those suffering from COPD.

• Most victims of COPD retain carbon dioxide in their bodies, leading to hypoxia and the development of respiratory acidosis.

• Without intervention, those infected will ultimately suffer from respiratory failure.

Chronic Obstructive Pulmonary Disease (COPD) Detailed Overview

• Major factors leading to COPD include:

  • Tobacco smoke

  • Air pollution

• Continual bronchial irritation and inflammation contribute to this respiratory condition.

• Breakdown of elastin (a protein that allows for stretch and elasticity) in the connective tissue of the lungs is a notable pathological change.

  • Chronic bronchitis:

  • Characterized by excessive mucus production, chronic productive cough, and bronchospasm (constriction of the airways).

  • Emphysema:

  • Involves the destruction of alveolar walls, leading to lung fibrosis and air trapping.

• Common symptoms of COPD include:

  • Airway obstruction or air trapping

  • Dyspnea

  • Frequent infections

  • Potential progression to respiratory failure.

Asthma

• Defined as a chronic condition where bronchiole passages become inflamed and hypersensitive.

• Asthmatic episodes are generally a response to irritants and lead to symptoms such as:

  • Dyspnea (difficulty breathing)

  • Coughing

  • Wheezing (a whistling or rattling sound when breathing).

Pneumonia

• An infection that causes inflammation of the alveoli (air sacs in the lungs).

• Inflamed alveoli may fill with fluid or pus, which significantly impairs respiration.

• Symptoms of pneumonia include:

  • Cough

  • Fever

  • Difficulty breathing.

Lung Cancer

• Lung cancer is responsible for approximately one-third of all cancer deaths in the United States.

• The incidence of lung cancer is significantly associated with smoking habits.

• Three common types of lung cancer include:

  • Squamous cell carcinoma

  • Adenocarcinoma

  • Small cell carcinoma.

Bronchial Anatomy and Gas Exchange

• Bronchiole: Small air passages in the lungs that branch out from the bronchi.

• Gas Exchange: Crucial process in the respiratory system where oxygen and carbon dioxide are exchanged.

• Right Bronchus: Larger and straighter than the left; directs air into the right lung.

• Trachea: Also known as the windpipe, it connects the larynx to the bronchi, allowing the passage of air.

• Intercostal Muscles: Muscles located between the ribs that assist in breathing by expanding and contracting the thoracic cavity.

• Diaphragm: A dome-shaped muscle at the base of the thoracic cavity that plays a major role in breathing.

• Alveoli: Tiny air sacs (approximately 300 million in the lungs) where gas exchange occurs.

Respiratory Membrane Composition

• Respiratory Membrane (Air-Blood Barrier): Consists of several components facilitating gas exchange:

  • Surfactant-secreting Cells: Secrete surfactant to reduce surface tension in the alveoli.

  • Squamous Epithelial Cells of Alveolar Wall: Form the thin layer of the alveoli for efficient diffusion.

  • Endothelial Cell: Lines the capillaries, facilitating gas exchange.

  • Macrophage: Immune cells that protect the alveoli by engulfing pathogens and debris.

  • Oxygen (O2) and Carbon Dioxide (CO2): Gases exchanged during respiration, facilitated by the structure of the respiratory membrane.

Gas Exchange Mechanism

• Diffusion: The primary method by which gas molecules move across the respiratory membrane:

  • Oxygen enters the blood due to a higher concentration in the alveoli compared to the pulmonary capillaries.

  • Carbon dioxide moves from the blood into the alveoli where its concentration is lower.

• Macrophages: Provide protection within the alveoli by engulfing harmful microorganisms and particles.

• Surfactant: A substance that coats the gas-exposed surfaces of the alveoli, preventing collapse and aiding in gas exchange.

Events of Respiration

• There are four distinct events involved in respiration:

  1. Pulmonary Ventilation: The act of moving air in and out of the lungs.

  2. External Respiration: The process of gas exchange between the pulmonary blood and alveoli, where oxygen enters the blood and carbon dioxide is expelled.

  3. Respiratory Gas Transport: The transportation of oxygen and carbon dioxide in the bloodstream.

  4. Internal Respiration: The exchange of gases between blood and tissue cells, occurring in systemic capillaries.

Mechanics of Breathing (Pulmonary Ventilation)

• Definition: A completely mechanical process involving muscle contractions and pressure changes to facilitate airflow.

• Volume Changes: Alterations in the thoracic cavity volume lead to pressure changes which result in airflow.

Phases of Breathing

• Inspiration: The flow of air into the lungs.

  • Involves the contraction of diaphragm and intercostal muscles.

  • Thoracic cavity size increases, creating a pressure drop that pulls air into the lungs.

• Expiration: The act of air leaving the lungs.

  • Largely passive due to the elastic recoil of lung tissues.

  • Forced expiration occurs through the contraction of internal intercostal muscles.

Detailed Process of Inspiration

• Diaphragm Contraction: When the diaphragm contracts, it moves downward, increasing the thoracic cavity's volume.

• Changes in Dimensions:

  • Anterior-Posterior and Superior-Inferior Dimensions: Ribs are elevated as external intercostal muscles contract, leading to increased thoracic cavity size.

  • Lateral Dimensions: Increases as the external intercostal muscles cause the rib cage to expand.

Detailed Process of Exhalation

• Passive Process: Most of the air is expelled from the lungs passively due to elastic recoil.

• Muscle Relaxation: As the diaphragm and intercostal muscles relax, the thoracic cavity reduces in size, pushing air out.

• Forced Expiration: Can occur through the contraction of internal intercostal muscles to further reduce ribcage volume.

External Respiration

• Oxygen Movement: Oxygen from the alveoli diffuses into the blood of the pulmonary capillary, as the concentration is higher in the alveoli than in the blood.

• Carbon Dioxide Movement: CO2 from the blood is released into the alveoli, as it is at a higher concentration in the blood than in the alveoli, resulting in carbon dioxide-rich blood leaving the lungs.

Gas Transport in the Blood

• Oxygen Transport:

  • Mostly occurs within red blood cells, where oxygen binds to hemoglobin to form oxyhemoglobin (HbO2).

  • A small percentage of oxygen is transported dissolved in the plasma.

• Carbon Dioxide Transport:

  • Most carbon dioxide is transported as bicarbonate ions (HCO3-) in the plasma.

  • Some CO2 binds to hemoglobin at different sites than oxygen.

Internal Respiration

• Gas Exchange Mechanism: Carbon dioxide diffuses out from tissue cells into the blood, while oxygen diffuses from the blood into tissue cells.

• This reaction is essentially the opposite of what happens during external respiration in the lungs.

Summary of External and Internal Respiration

• External Respiration: Involves the exchange of gases in the lungs where oxygen is loaded onto hemoglobin and CO2 is unloaded from the blood.

• Internal Respiration: Entails the exchange of gases at the tissue level, where oxygen is unloaded to tissues and carbon dioxide is loaded onto blood for transport back to the lungs.

• Chemical Reactions: Involve bicarbonate ions, carbonic acid, and the release of gases between blood and alveoli/tissues:

  • $Hb + O_2 <br>ightleftharpoons HbO_2$ (Oxyhemoglobin formation)

  • Carbon dioxide and water reactions, forming carbonic acid and bicarbonate ions relevant for transport:

  • $CO_2 + H_2O <br>ightleftharpoons H_2CO_3 <br>ightleftharpoons H^+ + HCO_3^-$

• Overall Exchange: Facilitated through the lung capillary systems and systemic capillary networks for effective gas delivery and removal.

• Oversees gas exchanges between:

  • External environment and lungs

  • Lungs and blood

  • Blood and body tissues

• Passageways to the lungs:

  • Purify incoming air

  • Warm incoming air

  • Humidify incoming air

Organs of the Respiratory System

• Main structures include:

  • Nose

  • Pharynx

  • Larynx

  • Trachea

  • Bronchi

  • Lungs (including alveoli)

The Nose

• The only externally visible part of the respiratory system

• Air enters through the external nares (nostrils)

• The interior consists of a nasal cavity, which is divided by a nasal septum

Anatomy of the Nasal Cavity

• Olfactory receptors:

  • Sense of smell located in the mucosa on the superior surface

• Respiratory mucosa lines the rest of the cavity:

  • Moistens air

  • Traps incoming foreign particles

  • Contains a rich network of veins that warms air

• Lateral walls:

  • Have projections called conchae

  • Increase surface area

  • Increase air turbulence within the nasal cavity

• The nasal cavity is separated from the oral cavity by the palate:

  • Anterior hard palate (bone)

  • Posterior soft palate (muscle)

Pharynx (Throat)

• Muscular passage from the nasal cavity to the larynx

• Divided into three regions:

  • Nasopharynx:

  • Superior region located behind the nasal cavity

  • Oropharynx:

  • Middle region located behind the mouth

  • Laryngopharynx:

  • Inferior region attached to the larynx

• The oropharynx and laryngopharynx serve as common passageways for air and food

Larynx (Voice Box)

• Functions:

  • Routes air and food into their proper channels

  • Plays a role in speech

• Structure:

  • Composed of eight rigid hyaline cartilages and a spoon-shaped flap of elastic cartilage called the epiglottis

Structures of the Larynx

• Thyroid cartilage:

  • The largest hyaline cartilage

  • Protrudes anteriorly (known as the Adam’s apple)

• Epiglottis:

  • Superior opening of the larynx

  • Routes food to the esophagus and air toward the trachea

• Vocal cords (vocal folds):

  • Vibrate with expelled air to create sound (speech)

• Glottis:

  • Opening between vocal cords

Trachea (Windpipe)

• Connects the larynx with bronchi

• Lined with ciliated mucosa:

  • Cilia beat continuously in the opposite direction of incoming air

  • Expels mucus loaded with dust and other debris away from the lungs

• Walls are reinforced with C-shaped hyaline cartilage

Bronchi

• Primary Bronchi:

  • Formed by the division of the trachea

  • Enter the lung at the hilus (medial depression)

  • Right bronchus is wider, shorter, and straighter than the left

  • Bronchi subdivide into smaller and smaller branches

Respiratory Tree Divisions

• Primary bronchi

• Secondary bronchi

• Tertiary bronchi

• Diagrammatic representation:

  • Larynx → Primary bronchus → Secondary bronchus → Tertiary bronchus → Trachea

• Associated anatomical structures include:

  • Carina

  • Left Lung

  • Parietal pleura

  • Visceral pleura

  • Bronchioles

  • Terminal bronchioles

  • Diaphragm

Bronchioles

• Bronchioles are the smallest branches of the bronchi and lead to:

  • Alveolar duct

  • Alveoli

• Alveolar duct connects to alveoli

Lungs

• Occupy most of the thoracic cavity

• Apex:

  • Near the clavicle (superior portion)

• Base:

  • Rests on the diaphragm (inferior portion)

• Each lung is divided into lobes by fissures:

  • Left lung:

  • Contains two lobes

  • Right lung:

  • Contains three lobes

Coverings of the Lungs

• Parietal pleura:

  • Lines the walls of the thoracic cavity

• Pulmonary (visceral) pleura:

  • Covers the lung surface

• Pleural fluid:

  • Fills the area between the layers of pleura to allow gliding and prevent friction

Alveoli

• Site of gas exchange within the respiratory membrane

• Composed of:

  • Thin squamous epithelial layer lining alveolar walls

  • Pulmonary capillaries covering the external surfaces of alveoli