Chap 4 Lesson 2 Lower Respiratory and the Process of Respiration PDF

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Chapter 4: The Respiratory System Lesson 2: Lower Respiratory System and Process of Respiration

Topics V. Lower respiratory Tract 1. Trachea 2. Bronchi and Alveoli 3. Lungs 4. Thorax 5. Pleura VI. Disorders of Lower respiratory System 1. Infections - Acute Bronchitis - Pneumonia - Tuberculosis 2. Lung Cancer

Objectives 1. Describe the structures and functions of the trachea, bronchi, bronchioles, and alveoli. 2. Identify the lobes, bronchopulmonary segments, gross surface anatomy, and generalized functions of the lungs. 3. Discuss the structures and functions of the thorax and mediastinum in respiration. 4. Discuss disorders associated with the lower respiratory tract

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V.

Lower respiratory Tract

1. Trachea Structure: It is a tube (windpipe) about 11 cm It extends from the larynx to the primary bronchi in the thoracic cavity Its diameter measures 2.5cm (1 inch) It is formed of smooth muscles in which are embedded C-shaped cartilages at regular intervals

 Figure 35.10 From Patton Anatomy and Physiology 10th Edition

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 Function It forms part of the passageway through which air can reach the lungs from the outside (Obstruction of airway causes death from asphyxiation)

 Figure 35.10 From Patton Anatomy and Physiology 10th Edition

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2. Bronchi and Alveoli Structure of bronchi The trachea divides into two primary bronchi The right bronchus is slightly larger and more vertical than the left (This is why aspirated foreign body lodge in the right bronchus) o They have incomplete cartilaginous rings in the section superior than the lung. o They are lined by ciliated mucosa

o o

Figure 35.11 From Patton Anatomy and Physiology 10th Edition

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 Bronchial tree: -

Primary bronchi branch into secondary bronchi Secondary bronchi branch to form bronchioles Bronchioles branches into smaller branches called terminal bronchioles The terminal bronchioles divide into respiratory bronchioles The respiratory bronchioles proceed onward into alveolar ducts Alveolar ducts end into one or more alveolar sacs

 Huther’ s 7th Edition

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 Structure of alveoli -

They are the primary gas exchange structures Their walls are extremely thin and lies in contact with blood capillaries There are millions of alveoli in each lung The respiratory membrane (barrier across which gases are exchanged) is formed of alveolar epithelium  Capillary endothelium

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The inside of alveoli is coated by a fluid that prevent the collapse of the alveoli this fluid is called surfactant

Functions of bronchi and alveoli o o o

The tubes forming the bronchial tree distribute the air to the lung interior The alveoli accomplish the gas exchange between the air and blood The layer of protective mucus that covers a large portion of the membrane that lines the respiratory tree serves as the most important air purification mechanisms

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3. Lungs  Structure of the lungs The lungs are cone shaped organs; they fill the pleural portion of the thoracic cavity -

They extend from the diaphragm to a point slightly above the clavicles; and lie against the ribs both anterior and posterior

 Figure 35.17 From Patton Anatomy and Physiology 10th Edition

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 The root of the lung The primary bronchi enter the lung from its medial surface through the hilum The base of the lung The broad inferior surface of the lung, it rests on the diaphragm The apex of the lung It projects above the clavicle The costal surface The surface that lies against the ribs; it is rounded to match the contour of the ribs Lobes of the lungs The left lung is divides into 2 lobes (superior and inferior) The right lung is divided into 3 lobes (superior, middle and inferior) Fissure of the lungs An oblique fissure is found in both lungs A horizontal fissure is found only in the right lung separating the superior lobe from the middle lobe. The secondary bronchi enter each lobe (thus the right lung has 3 bronchi) Functions of the lungs Air distribution by the bronchial tree Gas exchange between the air and blood is a function of the alveoli and the capillaries that envelop them 4. Thorax o o

Structure of the thoracic cavity The thoracic cavity has 3 divisions:  Pleural divisions are the parts occupied by the lungs  Mediastinum division the part occupied by the esophagus, trachea, large blood vessels, and the heart The parietal pleura lines the entire thoracic cavity; adhering to the internal surface of the ribs and the superior surface of the diaphragm The visceral pleura lies against the parietal pleura They are separated by pleural space containing pleural fluid for lubrication Functions of the thoracic cavity It plays a major role in respiration (The thorax become larger in inspiration)

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5. Pleura

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Two layered structure: 1- Parietal pleura lines the inner thoracic wall, the diaphragm and the mediastinum. 2- Visceral pleura that covers the lungs. The pleural cavity is filled with pleural fluid produced by the pleural membranes and it acts as a lubricant and helps hold the two layers of the pleura together.

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Intrapleural Pressure: The pressure within this pleural cavity The intrapulmonary Pressure: (intra alveolar) The pressure within the lungs.

[The intrapleural pressure is less than the intrapulmonary pressure.] ฀

Transpulmonary pressure: The difference between the intrapleural pressure (outside of the lungs) and the intrapulmonary pressure (that's inside the lungs).

Implication: The lower intrapleural pressure outside the lungs creates a vacuum that keeps the lungs expanded and prevents them from collapsing. 

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VI.

Disorders of Lower respiratory System

1. Lower respiratory tract infection Acute bronchitis Acute inflammation of the tracheobronchial tree caused mainly by infection. The protective functions of the bronchial epithelium are disturbed, and excessive fluid accumulates in the bronchi. Often begins with nonproductive cough, malaise, slight fever, muscle pain and sore throat.

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 Pneumonia Acute inflammation of the lungs. Alveoli and bronchi become swollen and plugged with mucous secretions. Common cause is Streptococcus pneumoniae bacteria but could also be caused by viral infections (SARS-COV) Aspiration pneumonia is caused by inhalation of vomit or other infective material Always associated with high fever, chills, headache, cough and chest pain, leukocytosis and hypoxia.

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 SARS – SEVERE ACUTE RESPIRATORY SYNDROME: Definition: Rapidly progressing viral pneumonia caused by the SARS-associated coronavirus (SARS-CoV) Etiology: SARS-Associated Coronavirus Incubation: 2-7 days Pathophysiology: o Droplet Transmission -Human to Human o Respiratory Tract Infection with SARS-Associated Coronavirus o Atypical Pneumonia +/- Respiratory Distress Syndrome Clinical Features: Difficult to Differentiate SARS from other Community-Acquired Pneumonias Because the initial Symptoms Are Not Specific: - Fever, Chills, Malaise, - Headache, Myalgia, - Cough, Sore Throat, Productive Cough However, 2/3 Of Patients Deteriorate with: Persistent Fever desaturation

Shortness of Breath &

20% Require ICU Admission and Mechanical Ventilation Complications: o o o

Respiratory failure Liver failure Heart failure

Diagnosis: o Clinical Suspicion – Symptoms, Hx of Travel, Hx of Contact Investigations: o Chest Xray: Features of Atypical Pneumonia o Lab: Neutrophilia, Lymphopenia, CRP,

LDH

o RT-PCR: from Blood/Sputum/NPA/Swabs. o Serology:(antibody detection via ELISA)

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 Treatment: o Notify public health o Quarantine (negative-pressure room, N95 Mask, gown, gloves, eye protection) o Antivirals (Ribavirin) o Steroids - (To prevent immune mediated lung damage) www.

Tuberculosis Chronic bacillus infection caused by Mycobacterium tuberculosis. Airborne transmission. Inflammatory lesions (tubercles) form around the TB bacilli. Symptoms include cough, fatigue, chest pain, weight loss and fever. As the disease progresses, hemorrhage and dyspnea develop.

2. Lung cancer Malignancy of the pulmonary tissue that not only destroys the vital gas exchange tissues of the lungs but also may invade other parts of the body (metastasis) Predisposed by smoking, asbestos, chromium, coal products, petroleum products, rust and ionizing radiation.

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