Chapter 24: Respiratory System

please organize these teacher notes, do no add any more or other information, keep the original text. only refine long sentences into understandable statements--IF NECESSARY

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I. Functions

A. Functions of the Respiratory System:

1. Gas exchange:

   • Allows oxygen from the air to enter the blood.

   • Allows carbon dioxide in the blood to leave the body in exhaled air.

   • Involves inspiration (inhalation) and expiration (exhalation).

2. Helps maintain the proper acid-base balance of the blood.

   • CO2 in the blood reacts with water to form carbonic acid.

3. Produces vocal sounds through phonation.

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B. Divisions

1. Upper Respiratory System:

   • Structures: Nose, paranasal sinuses, pharynx, nasal cavity.

   • Function: "Condition the air" by:

     • Humidifying, warming, and filtering the air (via nose hairs and mucus).

     • Protects the lower respiratory system from debris, pathogens, and temperature extremes.

2. Lower Respiratory System:

   • Structures: Larynx, trachea, bronchi, lungs.

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II. Upper Respiratory System

A. Nasal Cavity

1. Superior, middle, and inferior nasal conchae:

   • Create air turbulence and increase the surface area for warming and humidifying the air.

2. Superior, middle, and inferior meatuses:

   • Spaces between the conchae.

3. Nasal septum:

   • Made from the ethmoid and vomer bones.

4. Eustachian tube opening:

   • Connects the middle ear to the pharynx.

B. Paranasal Sinuses

1. Sinuses:

   • Frontal sinuses (2), sphenoid air cells, ethmoid air cells, maxillary sinuses (2).

2. Functions:

   • Reduce the weight of the skull.

   • Help voice resonance.

C. Epithelium

1. Stratified squamous epithelium:

   • Found near the nares (nostrils).

2. Ciliated pseudostratified columnar epithelium with goblet cells:

   • Known as respiratory epithelium, found in most of the nasal cavity.

3. Olfactory epithelium:

   • Located in the roof of the nasal cavity for detecting odors.

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III. Lower Respiratory Tract

A. Larynx

• Superiorly: Attaches to the hyoid bone.

• Inferiorly: Continuous with the trachea.

1. Epiglottis:

   • Made of elastic cartilage.

   • Functions to prevent food from entering the trachea during swallowing.

2. Cartilages Supporting the Larynx & Vocal Cords:

   • Thyroid cartilage (1): Large, consists of 2 cartilage plates.

     • Laryngeal prominence ("Adam's apple").

   • Cricoid cartilage: The only cartilage that forms a complete ring.

   • Arytenoid cartilages (2): Anchor the vocal cords.

   • Corniculate cartilages (2).

   • Cuneiform cartilages (2).

3. Ligaments & Membranes:

   • Thyrohyoid ligament.

   • Thyroid membrane.

   • Cricothyroid ligament.

   • Cricotracheal ligament.

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B. Vocal Cords

1. Vestibular Ligament (False Vocal Cord):

   • Superior to the true vocal cords.

   • Play no part in sound production.

2. Vocal Ligament (True Vocal Cord):

   • Inferior to the vestibular ligament.

   • Located between the thyroid cartilage and arytenoid cartilages.

   • Made of ligament covered with mucosal folds.

     • The mucosa is avascular, giving it a pearly white appearance.

   • Involved in sound production and determining pitch.

   • The glottis is the space between the true vocal cords.

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C. Epithelium

• Below vocal cords:

  • Ciliated pseudostratified columnar epithelium with goblet cells (also called "respiratory epithelium").

  • Forms the mucociliary escalator: a mechanism that moves mucus and trapped particles upward toward the throat to be cleared.

D. Trachea

1. Function: Connects the larynx to the primary bronchi.

2. Cartilage:

   • Composed of 16-20 C-shaped hyaline cartilage rings (also called tracheal cartilages).

   • The open part of the "C" faces the esophagus, allowing it to expand during swallowing.

   • Annular ligaments alternate between the cartilage rings, providing flexibility.

3. Lining: Lined with respiratory epithelium.

4. Carina: The split or bifurcation of the trachea into the left and right primary bronchi.

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III. Lower Respiratory Tract

E. Bronchial Tree

1. Primary (Main) Bronchi:

   • The left and right primary bronchi lead to the left and right lungs, respectively.

   • The right bronchus is shorter and straighter, so accidentally inhaled objects are more likely to go to the right lung.

2. Secondary Bronchi (Lobar):

   • These branch into each lobe of the lung.

   • Right lung: has superior, middle, and inferior lobar bronchi.

   • Left lung: has only superior and inferior lobar bronchi.

3. Tertiary Bronchi (Segmental):

   • These supply segments of the lung lobes.

   • Smooth muscle surrounds the smaller bronchi and bronchioles.

   • Asthma is caused by the constriction of these smooth muscles, which narrows the airway.

4. Bronchioles (Less than 1 mm in diameter):

   • The cartilaginous rings disappear, and elastin is present instead.

   • No cilia or mucus-secreting cells are found in the bronchioles.

   • Debris that isn't trapped in mucus must be cleared by macrophages.

5. Terminal Bronchioles (Less than 0.5 mm in diameter):

   • The last part of the conducting zone before the respiratory bronchioles.

6. Respiratory Bronchioles:

   • These contain alveoli and are part of the respiratory zone.

7. Alveolar Sacs with Alveoli:

   • Alveoli are made of very thin simple squamous cells called Type I cells (around 0.5 μm, about 15 times thinner than a sheet of tissue paper).

   • The alveolar sac is surrounded by capillaries where gas exchange occurs (this is part of the respiratory epithelium).

   • Type II cells produce surfactant, a lipoprotein film that lowers surface tension inside the alveoli, preventing collapse.

   • Resident macrophages help clear any remaining debris.

Pneumonia:

• Pneumonia occurs when alveoli fill with fluid, and gas exchange becomes compromised, which is a dangerous condition.

Difference Between Bronchitis and Pneumonia:

• Bronchitis: Inflammation of the bronchi, often due to infection or irritants, leading to coughing and mucus production.

• Pneumonia: Inflammation or infection of the alveoli in the lungs, where fluid or pus fills the alveolar spaces, impairing gas exchange.

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IV. Pleura

1. Structure:

   • Each lung is enclosed by a double serous membrane called the pleura.

   • Parietal Pleura: Lines the chest wall and diaphragm.

   • Visceral Pleura: Covers the surface of the lungs.

2. Pleural Cavity:

   • The space between the parietal pleura and visceral pleura.

   • Filled with pleural fluid, which reduces friction during breathing and allows the lungs to expand and contract smoothly.

V. Lungs

1. External Structures:

   • Apex: The pointed superior end of the lung, located just deep to the clavicle.

   • Base: The concave inferior end of the lung, which contacts the diaphragm.

   • Costal Surface: The surfaces of the lung that are in contact with the ribs, including the anterior, lateral, and posterior surfaces.

   • Hilum: The indentation on the lung where blood vessels and bronchi enter and exit the lung.

   • Cardiac Notch: A small indentation in the left lung, allowing space for the heart.

2. Lobes of the Lungs:

   • Right Lung: Contains 3 lobes—superior, middle, and inferior.

   • Left Lung: Contains 2 lobes—superior and inferior.

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VI. Muscles of Respiration

A. Primary Respiratory Muscles

1. Diaphragm: The main muscle responsible for inhalation by contracting and expanding the thoracic cavity.

2. External Intercostals: Located between the ribs, they elevate the ribs during inhalation, expanding the chest.

B. Accessory Respiratory Muscles

• Inhalation (Accessory Muscles):

  1. Sternocleidomastoid: Lifts the sternum, aiding in deep inhalation.

  2. Scalenes: Lift the first 2 ribs to help expand the chest.

  3. Pectoralis Minor: Elevates ribs 2-5, assisting with deep inhalation.

  4. Serratus Anterior: Lifts the ribs, contributing to inhalation.

• Exhalation (Accessory Muscles):

  1. Transversus Abdominis: Compresses the abdomen, helping to push air out during forced exhalation.

  2. Internal Intercostals: Depress the ribs to aid in exhalation.

  3. Rectus Abdominis & Obliques: Compress the abdomen, forcing the diaphragm upwards and assisting in forced exhalation.

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C. Respiration FOLLOWS Boyle's Law

• Boyle’s Law: This law states that pressure (P) is inversely related to volume (V) for a given amount of gas at a constant temperature (T). In equation form:
  P×V=n×R×TP \times V = n \times R \times TP×V=n×R×T
  Where:

  • P = pressure

  • V = volume

  • n = number of gas molecules

  • R = gas constant

  • T = temperature

• In the Context of Respiration:

  1. Inhalation:

     • When the diaphragm contracts and the thoracic cavity expands, the volume increases. According to Boyle’s Law, this leads to a decrease in pressure inside the lungs compared to atmospheric pressure. As a result, air flows into the lungs to equalize the pressure.

  2. Exhalation:

     • When the diaphragm relaxes and the thoracic cavity reduces in volume, the pressure inside the lungs increases. This leads to air being pushed out of the lungs towards the lower external pressure.

notes

Draw thoracic cage in breathing:

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VI. Respiratory Disorders

A. Emphysema

• Nature: Chronic and incurable disorder.

• Pathophysiology: The walls of the alveoli are damaged and distended, resulting in a reduction of surface area for gas exchange.

• Consequences: Less oxygen reaches vital organs like the heart and brain. As a result, the heart works overtime to pump blood to these areas, leading to heart strain.

B. Asthma

• Nature: Affects the bronchi and bronchioles.

• Pathophysiology: Smooth muscle around the bronchi and bronchioles undergoes spasms when exposed to irritants (e.g., allergens, cold air, smoke).

• Symptoms: Wheezing, breathlessness, and coughing.

• Treatment:

  • Inhalers: These contain bronchodilators, which dilate the smooth muscles of the bronchi and bronchioles, making it easier to breathe.

  • Corticosteroids: For chronic asthma, especially due to allergies, corticosteroids may be given to suppress the immune response, thus reducing inflammation and allergic reactions.