Respiratory System

Define respiration

Respiration is the entire process of gas exchange between the body cells and the atmosphere, involving the intake of oxygen and release of carbon dioxide

Steps of respiration/ main events of respiration

1. Pulmonary ventilation

2. External respiration

3. Transportation of gasses

4. Internal respiration

Organs of the respiratory system

Divided into 2 parts

1. Upper Respiratory Tract (URT)

2. Lower Respiratory Tract (LRT)

Organs of upper respiratory tract

• Nose

• Nasal cavity

• Paranasal sinuses

• Pharynx

Organs of lower respiratory tract

• Larynx

• Trachea

• Bronchial tree

• Lungs

Passage of air through the respiratory system

Nose → Nasal cavity → Pharynx → Larynx → Trachea → Bronchioles → Lungs → Alveoli

Nose (external nose and nasal cavity)

• The nose is the only externally visible part of the respiratory system

• The nose is covered with skin and is supported internally by muscle, bone, and cartilage

• Its two nostrils provide openings through which air can enter and leave the nasal cavity

• Many internal hairs in these openings prevent entry of large particles carried in the air

Functions of nose

• provides an airway for respiration,

• moistens and warms entering air,

• filters and cleans inspired air,

• houses the olfactory (smell) receptors

Paranasal sinuses

• The paranasal sinuses are air filled spaces within the frontal, ethmoid, sphenoid, and maxillary bones of the skull that open into the nasal cavity

• Mucous membranes line the sinuses and are continuous with the lining of the nasal cavity

Functions of paranasal sinuses

• The paranasal sinuses reduce the weight of the skull and are resonant chambers that affect the quality of the voice

Pharynx

• Passageway connecting nasal cavity to larynx and oral cavity to esophagus

• Three subdivisions nasopharynx, oropharynx, and laryngopharynx (also known as hypopharynx)

• Houses tonsils (lymphoid tissue masses involved in protection against pathogens)

Functions of pharynx

• It is a passageway for food moving from the oral cavity to the esophagus and for air passing between the nasal cavity and the larynx

• The pharynx also helps produce the sounds of speech

Larynx

• Connects pharynx to trachea

• Has framework of cartilage and dense connective tissue

• Houses vocal cords

Functions of larynx

• Air passageway

• Prevents food from entering lower respiratory tract

• Voice production

Trachea

• Also known as windpipe

• Flexible tube running from larynx and dividing inferiorly into two main bronchi

Functions of trachea

• Air passageway

• Cleans, warms, and moistens incoming air

Bronchial tree

The bronchial tree consists of branched airways leading from the trachea to the microscopic air sacs in the lungs. Its branches begin with the right and left primary bronchi

Divisions of the branches

1. Right and left pulmonary bronchi

2. Secondary bronchi

3. Tertiary bronchi

4. Intralobular bronchioles

5. Terminal bronchioles

6. Respiratory bronchioles

7. Alveolar ducts

8. Alveolar sacs

9. Alveoli

Secondary bronchi

Three branch from the right primary bronchus, and two branch from the left

Tertiary bronchi

Each of these branches supplies a portion of the lung called a bronchopulmonary segment.
Usually ten such segments are in the right lung and eight are in the left lung

Intralobular bronchules

The small branches of the segmental bronchi enter the basic units of the lung - the lobules

Terminal bronchioles

The tubes branch from an intralobular bronchiole. Fifty to eighty terminal bronchioles occupy a lobule of the lung

Respiratory bronchioles

Two or more respiratory bronchioles branch from each terminal bronchiole. Short and about 0.5 mm in diameter, these structures are called “respiratory” because a few air sacs bud from their sides, enabling them to take part in gas exchange

Alveolar ducts

Alveolar ducts branch from each respiratory bronchiole

Alveolar sacs

Alveolar sacs are thin walled, closely packed outpouchings of the alveolar ducts

Alveoli

Alveoli are thin walled, microscopic air sacs that open to an alveolar sac. Air can diffuse freely from the alveolar ducts, through the alveolar sacs, and into the alveoli

Functions of bronchial tree

• Air passageways connecting trachea with alveoli

• Cleans, warms, and moistens incoming air

Lung

The lungs are soft, spongy, cone shaped organs in the thoracic cavity. It is composed primarily of alveoli and respiratory passageways

Functions of lungs

House respiratory passages

Define hypoxia

Hypoxia is a condition characterized by deficiency of oxygen in the body tissue/body cell and/or reduced utilization of oxygen at cellular level

Classification of hypoxia

1. Anemic hypoxia

2. Ischemic (stagnant) hypoxia

3. Histotoxic hypoxia

4. Hypoxemic (Hypoxic) hypoxia

Anemic hypoxia

Anemic hypoxia reflects poor oxygen delivery resulting from too few RBCs or from RBCs that contain abnormal or too little Hb

Ischemic (stagnant) hypoxia

• Ischemic (stagnant) hypoxia results from impaired or blocked blood circulation

• Congestive heart failure may cause ischemic hypoxia throughout the body, whereas emboli or a blood clot block oxygen delivery only to tissues distal to the obstruction

Histotoxic hypoxia

• Histotoxic hypoxia occurs when body cells are unable to use O2 even though adequate amounts are delivered

• Alcohol, narcotics, and cyanide are three primary factors that can cause histotoxic hypoxia

Hypoxemic (Hypoxic) hypoxia

• Is the most common and is caused by decreased oxygen in air or the inability to diffuse the oxygen across the lungs

• Possible causes include disordered or abnormal ventilation-perfusion coupling, pulmonary diseases that impair ventilation, and breathing air containing little amounts of O2

What is breathing?

Breathing, or ventilation, is the movement of air from outside the body first into and then out of the bronchial tree and alveoli.

Inspiration or inhalation

The intake of air into the lungs through expansion of chest volume.

Expiration or exhalation

The expulsion of air from the lungs through contraction of chest volume.

Inhalation mechanism

Diaphragm → contracted → ↑ Thoracic cavity → ↑Lung expansion → inhalation

Intercostal muscle → contracted → ↑ Thoracic cavity → ↑Lung expansion → inhalation

Exhalation mechanism

Diaphragm → relaxed → ↓ Thoracic cavity → Lung contraction → inhalation

Intercostal muscle → relaxed → ↓ Thoracic cavity → Lung contraction → inhalation

Respiratiory cycle

One inspiration plus the following expiration is called a respiratory cycle.

Respiratory volumes

1. Tidal volume (TV): It is the amount of air that can be inhaled or exhaled during one normal (resting condition) breathing cycle.

2. Inspiratory reserve volume (IRV): It is the amount of air that can be forcibly inhaled beyond a tidal inhalation.

3. Expiratory reserve volume (ERV): It is the amount of air that can be forcibly exhaled beyond a tidal exhalation.

4. Residual volume (RV): It is the amount of air remaining in the lungs after an ERV

Respiratory air volume and capacities

1. Inspiratory capacity (IC): Maximum volume of air a person can inhale following a resting expiration. [IC = TV + IRV]

2. Functional residual capacity (FRC): Volume of air remaining in the lungs following a resting expiration. [FRC = ERV + RV]

3. Vital capacity (VC): Maximum amount of air that can be expired after a maximum inspiratory effort. [VC = TV + IRV + ERV]

4. Total lung capacity (TLC): The volume of air in the lungs after a maximum inspiratory effort. [TLC = TV + IRV + ERV + RV]

Minute ventilation

The volume of new atmospheric air moved into the respiratory passages each minute is called the minute ventilation

Minute Ventilation (MV) = Tidal Volume × Breathing Rate

Respiratory membrane is composed of-

• simple squamous epithelium lining the alveoli,

• the endothelium of the pulmonary capillary walls, and

• their fused basement membranes.