Respiration and the Respiratory System

Respiration

• Respiration is the process of breathing.
• It involves two phases:
  • Inspiration: Taking in oxygen
  • Expiration: Disposing of carbon dioxide

Function of the Respiratory System

• The respiratory system supplies the body with oxygen and removes carbon dioxide.
• This occurs through three main processes:
  • Pulmonary ventilation: Movement of air in and out of the lungs.
  • External respiration: Oxygen moves from the lungs to the blood, while carbon dioxide moves from the blood to the lungs.
  • Internal respiration: Oxygen moves from the blood to tissue cells, and carbon dioxide moves from tissue cells to the blood.

Respiratory System Structures

• The respiratory system includes:
  • Nose
  • Nasal cavity
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi and their branches
  • Lungs

Functional Divisions of the Respiratory System

• The respiratory system is divided into two functional zones:
  • Conducting zone: Carries air to the sites of gas exchange. This zone includes:
    • Nose
    • Nasal cavity
    • Pharynx
    • Larynx
    • Trachea
    • Bronchi
    • Bronchioles
    • Terminal bronchioles
  • Respiratory zone: The site of gas exchange. This zone includes:
    • Respiratory bronchioles
    • Alveolar ducts
    • Alveolar sacs
    • Alveoli

Nose

• Air entering the nose is filtered by hairs and moistened by mucus.
• Air can also enter the body through the mouth cavity.

Nasal Cavity

• Located above the oral cavity, separated by the hard palate.
• Filters, warms, and moistens air.

Para-Nasal Sinuses

• Functions:
  • Reduce skull weight
  • Provide resonance for voice
• Includes:
  • Maxillary sinus
  • Frontal sinus
  • Ethmoidal sinus
  • Sphenoidal sinus
• These sinuses open into the nasal cavity (meatuses).

Pharynx

• A muscular tube that continues with the esophagus.
• Divided into three parts:
  • Nasopharynx:
    • Contains the opening of the Eustachian (auditory) tube.
    • Contains the pharyngeal tonsil, which when inflamed is called an adenoid.
  • Oropharynx:
    • Common passage for air and food.
    • Lies behind the mouth cavity.
    • Contains the palatine tonsil on its lateral wall.
  • Laryngopharynx:
    • Lies behind the laryngeal cavity.

Larynx

• Connects the pharynx above with the trachea below.
• Functions:
  • Production of sound (voice box)
• Composed of:
  • Cartilages
  • Ligaments
  • Muscles
  • Mucous membrane

Air Flow - Larynx

• Air from the pharynx enters the larynx.
• The epiglottis prevents food from entering the larynx.

The Glottis

• The opening between the vocal cords.

Movements of Vocal Cords

• The vocal cords can move to produce sound and regulate airflow.

Trachea

• Held open by incomplete rings of hyaline cartilage (about 16-20).
• Divides at the level of the sternal angle (angle of Louis) T5 into the right and left main bronchus.
• Relations:
  • Anterior: Thyroid - isthmus and arch of aorta
  • Posterior: esophagus

Bronchi

• Trachea divides into main bronchi, which further divide into:
  • Lobar bronchi
  • Segmental bronchi
  • Bronchioles
  • Terminal bronchioles

Distal Respiratory Tract

• Includes bronchioles and alveoli.

Alveoli

• Small air sacs where gas exchange takes place.
• Surrounded by capillaries.

Lungs

• Located on each side of the heart, inside the chest cavity.
• Separated from each other by:
  • Heart and its large vessels
  • Trachea
  • Esophagus

Differences between the Right and Left Lungs

• Right lung:
  • Has three lobes (upper, middle, and lower)
  • Has two fissures (horizontal and oblique)
  • Short, wide, and has no cardiac notch
  • No lingula
• Left lung:
  • Has two lobes (upper and lower)
  • Has one fissure (oblique)
  • Long, thin, and has a cardiac notch
  • Has a lingula