The Respiratory System (Part 1): Structure and Function Flashcards
Why Do We Breathe?
- Respiratory system creates an interface between the environment and the tissues (via the blood) for gas exchange
Key Definitions
1) Ventilation: movement of air into and out of lungs
(i.e., breathing)
2) Physiological respiration: diffusion of gases across
plasma membranes; two types:
- External (pulmonary) respiration: gas exchange between air in lungs and blood (includes ventilation)
- Internal (systemic) respiration: gas exchange between the blood and body cells
3) Cellular respiration: chemical reactions that break down glucose to produce ATP for use as energy
Non-respiratory Functions
Functions in addition to ventilation and respiration:
1) Olfaction: Smell occurs when airborne molecules are drawn into nasal cavity
2) Phonation: Movement of air past vocal folds makes sound and speech
3) Protection: Against microorganisms by preventing entry and removing them from respiratory surfaces (mucus layer, cough, sneeze)
4) Production of chemical mediators: ACE, an enzyme involved in blood pressure regulation
5) Acid-base balance (+ renal system): Blood pH is altered by changing blood carbon dioxide levels
Anatomy of the Respiratory System
1) Nose
2) Nasal cavity
3) Pharynx
4) Larynx
5) Trachea
6) Bronchus
7) Bronchiole
8) Alveoli
Nasal Cavity and Pharynx
Nasal cavity:
- Air passageway
- Cleans, warms and
humidifies inspired air
- Contains olfactory
epithelium for sense of
smell (not shown)
- Resonating chambers
for speech (alongside
paranasal sinuses)
Pharynx:
- Common opening for
respiratory and digestive systems
Larynx
1) Passes air from the throat to the lungs.
2) Produces sound using vocal cords.
3) Protects the airway by preventing food from entering the trachea during swallowing
Vocal Folds
1) Produce sound by vibrating as air passes through.
2) Control airflow by opening during breathing and closing during swallowing or speech.
3) Protect the airway by preventing food or liquids from entering the trachea.
Trachea
1) Carries air between the larynx and lungs.
2) Filters air using mucus and cilia to trap dust and germs.
3) Keeps airway open with its strong, flexible structure.
Beating Cilia
1) Move mucus upward toward the throat.
2) Clear dust, germs, and debris from the airways.
3) Protect lungs by keeping them clean
Mucus Flakes and Cilia
1) Mucus flakes trap dust, germs, and other particles.
2) Cilia beat rhythmically to move the mucus up and out of the airways.
3) Together, they clean and protect the respiratory system
Tracheobronchial Tree
1) Carries air from the trachea into the lungs.
2) Branches into bronchi and bronchioles to reach all parts of the lungs.
3) Distributes and filters air, helping with efficient gas exchange
Bronchioles and Alveoli
Bronchioles:
1) Carry air from the bronchi to the alveoli.
2) Control airflow with smooth muscles that can widen or narrow.
3) Help distribute air evenly in the lungs.
Alveoli:
1) Tiny air sacs where gas exchange happens.
2) Oxygen enters the blood, and carbon dioxide leaves.
3) Surrounded by capillaries for efficient gas exchange
Inter-alveolar and Inter-bronchiolar Connections
Inter-Alveolar Connections:
1) Link adjacent alveoli to allow airflow between them.
2) Help equalize pressure and improve gas exchange.
Inter-Bronchiolar Connections:
1) Connect bronchioles to improve airflow distribution.
2) Provide backup pathways for air if one is blocked.
Alveolus and the Respiratory Membrane
Alveolus:
1) Tiny air sac where gas exchange occurs.
2) Oxygen enters the blood, and carbon dioxide is removed.
Respiratory Membrane:
1) Thin barrier between alveolus and capillary.
2) Facilitates gas exchange by allowing oxygen and carbon dioxide to pass easily
Alveolar Structure
1) Type I cells – incredibly thin (like fried eggs) – cover ~95% of alveolar surface –
involved in gas exchange
2) Type II cells – greater numbers than Type I cells, but only cover ~5% of alveolar surface – produce surfactant (reduces surface tension on alveoli, preventing them from collapse)
Thoracic Cavity and Respiratory Muscles
- Thoracic cavity is the space enclosed by the thoracic wall and the diaphragm
- Respiratory muscles change volume of thoracic cavity during ventilation
Thoracic Skeleton
1) Consists of ribs, sternum, and thoracic vertebrae.
2) Protects vital organs like the heart and lungs.
3) Supports breathing by aiding in the expansion and contraction of the chest.
Ribs
- True ribs (7)
- False (3)
- Floating (2)
Effect of Rib and Sternum Movement on Thoracic Volume
- Rib movement: During inhalation, ribs move up and out, increasing thoracic volume; during exhalation, they move down and in, decreasing volume.
- Sternum movement: The sternum moves forward and upward during inhalation, further expanding thoracic volume, and downward during exhalation, reducing volume
Diaphragm
- Thoracic volume is increased by diaphragm contraction (lowers dome)
- A muscular sheet that separates the thoracic cavity from the abdominal cavity.
- Plays a key role in breathing: during inhalation, it contracts and moves down, increasing thoracic volume; during exhalation, it relaxes and moves up, decreasing thoracic volume.
- This movement helps draw air into the lungs and push air out during breathing.
Intercostal Muscles
- Located between the ribs, these muscles help with breathing.
- The external intercostals contract during inhalation, lifting the ribs and expanding the chest.
- The internal intercostals contract during exhalation, pulling the ribs downward to reduce chest volume.
Accessory Inspiratory Muscles
- Pectoralis major:
1) A large chest muscle that can assist in forced inhalation.
2) When the arms are fixed, it lifts the ribcage to expand the thoracic cavity
- Pectoralis minor:
1) Located underneath the pectoralis major, it elevates the ribs during deep inhalation, aiding in expanding the chest - Sternocleidomastoid:
1) A neck muscle that helps with forced inhalation.
2) When contracted, it lifts the sternum and clavicle, increasing thoracic volume
- Scalenes:
1) A group of muscles in the neck that assist in elevating the first two ribs during deep inhalation, increasing thoracic cavity space
Mechanisms of Inspiration and Expiration
Quiet inspiration:
- Diaphragm
Deep inspiration:
- Diaphragm, external
intercostals, parasternal
intercostals
Deepest inspiration:
- Scalenes, sternocleidomastoids, serratus anterior, pectoralis major and minor
- Potentially others
Quiet expiration (passive):
- Elastic recoil of lungs
- Relaxation of diaphragm
Forced expiration:
- Abdominals
- Internal intercostals
- Potentially others
Lungs
- Primary organs of
respiratory system - Right lung: 3 lobes
separated by fissures - Left lung: 2 lobes and
an indentation called
the cardiac notch - Mediastinum: central
region, contains
contents of thoracic
cavity except for lungs
