BIO 252 Anatomy and Physiology Module 5
AP 5 – Respiratory Center
5.1 – Functional Anatomy of the Respiratory System
Primary Functions of the Respiratory System
● Supplies O2 for aerobic metabolism (ATP production)
● Removes CO2, a metabolic waste
● Helps regulate acid-base balancer
● Enables speech, olfaction, and protective reflexes (coughing, sneezing, Valsalva)
● Breathing is largely automatic, controlled by autonomic nervous system due to the constant
cellular oxygen demand
Anatomical Organization
● Upper Respiratory System
○ Nose
○ Nasal cavity
○ Sinuses
○ Pharynx
○ (sometimes larynx depending on source)
● Lower Respiratory System
○ Larynx
○ Trachea
○ Bronchi
○ Bronchioles
○ Lungs
○ Alveoli
Key Structures and Functions
● Nasal Cavity
○ Warms, humidifies, and filters incoming air
○ Mucous membranes trap dust and microbes
○ Rich blood supply helps warm air
○ Contain olfactory epithelium for smell
● Pharynx
○ Shared pathway for air and food
○ Directs air to larynx and food to esophagus
, ● Larynx (voice box)
○ Keeps airway open
○ Routes air and food correctly
○ Produces sound
○ Epiglottis
■ Moveable flap
■ Prevents food/liquid from entering trachea during swallowing
○ Glottis
■ Includes
● Vestibular folds (false vocal cords)
● Vocal folds (true vocal cords)
● Space between them (rima glottidis)
■ Functions in breathing, sound production, and airway protecting
○ Voice production
■ Sound → vibration of vocal cords
■ Pitch depends on vocal cord length and tension
■ Volume depends on airflow
○ Valsalva Maneuver
■ Forced expiration with closed glottis
■ Increases intra-abdominal pressure
■ Used during defecation, childbirth, heavy lifting
● Trachea
○ Supported by C-shaped hyaline cartilage rings
○ Keeps airway open
○ Lined with ciliated epithelium
○ Cilia move mucus upward toward pharynx
● Bronci and Bronchioles
○ Trachea → right and left primary bronchi
○ Branch repeatedly into smaller bronchi → bronchioles
○ Bronchioles lack cartilage
○ Diameter controlled by smooth muscle
○ Autonomic control
■ Parasympathetic → bronchoconstriction
■ Sympathetic → bronchodilation
■ Histamine → bronchoconstriction (allergic response)
● Asthma = excessive bronchoconstriction
Respiratory Zones
● Conducting Zone
, ○ Purpose– move, warm, humidify, and clean air
○ Includes
■ Nasal cavity
■ Pharynx
■ Larynx
■ Trachea ■
Bronchi
■ Terminal bronchioles
○ No gas exchange
● Respiratory Zone
○ Purpose– gas exchange ○ Includes
■ Respiratory
bronchioles
■ Alveolar ducts
■ Alveolar sacs
■ Alveoli
Respiratory Epithelium
● Pseudostratified ciliated columnar epithelium
● Contains
○ Goblet cells → secrete mucus
○ Cilia → move mucus toward pharynx
● Produces lysozyme and defensins (antibacterial)
● Humidification is essential to…
○ Prevent drying
○ Maintain ciliary function
○ Reduce complications in ventilated patients
Alveoli and Gas Exchange
● Alveolus– single air sac
● Alveolar sac– cluster of alveoli
● Alveolar ducts– lead into sacs
● Alveolar pores– equalize air pressure between alveoli
● Thin elastic walls allow expansion
Cells of the Alveoli
● Type 1 Alveolar Cells
○ Simple squamous epithelial cells
○ ~ 97% of alveolar surface
○ Extremely thin (~ 0.25 um)
, ○ Primary site of gas diffusion
● Type 2 Alveolar Cells
○ Cudoidal cells
○ Secrete pulmonary surfactant
○ Surfactant reduces surface tension → prevents alveolar collapse
○ Deficiency → respiratory distress syndrome (RDS) in premature infants
● Alveolar Macrophages
○ Immune cells
○ Remove debris and pathogens
Respiratory
Membrane ●
Formed by:
○ Type 1 Alveolar cell
○ Fused basement membrane
○ Capillary endothelium
● Thickness ~ 0.5 um
● Allows simple diffusion of O2 and CO2
● Creates an air-blood barrier
Respiratory Muscles
● Primary Respiratory Muscles
○ Diaphragm
■ Contracts → flattens → inspiration
■ Relaxes → expiration
○ External intercostals
■ Elevate ribs during inspiration
● Accessory Respiratory Muscles
○ Used during exercise or respiratory distress
○ Includes
■ Sternocleidomastoid
■ Scalenes
■ Pectoralis minor
■ Serratus anterior
■ Internal intercostals
■ Abdominal muscles (forced expiration)
Pleura and Pleural Cavity
● Visceral pleura → covers lungs
● Parietal pleura → lines chest wall ● Pleural cavity
AP 5 – Respiratory Center
5.1 – Functional Anatomy of the Respiratory System
Primary Functions of the Respiratory System
● Supplies O2 for aerobic metabolism (ATP production)
● Removes CO2, a metabolic waste
● Helps regulate acid-base balancer
● Enables speech, olfaction, and protective reflexes (coughing, sneezing, Valsalva)
● Breathing is largely automatic, controlled by autonomic nervous system due to the constant
cellular oxygen demand
Anatomical Organization
● Upper Respiratory System
○ Nose
○ Nasal cavity
○ Sinuses
○ Pharynx
○ (sometimes larynx depending on source)
● Lower Respiratory System
○ Larynx
○ Trachea
○ Bronchi
○ Bronchioles
○ Lungs
○ Alveoli
Key Structures and Functions
● Nasal Cavity
○ Warms, humidifies, and filters incoming air
○ Mucous membranes trap dust and microbes
○ Rich blood supply helps warm air
○ Contain olfactory epithelium for smell
● Pharynx
○ Shared pathway for air and food
○ Directs air to larynx and food to esophagus
, ● Larynx (voice box)
○ Keeps airway open
○ Routes air and food correctly
○ Produces sound
○ Epiglottis
■ Moveable flap
■ Prevents food/liquid from entering trachea during swallowing
○ Glottis
■ Includes
● Vestibular folds (false vocal cords)
● Vocal folds (true vocal cords)
● Space between them (rima glottidis)
■ Functions in breathing, sound production, and airway protecting
○ Voice production
■ Sound → vibration of vocal cords
■ Pitch depends on vocal cord length and tension
■ Volume depends on airflow
○ Valsalva Maneuver
■ Forced expiration with closed glottis
■ Increases intra-abdominal pressure
■ Used during defecation, childbirth, heavy lifting
● Trachea
○ Supported by C-shaped hyaline cartilage rings
○ Keeps airway open
○ Lined with ciliated epithelium
○ Cilia move mucus upward toward pharynx
● Bronci and Bronchioles
○ Trachea → right and left primary bronchi
○ Branch repeatedly into smaller bronchi → bronchioles
○ Bronchioles lack cartilage
○ Diameter controlled by smooth muscle
○ Autonomic control
■ Parasympathetic → bronchoconstriction
■ Sympathetic → bronchodilation
■ Histamine → bronchoconstriction (allergic response)
● Asthma = excessive bronchoconstriction
Respiratory Zones
● Conducting Zone
, ○ Purpose– move, warm, humidify, and clean air
○ Includes
■ Nasal cavity
■ Pharynx
■ Larynx
■ Trachea ■
Bronchi
■ Terminal bronchioles
○ No gas exchange
● Respiratory Zone
○ Purpose– gas exchange ○ Includes
■ Respiratory
bronchioles
■ Alveolar ducts
■ Alveolar sacs
■ Alveoli
Respiratory Epithelium
● Pseudostratified ciliated columnar epithelium
● Contains
○ Goblet cells → secrete mucus
○ Cilia → move mucus toward pharynx
● Produces lysozyme and defensins (antibacterial)
● Humidification is essential to…
○ Prevent drying
○ Maintain ciliary function
○ Reduce complications in ventilated patients
Alveoli and Gas Exchange
● Alveolus– single air sac
● Alveolar sac– cluster of alveoli
● Alveolar ducts– lead into sacs
● Alveolar pores– equalize air pressure between alveoli
● Thin elastic walls allow expansion
Cells of the Alveoli
● Type 1 Alveolar Cells
○ Simple squamous epithelial cells
○ ~ 97% of alveolar surface
○ Extremely thin (~ 0.25 um)
, ○ Primary site of gas diffusion
● Type 2 Alveolar Cells
○ Cudoidal cells
○ Secrete pulmonary surfactant
○ Surfactant reduces surface tension → prevents alveolar collapse
○ Deficiency → respiratory distress syndrome (RDS) in premature infants
● Alveolar Macrophages
○ Immune cells
○ Remove debris and pathogens
Respiratory
Membrane ●
Formed by:
○ Type 1 Alveolar cell
○ Fused basement membrane
○ Capillary endothelium
● Thickness ~ 0.5 um
● Allows simple diffusion of O2 and CO2
● Creates an air-blood barrier
Respiratory Muscles
● Primary Respiratory Muscles
○ Diaphragm
■ Contracts → flattens → inspiration
■ Relaxes → expiration
○ External intercostals
■ Elevate ribs during inspiration
● Accessory Respiratory Muscles
○ Used during exercise or respiratory distress
○ Includes
■ Sternocleidomastoid
■ Scalenes
■ Pectoralis minor
■ Serratus anterior
■ Internal intercostals
■ Abdominal muscles (forced expiration)
Pleura and Pleural Cavity
● Visceral pleura → covers lungs
● Parietal pleura → lines chest wall ● Pleural cavity
