Respiratory Physiology Summary Notes for Dentistry (Year 1)
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Course
Biomedicine in Relation to Dentistry (4NNYBD01)
Institution
Kings College London (KCL)
Concise and easy to access notes on the physiology of the respiratory system for first year dental students.
Covers lung volumes & capacities, ventilation rates, respiratory tract anatomy, alveoli, respiratory vasculature & lymphatics, lung mechanics, gas laws & partial pressure, oxygen & carbon ...
Respiratory System Basics
Lung Volumes
Alveoli
• Tidal Volume (VT) 500ml - volume of air
• 300x106 alveoli moving in/out of lungs
• Diameter ~0.2mm, membrane SA ~0.4m
• Inspiration Reserve Volume (IRV) 3000ml -
• Surface covered with moist alveolar lining volume of air inspired with maximal effort
• Expiratory Reserve Volume (ERV) 1200ml
Lung Capacities - volume of air expired with maximal effort
• Inspiratory Capacity (IC) 3500ml • Residual Volume (RV) 1200ml - volume of
= VT + IRV air remaining in lungs after ERV
• Vital Capacity (VC) 4700ml
= IRV + VT + ERV Spirometers
• Functional Residual Capacity (FRC) 2400ml • Inspiration → pen moves up, expiration →
= ERV + RV pen moves down
• Total Lung Capacity (TLC) 5900ml • Cannot measure RV, hence cannot measure
= VT + IRV + ERV + RV FRC or TLC
Inspiration
At FRC:
• Alveolar pressure (PA)
=0
• IPP = -ve
1. Chest expands
2. IPP becomes more -ve
3. Increased outward
force across alveoli
4. Alveoli expand
5. PA falls
6. Pmouth > Palveoli
7. Air flows to alveoli
until pressure returns to
zero
Ventilation Rates
• Resting respiratory frequency ~15 breaths per Resting Position at FRC
min • All respiratory muscles relaxed, but
• Minute Ventilation (VE) = Respiratory rate x lungs recoil inwards and chest recoils
Tidal Volume (total ventilation per min) outwards
• Alveolar Ventilation (VA) = volume of • Opposing recoils → slight negative
FRESH air reaching alveoli per min pressure between pleural membranes
• VA differs from VE due to anatomical dead (intrapleural pressure, PIP/IPP)
space: VA = VE - Anatomical dead space
ventilation
Dead Spaces
• Air that is inhaled but not used in gas
Pressure During Breathing exchange
• Quiet breathing: PIP always -ve, but • Anatomical Dead Space = volume of
inspiration is more -ve than expiration pharynx and conducting zone (150ml)
• Forced expiration: PIP is +ve • Alveolar Dead Space = volume of air in
• PA: inspiration = -ve, expiration = +ve, in non-functional alveoli
between = 0 • Physiological Dead Space = anatomical
• PA always more +ve than PIP dead space + alveolar dead space
, Respiratory Tract Anatomy
Respiratory Tract Respiratory Epithelium
Upper • Lines much of upper respiratory tract &
• Nasal cavity conducting zone (but NOT alveoli)
• Paranasal sinuses • Pseudostratified, columnar, ciliated
• Nasopharynx epithelium with goblet cells
Lower • Goblet Cells → mucus, which traps dust
• Larynx (aided by submucosal glands)
Conducting Zone
• Trachea – no gas exchange
• Cilia: beat to propel mucus to pharynx
• Bronchi (1/2/3)
• Terminal bronchioles Cilia structure: 20 microtubules (9
• Respiratory bronchioles Respiratory Zone doublets + central pair), 7-10m
• Alveolar ducts –gas exchange
• Alveolar sacs Bronchioles
• Columnar → cuboidal ciliated cells in
respiratory epithelium
Conducting Zone
• Discrete bundles of smooth muscle
From trachea → terminal bronchioles
• No cartilage or submucosal glands + fewer
• Tall columnar → cuboidal epithelium
goblet cells than bronchi
• No smooth muscle → complete smooth
muscle layer → discrete bundles
• Many submucosal glands → none Terminal Bronchioles
• Many goblet cells → none • Cuboidal ciliated respiratory epithelium
• No Clara cells → Clara cells present • No goblet cells, rather Clara cells → secrete
components of surfactant and pumps Cl-
Trachea
• Very tall respiratory epithelium
• Highly cellular/vascular lamina propria + rich
in elastin
• Submucosa contains mucoserous glands
• C-shaped cartilage rings, prevent collapse
• Contraction of trachealis → reduced diameter
→ intrathoracic pressure
Primary Bronchus
• Shorter respiratory epithelium & fewer goblet
cells compared to trachea
• Discontinuous smooth muscle layer secretes
lamina propria & submucosa Respiratory Bronchioles
• No C-shaped rings – plates of cartilage • Minimal gas exchange: single alveoli in
instead walls
• Branch into individual alveoli/alveolar
ducts
Tertiary Bronchus
• Tall, columnar respiratory epithelium with
little pseudostratification Alveolar Ducts/Sacs
• Complete layer of smooth muscle below • Supported by smooth muscle cells, collagen
lamina propria (contraction by PNS) & elastin
• Fewer goblet cells and fewer mucoserous • ~50 alveoli per sac
glands than trachea • Site of most gas exchange with extensive
• Irregular cartilage plates blood supply / capillary network
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