Summary
Summary Respiratory System APES1001 MBBCH I
- Course
- APES1001A (APES1001)
- Institution
- University Of The Witwatersrand (wits)
Summary of Respiratory System lecture notes for APES1001 MBBCH I
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RESPIRATORY SYSTEM,Lesson 1 - Overview of the Respiratory System
Main function: to exchange CO2 and O2 between the body and the external environment
Gaseous exchange occurs in the respiratory division of the lungs
Nose → pharynx → larynx → trachea → bronchi → bronchioles (passageways for air to pass
in and out and known as conducting division)
Nasal cavity is lined with a ciliated mucous membrane → sticky mucous traps inhaled
particles + beating of cilia drives mucous to throat to be swallowed
Bacteria that are inhaled are destroyed by lysozymes in the mucous + lymphocytes +
antibodies
3 folds of tissue arising from wall of nasal cavity (nasal conchae/turbinate’s) → increase
contact surface with inhaled air enabling nose to rapidly warm, moisten and cleanse it.
Roof of nasal lining has olfactory nerve cells which bring sense of smell
The inhaled air moves at a 90-degree angle down as soon as it reaches the pharynx. Also,
another method of trapping large particles, that due to their inertia, crash and stick to the
wall of the throat and stick to mucosa.
Pharynx has several tonsils (immune competent) + pharynx also passes food down the
oesophagus
In order to prevent food from going down the wrong pipe, the larynx is covered by a flap
called the epiglottis. During swallowing, the larynx is pulled up and the flap flips over,
directing food and drink to oesophagus.
Vocal folds are closed protecting airway. From the larynx, air passes to trachea.
The bronchi split into multiple bronchi until making bronchioles (smooth muscles allow to
constrict (to decrease air flow) /dilate (to increase air flow)
Larynx, trachea, bronchiole tree are lined by ciliated columnar epithelium which act as
mucocillary escalator (mucous traps dust and moves up into throat to get swallowed).
Terminal bronchioles → branch into respiratory bronchioles begins which mark beginning of
respiratory division
The terminal bronchioles ned with alveoli. These are surrounded by blood capillaries where
gaseous exchange occurs. The Alveoli is surrounded by a Type I squamous cells which allows
rapid diffusion.
Type II (cuboidal cell) acts as surfactant to lower ST at air-liquid interface + prevents alveolus
from exploding ate need of each exhalation.
Alveoli have macrophage so as to dissolve any unwanted large particles
Macrophages ride the mucocillary escalator so they can be digested.
, Specialized respiratory surfaces
Conducting zone
nose/mouth → pharynx –> larynx → trachea → primary bronchus → bronchi → bronchioles
- no gaseous exchange
- contribute to anatomical space
- act as pathway for air
Functions:
1. warm and humidify the air
2. filter air via cilia (move particles) + mucous (trap particles) and the mucocillary
escalator (expel particles)
As air moves down our trachea, low resistance of air flow, because trachea is open by
cartilaginous rings.
The air then moves into 2 bronchi, one to each lung. Bronchi has cartilaginous rings to keep
them open. When we don’t have the cartilaginous rings, we term them bronchioles.
Bronchioles form bronchiole tree. Further split into terminal bronchioles (16000)
Respiratory zone
As air flows down terminal bronchioles, they will branch again into respiratory bronchioles
(500 000)
Respiratory bronchioles have tiny air sacs (alveolar sacs – 8 million) where gaseous exchange
takes place. The alveoli form the start of the respiratory zone.
Respiratory bronchioles split into alveolar sacs which are made by individual alveoli (singular:
alveolus – 300 million) bunched together.
The alveoli increase the surface area of the lungs to facilitate gaseous exchange.
Alveoli + Blood vessels
In order for gaseous exchange to occur, alveoli need to be associated with a blood supply.
Around each alveoli air sac, is a capillary bed.
Branch of pulmonary artery does not thick muscles to lower the pressure with which blood
flows to the lungs. The pulmonary artery carriers deoxygenated blood down the artery into
arterioles into small capillaries which surround the
alveolar sacs.
In capillary beds, O2 is picked up and CO2 is offloaded.
The oxygenated blood is then collected via the
pulmonary vein and returned to the heart to pump to the
rest of the body.
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