Structure And Function Of The Lung Flashcards
What is the function of the respiratory system?
- to supply oxygen to all parts of the body via the heart
What are the conducting components?
- upper and lower respiratory tract
What are the respiratory components?
- respiratory bronchioles
- respiratory alveoli
- the diaphragm
What is in the upper respiratory tract?
- nose
- tongue
- larynx
- nasopharynx
- oropharynx
- laryngopharynx
- oesophagus
What is in the lower respiratory tract?
- right lung
- right bronchus
- trachea
- left lung
- left bronchus
What are the conducting airways responsible for?
- ventilation
- humidifcation & temperature regulation
- filtration and removal of particles
- antibacterial & immunologic defence
- sense of smell = from olfactory epithelium
- the production of sound
What is the bronchial tree made up of?
- trachea
- bronchi
- bronchioles
Primary bronchus = one away from the bronchus that is furtherst away from us on the page
What are the structure and function of the trachea?
Structure:
- 10cm long, 2.5cm wide
- divides into left and right bronchus
- kept open by 20 horse shoe cartiliginous rings, completed by tracheal is muscle
Function:
- flexibility in breathing
- allows back wall to bulge forward when coughing
What is the structure of the bronchus?
Left = longer than right = trachea at a more abrupt angle
Right = in line with trachea = more air is inhaled than the left
- tubes get smaller, cartilage gets irregular
- until the tubes are 1mm
- cartilage disappeares
- smooth muscle then gets thicker
What are examples of respiratory epithelium?
- pseudostratified columnar
- ciliated epithelium with secreting goblet cells
What is the structure of the epithelium?
- bronchi decrease in size = ciliated simple columnar
- then onto = simple cuboidal epithelium
- decrease in the number of goblet cells
- structural changes = gradual
- respiratory mucosa
- cilia
- mucus layer
- epithelium
- basement membrane
- lamina propria
What is mucociliary clearance?
- goblet cells secrete mucus = moistens air as it passes through respiratory tract
- traps fine particles of dust & bacteria that have escaped the nasal cavity
- epithelial cells = have ion channels = which regulates the thickness of airway surface liquid = where cilia bathe
- cilia beat upward
- foreign particles & mucus are sent to the base of the throat
- where they are swallowed or coughed out
What is the structure and function of the bronchioles?
Structure:
- less than 1mm
- no cartilage, thick smooth muscle maintains the structure
Function:
Muscle = responds to autonomic nerve stimulation
- wall extends to distal bronchiole, ciliated columnar membranous layer - to cuboidal shaped cells
- kept in an open state = radial traction of the surrounding fibres in the lung tissue
- walls retain elastic tension, allowing them to stay open
What do the bronchioles do during inspiration?
- distension of the air spaces
- elastic tension
What do the bronchioles do during expiration?
- passive
- recoil of elastic fibres in air spaces
Structure and function of the alveoli:
- gas exchange takes place
- spherical / polygonal air spaces
- thin walls surrounded by rich network of pulmonary capillaries
- bronchioles have alveoli
Where does the blood come from?
Carbon dioxide rich blood = deoxygenated
- right atrium
- right ventricle
- pulmonary artery
- goes to lungs
Oxygenated blood: oxygen rich:
- left atrium
- left ventricle
- to heart
- aorta to the rest of the body
What is perfusion?
The local flow of blood through a capillary bed of biological tissue
What is lung perfusion? What happens?
Pulmonary capillary network = very dense = large surface area for gas exchange
Pulmonary venues = oxygen rich = joins the pulmonary vein = empties into the left atriumm
What is the definition of breathing?
The physical movement of air between the outside environment and the lungs
What are the two phases of breathing?
- inspiration
- expiration
The gas percentages breathed in and out:
Nitrogen = 79% & 79%
Oxygen = 20% and 16%
Carbon dioxide = 0.04% and 4%
The process of inspiration:
- gases move from an area of high pressure to an area of low pressure
- the diaphragm contracts, lungs expand
- long volume increases
- pressure inside lungs decreases
- this is now lower than the outside pressure
- so air moves in
Process = negative pressure ventilation = active
What is Boyle’s Law?
Air pressure is inversely proportional to air volume
The process of expiration:
- inspiratory muscles release their contraction
- elastic recoil of lungs brings the tidal breathing cycle back to the starting point
- diaphragm and intercostal muscles relax
- the diaphragm & intercostal muscles move up to squeeze air out
- the ribs move down
- volume in the lungs decreases, pressure inside the lungs increases
- air moves out from a high to low pressure
What is neural control of breathing?
- autonomic nervous system effects a response
- involuntary
- breathing is controlled by inspiratory signals from the brain to the diaphragm
- flattens the diaphragm
- intercostal muscles are lifted
Chemical control of breathing - summarised:
- indirect control via detection of chemical changes in the blood
- during exercise
- to regulate breathing
- it is involuntary
For central neural control - where is the respiratory centre located in the brain?
Brain stem = medulla oblongata & pons
How does central neural control work?
- neurons send nerve signals to diaphragm & intercostal muscles
- regulates the rate and depth of breathing
What is unconscious activity needed for?
- oxygen and carbon dioxide exchange
- blood acid-base balance
What is voluntary control of ventilation?
- under control from cerebral cortex
- overruled by autonomic system in the event of a danger
How is the respiratory centre regulated? The process:
- regulated by oxygen, carbon dioxide and hydrogen ion content of the blood
- carbon dioxide and hydrogen ions are the most important
- increase in partial pressure carbon dioxide & h+ in the cerebral capillary across the blood brain barrier
- to the cerebrospinal fluid
- where carbon dioxide dissolves
CO2 + H2O -> H2CO3 -> H+ + HCO3-
- central chemoreceptors are sensitive to H+
- when stimulated, the rate & depth of respiration increases
- due to more carbon dioxide present
What are chemoreceptors?
- receptors that respond to changes in the chemical composition of body fluids
Give examples of peripheral chemoreceptors:
- respiratory centres in the brain
= monitor carbon dioxide and ph levels
= control the motor neurones to the intercostal muscles & diaphragm - chemoreceptors on the aorta and the carotid sinus of the carotid artery
= send information about chemical changes in the blood
= to respiratory centres in the brain stem
Examples of when peripheral chemoreceptors do that:
During exercise:
- muscles consume more oxygen
- oxygen levels in the blood fall
- carbon dioxide levels rise
Monitor blood acidity:
- concentration of H+ ions in the blood
Raised carbon dioxide:
- decreases blood ph
- due to increase in carbonic acid, which leads to more H+
- can also increase breathing rate if the partial pressure of oxygen drops down to below 60mmhg
The process of neural signalling to the lungs from the respiratory centre summarised:
- nervous impulses happen from the respiratory centre to the motor nerves
- they travel to the diaphragm via the = phrenic nerve
- they increase the breathing rate and volume of the lungs during inhalation
- pulls more oxygen into the body, increases expulsion of carbon dioxide so body gas levels go back to normal
- stretch receptors in the alveoli = detect inhalation, send inhibitory signals via the vagus nerve to the centre
- this causes exhalation
This is the = negative feedback system - Hering-Breuer Inflation Reflex
= prevents damage to lungs
