Structure And Function Of The Lung

Question 1

What is the function of the respiratory system?

Answer 1

• to supply oxygen to all parts of the body via the heart

Question 2

What are the conducting components?

Answer 2

• upper and lower respiratory tract

Question 3

What are the respiratory components?

Answer 3

• respiratory bronchioles
• respiratory alveoli
• the diaphragm

Question 4

What is in the upper respiratory tract?

Answer 4

• nose
• tongue
• larynx
• nasopharynx
• oropharynx
• laryngopharynx
• oesophagus

Question 5

What is in the lower respiratory tract?

Answer 5

• right lung
• right bronchus
• trachea
• left lung
• left bronchus

Question 6

What are the conducting airways responsible for?

Answer 6

• ventilation
• humidifcation & temperature regulation
• filtration and removal of particles
• antibacterial & immunologic defence
• sense of smell = from olfactory epithelium
• the production of sound

Question 7

What is the bronchial tree made up of?

Answer 7

• trachea
• bronchi
• bronchioles

Primary bronchus = one away from the bronchus that is furtherst away from us on the page

Question 8

What are the structure and function of the trachea?

Answer 8

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

Question 9

What is the structure of the bronchus?

Answer 9

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

Question 10

What are examples of respiratory epithelium?

Answer 10

• pseudostratified columnar
• ciliated epithelium with secreting goblet cells

Question 11

What is the structure of the epithelium?

Answer 11

• 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

Question 12

What is mucociliary clearance?

Answer 12

• 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

Question 13

What is the structure and function of the bronchioles?

Answer 13

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

Question 14

What do the bronchioles do during inspiration?

Answer 14

• distension of the air spaces
• elastic tension

Question 15

What do the bronchioles do during expiration?

Answer 15

• passive
• recoil of elastic fibres in air spaces

Question 16

Structure and function of the alveoli:

Answer 16

• gas exchange takes place
• spherical / polygonal air spaces
• thin walls surrounded by rich network of pulmonary capillaries
• bronchioles have alveoli

Question 17

Where does the blood come from?

Answer 17

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

Question 18

What is perfusion?

Answer 18

The local flow of blood through a capillary bed of biological tissue

Question 19

What is lung perfusion? What happens?

Answer 19

Pulmonary capillary network = very dense = large surface area for gas exchange

Pulmonary venues = oxygen rich = joins the pulmonary vein = empties into the left atriumm

Question 20

What is the definition of breathing?

Answer 20

The physical movement of air between the outside environment and the lungs

Question 21

What are the two phases of breathing?

Answer 21

• inspiration
• expiration

Question 22

The gas percentages breathed in and out:

Answer 22

Nitrogen = 79% & 79%
Oxygen = 20% and 16%
Carbon dioxide = 0.04% and 4%

Question 23

The process of inspiration:

Answer 23

• 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

Question 24

What is Boyle’s Law?

Answer 24

Air pressure is inversely proportional to air volume

Question 25

The process of expiration:

Answer 25

- 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

Question 26

What is neural control of breathing?

Answer 26

- 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

Question 27

Chemical control of breathing - summarised:

Answer 27

- indirect control via detection of chemical changes in the blood - during exercise - to regulate breathing - it is involuntary

Question 28

For central neural control - where is the respiratory centre located in the brain?

Answer 28

Brain stem = medulla oblongata & pons

Question 29

How does central neural control work?

Answer 29

- neurons send nerve signals to diaphragm & intercostal muscles - regulates the rate and depth of breathing

Question 30

What is unconscious activity needed for?

Answer 30

- oxygen and carbon dioxide exchange - blood acid-base balance

Question 31

What is voluntary control of ventilation?

Answer 31

- under control from cerebral cortex - overruled by autonomic system in the event of a danger

Question 32

How is the respiratory centre regulated? The process:

Answer 32

- 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

Question 33

What are chemoreceptors?

Answer 33

- receptors that respond to changes in the chemical composition of body fluids

Question 34

Give examples of peripheral chemoreceptors:

Answer 34

- 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

Question 35

Examples of when peripheral chemoreceptors do that:

Answer 35

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

Question 36

The process of neural signalling to the lungs from the respiratory centre summarised:

Answer 36

- 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