The Respiratory System

Question 1

1- give an overview of the five main stages involved in respiration

Answer 1

STAGE 1- Ventilation, expiration and inspiration
STAGE 2- Gas exchange in the lungs: External Respiration
STAGE 3- Transport of respiratory gases in the blood
STAGE 4- Tissue gas exchange: Internal Respiration
STAGE 5- Production of CO2 from metabolism transport to lungs for respiration

This is a cycle and repeats itself!

Question 2

1- what is respiration?

Answer 2

A chemical reaction
Breathing
The process of inhaling and exhaling gases to and from the external environment

Question 3

1- name the structures, in order, that make up the URT

Answer 3

Nasal cavity
Pharynx
Nasopharynx
Oropharynx
Laryngopharynx
Larynx

Question 4

1- name the structures, in order, that make up the LRT

Answer 4

Trachea
Bronchi
Bronchioles
Alveolar sacs
Alveoli

Question 5

1- describe the anatomical positions of both the URT and LRT

Answer 5

URT- organ outside thorax, above the vocal chords
LRT- organ within thorax, extends from the bottom of the larynx

Question 6

2- what role does the nose/nasal cavities play? (URT)

Answer 6

Nasal cavities- warm and humidify air as it is breathed in through the nose
Scroll shaped bones- conchae form slaves for air to pass through, swirled around and cleaned before it enters the lungs
Epithelial cilia and mucous membrane- line inside to trap unwanted particles to be coughed or swallowed
Nose hair- also trap particles
Olfactory epithelium- smell

Question 7

2- what role does the nasopharynx play? (URT)

Answer 7

To connect nasal passages to the rest of the respiratory system
Allows air to get from nose to lungs
Also controls pressure associated with the ear

Question 8

2- what role does the mouth play? (URT)

Answer 8

Draws air in
Moistens, humidifies and warms air
Air and food have shared pathway= risk of choking
When eating, the glottis closes and epiglottis folds backwards to stop food entering the lungs through the larynx

Question 9

2- what role does the oropharynx play? (URT)

Answer 9

The middle part of the throat
Transports air and food to the larynx

Question 10

2- what role does the larynx play? (URT)

Answer 10

Connects the lower part of the pharynx (the laryngopharynx) to the trachea
Vocal chords- speech
Protects the LRT from aspirating food into the trachea while breathing

Question 11

2- what role does the bronchi play? (LRT)

Answer 11

Carry air into your lungs
At the end of the bronchi are bronchioles which carry air to small sacs called alveoli (where gas exchange is then performed)
They further warm, moisten and clean air

Question 12

2- what role does the alveoli play? (LRT)

Answer 12

Small sacs where the lungs and blood exchange oxygen and carbon dioxide during the process of breathing

300 million
Vast surface area
Type I cells= cover 90% SA permit gas exchange with capillaries
Type II cells= cover 10% SA produce surfactant

Honeycomb like structure to maximise volume to give maximum gas exchange

Question 13

3- describe the position and structure of the lungs (referring to pleura, gross structure and divisions of the bronchi into alveoli)

Answer 13

Anatomical gross structure/ position of the lungs-
Lie in thoracic cavity
Separated by the heart
Each lung has… apex, base, two surfaces (medial and diaphragmatic), three boarders (anterior, interior, posterior)
Left lung- two lobes and one fissure
Right lung- three lobes and two fissures

Pleura-
Pleura= closed sac of serous membrane with fluid, one for each lung
Allows lung to expand and recoil (like punching a water balloon, your fist gets surrounded)
Lubricated with pleural fluid

Divisions of bronchi to alveoli-
Bronchi TO bronchioles TO terminal bronchioles TO respiratory bronchioles TO alveolar ducts TO alveoli
Conducting zone TO respiratory zone (this transition happens just after the terminal bronchioles)
Conducting zone- air is anatomical dead space, no alveoli, so no gas exchange in this zone

Question 14

4- what is the difference between respiration and ventilation?

Answer 14

Ventilation= mechanics involving air movement
Respiration= the gas exchange of oxygen and car in dioxide in the alveoli

Question 15

4- describe the mechanics of ventilation (with reference to muscles, diaphragm, and breathing cycle)

Answer 15

MUSCLES-
11 intercostal muscles between the ribs in two layers
External intercostals lift the rib cage upwards and outwards
Internal intercostal muscles extend down and backwards (e.g. during exercise)

Accessory muscles of forced inspiration- link vertebrae to ribs and increase expansion
Accessory muscles of forced expiration- increases speed and force, compressing lungs, allows respiratory rate to rise

DIAPHGRAM-
=The major muscle of respiration
Dome shaped muscular structure
Separates thoracic and abdominal cavity
Central tendon attached to the sternum
Two cura attach it to vertebral column

BREATHING CYCLE-
Average resp rate is 12-15 bpm
Every breath has 3 phases: Inspiration, Expiration and Pause

Inspiration- muscles contract, thoracic cavity enlarges and lengthens, pleura pulled outwards, lung tissue expands, alveoli pressure falls, air drawn into lungs to equalise atmospheric and alveoli pressure. Active process (needs energy). Approx two seconds.

Expiration- Muscles relax, inwards and downwards movement of rib cage, elastic recoil of lungs, lung pressure increases, air expelled from RT, at the end they still contain some air to prevent complete collapse. Passive process (no energy needed). Approx three seconds.

Pause- everything relaxes and body pauses

Question 16

5- describe the chemical and neural aspects of breathing

Answer 16

CHEMICAL-
Chemical regulation of respiration of controlled by the hydrogen ion content of neurones. This content is dependent of the tension between oxygen and carbon dioxide levels in blood flow.
CO2 increases = respiration rate increases

NEURAL-
Respiratory centre in brain stem receives input
Responds appropriately by sending signals to effector muscles
Central chemoreceptors- brain stem responds to pH changes in CSF, CSF pH reflects CO2 levels in blood, therefore respiration regulation is maintained by monitoring pH and resultantly CO2
Peripheral chemoreceptors- located in arteries above the heart. Sensitive to PCO2 and low arterial PO2. So under normal conditions, the peripheral chemoreceptors will regulate respiration.

Question 17

6- describe gaseous exchange. What is it involved in?

Answer 17

The process by which oxygen and carbon dioxide move between the bloodstream and the lungs- the primary function of the respiratory system

During gas exchange, oxygen moves from the lungs to the bloodstream. At the same time, carbon dioxide moves from the bloodstream to the lungs.

Ventilation, diffusion, profusion

Question 18

6- describe how we measure gaseous exchange in the body

Answer 18

Arterial Blood Gas (ABG)
This is a way to measure PO2 and PCO2

The amount of oxygen or carbon dioxide in someone’s blood is measured in partial pressure
PO2 (partial pressure of oxygen)
PCO2 (partial pressure of carbon dioxide)

Question 19

6- describe gas movement in alveoli

Answer 19

There is a pressure differential- this means that the amounts of pO2 and pCO2 are different in the bloodstream and lungs
Oxygen and carbon dioxide molecules swap places…
O2 level in alveoli= HIGH, O2 level in blood= LOW
CO2 in blood= HIGH, O2 in blood= LOW

Blood enters lung in pulmonary artery- LOW pO2, HIGH pCO2
Blood leaves lung in pulmonary vein- HIGH pO2, LOW pCO2

Question 20

6- describe gaseous diffusion

Answer 20

Gases have to diffuse across:
Alveolar fluid, alveolar membrane, tissue, capillaries, plasma and RBC membrane

O2 enters plasma and dissolves in the plasma
Enters the RBC and binds to its haemoglobin
98% of oxygen delivered to tissue is done so through Hb
Although in,y a small amount of oxygen is dissolved in Hb, it determines how saturated it is (how many O2 molecules it is carrying)

pO2 reflects the amount of dissolved oxygen in the blood
Dissolved O2 is able to diffuse into tissues
In lungs, dissolved O2 binds to Hb