Respiratory System

Question 1

What are the 6 main parts of the RS?

Answer 1

These include the nose, pharynx, larynx, trachea, bronchi and bronchioles

Question 2

How does the nasal cavity work?

Answer 2

The nostrils are the main route of air entry into the respiratory system, behind which there is a large cavity with the right and left nasal cavities separated by the nasal septum.

Hair in nostrils trap large particles/ filter dust

The conchae are curved shelves of bone that project into the nasal cavity creating pathways for air to flow.

Their function is to increase the surface area of the nasal cavity which increases the amount of inspired air that can come into contact with cavity walls.

They also disrupt the fast flow of air making it slow and turbulent so it spends longer in the nasal cavity where the air is warmed, humidified and filtered.
Air is humidified as it travels over moist mucosa where its saturated with water vapour.
Air is warmed by the blood capillaries in the vascular mucosa.
Mucus from goblet cells traps dust
The cilia (hair like organelles) lining the respiratory tract waft mucus towards throat where it can be swallowed or coughed up.

Question 3

Functions of the Pharynx?

Answer 3

Passage for air and food
Warms and humidifies
Hearing
Protection - houses tonsils
Speech - acts as resonating chamber for sound

Question 4

What are the 3 parts of the Pharynx?

Answer 4

Nasopharynx - air passage, 2 openings of auditory tubes. Ciliated columnar epithelium.

Oropharynx - air and food passage. Stratified squamous epithelium.

Laryngopharynx - air and food passage. Stratified squamous epithelium.

The nasopharynx lies behind the nose and acts only as an air passage and contains 2 openings to the auditory canals.
The oropharynx lies behind the mouth and extends from the soft palate to the epiglottis so both air and food can pass through this.
The laryngopharynx extends from the oropharynx above and continues to the oesophagus acting as a passageway for food and air. It sits posterior (behind) the larynx where the respiratory and digestive tracts separate.

Question 5

What is the larynx made up of?

Answer 5

Connects pharynx and trachea
Made up of 9 irregularly shaped cartilages attached by ligaments and membranes:
1 thyroid cartilage (Adam’s apple)
1 cricoid cartilage
2 arytenoid cartilages
1 epiglottis

Question 6

What are the functions of the larynx?

Answer 6

Production of sound
Speech
Protection of lower respiratory tract
Passageway for air
Humidifying, filtering and warming

Question 7

What are the functions of the trachea?

Answer 7

Support and patency
Mucociliary escalator
Cough reflex
Warming, humidifying and filtering - however air normally humidifed and at body temperature when reaches trachea.

The tracheal wall is composed of 3 layers of tissue: the lining which is the ciliated columnar epithelium, the middle layer consists of cartilages and bands of smooth muscle and the outer layer which contains connective tissue that’s reinforced and is held open by 16-20 c shaped cartilage rings which prevent the trachea from collapsing during an active breath cycle.

Question 8

How many primary Bronchi are there?

How many in right lung and left?

Answer 8

2 Primary bronchi

Right lung - 3 lobes.
The right lung is divided into 3 lobes: superior, middle and inferior,
Left lung - 2 lobes
whilst the left lung is smaller due to the heart occupying space and so is only divided into 2 lobes: superior and inferior. These bronchi are lined with the same layers of tissue as the trachea

Question 9

Function of Bronchi?

Answer 9

Control of air entry - diameter of respiratory passages altered by contraction/relaxation of smooth muscle in their walls, regulates speed and volume of airflow

Question 10

How is breathing controlled?

Answer 10

Effective control of breathing enables the body to regulate blood gas levels in a variety of physiological, environmental and pathological conditions and is normally involuntary. We can voluntarily control our breathing during activities such as speaking and singing but if CO2 levels rise this is overridden.
In the brain there is an area that is also known as the respiratory centre which is located specifically in the brain stem in the medulla. Within these areas of the brain there are groups of nerves which control the respiratory rate and depth of breathing. The 3 important groups of neurones here include: the inspiratory group (set the basic rhythm of breathing), an expiratory group (control expiration) and neurones in the pneumotaxic area (these are located in the pons and helps regulate rate and depth of breathing).

Question 11

How is tidal volume measured?

Answer 11

Tidal Volume = the amount of air passing in and out of the lungs in one breath

Question 12

What is

IRV - inspiratory reserve volume

ERV expiratory

RV reserve volume

Inspiritaory capacity

Functional residual capacity

Vital capacity

Total lung capacity

Answer 12

Inspiratory reserve volume (IRV) - amount of air that can be forcibly inspired beyond the tidal volume
Expiratory reserve volume (ERV) - amount of air that can be expelled from the lungs after a normal tidal volume expiration
Residual volume (RV) - amount of air left in lungs even after largest expiration - cannot be directly measured.
Inspiratory capacity - total amount of air that can be inspired after a normal tidal volume so it is the sum of TV and IRV.
Functional Residual capacity - amount of air remaining in lungs after a normal tidal volume expiration so is the sum of RV and ERV - prevents alveoli collapse on expiration.
Vital capacity - maximum volume of air that can be moved in and out of the lungs so is sum of TV+IRV+ERV
Total lung capacity - the maximum amount of air the lungs can hold - in average adult is around 6 litres. Is the sum of TV+IRV+ERV+RV - cannot be directly measured in tests because even after forced expiration the RV of air still remains in the lungs.
Lung function tests can be carried out to determine respiratory function which can help in diagnosing and monitoring respiratory disorders.

Question 13

How is carbon dioxide removed from the body - 3 mechanisms

Answer 13

As bicarbonate ions (HCO3-) in the blood plasma (70%) - CO2 combines with water when inside red blood cell forming carbonic acid (H2CO3) which is unstable and dissociates into hydrogen ions and bicarbonate ions.

Combined with haemoglobin in the erythrocytes as carbaminohemoglobin (23%)

Dissolved in the blood plasma (7%)

Question 14

What is pleura

Answer 14

The pleura is a closed sac of a thin serous membrane surrounding each lung.
A serous membrane is a thin membrane made out of epithelial cells, some cells make the serous secretion (watery secretion) epithelial cells held together by connective tissue layers like every other tissue in the body

Question 15

What is visceral pleura

What is parietal pleura

Answer 15

Visceral pleura - adheres to the lung covering the lung - folds back on itself near the hilum to from the parietal pleura
Parietal pleura - adheres to the inside of the chest wall and the upper surface of the diaphragm - folds back on itself at the hilum to form the visceral pleura.

Question 16

What are the walls of alveoli made up of?

What do type 2 alveoli cells do?

Answer 16

The walls of alveoli are made up of single layer of squamous epithelial cells = type 1 alveolar cells surrounded by flimsy basement membrane.

Type 2 alveolar cells are cuboidal epithelial cells, scattered among type 1 cells. These secrete surfactant (detergent like substance) which coats the gas exposed alveolar surface, stops alveoli drying out and reduces surface tension preventing alveolar collapse during expiration. Secretions of surfactant start in about the 35th week of fetal life, its presence in newborns permits expansion of the lungs and the establishment of respiration immediately after birth. May not be present in sufficient amounts in immature lungs of premature babies causing serious breathing problems.
External surfaces of alveoli covered with ‘cobweb’ of pulmonary capillaries. Blood flowing past on one side and gas on the other.

Question 17

How does the pulmonary blood supply work?

Answer 17

The pulmonary trunk divides into the right and left pulmonary arteries carrying deoxygenated blood to the lungs.
Within the lungs the pulmonary arteries divide into many branches which end in a dense capillary network around the alveoli.
The exchange of gases between air in the alveoli and blood in the capillaries takes place and then the pulmonary capillaries merge into a network that forms the two pulmonary veins carrying oxygenated blood back to the heart.

Question 18

What are the 3 phases of breathing?

Answer 18

When we breathe each breath consists of 3 phases: inspiration, expiration and pause (at rest).
Breathing also depends though on changes in pressure and volume in the thoracic cavity.
It follows the underlying principles of Boyle’s law which states that the pressure exerted by a gas is inversely proportional to its volume at constant temperature.
This is that as the volume of a container the gas is in increases, the pressure of the gas inside it decreases and as the volume of the container decreases the pressure of the gas increases.

Question 19

What is the cycle of breathing?

Answer 19

Intact pleura and some air left in lungs at end of expiration prevents lung collapse.
Inspiration = active process, requires energy for muscle contraction.
Expiration = passive process does not require energy.

Question 20

Explain how has exchange works?

Answer 20

Relating this to the respiratory system our lungs are our containers and when we breathe in we increase the volume of these causing the pressure of gas in our lungs to decrease. As the pressure inside the lungs is reduced and lower than atmospheric pressure air will naturally flow into the lungs until there is no pressure difference. The process of inspiration is active as it needs energy for muscle contraction. Conversely when we breathe out the volume of our chest cavity reduces so the pressure increases above atmospheric pressure therefore air moves out of our lungs and into the atmosphere. At the end of expiration the lungs will always contain some air, this along with the intact pleura prevents the lungs from complete collapse. Expiration is a passive process as it doesn’t require any energy. After expiration there is a pause before the next cycle begins.

As air will naturally flow from an area of high pressure to an area of low pressure.

Question 21

Atmospheric air - gases exchange.

Answer 21

Atmospheric air is a mixture of gases - nitrogen, oxygen, carbon dioxide, water vapour and small amounts of inert gases. Each gas in this mixture exerts a part of the total pressure proportional to its concentration i.e. the partial pressure (PO2 and PCO2). (Dalton’s Law is another useful gas law to be aware of that states - the total pressure of a mixture of gases, is equal to the sum of the partial pressures of the individual gases).
This is relevant to the respiratory system as the differences in partial pressure dictate the movement of oxygen and carbon dioxide between the atmosphere, the lungs and the blood. A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower.

Question 22

Atmospheric air - gases exchange.

Answer 22

Atmospheric air is a mixture of gases - nitrogen, oxygen, carbon dioxide, water vapour and small amounts of inert gases. Each gas in this mixture exerts a part of the total pressure proportional to its concentration i.e. the partial pressure (PO2 and PCO2). (Dalton’s Law is another useful gas law to be aware of that states - the total pressure of a mixture of gases, is equal to the sum of the partial pressures of the individual gases).
This is relevant to the respiratory system as the differences in partial pressure dictate the movement of oxygen and carbon dioxide between the atmosphere, the lungs and the blood. A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower.

Question 23

How are alveoli adapted to gaseos exchange?

Answer 23

Thin respiratory membrane

Cell wall is one cell thick so short diffusion distance

Large surface area of alveolar membrane

Large surface area of capillaries

Question 24

How is oxygen transported?

Answer 24

Oxygen and carbon dioxide are carried in the bloodstream.

Oxygen is carried by a protein called haemoglobin which is found in the erythrocytes (red blood cells). Erythrocytes contain millions of heamoglobin proteins, with each haemoglobin having the capacity to carry 4 oxygen molecules.

When oxygen combines with haemoglobin it creates oxyhaemoglobin, this is how 98.5% of the oxygen in our bodies is carried. The other 1.5% of oxygen is dissolved in blood plasma.
The amount of oxygen that is attached to haemoglobin at a given time is measured as an oxygen saturation (SaO2).

Question 25

How is CO2 transported?

Answer 25

Carbon dioxide is one of the waste products of metabolism. It is excreted by the lungs and is transported by 3 mechanisms.

As bicarbonate ions (HCO3-) in the blood plasma (70%) - CO2 combines with water when inside red blood cell forming carbonic acid (H2CO3) which is unstable and dissociates into hydrogen ions and bicarbonate ions.
Combined with haemoglobin in the erythrocytes as carbaminohemoglobin (23%)
Dissolved in the blood plasma (7%)

CO2 levels must be managed carefully as an excess or deficiency leads to significant disruption to our acid-base balance which is the levels of acids and bases (Base (alkaline) - a substance that can neutralize acid by accepting hydrogen ions) in your blood which your body functions best at, the pH balance of the body. Sufficient CO2 is essential for the bicarbonate buffering system that protects against a fall in body pH. Excess CO2 however reduces blood pH because it dissolves in body water to form carbonic acid.