Anatomy & Physiology

Question 1

What are the major functions of the respiratory system?

Answer 1

Supplying oxygen and eliminating carbon dioxide.

Question 2

What structures does the upper airway consist of?

Answer 2

Nasal passages;
Mouth;
Pharynx;
Larynx.

Question 3

What is the function of the nasal passage?

Answer 3

To warm and filter air. Turbinates create turbulence to increase impaction of larger particles into the hairs and mucous within the nasal passage. These particles are then moved towards the pharynx where they are swallowed.

Question 4

What is the function of the mouth?

Answer 4

Dual function of breathing and eating. The mouth allows large volumes of aid to be moved in and out of the lungs e.g during exercise. However, less warming and filtering occurs.

Question 5

Name the lobes of the left and right lungs.

Answer 5

Right lung:
Superior
Middle
Inferior

Left lung:
Superior
Inferior

Question 6

Describe the structure of the airways, beginning at the trachea.

Answer 6

The trachea is the largest of the airways and contains 15-20 C-shaped tracheal cartilages which protect the anterior and lateral surfaces of the trachea. The posterior open portion faces the oesophagus, allowing for distortions when swallowing food.

The trachea splits and the carina, into the left and right primary (main) bronchus.

The primary bronchi then divide into secondary (lobar) and tertiary (segmental) bronchi.

Each airway continues to branch into two more airways, getting smaller and smaller, eventually becoming terminal bronchioles.

Question 7

Describe the general structure of an airway.

Answer 7

The airways generally have three layers:

• Inner mucosal surface - consists of ciliated epithelium and mucous-secreting goblet cells. These make up the mucocilliary escalator.
• Smooth muscle layer - found in decreasing amounts from the large airways down to the terminal bronchioles.
• Outer connective layer - consists of connective tissue including cartilage in the large airways. Once the airways enter the lungs, the cartilage is lost and smooth muscle increases.

Question 8

What are alveoli?

Answer 8

Alveoli are microscopic structures connected to respiratory bronchioles along regions called alveolar ducts, which end in alveolar sacs. Alveolar sacs consist of multiple individual alveoli of which there are approximately 150 million per lung. Alveoli provide a large surface area and are composed of a single layer of cells, surrounded by pulmonary capillaries.

Question 9

Describe the alveolar epithelium.

Answer 9

Alveolar epithelium is made up of a very thin layer of simple squamous epithelial cells (Type I cells). Amongst type I cells there are scattered Type II cells. These Type II cells secrete surfactant, a mixture of phospholipids and proteins, which reduces surface tension and prevents alveoli from collapsing. Alveolar macrophages roam the surface of the epithelium, phagocytosing any particulate matter that has evaded other respiratory defences and reached the alveoli. Open alveolar pores connect adjacent alveoli to equalise air pressure.

Question 10

Define anatomical dead space.

Answer 10

Anatomical dead space is all of the air that fills the conducting airways without contributing to gas exchange. Anatomical dead space in adults is approximately 150ml.

Question 11

What is pulmonary ventilation.

Answer 11

Pulmonary ventilation involves the exchange of gases between the atmosphere and alveoli. It involved the inspiration (approximately 2 seconds) and expiration (approximately 3 seconds).

Question 12

What is tidal volume?

Answer 12

The volume of air in normal inspiration and expiration (approximately 500ml in adults).

Question 13

What is Dalton’s Law?

Answer 13

The total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture.

Question 14

What is Fick’s Law of diffusion?

Answer 14

The rate of diffusion of a gas increases:
• as the surface area of the membrane increases
• the thinner the membrane
• the greater the partial pressure gradient across the membrane
• the more soluble the gas

Question 15

How is oxygen transported in the blood?

Answer 15

• 97-99% is bound to haemoglobin (oxyhaemoglobin)

* remainder dissolved in plasma

Question 16

Where are the respiratory centres and what do they control?

Answer 16

The respiratory centres are located in the pons and the medulla of the brain stem.

• the pons - centres within the pons coordinate the transition between inspiration and expiration
• the medulla - the medullary rhythmicity area controls the basic rhythm of respiration. It has inspiratory and expiratory areas. Chemoreceptors in the aortic arch and carotid bodies monitor blood gases and send signals to the medulla to control respiration.

Question 17

What is Boyle’s Law?

Answer 17

Volume of gas is inversely proportional to the pressure to which it is subjected provided the temperature remains constant. Therefore if volume increases, pressure must decrease, and vice versa.

Question 18

Explain how inspiration occurs.

Answer 18

Nerve cells have intrinsic excitability. Nerve impulses are generated and transmitted along the phrenic nerve to the diaphragm and the external intercostal nerve to the external intercostal muscles to cause the diaphragm to flatten and the ribs to move up and outwards, expanding the thoracic cavity. As the ribs move, the pleural membranes of the lungs are pulled, causing the lungs to expand. Gas pressure within the thoracic cavity falls, relative to the atmosphere and so air flows into the lungs from high to low pressure.

Question 19

Explain how expiration occurs.

Answer 19

When nerve cells become inactive, passive relaxation of external intercostal muscles and diaphragm cause the rib cage to move downwards and the diaphragm becomes dome shaped. The thoracic cavity and lung volume decreases, aided by the elastic recoil of alveolar tissue, so gas pressure in the lungs increases relative to the atmosphere. Air flow from the alveoli into the atmosphere, from higher to lower pressure.

Question 20

What 2 mechanisms aid pulmonary ventilation?

Answer 20

1) the lungs remain partially filled with air at the end of expiration which prevents the alveoli from collapsing - this is known as the residual volume.
2) lower gas pressures in the pleural cavity (intrapleural pressures) also helps to keep the alveoli open.

Question 21

Name the 8 factors that modulate breathing?

Answer 21

• Higher brain receptors in the cerebral cortex
• Respiratory centres in the pons and medulla of the brain stem
• Stretch receptors in the lungs
• Irritant receptors
• Receptors in muscles and joints
• Central chemoreceptors
• Peripheral chemoreceptors
• Other receptors such as pain receptors in the hypothalamus

Question 22

What is dyspnoea?

Answer 22

Difficulty in breathing.

Question 23

What is tachypnoea?

Answer 23

Faster than normal rate of breathing.

Question 24

What is apnoea?

Answer 24

Absence of breathing.

Question 25

What is orthopnoea?

Answer 25

Difficulty in breathing when lying flat.

Question 26

What is Cheyne-Stokes Respiration?

Answer 26

Periodic breathing.