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Biomedicine > 4. Respiratory System > Flashcards

4. Respiratory System Flashcards

1
Q

Functions of the respiratory system

A
  1. Gas exchange: Oxygen (O2) and carbon dioxide (CO2).
  2. Warming or cooling and moistening of air.
  3. Removal of inhaled particles (immunity).
    - removal of larger substances in nose.
    - smaller substances by mucociliary escalator.
    - alveolar macrophages in alveoli.
  4. Voice production and olfaction (smell).
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2
Q

Respiratory system structures

A
  • Nose
  • Paranasal sinuses
  • Pharynx (throat)
  • Larynx (voice box)
  • Trachea (windpipe)
  • Bronchi (left and right)
  • Bronchioles
  • Alveoli (air sacs)
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3
Q

Types of cell respiration

A
  1. External respiration: Exchange of gases between the blood and lungs (air).
  2. Internal respiration: Exchange of gases between blood and cells.
  3. Cellular respiration: Metabolic process whereby energy (ATP) is obtained by metabolising carbohydrates, fats and proteins.
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4
Q

Respiratory Tract Mucous Membrane

A

The respiratory tract is lined with a mucous membrane. This is a ciliated epithelial membrane that contains mucous-secreting goblet cells.

  • Mucus traps inhaled particles and acts as a surfactant (lowers the surface tension of a liquid, allowing easier spreading). Also has antimicrobial properties.
  • Cilia move the particle-laden mucus towards the oesophagus where it can be coughed up or swallowed, thus protecting the lungs from inhaled pathogens. This mechanism is called the mucociliary escalator.
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5
Q

Nose and Nasal Cavity

A

The nasal cavity is the first contact organ in the respiratory system and ‘conditions’ air.

  • It is an irregular cavity, divided by a septum (cartilage). Bordered posteriorly by skull bones.
  • The nasal cavity contains hairs that trap larger particles.
  • Internally has three nasal concha (‘turbinates’) — shelves that increase surface area and trap water during exhalation.
  • Contains olfactory receptors (interpret smell).
  • Internal nose lined by mucous membrane and capillaries.
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6
Q

Nasal Cavity Functions

A
  1. Filtering air
  2. Warming the air
  3. Humidification
  4. Sneezing reflex
  5. Olfactory function
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7
Q

Paranasal Sinuses

A

The paranasal sinuses are air-filled cavities within certain facial and cranial bones.

  • They are lined with mucous membranes that are continuous with the nasal mucosa lining. Secretions drain into nasal cavity.
  • Include: Frontal, ethmoid, sphenoid, maxillary.
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8
Q

Paranasal sinuses functions

A
  1. Resonance in speech.
  2. Lightening of cranial mass.
  3. Nasolacrimal ducts drain tears from the eyes.
  4. Moistening / humidifying of the air.
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9
Q

Pharynx

A

The pharynx is a straight muscular tube that connects the nose and throat.

  • Consists of the nasopharynx, oropharynx and laryngopharynx.
  • The pharynx contains the ‘eustachian tubes’, which connect the nasopharynx to the middle ear and allow equalisation of pressure in the middle ear.
  • Contains adenoids (‘nasopharyngeal tonsils’).
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10
Q

Pharynx functions

A
  1. Passageway for air and food.
  2. Warming and humidifying.
  3. Taste.
  4. Hearing.
  5. Equalisation of pressure in middle ear (eustachian tubes).
  6. Immune protection: Tonsils.
  7. Speech: Resonating chamber.
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11
Q

Larynx

A

The larynx is also known as the voice box and connects the laryngopharynx with the trachea.

  • Consists of nine pieces of cartilage (including the thyroid cartilage and epiglottis) and vocal cords.
  • The vocal cords are composed of mucous membrane foldings stretched horizontally.

Laryngeal muscles attach to the vocal cords and when contracted stretch them:
• Relaxed muscles = loose cords = low tone
• Contract muscles = tight cords = high tone
(vibrate rapidly).

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12
Q

Larynx functions

A
  • Production of sound (vocal cords) and speech (tongue, lips and cheeks).
  • Protection — the ‘epiglottis’ closes off the trachea during swallowing and hence prevents food entering the lungs.
  • Air passageway.
  • Warming and humidifying.
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13
Q

Trachea

A

The trachea (or windpipe) is roughly 12cm long and is made of incomplete C-shaped rings of hyaline cartilage.

The incomplete rings of cartilage are connected by smooth muscle, which is called ‘trachealis’.

  • Sympathetic (fight or flight) response - causes tracheal dilation.
  • Parasympathetic (rest and digest) response - causes tracheal constriction.
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14
Q

Trachea functions

A
  1. Air flow: Rings keep trachea open and unobstructed.
  2. Mucociliary escalator:
    Trapping inhaled particles and removing them from the respiratory tract.
  3. Cough reflex.
  4. Warming, humidifying, filtering (it is usually warm and humid by this point).
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15
Q

Cough reflex

A
  1. Epithelial receptors in the respiratory tract are highly sensitive to mechanical and chemical stimuli. The coughing reflex starts when irritation of the mucous membrane occurs.
  2. Stimulates sensitive nerve endings in the larynx, trachea, bronchi.
  3. A nerve impulse is sent via the vagus nerve to the respiratory centre in the brain stem.
  4. This causes deep inhalation and closure of the glottis (and vocal cords).
  5. Contraction of the abdominal / respiratory muscles to increase pressure.
  6. Forced removal of irritation.
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16
Q

Bronchi

A

The trachea divides into left and right bronchi at the vertebral level of T5.

  • The bronchi deliver air into the lungs.
  • Bronchi contain cartilage rings that maintain an open airway. Bronchi are lined with ciliated epithelium.
  • The right bronchus is more vertical, shorter and wider. Hence an aspirated object is more likely to enter the right lung.
  • Where the trachea divides into the two bronchi, an internal ridge called the carina is formed (this is the most sensitive structure in the system and triggers cough reflex).
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17
Q

Bronchioles

A

The bronchioles are continuations of the bronchi.

  • Bronchioles have no cartilage in their structure and instead contain more smooth muscle.
  • The bronchioles lead directly into the alveoli, where gas exchange occurs.

Control of air-entry via:

  • Sympathetic nervous system (SNS: Fight or flight) = bronchodilation.
  • Parasympathetic nervous system (PSNS: Rest and digest) = bronchoconstriction.
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18
Q

Alveoli

A

Alveoli are small hollow cavities that make up most of the lung volume. They act as the sites of gas exchange in the lungs.

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19
Q

How is alveoli gas exchange maximised?

A
  • A large surface area (approximately 80m ) created by 250 million alveoli in each lung.
  • Alveolar walls are very thin (single-layered).
  • Surrounded by many blood capillaries.
  • Alveolar surfaces are moist (gases exchange more easily when in water).
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20
Q

Alveolar Gas Exchange

A

In alveoli, oxygen and carbon dioxide are ‘exchanged’ between air and blood.

  • Gas exchange occurs between alveoli and capillaries.
  • Oxygen moves from the alveoli (after breathing in), into the blood. This causes the blood to become ‘oxygenated’.
  • Carbon dioxide moves from the blood (having been delivered via the pulmonary artery), into the alveoli, to be exhaled.
  • The movement of both gases occurs via diffusion (down the concentration gradient).
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21
Q

Type I alveolar cells

A

These are simple epithelial cells, covering 90% of the alveolar surface and are
very thin to support gas exchange.

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22
Q

Type II alveolar cells

A

• Secrete ‘alveolar fluid’ that contains ‘pulmonary surfactant’.

• Pulmonary surfactant reduces alveoli
surface tension, preventing alveolar collapse.

• The fluid allows gases to diffuse through it.

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23
Q

Alveolar macrophages

A

These are strategically located white blood cells (leukocytes) that engulf and destroy microbes entering the alveoli.

24
Q

Pulmonary Surfactant

A

Surfactant is a mixture of lipids and proteins that forms a surface film in alveoli.

  • The protein part is hydrophilic and resides in the alveolar fluid, whilst the lipid component is hydrophobic and faces the air.
  • surfactant reduces the surface tension within the alveoli, preventing them from collapsing and reducing the pressure required to re-inflate them.
  • Surfactant is not produced until 20-24 weeks’ gestation, so consider lung development in a premature baby.
25
Q

How many lobes of each lung

A
  • Right lung: Three lobes.

* Left lung: Two lobes (due to the heart).

26
Q

Pleura

A

The pleura are serous membranes that surround the lungs.

27
Q

Pleural Cavity

A
  • The pleura contain a visceral and a parietal layer, with a ‘pleural cavity’ in between.
  • The visceral and parietal pleura form a double layer separated by 5–10ml of serous fluid that prevents friction.
  • The pleura adhere to the lungs so that the lungs are sucked to the pleura (‘passive dilation’) — helps expansion of the lungs.
28
Q

pneumothorax

A

A pneumothorax (collapsed lung) occurs when damage to the pleura allows air into the pleural cavity.

29
Q

Ventilation

A

Ventilation is the process through which O2 and CO2 are transported to and from the lungs.

30
Q

Two phases of ventilation

A
  1. Inhalation

2. Exhalation

31
Q

The two areas breathing can come from

A
  • Abdominal (diaphragmatic) breathing: where most breathing should come from
  • Upper rib breathing
32
Q

Primary muscles of ventilation

A

Intercostal muscles:

Attached between ribs at right angles.

Contraction pulls ribs upwards (inhalation) expanding outward and increasing size of rib cage.

Diaphragm:

Attached to the lower ribs, sternum and lumbar spine. A domed muscle that separates the thoracic and abdominal cavity.

Contraction moves the diaphragm into the abdomen and draws air into the lungs.

33
Q

Secondary muscles of ventilation

A

‘accessory muscles’

  • These muscles are often over-recruited in patients suffering with breathlessness (e.g. asthmatics). They can become shortened and fatigued.
  • Most accessory muscles are located around the neck and chest.

Examples: trapezius, sternocleidomastoid and the scalenes.

34
Q

Inhalation

A
  • Inhalation is an active process requiring muscles.

* Negative pressure in the thoracic cavity causes air to enter lungs down a pressure gradient.

35
Q

Exhalation

A
  • Exhalation is typically a passive process — muscles relax.
  • This occurs through the elastic recoil of the lungs.
  • Should only be active during forceful breathing.
  • If elasticity is lost, for example, in pulmonary fibrosis, exhalation can become active with the recruitment of internal intercostal and abdominal muscles.
36
Q

Lung volume

A

The average pair of human lungs can hold about six litres of air. However, only a small amount of this capacity is used during normal breathing

37
Q

Tidal volume

A

The ‘tidal volume’ represents the normal volume of air that enters the lungs during inspiration when no extra effort is applied.

A normal tidal volume is about 500ml.

Men generally have larger lung volumes, as do taller individuals, non-smokers, athletes and those living at higher altitudes.

38
Q

Gases

A

Inspired air contains a large quantity of nitrogen and oxygen.

  • As oxygen has a strong affinity (attraction) for haemoglobin, oxygen will readily enter the blood and bind with haemoblogin molecules.
  • Haemoglobin is the key component of red blood cells and transports oxygen in the blood.
  • Nitrogen doesn’t bind to haemoglobin. Furthermore, nitrogen is not used or created in the body, so any nitrogen that has dissolved in the blood will remain at the same concentration.

Oxygen: in 21% out 16%
Carbon dioxide: in 0.04% out 4%
Nitrogen and rare gases: in 78%
out 78%

39
Q

Gases in Blood: Oxygen

A

98.5% of oxygen in the blood is transported by haemoglobin (Hb) in red blood cells.

• 1.5% of oxygen is dissolved in plasma
(oxygen dissolves poorly in water).

• Haemoglobin changes colour depending on how much oxygen is bound to the molecule.

Oxygen is an essential gas in the body. Cells use oxygen to create the energy that is required for various processes.

40
Q

Oxyhaemoglobin

A

Is when plenty of oxygen is bound to Hb

41
Q

Deoxyhaemoglobin

A

is Hb that lacks oxygen.

42
Q

Gases in Blood: Carbon Dioxide

A

Carbon dioxide diffuses into the blood from respiring cells easily. It is transported in the following ways:

• 70% found in plasma as HCO3-
(bicarbonate).

  • 23% carried in RBCs (bound to haemoglobin).
  • 7% dissolved in plasma (the water component of blood).
43
Q

Bicarbonate buffer reaction

A
  • CO2 diffuses down its concentration gradient from tissues into the blood.
  • Because of the high water content of blood, CO2 combines with water to produce carbonic acid (H2CO3).
  • As carbonic acid is unstable, it decomposes immediately into bicarbonate and H+ .
  • Hydrogen is exhaled and excreted into urine to reduce the acidity. In addition, the bicarbonate formed is alkaline, which ‘buffers’ the acidity of blood to keep pH stable.
44
Q

Respiratory System: Blood pH

A

pH is the measure of acidity, alkalinity and neutrality.

  • Blood pH needs to be controlled within very narrow limits.
  • Low pH = elevated H+ ion concentration (more acidic). • High pH = more alkaline.
45
Q

What causes a low pH (acidity) in the blood?

A

When CO2 dissolves in the blood, it causes an increase in H+ ions and thus an increase in acidity. This leads to ‘respiratory acidosis’.

  • It is not just CO2 that causes acidosis; exercise produces lactic acid and fasting produces ketoacids which enter the blood. This is called ‘metabolic acidosis’.
  • Ventilation helps to lower the acidity of body fluids via exhalation of CO2.
46
Q

Increase in acidity is managed in three ways

A
  1. Buffer systems
    • Temporarily bind to H+ removing them from solution (i.e. proteins, bicarbonate).
  2. Increased exhalation of CO2
  3. Kidney excretion of H+
    • Slow mechanism.
    • Kidneys can also synthesise new
    bicarbonate and reabsorb bicarbonate, thus influencing pH.
47
Q

Cell Respiration

A

Cell respiration describes the process of energy production (ATP) within cells.

• Glucose is the primary organic molecule metabolised for ATP production. Fats and proteins are also used.

Energy is produced by either:
1. Aerobic respiration (with oxygen) 38 ATP (total yield) + water + CO2.

  1. Anaerobic respiration (no oxygen) 2 ATP (total yield) + lactic acid.
48
Q

The oxygen availability of cells depends on what?

A

The functioning of the respiratory system (breathing and gas exchange), as well as circulation to deliver oxygen.

49
Q

Ventilation Control

A

The control of ventilation is primarily involuntary.

  • The ‘respiratory centre’ is located in the brainstem (medulla oblongata and pons). This receives inputs from different parts of the body.
  • Chemical receptors found in the brainstem measure CO2 and acidity (H+ concentration).
  • Chemical receptors in the aorta and carotid artery measure CO2, O2 and acidity levels.
  • Stretch receptors in the walls of the bronchi and bronchioles detect over-inflation.
  • If receptors detect high arterial CO2, this triggers hyperventilation (to excrete / exhale excess CO2).
50
Q

Smoking and the respiratory system

A

Smoking cigarettes significantly increases the risk of lung diseases.

  • Cigarettes contain substances known as ‘carcinogens’. Carcinogens are substances that can cause cancer.
  • Smoking also damages the delicate cilia that line the respiratory tract. Normally these cilia would sweep trapped particles out of the lungs.
  • Following cilia damage, mucus and trapped particles build up in the lungs, causing a smoker’s cough, whilst also increasing the risk of pulmonary infections, bronchitis and emphysema.
51
Q

Respiratory investigations: Common Signs & Symptoms

A 
• Congestion.
• Runny nose.
• Sneezing.
• Cough.
• Sputum.
• Wheezing.
• Chest pain.
• Breathlessness.
• Dyspnoea (difficulty breathing).
• Orthopnoea (breathless when
lying down).
• Hyperventilation (over-breathing).
• Cyanosis.
52
Q

Sputum: mucoid

A

Clear, grey/white

Causes: Asthma & bronchitis

53
Q

Sputum: purulent

A

Thick, yellow / green.

Causes: Infections (bronchitis, pneumonia).

54
Q

Sputum: serous

A

Clear, frothy, pink.

Causes: Pulmonary oedema.

55
Q

Sputum: blood

A

Blood.

Causes: Lung cancer, TB, pulmonary embolism, clotting disorders.

56
Q

Investigations

A

Medical investigations:

  • Blood test (i.e. white blood cell count, inflammatory markers).
  • Biochemistry tests.
  • Sputum analysis and microbiology.
  • Imaging — chest x-ray, MRI, CT.

Physical examination:

  • Percussion (‘tapping to the thoracic cage’) and auscultation.
  • Respiratory function tests — measure inspiration / expiration of lungs and gaseous exchange in the lungs / circulation.
  • Finger ‘clubbing’
  • Chest deformity (barrel chest)

Biomedicine (9 decks)

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