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human physiology > Respiratory System > Flashcards

Respiratory System Flashcards

1
Q

What is Ventilation?

A

Breathing

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2
Q

Where does gas exchange occur?

A

Between lung surface and blood and other tissues of the body

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3
Q

What is the lungs gross anatomy?

A

5 lobes
3 right
2 left

Lie beneath rib cage
Base rests on diaphragm
Top converges into narrow apex under clavicle bone
Space between lungs (mediastinum) contains:
- heart
- oesophagus
- lower trachea
- primary bronchi

mid-way along surface of lung is a depression called Hilum

pulmonary artery and vein

nerves and bronchi enter and leave lungs

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4
Q

What are the functions of the respiratory system?

A

Primary function:
Gas exchange O2 for CO2

Secondary function:

  • warming and humidifying incoming air
  • keeping airway sterile
  • keeping airways open during pressure changes in breathing
  • keeping alveoli open against surface tension
  • regulation of air-flow and blood flow
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5
Q

What is the respiratory tract comprised of?

A

Upper and lower tracts

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6
Q

What is in the upper respiratory tract?

A 
The nose
The pharynx (throat)
The larynx (voice box)
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7
Q

What is the anatomy and function of the nasal cavity?

A 
Three curved tribunate bones churn air as it passes
Respiratory mucosa lines these bones to:
- warm
- moisten
- clean

Three layers of nasal respiratory mucosa:

  1. pseudostratified ciliated columnar epithelium
  2. goblet cells - secrete mucus
  3. basement membrane stuck to lamina propria

Air enters nose through nostrils and exits through back of nasal cavity.

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8
Q

What is the anatomy and function of the pharynx (throat)?

A

Fibro muscular tube that conducts air from nasal cavity to larynx

Lines with pseudostratified ciliated columnar epithelium

Surface of nasopharynx does not encounter food.

Oropharynx and laryngopharynx are lines with stratified squamous epithelium

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9
Q

What is the structure and function of the larynx?

A

Tube of interconnecting cartilage, ligaments and muscles to guard the lower respiratory tract during swallowing.

Prevents food entering trachea when swallowing by moving upwards, pushing against epiglottis, closing lower respiratory pathway.
Also contains vocal chords

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10
Q

What are the components of the lower respiratory tract?

A

The trachea
The bronchi
The bronchioles
The alveoli

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11
Q

What is the anatomy and function of the trachea?

A

Tube to conduct air between larynx and primary bronchi
Stiffened by hyaline cartilage rings to prevent collapse.

Trachea wall has four layers:

  1. respiratory mucosa: luminal (air) surface
  2. submucosa: connective tissue, blood vessels, glands, nerves
  3. cartilage ring: connected by smooth muscle to control size of lumen when breathing
  4. adventitia: loose connective tissue to keep trachea in place with chest wall.
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12
Q

What is the anatomy and function of the bronchi?

A

Conduct air from trachea through 1st, 2nd and 3rd degree bronchi into bronchioles.

Trachea splits into left and right primary bronchi then enter lung.
Primary bronchi divide into 5 secondary bronchi to conduct air into five lobes of lung.

Secondary bronchi branch into 18 tertiary bronchi which provide bronchopulmonary segments (10 right, 8 left)

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13
Q

Describe the bronchi walls:

A

Similar to trachea walls except goblet cells are less numerous
Broken ring of smooth muscle fibres to constrict during exhalation
Plates of hyaline cartilage are thinner and less numerous in 2nd and 3rd bronchi.

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14
Q

What is the anatomy and function of the bronchioles?

A

Conduct air between 3rd bronchi and alveoli

Branching tubules attached to alveoli surrounded by elastic fibres holding bronchioles open during breathing. Allows recoil.

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15
Q

What is the anatomy and function of the alveoli?

A

Each bronchiole is connected to an alveolar duct which protrudes many alveoli.

Cluster of alveoli : Alveolar sac

Network of capillaries and supportive cartilage and elastic fibres in the interstitial space separate alveoli

Alveoli are made of two types of cells (pneumocytes):

Type I:
simple squamous
main sites of gas exchange
Type II:
cuboidal with microvilli
secrete surfactant
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16
Q

How big is the respiratory membrane?

A

0.5 micrometres to allow quick and efficient diffusion

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17
Q

What is the mechanism of breathing?

A

Air flows into lungs due to gas pressure gradients caused by thoracic cavity muscles.

Volume changes (thoracic cavity) –> pressure changes –> air flow to equalize pressure

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18
Q

Define inspiration and Expiration

A

inspiration : flow of air INTO lungs

expiration: flow of air OUT OF lungs

19
Q

What is Boyle’s Law?

A

pressure x volume = constant (in closed system)

P x V = k

In a larger container molecules strike wall less frequently therefore exerting less pressure.

20
Q

Describe pressure changes in terms of ventilation:

A

For air to enter lungs:

  • lung pressure < atmospheric pressure
  • increasing volume decreases pressure
  • lung volume needs to increase for inspiration

For air to leave lungs:

  • lung pressure > atmospheric pressure
  • decreasing volume will increase pressure
  • lung volume needs to decrease for expiration
21
Q

What is in the thoracic cavity?

A

Ribs, spine, sternum form top and sides

Dome shaped sheet of muscle - diaphragm forms floor.

22
Q

What happens to the muscles during ventilation?

A

Inspiration:
chest expands
external intercostal muscles contract
diaphragm contracts

Expiration:
chest contracts
internal intercostal muscles contract
diaphragm relaxes

23
Q

What is the pleura?

A

2 layered serous membrane surrounding each lungs.
Visceral membrane lines lung
Parietal membrane lines inside of thorax

Cavity filled with pleural fluid:

  • slippery surface to aid movement
  • surface tension holds lungs tight against thoracic wall
24
Q

What is inter-pleural pressure?

A

always negative pressure: things stick together
surface tension in alveolar fluid
elasticity of lungs
elasticity of thoracic wall acts like a suction keeping lungs inflated

25
Q

What would happen if you decreased interpulmonary pressure?

A

Increase volume of lungs.

Only need 1mmHg difference to create gradient

26
Q

What happens if you puncture the pleural membrane?

A
  • 4mmHg in comparison to atmospheric pressure is all you need to cause a pressure gradient.

Air enters pleural cavity from high to low pressure
Loss of negative pleural pressure removes suction that keeps lung inflated
Lung collapses (pneumothorax)

Each lung is surrounded by its own pleural membrane and cavity so changes in one lung won’t affect the other.

27
Q

Summarise the events of inspiration:

A

Diaphragm and external intercostal muscles contract

Volume of thoracic cavity increases

Interpleural pressure becomes more negative

Lungs expand

Interpulmonary pressure becomes negative

Air flows into lungs

28
Q

Summarise the events of expiration:

A

Diaphragm and external intercostal muscles relax
internal intercostal muscles contract.

Volume of thoracic cavity decreases

Interpleural pressure becomes less negative

Lungs recoil

intrapulmonary pressure rises above atmospheric pressure

air flows out of lungs

29
Q

What factors affect ventilation?

A

Airway resistance:

  • gas molecules encounter resistance as they strike walls
  • airflow is inversely proportional to resistance.

Histamine:
released during an allergic reaction, constricts bronchioles, increasing airway resistance, decreasing airflow.

Epinephrine:
released by adrenal medulla during periods of stress, dilates bronchioles, decreasing airway resistance, increasing airflow.

30
Q

What is lung compliance?

A

The ease at which lungs expand.
Determined by two factors:
1. stretchability of elastic fibres within lungs
2. surface tension within alveoli

31
Q

Describe elastic fibres in the lungs:

A

Healthy lungs are abundant in elastic connective tissue
High lung compliance

Fibrosis reduces elastic tissue
Low lung compliance

32
Q

Describe surface tension and surfactant in the alveoli:

A

Strong attraction between water molecules at surface of alveolar fluid, drawing water molecules together. Creating tension.

Detergent-like surfactant interferes with water molecule attraction at surface, reducing tension, preventing alveolar collapse and increasing lung compliance.

33
Q

What is surfactant?

A

Dipalmitoyl-phosphatidycholine (DPPC)

Synthesised in type II cells

Hydrophillic head into aqueous layer
Hydrophobic portion in air.

34
Q

What is Dalton’s law?

A

The total pressure of a gas mixture is the sum of the partial pressures of the component gas.

partial pressure of an individual gas in a mixture of gases is directly proportional to the % of the gas in the total gas mixture.

At altitude, the proportion of each gas at sea level = high altitude BUT less air to breathe (reduced atmospheric pressure)

35
Q

What is Henry’s law?

A

The amount of gas which dissolves in a liquid is proportional to the partial pressure of the gas and it’s solubility.

k = Px / Cx 
k = equilibrium constant
Px = partial pressure of gas x in equilibrium with solution
Cx = concentration of gas x in solution
36
Q

Briefly describe what happens in external and internal respiration:

A

External respiration:

  • CO2 diffuses from pulmonary capillaries into alveoli
  • O2 diffuses from alveoli into pulmonary capillaries

internal respiration:

  • O2 diffuses from systemic capillaries into cells
  • CO2 diffuses from cells into systemic capillaries.
37
Q

What factors influence external respiration?

A

Efficient external respiration depends on three main factors:

  1. surface area of structure of respiratory membrane
  2. partial pressure gradients
  3. matching alveolar airflow to pulmonary capillary blood flow.
38
Q

What is the effect of a partial pressure of O2?

A

Facillitates efficient gas exchange by maintaining proportionate alveoli airflow to pulmonary capillary blood flow.

regions with high airflow to blood supply will have high PO2:

  • causes local arteriole to vasodilate
  • greater blood flow to collect O2.

regions with low airflow to blood supply will have low blood PO2:

  • causes local arterioles to vasoconstrict
  • blood flow redirected to alveoli with higher airflow and more O2 available
39
Q

What is the effect of a partial pressure of CO2?

A

When airflow through a bronchiole is high compared to blood supply, PCO2 falls causing bronchioles to constrict, reducing airflow proportional to local blood flow.

40
Q

What does internal respiration depend on?

A
  1. Available surface area
  2. Partial pressure gradients
  3. Rate of blood flow.
41
Q

What is the structure and function of haemoglobin?

A

Hb is made of 4 protein globlin chains:
2x alpha
2x beta
Each chain has a haem group at its centre
Each haem group consists of a porphyrin ring with an iron atom in the centre
Each Fe2+ atom can bind reversibly to one molecule of O2.
Therefore haemoglobin can bind 4 molecules of O2.

42
Q

What happens to haemoglobin and oxygen in a high PO2 environment like lung capillaries?

A

1 O2 binds to Hb, hb shifts to relaxed state.
Hb changes shape making it easier for another O2 molecule to bind to another haem group.
Hb affinity for O2 increases as its saturation increases - this is co-operativity.

43
Q

What is the utilisation coefficients for Hb-O2 saturation?

A

~ 98% at systemic circulation
~ 75% leaving capillaries of resting tissue
Hb gives up ~23% of O2 (utilisation coefficient)

remaining O2 is termed ‘venous reserve’
can sustain life for 4-5 mins in event of respiratory arrest.

44
Q

Factors affecting O2-Hb dissociation curve:

A

Temperature
CO2 blood transport
Plasma pH (Bohr Effect)
2,3-DPG

human physiology (4 decks)

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