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Human Physiology > Respiratory System > Flashcards

Respiratory System Flashcards

1
Q

Haemoglobin - Loading and Unloading Oxygen

A

Haemoglobin must reversibly bind O2
> Loading O2 in the lungs
> Unloading O2 at the tissues
Aided by cooperative binding and release

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2
Q

Factors Affecting Pulmonary Ventilation: airways resistance

A
  • airflow inversely proportional to airway resistance

- primary determinant of resistance is radius of conducting airways

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3
Q

Chemical Control of Respiration

A
  • Chemoreceptors = sensors that detect PCO2, pH and PO2
    Peripheral chemoreceptors - in aorta and carotid arteries
    Central chemoreceptors - medulla

Exert secondary control over breathing

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4
Q

Inspiratory Reverse Volume

A

Extra volume of air that can be maximally inspired over and above the typical resting tidal volume
Ave. Value: 3000mL

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5
Q

Respiratory Epithelium: Component of the Respiratory Defence System

A
  • Pseudostratified columnar epithelium
  • Similar to nasal cavity and nasopharynx
  • Mucous cells + mucous glands in lamina propria
  • Cilia on epithelial cells
  • Mucociliary escalator
  • Other defences e.g. immunological and biochemical
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6
Q

3 Processes of Respiration: External respiration

A
  • Includes all processes involved in exchanging O2 and CO2 with the interstitial fluids and external environment
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7
Q

Oropharynx (middle)

A

Communicates with oral cavity

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8
Q

External Respiration: Summary

A

1) Primary ventilation: physical movement of air into and out of lungs
2) Gas diffusion: at lungs and in tissues
3) transport of O2 and CO2

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9
Q

Alveolar Type 2 Cells

A
  • Cuboidal epithelial cells
  • Microvilli
  • Secrete pulmonary surfactant which reduces surface tension
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10
Q

Inspiratory Capacity

A

Maximum volume of air that can be inspired at the end of a normal quiet expiration (IC = IRV + TV)
Ave. Value: 3500mL

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11
Q

Three Levels of Control

A

1) Neural Control
2) Chemical Control
3) Voluntary Control

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12
Q

Upper Respiratory Tract: Nose

A

Main functions:
1) warming, moistening and filtering air
2) olfaction
3) modifying speech vibrations
- air enters the respiratory system through the nostrils and into the nasal vestibule
Nasal hairs: particle filtration system - part of respiratory defence system

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13
Q

Composition and Partial Pressures of Normal Air

A
  • Alveolar PO2 is less than atmospheric PO2
  • Air in alveolus is saturated with water vapour and contains 40mmHg Co2 from venous blood
  • Hence alveolar air contains two additional gases not present in significant quantities in the air that we breathe
  • However, total atmospheric pressure is still 760mmHg
  • Hence alveolar PO2 lower
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14
Q

Pressures Important in Ventilation: Atmospheric Pressure (P atm)

A

~760mmHg

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15
Q

Pulmonary Gas Exchange and Transport

A

1) Oxygen enters the blood at alveolar - capillary interface
2) Oxygen is transported in blood dissolved in plasma or bound to haemoglobin inside RBCs
3) Oxygen diffuses into cells
Cellular Respiration Determines Metabolic CO2 Production
4) CO2 diffuses out of cells
5) CO2 is transported dissolved bound to haemoglobin, or as HCO3-
6) CO2 enters alveoli at alveolar-capillary interface

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16
Q

Structures of the Respiratory System: Lower

A
  • Larynx (voice box)
  • Trachea (wind pipe)
  • Bronchi
  • Smaller (respiratory bronchioles)
  • Alveoli
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17
Q

Neural control of Respiration

A
  • Nerve impulses from medullary respiratory centres sent via motor neurons to:
    > diaphragm (phrenic nerve)
    > intercostal muscles (intercostal nerves)
  • Stimulate contraction
    > inhalation
  • When impulse cease: expiration (passive)
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18
Q

Voluntary Control

A
  • Cerebral Cortex
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19
Q

Respiratory Minute Volume and Dead Space

A

Respiratory system adopts to changing oxygen demands by varying:
> the number of breaths per minute (Respiratory Rate)
> the volume of air moved per breath (Tidal volume)
Healthy adults:
> 12bpm x 500mL tidal volume
Respiratory minute volume (aka Pulmonary ventilation):
> amount of air moved into and out of lung per minute
> respiratory rate > tidal volume
Fresh air in conducting airways (trachea, bronchi and bronchioles) does not particpate in gas exchange
- Known as anatomic dead space (physical limitation)
- only ~70% of fresh air reaches alveoli

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20
Q

External Respiration

A

At lungs, diffusion of:
- O2 from alveoli to blood
- CO2 from blood to alveoli
> Blood leaving pulmonary capillaries mixes with blood that has supplied lung tissue
> PO2 of blood in pulmonary venous & systemic arterial blood slightly lower than in pulmonary capillaries

At tissues, diffusion of:

  • O2 from blood to tissues
  • CO2 from tissues to blood
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21
Q

Neural control

A
  • Involuntary establishment of basic breathing rhythm
    > Rhythm centre - medulla oblongata
    > Basic rhythm: 10-15 inhalations per minute, inspiration: 2 sec, expiration: 3 sec
  • Involuntary adjustment of rate and depth: controlled by neurons in the pons and receptor feedback from lungs and airways
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22
Q

Lower Respiratory Tract: Trachea

A
  • Anterior to oesophagus
  • C-shaped cartilage rings provide support that prevents tracheal wall collapsing during inhalation and allows passage of food through oesophagus (soft posterior wall)
  • Extends into mediastinum where it branches through into right and left pulmonary bronchi
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23
Q

Alveolar Ventilation

A

Instead measure alveolar ventilation:
> Respiratory rate = TV - ADS
Relative rate and depth of breathing determine efficiency of alveolar ventilation
- Same pulmonary ventilation = increasing alveolar ventilation
- More efficient to breathe deeper and slower

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24
Q

Upper Respiratory Tract: Pharynx

A
  • Chamber shared by digestive and respiratory system
  • Divided into:
    1) Nasopharynx (superior)
    2) Oropharynx (middle)
    3) Laryngopharynx (inferior)
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25
Q

Peripheral chemoreceptors

A
  • Strongly detect changes in plasma pH (caused by changes in CO2)
  • Weaker response directly to PCO2
  • Weak response to PO2 - only when very low (<60mmHg:90% saturated)
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26
Q

Carbon dioxide transport

A

Method of Transport in Blood: Physically dissolved
% Carried in this form: 7%

Method of Transport in Blood: Bound to Haemoglobin
% Carried in this form: 23%

Method of Transport in Blood: As bicarbonate ion
% Carried in this form: 70%

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27
Q

Nasopharynx (superior)

A
  • Contains tonsils

- Exchanges air with eustachian tubes that equalises air pressure across the ear drum

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28
Q

Dorsal Respiratory Group

A
  • inspiratory centres

- functions in quiet and forced breathing

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29
Q

Haemoglobin Increases Oxygen Transport

A

a) Oxygen transport in blood without haemoglobin
Alveolar PO2 = Arterial PO2
b) Oxygen transport at normal PO2 in blood with haemoglobin - red blood cells with haemoglobin are carrying 98% of their maximum load of oxygen
c) Oxygen transport at reduced PO2 in blood with haemoglobin - red blood cells carrying 50% of their maximum load of oxygen

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30
Q

Deep forceful breathing: Deep inhalation

A

Accessory muscles of inhalation participate to increase size of thoracic cavity
> sternocleidomastoid - elevate sternum
> scalenes - elevate first two ribs
> pectoralis minor - elevate 3rd-5th ribs

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31
Q

Tidal Volume

A

Volume of air entering or leaving lungs during a single breath
Ave. Value: 500mL

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32
Q

Lungs - Pleural Membranes

A
  • Mediastinum separates the thoracic cavity into two distinct compartments
  • Pleural membranes enclose each lung
    > Parietal pleura: outer layer attached to wall of thoracic activity
    > Visceral pleura: inner layer covering surface of lung
    > Pleural cavity: contains lubricating fluid secreted by membranes, high cohesive forces
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33
Q

Deep forceful breathing: Deep exhalation

A

Exhalation during forceful breathing is an active process

> muscles of exhalation increase pressure in abdomen and thorax

34
Q

Bronchopulmonary Lobule

A
  • Lobule begins from terminal bronchiole (end of conducting zone)
  • Each lobule contains: lymphatics, arterioles, capillaries, venules
  • Terminal bronchiole subdivides into several respiratory bronchioles
  • Marks beginning of respiratory zone
  • Branch into alveolar ducts
  • Each leading to an alveolar sac consisting of several alveoli
35
Q

Fick’s Law of Diffusion

A
  • The rate of diffusion (R) of a gas or molecule across a membrane is:
    1) Proportional to the area of the membrane (A)
    2) Inversely proportional to the thickness of the membrane (d)
    3) Proportional to the difference in concentration (ΔC) or partial pressure (gas equivalent of concentration) (ΔP)

R = DAΔP/d

where D is a molecule-specific diffusion constant, which accounts for the size of the molecule, membrane permeability and temperature

36
Q

Structures of the Respiratory System: Upper

A
  • Nose

- Pharynx (throat)

37
Q

Alveolar Type 1 Cell

A
  • Simple squamous epithelial cells
  • Predominant
  • Long cytoplasmic extensions
  • Site of gas exchange
38
Q

Chemoreceptor Receptor Response - Negative Feedback

A

a) a rise in arterial PCO2 stimulates chemoreceptors that accelerate breathing cycles at the inspiratory centre. This change increases the respiratory rate, encourages CO2 loss at the lungs and lowers arterial PCO2
b) A drop in arterial PCO2 inhibits these chemoreceptors in the absence of stimulation the rate of respiration decreases, slowing the rate of CO2 loss at the lungs, and elevating arterial PCO2

39
Q

Pressure-volume changes during ventilation

A
  • Intrapleural pressure (Pip) is always negative

- Hence there is always a transpulmonary pressure gradient across lung wall keeping the lung open

40
Q

Forced expiratory volume in one second

A

Volume of air that can be expired during the first second of expiration in a VC determination

41
Q

Factors Affecting Pulmonary Ventilation: surface tension of alveolar fluid

A
  • surfactant reduces surface tension of water

- low surface tension increases compliance and decreases elastance

42
Q

Functional Residual Capacity

A

Volume of air in lungs at end of normal passive expiration (FRC = ERV + RV)
Ave. Value: 2200mL

43
Q

Factors Affecting Pulmonary Ventilation: Lung compliance

A
  • How much effort (force) required to deform a body

- Less compliant = more work (increase pressure) required to produce a given degree of inflation

44
Q

Chemical Control

A
  • Regulates O2 consumption and CO2 production
  • PCO2 detection is indirect via pH (i.e. H+) in cerebrospinal fluid
  • Detection of arteial PO2 and H+
45
Q

Oxygen Transport

A

Most O2 in blood transported bound to haemoglobin

Hb + O2 HbO2

Gas: O2
Method of Transport in Blood: Physically dissolved
% Carried in the Form: 1.5
Gas Content in mL/1000mL arterial blood: 3

Method of transport in blood: bound to haemoglobin
% Carried in the Form: 98.5
Gas Content in mL/1000mL arterial blood: 197

46
Q

Blood Supply to the Respiratory Surfaces

A
  • Each lobule receives an arteriole and a venule:
    > Respiratory exchange surfaces receive blood from arteries of pulmonary circuit
    > A capillary network surrounds each alveolus (as part of the respiratory membrane)
    > blood from alveolar capillaries: passes through pulmonary venules and veins and returns to left atrium
47
Q

3 Processes of Respiration: Internal Respiration

A
  • Also called cellular respiration

- Involves the uptake of O2 and production of CO2 within individual cells

48
Q

Alveolar Macrophages

A

Wandering phagocytes that remove dust and debris

49
Q

Expiratory Reverse Volume (ERV)

A

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
Ave. Value: 1000mL

50
Q

Oxygen - Haemoglobin Saturation Curve

A
  • The haemoglobin saturation curve is determined in vitro in the laboratory

Increasing part of curve: room for additional O2 to be liberated for diffusion into actively metabolising cells (e.g. during exercise)

Middle part of curve: Hb is only 75% saturated at PO2 of 40mmHg (tissues at rest). O2 must dissociate from Hb can then diffuse down partial pressure gradient into cells

Plateau: Amount of O2 unloaded to tissues

51
Q

3 Processes of Respiration: Pulmonary Ventilation (Breathing)

A
  • Physical movement of air into and out of respiratory tract
52
Q

Physiological significance of the O2 - Hb saturation curve

A
  • Plateau region
  • Hb in systemic blood normally saturated
  • Good-safety margin in the oxygen-carrying capacity
  • Unless PO2 drops below 60mmHg, near-normal amounts of O2 can still be carried to cells
53
Q

Partial Pressures - Dalton’s Law

A

Each gas in a mixture exerts a pressure according to its own concentration, independently of the other gases present (Dalton’s law)
E.g. partial pressure of each gas = total pressure x fractional composition of gas in the mixture
- At lungs and tissues - simple diffusion of O2 and CO2 occurs down partial pressure gradient

54
Q

Respiratory Control centres

A

Two groups of neurons in medullary centre

  • Dorsal Respiratory Group (DRG)
  • Ventral Respiratory Group (VRG)

The neurons of the pons adjust breathing rate and depth (fine tuning) to match metabolic demands

55
Q

3 Processes of Respiration: summary

A
  • Pulmonary ventilation (breathing)
  • External respiration
  • Internal respiration
56
Q

Total lung capacity

A

Maximum volume of air that the lungs can hold (TLC = VC + RV)
Ave. Value: 5700mL

57
Q

Diffusion of a Gas in a liquid - Henry’s Law

A

a) Increases the pressure drives gas molecules into solution until an equilibrium is established
b) when the gas pressure decreases, dissolved gas molecules leave the solution until a new equilibrium is reached

At equilibrium the partial pressure of the gas molecules in the liquid and gaseous phases will be identical

Therefore …

  • If a liquid is exposed to two different gases with the same partial pressure, then
  • at equilibrium, the partial pressures of the two gases in the liquid will be equal, BUT
  • the concentrations of the gases in the liquid will be different, depending on their solubility!

i.e. partial pressures are not the same as concentrations when talking about gases in liquids!
Solubilities of gases differ markedly:
CO2 is 20x more soluble than O2

58
Q

Composition and Partial Pressures of Normal Air: Partial pressure for each gas

A 
Partial pressure for each gas
AIR:
Nitrogen: 78.6% | 597mmHg
Oxygen: 20.9% | ~160mmHg
Carbon Dioxide: 0.04% | 0.3mmHg
Water: 0.46% | 4.2mmHg
OXYGEN:
Nitrogen: 75.4% | 573mmHg
Oxygen: 13.2% | 100 mmHg
Carbon Dioxide: 5.2% | 40mmHg
Water: 62% | 47mmHg
59
Q

Respiratory Membranes: Gas Exchange Surface

A
  • Respiratory membranes form diffusion barrier
    3 Parts
    1) Squamous epithelial lining alveolus
    2) Endothelial cells lining an adjacent capillary
    3) Fused basal laminae between alveolar and endothelial cells
  • Diffusion very rapid: distance is short and gases are lipid soluble
60
Q

Vital Capacity

A

Maximum volume of air that can be moved out during a single breath following a maximal inspiration
VC = IRV + TV + ERV
Ave. Value: 4500mL

61
Q

Alveoli

A
  • Cup-shaped pouch
  • Alveolar Type 1 Cell
  • Alveolar Type 2 cell
  • Alveolar macrophages
62
Q

Residual Volume

A

Minimum volume of air remaining in the lungs even after a maximal expiration
Ave. Value: 1200mL

63
Q

Physical and Chemical factors alter Haemoglobin’s Affinity for Oxygen

A
  • Shifting of curve to right: increases unloading of O2 from Hb
  • Shifting of curve to left: decreases unloading of O2 from Hn
  • Effect of pH known as the Bohr effect (mainly due to CO2)

Most important chemical equation in respiration and acid-base balance - when CO2 is in solution in plasma:

CO2 + H2O H2CO3 H+ + HCO3-

Therefore, CO2 in an important determinant of pH: increased plasma CO2 decreases pH

64
Q

Laryngopharynx (inferior)

A

Extends from hyoid bone to entrance of larynx and esophagus

65
Q

Factors Affecting Pulmonary Ventilation: Elastance (=elasticity)

A
  • Inverse of compliance; how readily lungs rebound after being stretched
  • Due to elastic fibres and surface tension
66
Q

Central Chemoreceptors

A
  • detect changes in pH in the cerebrospinal fluid caused by changes in arterial PCO2 (CO2 freely diffusible across blood - brain barrier)
67
Q

Pressures Important in Ventilation: Intrapleural Pressure (P ip)

A
  • ~756mmHg
  • Lower than atmospheric and intrapulmonary pressure
  • Due to elastic lung
  • Difference -4 mmHg
68
Q

Partial pressure of gases in lung and blood

A

VENOUS BLOOD (SYSTEMIC)
PO2: 40mmHg
PCO2: 46mmHg

ALVEOLUS
PO2: 100mmHg
PCO2: 40mmHg

ARTERIAL BLOOD (SYSTEMIC)
PO2: 95mmHg*
PCO2: 40mmHg

  • Alveolar pO2 and pCO2 equilibrate with blood in pulmonary capillaries alveolar ≈ arterial gases
  • Some mixing of deoxygenated blood from lung supply reduces PO2 of pulmonary venous and systemic arterial blood
  • Nitrogen is most abundant gas, but it is inert and does not change, i.e. ~560 mmHg in all compartments
69
Q

How does the lung move with the thoracic cavity?

A
  • No skeletal muscle in lung tissue
  • Has to move with thoracic cavity
  • 2 critical factors:
    1) cohesive forces of intrapleural fluid
    2) transpulmonary pressure gradient across lung wall
70
Q

What drives pulmonary ventilation?

A
  • Pressure and airflow: airflows from area of higher pressure to area of lower pressure
  • Pulmonary ventilation: volume of thoracic cavity changes > with expansion or contraction of diaphragm on rib cage - volume changes create changes in pressure
71
Q

Primary Functions of the Respiratory System

A

1) Provides extensive gas exchange surface area between air and circulating blood
2) Moves air to and from exchange surfaces of lungs
3) Protects respiratory surfaces from outside environment
4) Produces sounds
5) Participates in olfactory sense

72
Q

The lung lobes

A
  • Right lung: three lobes that are separated by horizontal and oblique fissures
  • Left lung: two longs that are separated by oblique fissure and has a cardiac notch
73
Q

Lower Respiratory Tract: Bronchi

A
  • Bronchial tree - 23 generations - progressively smaller
  • Primary bronchus: branches to form secondary bronchi (lobar bronchi), one secondary bronchus goes to each lobe
  • secondary bronchi: branch to form tertiary bronchi, also called the segmental bronchi, each segmental bronchus supplies air to a single bronchopulmonary segment
74
Q

Pulmonary Ventilation: Exhalation

A

Passive process
- relaxation of muscles, elastic recoil of chest wall and lungs to due:
> recoil of elastic fibres
> inward pull of surface tension of alveolar fluid
- volume decreases, intrapulmonary pressure increases > air flows out

75
Q

Gas Exchange

A

Exchange of O2 and CO2 between alveolar air and blood occurs via passive diffusion

  • Fick’s Law
  • Dalton’s Law: Each gas in a mixture exerts its own pressure, i.e. the partial pressure, proportional to its concentration in the mixture
  • Henry’s Law: Quantity of gas that dissolves in a liquid is proportional to the partial pressure and solubility coefficient
76
Q

Pressures Important in Ventilation: Intrapulmonary Pressure (P pl)

A
  • At rest, no change in volume of the thoracic cavity
  • ~760mmHg
  • Difference in pressure is 50mmHg (at rest)
77
Q

Bronchioles: Dynamic airways

A
  • Trachea and primary bronchi: fairly rigid, nonmuscular tubes
  • However bronchioles: no cartilage, smooth muscle innervated by ANS and stimulated by circulating adrenaline
    Parasympathetic > bronchial constriction
    Sympathetic and adrenaline > bronchial dilation
  • Sensitive to local chemicals (e.g. oxygen and carbon dioxide)
  • dynamic > significant capacity to change diameter (affects airflow)
  • Important in disease (e.g. asthma)
78
Q

Ventral Respiratory Group

A
  • inspiratory and expiratory centre

- functions only in forced breathing

79
Q

Pulmonary Ventilation: Inhalation

A

Active process
- During quiet breathing, contraction of diaphragm and external intercostals expands thoracic cavity
> Decreases intrapulmonary pressure relative to atmospheric pressure
> Air flows down pressure gradient

80
Q

Respiratory Diseases

A

Obstructive lung diseases - characterised by difficulty to expire
> Emphysema
> Asthma
> Bronchitis

Restrictive lung diseases - characterised by difficulty to inspire
> Respiratory distress syndrome
> lung fibrosis

81
Q

Effect of Alveolar Ventilation on the Blood Gases

A

As alveolar ventilation increases, alveolar PO2 increases and PCO2 decreases. The opposite occurs as alveolar ventilation decreases

Human Physiology (8 decks)

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