Week 8 Flashcards
1
Q
What is the diaphragm attached to anteriorly?
A
Xiphoid process opposite T8/9
2
Q
What is the diaphragm attached to laterally?
A
Deep surface of ribs and costal cartilages 7-12
3
Q
What is the diaphragm attached to posteriorly?
A
- Median arcuate ligament T12 (between crura)
- Median Arcuate ligament (body of L1 tip of transverse process of L1)
- Lateral Arcuate ligament (tip of L1 transverse process to 12th rib)
- 2 Muscular crura
4
Q
Where is the left crus of diaphragm from?
A
Bodies of L1 & L2
5
Q
Where is the right crus of diaphragm from?
A
Bodies of L1, 2 & 3
6
Q
What passes through diaphragm at T8?
A
- IVC
- Right Phrenic nerve
7
Q
What passes through diaphragm at T10?
A
- Oesophagus
- Both Vagus nerves
- Left gastric vessels
8
Q
What passes through diaphragm at T12?
A
- Aorta
- Thoracic duct
- Azygos veins
9
Q
What happens during Quiet Inspiration: Contraction of diaphragm (1)?
A
- Flattens domes of diaphragm
- Increases vertical thoracic diameter
- Increases volume
- Decreases intrathoracic pressure
- Air is drawn into lungs
10
Q
What happens to the ribs and CC during Quiet Inspiration: Contraction of intercostal muscles?
A
Costal cartilages of ribs 5-10 pass obliquely upwards to the sternum, contraction of the intercostal muscles raise rib towards one above also lifts CC and pushes rib laterally
11
Q
What happens to rib 1 during Quiet Inspiration: Contraction of intercostal muscles?
A
No lateral movement of 1st rib
12
Q
What happens during Forced Inspiration?
A
- Bucket-handle
- Ribs 8-10
- Central tendon of the diaphragm is “anchored” by attachment to pericardium, further muscle contraction pulls the ribs and causes them to evert like lifting the handle of bucket
- Gives small increase in the lateral thoracic diameter & therefore the volume
- Air is drawn into the lungs by this additional decrease in intrathoracic pressure
13
Q
What 4 examples of Accessory Muscles can assist in both movements of inspiration and expiration when required?
A
- Pectoralis Major/Minor - inspiration
- Latissimus dorsi (compress ribs in forced expiration, raise ribs in forced inspiration)
- Abdominal wall muscles (raise intra-abdominal pressure to push
diaphragm up in forced expiration) - Neck and back muscles (trapezius, sternocleidomastoid, scalene
muscles) help to fix the ribs
14
Q
What type of respiration is external intercostal more active during?
A
Inspiration
15
Q
What type of respiration is internal intercostal more active during?
A
Expiration
16
Q
What is Mesothelium?
A
- Simple squamous epithelium
- Secretes small amount of serous fluid to lubricate the surfaces of viscera
17
Q
What are the surface marking of the Pleural cavity reflections?
A
- Rise to neck of 1st rib, 2cms above clavicle
- 2nd CC lie adjacent in midline
- 4th Left CC notch for the heart
- 6th CC deviate laterally
- 8th rib lie in midclavicular line
- 10th rib lie in midaxillary line
- 12th rib lie in mid scapular line
- Midline level with T12
18
Q
What are the Pleural Recesses?
A
- Costodiaphragmatic Recess- around periphery of diaphragm
2. Costomediastinal Recess- anteriorly, larger on the left
19
Q
What are Recesses?
A
Potential spaces and sites of accumulation of fluids
20
Q
Where is the Oblique Lung Fissure on both lungs?
A
- Spine of T4/body of T5
- Down across 5th rib
- Follow line of 6th rib around thorax
21
Q
What is the clinical possibility of the apical segment of the inferior lobe?
A
Pneumonia
22
Q
Where is the Horizontal Lung Fissure on right lung only?
A
- 4th CC
- Horizontally back across 5th rib
- Mett oblique issue in midaxillary line
23
Q
What does Surface tension of the Pleural membrane cause?
A
- Between Parietal & Visceral pleural “pulls” visceral layer with movements of thoracic wall
- Slight negative pressure that maintains lung in slight infiltration even at end of expiration
24
Q
What happens to Surface tension of Pleural Membrane when Air enters the Pleural cavity?
A
Surface tension & negative pressure are lost and lung collapses
25
What are the severe side effects of air entering the pleural cavity?
- No thoracic movement
- Elevated hemi diaphragm
- Shift of mediastinum to affected side
26
What is an example of Paradoxical Respiration?
- Fracture of ribs and sternum causing the whole segment to float freely ie. flail segment
- Inspiration the segment would be sucked inwards, instead of lifting upwards.
27
What does the ectoderm overlying the pharynx externally send during development?
- Pharyngeal grooves/clefts inwards towards the endodermal pharynx
- Most disappear but the first groove gives rise to the external auditory meatus
28
What is pharyngeal pouches?
Series of outgrowths which extend from the internal, endodermal aspect of the pharynx towards the grooves
29
Where does the pharyngeal membrane form?
Where the pharyngeal groove & pouch meet
30
What respiratory development occurs as a result of the cephalocaudal folding?
Endodermal tube of pharynx and oesophagus, septum transversum between thorax and abdomen
31
What/Where are the 6 pharyngeal arches?
- Each with core of mesoderm
| - Formed between each pharyngeal groove & pouch
32
What are the 6 pharyngeal arches have in them?
- Cartilaginous element (from neural crest cells)
- Artery (aortic arch)
- Nerve (cranial nerve)
33
What do the 6 Pharyngeal arches give rise to?
- Facial structures
- Mandible
- Tongue
34
What do the Pharyngeal pouches give rise to?
- 1st to the tympanic cavity
- 2nd to tonsils
- 3rd to thymus
- 3rd & 4th to parathyroid glands
35
What is the epithelium of the respiratory tract derived from?
Endoderm
36
What is cartilage, vasculature and muscle derived from?
Overlying Mesoderm
37
What is the respiratory diverticulum and when is it formed?
- Ventral outgrowth from foregut (endoderm) early in the 4th week
- Develops as the laryngotracheal groove in the floor of pharynx
38
What does the septum transversum seperate?
Heart in pericardial cavity and GI in peritoneal cavity
39
Where is the laryngeal orifice derived from?
Laryngotracheal groove
40
What does the tracheo-oesophageal septum do?
Separates the lung bud (trachea) ventrally from the gut tube (oesophagus) dorsally, leaving only the connection of larynx to pharynx
41
Give examples of the abnormalities that can occur in trachea-oesophageal septum?
- Oesophgeal atresia
| - Tracheo-oesophageal fistulas (TEFs)
42
What is 90% of Trachea-Oesophageal Fistula (TEF) cases?
Upper oesophageal atresia and fistula between lower oesophagus and the trachea
43
What amniotic fluid complication can occur as a result of oesophageal atresia?
Polyhydramnios (excess amniotic fluid)
44
What other defects are linked with TEF's?
- Renal
- Cardiac
- Vertebral
- Ano-rectal
45
What structures are first to develop from the respiratory diverticulum for the lungs?
2 bronchial buds (week 5)
46
What will the pericardio-peritoneal cavities become?
Pleural cavities
47
How many secondary bronchi are on the left and right?
- Left: 2
| - Right: 3
48
What do the 2 bronchial buds do?
- Subdivide into lung buds and push towards the pericardio-peritoneal canals
- Also "picking up" mesoderm to become cartilage, muscle, vasculature and pleura
49
How many tertiary bronchi are on the left and right?
10 on both
50
When does the tertiary bronchi become the segmental bronchi?
End of 24 weeks
51
Which structures are associated with the same mesoderm, resulting in them all having C3,4,5 supply?
Pleura, developing pericardium and septum transversum
52
What are the 4 Stages of lung development?
1. Pseudoglandular
2. Canalicular
3. Terminal Saccular
4. Alveolar
53
When does Pseudoglandular stage of lung development occur?
What does it consist of?
- 6-16 weeks
- Major elements formed upto terminal bronchioles (not those involved with gaseous exchange and therefore not compatible for life)
54
When does Canalicular stage of lung development occur?
What does it consist of?
- 16-26/28 weeks
- Terminal bronchioles have 2/3 respiratory bronchioles, which branch to form 3-6 alveolar ducts
- Become increasingly well vascularised
- Not compatible for life
55
When does Terminal Saccular stage of lung development occur?
What does it consist of?
- 24/26-36 weeks/birth
- Thin walled sacs (primordial alveoli) lined by squamous epithelial type 1 pneumocytes become well vascularised and across which gaseous exchange can occur
- From 20 weeks type 2 pneumocytes begin to secrete surfactant but there is wide individual variation
- At 28 weeks 1000gram babies can survive
56
When does Alveolar stage of lung development occur?
What does it consist of?
- 28-36 weeks, birth and into childhood (8 yrs)
- 50 million alveoli at birth
- However 5/6 of alveoli develop postnatally
- No increase in size, increase in numbers of alveoli
57
What is Surfactant?
Complex mixture of phospholipids that reduces the surface tension and facilitates expansion of the alveoli
58
What are the 3 Necessities in lung development for foetal survival?
1. Close association of thin walled alveolar ducts and alveoli with...
2. Rich capillary bed
3. Surfactant
59
What is Respiratory Distress Syndrome (RDS)?
- Deficiency of surfactant resulting in collapse of alveolar wall during expiration
- Also known as hyaline membrane disease
60
How has the mortality associated with Respiratory Distress Syndrome (RDS) been decreased?
Artificial surfactant & glucocorticoids to stimulate surfactant secretion
61
What is the Septum Transversum?
- Lies between pericardial/thorax & peritoneal/abdomen cavities
- Is a thick plug of mesoderm
- Contains myoblasts from somites in C3/4/5
62
What are the Diaphragms 4 sources of origin?
1. Septum Transversum- central tendon of diaphragm
2. 2 pleuroperitoneal membranes project towards and fuse with the septum transverse and close the pericardia-peritoneal canals
3. Mesentery of the oesophagus from which the crura develop
4. Ingrowth from the body wall
63
What can occur if the components of the diaphragm don't fuse properly?
Congenital Diaphragmatic Hernia
64
What is the name of the posterolateral hernia of the diaphragm?
Bochdalek Hernia
65
What is the name for an anterior hernia of the diaphragm?
Morgagni Hernia
66
What is intrapulmonary pressure?
Pressure within Alveoli
67
What is Intrapleural pressure?
- Always more negative than alveolar
| - Elastic nature of lung tissue versus ribcage and thorax trying to pull apart visceral from parietal pleura
68
What is the usual value for intrapleural pressure?
-4mmHg
69
What is the usual value of intrapulmonary pressure?
760 mmHg
70
What is the normal tidal volume?
500ml per inspiration
71
How much does intrapleural pressure drop in inspiration?
approx -6mmHg
72
How much does intrapulmonary pressure drop by in inspiration?
approx 1mmHg
73
What is the role of the diaphragm in respiration?
- Main muscle
- Contraction flattens domes
- Abdominal wall relaxes to allow abdominal contents to move downwards
74
What is the role of intercostal muscles in respiration?
- Forward movement of lower end of sternum
| - Upward and outward movement of ribs
75
What is the accessory muscle in forced inspiration?
Trapezius
76
Describe what happens during Quiet Expiration?
- Passive
- Cessation of muscle contraction
- Elastic recoil (air out of lungs)
- Thoracic volume decreases by 500ml
- Intrapulmonary pressure increases
- Air moves down pressure gradient
77
Describe what happens during forced expiration?
- Contraction of abdominal walls, forces abdominal contents up against diaphragm
- Internal intercostals pull ribs downwards
78
What is energy used to do regarding breathing?
- Contract muscles of inspiration
- Stretch elastic elements
- Overcome airways resistance
- Overcome frictional forces arising from viscosity of lung and chest wall
- Overcome inertia of the air and tissues
79
Where does 75% of energy expenditure in breathing go?
In quiet breathing, contraction of diaphragm
80
What is the most significant non-elastic source of resistance?
Airway resistance
81
How is the amount of air that flows (F) calculated?
ΔP/R
82
What 2 factors predisposes turbulent flow?
1. High velocity
| 2. Large diameter airways
83
Where is the greatest resistance to airflow?
Why?
- Segmental bronchi
| - Cross sectional area is relatively low and airflow is high and turbulent
84
Which stage of respiritory cycle is airway resistance decreased?
Inhalation
85
What is the airway resistance in asthma patients?
| Why?
Inflammatory mediators change smooth muscle tone and narrow airways leading to increased resistance
86
What is the definition of Compliance?
- Describes the distensibility/ ease of stretch of lung tissue when external forces applied
- Or ease with which the lungs expand under pressure
87
What are the major determinants of compliance?
- Elastic components
| - Alveolar surface tension
88
What is the compliance of a healthy individual?
approx 1L per kPa
| 1L per 7.5mmHg
89
How can compliance be reduced?
- Replacing elastic tissue with non-elastic (pulmonary fibrosis)
- Blocking smaller respiratory passages
- Increasing alveolar surface tension
- Decreasing the flexibility of the thoracic cage/its ability to expand
90
How can compliance be increased?
- Alveoli rupture, creating larger air spaces & reducing surface area of the lung (pulmonary emphysema)
- Impaired elastic recoil leads to poor deflation, trapping more air
91
Which lung volume is compliance the highest?
Low volume
92
Which part of lung has the greatest compliance and why?
- Base of lung
| - Compressed by surrounding tissues, so volume is less, so can expand more than the apex
93
What makes up the Alveolar surface tension?
- Due to polar nature of water (pure water=collapse)
| - Presence of surfactant prevents alveolar collapse pressure
94
Name Respiratory Volumes & Pulmonary Function Tests?
- Spirometry (can't measure residual volume)
- Vitalograph
- Peak flow meter
95
What is Tidal Volume (TV)?
Volume of air breathed in and out in a single breath (0.5L)
96
What is Inspiratory Reserve Volume (IRV)?
Volume breathed in by max inspiration at end of normal inspiration (3.3L)
97
What is Expiratory Reserve Volume (ERV)?
Volume of air expelled by max effort at the end
| of normal expiration (1 L)
98
What is Residual Volume (RV)?
Volume of air in lungs at the end of maximum expiration ( 1.2 L)
99
What is Inspiratory capacity (IC)?
- TV + IRV
| - Volume of air breathed in by max inspiration at the end of a normal expiration (3.8 L)
100
What is Functional Residual Capacity (FRC)?
- ERV+RV
- Volume of air left in lungs at end of normal expiration. - Buffer against extreme changes in alveolar gas levels in each breath (2.2-2.4 L)
101
What is Vital capacity (VC)?
- IRV+TV+ERV
| - Volume of air that can be breathed by max inspiration following a max expiration (4.8 L)
102
What is the anatomical definition of Dead Space?
Areas of airway not involved in gaseous exchange
- Nose, mouth, pharynx, larynx, trachea, bronchi, bronchioles (little bit of alveolar aswell in physiological definition!)
103
How much ventilation occurs at dead spaces?
approx 150ml
104
How much ventilation occurs in alveoli?
approx 5ml
105
What does high compliance mean?
There is a large change in volume for a given change in pressure
106
What is FEV1 and what measures it?
- Forced exhalation volume per second
| - Vitalograph measures it
107
What is the characteristics of Respiration?
- Automatic
- Rhythmic
- Adapts to meet changing requirements
108
What happens to the activity of inspiration neurons during Inspiration?
- Activity increases steadily
| - Through positive feedback mechanism
109
What happens to the activity of inspiration neurons at the end of Inspiration?
Activity shuts off abruptly and expiration takes place through recoil of elastic lung tissue
110
Do respiratory muscles have/have not got intrinsic rhythmicity?
- HAVE NOT
| - Unlike heart
111
What contains all the components to generate a rhythmic pattern of respiration?
The brainstem
112
Where is the respiratory rhythm generated?
In the Medulla
113
What 2 mechanisms regulate respiration?
1. Nervous/Neural
| 2. Chemical
114
What are respiratory "centres"?
They are diffuse networks, possibly at higher density which are active together to bring about the respiratory effect
115
Where and what do the respiratory centres do?
- Located in medulla oblongata and pons
- Collect sensory information about levels of oxygen and carbon dioxide in blood that determines the signal sent to respiratory muscles
- Stimulation of these muscles provides respiratory movements which produce alveolar ventilation
116
What are the 2 Medullary Respiratory Centres called?
1. Inspiratory centre
| 2. Expiratory centre
117
Where and what does the Inspiratory centre do?
- Located in upper part of medulla oblongata
- Also called Dorsal Respiratory Group (DRG)
- Function is exclusively with inspiration
118
Where and what does the Expiratory centre do?
- Located in medulla oblongata, anterior and lateral to the inspiratory centre
- Also called Ventral Respiratory Group (VRG)
- Inactive during quiet breathing and when inspiratory centre is active, but during forced breathing or when inspiratory centre is inhibited it becomes active
119
What are the 2 Poutine Centres called?
1. Pneumotaxic Centre
| 2. Apnestic Centre
120
Where and what does the Pneumotaxic centre do?
- Located in upper Pons
- Controls medullary respiratory centres, especially the inspiratory centre through the apneustic centre
- Influences inspiratory centre so that duration of inspiratory is under control
121
Where and what does the Apneustic centre do?
- Located in lower Pons
| - Increases depth of inspiration by acting on inspiratory centre
122
How do respiratory Afferent pathways deliver impulses?
Via vagus & glossopharyngeal nerves
123
How does respiratory afferent signals occur?
- Respiratory centre gets impulses according movement of thoracic region and lungs
- Also from chemoreceptors
124
How does respiratory efferent signals occur?
- Nerves from respiratory centre leave brain in anterior part of lateral column in spinal cord
- Terminate in motor neurons in cervical and thoracic segments of spinal cord
- Supply phrenic nerve that controls diaphragm
- Supply fibres for intercostal muscles
125
What are the 10 Factors which affect respiratory centres?
1. Impulses from higher centres
2. Stretch receptors of lung slowly adapting pulmonary receptors
3. "J" receptors/pulmonary C-fibres
4. Irritant receptors of lungs
5. Proprioreceptors
6. Thermoreceptors
7. Pain Receptors
8. Cough Reflex
9. Sneezing Reflex
10. Deglutition reflex
126
What are impulses from higher centres and how does it affect respiratory centres?
- Limbic system, cerebral cortex, hypothalamus
| - Can stimulate/inhibit respiratory centres directly
127
What are "J" Receptors/Pulmonary C-fibres and how does it affect respiratory centres?
- Juxtacapillary receptors present in wall of alveoli
- Stimulated during conditions like pulmonary oedema, congestion, pneumonia. Also from endogenous chemicals such as histamine
- Stimulation induces apnea
128
What is Apnea?
Temporary suspension of breathing, followed by rapid shallow breathing
129
What are Irritant receptors of lungs and how does it affect respiratory centres?
- Rapidly adapting receptors
- Situated on walls of bronchi & Bronchioles
- Stimulated by chemicals like ammonia, cigarette
- Induces rapid shallow breathing, mainly from shortening of expiration
- But also, long deep augmented breaths, which are taken by mammals every 5-20mins on average to reverse slow collapse of lungs that occur during quiet breathing
130
What are Proprioreceptors and how does it affect respiratory centres?
- On chest wall
- Reflexes from muscles and joints to stabilise ventilation in the face of changing mechanical conditions
- Situated in joints
- Tendons detect stretch of muscle contraction
- Muscle spindles monitors length of fibres both statically and dynamically (length & velocity)
131
What are Thermoreceptors and how does it affect respiratory centres?
- Cutaneous
- Supply signals to cerebral cortex
- Stimulates respiratory centre
- Hyperventilation
132
What are Pain Receptors and how does it affect respiratory centres?
- Supply signals to cerebral cortex
- Stimulates respiratory centres
- Hyperventilation
133
What is Cough Reflex and how does it affect respiratory centres?
- Protect reflex caused by irritation of parts of respiratory tract beyond nose (larynx, trachea & bronchi)
- Stimulates vagus nerve
- Deep inspiration followed by forceful expiration with closed glottis
- Glottis opens and explosive outflow of air at high velocity
134
What is Sneezing reflex and how does it affect respiratory centres?
- Irritation of nasal mucous membranes
| - Deep inspiration followed by forced expiration with opened glottis
135
What is Deglutition reflex and how does it affect respiratory centres?
- Respiration arrested during swallowing of food
| - Swallowing apnea or deglutition apnea
136
What doe Chemoreceptors Respond to?
- Changes in chemical constituents of blood or CSF
- Hypoxia
- Hypercapnea: elevated CO2 in blood
- Increased H+ connection (decreased pH)
137
What are the 2 groups of chemoreceptors?
1. Central chemoreceptors
| 2. Peripheral chemoreceptors
138
Where and what do the Central Chemoreceptors do?
- Located in medulla oblongata close to DRG
- Sensitive to increase in H+ concentration
- H+ cannot cross BBB or CSF barrier
- CO2 can cross into CSF, form carbonic acid, which is unstable and rapidly dissociates to H+ and bicarbonate
- Sensitive to arterial PaCO2, not arterial H+
- NOT sensitive to PaO2
139
Why are central chemoreceptors sensitive to arterial PaCO2 and not arterial H+?
Because there is less protein in CSF than plasma a rise in PaCO2 can cause a larger effect on pH in CSF than in blood
140
Where and what do Peripheral Chemoreceptors do?
- Situated around carotid sinus and aortic arch
- Carotid bodies have the greater effect on respiratory
- Sensitive to PaO2, PaCO2 (but about 10x less sensitive than central receptors), pH, blood flow, temp.
141
What is CNS neuromuscular disorder?
Trauma to brain and spinal cord can cause partial or total loss of respiratory function
- Vasoconstriction, hypertension, mucus secretion, oedema can result from uncontrolled activity of airways innervation
142
What do Hemispheric strokes interfere with?
- Voluntary pathways of breathing
| - Brainstem strokes that affect dorsal medullary centres cause fatal apnoea
143
What is Poliomyelitis?
- Viral Disease can cause temporary or permanent paralysis
| - 25% require mechanical ventilation during acute phase
144
What is Diptheria?
Demyelinating neuropathy that can lead to respiratory failure
145
What is Botulism?
- Food poisoning
| - Innervation of respiratory muscles seems particularly vulnerable, ventilation may be required for extended period
146
What happens if the brainstem is cut above the level of the pons?
Basic rhythm continues
147
What is normal atmospheric pressure in mmHg and pascals?
- 760mmHg
| - 101kPa
148
What is the partial pressure of nitrogen?
593mmHg
149
What is the partial pressure of oxygen?
159mmHg
150
What is the partial pressure of carbon dioxide?
0.29mmHg
151
What happens to partial pressure when atmospheric pressure changes?
Partial pressure changes
152
What is Trimix?
Nitrogen, Oxygen & Helium
153
What is Heliox?
Oxygen & Helium
154
What is Henry's Law?
- When mixture of gases is in contact with liquid, each gas will dissolve in liquid in proportion with its partial pressure
- Absolute level of gas dissolved in a liquid also depends on solubility of the gas
155
What happens to the gas when the partial pressure in liquid becomes greater than air?
Gas will move out of liquid
156
Out of the atmospheric gases, which is the most soluble?
CO2
157
What is the total amount of gas in liquid when a chemical reaction occurs?
Total amount of gas in liquid is the amount dissolved plus that chemically bound in solution
158
Is alveolar gas same as atmospheric air?
NO
159
What is the pressure of the water vapour in the alveoli?
47mmHg
160
What is the alveolar partial pressure of O2?
104mmHg
161
What is the alveolar partial pressure of CO2?
40mmHg
162
What things is the rate of diffusion proportional to?
Surface area, solubility, concentration gradient, inversely proportional to tissue thickness and square root of molecular mass
163
What is the concentration gradient?
Difference in partial pressure
164
What is the partial pressure of oxygen in venous blood?
40mmHg
165
How much more soluble is CO2 than O2?
20x
166
How long does it take for a RBC to pass through pulmonary capillary at rest? Exercise? & Equilibrium?
REST- 1s
EXERCISE- 0.3s
EQUILIBRIUM- 0.25s
167
What is the partial pressure of PCO2 in venous blood?
45mmHg
168
What could be a cause of increase in thickness of respiratory membranes?
Oedema
169
What may cause decrease in surface area for gas exchange?
Emphysema
170
What may cause gas entry inhibition?
Gas exchange reduced by mucus, inflammation of airway, tumour
171
Explain how altitude increases RBC count?
- Lower atmospheric pressure, therefore lower partial pressure pO2
- Haemoglobin saturation reduced
- Increased erythropoietin release, compensation by increased Hb
172
What are problems associated with N2 bubbles?
- Lethal emboli
- Bubbles in pulmonary circulation
- Painful joints
- Stroke
173
How is decompression sickness treated in divers?
Hyperbaric chambers used to slowly decompress divers who surfaced too quickly
174
What are the problems associated with rapid ascension without exhaling?
- Volume of air in lungs increases (P1V1=P2V2)
- Causes rupture of alveoli and gas bubbles enter circulation
- Usually lodge in cerebral circulation
- Can cause Seizures, unconsciousness
175
What are the gas movements in the tissues?
- CO2 moves into blood from tissues
| - O2 moves out of blood into tissues
176
What are the 2 ways oxygen is carried in the blood?
1. Dissolved in plasma
| 2. Attached to haemoglobin
177
What are the O2 tissue requirements at rest?
250ml O2/min
178
How is O2 dissolved in plasma?
- Proportional to partial pressure
| - O2 poorly soluble
179
What does PO2 mean?
- Partial pressure of oxygen
| - Reflects amount of oxygen gas dissolved in the blood
180
How is O2 carried by haemoglobin (Hb)?
- Easily reversible combination: HbO2
- 4 binding sites
- Affinity of Hb for O2 increases with amount of O2 previously bound (Positive co-operative binding)
- Oxygen-haemoglobin dissociation curve with is sigmoidal
181
What is the percentage saturation of haemoglobin at tissues and what is the partial pressure of O2?
- Hb 75% saturated so you only lose 25%
| - 40mmHg
182
What is the significance of the flat upper plateau in Oxygen-haemoglobin dissociation curve?
If PO2 in lungs falls (low O2 environments), Hb saturation not greatly altered in lungs
183
What is the significance of the steep lower part of the Oxygen-haemoglobin dissociation curve?
In low O2 tissues, only small change in n PpO2 req. for a large unloading of O2 from haemoglobin
184
What is the significance of 25% of unloading in normal tissues?
Large reserve of O2 without even needing to increase Cardiac Output or respiratory rate
185
What factors shift the Oxygen-haemoglobin dissociation curve to the right?
Increased temperature, H+, CO2, 2,3-bisphosphoglycerate
186
How is the oxygen-haemoglobin dissociation curve moved to the right and what does this mean?
- Factors modify the structure of haemoglobin
| - Decrease Hb affinity for O2
187
What is the Bohr Effect?
Increased CO2 leads to an increase in H+ which weakens the Hb-O2 interaction
188
How is amount of O2 carried in blood worked out?
Amount of O2 carried by haemoglobin + amount dissolved
189
How is amount carried by Hb worked out?
Hb concentration in blood X max O2 carrying capacity of Hb X % saturation of Hb
190
What is the normal amount of Hb in blood?
15g/100ml
191
What is the normal capacity of Hb for carrying O2?
1.35 ml (O2)/g (Hb)
192
What is the % of saturation of Hb in 100ml of normal arterial blood?
98%
193
How is carbon dioxide transported in the blood?
1. Dissolved in plasma
2. Bound to haemoglobin
3. As bicarbonate
194
How much CO2 is dissolved into the plasma?
7-10%
195
How much CO2 is bound to haemoglobin?
10-20%
196
How does CO2 bind to haemoglobin?
- Carbaminohaemoglobin
- Binds to amino acids, not the haevx m so does not compete with oxygen
- Loading and unloading is directly related to PCO2 and degree of oxygenation of Hb
197
What is the Haldane Effect?
- Deoxygentation of Hb increases its ability to bind CO2
| - Oxygenation of Hb releases CO2 into plasma for transport into alveoli
198
How much CO2 is transported in blood as a bicarbonate?
70-80%
199
What is the chemical reaction of CO2 dissolving in water?
CO2 + H2O --> H2CO3 --> H+ + HCO3-
200
How is the conversion of CO2 to carbonic acid speed up?
Carbonic anhydrase in RBC
201
What happens as a result of increased H+ ?
Chloride shift: chloride ions move into RBC to restore electrochemical gradient
202
What happens in the lungs regarding CO2 travelling as bicarbonate?
- Reversed
- HCO3- moves back into RBC, reacts with H+ to form carbonic acid which is rapidly reacted by carbonic anhydrase to form CO2 & water
- CO2 diffuses into alveoli space
203
What equation can calculate the pH of blood?
Henderson-Hasselbach equation
204
What is the Henderson-Hasselbach equation?
pH=pK+ Log(bicarbonate)/CO2
205
What is the pK of bicarbonate?
6.1
206
Changing the levels of what will change the pH of blood?
CO2 or Bicarbonate
207
What is respiratory Acidosis?
If Ventilation decreases, CO2 increases, pH falls and HCO3- increases
208
What is respiratory Alkalosis?
If patient hyperventilates, blowing off more CO2, pH rises and the levels of HCO3- falls
209
What factors need to be closely matched in order to have effective gas exchange?
Ventilation & Perfusion
210
What is ventilation?
Change in volume through the respiratory cycle
211
Where does more gas go to in the lung during inspiration?
More goes to the base of the lung than the apex
212
Why does the base of the lung receive more gas than the apex?
- Lower ribs more curved & mobile
- Diaphragm expands lower lobes more
- Upper lobes are attached to main bronchi & upper airways so less easily stretched
- Lower lobes have greater compliance
- Weight causes apex to have more negative intracellular pressure, with so alveoli are more extended already
213
Which 2 circuits nourish lung tissue?
1. Pulmonary (approx 98% of blood to lungs)
| 2. Bronchial (approx 2% of blood to lungs)
214
Describe the Pulmonary blood flow?
- Respiratory Portion
- Pulmonary artery flow considered equal to cardiac output
- approx 5L enters each min
- Stroke volume is ~70ml
- Volume of pulmonary capillary network at rest ~100ml
-
215
Describe the Bronchial blood flow?
- Conducting portion, thus diluting oxygenated with deoxygenated blood slightly
- Bronchial arteries are branches of descending aorta
- Function to supply oxygen to lung parenchyma, airway smooth muscle pulmonary arteries, veins and pleura
- Also conditioning (warming) of inspired air
216
What is the pressure and resistance in pulmonary circulation?
Both LOW
217
What is the clinical relevance of how pulmonary capillaries are surrounded in air?
Can collapse or be extended according to balance of blood pressure and alveolar pressure (transmural pressure)
218
What is the mean arterial pressure in the lung?
~15mmHg
219
What is the distribution of blood flow in an upright position and why?
- Blood flow at apex is low
- Blood flow at base is large
- Due to hydrostatic pressure difference between base & apex ~23mmHg
- Pressure in capillaries is lower at apex than at base of lung
220
What are the consequences of the change in hydrostatic pressure at different levels of the lung?
In apex if alveolar pressure > blood hydrostatic pressure capillary will be closed
221
What are the 3 Zones of the lungs?
Zone 1- Apex (PA = Pa)
Zone 2- Middle (Pa > PA)
Zone 3- Base (Pa >> PA)
222
What happens when the capillaries are closed in zone 1 of the lungs?
Apex of lungs are ventilated but not perfused so are considered alveolar dead space
223
Why under normal conditions is there no Zone 1 in lungs?
Because there is sufficient pressure to perfuse the apices
224
How is the flow determined in Zone 2 of the lungs?
- Alveolar pressure (PA) is lower than systolic arterial pressure (Pa) but may be higher than diastolic arterial pressure and venous pressure
- Flow is determined by arterial alveolar pressure difference
225
How is the flow determined in Zone 3 of the lungs?
- Alveolar pressure (PA) is lower than both arterial pressure (Pa) and venous pressure
- Capillaries are distended as a consequence of the transmural pressure and there is continuous flow
226
What is the V/Q?
Ventilation (V) and Perfusion (Q) ratio
227
What is the V/Q ratio over the entire lung?
0.85
228
What is the V/Q ratio at base?
0.6
| more prefusion than ventilation
229
Where is V/Q ratio 1?
2/3 up the base
230
What is the V/Q ratio at apex of lung?
3
231
What are the 3 Main Scenarios of Ventilation and Perfusion matching?
1. Perfect matching- well ventilated alveoli, good perfusion of blood. Rich in O2, low in CO2
2. Poorly ventilated alveoli with rich blood supply- low PO2, high PCO2
3. Well ventilated alveoli, poorly perfused with blood- blood leaving alveoli will be low in CO2 but as Hb is fully saturated, no significant increase in O2 levels
232
What happens to lowered P02 of blood leaving poorly ventilated parts of the lung?
- NOT compensated for by blood leaving well ventilated areas
- Poorly ventilated areas have low O2 content
- Well ventilated areas have normal O2 content
233
Describe effect on CO2 conc. at low VQ ratio?
As ventilation low, CO2 not removed rapidly, CO2 accumuates in the alveoli and higher steady state PCO2 occurs
234
Describe effects on O2 conc. at low VQ ratio?
As ventilation low, O2 taken up by blood is not fully replenished by new air entering lungs, so O2 is depleted in alveolar air and a new steady state low PO2 occurs
235
Describe effects on CO2 conc. at high VQ ratios?
CO2 diffusing from blood nearly all blown away. CO2 nearly depleted from alveoli until a new lower steady state level occurs
236
Describe effect on O2 conc. at high VQ ratios?
O2 is not removed by blood as quickly so accumulates in alveoli.
Higher PO2 occurs
237
What does Hypoxic Vasoconstriction do?
- Intrinsic effect
| - Diverts blood away from poorly ventilated areas
238
Via which tract can lower motor neurone activity be affected by other upper motor neurones?
Corticospinal tract
239
During voluntary control of ventilation, where are signals coming from and going to?
Come from cerebral cortex, travel to medulla (influence DRG) or go directly to lower motor neurones (influence intercostals/diaphragm)
240
What is involuntary control of ventilation driven by?
Levels of O2, CO2, H+ in blood
241
What is a glomus type 1 cell?
Peripheral chemoreceptor cell located in carotid bodies and aortic bodies
242
What are glomus cells stimulated by?
Primarily Decrease in PO2, increase in H+ (caused by increase in CO2)
243
What do glomus cells synapse with?
Afferent nerves which run to brainstem, sensory portion cranial nerve X (vagus) from aortic bodies and cranial nerve IX (glossopharyngeal) from carotid bodies
244
Which of the 2 peripheral chemoreceptors is more important in respiration?
Carotid Body
245
Where are the central chemorecpetors located?
Ventro-lateral medulla
246
What are peripheral chemoreceptors sensitised by?
CO2 and pH
247
Describe what keeps the glomulus cell quiescent/inactive?
When PO2 is high, K+ channel is open and glomus cell is inactive (REFRACTORY)
248
Describe what happens when glomulus cell is activated
1. PO2 falls and K+ channel closes, cell membrane depolarises
2. Ca2+ channels open
3. Ca2+ influx triggers neurotransmitter release
4. Action potential travels along sensory afferents synpasing with glomulus cell
249
Where does the central chemoreceptor input go?
DRG (dorsal respiratory group)
250
What does CO2 do when it crosses BBB?
- Causes hypercapnea in blood
- pH of CSF decreases
- Excitatory input to DRG in medulla and resulting increased ventilation "blows off" CO2, reducing arterial PCO2
251
If CO2 is decreased (during hyperventilation) how is ventilation depressed?
- Normal PCO2 there is resting discharge action potential from chemoreceptors
- PCO2 falls the firing rate also falls so decrease in excitatory input to DRG, with result of respiration being inhibited
252
What chemoreceptors are sensitive to PO2?
- Peripheral chemoreceptors ARE
| - Central chemoreceptors are NOT
253
What must PO2 drop below to result in peripheral chemoreceptors becoming major stimuli for ventilation? What is the oxygen saturation of hB at this level?
- 60mmHg (13.3kPa)
| - 85%
254
What happens to peripheral chemoreceptors in COPD & why does this become a problem?
- Steady state PCO2 high due to poor ventilation
- Central & peripheral chemoreceptors become insensitive to PCO2
- Patient relies on peripheral stimulation from the low PO2 to stimulate breathing
- If you give these patients O2 (100%) breathing stops
255
What type of chemoreceptor controls change of pH if PCO2 is normal?
Stimulation of Peripheral chemoreceptors from PO2
256
What happens to ventilation if pH decreases?
Ventilation increases
