Physiology

Question 1

Identify the different classes of airways and the two types of alveolar

Answer 1

type 1- allow for gas exchange
type 2- synthesise surfactant- this substance lowers surface tension, which keeps the alveoli from collapsing after exhalation and makes breathing easy

Question 2

List the functions of the respiratory system

Answer 2

Gas exchange, acid base balance, protection from infection and communication via speech

Question 3

Know the difference between pulmonary and systemic circulation

Answer 3

Pulmonary- collects oxygen from pulmonary vein and remove carbon dioxide from pulmonary artery
Systemic- delivers CO2 to the heart, from where it is then transported to the lungs via the pulmonary artery.

Question 4

Identify points of gas exchange between the respiratory and cardiovascular systems

Answer 4

During exercise- rate and depth of breathing speeds up and heart rate and force of contraction speeds up. Lungs obtain oxygen and heart delivers it to muscles. Breathing produces waste carbon dioxide and its removed via blood

Question 5

Understand why, and how, resistance to air flow varies across the respiratory tree

Answer 5

alveoli have least resistance to airflow as contraction decreases diameter=increases resistance relaxation= increases diameter= decreases resistance

Question 6

Name and explain the key terms used to describe the different lung volumes

Answer 6

TV- tidal volume (volume breathed in and out of lungs at each breath)
ERV- expiratory reserve volume- maximum volume of air that can be expelled at end of normal expiration
IRV- Inspiratory reserve volume- maximum volume of air which can be drawn into lungs at end of normal inspiration
RV- residual volume- volume of gas in lungs at end of maximal expiration

Question 7

Describe the anatomy of the pleural cavity

Answer 7

lungs and inferior of thorax are covered by pleural membranes between the surfaces of these are an extremely thin layer of intrapleural fluid

Question 8

Describe the relationship between the parietal and visceral pleura and why this is important for inflation and deflation of the lung

Answer 8

Visceral lines outer surface of lungs and parietal lines inner surface of ribs

visceral pleura is stuck to the parietal pleura via cohesive forces of the pleural fluid. so lungs are stuck to ribcage

Question 9

Describe how the muscles of respiration act to increase and decrease thoracic volume

Answer 9

Inspiration uses external intercostal muscles and the diaphragm (contracts)
Expiration is passive at rest but uses internal intercostal and abdominal muscles during severe load

Question 10

Relate Boyle’s law to the mechanics of breathing, inspiration and expiration

Answer 10

occurs because thoracic cavity changes volume
increased volume= decreased pressure

Question 11

State the mechanical factors that affect respiratory minute volume.

Answer 11

lateral and anterior- posterior movement of ribcage

Question 12

Explain why intrapleural pressure is always less than alveolar pressure

Question 13

State the role of pulmonary surfactant and the Law of Laplace

Answer 13

reduces surface tension on alveolar surface membrane thus reducing tendency for alveoli to collapse. surface tension occurs where ever there is an air-water interface and refers to the attraction between water molecules

P= 2T/r 2 times surface tension divided by radius

Question 14

Define the term compliance the factors that affect this

Answer 14

change in volume relative to change in pressure. diseases and ages effect compliance
high compliance- means lots of air getting into lungs with only a small pressure

Question 15

what does the pulmonary artery carry

Answer 15

deoxygenated blood

Question 16

what does the pulmonary vein carry

Answer 16

oxygenated blood and has low carbon dioxide

Question 17

pharynx

Answer 17

from nose air moves down pharynx

Question 18

epiglottis

Answer 18

small flap that folds over trachea and prevents food from entering when you swallow

Question 19

larynx

Answer 19

voice box

Question 20

trachea

Answer 20

made up of stiff rings of cartilage

Question 21

bronchus

Answer 21

air moves from trachea into bronchi

Question 22

what structures are part of the upper respiratory tract

Answer 22

pharynx, larynx, oesophagus

Question 23

what structures are part of the lower respiratory tract

Answer 23

trachea, lungs, bronchus and diaphragm

Question 24

splitting of primary bronchi

Answer 24

right bronchus splits 3 times and the right bronchus splits 2 times

Question 25

alveolar

Answer 25

Only site of gas exchange and are very thin and have a large surface area

Question 26

what does anatomical dead space mean

Answer 26

air in airways that isn't involved in gas exchange e.g trachea and bronchus

Question 27

lung capacities

Answer 27

VC- vital capacity= tidal volume + IRV + ERV TLC= total lung capacity IC- inspiratory capacity= tidal volume + IRV FRC- functional residual capacity= ERV and RV

Question 28

alveolar pressure

Answer 28

pressure in the thoracic cavity. Can be negative or positive depending on atmospheric pressure

Question 29

intra-pleural pressure

Answer 29

pressure inside the pleural cavity. typically negative

Question 30

transpulmonary pressure

Answer 30

differences between alveolar and intra-pleural pressure. always positive

Question 31

Describe the structure and function of the diaphragm

Question 32

Understand the functional difference between pulmonary and alveolar ventilation

Answer 32

pulmonary ventilation- total air movement into/out of lungs alveolar ventilation- fresh air getting to alveoli and therefore available for gas exchange

Question 33

Be able to describe the impact dead space has on alveolar ventilation

Answer 33

air in dead space is used first before taking air from alveolar. found in trachea and bronchi

Question 34

Know the normal values for alveolar and arterial gas partial pressures in different units

Answer 34

alveolar- 100mmHg/13.3kPa of oxygen and 40mmHg/5.3kPa of carbon dioxide

Question 35

Be able to describe the blood supply to the lungs

Answer 35

bronchial circulation supplies oxygenated blood to the lungs pulmonary circulation supplies dense network of capillaries surrounding the alveolar and returns oxygenated blood to the left atrium.

Question 36

Be able to describe the factors that are proportional to diffusion of gases across the alveoli

Answer 36

partial pressure gradient gas solubility surface area availability

Question 37

Know the abbreviations used to describe the partial pressure of gases in the alveoli, systemic arteries and veins

Answer 37

A= alveolar a= arterial blood v=mixed venous blood

Question 38

Outline the basic characteristics of obstructive and restrictive lung diseases.

Answer 38

obstructive- obstruction of air flow, especially on expiration e.g asthma, COPD, chronic bronchitis, emphysema restrictive- restriction of lung expansion especially inspiration e.g fibrosis, infant respiratory distress syndrome, oedema, pneumothorax

Question 39

Outline how spirometry can be used to identify abnormal lung function.

Answer 39

static- consideration made about volume exhaled only dynamic- time taken to exhale a certain volume FEV1=4L (forced expiratory volume) FVC=5L (forced vital capacity)

Question 40

Describe and explain the characteristic results you would observe following lung function tests in patients with obstructive lung diseases

Answer 40

lower FEV1/FVC as rate of air exhaled in much slower

Question 41

what is hypoventilation

Answer 41

rapid and shallow breathing hypoventilation- P02 fails to 30 mm Hg and Pc02 rises to 100mm Hg

Question 42

what is hyperventilation

Answer 42

slow and deep breathing hyperventilation- Po2 rises to 120mm Hg and Pco2 falls to 20mm Hg

Question 43

Emphysema

Answer 43

Destruction of alveoli reduces surface area for gas exchange. Less diffusion so less oxygen can enter. inspiration is easier but expiration is harder because no elastic recoil. smoking produces elastase which breaksdown the elastic fibres, increased compliance whihc increases lung volume

Question 44

Fibrotic lung disease

Answer 44

Thickened alveolar membrane slows gas exchange. Resists stretch and makes lungs not expand during inhalation

Question 45

pulmonary edema

Answer 45

Fluid in interstiual space increases diffusion distance between alveoli and capillary. increased blood pressure forces plasma out of capillaries and it cools in interstitual space. co2 can be normal as more soluble

Question 46

Asthma

Answer 46

increased airway resistance decreases airway ventilation and therefore effects alveolar partial pressure of oxygen and carbon dioxide which limits diffusion

Question 47

differences between obstructive and restrictive diseases

Answer 47

obstructive- obstruction of air flow, especially on expiration e.g asthma, COPD, chronic bronchitis, emphysema restrictive- restriction of lung expansion e.g fibrosis, infant respiratory distress syndrome, oedema, pneumothorax

Question 48

Describe and explain the characteristic results you would observe following lung function tests in patients with restrictive lung diseases

Answer 48

FEV1 reduced and FVC reducesd as rate of airflow reduced as lung volume ratio remains normal or increases

Question 49

State the differences between partial pressure and gas content.

Answer 49

partial pressure describes amount of oxygen in solution in the plasma and not total oxygen concentration in the blood. however partial pressure determines total oxygen content of the blood by determining the saturation of haemogloblin

Question 50

Compare oxyhaemoglobin dissociation for adult haemoglobin with that of foetal haemoglobin and myoglobin in relation to their physiological roles.

Answer 50

myoglobin and foetal haemogloblin have a higher stauration for oxygen. as myogloblin wants more oxygen to deliver it ot the skeletal and cardiac muscles and foetal wants to take oxygen from mother

Question 51

Describe the relationship between ventilation and perfusion and its significance in health

Answer 51

Want them to be matched ventilation is the air getting to the alveoli perfusion is the local blood flow

Question 52

Describe the conditions under which there may be an imbalance in the ventilation- perfusion ratio of regions of the ratio of regions of the lung and describe how this affects the O2 and CO2 content of alveolar gas and arterial blood.

Answer 52

Both decrease with height At base of lung blood flow is higher than ventilation because arterial pressure exceeds alveolar pressure ventinaltionperfusion>1

Question 53

Define the terms shunt, alveolar dead space, physiologic dead space and anatomical dead space.

Answer 53

Shunt describes passage of blood through areas of lung that are poorly ventilated. alveolar dead space refers to alveoli that are ventilated but not perfused physiological dead space- alveolar dead space and anatomical dead space anatomical dead space- air unable to participate in gas exchange

Question 54

Define the five different types of hypoxia

Answer 54

Hypoxaemic- reduction in oxygen diffusion at lungs due to decreased partial pressure of oxygen in atmosphere or tissue pathology anaemic- reduction of oxygen carrying capacity in blood due to anaemia stagnant- heart disease results in inefficient pumping of blood to lungs and around body histotoxic- poisining prevents utilising oxygen delivery delivered to them e.g carbon monoxide metabolic hypoxia- oxygen delivery to tissues does not meet increased oxygen demand by cells

Question 55

Apply the concept of partial pressure gradients to the movement of O2 and CO2 between the blood and the alveoli

Answer 55

The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli.

Question 56

Describe the role of haemoglobin in the transport of O2 in the blood.

Answer 56

oxygen demand of resting tissues is 250ml/min but add haem you get 1000ml/min so only 25% of arterial oxygen is extracted by periheral tissues at rest The major determinant of the degree to which haemoglobin binds (is saturated with) oxygen is partial pressure of oxygen in the blood.

Question 57

Explain why the shape of the oxyhaemoglobin dissociation curve aids O2 loading in the lungs and unloading in the tissues.

Answer 57

haem is almost 100% saturated at normal systemic arterial partial pressure of 100mm Hg. even at 60mm Hg its still more than 90% saturated.

Question 58

Describe the factors that affect the oxyhaemoglobin dissociation curve.

Answer 58

Ph lower pushes curve to the right and oxygen has a lower affintiy so unloads oxygen increased temp pushes curve to the right and decreases affinity Pco2 increases pushes curve to right DPG present pushes curve to the right.

Question 59

Use anaemia to demonstrate how PaO2 determines, but is independent of, total blood oxygen content

Answer 59

In anemic patients, oxygen delivery decreases and oxygen extraction is increased. partial pressure of oxygen doesn't change

Question 60

Identify the forms in which CO2 is carried in the blood.

Answer 60

some dissolves in the plasma and erythrocytes combine with deoxyhemoglobin to form carbonic acid which yields bicarbonate and hydrogen ions. The bulk of carbon dioxide travels in bicarbonate ions because they get pumped back into plasma in exchange for carbon

Question 61

Explain the action of carbonic anhydrase in CO2 transport

Answer 61

An enzyme present in red blood cells, carbonic anhydrase, aids in the conversion of carbon dioxide to carbonic acid and bicarbonate ions.

Question 62

Identify the factors which favour CO2 unloading to the alveoli at the lungs.

Question 63

Explain how respiratory motor movements are affected by the central nervous system.

Answer 63

emotion- limbic system in the brain voluntary over-ride- via higher centres in the brain mechanic-sensory input from the thorax

Question 64

describe the location of the two classes of chemoreceptors and identify the stimuli which activate them.

Answer 64

central- medulla, responds directly to H+ generated as a result of an increased CO2 in CSF in brain, primary ventilatory drive. doesn't respond to direct changes in hydrogen conc of plasma peripheral- carotid and aortic bodies, respond to primary to Po2 and plasma H+, secondary ventilation drive

Question 65

List the factors involved in changing ‘respiratory drive’, rate and depth of breathing.

Answer 65

barbiturates and opioids depress respiratory centre- decreases sensitivity to pH and therefore response to pressure of CO2 also decreases peripheral chemoreceptor response to lower Po2 nitrous oxide blunts response to falling partial arterial pressure of oxygen

Question 66

Explain how the central chemoreceptors serve to regulate the arterial PCO2 by monitoring the pH of CSF.

Question 67

Explain how the peripheral chemoreceptors become important during hypoxia and acid-base imbalance.

Answer 67

Peripheral chemoreceptors monitor changes in arterial blood O2, and within seconds after the onset of hypoxia they trigger cardiorespiratory changes (i.e., increase in breathing and blood pressure), which are important for maintaining O2 homeostasis.

Question 68

Outline the role of the respiratory system in acid-base disturbances.

Answer 68

if plasma pH falls ventilation will be stimulates ventilation and if plasma pH increases ventilation will be inhibited

Question 69

Explain how CO2 affects acid-base balance

Answer 69

capable of changing ECF pH. hypoventilation causes CO2 retention and leads to increased H+ bringing about respiratory acidosis hyperventilation (blowing off more CO2) leads to decreased H+ bringing respiratory alkalosis

Question 70

Outline how the respiratory system can both create, and compensate for, acid-base disturbances.

Answer 70

pH is directly proportional to bicarbonate( controlled by kidneys)/ carbon dioxide (controlled by lungs)