Respiratory System Flashcards
What is part of the conducting system?
Nasal cavities to the terminal bronchioles
What is part of the respiratory system?
Respiratory bronchioles to the alveoli
What type of epithelium is found in the trachea?
Psuedostratified, ciliated, columnar epithelium
Describe the pathway of the respiratory tree?
Trachea Primary bronchi Secondary Bronchi Tertiary bronchi Bronchioles Terminal Bronchioles Respiratory Bronchioles Alveolar Duct Alveolar Sac Alveoli
What type of epithelium is found in wide bronchioles?
Simple, ciliated, columnar
What type of epithelium is found in narrower bronchioles?
Simple cuboidal
What type of epithelium is found in alveoli?
Simple squamous
what are the pleurae?
Serous membranes that line the thoracic cavity and lungs
What are the two types of pleurae and how do they differ?
Parietal pleurae: lines the inside of the thoracic cavity. It is innervated by the phrenic and intercostal nerves. It is thicker.
Visceral pleurae: lines the lines, is not sensitive to pain, touch or temperature. Its sensory fibres only detect stretch.
where are the two pleurae continuous with one another?
AT the hilum of the lung
What is the space between the pleurae and what doe sit contain?
Pleural cavity, it contains pleural fluid
What does the pleural fluid do?
To provide lubrication to reduce the friction between the two layers
To create surface tension
What are the surfaces of the lungs?
Costal, Mediastinal, diaphragmatic
What provides venous drainage of the lungs and what does it split into?
bronchial veins.
They split into the azygous vein on the right and the accessory hemiazygous vein on the left
What is the point at which the trachea bifurcates called?
Carina
What is the structure of the trachea?
C shaped hyaline cartilage rings – which hold open the airway. They lie anteriorly.
Trachealis muscle lies posteriorly which adjusts the width of the trachea to control air flow and is flexible with the oesophagus.
Which one is anterior, the trachea or the oesophagus?
Trachea
Briefly describe the layers of the trachea?
Top layer = respiratory epithelium (psuedostratified, ciliated, columnar) which has goblet cells that secrete mucous. Submucosa contains seromucous glands which produce a watery mucus secretion.
What is different in the structure of trachea and bronchi?
Bronchi have cartilage arranged as irregular plates
What is the difference between the left and right primary bronchi?
Right bronchus is shorter and more vertical
WHAT CHANGES occur in the structure as the primary bronchi splits into secondary ?
Cartilage rings becomes smaller and fewer
What are bronchioles made up of?
They do not contain cartilage and are made up of smooth muscle
what is the function of type 1 pneumocytes and describe them?
Type 1: primarily involved in gas exchange. They are flat cells with a thin cytoplasm.
They cover 95% fo the surface
what is the function of type 2 pneumocytes and describe their shape?
They produce surfactant to reduce surface tension of the alveoli. They are also progenitor cells.
They are cuboidal
Describe the effect which breathing has on pressure on the thoracic cavity?
Upon inhalation: contraction of the respiratory muscles increases the size of the thoracic cavity. This causes a decrease in interpulmonary pressure and causes air to move in from area of high pressure to low pressure, so from outside into the lungs.
Upon exhalation: relaxation of the respiratory muscle decreases the size of the thoracic cavity. This increases the interpulmonary pressure and causes air to move out of the lungs.
Describe the process of gas exchange in the alveoli
Pulmonary arteries carry deoxygenated blood from the heart to lungs where it branches into a network of pulmonary capillaries that cover the alveoli.
Pulmonary capillaries fuse their basement membrane with alveoli to reduce the distance between RBCs and Oxygen.
The partial pressure of oxygen in the pulmonary capillaries is low at 40 mm Hg and high for CO2 at 46 mm Hg.
When air is breathed in, it has a high partial pressure for oxygen of 102 mm Hg and low PP of CO2 at 40 mm Hg.
Gas exchange in alveoli is driven by the difference in partial pressures of oxygen and Co2 in the pulmonary capillaries and alveoli. Each gas diffuses down their concentration gradients and moves from an area of high partial pressure to low PP.
Oxygen moves from alveoli to pulmonary capillaries and CO2 moves from pulmonary capillaries to alveoli.
Describe the neural and chemical factors involved in control of breathing?
Chemoreceptors: detect changes in PP of oxygen, CO2 and pH
Peripheral - found in carotid sinuses and aortic arch. These detect changes in PP of oxygen and send signals to the NTS in the brainstem via vagus nerve and glossopharyngeal nerve.
Central - responds to changes in PP of CO2
Neural signal sent from neuronal clusters in the brainstem to neuronal clusters in brainstem involved in breathing.
Mechanoreceptors - detect changes in stretch, pressure and movement of lungs and thoracic wall. Send signals via the vagus nerve to NTS.
what is a pneumothorax?
A collection of air/gas in the pleural cavity
Explain the mechanism of a pneumothorax
The air removes the surface tension of the pleural fluid, reducing lung extension. This causes the lungs to collapse, impairing lung function.
Explain the 2 main classes of pneumothorax
Spontaneous:
Primary = no underlying respiratory condition. Occurs due to the tear of a small bleb (Bleb is a small balloon of tissue that develops at edge of lungs - it is not as strong as lung tissue)
Secondary = underline respiratory condition e.g. TB, pneumonia, COPD
Traumatic: due to blunt/penetrating trauma to the chest
What are the symptoms of pneumothorax?
Chest pain
Breathlessness
tachycardia
Cardiorespiratory collapse - if severe
Outline the treatment of pneumothorax
Needle aspiration: needle with a catheter is inserted between the ribs into the space. Air is drawn out.
Chest tube: is inserted into the air filled space and air is sucked out.
If repeated episodes of pneumothorax or it persists, then thoracoscopy surgery.
List the ways oxygen is carried in the blood
IN One of two forms:
dissolved - very small amount of oxygen is dissolved
Bound to haemoglobin - major transport molecule for oxygen, found in RBCs, this is reversible
Describe the structure of haemoglobin
Hb is a tetramer made up of 4 subunits.
Each subunit consists of:
Globin: polypeptide chain 2 alpha and 2 beta
Haem: iron porphyrin compound
what is the max number of oxygen molecules that Hb can bind?
4
What is oxygen saturation?
the amount of oxygen bound to haemoglobin relative to the maximal amount that can bind
describe the affinity of Hb for Oxygen at different levels fo oxygen?
When O2 levels are low, Hb affinity for oxygen is low = oxygen release
When O2 levels are high, Hb affinity for O2 is high = oxygen binding
What does the oxyhemoglobin curve show?
Relationship between the partial pressure of oxygen and percentage of oxygen saturation
Describe the oxygen haemoglobin curve
Initial binding of first oxygen molecule is difficult but it facilitates the binding of further oxygen molecules. As partial pressure of O2 increases, binding of O2 to Hb also increases (saturation) until it reaches its maximum amount that can bind. As this binding limit is approached, very little additional oxygen binding occurs and the curve levels out. This gives the curve its sigmoidal (S) shape.
How does a change in pH shift the curve?
Increase in pH pushes the curve to the left (increased uptake of Oxygen from tissues)
Decrease in pH (low pH) shifts curve to right (greater release of oxygen)
when you exercise there’s more Co2 so decrease in pH so more oxygen released to supply tissues
How does a change in temperature shift the curve?
Increase in temperature shifts the curve to the right
Decrease in temperature shifts the curve to the left (so more uptake of oxygen from tissues)
How is carbon dioxide carried in the blood? Which method is used most?
Dissolved
Bound to Hb
Converted to bicarbonate (most of it is carried this way)
Explain what happens when CO2 is converted to bicarbonate
When CO2 is produced by the tissues it dissociates into carbonic acid with the help of carbonic anhydrase. Carbonic acid dissociates quickly into H+ and HCO3- ions.
H+ is removed by buffers and binds to Hb to prevent it from changing the pH and Bicarbonate ion (HCO3-) moves out of the RBC in exchange for Cl- and acts as a pH buffer.
When Bicarbonate ion reaches the lungs it moves back into the RBC in exchange for CL- and H+ dissociates from the Hb. H+ binds to bicarbonate ion ion to form carbonic acid which turns into CO2 and is expelled from the body.
what factors affect breathing?
Sleep EMotion Exercise Temperature COughing Phonation
What is a chemoreceptor?
Sensory receptor that detects chemical changes in the surrounding environment
What are peripheral chemoreceptors?
Small highly vascularised bodies in region of aortic arch and carotid sinuses
What is hypoxia?
oxygen deficiency
What is hypercapnia?
Abnormally elevated CO2 levels
Small changes in which gas result in large effects on ventilation?
PP of CO2
What are mechanoreceptors?
Sensory receptors that detect changes in pressure, movement and touch.
What are the 3 respiratory groups found in the respiratory centre in the brain?
Dorsal
Ventral
Pontine
What is found in the dorsal RG and what does it do?
Mostly inspiratory neurons (Most are in the NTS)
it receives sensory information (chemoreceptors and mechanoreceptors)
What is found in the ventral RG and when is it active?
Inspiratory and expiratory neurons
Primarily active when exercising or stressed
What does the pontine respiratory group do?
Modulates respiratory output
What does partial pressure equal to?
barometric pressure X fraction of gas in mixture
what’s dead space?
Volume of air breathed in that does not participate in gas exchange. It is ventilation without perfusion.
What is pulmonary shunt?
A pathological condition in which alveoli are perfused as normal but ventilation (air supply) fails to supply the perfused zone.
i.e. pulmonary/ventilation ratio is zero.
What causes the oxyhemoglobin curve to the left?
Fetal haemoglobin
What is the lowest vertebral level reached by the pleura?
T12
What is respiratory acidosis?
Hypoventilation: when ventilation is less than the CO2 levels. This occurs due to an acid disturbance whereby there is increased CO2 production which decreases the pH
What are the compensatory mechanisms that occur in respiratory acidosis?
When O2 is lower, Hb binds to and buffers H+ more effectively. High levels of H+ decrease the affinity of Hb for O2 and O2 is unloaded to the tissues. this improves the supply of O2.
Chemoreceptors detect changes in PP of oxygen, carbon dioxide and pH. It responds by increasing breathing rates and ventilation.
Renal compensation: when H+ levels are high, more H+ is excreted by the kidney in urine. More HCO3- is retained and reabsorbed from tubules. This type of compensation is the slowest.
