Flashcards in cardiovascular week 4 Deck (37):
Describe the trachea
wall contains fibrous tissue/ muscle tissue. C shaped hyaline cartilage rings
internal lining - respiratory epithelium
tracheal rings between cartilage contain glands
cartilage surrounded by perichondrium
trachealis muscle - smooth muscle, relaxes on swallowing and inspiration, contraction on coughing
Describe the epithelium of the trachea
ciliated pseudo stratified with goblet cells in between
Describe the trachea bifurcation
mainly propria with glands
ring-shaped muscular layer
cartilage plates instead of C-shaped rings
lymphatic infiltration in connective tissue
Describe the bronchioli
less than 5mm
epithelium decreases in size - cuboidal in terminal branch, cilia tend to disappear
no goblet cells
clara cells - function?
Describe the respiratory portion
alveoli open here
often located in clusters opening into alveolar sac
sac-like evaginations of tissue
95% type 1 pneumocytes - thin epithelium
5% `type 2 - produce surfactant
surfactant relieves surface tension of alveoli
What is present between alveoli?
alveolar septa - thin connective tissue rich in elastic fibres, extremely vascularised, blood-air barrier
What are the pleura?
each plural cavity is lined by a single layer of flat cells, mesothelium, and an associated layer of connective tissue
What are the two major types of pleura?
Describe the pleural cavity
the potential space enclosed between the visceral and parietal pleura. Normally contain a thin layer of serous fluid
What is ventilation?
the movement of gas into and out of the alveoli
What is perfusion (q)
the flow of blood through the pulmonary capillaries
Why must perfusion and ventilation be matched?
For efficient gas exchange
Where is perfusion greater and why?
the bases of the apices due to gravity
What are the ways which breathing is controlled?
higher cortical centres - modulation of breathing rate or depth
Central and peripheral chemoreceptors - react to a variety of factors in the blood
What do central chemoreceptors respond to?
only changes in plasma carbon dioxide levels
How do central chemoreceptors work?
Separated from the blood by the blood-brain barrier
only non-polarised molecules can diffuse through the lipid layer
When CO2 diffuses into the CSF it combines with water to form bicarbonate and hydrogen ions.
Chemoreceptors detect H+ ion concentration
Oxygen can diffuse but has no effect
How do peripheral chemoreceptors work?
they are located in the arctic arch and carotid body
they respond to changes in the partial pressures of CO2 or H+, or falls in O2
What is the most important factor in determining breathing rate?
What is a pneumothorax?
the presence of air in the pleural space
What can cause pneumothorax?
spontaneous, iatrogenic injury or trauma to the lung or chest wall
What are risk factors for pneumothorax?
presence of apical sub-pleural blebs
What types of pneumothorax are there?
Describe a closed pneumothorax
communication between the airway and pleural space seals off as the lung deflates and does not re-open
pleural pressure remains negative
spontaneous reabsorption of air occurs in days or weeks
Describe open pneumothorax
communication fails to seal off and air continues to flow freely between the bronchial tree and pleural space
Describe a tension pneumothorax
communication between the airway and pleural spear acts as a one-way valve
air enters the pleural space during inhalation
does not escape during expiration
large amounts of trapped air accumulate
this causes mediastinal displacement towards the opposite side
What is the oxygen capacity of haemoglobin?
the maximum number of oxygen molecules that can be carried
What is the saturation of haemoglobin?
The proportion of capacity occupied
What happens if tissues start to use more oxygen?
the PaO2 only has to drop a little for the saturation to drop a lot - haemoglobin gives lots of oxygen out to the tissues
What happens when the oxo-haemoglobin curve is shifted to the right?
for a given PaO2, the oxygen saturations are lower
What can shift the curve to the right?
increased temperature, CO2 concentration, H+ concentration
2,3DPG is a molecule produced in RBCs which pushes curve to right in chronic hypoxia - at altitude
What causes left-ward shift of the curve?
reduction of other factors
foetus - more efficient at stripping oxygen from the mother
How isCO2 transported in the body?
dissolved in plasma
bound to proteins such as carbamino compounds (e.g. haemoglobin)
as a bicarbonate
What is the reaction between carbon dioxide and water?
CO2 + H2O > H+ + HCO3-
Why are investigations of the respiratory system important?
assess fitness for treatment
What methods of respiratory investigations are there?
xray - usually first
CT scanning - solid, peruse. affecting other body parts?
bronchoscopy - can be used to take a sample
CT guided biopsy
What is type 1 respiratory failure?