Describe Conducting Zone And Respiratory Zone Of The Respiratory Tract. Describe Meschanic Of Ventilation Cluding Role Of Pleura. Describe Surfactant And Its Role In Respiratory System Flashcards
What are the 2 zones / divisions of the lower respiratory tract?
What is the anatomical dead space?
- Conducting zone (includes bronchi, bronchioles and terminal bronchioles)
- Respiratory zone (includes respiratory bronchioles, alveolar ducts and alveoli)
The anatomical dead space is in the conducting zone. It’s ferried to this because there is no alveoli in this zone and therefore no gas exchange.
Describe alveoli
Alveoli are a sac of two types of cells to allow gas exchange into the blood. They have a high surface area.
What are the they types of cells in alveoli?
What lines the alveolar surface?
Type 1 cells: squamous (covers 90% of surface area and permit gas exchange with capillaries)
Type 2 cells: cuboidal (covers 10% of surface area and produce surfactant.
Numerous macrophages / phagocytoses particles
What helps protect the lungs from infection?
Respiratory epithelial lining of the respiratory tract.
Pseudo stratified epithelium, with cilia and goblet cells, lines the airways from the nasal cavity to the largest bronchioles.
As you go down to alveoli, no more goblet cells and cili so infection defence relies on antibodies, phagocytes and macrophages.
What is the muscocillary escalator?
Mucous secreted by goblet cells and glands traps and deposits dust and other particles.
There is synchronous regular beating of cilia of the mucous membrane wafts mucous and adhered particles up towards the pharynx. Mucous is then Coughed up or swallowed
What are intercostal muscles?
11 pairs of intercostal muscles occupying the spaces between the 12 pairs of ribs. They are arranged in two layers, the external and internal intercostal muscles, supplied by the intercostal nerves.
Describe external intercostal muscles
These extend downwards and forwards from the lower border of the ribs above to the upper border of the ribs below.
They lift the rib cage upwards and downwards in inspiration.
Describe internal intercostal muscles
These extend downwards and backwards from the lower border of the ribs above to the upper boarder of the ribs below, crossing the external intercostal muscles fibres at right angles.
They are used when expiration becomes active.
What is the diaphragm?
Dome shaped muscular structure supplied by the phrenic nerve and separating the thoracic and abdominal cavities.
It forms the floor of the thoracic cavity and the roof of the abdominal cavity.
It consists of a central tendon from which muscle fibres radiate to be attached to the lower ribs and sternum, and the vertebral column by two crura
What are the accessory muscles in forced inspiration?
It’s assisted by the sternocleidmastoid muscles and the scalene muscles, which link the cereal vertebrae to the first two ribs and increase rib cage expansion.
When these muscles contract, they pull the rib cage upwards, supplementing the action of the external intercostal muscles.
What are the accessory muscles in forced expiration?
Forced expiration is helped by contraction of the internal intercostal muscles, which pull the rib cage downwards and inwards, compressing the lungs and aiding exhalation.
Sometimes, the rectus abdominis muscle is also used, which compresses the abdominal organs, increasing the upwards pressure on the diaphragm and helping to force air out the lungs.
Explain inspiration. Talk about intercostal muscles, pleura and pressure.
Is this process passive or active?
The external intercostal muscles and diaphragm contract simultaneously, enlarging the thoracic cavity in all directions.
(The rib cage is anchored at the first rib, which is fastened firm,y to the sternum and the first thoracic vertebra.)
Contraction of the external intercostal muscles lifts the rib cage as a unit upwards and outwards, expanding the thorax.
When the diaphragm contracts, the muscle fibres shorten and the central tendon is pulled downwards to the level of the 9th thoracic vertebra, lengthening the thoracic cavity.
Because the parietal pleura adheres to the diaphragm and the inside of the rib cage, it is pulled outwards along with them?
This pulls the visceral pleura outwards too, since the two pleas are held together by negative interpleural pressure.
Because the visceral pleura is firmly adhered to the lung, the lung tissue is therefore also pulled upwards and outwards with the ribs, and downwards with the diaphragm.
This expands the lungs and the pressure within the alveoli and in the air passage falls, drawing air into the lungs in an attempt to equalise atmospheric and alveolar air pressures.
The negative pressure created in the thoracic cavity aids venous return to the heart and is cal,Ed the respiratory pump.
This is an active process and it needs energy to contract muscles.
Explain expiration
Is this an active or passive process?
Relaxation of the external intercostal muscles and the diaphragm results in downwards and inwards movement of the rib cage and elastic recoil of the lungs.
This action increases pressure in the lungs and expels air from the respiratory tract.
At the end of respiration, the lungs still contain some air, and are prevented from complete collapse by the intact pleura.
This process is passive as it does not require the expenditure of energy.
There is a pause after expiration before inspiration starts.
What are the 3 physiological variables affecting breathing?
- Elasticity
- Compliance
- Airway resistance
Explain elasticity in relation to it being a physiological variable affecting breathing
Elasticity is the amount of stretch in the lung itself and it’s ability to return to its normal shape.
Diseases that cause scarring and loss of elasticity meaning the lungs are not able to return to their normal shape and are slightly expanded. This increases the resistance and makes it harder to breathe.
