Lungs and breathing Flashcards
What is the Mediastinum?
A central wall of tissue dividing the thoracic cavity
Consists of:
- heart
- great vessels
- fat
- remnants of the thymus gland
What does the mediastinum divide the thorax into?
Divides the thorax into 2 pleural cavities:
- Parietal pleura - well supplied by sensory nerves, covers the rib cage
- Visceral pleura - no sensory nerve innervation, covers the lungs
What is found in between the two pleura?
Pleural cavity contains a small amount of lubricating fluid
What is the costodiaphragmatic recess?
Gap between the base of the lung and the base of the pleural cavity
Allows lungs can slide and expand when fully inflated
Describe basic lung structure
- Right and left lung
- Fissures
- Hilum
- Bronchial tree
Describe basic lung anatomy
Each lung has an:
- Apex - top
- Base - bottom
The surface of the lung can either be:
- Costal - facing the ribs
- Mesiastinal - facing the mediastinum
How many fissures are there in the right lung?
2
What are the names of the fissures of the right lung?
Horizontal
Oblique
What are the name of the lobes of the right lungs?
Upper
Middle
Lower
How many fissures are there in the left lung?
1
What are the names of the fissures of the left lung?
Oblique
+ cardiac notch
How many lobes are there in the left lung?
2
What are the names of the lobes of the left lung?
Upper
Lower
Lingula
What is the hilum of the lung?
The hilum is a large triangular depression where the connection between the parietal pleura and the visceral pleura is made, marking the meeting point between the mediastinum and pleural cavities
What are the structures found in the hilum of the lung?
Pulmonary artery
2 pulmonary veins
Main bronchus
Lymphatics
Bronchial vessel
Autonomic nerves - parasympathetic and sympathetic to the smooth muscles of the bronchi and vessels
What are the components of the bronchial tree?
- Trachea
- Main primary bronchus
- Lobal bronchus
- Segmental bronchus
- Bronchiole
- Terminal bronchiole
- Respiratory bronchiole
- Alveoli
What are bronchopulmonary segments?
Each lobe of the lung is divided into sub-lobes called bronchopulmonary segments.
Each segment is supplied by:
- A segmental artery
- A segmental vein
- A segmental bronchus
What is the goal of inspiratory movements?
Increase the volume of the thorax
Decrease the pressure of the thorax
This causes the internal pressure to fall and air to increase
What are the three ways to achieve the goals of inspiration?
- Increasing the superior-inferior height
- Increase the bilateral diameter
- Increase the anterioposterior diameter
How do the ribs increase the anteroposterior diameter during breathing?
Upper ribs slope downwards at rest
Raising them increase the anteroposterior diameter of the chest and pushes the sternum forwards
Requires flexion at the manubrio-sternal joint
What 3 movements are involved in increasing the bilateral diameter of the ribcage?
- Sliding of top ribs
- Bucket-handle movement in the true lower ribs
- Caliper movement in floating ribs
Which ribs take part in increasing the bilateral diameter of the ribcage?
Lower ribs (5 and below)
Describe the buckle-handle movement of the lower ribs
Anterior and posterior attachments of the lower ribs lie weel above the midpoint of the rib, so raising the ribs raises the midpoint
What enhances the movement of the ribs increasing the bilateral diameter of the ribcage?
The flattening of the diaphragm
Contracts to flatten, pushing against the abdominal organs
Also aids in raising intra-abdominal pressure
Which muscles are involved in increasing the superior-inferior height of the ribcage?
External intercostal muscles elevate the ribs with the aid of the pectoralis muscles, scalenes and sternocleidomastoid
Which muscle joins the ribs and arms?
Pectoralis muscle
Which muscle joins the skull to the clavicle and sternum?
Sternocleidomastoid
How does the scalenes increase the superior-inferior height of the rib cage?
Fix the first rib so that the other ribs are puller towards it when the intercostals contract
How do the scalene muscles increase the superior-inferior height of the rib cage?
Elevate the 1st and 2nd ribs
What type of process is expiration?
It is a passive process
What aids expiration?
Recoil of the lungs
Elasticity of lung tissue
Some contraction of the abdominal muscle - helps to push the diaphragm up
What does active respiration require?
Contraction of internal intercostals pulling ribs down towards lower ribs fixed by back and abdominal muscles, aided by increased contraction of abdominal wall muscles
What are the 2 steps of lung development?
- Outgrowth from gut
2. Proliferation and budding
Describe the first step of lung development
A median lung bud grows out from the ventral side of the gut tube
Describe the second step of lung development
Endodermal bud divides
Endoderm forms the lining of the system and the glands of the system
The endoderm is surrounded by the splanchnic lateral plate mesoderm that will form the smooth muscle, cartilage and blood vessels in the lung
Signalling between the endoderm and mesoderm helps to ensure correct branching
How many alveoli are there at birth?
20-70 million
How many alveoli are there in an adult?
300-400 million
What are the functions of surfactant?
Stops the respiratory surfaces from sticking together by reducing surface tension
Aids oxygen uptake
Aids lung compliance
Inhibits excess mucus
Around what week does the surfactant develop?
Week 17
2 features of underdeveloped lungs in premature babies
Low lung capacity
Low surfactant
What are the stages of bronchial tree development?
- Embryonic
- Pseudoglandular
- Canalicular
- Saccular
- Alveolar
What structures make up the acinus?
Terminal bronchiole
Respiratory bronchiole
