Lecture 13 Flashcards
How is pressure inside the lungs decreased? What law is this?
Boyle’s law states that increasing volume will decrease the pressure and vice versa, hence the lungs change in volume due to certain respiratory muscles to provide a pressure difference.
What is the location of the thoracic cavity? What cavities are within it?
The thoracic cavity is bordered by the diaphragm inferiorly (coming down to about the 12th vertebrae posteriorly while the anterior portion comes down to the 10th, superiorly is the root of the neck, laterally are the ribs and intercostal space, anteriorly is the sternum. The three cavities are two pleural cavities (which the lungs are in, on the lateral parts) and the pericardial cavity (where the heart is located, in the inferior center).
The mediastinum is the center of the thoracic cavity.
What are the main joints anterior to the thoracic cavity.
The joints between the sternum and the ribs. These are joined by hyaline cartilage bars which themselves are linked by special joints. The hyaline cartilage allows the ribs to expand.
The sternocostal joints are the joints which join the hyaline bar with the sternum, all of which are synovial except for the first ribs which is cartilaginous (fibrocartilage)
The costochondral joints join the hyaline bars with the ribs and are all cartilaginous
The interchondral joints join the hyaline bars wit each other (particularly important for false ribs), these are synovial.
What are the main joints posterior to the thoracic cavity?
The articulation between the thoracic vertebrae and the ribs, these contain two seperate joints and are synovial.
The costotransverse joints join the ribs to the transverse (posterior lateral aspect) of the vertebrae.
The Costovertebal articulates with the base of the vertebrae.
What does the thoracic cavity contain?
Both lungs, the heart (in mediastinum in pericardial sack with the vessels), the primary, secondary and tertiary bronchi. Also contains the visceral pleura which lines the lungs and protects them and the parietal pleura which lines the cavity.
What muscles are in the primary respiratory muscle group? What does it do?
The diaphragm is in the primary muscle group, it is at the lower boundary of the thoracic cavity, it is skeletal muscle which won’t fatigue easily and is innervated by the phrenic nerve (Which is in C3-C5), during inspiration it contracts (increasing vertical lung volume).
What muscles are in the secondary respiratory muscle group? What do they do?
The intercostal muscles (muscles between ribs), there are two layers which run diagonally, the ruperficial ones are used for inspiration and the direction of the muscle fibers is inferior and medial (down and forward), they will pull the lungs up and out, the internal (deep intercostals are for forcing expiration and the direction is inferiorly and laterally (pulling the ribs down).
What muscles are tertiary respiratory muscles? What do they do?
These are the accessory muscles and are used during forced inspiration or forces expiration (when the other muscles arn’t enough) they are attached to the clavicles or ribs and an example of these are the abs.
What type of membrane are the pleural membranes? What fluid do they secrete and what does it do?
The pleural membranes are serous membrans, an example of which is the visceral pleura which covers the lungs or the parietal pleura which lines the thorax and mediastinum, the pleural cavity is a potential space between these two membranes and contains serous fluid (about 2mL). This fluid allows low friction movement of the lungs, reduced surface tension and adhesion and also attaches the parietal and visceral pleura to the thoracic wall, resulting in lung movement with thoracic wall change.
What is expiration? What is its relative energy cost and why?
Expiration is the opposite of inspiration (release of air) it doesn’t require much energy because it can be done by simply relaxing the respiratory muscles, as well as large elastin amounts in the lungs to allow for recoil
