Anatomy of Breathing - Lecture 17 Flashcards
What are the lungs?
○ Located in thorax
○ Separated by mediastinum and heart
○ Extend from neck to diaphragm
○ Diaphragm separates throacic and abdominal cavities
What makes up the lungs?
○ Conical shaped with soft, spongy texture
○ Apex of the lung lies above the clavicle
○ Diaphragmatic surface: sits on the diaphragm
○ Costal surface: lies adjacent to the ribs
○ Mediastinal surface: faces the mediastinum
What are the features of the right lung?
○ Wider and shorted than the left lung: liver underneath the diaphragm
○ Three lobes: superior, middle, inferior
○ Two fissures: oblique and horizontal
What are the features of the left lung?
○ Narrower and longer than the right lung
○ Two lobes: superior and inferior
○ One fissure: oblique
What is the hilum of the lung?
○ Located on the mediastinal surface
○ The area where the pulmonary vessels, bronchi, bronchial vessels, lumpathics and nerves enters/leaves the lung
What are the physical properties of the lungs?
○ Compliance: the ability of the lungs to expand
○ Elasticity: elastic tissue allows lung expansion during inspiration and recoil during expiration
What factors can affect compliance?
○ Connective tissue structure of the lungs
○ Level of surfactant
○ Mobility of thoracic cage
What is the pleura?
Double layered serous membrane
What makes up the serous membrane?
○ Visceral pleura: adheres to the lung
○ Parietal pleura: attaches to the thoracic wall and diaphragm
○ Pleural cavity: Thin layer of serous fluid that holds the two layers together
What are the functions of the pleura?
○ Reduces friction during breathing
○ Creates a pressure gradient which assists in ventilation
○ Compartmentalises each lung: reduces spread of infection
What is the bony thorax and what does it consist of?
○ Forms the skeleton of the chest wall
Consists of:
○ Sternum
○ Ribs (12 pair)
○ Thoracic vertebrae (12)
What is the sternum and what does it consist of?
○ Breast bone
Consists of:
○ Manubrium
○ Body
○ Xiphisternum
What are the ribs?
○ Attached by the head and tubercle to the thoracic vertebrae
○ Slope downwards and forwards
How are the ribs attached?
○ Ribs 1-10 attached by costal cartilage to the sternum:
- 7 pairs true
- 3 pairs false
- 2 floating
What is the thoracic vertebrae?
○ Head of rib articulates with the body of the thoracic vertebrae
○ Tubercle of rib articulates with the transverse process of the thoracic vertebra
○ Synovial joints between the ribs and vertebrae to allow movement of ribs
What are intercoastal muscles and what does it consist of?
○ Span the spaces between the ribs
○ External intercostal muscles: superficial layer
○ Internal intercostal muscles: middle layer
○ Innermost intercostal muscles: deep layer
Which direction does the external intercostal run?
Downwards and fowards
Which direction does the internal intercostal run?
Downwards and backwards
How is blood and nerves supplied to the intercostal muscles?
○ Nerves and vessels course between the internal intercostal and innermost intercostal muscles
○ Protected by the ribs
○ Supply the muscles, adjacent skin and pleura
What are the features of the diaphragm?
○ Separates the thorax from the abdomen
○ Dome-shaped skeletal muscle with a central tendon
○ Attached to the xiphisternum, costal margin, 11th and 12th ribs and the lumbar vertebrae
○ Openings for inferior vena cava, oesophagus & aorta
○ Fibrous pericardium fused to central tendon
○ Innervated by the phrenic nerve
When does inspiration occur?
When intrapulmonary pressure is lower than atmospheric pressure
When does expiration occur?
When intrapulmonary pressure is greater than atmospheric pressure
How is intrapulmonary pressure altered?
Changes in thoracic volume
How can thoracic volume be altered?
Changes in:
○ Vertical diamter: top of thorax to diaphragm
○ Anterior posterior (AP) diameter: between sternum and vertebral column
○ Transverse diameter: left and right side of ribcage
How is the vertical diameter altered?
○ Increase = contraction of diaphragm
○ Decrease = relaxation of diaphragm
○ Contraction responsible for 75% increase in thoracic capacity during inspiration
How is AP and transverse diameters increased?
○ Elevation of the ribs at the sternal makes them more horizontal and pushes sternum forward (pump handle movement)
○ Responsible for 25% increase in thoracic capacity
How is transverse diameter increased?
○ Many of the ribs are lowest near their middle and rise at each end
○ If the middle of the rib rises, it moves away from the midline of the body and makes the chest wider
○ Responsible for 25% increase in thoracic capacity
What muscles are involved in quiet inspiration?
○ Contraction of diameter
○ External intercostals elevate the ribs
How does quiet expiration happen?
○ Passive process
○ Diaphragm and external intercostal muscles relax
What muscles are involved in forced inspiration?
○ Sternocleidomastoid: pulls up the manubrium of the sternum and the clavicle and brings them up and fowards which increases AP diameter
○ Scalenes: Holds the 1st and 2nd ribs in place which results in more effective movement of intercostal muscles
○ Serratus anterior: pulls the scapular forward
○ Pectoralis minor: pulls ribs 3-5 out when scapula is pulled
○ Pectoralis major: involved in the movement of the humerus and if humerus is fixed ribs move up and out
What muscles are involved in forced expiration?
○ Internal and innermost intercostals depress the ribs and reduce the size of the thoracic cavity
○ Abdominal muscles compress the abdomen and force the diaphragm upwards
