introduction to respiratory system

• where is the thorax

  • between the neck (above) and the abdomen (below)
• thoracic wall

  • protects the heart & lungs
  • make the movements of breathing
  • breast tissue - lactation

  
• thoracic cavity

  • within the chest walls
  • contains vital organs (also known as viscera)
  • also contains major vessels and nerves
  • consists of the mediastinum & right and left pleural cavities

  
• the skeleton of the thoracic/chest wall

  • 12 pairs of ribs:
  • true ribs= 1-7 (attach via their costal cartilage to the sternum)
  • false ribs= 8-10 (attach via their costal cartilage above to the sternum)
  • floating ribs= 11-12 (no attachment to sternum)
  • intercostal spaces
  • costal margin
  • 12 thoracic vertebrae
  • clavicle and scapula
  • sternum:
  • manubrium, body, xiphoid, sternal angle
• the skeleton of the thoracic/chest wall diagram

  diagram

  A) costal cartilages

  B) sternal angle- angle of Louis level of T4 vertebrae

  C) jugular notch

  D) clavicle

  E) scapula

  F) manubrium of the sternum

  G) body of the sternum

  H) xyphoid process of the sternum

  I) costal margin

  
• other diagram of the skeleton of the throacic/ chest wall

  posterior view

  A) posterior view

  B) 12 x throacic vertebrae- part of vertebral column

  C) clavicle

  D) spine of scapula

  E) scapula

  
• what are the intercostal spaces?

  • spaces between ribs is called the intercostal space (numbered according to the rib superior to it)
  • each intercostal space contains intercostal muscles which help to move the ribs during breathing/changing the volume within the thoracic cavity during respiration
  • we have external, internal and innermost intercostal Mm

  
• external intercostal muscles

  • the most superficial layer of the intercostal muscle
  • function: ribs to elevate in inhalation

  
• internal intercostal muscles

  • the middle layer of intercostal muscle
  • only function in forced exhalation

  
• innermost intercostal muscles

  • the deepest layer of intercostal muscle
  • separated from the other 2 layers of muscle by the neurovascular bundle

  
• neurovascular supply to intercostal spaces

  • each intercostal space has a separate blood and nervous supply (neurovascular bundle)
  • this neurovascular bundle runs along the inferior aspect of the rib in the costal groove
  • these run anteriorly from the spinal column to the sternum
  • always in the arrangement (superior->inferior):
  • intercostal Vein
  • intercostal Artery
  • intercostal Nerve
  • ^ VAN

  
• diaphram

  • forms the flood of the chest cavity and forms the roof of the abdominal cavity
  • has 'openings' to permit structures to pass between the 2 cavities
  • it is a skeletal muscle with an unusual central tendon
  • anatomically arranged as right & left 'domes'
  • the right dome is normally the more superior (due to the presence of the liver inferiorly)
  • the muscular part attaches peripherally to:
  • the sternum
  • the lower 6 ribs & costal cartilages
  • L1-L3 vertebral bodies
  • the muscular part is supplied by the phrenic nerve (C3,4,5 anterior rami)

  
• openings of the diaphragm

  • there are 3 major openings in the diaphragm
  • allows 3 very important structures to pass from the thoracic to the abdominal cavity:

  1. IVC passes through at T8 level
  2. oesophagus passes through at T10 level
  3. aorta passes through at T12 level

  
• opening of the diaphragm labels

  diagram

  A) aorta

  B) inferior vena cava

  C) oesophagus

  
• what is the respiration mechanism?

  • thoracic volume is increased in 3 planes during inspiration

  1. Anteroposterior increase is illustrated with pump handle movement
  2. Transverse increase is illustrated using a bucket with 2 handles. lifting handles is like raising right and left ribs at the costovertebral and costosternal joints
  3. Vertical dimension is increased by downward pull of diaphragm

  • diaphragm is the primary muscle in inspiration

  
• relaxed inhalation

  • diaphragm contracts
  • external intercostals elevate thoracic cavity
• relaxed exhalation

  • the muscles above relax
  • this allows the lungs to recoil and push air out
• upper tract in resp system

  • nose
  • nasal passages
  • paranasal sinuses
  • pharynx
  • portion of the larynx above the vocal cords

  
• lower tract in resp system

  • larynx below vocal cords
  • trachea
  • bronchi
  • bronchioles
  • lungs

  
• the nasal cavity

  • air enters via the nasal cavity
  • the nasal cavity is entered anteriorly through the anterior nares (nostrils)
  • it opens posteriorly into the nasopharynx through the choanae (posterior nares)
  • mucosa lines the nasal cavity, except the nasal vestibule which is lined with skin

  
• epithelium lining the nasal cavity

  • the majority of the nasal cavity is lined by 'respiratory epithelium'
  • a small part of the nasal cavity is lined by stratified squamous epithelium (nasal vestibule)
  • respiratory epithelium is pseudostratified columnar ciliated epithelium (with goblet cells)

  
• paranasal sinuses

  • maxillary sinuses:
  • cavities within the skull filled with air
  • line by ciliated pseudostratified columnar epithelial cells
  • connected to the lateral walls of the nasal cavity
  • frontal sinuses:
  • lighten the skull
  • increase resonance of voice
  • humidify inspired air
  • sphenoidal sinuses:
  • innervated by trigeminal nerve (CN V)
  • blood supply: branch of external carotid artery
• paranasal sinuses labels

  diagram

  A) frontal sinus

  B) ethmoidal cells

  C) maxillary sinuses

  D) sphenoidal sinus

  
• the oral cavity

  • acts as an air inlet
  • anteriorly - oral fissure
  • posteriorly - oropharynx
  • laterally - cheeks
  • superiorly - palate (hard and soft)
  • inferiorly - muscular flood and tongue

  
• the pharynx

  • 3 parts labels

  A) nasopharynx

  B) oropharynx

  C) laryngopharynx

  
• nasopharynx

  • posterior to nasal cavity and above soft palate
• oropharynx

  • posterior to oral cavity
  • inferior to the level of the soft palate
  • superior to the upper margin of the epiglottis
• laryngopharynx

  • extends from the superior margin of the epiglottis to the top of the oesophagus
• tonsillar region

  • Waldeyer's tonsillar ring/pharyngeal lymphoid rind is a group of lymphoid tissues in the pharynx:
  • pharyngeal tonsil (adenoids)
  • tubal tonsils x2
  • palatine tonsils x2
  • lingual tonsil
  • the first line of defence against pathogens entering through the nasopharynx or oropharynx
• tonsillar region labels

  diagram

  A) lingual tonsil

  B) palatine tonsils

  C) pharyngeal tonsil / adenoids

  D) tubal tonsils

  
• larynx

  • voice box
  • vocal cords. sound is created by forcing air through the vocal folds of the larynx which vibrate to make noise
  • so air travels through the larynx into the trachea
  • there are a few cartilage structure surrounding the larynx keeping it patent and protected

  
• the trachea (windpipe)

  • through the larynx, air travels through the trachea which is the tube through which air is transported to the lungs
  • it runs from the level of the lower border of the cricoid cartilage C6/7 to T4/5 vertebral level
  • it bifurcates into the left & right primary (main) bronchi
  • the trachea is formed of 'horse shoe' or 'C-shaped' rings of hyaline cartilage, held together by dense connective tissue
  • posteriorly, at the junction where the trachea is in contact with the oesophagus, the trachea has a membrane void of cartilage and covered in smooth muscle- the trachealis muscle
• the trachea labels

  posterior and anterior view

  A) tracheal mucosa

  B) trachealis muscle

  C) tracheal rings

  D) cartilage rings

  
• the trachea - carina

  • at the bifurcation of the trachea lies the carina
  • it is a ridge that can be seen on a bronchoscopy (little camera)
  • the carina is a key landmark in determining pathologies
  • widening/ distortion of the carina can often indicated cancer in the lymph nodes that lie just inferior to the carina
  • the name of these lymph nodes is Inferior Tracheobronchial lymph nodes

  A) carina

  B) membranous part of trachea

  C) tracheal cartilage

  D) right main bronchus

  E) left main bronchus

  
• bronchoscopy

  • bronchoscope is used to view the airways and check for abnormalities
  • travels down the trachea to enter a main bronchus
  • the bronchoscope must move around the carina to get the bronchus
  • the inferior tracheobronchial lymph nodes can blunt the carina when enlarged -> indicating pathology

  
• the bronchi

  • the trachea bifurcates into the LEFT & RIGHT primary (main) bronchi
  • the bronchi have characteristic hyaline cartilage rings, supporting them, the same as in the trachea
  • the position each bronchi sits at is different
  • the right is wider, shorter and lies at a steep vertical angle
  • the left is narrower and more horizontal
  • ^- important as inhaled foreign objects are more likely to get lodged in the right bronchus

  A) right main bronchus

  B) left main bronchus

  
• secondary bronchi

  • the left and right primary (main) bronchi divide further into secondary (lobar) bronchi
  • 2 on the left
  • 3 on the right
  • secondary further divide to give tertiary (segmental) bronchi; usually 10 for each lung

  
• terminale bronchioles

  • each tertiary bronchi gives rise to many terminal bronchioles - these now differ in structure
  • NO longer have hyaline cartilage in their walls
  • respiratory bronchioles branch from these terminal bronchioles
  • each respiratory ends in an ACINUS of clustered alveoli

  
• cute lung diagram

  • main function of lungs: gas exchange

  
• the lungs

  • they are the functional organs of respiration
  • 2 lungs- either side of the mediastinum and are protected by the ribcage
  • the diaphragm lies inferior to lungs which separates the thoracic and abdominal cavity
  • the function of the lungs is to oxygenate blood
  • they achieve this by bringing inhaled air into close contact with oxygen-poor blood in the pulmonary capillaries
  • they can expand down to the lower border of the ribs; the costal margin and extend as bar up as the root of the neck - above the 1st rib