Lower Respiratory Tract Flashcards
What are the components of the LRT?
- Larynx
- Trachea
- Bronchi
- Bronchioles
- Alveoli
Functions:
- conducts air to/from the site of gas exchange
- completes cleaning, warming and humidifying of air
- provides a barrier between air and blood, and a large surface area for gas exchange
Describe the larynx
- Passage fro air only
- Anterior to the esophagus
- From the hyoid bone to the trachea
- Cartilages protect and maintain an open airway (patent)
- Epiglottis closes over the airway when swallowing
Describe the cartilages of the larynx
Epiglottis: closes over airway when swallowing. Sits on top of larynx like a lid.
Thyroid cartilage: provides protection from the anterior side as well as keeping the airway open
Laryngeal prominence: its a significant bump (that forms the Adams apple in males)
Cricoid cartilage: complete circular ring which forms the gateway to the trachea and ensures it’s always open.
Tracheal cartilage: C shaped and only covers the anterior and lateral sides
Describe the Glottis and two folds of the larynx
Glottis = ‘voice box’
Folds attached to cartilages (found between the epiglottis and the cricoid cartilage):
- Vocal folds:
- ‘True’ vocal cords
- Passing air causes vibrations = sound waves
- used for normal phonation
- testosterone affects cartilage and muscle, resulting in longer, thicker folds = deeper voice
- Vestibular folds:
- ‘false’ vocal cords
- superior to vocal fords
- prevent foreign object entry to the glottis
- can produce very deep sounds
Describe the trachea
- Anterior to the esophagus
- Between the larynx and primary bronchi
Function:
- maintain patent airway
- C-shaped cartilage rings
- ends connected by a band of smooth muscle: trachealis (which contracts for coughing)
- many elastin fibres in lamina propria and submucosa
- clean, warm and humidify air
- lined with respiratory epithelium
Describe the mucocilary escalator in the trachea
Mucocilary escalator removed debris to the pharynx, to be swallowed and digested
- mucus from goblet cells and mucous glands coat surface of epithelium
- debris becomes trapped
- cilia move mucus to pharynx
Describe the features of the lungs
2 lungs
- 3 lobes on the right
- 2 lobes on the left (due to heart)
- Hilum: where bronchi and blood vessels enter
Hilum is a region on a solid organ where structures come in or out of
Apex of the lung: superior region (just above the clavicle)
Costal surface: lateral surface, against ribs
Base of the lung: inferior, sits on diaphragm
Describe the branches of the bronchial tree
- Trachea
- Primary bronchi (enter the lungs through the hilum)
- Secondary (lobar) bronchi (spilts into each lobe of the lung, so three branches on right and two on left)
- Tertiary (segmental) bronchi
- Bronchioles
- many many branches
- Terminal bronchioles (smallest of the bronchioles, they mark the end of the conducting zone)
Describe the physical structures for each of the branches of the bronchial tree
Trachea:
- respiratory epithelium
- C-shaped cartilage rings
- trachealis muscle at the posterior
Primary bronchi:
- respiratory epithelium
- cartilage and smooth muscle rings complete (to keep it open and to constrict and dilate)
Secondary and Tertiary bronchi:
- respiratory epithelium starts to decrease in height, goblet cell numbers reduce
- cartilage plates
Bronchioles <1mm:
- cuboidal epithelium
- no cartilage but thick smooth muscle from bronchoconstriction/dialtion
Terminal bronchioles <0.5mm
- each supplies a pulmonary lobule
Describe the features of the respiratory zone
- pulmonary lobules made of many alveoli (air sacs) arranged like bundles of grapes
- ~150 million alveoli per lung
- most of lung volume
- enormous surface area
- alveolar walls very thin: simple squamous epithelium on a thin basement membrane
- external surface of alveoli covered in fine network of pulmonary capillaries
Describe the features of alveolus (pl. alveoli)
- pocket-like - open at one side
- covered by a dense capillary network
- pneumocytes (lung epithelial cells)
- Type I squamous:
- forms the respiratory membrane/blood-air barrier with capillary wall and shared basement membrane - Type II squamous:
- scattered amongst Type I
- secrete surfactant, a complex lipoprotein (phospholipid) that reduces the surface tension of the alveolar fluid
- Type I squamous:
Describe the features of alveolus that can bee seen in a crossectional picture
- Type I pneumocyte: squamous epithelial cells, gas exchange
- Type II pneumocyte: cuboidal epithelial cells, produces surfactant
- Roaming macrophage: removed debris that makes it to alveoli (last line of defence)
- Respiratoy membrane
- capillary
- holes that connect to neighbouring alveoli
Describe the layers of the respiratory membrane from the air space to the blood space
- Alveolar air space
- surfactant coating alevolar surface
- alveolar cell layer
- fused basement membranes of alveolar epithelium and capillary endothelium
- capillary endothelium
- with nucleus of endothelial cells in it
- capillary lumen
- red blood cell
