LRT Flashcards
Functions of the LRT
Conducts air to/from the site of gas exchange. Completes cleaning, warming and humidifying air. Provides a barrier between the air and blood and a large surface area for gas exchange. Components include larynx, trachea, bronchi, bronchioles and alveoli
What is the larynx?
The larynx is a passage that only allows for air to go through. Spans from the hyoid bone to the trachea and is anterior to oesophagus. Functions to keep airway open and free of any obstructions (patent). Epiglottis closes over the airway when swallowing so food doesn’t enter - on top of the glottis
What is the glottis?
Glottis is the voice box, found below epiglottis, folds are attached to cartilages
What are the ‘true vocal cords’?
Vocal folds are the ‘true vocal cords’, air passes through causing vibrations (sound waves), used for normal phonation, testosterone affects cartilage and muscle resulting in longer, thick folds = deeper voice
What are the ‘false vocal cords’?
Vestibular folds are the ‘false vocal cords’, superior to vocal folds, prevent foreign object entry to glottis, can produce very deep sounds
What is the trachea?
The trachea is anterior to the oesophagus and is found between the larynx and primary bronchi. Mucus glands are present which can trap a large amount of debris hence cough out mucus from trachea
What is the function of the trachea?
It functions to maintain patent airway (C-shaped cartilage rings, ends connected by a band of smooth muscle, trachealis which contract for coughing, many elastin fibres in lamina propria and submucosa) and clean, warm and humidify the air (respiratory epithelium)
What is the mucociliary escalator?
Mucociliary escalator removes debris to the pharynx to be swallowed and digested. Mucus from goblet cells and mucous glands coat surface of epithelium. Debris becomes trapped and cilia move mucus to pharynx
Structure of the lungs
There are 2 lungs, 3 lobes on the right and 2 lobes on the left. Left only has two lobes as heart takes up space where third lobe would be. The hilum is where bronchi and blood vessels enter
Apex of the lung - superior region
Costal surface - lateral surface, against ribs
Base of lung - inferior, sits on diaphragm
Structure of the bronchial tree
Trachea spilts into two primary bronchi which further spilts into the secondary (lobar) bronchi, three for right and two for left, which further spilts into the tertiary (segmental) bronchi and continues to branch until terminal bronchioles reached - lowest order of the bronchi - which feed into the alveoli
Five structures in the bronchial tree
Trachea: made of respiratory epithelium, C-shaped cartilage rings, trachealis muscle at posterior
Primary bronchi: made of respiratory epithelium, cartilage and smooth muscle rings complete
Secondary and tertiary bronchi: respiratory epithelium starts to decrease in height, goblet cell numbers reduce, cartilage plates
Bronchioles <1mm: made of cuboidal epithelium, no cartilage but thick smooth muscle for bronchoconstriction/dilation
Terminal bronchioles <0.5mm: each supplies a pulmonary lobule
What is the respiratory zone?
Pulmonary lobules made of many alveoli (air sacs) ~ 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
What are alveoli?
Alveoli are pocket like - open at one side, covered by a dense capillary network. Pneumocytes: type 1 squamous (forms respiratory membrane/blood air barrier with capillary wall and shared basement membrane) type 2 cuboidal (scattered amongst type 1, secrete surfactant, a complex lipoprotein that reduces the surface tension of the alveolar fluid)
What are the structures of the alveoli?
Type 1 pneumocytes made of simple squamous epithelial cells which form the wall of alveoli
Type 2 pneumocytes are scattered along the type 1, they are cuboidal epithelial cells that keep the alveoli open
Roaming macrophage removes debris that make it to alveoli
Respiratory membrane is the wall of the capillary, has endothelium, shared basement membrane and wall of type 1 pneumocytes
In what order are the layers that oxygen and carbon dioxide pass through?
O2 travels from air space -> secretion from pneumocytes 2 -> basement membrane -> simple squamous epithelial -> capillary wall -> blood
CO2 travels from blood -> capillary wall -> simple squamous epithelium -> basement membrane -> secretion from pneumocytes 2 -> air space
