biological role of respiration Flashcards
role of respiratory tract
- air condition
- air filtration
- gas exchange, respiration.
- speech production as air passes through the larynx.
- sense of smell as air passes over the olfactory mucosa in the nasal cavity
respiratory tract zones
conducting zone:
- majority of respiratory tract.
- conducts gases into and out of lungs
- consists of URT to the terminal bronchioles.
transitional zone:
- conduction and gaseous exchange
- respiratory bronchioles
respiratory zone:
- site of gaseous exchange
- respiratory bronchioles to the alveoli
pulmonary circulation
- is derived from the pulmonary trunk the leaves the right ventricle of the heart
- carries deoxygenated blood to the lungs
- pulmonary arteries divide into lobar and segmental arteries and travel with the bronchi and bronchioles to reach the capillary level at the alveoli
- blood is oxygenated at the level of the alveolus an collected by pulmonary venous capillaries.
- these ultimately form the 4 pulmonary veins that return blood to the left atrium of the heart.
bronchial circulation
- from bronchial arteries that branch from the aorta.
- supplies to larger components of the bronchial tree
- the finest branches of the bronchial arterial tree also open into the pulmonary capillaries
- therefore the bronchial and pulmonary circulations anastomose at about the level of the junction between the conducting and respiratory passages.
- bronchial veins drain only the connective tissue of the hilar region of the lungs
- most of the blood reaching the lungs via the bronchial arteries leaves the lungs via the pulmonary veins
upper respiratory tract
nasal cavity and paranasal sinuses provide a large surface area for warming and moistening inspired air, and trapping particulate matter.
pseudostratified ciliated columnar cells, with scattered mucus-secreting goblet cells [G]
nasal cavity
the lamina propria of the nasal epithelium contain many mucus-secreting glands. the mucus secreted by these glands forma a sheet of mucus on the epithelial surface which traps inhaled particles. this is then wafted by the cilia to the pharynx where it is either swallowed or expectorated
nasopharynx
has the typical respiratory epithelium: pseudostratified ciliated columnar epithelium with goblet cells.
within the submucosa is MALT [lymphoid tissue] important in defence mechanisms
olfactory epithelium
the olfactory mucosa:
- senses smell
- located in the roof of the nasal cavity.
- pseudostratified ciliated columnar epithelium with olfactory receptor cells
- Bowman’s glands penetrate the epithelium and their secretion may act as the solvent in which odorous substances dissolve
larynx
- comprises of epiglottis, false and true vocal cords
- epiglottis prevents food and drink entering respiratory tract.
- vibration of true vocal cords generates sound.
- true vocal cords and part of the epiglottis are covered by stratified squamous epithelium
- > all other laryngeal structures have typical respiratory epithelium
bronchi
similar to the trachea.
- pseudostratified ciliated columnar epithelium.
- seromucous glands
- variable amounts of smooth muscle [arranged in longitudinal bands]
- variable amounts of partial cartilaginous ring
bronchioles
- branch repeatedly
- reduce their luminal size
- decrease cartilage content
- increase smooth muscle within wall
- ciliated columnar epithelium [no pseudostratification]
- occasional goblet cells but no seromucous glands.
- club (Clara) cells
respiratory zone
the terminal bronchiole leads to the distal respiratory tree= gaseous exchange.
respiratory bronchioles:
- cuboidal ciliated epithelium
- merges with alveolar ducts.
the walls of these ducts are composed of alveoli openings.
- each alveolar duct terminates in two or three alveolar sacs, formed from the confluence of the openings of several alveoli
type 1 alveolar cells
- type I pneumocytes.
- comprise 40% of the alveolar lining cells
- extremely thin squamous cells.
- joined by occluding junctions.
- line most (95%) of the surface of alveoli
type II alveolar cells
- type II pneumocytes are secretory cells
- cuboidal cells are interspersed among the type I cells but tend to congregate at septal junctions.
- 60% of the alveolar lining cells, only cover about 5% of the alveolar air surface.
- rich in surfactant.
- also progenitor cells for type 1 alveolar cells
gaseous exchange
- alveoli are the terminal air spaces of the respiratory system
- each alveolus is surrounded by a network of capillaries that brings blood into close proximity to inhaled air in the alveolus.
- each alveolus (A) is a thin-walled polyhedral chamber approximately 0.2mm in diameter that is confluent with an alveolar sac (AS)
