L22. Respiratory system structure and function Flashcards
Respiratory functions
- provide extensive surface area for gas exchange between air and circulating blood
- move air to and from exchange surfaces of lungs
- protect respiratory surfaces from dehydration, temperature changes, and pathogens
Conducting zones
- structures that don’t participate in gas exchange but provide rigid passageways that allow air to reach the alveoli
- includes: nose, nasal cavity, phyrynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles
Respiratory zone
- structures that actually participate in gas exchange
- includes: respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli
> alveoli are air-filled pockets within lungs where all gas exchange takes place
Organs of the respiratory system
3 groups:
- Airways for conduction
- Lungs for gas exchange
- Respiratory muscles for ventilation (breathing)
Nose and nasal cavity
ANATOMY:
- extends from nostrils to the choanae
- nasal cavity contains folds of tissue- superior, middle and inferior choncae
- covered in ciliated mucous membranes
- hair
FUNCTION:
- primary passageway for air entering respiratory system
- narrow passages ensure most inspired air comes in contact with the mucous membranes to:
> remove dust and bacteria
> warm and humidify air
> cilia sweep debris towards the pharynx to be swallowed and digested
Pharynx
ANATOMY:
- 3 regions
- L-shaped cavity
- Houses tonsils
FUNCTIONS:
- inspired air is forced to make a sharp 90 degree turn
- larger particles are trapped on the posterior wall of the nasopharynx mucosa
Larynx
ANATOMY:
- cartilaginous chamber
- aka: the “voice box”
- associated with the glottis, epiglottis and laryngeal muscles at the superior opening
FUNCTION:
- primarily to keep food and drink out of the trachea
- glottis, epiglottis and laryngeal muscles block off trachea opening during swallowing
Trachea anatomy
ANATOMY:
- tough, flexible tube, aka: the “windpipe”
- about 12cm long
- anterior to the esophagus
- supported by 16-20 cartilaginous C-shaped rings
- the gap faces posteriorly and is spanned by smooth muscle- Trachealis
- internal lining is covered with ciliated mucosa
- inferior end branches off into two primary bronchi
Trachea function
FUNCTION:
- goblet cells secrete mucous to trap particles
- ciliated cells beat in a wave-like manner to propel mucous upwards into pharynx
> MUCOCILIARY ESCALATOR
- cartilage rings are rigid structures that keep airways open
- trachealis muscles contract or relax to adjust tracheal airflow
- soft tissue allows for distortion of tracheal wall when swallowing
Bronchial tree
BRONCHIAL TREE
- resembles an up-side-down tree
- trachea (trunk)
- two primary bronchi (left and right)
Secondary bronchi -> tertiary bronchi
- approx 23 orders (branches off 23 times)
- contains progressively less cartilage and more smooth muscle
Bronchioles
- bronchi with < 1mm diameter
- have no cartilage
- respiratory bronchioles mark the begining of the respiratory division
> presence of alveoli
Bronchodilation
- caused by sympathetic activation
- enlarges luminal diameter of airway
- reduces airway resistance -> increases airflow
Bronchoconstriction
- caused by:
> parasympathetic activation
> histamine release (allergic reactions) - reduces luminal diameter of airway
- increases airway resistance -> decreases airflow
eg. asthma
Alveolar sacs
- grape-like clusters of alveoli
Alveoli
- tiny air sacs composed of a single squamous cell (type 1 alveolar cells)
> very thin for diffusion of gases - lungs contain approx 300 million alveoli
> huge surface area for gas exchange