Respiratory System LO Flashcards
Describe the structure and function of the nose
Structure
- the anterior nares are the openings from the exterior into the nasal cavity
- the right and left nasal cavity separated by the nasal septum
- nasal cavity is lined with vascular ciliated columnar epithelium
- contains mucus secreting goblet cells and coarse hairs
Function
- nostrils are the main route of air entry into the respiratory system
- warms air flowing through due to vascularity
- filters and clears the air entering as large particles get caught in hairs and mucus
- humidification as air travels over moist mucosa it becomes more saturated with water vapour
Describe the structure and function of the pharynx
Structure
- MUCOUS MEMBRANE LINING - mucosa varies slightly in different areas
- in the nasopharynx its continuous with the nasal lining and consists of ciliated columnar epithelium
- oropharynx and laryngopharynx are lined with stratified squamous epithelium, continuous with lining of the mouth
- SUBMUCOSA - layer of tissue rich in mucosa-associated lymphoid tissue involved in immunity
- SMOOTH MUSCLE - pharyngeal muscles help to keep pharynx permanently open so breathing isn’t obstructed
Function
- warming and humidifying as air moves closer to the lungs
- hearing as air filled auditory connects to nasopharynx to the middle ear, keeping air at atmospheric pressure
- protection from infection as immune cells in the pharyngeal and laryngeal tonsils defend against swallowed or inhaled antigens
- speech as pharynx acts as a resonating chamber for sound
Describe the structure and function of the larynx
Structure
- thyroid cartilage - prominent and lies at the front of the neck. It’s anterior wall projects into the soft tissues in the throat form laryngeal prominence (Adam’s apple). Lower part has ciliated columnar epithelium
- cricoid cartilage - shaped like a signet ring, lined with ciliated columnar epithelium
- arytenoid cartilages - two pyramid-shaped hyaline cartilages on top of the cricoid cartilage, forming part of the larynx’s posterior wall. Give attachment to vocal cords and muscles, lined with ciliated columnar epithelium
- epiglottis - leaf-shaped firbroelastic cartilage covered in squamous stratified epithelium, attached to inner surface of anterior wall. Closes off the larynx during swallowing to protect the lungs
Function
- production of sound as vocal cords are vibrated by air moving up from the lungs
- speech as sounds from vocal cords are amplified and manipulated by the tongue, checks and lips
- protection of the lower respiratory tract as the epiglottis closes over the laryngeal opening so no food is inhaled into the lungs
- passageway for air as it links to the trachea below
Describe the structure and function of the trachea
Structure
- held open by rings of hyaline cartilage
- these rings are incomplete posteriorly where the trachea lies against the oesophagus
Made of three layers:
- outer layer contains fibrous and elastic tissue (protective and supportive)
- middle layer contains C-shaped cartilage and bands of smooth muscle (allows for limited adjustment of tracheal diameter)
- inner lining of ciliated columnar epithelium with mucus secreting goblet cells (produces respiratory secretions)
Functions
- support and patency as a sense of posterior cartilage allows the oesophagus to expand when swallowing
- mucociliary escalator which is the regular beating of the cilia, wafting mucus and adherent particles up, away from the lungs
- cough reflex as the nerve endings in the trachea generate nerve impulses conducted by the respiratory centre
- warming, filtering and humidifying as air is usually saturated and warm when it reaches the trachea
Describe the structure of the lungs
Apex - rounded tip of the lung that rises into the root of the neck
Base - inferior surface of the lung. Is concave and semilunar in shape. Attached to upper surface of the diaphragm
Costal surface - broad outer surface of the lung, lying directly against costal, ribs and intercostal muscles
Medial surface - medial surface of each lung face each other directly across mediastinum. Concave with a rough triangle shaped area called hilum
Visceral pleura - adhere to lung, covering each lobe. Folds back on itself near hilum to form parietal pleura
Parietal pleura - adheres to inside of chest wall and upper surface of diaphragm
Pleural cavity - enclosed space between visceral and parietal layers
Describe the structure and function of the bronchi and bronchioles
Right bronchus is wider, shorter and more vertical than the left bronchus
Structure
- cartilage - present support by as bronchi divide into smaller airways rings become smaller until there isn’t any
- smooth muscle - cartilage is replaced by smooth muscle, allows diameter of airway to increase and decrease through regulation of airflow via autonomic nervous system
- epithelial lining - ciliated epithelium gradually replaced by no-ciliated epithelium and goblet cells disappear
Function
- control of air entry due to bronchi being slightly smaller in diameter and the cartilage around it preventing that from altering so less air is able to enter
Describe the structure and function of the alveoli
Structure
- small sacs with walls 1 cell thick
- wrapped in elastic fibres to help recoil after inspiration
- surrounded by dense network of capillaries
Function
- where gas exchange takes place
Describe the position of the lungs
- two cone shaped lungs lying on each side of the midline in the thoracic cavity
- space between the lungs is called the mediastinum and contains the heart, great vessels, trachea, right and left primary bronchi, lymph nodes, vessels and nerves
- lungs not symmetrical as heart occupies left space of midline
- right sits slightly higher due to space occupied by liver
- each lung divided int subunits called lobes
Describe the conducting zone and respiratory zone of the respiratory tract
Conducting zone
- includes everything from nose to bronchioles
- moves air into and out of the lungs
Respiratory zone
- includes bronchioles and alveoli
- moves respiratory gasses (O2 and CO2) in and out of the blood
Describe the mechanisms of ventilation
INSPIRATION
- external intercostal muscles and diaphragm contracts simultaneously, enlarging thoracic cavity in all directions
- rib cage anchored to first rib, fastened firmly to the sternum and the first thoracic vertebra
- rib cage moves up and out expanding the thorax anteriorly and laterally
- when the diaphragm contracts its muscle fibres shorten and the central tendon is pulled down, lengthening the thoracic cavity
- parietal pleura adheres to diaphragm so is pulled out too, therefore, pulling the visceral pleura out too
- visceral pleura adhered to lung tissue so lung is pulled up and out with the ribs and down with the diaphragm
- this expands the lungs and pressure witching the alveoli and air passages falls drawing air into the lungs To equalise the atmospheric and alveolar pressure
EXPIRATION
- relaxation of external intercostal muscles and diaphragm results in rib cage moving down and in and elastic recoil of the lungs
- this increases pressure in the lungs and expels air from respiratory tract
- at the end of expiration the lungs still contain some air
- lungs are prevented from complete collapse by the intact pleura
- passive process and doesn’t require energy
Describe the role of the pleura
- The pleura consists of two layers: visceral pleura and parietal pleura
- With a gap between them called the pleural cavity
- It protects and cushions the lungs
Describe the surfactant and its role in the respiratory system
- lines the alveoli to lower surface tension
- enriched with phospholipids and proteins
Identify tidal volume, vital capacity and residual volume
Tidal volume - the amount of air passing into and out of the lungs during each cycle of breathing
Vital capacity - the maximum volume of air that can be moved into and out of the lungs
Residual volume - the volume of air remaining in the lungs after forced expiration
Describe peak expiratory flow (PEF)
- measured with a peak flow meter and records the maximum speed of air flow during forced expiration
- measured in litres per minute
- only attained for a fraction of a second
- normal range = 400-700 L/min
- values may vary with: age, sex and physical build
- depends on diameter of larger airways
- useful for assessing lung function in obstructive respiratory disorders e.g. asthma
Describe gaseous exchange
- exchange of gasses occurs when there’s a difference in partial pressure across a semipermeable membrane
- gasses diffuse from a higher to a lower concentration until equilibrium is established
- O2 diffuses out of the alveoli into the capillary
- CO2 diffuses out of the capillary into the alveoli
- alveoli has thin walls resulting in a short diffusion pathway
