Lecture 14 - Respiratory system I - An overview and The Upper Respiratory Tract Flashcards
What is the role of the respiratory system?
Connected organs and structures that function to conduct warm, clean, moist air into close proximity with blood of the circulatory system for gas exchange
For the respiratory system to be effective it needs…
A surface for gas exchange - blood and air close together but are still separated as you don’t want them mixing
A path for air to flow to reach the gas exchange surface in optimal condition
Ability to draw breath in and out
Plus
Produce sound
Olfaction - smell
Main components of the respiratory system
Upper respiratory tract
Lower respiratory tract
Plus:
Thoracic cavity
Joints
Respiratory muscles
Main components - nasal cavity
Olfaction
Main components - oral cavity
Passage for air and food
Main components - conducting region
Nasal cavity to bronchioles (URT and LRT)
Ensure air is warm, clean and moist
Main components - respiratory region
Alveoli - little sacs deep down inside the lungs
Sites of gas exchange
Epithelia in the respiratory system
Tract is lined with mucosa - epithelium attached via basement membrane to lamina propria (CT) (this is a supporting layer for the epithelia
Epithelium changes along length of tract to reflect function
Most of the conducting region = respiratory epithelium
Where air and food travel = stratified squamous
Site of gas exchange = simple squamous
Olfaction = olfactory mucosa
Epithelium of the conducting region
Most of the conducting region = respiratory epithelium
Epithelium where air and food travel
Where air and food travel = stratified squamous
Such as the oral cavity
Protect against abrasion
Epithelium at the site of gas exchange
Site of gas exchange = simple squamous
Want barrier to be as small and as thin as possible
Epithelium at the site of olfaction
Olfaction = olfactory mucosa
Respiratory epithelium = ________
Pseudostratified ciliated columnar epithelium (with goblet cells)
Description of respiratory epithelium
Pseudostratified (fake layers) ciliated (have cilia) columnar (tall and narrow) epithelium (with goblet cells)
Found in - nasal cavity, part of pharynx (naso is respiratory and oro and laryngo are stratified squamous), larynx, trachea and bronchi
Goblet cells produce mucus - traps debris, moistens air (these are two of the three optimal conditions of air)
Mucus is sticky and has lots of water in I
Ciliated cells …
Patterned movement pushes mucus towards pharynx
Swallowed and digested by stomach acid
Lamina propria
A thin layer of connective tissue that forms part of the moist linings known as mucous membranes or mucosa, which line various tubes in the body, such as the respiratory tract
_______ and ______ are crucial components of the respiratory system
Cilia and mucus
Why does your nose run on a cold day?
In cold temperatures, cilia will stop beating. With nothing to help move the mucus towards the pharynx, it can dribble out of your nose
Why do we cough up mucus when we are unwell?
Normally produce 1-2 litres of mucus a day. When we are sick, the body produces more so we cough to help the cilia to move the mucus
Why do smokers cough?
Cigarette smoke paralyses and destroys cilia. This leads to mucus accumulation and coughing to try and dislodge it.
Components of the upper respiratory tract
Nose and nasal cavity
Paranasal sinuses
Pharnyx - nasopharynx, oropharynx, laryngopharynx
Functions of the upper respiratory tract
Conducting passage (not only air, also food)
Prepares air for respiratory membrane (gas exchange) - warm, clean and moisten air
Paranasal sinuses - resonating chambers for speech
Olfaction - sensory receptors smell
Nose (URT)
Primary passage for air
Cartilages
Soft, flexible
Maintain patent/unobstructed airway
However the bridge of the nose is made up of bone - 2 nasal bones
Nostrils
External/anterior nares (nostrils)
Vestibule lined with skin - part you can stick your finger in, stratified squamous therefor protective
Has sebaceous and sweat glands, hair follicles
Vibrissae (hairs) filter inhaled air (first line of defence against any debris)
Bones of the nasal complex
Nasal septum in midline
Anterior = cartilage
Posterior = bone
Internal/posterior nares open into nasal pharynx
Roof of cavity formed by ethmoid and sphenoid bonds
Floor of cavity formed by hard and soft palates
Conchae on lateral walls
Conchae
Three projections - superior, middle and inferior conchae (turbinates - makes the air turbulent)
Covered by respiratory epithelium
Swirl inspired air
Particles stick to mucosa
More time for warming and humidifying of air, plus olfactory detection
long, narrow, curled shelf of bone that protrudes into the breathing passage of the nose
They increase the surface area of these cavities, thus providing for rapid warming and humidification of air as it passes to the lungs.
Nasal epithelium
Nasal cavity
Mostly respiratory epithelium
Plus area of olfactory mucosa - area on roof of nasal cavity, contains smell (olfactory) receptors (highly specialised cells that sit on the superior side of the nasal cavity and detect smell, dendrites detect the smell and pass it. Up through the receptor cells off to the nerve fibres and then off to the brain
Nasal mucosa
Epithelium sits on lamina propria (connective tissue layer)
Plexus of thin walled veins
Helps to warm incoming air (radiation) - important for more efficient gas exchange
When air temperature drops, vascular plexus dilates = greater heat transfer
Nose bleeds normally originate from here
Paranasal sinuses
Sinus = cavity within a bone (normally air filled) Paranasal = surrounding the nose
Tiny air spaces between the layers of bone
Found within frontal, sphenoid, ethmoid and maxillary bones
Lined with respiratory mucosa
Drains into pharnyx
Functions:
Lighten the skull
Increased surface area to clean, warm, moisten air
Sound resonance
Infected mucus can block drainage = blocked sinuses
Pharynx
Muscular funnel shaped tube shared by the respiratory and digestive system
Commonly called the throat
Three regions: (names are given based on the what the structures are sitting posterior to)
Nasopharynx (air passage ONLY)
Oropharynx
Laryngopharnyx
Nasopharynx
Air passage only - respiratory mucosa (doesn’t need to worry about abrasion from food)
Posterior to nasal cavity
From posterior nares to soft palate
Soft palate and uvula block nasopharynx during swallowing to prevent food entering nasal cavity
Auditory tubes drain here from middle ear
Pharyngeal tonsils (adenoids) (lymphoid tissue) on posterior wall
Oropharynx
Air and food - stratified squamous epithelium to protect against abrasion from food
Posterior to oral cavity
From soft palate to hyoid bone (hyoid bone breaks during strangulation)
Palatine tonsils
Lingual tonsils
Laryngopharynx
Air and food - stratified squamous epithelium to protect against abrasion
From hyoid bone to opening of larynx/beginning of oesophagus
Ends at level where respiratory and digestive tracts diverge
Food has right of way during swallowing
What three qualities do we consider the optimum condition of air to be in?
Moist
Clean
Warm
How does the URT facilitate the 3 qualities we consider the optimum conditions of air to be?
Moist, clean, warm are the three qualities that are the optimum conditions of air
Vestibule contrains vibrisse to trap large particles
Goblet cells produce mucus to trap particles within nasal cavity and nasopharynx
Cilia push mucus to pharynx where it is stalled and digested
Mucus moistens air, and vascular plexus below mucosa warms the air
Conchae (turbinates) make air turbulent to have more contact with mucosa
What types of epithelium are found in the URT?
Skin in vestibule of nose
Respiratory mucosa (pseudostratified ciliated columnar epithelium with goblet cells) in nasal cavity and nasopharynx
Olfactory mucosa in nasal cavity
Stratified squamous in oropharynx and laryngopharynx
