Lecture 14 - Respiratory system I - An overview and The Upper Respiratory Tract

Question 1

What is the role of the respiratory system?

Answer 1

Connected organs and structures that function to conduct warm, clean, moist air into close proximity with blood of the circulatory system for gas exchange

Question 2

For the respiratory system to be effective it needs…

Answer 2

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

Question 3

Main components of the respiratory system

Answer 3

Upper respiratory tract
Lower respiratory tract

Plus:
Thoracic cavity
Joints
Respiratory muscles

Question 4

Main components - nasal cavity

Answer 4

Olfaction

Question 5

Main components - oral cavity

Answer 5

Passage for air and food

Question 6

Main components - conducting region

Answer 6

Nasal cavity to bronchioles (URT and LRT)

Ensure air is warm, clean and moist

Question 7

Main components - respiratory region

Answer 7

Alveoli - little sacs deep down inside the lungs

Sites of gas exchange

Question 8

Epithelia in the respiratory system

Answer 8

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

Question 9

Epithelium of the conducting region

Answer 9

Most of the conducting region = respiratory epithelium

Question 10

Epithelium where air and food travel

Answer 10

Where air and food travel = stratified squamous

Such as the oral cavity
Protect against abrasion

Question 11

Epithelium at the site of gas exchange

Answer 11

Site of gas exchange = simple squamous

Want barrier to be as small and as thin as possible

Question 12

Epithelium at the site of olfaction

Answer 12

Olfaction = olfactory mucosa

Question 13

Respiratory epithelium = ________

Answer 13

Pseudostratified ciliated columnar epithelium (with goblet cells)

Question 14

Description of respiratory epithelium

Answer 14

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

Question 15

Lamina propria

Answer 15

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

Question 16

_______ and ______ are crucial components of the respiratory system

Answer 16

Cilia and mucus

Question 17

Why does your nose run on a cold day?

Answer 17

In cold temperatures, cilia will stop beating. With nothing to help move the mucus towards the pharynx, it can dribble out of your nose

Question 18

Why do we cough up mucus when we are unwell?

Answer 18

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

Question 19

Why do smokers cough?

Answer 19

Cigarette smoke paralyses and destroys cilia. This leads to mucus accumulation and coughing to try and dislodge it.

Question 20

Components of the upper respiratory tract

Answer 20

Nose and nasal cavity
Paranasal sinuses
Pharnyx - nasopharynx, oropharynx, laryngopharynx

Question 21

Functions of the upper respiratory tract

Answer 21

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

Question 22

Nose (URT)

Answer 22

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)

Question 23

Bones of the nasal complex

Answer 23

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

Question 24

Conchae

Answer 24

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.

Question 25

Nasal epithelium

Answer 25

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

Question 26

Nasal mucosa

Answer 26

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

Question 27

Paranasal sinuses

Answer 27

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

Question 28

Pharynx

Answer 28

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

Question 29

Nasopharynx

Answer 29

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

Question 30

Oropharynx

Answer 30

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

Question 31

Laryngopharynx

Answer 31

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

Question 32

What three qualities do we consider the optimum condition of air to be in?

Answer 32

Moist
Clean
Warm

Question 33

How does the URT facilitate the 3 qualities we consider the optimum conditions of air to be?

Answer 33

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

Question 34

What types of epithelium are found in the URT?

Answer 34

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