Body Systems topic 3

Respiratory System

basic functions of the respiratory system overall (7)

1. Olfactory epithelium (olfactory receptors) for sense of smell

2. Produces sounds

3. Protects respiratory surfaces from dehydration, temperature changes,

   and pathogens

4. surface area for gas exchange between air and

   circulating blood

5. Moves air to and from exchange surfaces of lungs

6. Acid-base balance

7. Regulates pH

define respiration

Respiration is the exchange of gases between the atmosphere, blood, and cells.

what are the three basic steps of respiration?

1. Ventilation (breathing)

2. External (pulmonary) respiration

3. Internal (tissue) respiration

what is contained within the upper and lower respiratory tract

Upper respiratory tract is:

• above vocal cords:

  • nose, nasal cavity

  • paranasal sinuses

  • pharynx

Lower respiratory tract is

• below vocal cords:

  • larynx

  • trachea

  • bronchi

  • bronchioles

  • alveoli

what componants are in the respiratory portion and which are in the conducting system of the respiratory system as a whole

The conducting system consists of:

• a series of cavities and tubes

  • nose

  • pharynx

  • larynx

  • trachea

  • bronchi

  • bronchiole

  • terminal bronchioles

The respiratory portion consists of:

• the area where gas exchange occurs

  • respiratory bronchioles

  • alveolar ducts

  • alveolar sacs

  • alveoli.

define what anatomic dead space is?

It is the air in the conducting portion of the airways which does not take part in the process of gas exchange.

explain the role of the nose in the respiratory system (what are nasal hairs, pathway of air, functions)

Nasal hairs:

• in epithelium of vestibule - trap large particles in air (filters)

---

• Skin, nasal bones and cartilage lined with mucous membrane

• internal portion communicates with the paranasal sinuses and nasopharynx

  through the internal nares

---

Functions:

• warming, moistening, and filtering incoming air

• receiving olfactory stimuli

• serving as large, hollow resonating chambers to modify speech sounds

what are the paranasal siinuses

• Open into nasal cavity

• They lighten the skull and resonate voice

• There are ethmoid, sphenoid, frontal and maxillary sinuses

What are the tonsils (where and roles)

Where:

• at entrance of the respiratory tract

Roles:

• Are lymphatic tissues protect against infection.

• Lymph nodes monitor lymph drainage from lungs and provide specific defenses when infection occurs.

decribe the pathway of air through the nose

1. nose vestibule to choanae (internal openings of nasal cavity to pharynx)

2. through superior, middle, and inferior nasal meatuses

   • trap particles

   • warm and humidify

   • bring olfactory stimuli to receptors

Describe the structure of the nasal cavity

• divided into right and left by nasal septum (bones + cartilage)

• roof of ethmoid bone

• floor is hard plate

• superior, middle, and inferior nasal conchae on lateral walls

Describe the two palates in the nasal/oral cavity

Hard palate

• forms floor of nasal cavity separates nasal and oral cavities

Soft palate

• extends posterior to hard palate divides superior part of the pharynx (nasopharynx) from rest of pharynx

structure/location of pharynx + role

STRUCTURE

• skeletal muscular tube

• lined with mucous membrane

• comprised of three regions:

  • nasopharynx - respiration

  • oropharynx - digestion and respiration

  • laryngopharynx - digestion and respiration

LOCATION

• extends from internal nares to cricoid cartilage

ROLES

• resonating chamber for speech production

• Tonsils in the walls protect entry in body

What is the nasopharynx?

From choanae to soft palate

• openings of Eustachian (auditory) tubes from middle ear cavity

• adenoids or pharyngeal tonsil in roof

passage for airway only

What is the oropharynx

• between the soft plate and epiglottis

• common passageway for food and air

what is the laryngopharynx

Extends from epiglottis to cricoid cartilage, and ends as esophagus inferiorly

• Common passageway for food and air

What is the larynx

• Connects the pharynx with the trachea

• contains the:

  • thyroid cartilage

  • epiglottis

  • cricoid cartilage

• produces sound

• Opening and closing of the vocal folds occurs during breathing and speech

Explain what the thyroid cartilage is

adams apple

what is the epiglottis

a leaf-shaped piece of elastic cartilage which prevents food from entering the larynx.

• During swallowing, larynx moves upward, epiglottis bends to cover glottis

what is the cricoid cartilage

• a ring of cartilage connects larynx and trachea

explain the process of voice production in the larynx

Speech is a modified sound made by the larynx → requires pharynx, mouth, nasal cavity and sinuses to resonate sound

1. Vocal folds (true vocal cords) - produce sound

   • Taut vocal folds produce high pitches

   • Relaxed vocal folds produce low pitches

   • Vestibular folds (false vocal cords) found above vocal folds

explain how whispering occurs?

Whispering is forcing air through almost closed rima glottidis - oral cavity alone forms speech.

Tongue and lips movements form words

What is the true vocal cord?

• contains skeletal muscles

• contains elastic ligaments

• when muscles contract of the larynx contract → the cartilage moves and vocal chords are stretched tight.

  • when air is pushed past tight ligament = sound.

what is laryngitis

Is an inflammation of the larynx - usually caused by respiratory infection or irritants.

explain what the trachea is?

• From larynx → T5 anterior → oesophagus → splits into primary bronchii

  • composed of smooth muscle and c shaped rings of cartilage (keep airway open)

  • lined by pseudostratified epithelium

• cilia remove debris from lungs → throat to be swallowed.

what is a tracheostomy? and intubation

TRACHEOSTOMY

is incision in trachea below cricoid cartilage if larynx is obstructed

• Reestablished airflow past an airway obstruction

INSTUBATION:

• is passing a tube from mouth or nose through larynx and trachea

Explain the location of the lungs inside the thoracic cavity

1. Enclosed and protected by the pleural membrane:

   • Parietal pleura: outer layer attached to wall of thoracic cavity

   • Visceral pleura: inner layer covering lungs

   • Pleural cavity is potential space between the pleurae, contains a lubricating fluid secreted by the membranes

2. Lungs extend from the diaphragm to just slightly superior to the clavicles

3. lie against the ribs anteriorly and posteriorly

4. Lungs almost totally fill the thorax

What is visible from the costal surface of the lungs?

• apex

• base

• costal surface of right and left lung

• right lung = 3 lobes separated oblique and horizontal fissures.

• left lung = 2 lobes separated by oblique fissure and a cardiac notch (depression)

order of branching of the bronchial tree

trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, terminal bronchioles.

bronchioles → alveoli order

Branchings of single arteriole, venule and bronchiole are wrapped by elastic connective tissue - respiratory bronchioles are also wrapped by smooth muscles that can change diameter of these airways.

1. respiratory bronchiole → alveolar ducts → alveolar sacs → alveoli → alveolar pores

change in cartilage structure as bronchi branch

• When passing deeper into the lungs

  • Incomplete rings of cartilage replaced by rings of smooth muscle (bronchioles)

  • then replaced by connective tissue

Histology summary of respiratory system

CONDUCTION COMPONANT -

• Transports, cleans, warms, and humidifies air.

• Nose, pharynx, larynx, trachea, bronchi, terminal bronchioles

• ciliated pseudostratified columnar epithelium

RESPIRATORY PORTION

• Gas exchange (O2/CO2 diffusion)

• Respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli

• progresses from ciliated cuboidal epithelium to squamous epithelium.

histological composition of the respiratory system cells and functions

1. Epithelial cells - lined with basal cells that are attached to the basement membrane

2. Squamous epithelial cells - make up the beginning (nasal) and ends (alveoli) of the respiratory tract.

3. Ciliated and non-ciliated columnar epithelia - Upper tract and large bronchi

4. cuboidal epithelia - Small bronchi and bronchioles

5. Surface liquid - overlays the epithelial cells, is mucus, airway liquids, neutralising immunoglobulins, and antimicrobials

6. Resident leukocytes - line the mucosa, alveolar macrophages are found in lower airways and alveoli

7. Bronchiole smooth muscle cells - underlying the respiratory tract from the basal end provide structural support and elasticity to the airways.

4 layers of the trachea

1. mucosa - pseudostratified columnar epithelium with cilia and goblet cells

2. submucosa - loose connective tissue and seromucous glands

3. Hyaline cartilage - incomplete rings C-shaped structure closed by trachealis muscle

4. Adventitia - binds it to other organs

what is required for effective mucociliary drainage

• normal cilia

• optimum thickness and viscosity of mucous.

what causes increased and decreased mucocilary drainage

INCREASED:

• intense exercise

• postural drainage

• percussion

• nebulisation

DECREASED

• old age

• sleep

• disease

• dry cold air

explain what cystic fibrosis is?

The airways fill with thick sticky mucus, making it difficult to breathe.

• the thick mucus is an ideal breeding ground for bacteria

• affects mostly the lungs and digestive system

explain what asthma is?

Asthma is characterised by spasms of smooth muscle in bronchial tubes that result in partial or complete closure of air passageways

Can lead to:

• inflammation

• inflated alveoli

• excess mucus production.

Symptoms

• cough

• wheeze

• shortness of breath

• chest tightness

Can treat with nebulisation therapy

what is nebulisation therapy

Nebulisation therapy = inhale mist with chemicals that relax muscle and reduce thickness of mucus.

What are the types of alveolar cells?

Type 1 cells:

• simple squamous cells - gas exchange

Type 2 cells (septal cells):

• free surface has microvilli

• secrete alveolar fluid containing surfactant

Alveolar Macrophages:

• remove debris

Alveolar-capillary membrane

Respiratory membrane = 1/2 micron thick

• Vast surface area for gas exchange from alveoli to blood

This air-blood barrier is composed of:

• alveolar and capillary walls

• their fused basal laminas

Define respiration and the tree basic steps

Respiration: exchange of gases between atmosphere, blood, and cells.

Occurs in 3 basic steps:

1. Pulmonary ventilation (breathing)

2. External (pulmonary) respiration: all processes involved in exchange of O2 and CO2 with the external environment

3. Internal (tissue) respiration: uptake of O2 and release of CO2 by cells

Compare hypoxia to anoxia

Hypoxia

• Low tissue oxygen levels.

Anoxia

• Complete lack of oxygen in tissues.

Explain what pulmonary ventilation is

A mechanical process that depends on volume changes in the thoracic cavity.

• Volume changes lead to pressure changes, which lead to the flow of gases to equalise pressure.

Inspiration = Air in lungs < atmospheric pressure

Expiration = Air out Lung > Atmospheric pressure

What is Boyle’s Law?

Boyle’s law: the volume (V) of a gas varies inversely with pressure (P), assuming that temperature is constant.

• P = pressure of gas in mm Hg

• V = volume of a gas in cubic millimeters

P_InitialV_Initial = P_FinalV_Final

P = 1/V

Explain the role of a change in thoracic cavity size in respiration

1. when breathing in the thoracic cavity increases

   • contraction of the diaphragm, flattens, increases chest vertical dimenstions

   • contraction of the intercostal muscles, increases anterior-posterior dimension of the chest

2. When breathing out the thoracic cavity shrinks

muscles in expanding thoracic cavity inhalation

sterocleidomastoid

scalenes

external intercostals

diaphragm

muscles in relaxing/shrinking thoracic cavity exhalation

• internal intercostals

• external oblique muscles

• internal oblique muscles

• transverse abdominis

• rectus abdominis

compare intrapulmonary pressure and intrapleural pressure

Intrapulmonary pressure (Ppul) = pressure within the alveoli

• always eventually equalises with atmospheric pressure

Intrapleural pressure (Pip) = pressure within the pleural cavity

• intrapleural pressure is always less than intrapulmonary pressure and atmospheric pressure.

• both fluctuate with breathing phases

when does lung collapse occur?

• is caused by equalisation of the intrapleural pressure with the intrapulmonary pressure

• 2 forces pull the lungs away from the thoracic wall, promoting lung collapse

  • Elasticity of lungs causes them to assume smallest possible size

  • Surface tension of alveolar fluid draws alveoli to their smallest possible size

what is Transpulmonary pressure?

• keeps airways open

• Transpulmonary pressure = difference between the intrapulmonary and intrapleural pressures (Ppul – Pip)

define inspiration? how?

• the movement of air into the lungs.

• occurs when

• alveolar pressure < atmospheric pressure.

• intrapulmonary pressure < atmospheric pressure

HOW?

• diaphragm and external muscles increase the size of the thorax, intrapulmonary volume increases and pressure decreases below atmospheric prssure

• Air flows into the lungs, down its pressure gradient, until intrapulmonary pressure = atmospheric pressure.

forced vs quiet inspiration?

QUIET INSPIRATION

• Diaphragm contacts 1 cm and ribs lifted by external intercostal muscles.

• intrathoracic pressure falls and air is inhaled

FORCED INSPIRATION

• Accessory muscles of inspiration (sternocleidomastoids, scalenes, and pectoralis minor) lift chest upwards as you gasp for air.

sequence of event for inspiration

1. inspiratory muscles contract

2. thoracic cavity volume increases

3. intrapulmonary volume increases

4. intrapulmonary pressure drops

5. air flows into lungs down conc. gradient until = atmospheric pressure

expiration summary

• the movement of air out of the lungs.

• when alveolar pressure > atmospheric pressure

• also an inward pull of surface tension due to the film of alveolar fluid

quiet vs forced EXPIRATION

QUIET:

• Passive process with no muscle action

• Elastic recoil and surface tension in alveoli pulls inward.

• Alveolar pressure increases and air is pushed out

FORCED:

• Abdominal mm force diaphragm up

• Internal intercostals depress ribs

sequence of events for EXPIRATION

1. inspiratory muscles relax

2. thoracic cavity volume decreases

3. elastic lungs recoil passively

4. intrapulmonary volume decreases

5. intrapulmonary pressure rises

6. air flows out of lungs

relationship between flow F pressure P and resistance R in airways

F = P/R

air resistance and sympathetic nervous system

• Sympathetic nervous system stimulates the adrenal gland to release epinephrine (adrenaline) that relaxes smooth muscle and dilates airways

• thus, reducing air resistance

resistance in respiratory passageways

• depends on airway size

define surface tension and apply explain what alveolar surface tension is

Surface tension: the attraction of liquid molecules to one another at a liquid-gas interface

• The liquid lining the alveoli creates surface tension that acts to minimise surface area, tending to shrink or collapse the alveoli

role of surfactant in reducing alveolar surface tension (what happens in premature babies)

• Surfactant = a detergent-like substance, produced by Type II alveolar cells

  • Surfactant is a substance produced in the lungs that keeps the tiny air sacs (alveoli) open and stable

• premature babies

  • Respiratory Distress Syndrome - Insufficient surfactant in premature babies causes alveoli to collapse at the end of each exhalation

    • work harder to breathe

define lung compliance

refers to the ability of the lungs to stretch and expand.

• A measure of the change in lung volume.

  • High compliance → easier to expand lungs.

  • Low compliance à→harder to expand lungs.

what are the two main factors which affect lung compliance?

1. Distensibility of the lung tissue and surrounding thoracic cage

   • high volumes = compliance is low

     • elastic tissue stretched - more effort required to stretch it further

1. Surface tension of the alveoli

   • low volumes = compliance low

     • surfactant decreases surface tension, increases compliance.

which factors can diminish lung compliance?

1. scar tissue

2. blocked respiratory passages (fluid/mucus)

3. reduced surfactant production

4. low flexibility of thoracic cage

what are factors which affect the work of breathing?

1. the metabolic needs of the body

2. the force exerted by the lungs to overcome the resistance of air flow

3. rate at which respiratory muscles need to generate force (respiratory rate)

what is a pulmonary function test?

spirometer and spirogram

spirometer vs spirogram?

spirometer - measures Air volumes exchanged during breathing and rate of ventilation

Spirogram - the record produced.

what is respiratory minute volume?

Total volume of air taken in one minute

• Respiratory minute volume (VE) = respiratory rate × tidal volume

• measures pulmonary ventilation

what is alveolar ventilation?

Alveolar ventilation (VA) = respiratory rate × (tidal volume - anatomic dead space)

• amount of air reaching alveoli per min

• Alveoli contain less O2 than atmospheric air because inhaled air mixes with “used” air

how to increase alveolar ventilation rate?

• increase tidal volume

• increase respiratory rate

what are the different lung volumes?

1. tidal volume

   • amount air moved during quiet breathing

2. Reserve volumes

   • amount you can breathe either in or out above that amount of tidal volume

   • inspiratory and expiratory reserve volumes IRV and ERV

3. Residual volume

   • amount of air in lungs after maximal exhalation which is permanently trapped in the system

4. minimal volume

   • air trapped in a collapsed lung

what are the types of lung capacity?

1. Inspiratory capacity

   • tidal volume + inspiratory reserve volume

2. Functional residual capacity

   • expiratory reserve volume + residual volume

3. Vital Capacity

   • expiratory reserve volume + tidal volume + inspiratory reserve volume

4. Total lung capacity

   • vital capacity + residual volume

what are obstructive vs restrictive pulmonary diseases

Obstructive pulmonary diseases

make it more difficult to get gas out of the lungs = affect expiratory airflow.

Restrictive pulmonary diseases

make it more difficult to get gas into the lungs = affect inspiratory airflow

explain FEV and FVC in the pulmonary function test

FEV - forced expiratory volume in 1 second:

• volume of air exhaled in the 1st second during forced exhalation after maximal inspiration

• measured using spirometry

FVC - forced vital capacity

• maximum amount of air you can forcibly exhale from lungs after fully inhaling.

• used to differentiate between obstructive/restrictive lung disease

compare the FVC and FEV of obstructive and restrictive diseases

Obstructive

FVC - normal

FEV - decreased

Restrictive

FVC - decreased

FEV - normal

explain the flow-volume loops pulmonary function test process

Procedure: performed with the patient breathing into a pneumotachograph.

• Maximal breath in

• Forced aggressive expiration

• Maximal fast breath in

what is a peak expiratory flow rate?

The maximum speed of expiration, as measured with a peak flow meter

• Peak flow readings are higher when healthy, lower when airways are constricted.

what is a pleural cavity injury

the sealed cavities are opened to the outside

• pneumothorax - fill with air

• hemothorax - fill with blood

explain daltons law

1. Each gas in a mixture of gases exerts its own pressure as if all the other gases were not present

2. Each gas contributes to total pressure in proportion to its relative abundance

Partial pressure (p) = pressure contributed by a single gas in a mixture

Total pressure (P) = the sum of all partial pressures

define air composition

The amounts of O2 and CO2 vary in inspired (atmospheric), alveolar, and expired air.

• Alveolar air has less O2 since absorbed by blood

explain what henry’s law is (gas laws)

about diffusion between liquids and gasses

• When gas under pressure contacts a liquid, pressure forces gas molecules into the solution.

Henry’s law = the amount of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility coefficient (its physical or chemical attraction for water), when the temperature remains constant.

Equilibrium:

• gas molecules diffuse out of liquid as quickly as they enter it.

• number of gas molecules in solution is constant.

what are some phenomena explained by henry’s law?

• narcosis

• motion sickness

• why you can breathe compressed air while scuba diving despite 79% nitrogen.

• decompression sickness (in divivers)

clinical application of henry’s law?

hyperbaric oxygenation

• involves breathing pure O2 in a pressurised environment

• treat decompression sickness, heart disorders, carbon monoxide poisoning etc.

what is the V/Q ratio?

• V = ventilation = the amount of air you breathe in

• Q = Perfusion = blood blow

• V/Q ratio = the amount of air that reaches lungs divided by the amount of blood flow in the capillaries in lungs.

increased perfusion in the lungs - decreases V/Q

decreased perfusion in the lungs - increases V/Q

VQ ratio on healthy individual

3.3 at the apex, 1at the middle lung, 0.63 at the base

From high to lower air ventilation (more at top apex of lung then bottom base)

what is a V/Q mismatch

an abnormal V/Q ratio, part of the lung receives oxygen without blood flow or blood flow without oxygen

can cause:

• hypoxemia (low O2 in blood)

  • respiratory failure

what is the respiratory rate?

number of breaths per minute

what is tidal volume?

amount of air moved per breath (ml)

how to calculate respiratory volume?

Respiratory minute volume (VE) = respiratory rate × tidal volume

• Total volume of air taken in one minute

• Measures pulmonary ventilation

what is repiratory minute volume (Ve) set to match

the needs of:

• must match metabolic requirements (O2 delivered CO2 removed)

• exercise - Ve increases → hyperpnoea (abnormally deep respiration)

• hyperventilation (rapid and deep) - ventilation excessive - pCO2 decreases

what is the unit for blood gas levels?

1 Torr = 1mmHg

• Torr is a non-SI unit of pressure

internal vs external respiration?

Internal:

• occurring inside the cells

External:

• between alveolus and capillary

how does the rate of diffusion of gasses change with altitude - why?

pO2 - rate of diffusion decreases as altitude increases.

what affects diffusion rate in lungs

• alveolar surface area

• diffusion distance (cells between)

O2 and Co2 which diffuse faster

O2 diffuses faster through membrane

• co2 more easily dissolved in fluids though

how to restore V/Q ratio if perfusion to an area of the lung falls?

• To restore V/Q matching we need to decrease ventilation

  • via bronchocontriction

• Decreased blood flow results in decreased ventilation.

how to restore V/Q ratio if ventillation to an area of the lung falls?

To restore V/Q matching we need to decrease perfusion

• via vasoconstriction

Decreased ventilation results in decreased perfusion.

• Decreased ventilation results in decreased perfusion.

Causes of hypoxemia - (Abnormal arterial blood gases (bad))

Causes of hypoxemia (hypoxaemia = low O2 levels in blood)

• insufficient O2 in the alveoli

  • low o2

  • insufficient ventillation

• insufficient diffusion from alveoli into blood

• imbalance between ventilation of alveoli and blood flow to alveoli

  • V/Q mismatch

what causes Hypocarbia or hypocapnia

Is a decrease in alveolar and blood pCO2 below 35 mmHg

caused by:

• excessive removal of CO2 from the body

• Ventilation removes CO2 so hypocapnia is due to hyperventilation