Respiratory System - Hubs 192

The role of the respiratory system is to?

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

To be effective, the respiratory system needs:

• A surface for gas exchange - blood and air brought close together but separated

• A pathway for air to flow to reach the gas exchange surface in optimal condition

• Ability to draw breath in and out

• Plus: Sound production and Olfaction (smell)

The upper respiratory system is made up of?

• Nose

• Nasal cavity

• Paranasal sinuses

• Pharynx

The lower respiratory system is made up of?

• Larynx

• Trachea

• Bronchus

• Bronchioles

• Respiratory bronchioles

• Aveoli

Other main components of the Respiratory system Not included in URT or LRT

• thoracic cavity

• Joints

• Respiratory muscles

The four main areas of the respiratory system

• Nasal cavity : Olfaction

• oral cavity : Passage for air and food

• Conducting Zone : Nose to bronchioles, ensure air is warm, clean and moist

• Respiratory Zone : Bronchioles to alveoli sites of gas exchange

Epithelia in the respiratory system

• tract lined with mucus: Epithelium attached via basement membrane to lamina propria (CT)

• Epithelium changes along length of tract to reflect functions

Most of conducting regions are what kind of epithelium

Respiratory epithelium

Where air and food travel is what kind of epithelium

Stratified Squamous

Site of gas exchange is what kind of epithelium

Simple Squamous

Olfaction

Olfactory Mucosa

How much of the bodys organs are lined with mucosa?

Most body organs

Mucosa is

• epithelia

• Attached via a basement membrane to the lamina propria

Lamina Propria

• connective tissue

• May contain glands

Submucosal layer

• More connective tissue

• depending on region, may contain many glands

Where are Pseudostratified ciliated columnar epithelium (with goblet cells) located along the tract?

• Nasal Cavity

• Part of pharynx

• larynx

• trachea

• bronchi

Pseudostratified ciliated columnar epithelium (with goblet cells)

• Ciliated cells

• Goblet cells

• Basal cells

• Basement membrane

• Lamina propria

What do goblet cells produce

Mucus

What does mucus do to the air

• clean (traps debris) and moist

What is the role of ciliated cells

Move the mucus along the tract

• Patterned movement pushes mucus towards pharynx

• Swallowed and digested by stomach acid

different parts of the Pharynx

• Nasopharynx

• Oropharynx

• Laryngopharynx

Functions of The URT

• Conducting passage

  • Prepares air for respiratory membrane (gas exchange

    • Warm

    • Moist

    • Clean

  • Paranasal sinuses - resonating chambers for speech

  • Olfaction - sensory receptors

What is the primary passage way for air

The nose

What makes up the nose

• Cartilage - soft flexible, maintain patent (unobstructed) airway

• Nostrils - External nares

• Vestibule lined skin - has sebaceous and sweat glands, hair follicles, Vibrissae (hairs) filter inhaled air.

• 2 nasal bones in the bridge of nose (nasal bridges)

Bones of the Nasal Cavity

• nasal septum in midline

  • Anterior - cartilage

  • Posterior- bone

• Internal nares open into nasal pharynx

• Roof of cavity formed by ethmoid and shenoid bones

• Floor of cavity formed by hard and soft palates

• Conchae on lateral walls

What are the 3 projections of the Chonchae

• superior

• Middle

• Inferior

(turbinates)

Conchae

• the 3 projections are covered by respiratory epithelium

• Swirl inspired air

• Particles stick to mucosa

• More time for warming and humidifying of air, plus olfactory detection

Nasal Epithelium

• Nasal cavity

  • Mostly respiratory epithelium

  • Plus, specilized area of olfactory epithelium

    • Area on roof of nasal cavity, contains smell (olfactory) receptors

Nasal Mucosa

• Epithelium sits on lamina propria

• Thin-walled vascular plexus

• Helps warm incoming air

• Drop in air temp = dilated plexus = greater heat transfer

• Nose bleeds normally originate from damage here

Sinus

Cavity within a bone (normally filled with air)

Paranasal

Surrounding the nose

Paranasal Sinuses

• found within frontal, sphenoid, ethmoid and maxillary bones

• Lined with respiratory mucosa

• Drain into pharynx

What are the functions of Paranasal Sinuses

• Lighten skull

• Increased surface area to clean, moisten and warm air

• Sound resonance

• Infected mucus can block drainage = blocked sinuses

What section of the Pharynx is only for air

Nasopharynx

Description of the Pharynx

• Commonly called the throat

• Muscular funnel-shaped tube shared by respiratory and digestive system

Nasopharynx

• Air passage only (respiratory mucosa)

• Posterior to the nasal cavity

• From internal nares to soft palate

• Soft palate and uvula block the nasopharynx during swallowing to prevent food from entering the nasal cavity

• Auditory tubes drain here from middle ear

• Pharyngeal tonsils (adenoids) on the posterior wall

Oropharynx

• Air and food

  • Stratified squamous epithelium = protection against abrasion

• Posterior to oral cavity

• From soft palate to hyoid bone

• Palatine tonsils

• Lingual tonsils

Laryngopharynx

• Air and food

  • Stratified squamous epithelium

• From hyoid bone to opening of larynx/ beginning of esophagus

• Ends at level where respiratory and digestive tracts diverge

• Food has “right of way” during swallowing

Functions of the LRT

• Conducts air to/from the site of gas exchange

• Completes cleaning, warming and humidifying of air

• Provides a barrier between air and blood, and a large surface for gas exchange

Larynx

• passage of air only

• Anterior to esophagus

• From the hyoid bone to the trachea

• Cartilages protect and maintain an open airway (patent)

• Epiglottis closes over the airway when swallowing

Glottis

Voice box

Vocal folds

• True vocal cords

• passing air causes vibrations = sound waves

• Used for normal phonation

• testosterone affects cartilage and muscle, resulting in longer, thicker folds = deeper voice

Vestibular folds

• False vocal cords

• Superior to vocal folds

• Prevent foreign object entry to glottis

• can produce very deep sounds

Trachea

• anterior to esophagus

• Between the larynx and primary bronchi

• Respiratory epithelium

• C-shaped cartilage rings

• Trachealis muscle at posterior

Functions of the trachea

• Maintain patent airway

  • C-shaped cartilage rings

  • Ends connected by a band of smooth muscle: trachealis

    • Contracts for coughing

  • Many elastin fibres in lamina propria and submucosa

• clean, warm, moist air

  • Respiratory epithelium

The mucociliary escalator in the trachea

• removed debris to the pharynx, to be swallowed and digested

  • Mucus from goblet cells and mucous glands coat surface of epithelium

  • Debris becomes trapped

  • Cilia move mucus to pharynx

The lungs

• 2 lungs

  • 3 lobes on the right (Superior, middle and inferior)

  • 2 lobes on the left (Superior and inferior)

• Hilum: where bronchi and blood vessels enter

• The apex of the lung = superior region

• dome-shaped base of the lung = inferior sits on diaphragm at the bottom

• Costal surface= lateral surface, against ribs

Bronchial Tree

Trachea » 1 bronchi » 2 (lobar) bronchi » 3 (segmental) bronchi » bronchioles » a lot of branching » Terminal bronchioles

1 degree bronchi

• Respiratory epithelium

• cartilage and smooth muscle rings complete

2nd and 3rd degree bronchi

• Respiratory epithelium starts to decrease in height, goblet cell numbers reduce

• cartilage plates

Bronchioles <1mm

• cuboidal epithelium

• No cartilage but thick smooth muscle for bronchoconstriction/dilation

terminal bronchioles <0.5mm

• Each supplies a pulmonary lobule

respiratory zone

• Pulmonary lobules made of may alveoli arranged line bunches of grapes

• ~150 million alveoli per lung

  • Most of lung volume

  • Enormous surface area

• Alveolar walls very thin: simple squamous epithelium on a thin basement membrane

• External surface of alveoli covered in fine network of pulmonary capillaries

Alveolus

• pocket-like (open at one side)

• covered by a dense capillary network

• Pneumocytes (Lung epithelial cells)

• roaming macrophage - remove debris that makes it to alveoli

• respiratory membrane

• capillaries

• Connection to neighbouring alveoli

Type 1 squamous (Pneumocyte)

• forms the respiratory membrane/blood-air barrier with capillary wall and shared basement membrane

• Gas exchange

Type 2 cuboidal (Pneumocyte)

• scattered amongst type 1

• Secrete surfactant, a complex lipoprotein (phospholipid) that reduces the surface tension of the alveolar fluid

respiratory membrane

Alveolar air space

Surfactant coating alveolar surface

The blood-air barrier

capillary lumen

red blood cell

The blood air barrier consists of

• Alveolar cell layer

• Fused basement membranes of alveolar epithelium and capillary endothelium

• capillary endothelium (with Nucleus)

Body cavities

• our body cavities are lined with serous membranes

  • Double layer of secretory tissue with fluid between layers

    • Visceral layer on the organ

    • Parietal layer on body wall

• Thoracic cavity

  • Pericardium x1

  • Pleura x2 (one for each lung)

• Abdominopelvic cavity

  • Peritoneum

(separated by the diaphragm)

The thoracic cavity contains

• Mediastinum (heart, vessels, pericardium)

• Pleural cavities (Lungs) (lungs are separate so if one stops functioning, you have another)

Boundaries of the thoracic cavity

• Anterior: sternum

• Posterior: thoracic vertebrae (12)

• Lateral: ribs

• Superior: base of neck

• Inferior: diaphragm

walls of the Pleural cavities

• Pleural cavity

• Parietal pleura

• Visceral pleura

followed by the thoracic wall

Hilum of lung

Where 1 degree bronchus vessels enter

Ventilation is driven by

Pressure changes in thoracic cavity

• pressure is inversely proportional to volume

Boyle’s Law

P=1/V

• pressure inversely proportional to volume

• pressure measured by collisions

  • Smaller space = more collisions = increased pressure (Air flows out)

  • Bigger space = less collisions = decreased pressure (air flows in)

• Air will move to lower pressure space (pressure gradient)

• Between breaths pressure inside cavity = pressure outside (No gradient)

(provided temp and amount of gas molecules are kept constant)

Thoracic joints (anterior)

• sternum to Ribs - via costal cartilage (hyaline) - synovial joints and cartilaginous joints

• Sternocostal - synovial (except 1st = cartilaginous)

• Costochondral - cartilaginous

• Interchondral - synovial (joints are possible between bits of cartilage, allows for movement)

Thoracic Joints (posterior)

• Articulation between thoracic vertebrae and ribs

• synovial joints

  • Costotransverse - between rin and transverse process of vertebrae

  • Costovertebral - between rib and body of vertebrae

Joints allow movement to occur, but we need muscles to create the movement

Muscles of respiration

• respiratory muscles move the rib cage to allow us to breathe

• primary muscles of respiratory

  • Diaphragm

  • Intercostals

• Accessory muscles

  • Active only when needed

The diaphragm

• sheet of skeletal muscle

• Separates thorax from abdomen

• Dome-shaped when relaxed

• Flattened when contracted

• Contraction expands thoracic cavity, compresses abdominopelvic cavity

Intercostal muscles

• attach diagonally between neighboring ribs

• External intercostals

• Internal intercostals

External intercostals

• lift ribcage and expand cavity

• Inspiration - quiet and forced

Internal intercostals

• depress ribcage and decrease cavity

• Expiration- force only

Accessory Muscles

• Several muscles that attach to the thoracic cavity

Accessory Muscles collective functions

• some accessory muscles increase cavity volume for forced inspiration

• Other accessory muscles decrease cavity volume for forced expiration

Muscles of respiration: Inspiration

• during normal ‘quiet’ inspiration

  • Diaphragm contracts = flattens

  • External intercostals contract = lift ribs

• During active ‘forced’ inspiration

  • as above, plus accessory muscles contract to further expand thoracic cavity

Muscles of respiration: Expiration

• During normal ‘ quiet’ expiration

  • Passive process

  • diaphragm relaxes = dome shaped

  • External intercostals relax = ribs no longer lifted

• During active ‘forced’ expiration

  • Same as above plus:

  • Internal intercostals contract = depress ribs

  • Accessory muscles contract to further decrease cavity volume

How do the lungs expand as the cavity does?

• lung tissue is elastic and always trying to recoil

• The pleura make the lungs ‘stick’ to the thoracic wall

• Lungs expand during inspiration

• Lungs contract during expiration

Thoracic Movement: pleura

• Visceral pleura on lungs

• Parietal pleura on thoracic wall

• Pleural fluid in between

  • Slippery surface for frictionless movement against other structures

  • Fluid bond causes lungs to ‘stick’ to thoracic wall

• Thoracic wall movement results in lung movement

  • Increase volume of thorax » increase volume of lungs » decrease pressure in lungs» air flows in (opposite for air going out)

pressure gradient in the lungs

• Gas will move from high pressure to low pressure

• Right before a breath, the pressure outside the body and inside the lungs are equal, so no air is moving

what creates the pressure gradient

• as you inhale, your diaphragm drops while your rib cage expands

• this increases the volume in your chest, which lowers the pressure

• Direction of the airflow determined by difference between atmospheric pressure and intrapulmonary pressure

Inhalation

• Lung volume is increasing

• Pressure inside the lungs is decreasing

• Pressure outside the lung is now greater than inside, so air rushes in

Exhalation

• Lung volume is decreasing

• pressure inside the lungs is increasing

• Pressure outside the lung is now lower than inside, so air rushes out

2 opposing forces that must be over come to breath

• Stiffness of the lungs

  • Lungs must expand to take in air

  • How compliant are the lungs?

  • Surface tension holds lungs in place

• Resistance of the airway to the lungs

  • Need to move the air from outside to the alveoli

  • Hoe much resistance the respiratory system puts on the tract

Stiffness of the lungs is related to compliance

Defined as the magnitude of the change in the lung volume produced by the given change in the pressure

Compliance = V/P

Vital lung capacity = lung volume

Low compliance = stiff lungs (more work needed to expand)

Pulmonary Fibrosis

• Thickening and scarring of the alveolar membrane

• Can arise from chronic inflammation or exposure to industrial chemicals

Surface tension

Tendency of a fluid surface to occupy the smallest possible surface area

Fluids surrounding the lungs exert surface tension

• Alveoli are lined with fluid that exert surface tension

• Walls of alveoli are very thin, enhancing this effect

• Must overcome surface tension to expand lungs

Surfactant

reduces surface tension in alveoli (makes them easier to expand)

Surfactant produced by what type of pneumocytes

Type 2

• Major constituent is phospholipids

• Lower surface tension

  • reduces attractive forces between fluid molecules lining alveoli

  • Easier to increase lung size - increased compliance

Lack of surfactant / Failure to produce

• results in respiratory distress syndrome

• Premature infants do not produce surfactant- results in respiratory distress syndrome

Airway resistance through the respiratory tract

• need to move air from outside to the alveoli

• Air is conducted through the bronchi and bronchioles

• Exert force (friction) on the air that muct be overcome

Main area of airway resistance

Bronchi

Airway resistance in the Bronchi

• Most of the resistance to airflow arises in the bronchi

• The small airways (terminal and respiratory bronchioles) contribute very little to airways resistance (due to high cross-sectional area)

Spirometers

• measures volume inspired/ exhaled

• Common, simple test

• Can measure how much and how fast you breath

• Test response to therapy

Tidal volume

Volume of air moved in and out during normal quiet breaths

Inspiratory reserve volume

Extra volume that can be inhaled over and above the tidal volume

Expiratory reserve volume

Extra volume that can be exhaled voluntarily after completion of a normal, quiet respiratory cycle

Residual

Volume remaining in lungs after maximal exhalation

minimal volume

Volume remaining in lungs id they collapsed

Vital capacity

• Inspiratory reserve + Expiratory reserve + tidal volume

• Volume of air that can be moved in and out of your lungs