Respiratory System

Ventilation of the lung and gas exchange

Cardiovascular system

• gas excahnge,
• regulate blood pH
• produces vocal sounds
• excretes excess water and heat
• filters out impurities in air
• sense of smell

to produce ATP, which is the energy needed for all metabolic activity

a byproduct from metabolic reactions.

produces acidity

Carbonic acid H2CO3 which can turn to bicarbonate ion HCO3 + H. So as CO2 increases, so does the H, so you become too acidic. We then breather faster to try to expel more CO2

• Conducting portion (conducts air into lungs, filters, warms and moistens air) and:
• Respiratory portion where gas exchange occurs

nose, pharynx, larynx,trachea, bronchi, bronchioles and terminal bronchioles

tissues within the lungs where gas exhange occurs: respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

Presure changes coming from muscle relaxation and contraction

• Pulmonary ventilation (breathing),
• external respiration
• transport
• internal respiration

breathing, moving air in and out.

gas exchange between lungs and blood; blood in pulmonary capillaries gain O2 and lose CO2

transportation of oxygen and carbon dioxide between the lungs and tissues by the systemic blood vessels.

gas exchange between the systemic blood vessels and tissues. Blood in systemic capillaries loses O2 and gains CO2, while blood in tissue loses CO2 and gains O2.

when tissues lose CO2 and gain O2

2 sets of muscles between the ribs

external intercostal muscles

internal intercostal muscles

dome shaped muscle between thoracic and abdominal cavities

flattens and increases the volume in the thoracic cavity. This increase in volume means a decrease in pressure so air rushes in

inspiratory muscles contract (diaphragm descends, rib cage expands), thoracic cavity increases increasing volume and lowering intrapulmonary pressure, air flows down pressure gradient into lungs until pressure equal with outside pressure.

inspiratory muscles relax (diaphragm rises), thoracic cavity volume decreases which increases pressure so air flows down pressure gradient to the outside until intrapulmonary pressure is zero.

flows out

the air we breathe in and out during normal respiration

is your maximum inhale, the most air you can inhale at a time.

Extra volume that can be maximally exhaled following normal tidal exhalation.

this is the air that remains in your lungs after you have exhaled as much as you can

• all the air remaining in your lungs after a tidal exhalation.
• Sum of Residual Volume + Expiratory Reserve Volume

total volume of air inhaled and exhaled in one minute. Equals tidal ventilation x number of breathes per minute.

is the most you can breathe in and breath out. So your inspiratory capacity (including tidal) and the expiratory reserve

it is all the lung capacites, incl the residual capacity.

It refers to the partial pressure in the lungs or blood stream

lung volumes exchanged during breathing and rate of respiration.

It is the sum of all partial pressures in air. If atmospheric pressure is 760 then partial pressure for O2 is 21% x 760 (air is 21% oxygen)

In a mix of gases, parital pressure is the pressure exerted by each gas in the mixture. If the partial pressure is higher, there is more gas. So 100mmHg contains more O2 than 40mmHg

more oxygen in alveoli (about 104 vs 40mmHg) which means O2 moves very quickly from alveoli to blood (about 0.25 seconds)

to oxygenate the deoxygenated blood

in tissues throughout the body. O2 diffuses from systemic capillaries into pheripheral tissue cells; CO2 diffuses in opposite direction.

• surface area available
• partial pressure difference
• diffusion distance
• molecular wieght and solubility of gases

98.5% is attached to haemoglobin (this is the haeme part), and 1.5% is dissolved in plasma

• 7% is dissolved in plasma
• 70% dissolved as bicarbonate ions
• 23% bound to haemoglobin (globin part)

easier

Blood pH decreases (due to increase in H ions concentration); Chemoreceptors in medulla oblongata (central) and in aortic and carotid bodies (peripheral) detact change; send msg to inspiratory area in medulla oblongata; msg to effectors in diaphragm and internal intercostal muscles to increase respiratory rate and total volume so more CO2 expelled; less CO2 means fewer H ions so blood pH increases: homeostasis returned.

area in conducting airways containing air that doesn't undergo gas exchange

Medullary rhythmicity area within the medulla oblongata. It has 2 parts: inspiratory and expiratory areas.

during quiet breathing it controls the basic rhythm. Usually 2 secs inhalation (on) and 3 seconds exhalation (off).

helps with forced expiration

natural tendency of thoracic walls and lungs to spring back once they have been stretched. Normal expiration requiries no muscle contraction, relies on elastic recoil.

• warms and moistens incoming air
• detects olfactory stimuli
• modifies speech

usually through the external naris. These are 3 ridges inside the nasal cavity called conchae and they filters, warm and humidify incoming air.

Manages food and air coming down laryngopharynx. Prevents food entering trachea, protects vocal cords and ventricular folds.

passageway for food and air, resonating chamber for speech and houses tonsils. Divided into nasopharynx, oropharynx and layngopharynx.

Participates in immunological reactions against foreign invaders.

short passageway connecting larynogopharnx with trachea

Adam's apple; forms anterior wall of larynx and gives it a triangular shape.

Between cricoid and thyroid cartilage

ventricular folds: superior pair that protects vocal folds

inferior pair of vocal folds.

the vocal folds vibrate and produce sounds when stretched, narrowing the glottis.

windpipe

Trachea - primary bronchi - secondary bronchi - tertiary bronchi - bronchioles - terminal bronchioles

Cartilage becomes less and finally none; smooth muscle increases as amount of cartilage decreases;

• Upper respiratory tract – nose, pharynx and associated structures.
• Lower respiratory tract – larynx, trachea, bronchi,
• lungs.

• Conducting zone – interconnecting cavities and airways that moisten air and conduct it into the lungs- nose, pharynx, larynx, trachea,
• bronchi, bronchioles, terminal bronchioles.

• Respiratory zone – areas of
• the lung where gas exchange takes place (must have alveoli)-respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli.

External nares, through superior, middle and inferior meatuses which are grooves between the superior, middle and inferior conchae of the nasal vestibule, internal naris. The nasal cavity is divided into left and right sides by the nasal septum.

• 1. Warm, moisten filter air,
• (2) detect olfactory (smell) stimuli, (3) resonance of speech vibrations.

• superior, middle and inferior
• conchae

Production of mucus, resonating chambers for voice production, lightens bones of skull.

Nasopharynx, Oropharynx, Laryngopharynx. Oro and laryngopharynx have shared respiratory and gastrointestinal function.

Epiglottis, larynx, cricoid, arytenoid (x2)

Vocal folds (true vocal cords) are involved in sound production; ventricular folds (false vocal cords) protect the vocal folds and close the glottis (space between vocal and ventricular folds) during straining to lift or defecate.

arytenoid

• To close off the glottis during swallowing to
• prevent food entering the larynx and trachea

esophagus

• Between the ends of the C shaped cartilage of the
• trachea; to allow expansion and contraction of trachea during inhalation/exhalation and allow food bolus to pass through esophagus (immediately posterior) more easily during swallowing.

• Specialised last tracheal cartilage band that
• forms the bifurcation into left and right primary bronchi.

• Primary (lung) to secondary (lobar) bronchi to tertiary
• (segmental) bronchi . Further branching but not specifically named.

The conducting zone

Generally decreses in thickness from columnar to cuboidal to squamous with progression to alveoli. Nasal cavity and nasopharynx=pseudostratified ciliated columnar epithelium; oro- and laryngopharynx = stratified squamous epithelium; larynx (below vocal folds), trachea and bronchi= pseudostratified ciliated columnar epithelium; larger bronchioles=ciliated simple columnar epithelium; terminal bronchioles= simple cuboidal epithelium; alveoli=simple squamous epithelium

Cartilage decreases with progression through airways. Trachea & primary bronchi =C shaped/incomplete rings; smaller bronchi = plates of cartilage in wall; bronchioles=no cartilage in wall.

Left = 2 lobes; Right=3 lobes

• Parietal pleura lines thoracic cavity; visceral pleura
• covers lung; pleural cavity between with serous fluid

Each lung is enclosed in a separate double layered pleural membrane and they are separated by mediastinum.

• Reduce friction between membranes allowing
• them to slide easily during breathing.

Base sits on diaphragm; apex is just above clavicle, hlius is found on medial surface (facing mediastinum) and is where primary bronchi enter lung and blood vessels enter and exit

A terminal bronchiole terminates the conducting zone; a respiratory bronchiole has at least one alveoli in its wall and starts the respiratory zone.

alveolar duct

Type 1 Alveolar cell=simple squamous epithelial cell that forms the alveolar wall; Type II alveolar cell= rounded epithelial cells that secrete alveolar fluid with surfactant.

Surfactant is a mixture of phospholipids and lipoproteins which lowers surface tension of alveolar fluid and reduces the tendency for alveolar collapse.

Diaphragm

Contraction of the diaphragm (and external intercostal muscles).

• External intercostal muscles, sternocleidomastoid,
• scalenes

Internal intercostals, abdominals

Pleural cavity

• Elastic recoil is the natural tendency for elastic
• structures to spring back after being stretched. The surface tension of alveolar fluid and recoil of lung elastic fibres that where stretched during inhalation contribute to elastic recoil.

inward force tending to collapse alveoli caused by polar water molecules that are attracted to each other

a measure of how easily the lungs can be stretched, pressure difference required to cause a change in volume.

resistance to flow caused by friction between air molecules and airway wall.

• surface tension –reduction of surface tension reduces effort required to inflate alveoli therefore ventilation increases for given level of effort.
• lung compliance- high compliance=less effort (pressure difference) required to ventilate lung; low compliance =(stiff lung), more effort required to ventilate lung.
• airway resistance- increased resistance (airway
• narrowing) requires more effort to maintain ventilation.

Dalton’s law each gas in a gas mixture exerts its own pressure as if no other gases were present, ie. in proportion to the % of the total gas mixture it occupies.

Because the solubility of CO2 is 24 times greater than that of oxygen.

External respiration –O2 moves from alveolus to pulmonary capillary blood and CO2 from pulmonary capillary to alveolus

Internal respiration -O2 moves from systemic capillary blood to tissues and CO2 from tissues to systemic capillary blood

The partial pressure difference for O2 , gas will move from a region of high partial pressure to a region of lower partial pressure.

PO2 drops because atmospheric pressure drops with altitude, O2 still occupies 21% of air mix but total pressure is reduced.

The partial pressure of oxygen; the higher the PO2 the more O2 combines with Hb.

The percentage saturation of haemoglobin at any specific PO2 level

Affinity describes ease or the ‘tightness’ with which Hb binds O2.

As PCO2 increases and pH decreases the affinity of Hb for O2 declines. As temperature increases the affinity of Hb for O2 decreases.

These changes, increased temperature, more CO2 production and hence a decrease in pH, all occur during exercise. When you are exercising it is advantageous for the affinity of Hb for O2 to decrease so that more oxygen can be delivered to the exercising tissue. This is a useful way to remember the direction of change to Hb affinity.

• CO2 + H2O
• H2CO3
• H+ + HCO3-

Pons and medulla- medullary rhythmicity centre in medulla oblongata, pneumotaxic area in pons, apneustic area in pons

Phrenic nerves

• Apneustic area –send stimulatory signals to the
• inspiratory area that cause long, deep inhalation.

• Pneumotaxic area – transmits inhibitory signals to
• inspiratory area to shorten inhalation and prevent lungs becoming too full of air

• Central =In or near medulla oblongata; peripheral=
• carotid and aortic bodies

40mmHg

Increased level of PCO2 above normal (40mmHg).

Depth and frequency of breathing increase in negative feedback mechanism to reduce PCO2

They increase rate and depth of breathing as soon as muscles start moving

Stretch receptors in the bronchial/bronchiolar walls prevent overinflation of the lungs by inhibiting the inspiratory area

7.35-7.45

Buffer systems, exhalation of CO2, excretion of H+ in urine

Protein- buffers both acids (H+ added to NH2 when H+ high) and bases (H+ released from COOH when H+ low), Hb buffers H+ when O2 has been released

Bicarbonate- HCO3- buffers H+ to form H2CO3 when H+ high, H+ released from H2CO3 when H+ is low

Increase H+ so decreased pH

• Acidosis-condition in which blood pH is less than 7.35
• alkalosis-condition in which blood pH is greater than 7.45

• Acidosis- CNS depression via decreased synaptic
• transmission, disorientation, coma, death

Alkalosis- CNS and PNS overexcitability caused by increased synaptic transmission, causes muscle spasms, convulsions, death.

respiratory rate