Ch. 19 - The Respiratory System

Question 1

Describe the primary functions of the respiratory system

Answer 1

Intake of O2 and removal of CO2

• cells need O2 to break down nutrients, to release ATP.
• CO2 results from this process, and must be excreted.

Tubes filter incoming air while transporting it into and out of the lungs.

Gases are exchanged in microscopic air sacs.

Respiratory organs:

• entrap incoming air particles,
• Filtration of incoming air
• Control air temperature
• Control water content of the air
• Production of vocal sounds
• Regulation of blood pH
• Sense of smell

The first 2 steps of the respiration process are handled by the respiratory organs:

1 - Intake of O2 and removal of CO2.
Movement of air into and out of the lungs, called pulmonary ventilation/breathing, involves inward movement/inspiration and outward movement/expiration.

2 - Gas exchange between the air in the lungs and the blood, or ‘External Respiration.’
O2 diffuses from the lungs to the blood, whereas CO2 diffuses from the blood to the lungs

Steps 3 and 4 are carried out by the cardiovascular system

3 - Gas transport in blood between the lungs and the body cells, accomplished by the cardiovascular system, using blood as transporting fluid.
O2 transported from the lungs to the body’s tissue cells, whereas CO2 transported from tissue cells to the lungs

4 - Gas exchange between the blood and the cells, or ‘Internal Respiration.’
O2 diffuses from the blood to the body’s tissue cells, whereas CO2 diffuses from the tissue cells to the blood

ALL 4 processes must occur for the respiratory system to obtain O2 and eliminate CO2.
If either fails, the cells of the body will die from lack of O2.

Question 2

Describe Spirometry

Answer 2

Pulmonary function testing.

measure respiratory volumes/capacities.

Originall a spirometer was used, now a small electronic measuring device is used instead.

Electronic spirometry is used for evaluating lost respiratory function, and respiratory disease progression.

Question 3

Identify the 4 distinct respiratory volumes

Answer 3

1 - TIDAL VOLUME(TV) - approx. 500ml air moves in and out of the lungs with each normal, quiet breath

2 - INSPIRATORY RESERVE VOLUME(IRV) - between 2100-3200ml of air can be be forcibly inspired, beyond the tidal volume

3 - EXPIRATORY RESERVE VOLUME(ERV) - 1000-1200ml of air can be expelled from the lungs beyond normal tidal volume expiration

4 - RESIDUAL VOLUME(RV) - after the most strenuous expiration of air there is still about 1200ml remaining, to prevent lung collapse and keep alveoli open. This is referred to as being ‘patent’.

Question 4

Respiratory Capacities

Answer 4

Also used for diagnosing problems with pulmonary ventilation:

• TOTAL LUNG CAPACITY = TOTAL OF ALL COMBINED RESPIRATORY VOLUMES - maximum air contained in lungs after maximum inspiratory effort
• VITAL CAPACITY = TIDAL VOLUME + INSPIRATORY RESERVE VOLUME + EXPIRATORY RESERVE VOLUME - maximum air that can be expired after maximum inspiratory effort.
• INSPIRATORY CAPACITY = TIDAL VOLUME + INSPIRATORY RESERVE VOLUME - maximum air that can be inspired after normal tidal volume expiration.
• FUNCTIONAL RESIDUAL CAPACITY = RESIDUAL VOLUME + EXPIRATORY RESERVE VOLUME - air remaining in the lungs after normal tidal volume expiration.

Question 5

Describe dead space

Answer 5

A certain amount of inspired air doesn’t contribute to alveolar exchange but fills the conducting respiratory passageways.

‘Anatomic Dead Space’ is made up of the volume of these conduits, and is approximately 150ml.

eg. only 350ml of air are used in alveolar ventilation, out of the tidal volume of 500ml.

Question 6

Identify the organs of the Upper Respiratory System

Answer 6

• Nose
• Nasal Cavity
• Paranasal Sinuses
• Pharynx

Question 7

Describe the functions of the Nose

Answer 7

allows air to enter and leave via the nostrils

filtering/cleaning air

resonating chamber for speech

olfactory/smell receptors

Question 8

Describe the functions of the Nasal Cavity

Answer 8

divided left/right by Nasal Septum

helps to warm(capillaries) and moisten the air(mucus)

lined with respiratory mucosa that contains goblet cells which secrete mucus to trap dust and other small particles, and is then pushed by the cilia of the epithelial lining towards the pharynx

mucus contains lysozymes, that destroy bacteria

respiratory mucosa also secrete defensins, which function like natural antibiotics, killing invading micro-organisms.

rich supply of nerve ending in mucosa that trigger the sneeze reflex on contact with irritants, air is forced outward violently, effectively expelling the irritant.

Question 9

Describe the functions of the Paranasal Sinuses

Answer 9

ring of air-filled spaces inside the skull bones opening into nasal cavity

located inside the maxillary, frontal, ethmoid and sphenoid bones

lined with mucous membranes that are continues with those of the nasal cavity

reduces the skull’s weight

affects the quality of the voice by resonance

help to warm and moisten incoming air

mucous produced in sinuses eventually flows to nasal cavity

when you blow your nose the suction effect that is created drains your sinuses

Question 10

Describe the functions of the Pharynx

Answer 10

funnel shaped

commonly called the throat

behind oral cavity, connects nasal cavity to the larynx

extends approx. 13cm from base of skull to level of sixth cervical vertebra

carries food from the oral cavity to the oesophagus

allows air to pass from the nasal cavity to the larynx

helps produce the sounds of speech

Nasopharynx - located above the mouth, continuous with nasal cavity, assists mucosal transport

Pharyngeal Tonsil/Adenoids - posterior wall of nasopharynx, traps pathogens from incoming air and destroys them

Oropharynx - continuous with oral cavity via archway called ‘isthmus of the faucet’, both air and food pass through, extends inferiorly from soft palate to epiglottis, contains 2 Palatine Tonsils and the Lingual Tonsil

Laryngopharynx - allows air and food to pass, lies posterior to epiglottis, extends to the larynx where respiratory/digestive pathways separate

Question 11

Describe the functions of the Larynx

Answer 11

enlargement in the airway above trachea and below pharynx

commonly called voice box

approx 5cm in length, extending from level of 3rd-6th cervical vertebra

attached superiorly to hyoid bone, opening into laryngopharynx

continuous with trachea inferiorly

controls how air/food are passed into proper channels

houses the vocal chords and produces the voice

conducts air into and out of, whilst preventing foreign objects entering the trachea

consists of muscle and 9 cartilages bound by elastic tissues consisting of intrinsic ligaments and membranes

all laryngeal cartilages except the epiglottis are hyaline cartilage

2 cartilage plates fuse to form the Thyroid Cartilage, resembling a shield in shape, at its midline a laryngeal prominence/ Adams apple exists, ,makes up most of anterior/lateral surface of larynx

ring shaped cricoid cartilage inferior to thyroid cartilage and above trachea to which it is anchored inferiorly

part of the lateral and posterior walls are formed by 3 pairs of Arytenoid, Cuneiform and Corniculate Cartilages, of which the pyramid Arytenoid cartilages are most important as they anchor the vocal folds

Epiglottis is flap-like structure extending from the tongues posterior aspect to where it is anchored on the thyroid cartilage, allows larynx to control whether food/air passes, when swallowing larynx rises and the epiglottis presses downward covering the opening to the larynx and preventing food/liquid from entering airway, epiglottis is spoon shaped-highly elastic-almost covered with mucosa that contain taste buds

during breathing the larynx is wide open and the free edge of the epiglottis projects upward, anything besides air that enters, triggers a cough reflex so the substance can be expelled

under the laryngeal mucosa, on each side, are highly elastic ‘vocal ligaments’ that attach the arytenoid cartilages to the thyroid cartilage, they form horizontal vocal folds inside the larynx, extend inward and are divided into:

• upper ‘false’ vocal chords/vestibular folds that create no sound, help close airway during swallowing
• lower ‘true’ vocal chords that actually create sound when air is forced between them, causing them to vibrate side to side, appear pearly white due lack of blood vessels, using the tongue and lips to change the shape of the pharynx, transforms sound waves into words

during breathing the glottis is a triangular slit between the vocal chords, when food or drink is swallowed the glottis closes to prevent it entering the trachea

Question 13

Describe the functions of the Trachea

Answer 13

the trachea is approx. 2cm diameter tube, approx 10-12cm in length.

trachea has layers known as:

• mucosa - ciliated, goblet cells in epithelium, moves trapped particles up into pharynx to be swallowed
• submucosa - connective tissue layer containing seromucous glands
• adventitia - outermost layer of connective tissue, encasing rings of hyaline cartilage

inside the trachea are approx. 20 pieces of ‘C’ shaped hyaline cartilage - open ends toward the spine- that prevent the trachea from collapsing, with the soft tissue near the spine allowing expansion of the oesophagus as food moves down it.

the open posterior part of the rings are connected by smooth muscles in the trachealis, as well as soft connective tissue, when the trachealis contracts the diameter of the trachea increases and expired air is caused to rush upward from the lungs, helping to expel mucous when coughing

a cartilage structure called the carina projects posteriorly from the final tracheal cartilage, at this point the trachea branches into the 2 primary bronchi

Question 14

Discuss the structure of the airway outside of the lungs -Bronchi and Subdivisions

Answer 14

branched airways leading from the trachea to the alveoli make up the Bronchial Tree.

these branches begin with the right and left primary bronchi near level of 5th thoracic vertebra

the Right Bronchus/Bronchus Dexter, is wider, shorter and more vertical than the Left Bronchus/Bronchus Sinister.

right bronchus branches to upper lobe of right lung, this known as eparterial branch as it arises above the right pulmonary artery, it then passed below the artery at the hyparterial branch and divides into 2 branches for the middle and lower lobes.

left bronchus has no eparterial branch because there is no 3rd lobe in the left lung.

the primary bronchi, divide into secondary/lobar bronchi, then into tertiary bronchi, and even finer tubes.

bronchioles are smaller tubes(less than 1mm in diameter) that continue to divide into terminal bronchioles(less than 0.5mm in diameter).

Question 15

Describe the functional anatomy of the alveoli

Answer 15

thin-walled microscopic air sacs inside capillary networks of the lungs.

they provide a large surface area of epithelial cells that allow easy exchange of gases.

O2 diffuses from the alveoli into the capillaries, and CO2 diffuses from the blood into the alveoli.

alveoli walls mostly made up of 1 layer of squamous epithelial cells/type 1 alveolar cells surrounded by a thin respiratory basement membrane.

within the basement membrane are scattered, cuboidal type II alveolar cells, that secrete surfactant, coating the alveolar surfaces that are exposed to gas. These cells also secrete antimicrobial proteins, needed for innate immunity.

Question 16

Describe the major steps involved in external respiration

Answer 16

external respiration consists of ventilation, which is the movement of air from outside of the body into and out of the bronchial tree and alveoli.

Phrenic nerve impulses stimulate the diaphragm to contract, moving downward.

The thoracic cavity enlarges, internal pressure falls, and atmospheric pressure forces air into the airways.

as the diaphragm contracts, the external intercostal muscles contract.

the ribs raise and the sternum elevates.

during normal inspiration, when inside pressure decreases, atmospheric pressure pushes outside air into the airways.

the lungs expand in response, and the thoracic wall moves upward and outward.

there is an opposing effect in the alveoli.

Question 17

Define and compare the processes of external respiration and internal respiration

Answer 17

external respiration is defined as gas exchange between air in the lungs and the blood
- O2 diffuses from the lungs to the blood, whereas CO2 diffuses from the blood to the lungs

internal respiration is defined as gas exchange between the blood and the cells
- O2 diffuses from the blood to the body’s tissue cells, whereas CO2 diffuses from the tissue cells to the blood

Question 18

Explain the important structures of the respiratory membrane

Answer 18

alveoli consist of a tiny space within a thin wall, separating it from the adjacent alveoli.

inner lining is made up of simple squamous epithelium.

dense networks of capillaries are found near each alveoli.

at least 2 thicknesses of epithelial cells and a fused basement membrane layer separate the air in the alveolus from the blood in a capillary.

these layers make up the respiratory membrane, it is here that blood and alveolar air exchange gases.

Question 19

Describe how O2 is picked up, transported, and released in the blood

Answer 19

in the lungs, about 98% of O2 dissolves and rapidly binds to the iron-containing protein haemoglobin in red blood cells forming oxyhemoglobin, whose bonds are unstable.

the remainder dissolves in the plasma along with CO2 from the cells.

as the partial pressure of O2 decreases, oxyhemoglobin molecules release O2, which diffuses into nearby cells that have depleted their O2 supplies in cellular respiration.

haemoglobin that has released O2 is referred to as reduced haemoglobin or deoxyhemoglobin.

a haemoglobin molecules’ shape alters after the first O2 molecule binds to the iron, it will then take up 2 more O2 molecules more easily, with uptake of a 4th easier still.

a haemoglobin molecule is partially saturated when 1-3 O2 molecules are bound, and fully saturated when all 4 of its heme groups are bound to O2.

unloading of a single O2 molecule, enhances the unloading of the next, and the next, meaning that although loading and unloading are opposite processes, functionally they are similar.

as blood becomes more acidic, or blood temp. rises, CO2 increases in the blood, causing more release of O2.

Question 20

Briefly describe stimulation of respiration rate

Answer 20

Deep breathing is referred to as diaphragmatic breathing.
Shallow breathing is known as costal breathing.

Depth of inspiration during breathing is based on the level of activity of the respiratory centre and its stimulation of motor neurone that serve the respiratory muscles.
More stimulation = increased no’s of motor units are excited, and respiratory muscles contract with greater force.
Respiratory rate is established by length of time the inspiratory centre is active or how fast it is turned off.

Question 21

Briefly list factors that affect respiration rate

Answer 21

Certain chemical affect the respiratory rate and depth.
Important substances in the arterial blood include:
- carbon dioxide
- hydrogen ions
- oxygen ions

Other factors include:

• emotional states
• lung stretching capability
• levels of physical activity

Question 22

Describe chemical stimulus of respiration rate

Answer 22

Chemosensitive area known as ‘Central Chemoreceptors’ in the medulla oblongata, sense carbon dioxide and hydrogen ion changes in the cerebrospinal fluid.
When the levels change, respiratory rate and tidal volume are signaled to increase.
More CO2 is exhaled, and both blood and cerebrospinal fluid levels of these chemicals fall, decreasing the breathing rate.

CO2 is the most important chemical regulator of respiration. Arterial partial pressure of CO2 is usually 40mmHg and it is maintained within 3mmHg of this, mostly by how CO2 levels rising, affects the central chemoreceptors.

Hypercapnia=CO2 accumulates in the brain. The accumulating CO2 is hydrated, and carbonic acid is formed. When the acid is dissociated, H ions are freed and pH drops, the same thing happens when CO2 enters red blood cells.
Increased H ions excite the central chemoreceptors, which synapse with the respiratory regulatory centres, and breathing rate and depth increase.
Because alveolar ventilation is enhanced, CO2 is quickly flushed out of the blood, and pH rises. Alveolar ventilation is doubled with an elevation of only 5mmHg in arterial pressure of CO2. This is true even when there is no change in arterial O2 levels or pH.

The response to elevated partial pressure of CO2 is more extensive when partial pressure of O2 and pH are lower than normal.

Increased ventilation is usually self limiting, and stops when there is restoration of homeostatic blood partial pressure of CO2.

Rising levels of H ions in the brain increase the activity of central chemoreceptors, even though rising blood CO2 is the 1st stimulus.
H does not easily diffuse across the blood-brain barrier, but CO2 does, therefore, control of breathing, while resting is mostly based on regulation of H ion concentration in the brain.

Peripheral chemoreceptors in the carotid and aortic bodies help to sense changes in blood O2 levels, then increase respiration rate, but this requires extremely low levels of blood O2 to occur.

Depth of breathing is regulated by the ‘inflation reflex’, this occurs when stretched lung tissues stimulate stretch receptors in the visceral pleura, bronchioles and alveoli.
Duration of inspiratory movement is shortened, preventing overinflation of lungs during forceful breathing.
Emotional upset like fear/pain increase respiration rate.
If breathing stops, even for a short time, blood levels of CO2 and H ions rise, and O2 falls.
Chemoreceptors are stimulated, increasing urge to inhale, in order to overcome lack of O2

‘Deflation reflex’ only functions during forced exhalation, inhibiting the expiratory centres while stimulating the inspiratory centres when the lungs are deflating.

Question 23

Describe how partial pressure of O2 influences respiration

Answer 23

peripheral chemoreceptors contain cells that are sensitive to arterial levels of O2.

these chemoreceptors are in the aortic body of the aortic arch, and the carotid body at the bifurcation of the common carotid arteries.

those in the carotid bodies are the main O2 sensors.

normally reducing partial pressure of O2 only affects ventilation minimally, primarily involving enhanced sensitivity or peripheral receptors to increased partial pressure of CO2.

for O2 levels to become a strong stimulus for increased ventilation, arterial pressure of O2 must drop greatly, to at least 60mmHg.

Question 24

Describe how arterial pH influences respiration

Answer 24

even when levels of O2 and CO2 are normal, change to arterial pH can alter the rate and rhythm of breathing, with increased ventilation occurring because reduced arterial pH is controlled via the peripheral chemoreceptors.

This is in part due to H ions not crossing the blood-brain barrier. Changes in partial pressure of CO2, and H ion concentration are related yet different.

reduced blood pH might be related to CO2 retention, but may occur because of metabolic reasons, such as:

• lactic acid accumulation due to exercise
• fatty acid metabolite/ketone body accumulation due to uncontrolled diabetes mellitus

no matter the reason, as arterial pH declines, the respiratory system attempts to compensate and raise the pH, by an increase of respiratory rate and depth, in an attempt to eliminate CO2 and carbonic acid from the blood.

Question 25

Describe how higher brain centres influence respiration

Answer 25

respiratory rate and depth modify when pain or strong emotions send signals to the respiratory centres.

this occurs via the limbic system, including the hypothalamus.

changes in body temp. also affect respiration, with hot temps. increasing it and colder temps. decreasing it.

conscious control of breathing can also occur.

cerebral motor cortex sends impulses to motor neurons, causing stimulation of respiratory muscles, bypassing the medullary centres.

holding the breath is a limited function because the brain stem respiratory centres automatically reinitiate breathing once CO2 levels in the blood become critical.

Question 25

Describe how ageing influences respiration

Answer 25

ageing causes the lungs to lose elasticity, lowering their vital capacity.

the ribs may affect breathing if they become arthritic, and the costal cartilages may become less flexible.

respiratory volume therefore becomes impaired, resulting in the inability to exercise as long or as hard compared with earlier in life.

emphysema risk is much higher in smokers than non-smokers, but some evidence of the disease is present in most people over the age of 50 regardless of their smoking history.

although ageing affects the respiratory system of every adult, smoker will experience greatly increased problems as ageing continues.