Chapter 19 - respiratory system Flashcards
1
Q
Describe the primary functions of the respiratory system
learner Objective
A
The primary functions of the respiratory system are:
the intake of oxygen
and
the removal of carbon dioxide
2
Q
identify the organs of the upper respiratory system and describe their functions
(learner Objective)
A
The upper respiratory system consist of the
A. Nose: allows air to enter and leave via the nostrils.
B. Nasal cavity: helps to warm and moisten air, using mucus to trap particles.
C. Paranasal sinuses: reduce the skulls weight and effect the quality of the voice.
D. Pharynx: carries food from the oral cavity to the oesophagus and allows air to pass from the nasal cavity to the larynx; helps produce the sounds of speech.
3
Q
describe the structure of the airway outside the lungs
learner Objective
A
outside of the lungs, the trachea or windpipe splits into the right and left bronchi.
branched airways leading from the trachea to the alveoli make up the bronchial tree.
these branches begin with the right and left primary bronchi, with each dividing into a secondary bronchus, then into tertiary bronchi, and even finer tubes.
bronchioles are the smaller tubes that continue to divide.
4
Q
describe the functional anatomy of the alveoli.
learner Objective
A
The alveoli are microscopic air sacks inside capillary networks of the lungs.
they provide a large surface of epithelial cells that allow easy exchange of gases.
oxygen defuses from the alveoli into the capillaries, and carbon dioxide defuses from the blood into the alveoli.
5
Q
define and compare the processes of internal and external respiration
(learner Objective)
A
external respiration is defined as gas exchange between air in the lungs and blood.
Internal respiration is defined as gas exchange between blood and cells.
6
Q
Describe the major steps involved in external respiration.
learner Objective
A
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.
During normal inspiration, when inside pressure decreases, atmospheric pressure pushes outside air into the airways.
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. The lungs expand in response, and the thoracic wall moves upward and outward. There is an opposing effect in the alveoli.
7
Q
explain the important structures of the respiratory membrane
learner Objective
A
The respiratory membrane is located in the alveoli.
The inner lining is made up of simple squamous epithelium.
Dense networks of capillaries are found nearby.
At least two thicknesses of epithelial cells and a fused basement membrane layer separate the air in an alveolus form the blood in a capillary.
These layers make up the respiratory membrane; it is here where blood and alveolar air exchange gases.
8
Q
Describe how oxygen is picked up, transported and released in the blood
(learner Objective)
A
As oxygen from the lungs enters the blood, it dissolves in the plasma along with carbon dioxide from the cells or combines with blood components.
About 98% of the oxygen transported by the blood binds the iron containing protein haemoglobin in red blood cells. The remainder dissolves in the plasma.
In the lungs, oxygen dissolves in blood and combines rapidly with the iron atoms of haemoglobin to form oxyhemoglobin.
As the partial pressure of oxygen decreases, oxyhemoglobin molecules release oxygen, diffusing into nearby cells that have depleted their oxygen supplies in cellular respiration. When carbon dioxide increases in the blood, more oxygen is released.
9
Q
Describe the factors that influence the respiration rate
learner Objective
A
Respiration rate is controlled by the respiratory areas of the brain, in the the brainstem: the pons and the medulla oblongata.
The medullar respiratory centre consists of the dorsal and ventral respiratory groups and the respiratory group of the pons.
The dorsal group is important in stimulating the muscles of inspiration.
Increased impulses result in more forceful muscle contractions and deeper breathing.
Decreased impulses result in passive expiration.
The ventral group controls mostly the intercostal and abdominal muscles to increase inspiratory efforts.
Certain chemicals also affect breathing rate and depth, as do emotional states, lung stretching capability, and physical activity.
10
Q
Identify the four distinct respiratory volumes
learner Objective
A
- Tidal Volume: approx. 500ml moved into or out of lungs during respiratory cycle.
- Inspiratory Reserve Volume: Approx. 3,000ml inhaled during forced breathing in addition to tidal volume.
- Expiratory Reserve Volume: Approx. 1,100ml exhaled during forced breathing in addition to tidal volume.
- Residual Volume: Approx. 1,200ml remaining in lungs even after maximal expiration.
11
Q
upper respiratory tract includes
A
Nose
Nasal Cavity
Paranasal Sinuses
Pharynx
12
Q
lower respiratory tract includes
A
Larynx
Trachea
Lungs
13
Q
thyroid cartilage
A
The thyroid cartilage is a hyaline cartilage structure that sits in front of the larynx and above the thyroid gland. The cartilage is composed of two halves, which meet in the middle at a peak called the laryngeal prominence, also called the Adam’s apple.
14
Q
cricoid cartilage
A
is the only complete ring of cartilage around the trachea. It forms the back part of the voice box and functions as an attachment site for muscles, cartilages, and ligaments involved in opening and closing the airway and in producing speech.
15
Q
arytenoid cartilages
A
The arytenoid cartilages are a pair of small three-sided pyramids which form part of the larynx, to which the vocal folds are attached. These allow and aid in the vocal cords’ movement.
16
Q
vocal ligaments
A
The vocal ligaments are two bands enclosed within the vocal folds. They consist of elastic tissue. Anteriorly the vocal ligament is connected to the posterior side of the thyroid cartilage, and posteriorly the vocal ligament is connected to the arytenoid cartilage.
17
Q
inferior nasal concha
A
The inferior nasal concha is one of the three paired nasal conchae in the nose. It extends horizontally along the lateral wall of the nasal cavity and consists of a lamina of spongy bone, curled upon itself like a scroll,. The inferior nasal conchae are considered a pair of facial bones. As the air passes through the turbinates, the air is churned against these mucosa-lined bones in order to receive warmth, moisture and cleansing. Superior to inferior nasal concha are the middle nasal concha and superior nasal concha which arise from the cranial portion of the skull. Hence, these two are considered as a part of the cranial bones.
18
Q
Tracheal cartilages
A
In the trachea, or windpipe, there are tracheal rings, also known as tracheal cartilages. Cartilage is strong but flexible tissue. The tracheal cartilages help support the trachea while still allowing it to move and flex during breathing. There are generally sixteen to twenty individual cartilages in the trachea
19
Q
soft palate
A
The soft palate is, in mammals, the soft tissue constituting the back of the roof of the mouth. The soft palate is part of the palate of the mouth; the other part is the hard palate. The soft palate is distinguished from the hard palate at the front of the mouth in that it does not contain bone.
20
Q
the c-shaped rings of the trachea
A
made of cartilage
allow the oesophagus to expand slightly into the tracheal space.
keep the trachea open for passage of air
21
Q
total lung capacity of an adult
A
approx. 6 litres
22
Q
location of pnuemotaxic and apnuestic centres
A
Pons
23
Q
How is the basic rhythm of quiet respiration set?
A
by pacemaker cells in the diaphragm; by the pneumotaxic area of the pons; by the apneustic area of the pons; by the inspiratory area of the medulla oblongata; by the expiratory area of the medulla oblongata;
24
Q
nasal cavity is divided by
A
The nasal septum divides the cavity into two fossae.
Each fossa is the continuation of one of the two nostrils.
25
hilum
a depression or pit at the part of an organ where vessels and nerves enter.
Each lungs mediastinal surface has an indentation known as the Hilum.
Pulmonary and systemic blood vessels and bronchi, lymphatic vessels, and nerves enter and leave the loan at this point.
26
Lingual tonsils.
The lingual tonsils are two small mounds of lymphatic tissue located at the back of the base of the tongue, one on either side. They are composed of lymphatic tissue that functions to assist the immune system in the production of antibodies in response to invading pathogenic bacteria or viruses
27
Surfactant
surfactant is produced by the alveolar cells in the lungs and line mainly the alveoli and small bronchioles, and prevents the alveoli from collapsing. Lung surfactant makes it easier for oxygen to penetrate the lung surface lining and move into the blood.
28
Glottis
the space between one of the true vocal cords and the arytenoid cartilage on one side of the larynx and those of the other side
29
epiglottis
The epiglottis is a leaf-shaped flap of cartilage located behind the tongue, at the top of the larynx, or voice box. The main function of the epiglottis is to seal off the windpipe during eating, so that food is not accidentally inhaled. The epiglottis also helps with some aspects of sound production in certain languages.
30
The cough center location
The cough center of the brain is a region of the brain which controls coughing, located in the medulla oblongata area of the brain.
31
how many pieces of hyaline cartilage in trachea
20 c shaped pieces
32
carina
a cartilage structure called the carina projects posteriorly from the final tracheal cartilage.
This is the point where the trachea branches into the two primary bronchi.
33
bronchial tree
branched airways leading from the trachea to the alveoli make up the bronchial tree.
right and left primary bronchi. near the level of the fifth thoracic vertebrae.
each primary bronchus divides into secondary bronchus
then tertiary bronchi
and even finer tubes
The right bronchi aka bronchus dexter is wider, shorter and more vertical then the left bronchus aka bronchus sinister.
34
The right Bronchus AKA
bronchus dexter
is wider, shorter and more vertical
branches off to the upper lobe of the right lung. This branch is called the eparterial branch.
it then divides into two branches for the middle and lower lobes.
divides into secondary or lobar bronchi, with three on the right. each supplying a single lobe.
then divide into tertiary bronchi or segmental bronchi.
35
The left bronchus AKA
bronchus sinister
has no eparterial branch because there is no third lobe in the left lung
divides into secondary or lobar bronchi, with two on the left. each supplying a single lobe.
then divide into tertiary bronchi or segmental bronchi.
36
Bronchioles
smaller tubes that continue to divide and include terminal bronchioles, respiratory bronchioles and thin alveolar ducts.
The ducts lead to outpouchings called alveolar sacs, which lead to microscopic alveoli inside capillary networks.
The term bronchioles refers to bronchial passages that are smaller than 1 mm in diameter. The smallest are called terminal bronchioles, which are less than 0.5 mm in diameter.
37
cartilage and muscle of airways
bronchi have less cartilage then the trachea
bronchioles have no cartilage.
smaller and smaller respiratory tubes have smooth muscle instead of cartilage.
38
Alveoli
The alveoli provide a large surface of epithelial cells that allow easy exchange of gases.
Oxygen diffuses from the alveoli into the capillaries.
Carbon dioxide diffuses from the blood into the alveoli.
The alveoli are not the same as the alveolar sacs. The alveoli are the actual sides of gas exchange.
There are approximately 300 million alveoli in the lungs, all of them filled with gas. They make up most of the body's long volume, creating a huge surface area for gas exchange.
39
conducting zone structures
include all respiratory passageways except those that make up the respiratory zone.
The conducting zone structures are relatively bridges and the organs with in function to clean, humidify and warm the incoming air.
Therefore, when this air reaches the lungs, it contains less dust, bacteria, and other irritants then when it entered the nose and has become warm and damp.
trachea splits to primary bronchi, found at T7 when a person is standing. They move downward into the hilum, or medial depression, of the lungs.
40
Respiratory zone structures
The respiratory zone is where actual gas exchange occurs.
It's made up of microscopic structures: respiratory bronchioles, alveoli ducts, and alveoli.
The respiratory zone starts at the point of the terminal bronchioles feeding into the respiratory bronchioles inside the lungs.
Scattered alveoli protrude from the respiratory bronchioles which also lead into twisting and turning alveolar ducts.
The walls of the alveolar ducts are completely made up of diffuse rings of connective-tissue fibres, alveoli and smooth muscle cells.
The ducts lead to alveolar sacs or alveolar saccules, which are terminal clusters of alveoli.
41
alveolar sacs
The alveolar sacs resemble bunches of grapes.
with the alveoli being the individual grape-like structures.
42
alveolus
In each alveolus the walls are mostly made up of one layer of squamous epithelium cells, also called type one alveolar cells.
These are surrounded by a thin respiratory basement membrane. There are also scattered, cuboidal Type II alveolar cells. These secrete surfactant, which case the alveoli surfaces that are exposed to gas. The Type II cells also secrete many antimicrobial proteins comma needed for innate immunity.
43
lung apex
Just below the clavicle bone on each side is the lungs narrow superior tip or apex
44
base of lung
The base of the lung is the concave inferior surface that rests on the diaphragm muscle
45
elastic rebound
The action of the diaphragm and rib cage returning to their normal positions is called elastic rebound.
Most of the lungs contain airspaces, with the remainder, called the stroma, which is primarily an elastic connective tissue.
This makes the lungs very soft, spongy and light.
They collectively weigh slightly more than 1 kg.
46
two types of lung circulation
| upto pg 452 - delete this bracketed note
pulmonary and bronchial.
pulmonary: the pulmonary arteries deliver systemic venous blood that is deoxygenated, these arteries are located anterior to the main Bronchi. highly branched eventually bringing blood to the pulmonary capillary networks that surround the alveoli. Freshly oxygenated blood from the respiratory zone is brought by the pulmonary veins from the lungs to the heart. These veins flow to the hilum with corresponding bronchi as well as in the connective-tissue septa between the bronchopulmonary structures.
When a pulmonary arteries blocked by any type of embolus, including clots, air bubbles, or fat masses, a pulmonary embolism occurs. This can cause alveolar collapse, researchers failure, congestive heart failure and death.
47
what innervates the lungs
sympathetic and parasympathetic motor fibres along with visceral sensory fibres.
the visceral sensory fibres enter the lungs through the pulmonary plexus, which is located at the root of each lung, and runs along the bronchial tubes and lung blood vessels.
48
parasympathetic motor fibres effect on lungs
the parasympathetic motor fibres constrict the air tubes, known as broncho-constriction
excessive parasympathetic stimulation, which occurs in asthma, may also totally prevent airflow along terminal bronchioles.
49
sympathetic motor fibres effect on lungs
the sympathetic motor fibres dilate air tubes, know as broncho-dilation
50
how often does all the blood in the body pass through the lungs
once a minute.
Therefore, the endothelium of lung capillaries is a perfect place for enzymes that affect materials in the blood.
These enzymes include angiotensin-converting enzyme, which activates a vital blood pressure hormone, and enzymes that inactivate various prostaglandins.
51
structures of the respiratory system: Nose
centered above the mouth and inside and below the space of the eyes.
contains the nostrils, which provide entrances to the nasal cavity.
52
structures of the respiratory system: Nasal Cavity
Hollow space behind the nose.
Transports air to the pharynx.
filters, warms, and moistens air.
53
structures of the respiratory system: Oral Cavity
The mouth cavity, containing the teeth, tongue, salivary glands, etc.
Allows passage of air and food.
Transports air to the pharynx and warms and moistens it.
Aids in the production of vocal sounds.
54
structures of the respiratory system: Paranasal Sinuses
Hollow spaces in certain skull bones.
Serve as resonant chambers.
Also help to reduce the weight of the skull.
55
structures of the respiratory system: Pharynx
a chamber located behind the nasal cavity, oral cavity, and larynx. Also known as the throat.
Transports air to the larnyx.
56
structures of the respiratory system: Epiglottis
Flap like cartilaginous structure at the back of the tongue, near the entrance to the trachea.
Covers the opening to the trachea when swallowing occurs.
57
structures of the respiratory system: Larynx
Enlargement at the top of trachea. Commonly known as the voice box. Houses the vocal cords.
Produces sound.
Transports air to the trachea.
Helps to filter, warm, and moisten incoming air.
58
structures of the respiratory system: Trachea
Tubular structure in the neck through which passes.
Warms, filters, and moistens air.
Transport air into the lungs.
59
structures of the respiratory system: Bronchial Tree (including Bronchi and Bronchioles)
Tubes that branch out outward, connecting the trachea to the alveoli.
Conduct air from trachea to alveoli, with a mucus lining that filters incoming air.
60
structures of the respiratory system: Lungs
Pair of organs in the chest responsible for providing oxygen to the blood and for exhaling carbon dioxide waste.
Contains air passages, alveoli (the area where oxygen and carbon dioxide exchange occurs), blood vessels, connective tissues, lymphatic vessels, and nerves of the lower respiratory tract.
61
Breathing is also known as...
Pulmonary ventilation or respiration.
62
ventilation
The movement of air from outside of the body into and out of the bronchial tree and alveoli.
63
mechanics of breathing: inhalation
AKA inspiration
During normal inspiration, when inside pressure decreases, atmospheric pressure pushes outside air into the airways.
Phrenic nerve impulses stimulate the diaphragm to contract, moving downward.
The thoracic cavity then enlarges, internal pressure falls, and atmospheric pressure forces air into the airways.
As the diaphragm contracts, the external or inspiratory intercostal muscles between the ribs are stimulated to contract.
The ribs raise and the sternum elevates, enlarging enlarging the thoracic cavity further.
The lungs expand in response to these movements as well as those of the pleural membranes.
When the external intercostal muscles move the thoracic wall upward and outward, the parietal pleura also moves, as does the visecral pleura.
The lungs then expand in all directions.
64
mechanics of breathing: Alveoli
The attraction of water molecules creates surface tension that makes it difficult for the alveoli to inflate.
A mixture of lipids and proteins known as surfactant, reduces the tendency of the alveoli to collapse and eases inflation of the alveoli.
65
mechanics of breathing: exhalation
AKA expiration
Expiration occurs because of the elastic recoil of tissues and surface tension.
As the diaphragm lowers, it compresses the abdominal organs below it. The elastic tissues cause the lungs and thoracic cage to return to their original shapes, and the abdominal organs move back into their previous shapes to push the diaphragm upward.
Surface tension decreases the diameters of the alveoli, increasing alveolar air pressure.
Air inside the lungs is forced out, meaning that normal resting expiration is a passive process.
Even more forceful exhalation is required, the posterior internal or expiatory intercostal muscles contract.
This is pulls the ribs and sternum downward and inward to increase the pressure in the lungs.
The abdominal wall muscles squeeze on the abdominal organs inward, forcing the diaphragm even higher against the lungs.
66
Atmospheric pressure
760 mm hg at sea level.
Also expressed in atmospheric units. 760 mm Hg = 1 Atmospheric unit.
67
respiratory pressure
a zero respiratory pressure is equal to atmospheric pressure (760 mm Hg).
A positive respiratory pressure is higher than atmospheric pressure.
68
Intrapulmonary pressure
AKA intra-alveolar pressure.
abbreviated as 'P pul'
The pressure inside of the alveoli
Intrapulmonary pressure increases and decreases during normal breathing but always becomes equalised with atmospheric pressure and eventually.
69
intrapleural pressure
The pressure inside the plural cavity.
abbreviated as 'P ip'
Increases and decreases during normal breathing. However, intrapleural pressure is always approximately 4 mm Hg lower then intrapulmonary pressure.
It is therefore described as always negative to the intrapulmonary pressure.
To have a negative intrapleural pressure, the amount of pleural fluid in the pleural cavity needs to remain as little as possible. On a continuous basis, pleural fluid is pumped out of the pleural cavity, entering the lymphatics. Otherwise, it would accumulate in the intrapleural space and provide a positive pressure in the plural cavity.
If a condition equalises intrapleural pressure with either intrapulmonary or atmospheric pressure, immediate Lung collapse occurs.
70
The difference between the intrapulmonary and intrapleural pressures is called?
The transpulmonary pressure.
This pressure keeps the air spaces in the lungs open, keeping them from collapsing.
71
Pulmonary ventilation
Pulmonary ventilation is a mechanical process that consists of inspiration and expiration.
It is based on volume changes in the thoracic cavity.
Volume changes always lead to pressure changes
Pressure changes lead to flow of gases, to equalise pressure.
72
boyle's law
States that at a consistent temperature, the pressure of gas changes inversely with its volume.
Gases always fill their containers, so the size of a container influences the space between Gas molecules. A larger container will cause gas molecules to be further apart and, therefore, pressure to be lower. Reducing container volume brings the gas molecules closer and increases the pressure. This is a simple way to understand how gases work inside our lungs.
73
Airway Resistance
Friction is the primary non-elastic source of resistance to gas flow.
Also referred to as drag. It occurs in the respiratory passageways.
Gas flow is related to pressure and resistance. Equivalent factors determine gas flow in the respiratory system and blood flow in the cardiovascular system.
Usually tiny differences in pressure produce significant changes in gas low-volume.
During normal, quiet breathing, the average pressure gradient is 2 mm Hg or less. This small amount is able to move 500 mL of air, with each breath, in and out of the lungs.
74
Alveolar Surface Tension
Surface tension is a state of tension at a liquids surface that is produced by unequal attraction.
Surfactant is a mix of lipids and proteins that resembles detergent in its effects. It is produced by Type II alveolar cells.
Surfactant makes water molecules become less cohesive. This reduces the surface tension of the alveolar fluid. As a result, lower amounts of energy are needed to expand the lungs and keep the alveoli from collapsing. Type II alveolar cells are stimulated to secrete more surfactant by breaths that are deeper than normal.
75
Respiratory volumes
There are four distinct respiratory volumes that can be measured by using spirometry, which is also known as pulmonary function testing. Spirometry is used to measure the functional capacity of the lungs.
Tidal Volume/Quite breathing = 500ml
Inspiratory reserve volume = 3,100ml
Expiratory reserve volume = 1,200ml.
Residual volume = 1,200ml
76
Tidal Volume
500ml for men and women.
Under resting conditions, the air inhaled or ex-hailed with each breath
77
inspiratory reserve volume
3,100ml man
1,900ml women
Air that can be forcibly inhaled after normal tidal volume inspiration
78
expiratory reserve volume
1,200ml man
700ml woman
Air that can be forcibly exhaled after normal tidal volume expiration
79
Residual volume
1,200ml man
1,100ml woman
Air remaining in lungs after forced expiration
80
Respiratory capacities
Respiratory capacities include inspiratory, functional residual, vital, and total lung capacities.
Two or more lung volumes always make up the respiratory capacities.
Females have smaller bodies and lung volumes then adult males do.
81
Total lung capacity
6,000ml man
4,200ml woman
Maximum air contained in lungs after maximum inspiratory effort.
The total of all lung volumes added together.
82
Vital capacity
4,800ml man
3,100ml woman
Maximum air that can be expired after maximum inspiratory effort.
Total volume + inspiratory reserve volume + expiratory reserve volume
83
Inspiratory capacity
3,600ml man
2,400ml woman
Maximum air that can be inspired after normal tidal volume expiration.
tidal volume + inspiratory reserve volume
84
Functional residual capacity
2,400ml man
1,400ml woman
Air remaining in lungs after normal tidal volume expiration
expiratory reserve volume + residual volume
85
dead space
A certain amount of inspired air does not contribute alveolar gas exchange, but fills the conducting respiratory passageways.
Anatomic dead space is made up of the volume of these conducting conduits.
That dead space is approximately 150 mL.
Four example, only 350 mL of air are used in alveolar ventilation, out of a tidal volume of 500 mL.
In the conditions of alveoli collapse all mucous obstruction, gas exchange may stop. Then, the alveolar dead space is added to the anatomic dead space, comprising a volume that is not used, known as the total dead space.
86
minute ventilation
The total amount of gas flowing into or out of the respiratory tract, in one minute, is called the minute ventilation.
In a healthy individual during normal, quiet breathing, this is approximately 500 mL per breath.
At 12 breaths per minute, this is about 6 L of air.
The minute ventilation may increase to 200 L per minute during vigourous exercise.
87
Alveolar Ventilation Rate
It measures the flow of gases into and out of the alveoli during a certain interval of time. The alveolar ventilation rate is calculated by multiplying the frequency of breaths per minute by the tidal volume minus the debt space.
The alveolar ventilation rate it is based on millimetres of per minute.
88
respiratory membrane
The membrane separating air within the alveoli from the blood within pulmonary capillaries. It consists of the alveolar wall, the capillary wall, and their basement membranes.
alveolar wall and capillary walls are simple squamous epithelium
89
O2, Co2 and N2 content in air
78% N2
21% O2
0.04% Co2
90
partial pressure
The amount of pressure each gas contributes to air pressure is called the partial pressure of that gas.
e.g O2 is 21% of air so its 21% of atmospheric pressure (760 mm Hg) which means partial pressure of O2 in air is 160 mm Hg.
Partial pressure of oxygen is symbolised as P02 and the partial pressure of carbon dioxide is symbolised as Pc02
91
Gas exchange
Air exchanges across the respiratory membrane occur by diffusion
92
Daltons law
Dalton's law states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases.
93
Henry’s law
States that when gas contacts a liquid, it dissolves
94
Gas solubility
The solubility of a gas in a liquid, along with the liquids temperature, determines how much of the gas will dissolve in the liquid at a specific partial pressure.
From the air, carbon dioxide and other gases have various solubilities in water or in blood plasma. Carbon dioxide has the highest solubility, with oxygen only one 1/20th as soluble. Nitrogen is only half as soluble is this.
Therefore, at a certain partial pressure, nearly no nitrogen will dissolve in water, but there is twice as much oxygen that will dissolve and 20 times more carbon dioxide.
Gas solubility decreases as the temperature of a liquid increases. For example, soda loses the carbon dioxide that it contains more rapidly at room temperature then it does in a refrigerator.
95
Alveolar gas movement
The alveoli contain more carbon dioxide and water vapour, and much less oxygen than the atmosphere, which also has abundant amounts of nitrogen.
In the lungs, gas exchanges include the diffusion of oxygen from the alveoli into the pulmonary blood and the diffusion of carbon dioxide in the opposite direction.
The conducting passages humidify the air inside them.
Alveolar gas is really a mixture of new, inspired gases with those that remain in the respiratory passages between breaths.
Increasing the depth and rate of breathing easily changes the alveolar partial pressures of oxygen and carbon dioxide.
A high alveolar ventilation rate brings in more oxygen, and the alveolar partial pressure of oxygen therefore increases. Also, carbon dioxide is rapidly eliminated from the lungs.
96
External respiration
Also referred to as pulmonary gas exchange.
The blood in the pulmonary circulation is dark red in colour.
When its returned to the heart and oxygenated for distribution to the body tissues, it becomes scarlet, which is much brighter red. This is because of the uptake of oxygen to haemoglobin in the red blood cells.
The unloading or exchange of carbon dioxide also occurs at the same time, with the same speed.
97
External respiration is influenced by three factors
1. The respiratory membranes surface area.
2. Gas solubilities and partial pressure gradients.
3. The fact that alveolar ventilation is matched with pulmonary blood perfusion by ventilation-perfusion coupling.
In a normal lung, gas exchange is extremely efficient, and the respiratory membrane is thin, only between 0.5 and 1um
98
Internal respiration
In internal respiration, gas is exchanged between the capillaries and body tissues.
Diffusion gradients and partial pressure are reversed from those in external respiration and pulmonary gases exchange.
The ways in which gas exchanges occur between the systemic capillaries and the body tissues are nearly the same, however, as those occurring in the lungs.
In cells, Co2 is produced while O2 is used for metabolic processes. The partial pressure of oxygen is always lower in the tissues at 40 mmHg than systemic blood, which is 100 mm Hg. This means O2 quickly moves from blood to tissues up to the point equilibrium is reached.
Simultaneously Co2 is quickly moved along its pressure gradient into the blood.
In both internal and external respiration gas exchanges by simple diffusion. Influenced by partial pressure gradients on either side of the exchange membranes.
99
Air exchanges across the respiratory membrane occur by the?
Diffusion process
Each gas defuses between areas of higher partial pressure and areas of lower partial pressure, until the two areas reach equilibrium.
100
Internal respiration
In internal respiration gas is exchanged between the capillaries and body tissues.
Diffusion gradients and partial pressure are reversed from those in external respiration and pulmonary gas exchange.
The ways in which gas exchanges occur between the systemic capillaries and the body tissues are nearly the same, however, as those occurring in the lungs.
In the body tissue cells carbon dioxide is produced while oxygen is continuously used for metabolic processes.
Partial pressure of oxygen is always lower in the tissues at 40 mm Hg, then in systemic blood, in which it is 100 mm Hg.
Oxygen moves quickly into the tissues from the blood.
Carbon dioxide moves quickly along its partial pressure gradient out of tissues into the blood.
Gas exchange is occurring between the blood and alveoli and between the blood and body tissue cells occur via simple diffusion.
101
Oxygen transport
Oxygen and carbon dioxide enter into the blood by dissolving in the plasma or combining with blood components.
98% of the oxygen transported by the blood binds the iron containing protein haemoglobin in red blood cells. The remainder dissolves in the plasma.
In the lungs, oxygen dissolves in blood and combines rapidly with the iron atoms of haemoglobin to form oxyhaemoglobin, whose bonds are unstable.
As P02 decreases, Oxyhaemoglobin molecules release oxygen, diffusing into nearby cells that have depleted their oxygen supplies in cellular respiration.
102
Haemoglobin that has released oxygen is referred to as?
Reduced haemoglobin or deoxyhemoglobin
103
Loading and unloading of haemoglobin
The haemoglobin molecule changes shape after the first oxygen molecule binds to iron. Then, it takes up 2 more oxygen molecules more easily, with uptake of the fourth molecule still easier. A haemoglobin molecule is partially saturated when1 to 3 oxygen molecules are bound. It is fully saturated when all four of its haem groups are bound to oxygen.
Unloading of a single oxygen molecule enhances unloading of the next molecule and then the next, meaning unloading and loading are functionally similar although opposite processes.
The binding strength, or affinity, of haemoglobin for oxygen is altered based on how much oxygen saturation exists.
The partial pressure of oxygen, blood pH, temperature, the partial pressure of carbon dioxide, and blood concentrations of two, 3-bisphosphoglycerate all regulate the rate of haemoglobin reversibly binding or releasing oxygen.
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Effects of blood acidity increase or temperature rise
Carbon dioxide increases in the blood, causing more release of oxygen. Therefore, during physical exercise, more oxygen is released to skeletal muscles. This increases carbon dioxide concentration, D creases PH, and raises temperature.
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Carbon dioxide transport
Blood transports carbon dioxide to the lungs either:
As carbon dioxide dissolved in plasma, in quantities of 7% to 10%.
As part of a compound formed by bonding to haemoglobin, which is slightly more than 20%.
As bicarbonate ions, which is approximately 70%.
Approximately 200 mL of carbon dioxide are produced by active body cells every minute. This is exactly the same amount that
is excreted by the lungs.
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Carbon dioxide transported on haemoglobin
Carbon dioxide differs from oxygen in that it bonds with the amino groups of the “globin” or protein portion of these molecules.
Oxygen and carbon dioxide do not compete for binding sites.
Haemoglobin can transport both molecules at the same time. Carbon dioxide loosely bonds with haemoglobin to slowly form carbaminohaemoglobin, which decomposes readily in regions of low carbon dioxide partial pressure.
C02 + Hb HbC02 (carbaminohaemoglobin)
Hb is haemoglobin
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C02 transport: Bicarbonate ions
The most important carbon dioxide transport mechanism forms bicarbonate ions.
Carbon dioxide reacts with water to form carbonic acid.
Most carbon dioxide molecules that enter the plasma quickly enter the red blood cells. It is unstable, disassociating into hydrogen and bicarbonate ions.
In red blood cells, the enzyme carbonic anhydrase speeds up the reaction of carbon dioxide and water, resulting in carbonic acid that releases hydrogen and bicarbonate ions.
Nearly 70% of carbon dioxide is transported by the blood is in this form.
Haemoglobin acts as a buffer, freed hydrogen ions do not cause a significant change in pH under resting conditions.
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Control of breathing
Respiratory control has both involuntary and voluntary components.
The involuntary centres of the brain regulate the inspiratory muscles. They control respiratory minute volume by adjusting the depth and frequency of pulmonary ventilation.
This occurs in response to sensory information that arrives from the lungs, various portions of the respiratory tract, and a variety of other sites.
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The respiratory areas of the brain
They control inspiration as well as exhalation.
The voluntary control of respiration reflects activity in the cerebral cortex that affects either the output of the respiratory centre in the Medela oblongata and pons OR the output of motor neurons in the spinal-cord that controls the respiratory muscles.
The most important parts comprise the medullary respiratory centre, which consists of the dorsal and ventral respiratory groups and the respiratory group of the pons.
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The dorsal respiratory group
Located near the root of the cranial nerve IX
It is important in stimulating the muscles of inspiration
Increased impulses result in more forceful muscle contractions and deeper breathing. Decreased impulses result in passive expiration.
It integrates input from chemoreceptors and peripheral stretch receptors.
It communicates this information to the ventral respiratory group.
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The ventral respiratory group
Controls other respiratory muscles, mostly the intercostals and abdominals, to increase the force of expiration and sometimes to increase inspiratory efforts.
It is believed to be a centre of integration and generation of rhythm.
It is a network of neurons extending from the spinal-cord, through the ventral brainstem, to the pons-medulla junction.
Some neurons fire during inspiration, where as others fire during expiration.
The inspiratory neurons, send impulses along the phrenic and intercostal nerves, exciting the diaphragm and external intercostal muscles, respectively.
Therefore, damage to the phrenic nerves can increase respiratory rate.
In severe hypoxia the ventral respiratory group causes the individual to gasp for air. This may be a final effort to restore oxygen to the brain.
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Inspiratory and expiratory cycling
Is continuous, producing the normal respiratory rate of 12 to 15 breaths per minute.
Eupnea is the term describing this normal respiratory rate and rhythm.
When certain clustered neurons are completely suppressed, respiration stops. Causes of this include overdoses of alcohol or drugs such as morphine.
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Pontine respiratory group
In the pons.
The basic rhythm of breathing may also be controlled by the pontine respiratory group.
This consists of several centres influencing and modifying medullary neuron activities.
The pontine group is believed to make the transitions between inspiration and expiration and the reverse, smoother processes. Lesions to the superior region of the pontine respiratory group causes prolonged inspirations to occur, which is called apneustic breathing.
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The rhythmic quality of breathing
It’s not fully understood but the most accepted theory is that normal respiratory rhythm is based on reciprocal inhibition of interconnected networks of neurons in the medulla.
Instead of one set of “pacemaker neurons”, two sets of neurons inhibit each other. Their activity occurs in cycles, and this generates respiratory rythm.
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Factors of respiratory rate and depth: depth
The level of activity of the respiratory centre and its stimulation of motor neurons that serve the respiratory muscles affect depth of inspiration. With more stimulation, increased numbers of motor units are excited. Causing respiratory muscles to contract with greater force.
Deep breathing is referred to as diaphragmatic breathing, while shallow breathing is known as costal breathing.
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Factors of respiratory rate and depth: rate
Respiratory rate is established by the length of time the inspiratory centre is active or how fast it is turned off.
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Factors of respiratory rate and depth: chemicals
Important substances include: carbon dioxide, hydrogen and oxygen ions in the arterial blood.
Central chemoreceptors: located in the medulla oblongata, sense carbon dioxide and hydrogen ion changes in the cerebrospinal fluid. When these levels change, respiratory rate and tidal volume are signalled to increase.
More carbon dioxide is exhaled, and both blood and cerebrospinal fluid levels of these chemicals fall, decreasing breathing rate.
Carbon dioxide is the most important chemical regulator of respiration.
If breathing stops even for a short time blood levels of carbon dioxside and hydrogen ions rise and oxygen levels fall. Chemo receptors are stimulated, and the urge to inhale increases, overcoming the lack of oxygen.
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Factors of respiratory rate and depth: other factors
Other factors include: emotional states, lung stretching capability and levels of physical activity.
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Factors of respiratory rate and depth: the deflation reflex
Usually only functions during forced exhalation and inhibits the expiratory centres while stimulating the inspiratory centres when the lungs are deflating.
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Factors of respiratory rate and depth: how partial pressure of oxygen influences breathing
The peripheral chemoreceptors contain cells that are sensitive to arterial levels of oxygen.
These chemo receptors lie in the aortic bodies of the aortic arch and the carotid bodies at the bifurcation of the common carotid arteries.
Normally, reducing partial pressure of oxygen only affect ventilation minimally.
For oxygen levels to become a strong stimulus for increased ventilation, arterial partial pressure of oxygen must drop greatly, to at least 60 MM Hg
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Factors of respiratory rate and depth: how arterial PH influences breathing
Increased ventilation occurring because of reduced arterial pH is controlled via the peripheral chemoreceptors.
Reduced blood pH may be related to retention of carbon dioxide.
It may also occur because of metabolic reasons.
These include lactic acid accumulation because of exercise or fatty acid metabolite or ketone body accumulation because of uncontrolled diabetes mellitus.
As arterial pH declines, the respiratory system will attempt to compensate and raise the pH. This occurs by the increase of respiratory rate and depth in an attempt to eliminate carbon dioxide and carbonic acid in the blood.
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Factors of respiratory rate: how higher brain centres influence breathing
Respiratory rate and depth are modified when pain or strong emotions send signals to the respiratory centres.
This occurs via the limbic system, including the hypothalamus.
Changes in body temperature also affect respiration, with hotter temperatures increasing it and colder temperatures decreasing it.
Conscious control of breathing can also occur. The cerebral motor cortex sends impulses to the motor neurons, causing stimulation of respiratory muscles. This bypass is the medullary centres.
Holding the breath is a limited function because the brain stem respiratory centres automatically reinitiate breathing once carbon dioxide levels in the blood become critical.
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Effects of ageing on the respiratory system
Ageing causes the lungs to lose elasticity, lowering their vital capacity. The ribs play a role in affecting breathing because they may become arthritic, and the costal cartilages may become less flexible. Respiratory volume is therefore impaired, resulting in the inability to exercise as long or as hard compared with earlier in life.
Emphysema risk is much higher in smokers then in non-smokers, but some evidence of the disease is present in most people over age 50 regardless of their history of smoking.
