Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
The two systems that supplied O2 and eliminated CO2 are the cardiovascular system and respiratory system.
The respiratory system consists of a set of passageways that carry gases to and from the respiratory membranes, which gases diffuse between the lungs and the blood.
The r.s consist of organs that exchange gases between atmosphere and blood .These organs are 1-nose 2-pharynx 3-larynx 4-trachea 5-bronchi 6- lungs.
The upper, r.s consist of nose, pharynx and larynx.
The lower r.s consist of trachea, bronchi and Lungs.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Respiration: is the overall exchange of gases between the atmosphere, blood and cells.
There are three basic processes involved in respiration:-
1-pulmonary ventilation (breathing): is the inspiration (in flow) and expiration (out flow) of air between the atmosphere and the lung.
2-External respiration: is the exchange of gases between the lungs and the blood.
3-Internal respiration: is the exchange of gases between the blood and the cells.
A) Nose consist of - 1-External nares 2-Nasal cavity 3-Nasal septum
4-conchae 5-Internal nares.
*Nasal cavity in the internal position contain vestibule
*The conchae contain the olfactory receptors.
*Functions of the structure, of the nose are:-
1-incoming air is wormed, humidified and filtered 2-olfactory stimuli is received 3-large hollow resonating chambers are provided for speech sound.
B) Pharynx (throat): Is a muscular tube lined by mucous membrane and divided into:-
1-nasopharynx:-functions in respiration
2-oropharynx:-functions in digestion and respiration.
3-laryngopharynx: - functions in digestion and respiration. 2
Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Functions are:
1-serves a passageway for air and food
2-provide a resonating chamber for speech sounds
C) Larynx (voice box): It is a short passageway that connects the pharynx with the trachea.
The larynx contain:
The cartilages are either hyaline or elastic in nature.
These are Hyaline cartilages – Thyroid (unpaired) – Cricoid (unpaired) – Arytenoid (paired)
Elastic cartilages – Epiglottis (unpaired) – Cuneiform (paired) – Corniculate (paired)
1-cartilages (nine in number).
a) Thyroid cartilage (Adams apple).
b) The epiglottis which prevents food from entering the larynx.
C) The cricoid cartilage which connects the larynx and trachea.
d) Paired arytenoid cartilages.
e) Paired corniculate cartilage.
f) Paired cuneiform cartilage.
2-vocal folds (vocal cords) which produce sounds a) Taut folds produce high pitches
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji b) Loose folds produce low pitches
*The larynx is lined with ciliated columnar cells, goblet cells, and basal cells and provide some protection against dust.
D) Trachea: It is a tubular passageway for air extends from the larynx to the primary bronchi. It is composed of smooth muscle and C-shaped ring of hyaline cartilage and is lined with pseudo-stratified epithelium.
Functions:
1-protection against dust
2-the C-shaped cartilage provide a rigid support to prevent tracheal collapse inward and then prevent obstruction of air passageway.
3- The presence of the smooth muscle and elastic C.T in the trachea allow it to dilate and constrict the air passageway according to the physiological state.
*Carina: is an internal ridge in the bifurcation of trachea into left and right bronchi, formed by the projection of the last tracheal cartilage. The mucous membrane of the Carina is one of the most sensitive areas of the respiratory system and is associated with the cough reflex.
E) Bronchi
The trachea terminates in the chest by dividing at the sternal angle into:-
1-right primary bronchus which goes to the right lung.
2-left primary bronchus goes to the left lung.
The bronchi (like trachea) contain incomplete ring of cartilages and are lined by pseudostratified ciliated epithelium.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
On entering the lungs, the primary bronchi divides as follows:
Primary bronchus→ secondary bronchi (one for each lobe of the lung (the right lung has 3 lobes and the left has 2 lobes in human and 3 in animals) → tertiary (segmental) bronchi→ that divided into bronchioles →terminal bronchioles→ resp. bronchioles→ alveolar ducts →alveolar sacs +alveoli
*This continuous branching from trachea to form a tree trunk with it is branches called the bronchial tree.
As the branching becomes more extensive in the bronchial tree, several Structural changes noted:-
1-rings of cartilages are replaced by plates of cartilage that finally disappear in the bronchioles.
2-as the cartilages decreases, the amount of smooth muscle increases.
3- The epithelium changes from pseudostratified ciliated to simple cuboidal in the terminal bronchioles.
F) Lungs
The lungs are paired cone- shaped organs lying in the thoracic cavity.
They enclosed and protected by two layers of serous membrane. Called Pleural membrane. Pleural membrane is consists of:-
1-parietal pleura:-the outer layer which attached to the wall of the thoracic cavity.
2- Visceral pleura:-the inner layer which cover the lungs.
Between the visceral and parietal pleura is the pleural cavity which contains a lubricating fluid secreted by the membranes. This fluid prevent frictions
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji between the membranes and allows them to move easily on one another during breathing.
# Alveolar-capillary membrane (Resp. membrane) it is the membrane across it the exchange of resp. gases between the lungs and blood takes place by diffusion.
This membrane is consist of:-
1-Alvoelar wall a layer of squamous epithelium cells with septal cells and free alveolar macrophages.
2-An epithelial basement membrane under the alveolar wall.
3- A capillary basement membrane that is often fused to the epith. basement membrane.
4-The endothelial cells of the capillary.
*septal cells function in producing a phospholipid substance called surfactant which lowers surface tension.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
*Alveolar macrophages (dust cells) are highly phagocytic cells that remove dust particles or other debris from alveolar spaces.
*The functional structures of the lung is the alveoli plus the alveolar sac. over the alveoli the arterioles and venules disperse into a capillary network.
Blood supply
There are double blood supply to the lungs.
1-Deoxygenated blood: - pulm. Artery →left and right pulm. arteries
4-pulm.veins (2from each lung)→L. atrium
2-Oxygenated blood:-aorta→ bronchial arteries→ bronchial veins →communicate with the pulm .veins→ left atrium
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Physiology of respiration
1-pulmonary ventilation
It is the process by which gases are exchanged between atmosphere and lung alveoli.
Air flows between the atmosphere and lung a long with pressure gradient. Air moves into the lungs when the pressure inside the lungs is less than the air pressure in the atmosphere inspiration and air moves out of the lungs when the pressure inside the lungs is greater than the pressure in atmosphere (expiration).
A) Inspiration (inhalation)
*The pressure of a gas in closed container is inversely proportional to the volume of the container.
↑ Size of the container→ ↓ pressure inside the container.
↓Size of the container→ ↑ pressure inside the container.
This is the Boyles law.
*In order for inspiration to occur, the lungs must be expanded. This increase lung volume and thus decreases the pressure in the lung bellow than the atmosphere pressure this differences in pressure force air into the lungs during inhalation
The first step toward increasing lung volume involves contraction of the inspiratory muscle (the diaphragm and external intercostal muscle).
1-Contraction of the diaphragm increases the vertical dimensions of the thoracic cavity and account for the movement of about 75% of the air that enters the lungs during inspiration.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
2-Contraction of external intercostal muscles increases the anterior-posterior diameter of the thoracic cavity.
3-Accessory muscles of inspiration also participate in increasing the size of the thoracic cavity, these include:
a-the sternocleidomastoid m. which elevates the sternum
b-the scalenes m. which elevates the superior two ribs.
c-the pectoralis minor which elevates the third –fifth ribs.
*Eupnea :-mean the normal quit breathing which involves
1-costal breathing:-it is shallow breathing. It consists of an upward and outward movement of the chest as a result of contraction of the external intercostal muscles.
2-Diaphragmatic breathing:-it is deep breathing .It consists of the outward movement of the abdomen as a result of the contraction and descend of the diaphragm.
3-Deep labored inspiration (breathing): It consists of the outward movement of the abdomen as a result of the contraction of the diaphragm and accessory muscles of inspiration.
*The pressure between the two pleural layers called intraplural pressure (always sub atmosphere pressure=756mmHg).
The Ipp ↓ during inspiration (during ↑ed thoracic cavity size).
Contraction of inspiratory m. →↑ volume of the lungs → pressure gradient between atmosphere and alveoli press. grad + IPP →↓ intrapulmonic(alveolar)pressure from 760-758mmHg.→ inflow of the air .
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Expiration (exhalation) or breathing out
Is also achieved by a pressure gradient.
-Normal expiration during quiet breathing is a passive process since no muscular contraction are involved .It depends on the elasticity of the lungs
-Expiration starts when the inspiratory muscles are relaxed. These movement (relaxation of insp. muscles) decrease the diameters of thoracic cavity (vertical and anterior- posterior dimensions) and then returns to its resting size.
Decrease the volume of thoracic cavity → ↑pressure (intrapulmonic)
=763→↑ IPP → expiration.
*During higher level of ventilation, muscles of expiration contract.
These muscles are:
1-Abdominal m.: contraction of these muscles →moves the inferior ribs downward and compresses the abdominal viscera →forcing the diaphragm upward.
2- Internal intercostal m.:-Contraction of these muscles →moves the ribs downward.
At the end of expiration, the alveoli attempt to recoil inward and collapse on themselves. This collapse is prevented by
1-intrapleural pressure that make lungs slightly inflated
2-the pressure of surfactant, lining the alveoli, will decreases the surface tension and prevent the collapse of alveoli.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Atelectasis:
Atelectasis means collapse of the alveoli. It can occur in localized areas of a lung or in an entire lung. Its most common causes are (1) total obstruction of the airway or (2) lack of surfactant in the fluids lining the alveoli.
*Atelectasis:-collapsing of lung or portion of lung.
*A deficiency of surfactant in infants results in a disorder called respiratory distress syndrome (RDS) of the newborn.
*Compliance: is the ease with which the lungs and thoracic wall can be expanded.
↑com.→ easily expansion of lungs and thoracic walls
↓com→ the lungs and thoracic walls resist expansion.
Compliance is related to two principal factors:-
1-Elaticity:-the presence of elastic fiber in lung tissue result in high
Compliance.
2-surface tension:-↑surface tension within lung tissue →resistance to expansion →↓compliance. but the presence of surfactant →↓Surface tension and therefor ↑compliance.
*Any condition that destroy lungs tissues →↓compliance
1-Fibrosis 2-Edema 3-deficiency of surfactant 4-any way impedes lung expansion.
Airway resistance:-
The walls of resp. passageways (especially bronchi and bronchiols offer some resistance to the normal flow of air into the lungs.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
The muscle contraction of normal respiration not only expanse the thoracic cavity but also help to overcome resistance to air flow.
Volume –pressure curve.
In isolated dog lung, when lung inflated under a pressure, the following events seen:-
1-During inflation
a-At first the volume of the lung before pumping is normal (50ml)
b-Then a large increase in pressure (up to12mm Hg)leads to small increase in inflation (volume of lung).
(This is due to lung elasticity coming from elastic tissue of the lung and the presence of surfactant) c- After that small increase in pressure leads to large inflation.
2-During deflation a-At start of deflation ,pressure drops rapidly but the volume decreased slowly (because of lung elasticity). b-Then small decrease in pressure leads large decrease in volume(down to 50ml).
*This experiment indicate that there is a role of compliance during inspiration and expiration
Respiratory volumes and capacities
Respiratory rate in different animals:-
Horse =12resp. ∕ min.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Pigs =13 , adult man =12, cow=20
Dog =20 , cat=25 , sheep=16
Spirometer: is the instrument used in measuring the respiratory rate and capacity (also called respirometer)
Spirogram (spirometery):-is the process of recording the resp. rate and capacities.
Spirogram of pulmonary volumes and capacities
1. The tidal volume is the volume of air inspired or expired with each normal breath; it amounts to about 500 milliliters in the adult male.
2. The inspiratory reserve volume is the extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force; it is usually equal to about 3000 milliliters.
3. The expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration; this normally amounts to about 1100 milliliters.
4. The residual volume is the volume of air remaining in the lungs after the most forceful expiration; this volume averages about 1200 milliliters.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Pulmonary Capacities
In describing events in the pulmonary cycle, it is sometimes desirable to consider two or more of the volumes together. Such combinations are called pulmonary capacities.To the right in Figure are listed the important pulmonary capacities, which can be described as follows:
1. The inspiratory capacity equals the tidal volume plus the inspiratory reserve volume. This is the amount of air (about 3500 milliliters) a person can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount.
2. The functional residual capacity equals the expiratory reserve volume plus the residual volume. This is the amount of air that remains in the lungs at the end of normal expiration (about 2300 milliliters).
3. The vital capacity equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume. This is the maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent (about 4600 milliliters).
4. The total lung capacity is the maximum volume to which the lungs can be expanded with the greatest possible effort (about 5800 milliliters); it is equal to the vital capacity plus the residual volume. All pulmonary volumes and capacities are about 20 to 25 per cent less in women than in men, and they are
greater in large and athletic people than in small and asthenic people.
Rv= Residual volume
IRv=Inspiratory Reserve Volume
ERV =expiratory Reserve Volume
TV=Tidal volume 14
Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Tidal volume: - is the volume of air inspired or expired with each normal breath. (TV=500ml).
Inspiratory reserve Volume:-is the extra volume of air that can be inspired over the normal tidal volume (IRV= 3000ml).
Expiratory reserve volume : is the amount of air that can still be expired by forceful expiration after the end of a normal expiration (ERV= 1100ml).
Residual volume : is volume of the air still remaining in the lungs after the forceful expiration (RV = 1200ml).
A person can breathe beginning at the normal expiratory level & distending his lungs to the maximum amount.
The inspiratory capacity (IC) = TV + IRV = 3500 ML.
The functional residual capacity (FRC) = ERV+ RV = 2300ml.
It is the amount of air remaining in the lungs at the end of normal expiration.
The vital capacity (vc):- = IRV + TV + ERV = 4600ml.
It is the maximum amount of air that a person can expel from the lungs after maximum inspiration & maximum expiration.
The total lungs capacity: (TLC) := IRV + TV + ERV + RV = 5800ml.
It is the maximum volume to which the lungs can be expanded with the greatest possible inspiratory effort.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Exchange of respiratory Cases:
As soon as the lungs fill with air, O2 diffuse from the alveoli into the blood
& through the interstitial fluid & finally into the cells. CO2 diffuses in the opposite direction – from cells, through interstitial fluid to blood & to the alveoli.
* to understand how resp. gases are exchanged in the body. You need to know a few gas laws:-
Charles's Law:- the volume of gas is directly proportional to its absolute temperature in constant pressure (↑ temp →↑ volume and vice versa).
Dalton's Law: - each gas is a mixture of gases exerts its own pressure as if all the other gases were not present. This pressure is called partial pressure (P). e.g / atmospheric pressure = Po2 + Pco2 + PN2 + PH2o
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
O2= 21 % of atmosphere air , so Po2 = 21% × 760 = 160 mm Hg.
CO2=0.04 % of atmosphere air, so , PCO2= 0.04% × 760 = 0.3 mm.Hg
2- External Respiration: Is the exchange of O2 & CO2 between the alveoli of the lungs & pulmonary blood capillaries.
The PO2 of the deoxygenated blood entering the pulmonary capillaries = 40 mm.Hg. & the PO2 of alveolar air = 105 mm.Hg. As a result of this differences in Po2, O2 diffuses from the alveoli into deoxygenated blood until equilibrium is reached so that the Po2 of the blood reach 105= mmHg.
At the same time the CO2 diffuses in the opposite direction. The Pco2 of deoxygenated blood entering the pulmonary capillaries = 45 mmHg. & the Pco2 of alveolar air = 40mmHg. Because of this differences in Pco2, CO2 diffuses from pulmonary deoxygenated blood into the alveoli until the Pco2 of the blood decreases to 40 mmHg.
Thus the Po2 & Pco2 of oxygenated blood leaving the lungs are the same as in alveolar air.
External respiration: is aided by several anatomic adaptations
1- Low thickness of the respiratory membrane (alveolar – capillary memb.) which is equal to 0.5µ m (µm=micrometer).
* Thicker membrane would restrict diffusion.
2- Large surface area through which diffusion occur = 70 m2 . 3- Extensive networks of capillaries lying over the alveoli .
* so that 100 ml of blood is able to participate in gas exchange at any time
4- Narrow diameter of capillaries, so that single of blood cells, can flow through them.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
* this feature gives each RBC maximum exposure to the available oxygen.
The efficiency of external respiration depends on factors:-
1- Altitude (one of most important factors) in altitude Po2 decreases in
atmosphere → ↓alveolar Po2→↓ O2 diffusion into the blood. e.g At sea level Po2 = 160 mmHg.
At 10,000 ft Po2 = 110 mm Hg.
At 20,000 ft Po2 = 73 mm Hg.
At 50,000 ft Po2 = 18 mm Hg.
2- The total surface area available for O2 - CO2 exchange .
Any pulmonary disorder that decreases the functional surface area→↓
The efficiency of external respiration.
3- The minute volume of respiration.
e.g / morphine respiration rate → ↓ amount of O2 and CO2 that can be exchanged between the alveoli & the blood.
4- The diffusion distance.
e.g pulmonary edema → ↑ thickness of respiratory membrane →
↑ diffusion distance.
퐴푟푒푎 (퐴) *Diffusion rate (Dr) = X P (P1 – P2) 푡ℎ𝑖푐푘푛푒푠푠 (푇)
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
3- Internal Respiration :
Is the exchange of O2 & CO2 between tissue blood capillaries & tissue cells.
Oxygenated blood entering tissue capillaries has a Po2 = 105 mm Hg, whereas tissue cells have a Po2 = 40 mm Hg. Because of this difference in Po2 , O2 diffuses from the oxygenated blood through interstitial fluid & into tissue cells until the Po2 in the blood decreases to 40 mm Hg.
*At rest, only 25% of O2 in oxygenated blood enters tissue cells, during exercise, more O2 is released.
At the same time the CO2 diffusion in the opposite direction. The Pco2 of tissue cells = 45 mm hg, whereas that of tissue capillary oxygenated blood = 40 mmhg.
As a result, CO2 diffuses from cells through interstitial fluid into the oxygenated blood until the PCO2 in the blood increases to 45 mm hg.
* The deoxygenated blood now returns to the heart. From here it is pumped to the lungs for another cycle of external respiration.
Transport of Respiratory Gases:
The transportation of respiratory gases between the lungs & body tissue is a function of the blood. When O2 & CO2 enter the blood, certain physical & chemical changes occur that aid in gas transport & exchange.
Oxygen Transport:-
1- 3% of O2 dissolved in plasma.
2- 97% of O2 is carried in chemical combination with Hb in RBC.
* Hemoglobin & Po2
PO2 is the most important factor that determine how much oxygen combines with Hb.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
* When Hb is completely converted to HbO2 it is fully saturated.
* When Hb consist of a mixture of Hb & HbO2 , it is partially saturated
퐻푏푂2 * Hb saturation %= x 100. 푡표푡푎푙 퐻푏 oxygen -Hb dissociation curve in the relationship between the percent saturation of Hb & Po2.
* When PO2 is high → Hb binds with large amount of O2 or fully saturated.
* When PO2 is low → Hb binds little amount of O2 or partially saturated.
↑ PO2 ↑ HbO2 & Hb.CO2
↓PO2 ↓ HbO2 & Hb.CO2
In pulmonary capillaries
High PO2 ↑ HbO2 reaching saturation (oxygenated blood)
In tissue capillaries
Low PO2 ↓ HbO2 (release of O2) (deoxygenated blood)
O2- Hb dissociation curve showing the relationship between PO2 & Hb saturation .
(Also called normal O2 – Hb dissociation curve)
* Hemoglobin & PH:
PH is another factor determine the amount of O2 released from hemoglobin.
* In acidic environment (low PH) (high PCO2), O2 splits more readily from Hb. (This is called Bohr effect) which is due to high concentration of H+ which bind to Hb and alter the Hb structure leading to decrease the Hb oxygen – carrying capacity. 21
Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
+ ( ↑PCO2 → ↑ [H ] low PH HbO2)
+ CO2 + H2O ↔H2CO3 ↔ H + HCO3
Carbonic anhydrase is an enzyme formed in the RBC.
O2-Hb dissociation curve showing the relationship between Hb saturation & PH
(PCO2)
↓PCO2→↑ ↑PH →↑Hb saturation
↑PCO2→ ↓PH→ ↓ Hb saturation
Normal PCO2→ Normal PH →Normal Hb saturation
* Hemoglobin & Temperature:
As temperature increases releasing of O2 from Hb. e.g. / in body tissue, when the metabolism is increased there is a high energy liberated leading to increased temperature releasing of O2 from Hb to maintain aerobic oxidation necessary for metabolism.
*Splitting the oxyhemoglobin molecule is another example of how homeostatic mechanisms adjust body activities to cellular needs.
Active cells require more O2 & active cells liberate more acid & heat. The acid
& heat, in turn stimulate the HbO2 to release its O2.
*Hemoglobin & DPG
*DPG is 2,3 diphosphoglycerate : It is a substance formed in RBC during glycolysis helps to release O2 from hemoglobin.
HbO2 + DPG → Hb. DPG +O2
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
* Fetal Hb differ from adult Hb in structure & in its affinity for O2 because fetal
Hb cannot bind to DPG & thus can carry as much as 20 – 30 % more O2 than maternal Hb.
Hypoxia
It is a deficiency of O2 at the tissue level. Based on the causes, hypoxia classified as follows:
1- Hypoxic hypoxia :- it is caused by a low PO2 in arterial blood which may be a result of: a. High attitude b. Obstructions of air passageway. c. Fluid in the lungs. 2- Anemic hypoxia:- caused by two little functioning Hb in the blood. Which may be a result of :- a- Hemorrhage b- Anemia
c- Failure of Hb to carry its normal completed of O2 as in CO poisoning.
3- Stagnant hypoxia :- caused by inability of blood to carry O2 to tissue, fast enough to sustain their need which may be a result of: a. Heart failure. b. Circulatory shock.
4- Histotoxic hypoxia : in this condition, the blood delivers adequate O2 to tissue,but the tissue are unable to use it properly which result from : a. Cyanide poisoning :
Cyanide blocks the metabolic machinery of cells related to oxygen utilization.
Carbon Dioxide Transport
1- 7% dissolved in plasma
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
2- 23% combine with Hb to form carbohemoglobin.
- 3- 70% transfer in plasma as bicarbonate (HCO3 )
CO2 + Hb → Hb CO2 (carbohemoglobin)
+ - CO2 + H2O → H2CO3→ H + HCO 3
- * CO2 from tissues tissue capillaries enter the RBC to form HCO 3+
+ + - - H (H + Hb → HHb) HCO 3 leave the RBC to plasma & Cl enter the RBC (for ionic balance) This is called chloride shift (the exchange of negative ions maintain the ionic balance between plasma & RBC).
Cl- +K+ → KCl inside the RBC
- + HCO 3 + Na →Na HCO3 in the plasma.
In the lungs:
1- Dissolved CO2 in the plasma by diffusion to the alveoli.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
2- Carbaminohomeglobin →Hb + CO2 + CO2 diffuse to alveoli depend on
PCO2.
- 3- Bicarbonate (HCO3 ): CO2 is released as follows:
+ HHb + O2→HbO2 + H (inside RBC)
+ - NaHCO3→ Na +HCO 3 (in the plasma)
KCl → K+ + Cl- (inside the RBC)
- - HCO 3 enter the RBC instead of Cl leave RBC.
- HCO 3+H → H2CO3 ↔ CO2 + H2O
CO2 then diffuse into alveoli
Control of Respiration:
1- Neural control of Respiration
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Respiration is controlled involuntary by centers found in the brain (in the medulla oblongata & pons)
*Note: there is a voluntary control of respiration by cerebral cortex but just for some time.
These centers are classified into the following areas:-
a. Inspiratory center it is a group of neurons localized in the dorsal part of the medulla at the left & right sides. Stimulation of this receptor lead to inspiration by stimulation of inspiratory muscles (diaphragm & external intercostal muscles ). b. Expiratory Center: is a group of neurons localized in the medulla superior & lateral to the inspiratory center. Stimulation of this center will lead to expiration. (Labor expiration) by stimulation of expiratory muscles.
c. Apneustic center is group of neurons localized at the left & right sides of pons. This center controls the inspiratory center.
d. pneumotaxic center is group of neurons localized at the left & right sides superior to the apneustic center in the pons. This center control the
inspiratory indirectly via the apneustic center.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
The role of respiratory centers in respiration can be summerized as follows:-
1- Inspiratory center stimulate the inspiratory muscles continuously by: a. Left & right phrenic nerves to the diaphragm. b. Intercostal nerves to the external intercostal muscles.
This stimulation will lead to inspiratory (increased thoracic cavity & lungs)
2- There are receptors found in the wall of the lung called stretch receptors. During lungs inflation will lead to stimulation of these receptors & impulses conduct via vagus nerve to the apneustic center to inhibit it. 3- The inhibition of the apneustic center will inhibit the inspiratory center which lead to relaxation of inspiratory muscles which lead to expiration.
4- Expiration & the decrease in the lungs volume will inhibit the stretch receptor. This will lead to relieve the inhibitory effect of vagus nerve on the apneustic center & this will lead to stimulate the inspiratory center again.
5- Pneumotaxic center also play an important in regulation of respiration. During stimulation of inspiratory center to stimulate the inspiratory muscles to contract, the inspiratory center send impulses to the pneumotaxic center to stimulate it. This stimulation of pneumotaxic center will lead to.
a. Inhibition of apneustic center. b. Stimulation of expiratory center.
6-The role of expiratory center is limited during quite respiration, but it is important during labor respiration in case of exercises or in diseases condition.
Chemical control of Respiration:
CO2& PH respiratory rate
O2 respiratory rate. 26
Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
a. Central chemoreceptor it is a chemosensetive area found in the ventral surfaced of the medulla oblongata.
It is sensitive to the hydrogen ion concentration.
CO2 in the blood CO2 in the cerebrospinal fluid
+ H2CO3 H st. the chemosensetive area.
St. the inspiratory center.
b. Peripheral chemoreceptor sensetive to ↑CO2 , ↓O2, ↓PH.
1- Carotid bodies sensitive to ↓O2 gloss pharyngeal st. insp.center.
2- Aortic bodies sensitive to↓ O2 vagus nerve . st.insp.center.
3- Other receptor influence respiration:
a. Lungs receptors. 1- Pulmonary stretch receptors. 2- Irritant receptors a) smoking b) cold c) inhaled dust. 3- Jaxta – capillary receptor , (found in bronchi & bronchioles )sensitive to chemicals also. b. Receptors outside the lungs. 1- Nose & upper airways receptors: stimulated chemically & mechanically leading to sneezing, coughing ,etc. 2- Joint receptors & muscles receptors pain respiration. 3- Gamma system:- any obstruction in the passage way 4- Arterial baroreceptors : ↑blood pressure→st. at baroreseptors→
hypoventilation
↓bl. Pressure inhibition of baroreceptor hyperventilation
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Respiratory Disorders:
Bronchial asthma it is reversible obstructive airway disease characterized by periods of coughing, difficult breathing & wheezing that reverse either spontaneously or with treatment.
Bronchial asthma is usually caused by allergic hypersensitivity of the person to foreign substances in the air.
The following events are usually included in Br. Asthma:-
1- Attacks are brought on by spasms of the smooth muscles that lie in the walls of smaller bronchi & bronchioles causing the passageways to close partially. 2- The patient has trouble exhaling & the alveoli may remain inflated during expiration. 3- The mucous membrane that line the respiratory passageways become irritated & secrets excessive amounts of mucus that may clog the bronchi & bronchioles there are two major varieties of asthma:- 1- Extrinsic asthma : occurring in childhood or early adulthood, which is due to respiratory allergies.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
2- Intrinsic asthma: occurring in adults after age 45 & its cause is other than just allergies.
Bronchitis:
Is inflammation of the bronchi characterized by hypertrophy & hyperplasia of seromucous glands & global cells lining the bronchial airways.
*The typical symptom is a productive cough in which a thick green – ash – yellow sputum is raised.
* The most important cause of chronic bronchitis is cigarette smoking.
Emphysema
In emphysema, the alveolar walls lose their elasticity &remain filled with air during expiration. The first symptom is reduced forced expiratory volume & later, alveoli of other areas of the lungs are damaged. The patient has to work voluntary to exhale & the O2 diffusion does not occur as easily across the damage alveolar – capillary membrane emphysema is generally caused by a long – term irritation by air pollution or cigarette smoke.
Pneumonia
It is an acute infection or inflammation of lungs tissue (especially alveoli). In this disease, the alveolar sacs fill up with fluid & dead WBC reducing the amount of air space in the lungs.
The most common case of pneumonia is the pneumococcus bacterium (streptococcus pneumonia)
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Respiratory failure
It is a condition in which the respiratory system cannot supply sufficient O2 to maintain metabolism or cannot eliminate enough CO2 to prevent respiratory acidosis.
Pulmonary embolism
It is the presence of blood a lot or other foreign substance in a pulmonary area arterial vessel that obstruct circulation to lung tissue.
Pulmonary edema
It is an abnormal accumulation of fluid in that interstitial space & alveoli of the lungs.
Causes (1) pulmonary origin:- increased pulmonary capillary permeability
(2) cardiac origin: increased pulmonary capillary pressure . e.g congestive heart failure symptom
(1) Dyspnea (the most common symptom)
(2) Wheezing
(3) Tachypnea
(4) Restlessness
(5) Cyanosis
(6) Paleness
(7) Diaphoresis
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Smoke inhalation injury:
Has three components that occur in sequence:
1- Inhibition of O2 delivery & utilization 2- Upper airway injury from heat. 3- Lungs damage from acids & aldehydes in smoke.
* The first one is due to inhalation of CO & cyanide.
*The second one may cause edema of the laryngotrachial mucosa & obstruction of upper airways with atelectasis (collapsed lungs)
* The third one result in bronchocostriction, atelectasis bronchiolar edema, impairment , of mucociliary action & destruction of surfactant.
Medical Terminology Associated with the Resp. System.
Asphyxia: O2 starvation due to low atmosphere O2 or interference with ventilation external respiration or internal respiration.
Aspiration: Inhalation of a foreign substance such as water, food, or foreign body into the bronchial tree.
Bronchiectasis: A chronic dilation of the bronchi or bronchioles.
Diphtheria: an acute bacterial infection that causes the mucous membranes of the oropharynx, nasopharynx & larynx to enlarge &became leathery.
Dyspnea: painful or labored breathing.
Epistaxis: Loss of blood from the nose due to trauma infection, allergy, neoplasms & bleeding disorders.
Hemoptysis: spitting of blood from the respiratory tract.
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Theoretical Physiology Lect (6) Dr. Khama’al Al-khafaji
Cyanosis: blueness of the skin due to the excessive amount of deoxygenated blood in the skin blood vessels.
Pneumonectomy: surgical removal of a lungs.
Rales : Sounds sometimes heard in the lungs that resemble bubbling or rattling.
Rhinitis: Chronic or acute inflammation of the mucous membrane of the nose.
Avian Respiratory System:
There are many differences between mammalian & avian respi. System in structures& action.
1- Lungs volume is smaller in birds than in mammalian & located dorsally in the chest cavity & close to the ribs, thus they cannot inflated as much as mammalian lungs inflation. 2- There are nine air sacs related to the lungs, five are dorsally located & four are ventrally located. These air sacs play an important role in respiration. 3- There is no diaphragm in the birds &the thoracic cavity open directly to the abdominal cavity.
* Gas exchange occur in the tertiary.
* During inspiration air flows:
1- Nostril → abdominal air sacs (oxygenated)
2- from lungs to the anterior air sacs (deoxygenated)
* During expiration air flows: (1) Anterior air sacs to the outside. (2) from abdominal air sacs (oxygenated) to the lungs through recurrent bronchi.
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