1. The Respiratory System
Biology 1612 Lecture Outline
K. Donaldson, M.S.
Georgia Perimeter College

2. INTRODUCTION
The two systems that cooperate to supply O2 and eliminate CO2 are the cardiovascular and the respiratory system.
The respiratory system provides for gas exchange.
The cardiovascular system transports the respiratory gases.
Failure of either system has the same effect on the body: disruption of homeostasis and rapid death of cells from oxygen starvation and buildup of waste products.
Respiration is the exchange of gases between the atmosphere, blood, and cells. It takes place in three basic steps: ventilation (breathing), external (pulmonary) respiration, and internal (tissue) respiration.

3. The Respiratory System
Cells continually use O2 & release CO2
Respiratory system designed for gas exchange
Cardiovascular system is what transports gases in blood
Failure of either system leads to rapid cell death from O2 starvation

4. Respiratory System Anatomical Terms
Nose
Pharynx = throat
Larynx = voice box
Trachea = windpipe
Bronchi = airways
Lungs
Terms to indicate locations of respiratory infections:
upper respiratory tract is above vocal cords
lower respiratory tract is below vocal cords
The conducting system consists of a series of cavities and tubes - nose, pharynx, larynx, trachea, bronchi, bronchiole, and terminal bronchioles - that conduct air into the lungs.
The respiratory portion consists of the area where gas exchange occurs - respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

5. External Nasal Structures
Skin, nasal bones, & cartilage lined with mucous membrane
Openings are called external nares or nostrils

6. External Anatomy
The external portion of the nose is made of cartilage and skin and is lined with mucous membranes. Openings to the exterior are the external nares or nostrils.
The external portion of the nose is made of cartilage and skin and is lined with mucous membranes.
The bony framework of the nose is formed by the frontal bone, nasal bones, and maxillae.

7. Internal Anatomy
The interior structures of the nose are specialized for warming, moistening, and filtering incoming air; receiving olfactory stimuli; and serving as large, hollow resonating chambers to modify speech sounds.
The internal portion of the nose communicates with the paranasal sinuses and nasopharynx through the internal nares.
The inside of both the external and internal nose is called the nasal cavity. It is divided into right and left sides by the nasal septum. The anterior portion of the cavity is called the vestibule.

8. Nasal Polyps
Nasal polyps are outgrowths of the mucous membranes which are usually found around the openings of the paranasal sinuses.
They are soft, noncancerous (benign) growths that develop on the lining of your nose or sinuses.
Small nasal polyps usually cause few problems, but larger ones can affect your breathing and diminish your sense of smell. Sometimes they may cause dull headaches or snoring, and in rare cases, massive nasal polyps can alter the shape of your face.
Nasal polyps result from chronic inflammation in the lining of your nose or sinuses, but just what triggers the inflammation isn't always clear.
Although nasal polyps can affect anyone, they're more common in people older than 40 and in adults and children with conditions such as asthma, chronic sinus infections, hay fever and cystic fibrosis.

9. Nose -- Internal Structures
Large chamber within the skull
Roof is made up of the ethmoid bone and floor is hard palate
Internal nares (choanae) are openings to pharynx
In the lateral walls of either fossa are three shell-like concavities: the superior, middle and inferior conchae. Air passages or meatuses connect the conchae.
The nostrils (external nares) open anteriorly into the nasal cavity and the
choanae (posterior nares) communicate posteriorly with the nasopharynx.
Nasal septum is composed of bone & cartilage.

10. Functions of the Nasal Structures
Specialized columnar epithelium called olfactory epithelium lines the upper medial portion of the nasal cavity and responds to odors.
Pseudostratified ciliated columnar epithelium with goblet cells lines nasal cavity. The function is to:
warms air due to high its high vascularity
mucous moistens air & traps dust, pollens, smoke and other airborne particles
cilia move mucous towards pharynx where it can be removed
Paranasal sinuses open into nasal cavity:
The four paranasal sinuses are the ethmoid, sphenoid, frontal & maxillary sinuses.
Their function is to lighten the overall weight of the skull and to act as sound chambers for voice resonance.

11. Rhinoplasty
Rhinoplasty (“nose job”) is a surgical procedure in which the structure of the external nose is altered for cosmetic or functional reasons (fracture or septal repair)
Procedure:
local and general anesthetic
nasal cartilage is reshaped or removed by entering through nostrils
bones fractured and repositioned
internal packing & splint while healing

12. Pharynx - Overview
The pharynx (throat) is a muscular tube lined by a mucous membrane.
The anatomic regions are the nasopharynx, oropharynx, and laryngopharynx.
The nasopharynx functions in respiration.
Both the oropharynx and laryngopharynx function in digestion and in respiration (serving as a passageway for both air and food).

13. Pharynx

14. Pharynx
Muscular tube (5 inch long) hanging from skull composed of skeletal muscle and mucous membranes.
Extends from internal nares to cricoid cartilage
Functions:
passageway for food and air
resonating chamber for speech production
tonsil (lymphatic tissue) in the walls protects entryway into body
Distinct regions -- nasopharynx, oropharynx and laryngopharynx

15. Nasopharynx From choanae to soft palate Passageway for air only
openings of auditory (Eustachian) tubes from middle ear cavity
adenoids or pharyngeal tonsil in roof
Passageway for air only
pseudostratified ciliated columnar epithelium with goblet

16. Oropharynx From soft palate to epiglottis
fauces is opening from mouth into oropharynx
palatine tonsils found in side walls, lingual tonsil in tongue
Common passageway for food & air
stratified squamous epithelium

17. Laryngopharynx Extends from epiglottis to cricoid cartilage
Common passageway for food & air & ends as esophagus inferiorly
stratified squamous epithelium

18. Larynx - Overview
The larynx (voice box) is a passageway that connects the pharynx with the trachea.
It contains the thyroid cartilage (Adam’s apple); the epiglottis, which prevents food from entering the larynx; the cricoid cartilage, which connects the larynx and trachea; and the paired arytenoid, corniculate, and cuneiform cartilages.
Voice Production:
The larynx contains vocal folds (true vocal cords), which produce sound.
Taunt vocal folds produce high pitches, and relaxed vocal folds produce low pitches. Other structures modify the sound.

19. Cartilages of the Larynx
Thyroid cartilage forms Adam’s apple
Epiglottis---leaf-shaped piece of elastic cartilage
during swallowing, larynx moves upward
epiglottis bends to cover glottis
Cricoid cartilage---ring of cartilage attached to top of trachea
Pair of arytenoid cartilages sit upon cricoid
many muscles responsible for their movement
partially buried in vocal folds (true vocal cords)

20. Larynx Cartilage & connective tissue tube Anterior to C4 to C6
Constructed of 3 single & 3 paired cartilages

21. Vocal Cords
False vocal cords (ventricular folds) found above vocal folds (true vocal cords)
True vocal cords attach to arytenoid cartilages

22. The Structures of Voice Production
True vocal cord contains both skeletal muscle and an elastic ligament (vocal ligament)
When 10 intrinsic muscles of the larynx contract, it moves the cartilages & stretches the vocal cord tight
When air is pushed past tight ligament, sound is produced (the longer & thicker vocal cord in male produces a lower pitch of sound)
The tighter the ligament, the higher the pitch
To increase volume of sound, push air harder.

23. Movement of Vocal Cords
Opening and closing of the vocal folds occurs during breathing and speech

24. Speech and Whispering Speech is modified sound made by the larynx.
Speech requires pharynx, mouth, nasal cavity & sinuses to resonate that sound
Tongue & lips form words
Pitch is controlled by tension on vocal folds
pulled tight produces higher pitch
male vocal folds are thicker & longer so vibrate more slowly producing a lower pitch
Whispering is forcing air through almost closed rima glottidis -- oral cavity alone forms speech

25. Laryngitis
Laryngitis is an inflammation of the larynx that is usually caused by respiratory infection or irritants.

26. Trachea
The trachea (windpipe) extends from the larynx to the primary bronchi.
It is composed of smooth muscle and C-shaped rings of cartilage and is lined with pseudostratified ciliated columnar epithelium.
The cartilage rings keep the airway open.
The cilia of the epithelium sweep debris away from the lungs and back to the throat to be swallowed.

27. Trachea Size is 5 in long & 1in diameter
Extends from larynx to T5 anterior to the esophagus and then splits into bronchi
Layers
mucosa = pseudostratified columnar with cilia & goblet
submucosa = loose connective tissue & seromucous glands
hyaline cartilage = 16 to 20 incomplete rings
open side facing esophagus contains trachealis m. (smooth)
internal ridge on last ring called carina
adventitia binds it to other organs

28. Trachea and Bronchial Tree
Full extent of airways is visible starting at the larynx and trachea

29. Histology of the Trachea
Ciliated pseudostratified columnar epithelium
Hyaline cartilage as C-shaped structure closed by trachealis muscle

30. Airway Epithelium
Ciliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus.

31. Tracheostomy and Intubation
Reestablishing airflow past an airway obstruction
crushing injury to larynx or chest
swelling that closes airway
vomit or foreign object
Tracheostomy is incision in trachea below cricoid cartilage if larynx is obstructed
Intubation is passing a tube from mouth or nose through larynx and trachea

32. Bronchi The trachea divides into the right and left pulmonary bronchi.
The bronchial tree consists of the trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles, and terminal bronchioles.
Walls of bronchi contain rings of cartilage.
Walls of bronchioles contain smooth muscle.

33. Bronchi and Bronchioles
Primary bronchi supply each lung
Secondary bronchi supply each lobe of the lungs (3 right + 2 left)
Tertiary bronchi supply each bronchopulmonary segment
Repeated branchings called bronchioles form a bronchial tree

34. Histology of Bronchial Tree
Epithelium changes from pseudostratified ciliated columnar to nonciliated simple cuboidal as pass deeper into lungs
Incomplete rings of cartilage replaced by rings of smooth muscle & then connective tissue
sympathetic NS & adrenal gland release epinephrine that relaxes smooth muscle & dilates airways
asthma attack or allergic reactions constrict distal bronchiole smooth muscle
nebulization therapy = inhale mist with chemicals that relax muscle & reduce thickness of mucus.

35. Pleural Membranes & Pleural Cavity
Visceral pleura covers lungs --- parietal pleura lines ribcage & covers upper surface of diaphragm
Pleural cavity is potential space between ribs & lungs

36. Lungs - Overview
Lungs are paired organs in the thoracic cavity; they are enclosed and protected by the pleural membrane .
The parietal pleura is the outer layer which is attached to the wall of the thoracic cavity.
The visceral pleura is the inner layer, covering the lungs themselves.
Between the pleurae is a small potential space, the pleural cavity, which contains a lubricating fluid secreted by the membranes.
The pleural cavities may fill with air (pneumothorax) or blood (hemothorax).
A pneumorthorax may cause a partial or complete collapse of the lung.
The lungs extend from the diaphragm to just slightly superior to the clavicles and lie against the ribs anteriorly and posteriorly.

37. Lungs - Overview The lungs almost totally fill the thorax.
The right lung has three lobes separated by two fissures; the left lung has two lobes separated by one fissure and a depression, the cardiac notch.
The secondary bronchi give rise to branches called tertiary (segmental) bronchi, which supply segments of lung tissue called bronchopulmonary segments.
Each bronchopulmonary segment consists of many small compartments called lobules, which contain lymphatics, arterioles, venules, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli.

38. Gross Anatomy of Lungs
Base, apex (cupula), costal surface, cardiac notch
Oblique & horizontal fissure in right lung results in 3 lobes
Oblique fissure only in left lung produces 2 lobes

39. Mediastinal Surface of Lungs
Blood vessels & airways enter lungs at hilus
Forms root of lungs
Covered with pleura (parietal becomes visceral)

40. Structures within a Lobule of Lung
Branchings of single arteriole, venule & bronchiole are wrapped by elastic CT
Respiratory bronchiole
simple squamous
Alveolar ducts surrounded by alveolar sacs & alveoli
sac is 2 or more alveoli sharing a common opening

41. Alveoli
Alveolar walls consist of type I alveolar (squamous pulmonary epithelial) cells, type II alveolar (septal) cells, and alveolar macrophages (dust cells).
Type II alveolar cells secrete alveolar fluid, which keeps the alveolar cells moist and which contains a component called surfactant. Surfactant lowers the surface tension of alveolar fluid, preventing the collapse of alveoli with each expiration.
Respiratory Distress Syndrome is a disorder of premature infants in which the alveoli do not have sufficient surfactant to remain open.
Gas exchange occurs across the alveolar-capillary membrane.

42. Histology of Lung Tissue
Photomicrograph of lung tissue showing bronchioles, alveoli and alveolar ducts.

43. Details of Respiratory Membrane

44. Cells Types of the Alveoli
Type I alveolar cells
simple squamous cells where gas exchange occurs
Type II alveolar cells (septal cells)
free surface has microvilli
secrete alveolar fluid containing surfactant
Alveolar dust cells
wandering macrophages remove debris

45. Alveolar-Capillary Membrane
Respiratory membrane = 1/2 micron thick
Exchange of gas from alveoli to blood
4 Layers of membrane to cross
alveolar epithelial wall of type I cells
alveolar epithelial basement membrane
capillary basement membrane
endothelial cells of capillary
Vast surface area = handball court

46. Details of Respiratory Membrane
Find the 4 layers that comprise the respiratory membrane

47. Double Blood Supply to the Lungs
Deoxygenated blood arrives through pulmonary trunk from the right ventricle
Bronchial arteries branch off of the aorta to supply oxygenated blood to lung tissue
Venous drainage returns all blood to heart
Less pressure in venous system
Pulmonary blood vessels constrict in response to low O2 levels so as not to pick up CO2 on there way through the lungs

48. Clinical Applications
Nebulization, a procedure for administering medication as small droplets suspended in air into the respiratory tract, is used to treat many different types of respiratory disorders.
In the lungs vasoconstriction in response to hypoxia diverts pulmonary blood from poorly ventilated areas to well ventilated areas. This phenomenon is known as ventilation – perfusion coupling.

49. PULMONARY VENTILATION
Respiration occurs in three basic steps: pulmonary ventilation, external respiration, and internal respiration.
Inspiration (inhalation) is the process of bringing air into the lungs.
The movement of air into and out of the lungs depends on pressure changes governed in part by Boyle’s law, which states that the volume of a gas varies inversely with pressure, assuming that temperature is constant.

50. Breathing or Pulmonary Ventilation
Air moves into lungs when pressure inside lungs is less than atmospheric pressure
How is this accomplished?
Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressure
Atmospheric pressure = 1 atm or 760mm Hg

51. Boyle’s Law
As the size of closed container decreases, pressure inside is increased
The molecules have less wall area to strike so the pressure on each inch of area increases.

52. Dimensions of the Chest Cavity
Breathing in requires muscular activity & chest size changes
Contraction of the diaphragm flattens the dome and increases the vertical dimension of the chest

53. Inspiration
The first step in expanding the lungs involves contraction of the main inspiratory muscle, the diaphragm.
Inhalation occurs when alveolar (intrapulmonic) pressure falls below atmospheric pressure. Contraction of the diaphragm and external intercostal muscles increases the size of the thorax, thus decreasing the intrapleural (intrathoracic) pressure so that the lungs expand. Expansion of the lungs decreases alveolar pressure so that air moves along the pressure gradient from the atmosphere into the lungs.
During forced inhalation, accessory muscles of inspiration (sternocleidomastoids, scalenes, and pectoralis minor) are also used.

54. Quiet Inspiration Diaphragm moves 1 cm & ribs lifted by muscles
Intrathoracic pressure falls and 2-3 liters inhaled

55. Expiration
Expiration (exhalation) is the movement of air out of the lungs.
Exhalation occurs when alveolar pressure is higher than atmospheric pressure. Relaxation of the diaphragm and external intercostal muscles results in elastic recoil of the chest wall and lungs, which increases intrapleural pressure, decreases lung volume, and increases alveolar pressure so that air moves from the lungs to the atmosphere. There is also an inward pull of surface tension due to the film of alveolar fluid.
Exhalation becomes active during labored breathing and when air movement out of the lungs is impeded. Forced expiration employs contraction of the internal intercostals and abdominal muscles.

56. Quiet Expiration Passive process with no muscle action
Elastic recoil & surface tension in alveoli pulls inward
Alveolar pressure increases & air is pushed out

57. Labored Breathing Forced expiration Forced inspiration
abdominal mm force diaphragm up
internal intercostals depress ribs
Forced inspiration
sternocleidomastoid, scalenes & pectoralis minor lift chest upwards as you gasp for air

58. Intrapleural Pressures
Always subatmospheric (756 mm Hg)
As diaphragm contracts intrathoracic pressure decreases even more (754 mm Hg)
Helps keep parietal & visceral pleura stick together

59. Summary of Breathing Alveolar pressure decreases & air rushes in
Alveolar pressure increases & air rushes out

60. Alveolar Surface Tension
Thin layer of fluid in alveoli causes inwardly directed force = surface tension
water molecules strongly attracted to each other
Causes alveoli to remain as small as possible
Detergent-like substance called surfactant produced by Type II alveolar cells
lowers alveolar surface tension
insufficient in premature babies so that alveoli collapse at end of each exhalation

61. Compliance of the Lungs
Ease with which lungs & chest wall expand depends upon elasticity of lungs & surface tension
Some diseases reduce compliance
tuberculosis forms scar tissue
pulmonary edema --- fluid in lungs & reduced surfactant
paralysis

62. Airway Resistance Resistance to airflow depends upon airway size
increase size of chest
airways increase in diameter
contract smooth muscles in airways
decreases in diameter

63. Breathing Patterns
Eupnea is normal variation in breathing rate and depth.
Apnea refers to breath holding.
Dyspnea relates to painful or difficult breathing.
Tachypnea involves rapid breathing rate.
Costal breathing requires combinations of various patterns of intercostal and extracostal muscles, usually during need for increased ventilation, as with exercise.
Diaphragmatic breathing is the usual mode of operation to move air by contracting and relaxing the diaphragm to change the lung volume.
Modified respiratory movements are used to express emotions and to clear air passageways.

64. Modified Respiratory Movements
Coughing
deep inspiration, closure of rima glottidis & strong expiration blasts air out to clear respiratory passages
Hiccuping
spasmodic contraction of diaphragm & quick closure of rima glottidis produce sharp inspiratory sound

65. LUNG VOLUMES AND CAPACITIES
Air volumes exchanged during breathing and rate of ventilation are measured with a spiromometer, or respirometer, and the record is called a spirogram.
Among the pulmonary air volumes exchanged in ventilation are tidal (500 ml), inspiratory reserve (3100 ml), expiratory reserve (1200 ml), residual (1200 ml) and minimal volumes. Only about 350 ml of the tidal volume actually reaches the alveoli, the other 150 ml remains in the airways as anatomic dead space.
Pulmonary lung capacities, the sum of two or more volumes, include inspiratory (3600 ml), functional residual (2400 ml), vital (4800 ml), and total lung (6000 ml) capacities.
The minute volume of respiration is the total volume of air taken in during one minute (tidal volume x 12 respirations per minute = 6000 ml/min).

66. Lung Volumes and Capacities
Tidal volume = amount air moved during quiet breathing
MVR= minute ventilation is amount of air moved in a minute
Reserve volumes ---- amount you can breathe either in or out above that amount of tidal volume
Residual volume = 1200 mL permanently trapped air in system
Vital capacity & total lung capacity are sums of the other volumes

67. EXCHANGE OF OXYGEN AND CARBON DIOXIDE
To understand the exchange of oxygen and carbon dioxide between the blood and alveoli, it is useful to know some gas laws.
According to Dalton’s law, each gas in a mixture of gases exerts its own pressure as if all the other gases were not present.

68. Dalton’s Law Each gas in a mixture of gases exerts its own pressure
as if all other gases were not present
partial pressures denoted as p
Total pressure is sum of all partial pressures
atmospheric pressure (760 mm Hg) = pO2 + pCO2 + pN2 + pH2O
to determine partial pressure of O2-- multiply 760 by % of air that is O2 (21%) = 160 mm Hg

69. What is Composition of Air?
Air = 21% O2, 79% N2 and .04% CO2
Alveolar air = 14% O2, 79% N2 and 5.2% CO2
Expired air = 16% O2, 79% N2 and 4.5% CO2
Observations
alveolar air has less O2 since absorbed by blood
mystery-----expired air has more O2 & less CO2 than alveolar air?
Anatomical dead space = 150 ml of 500 ml of tidal volume

70. EXCHANGE OF OXYGEN AND CARBON DIOXIDE
The partial pressure of a gas is the pressure exerted by that gas in a mixture of gases. The total pressure of a mixture is calculated by simply adding all the partial pressures. It is symbolized by P.
The partial pressures of the respiratory gases in the atmosphere, alveoli, blood, and tissues cells are shown in the text.
The amounts of O2 and CO2 vary in inspired (atmospheric), alveolar, and expired air.

71. Henry’s Law
Henry’s law states that the quantity of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility coefficient (its physical or chemical attraction for water), when the temperature remains constant.
Nitrogen narcosis and decompression sickness (caisson disease, or bends) are conditions explained by Henry’s law.

72. Henry’s Law
Quantity of a gas that will dissolve in a liquid depends upon the amount of gas present and its solubility coefficient
explains why you can breathe compressed air while scuba diving despite 79% Nitrogen
N2 has very low solubility unlike CO2 (soda cans)
dive deep & increased pressure forces more N2 to dissolve in the blood (nitrogen narcosis)
decompression sickness if come back to surface too fast or stay deep too long
Breathing O2 under pressure dissolves more O2 in blood

73. Hyperbaric Oxygenation
A major clinical application of Henry’s law is hyperbaric oxygenation.
Use of pressure to dissolve more O2 in the blood
treatment for patients with anaerobic bacterial infections (tetanus and gangrene)
anaerobic bacteria die in the presence of O2
Hyperbaric chamber pressure raised to 3 to 4 atmospheres so that tissues absorb more O2
Used to treat heart disorders, carbon monoxide poisoning, cerebral edema, bone infections, gas embolisms & crush injuries

74. Respiration

75. External Respiration
O2 and CO2 diffuse from areas of their higher partial pressures to areas of their lower partial pressures.
Diffusion depends on partial pressure differences
Compare gas movements in pulmonary capillaries to tissue capillaries

76. Rate of Diffusion of Gases
Depends upon partial pressure of gases in air
p O2 at sea level is 160 mm Hg
10,000 feet is 110 mm Hg / 50,000 feet is 18 mm Hg
Large surface area of our alveoli
Diffusion distance (membrane thickness) is very small
Solubility & molecular weight of gases
O2 smaller molecule diffuses somewhat faster
CO2 dissolves 24X more easily in water so net outward diffusion of CO2 is much faster
disease produces hypoxia before hypercapnia
lack of O2 before too much CO2

77. Internal Respiration Exchange of gases between blood & tissues
Conversion of oxygenated blood into deoxygenated
Observe diffusion of O2 inward
at rest 25% of available O2 enters cells
during exercise more O2 is absorbed
Observe diffusion of CO2 outward

78. Oxygen Transport
In each 100 ml of oxygenated blood, 1.5% of the O2 is dissolved in the plasma and 98.5% is carried with hemoglobin (Hb) inside red blood cells as oxyhemglobin (HbO2).
Hemoglobin consists of a protein portion called globin and a pigment called heme.
The heme portion contains 4 atoms of iron, each capable of combining with a molecule of oxygen.

79. Hemoglobin and Oxygen Partial Pressure
The most important factor that determines how much oxygen combines with hemoglobin is PO2.
The greater the PO2, the more oxygen will combine with hemoglobin, until the available hemoglobin molecules are saturated.

80. Hemoglobin and Oxygen Partial Pressure
Blood is almost fully saturated at pO2 of 60mm
people OK at high altitudes & with some disease
Between 40 & 20 mm Hg, large amounts of O2 are released as in areas of need like contracting muscle

81. Oxygen Transport in the Blood
Oxyhemoglobin contains 98.5% chemically combined oxygen and hemoglobin
inside red blood cells
Does not dissolve easily in water
only 1.5% transported dissolved in blood
Only the dissolved O2 can diffuse into tissues
Factors affecting dissociation of O2 from hemoglobin are important
Oxygen dissociation curve shows levels of saturation and oxygen partial pressures

82. Hemoglobin and Oxygen Partial Pressure
Blood is almost fully saturated at pO2 of 60mm
people OK at high altitudes & with some disease
Between 40 & 20 mm Hg, large amounts of O2 are released as in areas of need like contracting muscle

83. Other Factors Affecting Hemoglobin Affinity for Oxygen
In an acid (low pH) environment, O2 splits more readily from hemoglobin. This is referred to as the Bohr effect.
Low blood pH (acidic conditions) results from high PCO2.
Within limits, as temperature increases, so does the amount of oxygen released from hemoglobin. Active cells require more oxygen, and active cells (such as contracting muscle cells) liberate more acid and heat. The acid and heat, in turn, stimulate the oxyhemoglobin to release its oxygen.
BPG (2, 3-biphosphoglycerate) is a substance formed in red blood cells during glycolysis. The greater the level of BPG, the more oxygen is released from hemoglobin.

84. Acidity & Oxygen Affinity for Hb
As acidity increases, O2 affinity for Hb decreases
Bohr effect
H+ binds to hemoglobin & alters it
O2 left behind in needy tissues

85. pCO2 & Oxygen Release
As pCO2 rises with exercise, O2 is released more easily
CO2 converts to carbonic acid & becomes H+ and bicarbonate ions & lowers pH.

86. Temperature & Oxygen Release
As temperature increases, more O2 is released
Metabolic activity & heat
More BPG, more O2 released
RBC activity
hormones like thyroxine & growth hormone

87. Oxygen Affinity & Fetal Hemoglobin
Differs from adult in structure & affinity for O2
When pO2 is low, can carry more O2
Maternal blood in placenta has less O2

88. Review

89. Fetal Hemoglobin
Fetal hemoglobin has a higher affinity for oxygen because it binds BPG less strongly and can carry more oxygen to offset the low oxygen saturation in maternal blood in the placenta.
Because of the strong attraction of carbon monoxide (CO) to hemoglobin, even small concentrations of CO will reduce the oxygen carrying capacity leading to hypoxia and carbon monoxide poisoning.

90. Carbon Monoxide Poisoning
CO from car exhaust & tobacco smoke
Binds to Hb heme group more successfully than O2
CO poisoning
Treat by administering pure O2

91. Carbon Dioxide Transport
CO2 is carried in blood in the form of dissolved CO2 (7%), carbaminohemoglobin (23%), and bicarbonate ions (70%).
The conversion of CO2 to bicarbonate ions and the related chloride shift maintains the ionic balance between plasma and red blood cells.

92. Carbon Dioxide Transport
100 ml of blood carries 55 ml of CO2
Is carried by the blood in 3 ways
dissolved in plasma
combined with the globin part of Hb molecule forming carbaminohemoglobin
as part of bicarbonate ion
CO2 + H2O combine to form carbonic acid that dissociates into H+ and bicarbonate ion

93. Summary of Gas Exchange and Transport in Lungs and Tissues
CO2 in blood causes O2 to split from hemoglobin.
Similarly, the binding of O2 to hemoglobin causes a release of CO2 from blood.

94. Summary of Gas Exchange & Transport

95. Respiratory Center
The area of the brain from which nerve impulses are sent to respiratory muscles is located bilaterally in the reticular formation of the brain stem. This respiratory center consists of a medullary rhythmicity area (inspiratory and expiratory areas), pneumotaxic area, and apneustic area.

96. Role of the Respiratory Center
Respiratory mm. controlled by neurons in pons & medulla
3 groups of neurons
medullary rhythmicity
pneumotaxic
apneustic centers

97. Medullary Rhythmicity Area
The function of the medullary rhythmicity area is to control the basic rhythm of respiration.
The inspiratory area has an intrinsic excitability of autorhythmic neurons that sets the basic rhythm of respiration.
The expiratory area neurons remain inactive during most quiet respiration but are probably activated during high levels of ventilation to cause contraction of muscles used in forced (labored) expiration.

98. Medullary Rhythmicity Area
Controls basic rhythm of respiration
Inspiration for 2 seconds, expiration for 3
Autorhythmic cells active for 2 seconds then inactive
Expiratory neurons inactive during most quiet breathing only active during high ventilation rates

99. Pneumotaxic Area
The pneumotaxic area in the upper pons helps coordinate the transition between inspiration and expiration.
The apneustic area sends impulses to the inspiratory area that activate it and prolong inspiration, inhibiting expiration.

100. Regulation of Respiratory Center
Cortical Influences
voluntarily alter breathing patterns
Cortical influences allow conscious control of respiration that may be needed to avoid inhaling noxious gasses or water.
Voluntary breath holding is limited by the overriding stimuli of increased [H+] and [CO2].
inspiratory center is stimulated by increase in either
if you hold breathe until you faint----breathing will resume

101. Chemoreceptor Regulation of Respiration
A slight increase in PCO2 (and thus H+), a condition called hypercapnia, stimulates central chemoreceptors.
As a response to increased PCO2, increased H+ and decreased PO2, the inspiratory area is activated and hyperventilation, rapid and deep breathing, occurs.
If arterial PCO2 is lower than 40 mm Hg, a condition called hypocapnia, the chemoreceptors are not stimulated and the inspiratory area sets its own pace until CO2 accumulates and PCO2 rises to 40 mm Hg.
Severe deficiency of O2 depresses activity of the central chemoreceptors and respiratory center.

102. Chemical Regulation of Respiration
Central chemoreceptors in medulla
respond to changes in H+ or pCO2
hypercapnia = slight increase in pCO2 is noticed
Peripheral chemoreceptors
respond to changes in H+ , pO2 or PCO2
aortic body---in wall of aorta
nerves join vagus
carotid bodies--in walls of common carotid arteries
nerves join glossopharyngeal nerve

103. Negative Feedback Regulation of Breathing
Negative feedback control of breathing
Increase in arterial pCO2
Stimulates receptors
Inspiratory center
Muscles of respiration contract more frequently & forcefully
pCO2 Decreases

104. Control of Respiratory Rate
Proprioceptors of joints and muscles activate the inspiratory center to increase ventilation prior to exercise induced oxygen need.
The inflation (Hering-Breuer) reflex detects lung expansion with stretch receptors and limits it depending on ventilatory need and prevention of damage.
Other influences include blood pressure, limbic system, temperature, pain, stretching the anal sphincter, and irritation to the respiratory mucosa.
Table 23.2 summarizes the changes that increase or decrease ventilation rate and depth.

105. Regulation of Ventilation Rate and Depth

106. Hypoxia
Hypoxia refers to oxygen deficiency at the tissue level and is classified in several ways.
Hypoxic hypoxia is caused by a low PO2 in arterial blood (high altitude, airway obstruction, fluid in lungs).
In anemic hypoxia, there is too little functioning hemoglobin in the blood (hemorrhage, anemia, carbon monoxide poisoning).
Stagnant hypoxia results from the inability of blood to carry oxygen to tissues fast enough to sustain their needs (heart failure, circulatory shock).
In histotoxic hypoxia, the blood delivers adequate oxygen to the tissues, but the tissues are unable to use it properly (cyanide poisoning).

107. EXERCISE AND THE RESPIRATORY SYSTEM
The respiratory system works with the cardiovascular system to make appropriate adjustments for different exercise intensities and durations.
As blood flow increases with a lower O2 and higher CO2 content, the amount passing through the lung (pulmonary perfusion) increases and is matched by increased ventilation and oxygen diffusion capacity as more pulmonary capillaries open.
Ventilatory modifications can increase 30 times above resting levels, in an initial rapid rate due to neural influences and then more gradually due to chemical stimulation from changes in cell metabolism. A similar, but reversed, effect occurs with cessation of exercise.
Smokers have difficulty breathing for a number of reasons, including nicotine, mucous, irritants, and that fact that scar tissue replaces elastic fibers.

108. Smokers Lowered Respiratory Efficiency
Smoker is easily “winded” with moderate exercise
nicotine constricts terminal bronchioles
carbon monoxide in smoke binds to hemoglobin
irritants in smoke cause excess mucus secretion
irritants inhibit movements of cilia
in time destroys elastic fibers in lungs & leads to emphysema
trapping of air in alveoli & reduced gas exchange

109. The time line for development of the respiratory system
6 – 16 weeks the basic structures are formed
16 – 26 weeks vascularization and the development of respiratory bronchioles, alveolar ducts and some alveoli begins
26 weeks to birth many more alveoli develop
By 26 – 28 weeks there is sufficient surfactant for survival.

110. Aging & the Respiratory System
Respiratory tissues & chest wall become more rigid
Vital capacity decreases to 35% by age 70.
Decreases in macrophage activity
Diminished ciliary action
Decrease in blood levels of O2
Result is an age-related susceptibility to pneumonia or bronchitis

111. Disorders of the Respiratory System
Asthma
Chronic obstructive pulmonary disease
Emphysema
Chronic bronchitis
Lung cancer
Pneumonia
Tuberculosis
Coryza and Influenza
Pulmonary Edema
Cystic fibrosis

112. Pneumothorax
Pleural cavities are sealed cavities not open to the outside
Injuries to the chest wall that let air enter the intrapleural space
causes a pneumothorax
collapsed lung on same side as injury
surface tension and recoil of elastic fibers causes the lung to collapse

113. DISORDERS OF THE RESPIRATORY SYSTEM
Asthma is characterized by the following: spasms of smooth muscle in bronchial tubes that result in partial or complete closure of air passageways; inflammation; inflated alveoli; and excess mucus production. A common triggering factor is allergy, but other factors include emotional upset, aspirin, exercise, and breathing cold air or cigarette smoke.
Chronic obstructive pulmonary disease (COPD) is a type of respiratory disorder characterized by chronic and recurrent obstruction of air flow, which increases airway resistance.
The principal types of COPD are emphysema and chronic bronchitis.
Bronchitis is an inflammation of the bronchial tubes, the main symptom of which is a productive (raising mucus or sputum) cough.

114. DISORDERS OF THE RESPIRATORY SYSTEM
In bronchogenic carcinoma (lung cancer), bronchial epithelial cells are replaced by cancer cells after constant irritation has disrupted the normal growth, division, and function of the epithelial cells. Airways are often blocked and metastasis is very common. It is most commonly associated with smoking.
Pneumonia is an acute infection of the alveoli. The most common cause in the pneumococcal bacteria but other microbes may be involved. Treatment involves antibiotics, bronchodilators, oxygen therapy, and chest physiotherapy.
Tuberculosis (TB) is an inflammation of pleurae and lungs produced by the organism Mycobacterium tuberculosis. It is communicable and destroys lung tissue, leaving nonfunctional fibrous tissue behind.
Coryza (common cold) is caused by viruses and usually is not accompanied by a fever, whereas influenza (flu) is usually accompanied by a fever greater than 101oF.

115. DISORDERS OF THE RESPIRATORY SYSTEM
Pulmonary edema refers to an abnormal accumulation of interstitial fluid in the interstitial spaces and alveoli of the lungs. It may be pulmonary or cardiac in origin.
Cystic fibrosis is an inherited disease of secretory epithelia that affects the respiratory passageways, pancreas, salivary glands, and sweat glands.
Asbestos related diseases develop as a result of inhaling asbestos particles. Diseases such as asbestosis, diffuse pleural thickening, and mesothelioma may result.
Sudden infant death syndrome (SIDS) is the sudden unexpected death of an apparently healthy infant. Peak incidence is ages two to four months. The exact cause is unknown.
Severe acute respiratory syndrome (SARS) is an emerging infectious disease.