Respiratory System

v  Major Functions

v  Gas exchange (external and internal exchange)

v  Cleanse/Moisten/Warm Air

v  Inspiration and expiration move air in and out of the lungs during breathing.

v  Cellular respiration is the final destination where ATP is produced in cells.

Introduction

The respiratory tract

The Nose v  The two nasal cavities are divided by a septum.

v  They contain olfactory cells, receive tear ducts from eyes, and communicate with sinuses.

v  The nasal cavities empty into the nasopharynx.

v  Auditory tubes lead from the middle ears to the nasopharynx.

The path of air

The Pharynx v  The pharynx (throat) is a passageway from the nasal

cavities to oral cavities and to the larynx.

v  The pharynx contains the tonsils; the respiratory tract assists the immune system in maintaining homeostasis.

v  The pharynx takes air from the nose to the larynx and takes food from the oral cavity to the esophagus.

The Larynx v  The larynx is a cartilaginous structure lying between the

pharynx and the trachea.

v  The larynx houses the vocal cords.

v  A flap of tissue called the epiglottis covers the glottis, an opening to the larynx.

v  In young men, rapid growth of the larynx and vocal cords changes the voice.

Placement of the vocal cords

15-8

The Trachea

v  The trachea, supported by C-shaped cartilaginous rings, is lined by ciliated cells, which sweep impurities up toward the pharynx.

v  Smoking destroys the cilia.

v  The trachea takes air to the bronchial tree.

v  Blockage of the trachea requires an operation called a tracheostomy to form an opening.

Cilia in the trachea

15-10

The Bronchial Tree v  The trachea divides into right and left primary bronchi

which lead into the right and left lungs.

v  The right and left primary bronchi divide into ever smaller bronchioles to conduct air to the alveoli.

v  An asthma attack occurs when smooth muscles in the bronchioles constrict and cause wheezing.

The Lungs v  Lungs are paired, cone-shaped organs that lie on either

side of the heart and within the thoracic cavity.

v  The right lung has three lobes, and the left lung has two lobes, allowing for the space occupied by the heart.

v  The lungs are bounded by the ribs and diaphragm.

The Alveoli v  Alveoli are the tiny air sacs of the lungs made up of

squamous epithelium and surrounded by blood capillaries.

v  Alveoli function in gas exchange, oxygen diffusing into the bloodstream and carbon dioxide diffusing out.

v  Infant respiratory distress syndrome occurs in premature infants where underdeveloped lungs lack surfactant (thin film of lipoprotein) and collapse.

Gas exchange in the lungs

v  During breathing, air moves into the lungs during inspiration (inhalation) from the nose or mouth, then moves out again during expiration (exhalation).

v  A spirometer allows measurement of the components of air during breathing.

Mechanism of Breathing

Respiratory Volumes v  Tidal volume (VT) the normal amount of air

moved in and out of the lungs when relaxed, is usually 500 ml.

v  Inspiratory reserve volume is the maximum amount of forcibly inspired air.

v  Expiratory reserve volume is the maximum amount of forcibly expired air.

v  Vital capacity is the maximum amount of air moved in and out on deep breathing, and is the sum of tidal, inspiratory reserve, and expiratory reserve volumes.

v  Air that remains in the lungs is residual volume.

Vital capacity

Inspiration and Expiration v  There is a continuous column of air from the pharynx to

the alveoli, and the lungs lie within the sealed-off thoracic cavity.

v  The thoracic cavity is bounded by the rib cage and diaphragm.

v  Pleural membranes line the thoracic cavity and lungs and the intrapleural pressure is lower than atmospheric pressure, keeping the lobules of the lungs from collapsing.

v  Minute Ventilation – The volume of inhaled and exhaled air in one minute.

Inspiration

v  When we inhale (inspiration) impulses from the respiratory center in the medulla oblongata cause the rib cage to rise and the diaphragm to lower, causing the thoracic cavity to expand.

v  The negative pressure or partial vacuum in the alveoli causes the air to come in.

v  Changing amounts of blood of H+ and CO2 detected by chemoreceptors in the carotid arteries and aorta increase breathing rate.

O2 UPTAKE DURING EXERCISE

v  VO2 - measured in ml/Kg/min

v  VO2max - maximal oxygen uptake

v  Metabolic Cart

v  Predicted VO2max testing

v  Astrand 6 min. test

v  Balke Test

Nervous control of breathing

Inspiration

Expiration v  When we exhale (expiration), lack of impulses from the

respiratory center allow the rib cage to lower and the diaphragm to resume a dome shape.

v  Expiration is passive, while inspiration is active.

v  The elastic recoil of the lungs causes expiration (gravity).

v  A deep breath causes alveoli to stretch; stretch receptors then inhibit the respiratory center via the vagus nerve.

Expiration

Expiration: active

v  Under extreme conditions, exhalation becomes dynamic.

v  Internal intercostal muscles contract forcing the ribs down and inward.

v  Tightening of the abdominal walls also pushes on the viscera which pushes the diaphragm and forces out even more air.

v  FEV1 – the amount of air forcibly expired in one second. Reduced in patients with COPD

Spirometry

v  External Respiration

v  Individual gases exert pressure proportional to their portion of the total in a mixture of gases; this is called “partial pressure” (PO2). (Air - 21% O2, 0.04% CO2)

v  External respiration is the diffusion of CO2 from pulmonary capillaries into alveolar sacs and O2 from alveolar sacs into pulmonary capillaries.

v  Most CO2 is carried as bicarbonate ions.

v  The enzyme carbonic anhydrase, in red blood cells, speeds up the conversion of bicarbonate and H+ to H2O and CO2; CO2 enters alveoli and is exhaled.

Gas Exchange

Partial Pressures

Hemoglobin Structure

v Hemoglobin (Hb) takes up oxygen from alveoli and becomes oxyhemoglobin (HbO2).

v 4 globular proteins (globin) & 4 heme units.

v (64 000 daltons)

Internal Respiration v  Internal respiration is the diffusion of O2 from systemic

capillaries into tissues and CO2 from tissue fluid into systemic capillaries.

v  Oxyhemoglobin gives up O2, which diffuses out of the blood and into the tissues because the partial pressure of O2 of tissues fluid is lower than that of the blood.

v  After CO2 diffuses from tissue cells into the blood, it enters red blood cells where a small amount is taken up by hemoglobin, forming carbaminohemoglobin.

Internal Respiration Cont. v  Most of the CO2 combines with water to form

carbonic acid (H2CO3), which dissociates to release hydrogen ions (H+) and bicarbonate ions (HCO3

-); the enzyme carbonic anhydrase speeds this reaction.

v  The globin portion of hemoglobin combines with excess hydrogen ions to become reduced hemoglobin or HHb; this helps maintain a normal blood pH.

v  Blood leaving capillaries is a dark maroon color because red blood cells contain reduced hemoglobin.

External and Internal Respiration

External and Internal Respiration

External

v  Hb + O2 à HbO2

v  HbCO2 à Hb + CO2

v  H+ + HCO3- à H2CO3

à CO2 + H2O

Internal

v  HbO2 à Hb + O2

v  CO2 + H2O à H2CO3 à H+ + HCO3

-

v  Hb + CO2 à HbCO2

v  H+ + Hb à HHb

v  HCO3- dissolves in

plasma

Chemical Equation Summary

Respiratory Centre •  located in the medulla oblongata

•  stimulated by the presence of CO2 and H+ ions.

•  neurons send automatic rhythmic discharge that triggers breathing

•  the signals travel to the diaphragm and the intercostal muscles via the phrenic nerve.

v  Low O2 in blood registered by carotid and aortic bodies

v  Communication with respiratory centre

v  Increase in minute ventilation occurs

v  Hemoglobin has 200X affinity for CO than O2

Respiratory Centre Cont.

Hemoglobin Saturation (SO2)

v  Lungs: 98-100% saturated

v  Tissues: 60-70% saturated

v  Conditions affecting Saturation:

v  Partial Pressure of O2 – incr. é SO2

v  pH – incr. pH é SO2

v  Temperature – incr. temp ê SO2

v  Exercise – increases temperature and decreases pH causing a decrease in arterial oxygen saturation (SaO2)

Oxyhaemoglobin Dissociation Curve

v  Common Respiratory System Diseases:

v  Asthma

v  COPD

v  Chronic Bronchitis

v  Emphysema

v  Pleurisy

v  Cancer

v  Influenza

v  Sinusitis

Respiration and Health

Sites of upper respiratory infections

Sinusitis v  Sinusitis is infection of the cranial sinuses within the

facial skeleton that drain into nasal cavities.

v  It occurs when nasal congestion blocks the sinus openings and is relieved when drainage is restored.

v  Pain and tenderness over the lower forehead and cheeks, and toothache, accompany this condition.

Lower respiratory tract disorders

COPD Chronic Bronchitis

v  Long-term cough with mucus

Emphysema

v  A breakdown of the alveoli walls.

Causes, Risk Factors, Symptoms v  Smoking

v  Exposure to gases and fumes, cooking fire

v  Cough, Fatigue, many R.T.I, Wheezing

Asthma v  Muscle lining small airways becomes irritated

v  Causes a narrowing of airway passages

v  Steroids or bronchodilators can be used to prevent constriction

Lung Cancer v  Lung cancer follows this sequence of events: thickening of

airway cells, loss of cilia on the lining, cells with atypical nuclei, tumor development, and finally metastasis.

v  Removal of a lobe or lung, called pneumonectomy, may remove the cancer.

v  Smoking, whether active or passive, is a major cause of lung cancer.

Normal lung versus cancerous lung

15-47

Chapter Summary v  Air passes through a series of tubes before gas exchange

takes place across an extensive moist surface in the alveoli of the lungs.

v  Respiration comprises breathing, external and internal respiration, and cellular respiration.

v  During inspiration, the pressure in the lungs decreases and air comes rushing in; during expiration, increased pressure in the thoracic cavity causes air to leave the lungs.

Chapter Summary Cont. v  External respiration occurs in the lungs where oxygen

diffuses into the blood and carbon dioxide diffuses out of the blood.

v  Internal respiration occurs in the tissues where oxygen diffuses out of the blood into tissue cells and carbon dioxide diffuses into the blood.

v  Spirometry is the measurement of lung capacities and can be used to diagnose certain respiratory conditions such as COPD.

Chapter Summary Cont. v  The respiratory pigment hemoglobin transports

oxygen from the lungs to the tissues and aids in the transport of carbon dioxide from the tissues to the lungs.

v  Hemoglobin’s oxygen affinity is affected by pH, temp and PO2

v  The respiratory tract is especially subject to disease because it is exposed to infectious agents; also, cigarette smoking contributes to two major lung disorders—emphysema and cancer.