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Chapter 14. Respiratory System

Higher category : 【Biology】 Biology Index 

1. Overview of Breathing

2. Lung Structure (Mammals)

3. Lung ventilation (mammals)

4. Gas transport of blood

5. Control of breathing

6. Acidosis and Alkalosis

7. Lung disease

1. Overview of Breathing

⑴ Stage of breathing

① Exhalation : Gas exchange between the atmosphere and the respiratory tract (ventilation)

② Diffusion : Gas exchange between respiratory tract and blood

③ Mass transport : Carrying of blood

④ Breathing : Gas exchange between blood and tissue cells

⑤ (Note) cell respiration : Receives O2 to oxidize organic matter and produces CO2 and ATP

⑵ Insect breathing : Direct air to the engine only

① Air flow : Institutions → Institutions → Air capillaries

○ 1^st. Atmospheric O2 flows into the trachea (the thickest air duct) through the gate on the side of the abdomen

○ 2^nd. Air entering the trachea is the trachea (a.K.a bronchiole)

○ 3^rd. Air pockets exist due to the presence of expanded sites near tissues with high oxygen demand

○ 4^th. O2 in the bronchus moves through the diffusion into the air capillary

② The shape of the organ is retained by the ring-shaped chitin

③ The end of the bronchus is filled with a dark blue liquid. → As the momentum increases, oxygen consumption increases, and most of this liquid is absorbed into the body fluid, which increases the volume of the bronchial tube containing air.

④ Diving Insect : Using Bubbles to Absorb Oxygen

⑶ Fish breathing : Using gills as a respiratory tract

① Located on both sides of the fish

② Four gill bows located between the mouth and the gill lids

③ Hundreds of gill filaments, lamellar up and down

○ Lamella : Practical gas exchange surface

④ Blood vessels passing through the gill : Afferent vessels, centrifugal vessels

○ Afferent blood vessels : Carries blood to the gills

○ Efferent vessels : Withdrawing blood from gills

⑤ Increased gas exchange efficiency by ventilation and backflow exchange

○ Backflow Exchange : Blood flow inside the lamellae and water flow in opposite directions

⑷ Amphibian breathing

① Using gills during larval period, then lungs when adult

○ Reptiles, birds and mammals breathe using their lungs

② Ventilate with positive pressure breathing

○ Breathe positively : Breathing, swallowing air, increasing the pressure near the breathing surface to allow oxygen in the air to dissolve in capillaries across the breathing surface

○ Breathing negative pressure. mammalia) : A breath that lowers the pressure near the breathing surface so that oxygen in the air dissolves in capillaries that cross the breathing surface.

③ Skin respiration : 50% of gas exchanges through the skin

⑸ Bird breathing

① Envelope : Lungs and space inside some bones

② flow of air : Trachea → Bronchus → Lateral Bronchus → Air Capillary, two inhales and exhalations

○ Back air bag → Lung → Front air bag

○ 1^st. First breath : Air fills the rear pockets

○ 2^nd. First exhalation : The back airbag contracts and sends air to the lungs

○ 3^rd. Second inhale : Air flows out of the lungs into the front airbag

○ 4^th. Second exhalation : The anterior lung contracts and releases the air that entered the body by the first inhale

③ Advantages of bird breathing

○ Algae lungs are not blocked at the end → residual amount × → gas exchange efficiency ↑

○ Less contraction and relaxation than mammals

⑹ Mammal Breathing (See. 2, 3)

2. Lung Structure (Mammals)

⑴ Air flow : Mouth or nose → nasal cavity → pharynx → larynx → airway → bronchus → tracheobronchial (bronchial) → alveoli

① Air is filtered, warmed and humidified through the nasal passages

② Air from the nasal passages moves to the pharynx (inlet of the esophagus and larynx), where it meets food from the mouth.

③ Palate reflection

○ When swallowing food

○ Epiglottis : Structures that send food to the esophagus and air to the airways

○ 1^st. The larynx moves up to close the epiglottis at the gate that corresponds to the entrance to the prayer

○ 2^nd. Food goes down the esophagus and reaches over

○ Rest time : Prayer can open and breathe

○ Sends foreign substances trapped in the mucus of goblet cell to esophagus

④ vocal cords

○ The larynx and the lining of the airways (the role of the vocal cords) are fortified with cartilage to ensure airways at all times

○ High tone when strong contraction of vocal cord muscles, low tone when weak contraction

⑤ Bronchus : 2, the inner wall epithelial cells of the main bronchus pass the foreign body to the esophagus using cilia and mucus

⑵ Anatomy of the lungs

① The lungs are made of light spongy tissue, mostly filled with air-filled spaces

② Each lung is surrounded by a pleural sac that prevents gas exchange with the chest cavity

⑶ Alveoli

① 400 million, monolayer epithelium, diameter 0.1 to 0.3 mm

② Alveoli-capillary spacing : 0.1 to 1.5 μm for very smooth diffusion

③ Special structure of alveoli causes lung elasticity

○ The alveoli are muscleless (disrupting gas exchange) but the connective tissue contains large amounts of elastin, which allows it to contract and relax

○ Elastin fibers : Has elastic force opposite to tension

○ Moisture tension : Microscopic layers of moisture on alveoli attract each other to create strong contractile pressure

④ Types of Alveolar Cells

○ First alveolar cell : Mostly epithelial cells

○ Second alveolar cell : Secretion of surfactant on the surface of villi → Alveolar distortion due to surface tension of water

○ Smaller alveolar second alveolar cells secrete more surfactant to lower higher surface tension

○ Neonatal Respiratory Disorder Syndrome (NRDS) : Lack of surfactant secretion due to premature death of infants, second stage alveolar cells

○ Macrophage : Foreign object removal

⑤ Number of alveoli 8 × 10⁶ → Respiratory epithelium area 50 ~ 100 m² (See. Body surface area ~ 2 m²)

⑷ Functional structure of the lungs

① Lung blood : 0.5 L (10-12% of total blood)

② Volume of the lungs : 3 L

③ Mammals and fish have a larger respiratory surface area at higher weights

④ Oxygen respiration in mammals is proportional to alveolar surface area

⑤ Obesity : Lack of respiratory area → limited oxygen supply → decreased activity

3. Lung ventilation (mammals)

⑴ Breathing pressure : Consumes 3-5% of total energy

① The lungs are passively ventilated with diaphragm and intercostal contractions connected to the pleura

○ The lungs themselves have no muscles and cannot actively contract

○ Thoracic cavity : The lungs are floating in the chest cavity and the chest cavity is a closed space

○ Pleura : Comprised of proximal and pleural pleura, pleural effusion in interstitial space (3-4 mL)

○ Pneumothorax : Perforation of the pleura due to infection or cuts

○ Gang : Thin space surrounding the lungs

○ Contractions of the diaphragm and intercostal muscles are transmitted to the lungs through the pleural effusion so that the lungs are passive contractions

○ Lung flexibility : More surfactant, less scar tissue increases lung flexibility

② Inspiration (Inhalation) : Rib rise (external intercostal contraction), diaphragm descend (diaphragm contraction) → thoracic expansion → pressure drop → air inflow

③ Exhalation : Rib lowering (intercostal contraction), diaphragm rise (diaphragm relaxation) → thoracic contraction → pressure rise → air release

○ Less consumption of ATP during the exhalation process due to gravity and lung elasticity

④ Alveolar pressure, intrathoracic pressure change during breathing

○ Point 1. The pleural intraluminal pressure should be less than the alveolar pressure because the human body regulates the pleural cavity pressure to control the alveolar pressure

○ Point 2. The lungs show a wave graph because the air flows in when the pressure is lowered to offset the change.

○ Volumetric-pressure curve of the lung (link : / 1464) : When inflating requires more pressure than when contracting

⑤ Disadvantages : Partial Pressure Slope Reduction, Backflow Gas Exchange ×

○ Due to the large amount of oxygen in the atmosphere, the disadvantages do not significantly affect species survival

⑵ Spirometry curve

① Parameter

○ Inspiratory residual volume

○ Expiratory residual volume

○ Residual volume

○ Spirometry = 1 tidal volume + absorbent reserve + phagocytic reserve

○ Total lung volume = 1 breath volume + absorbent reserve amount + eosinophilic reserve amount + residue amount

○ Intake volume = tidal volume + absorbent reserve

○ Functional residue amount = phagocytic reserve amount + residue amount

② Gas exchange at rest

○ Tidal volume : 500 mL

○ Ventilation rate : Respiratory Rate Per Minute. Typically 8-12 times per minute

○ Total waste ventilation : Ventilation rate × tidal volume = 8 × 500 mL / min to 12 × 500 mL / min = 3 to 6 L / min

○ Inspiration : Nitrogen 78%, Oxygen 21%, Carbon Dioxide 0.3%

○ Exhalation : Nitrogen 78%, Oxygen 17%, Carbon Dioxide 4%

○ 250 mL O² / min influx into the blood → 360 to 600 L / day O²

○ 200 mL CO² / min discharge into the lungs

○ Alveolar ventilation increased more than 20 times during exercise, alveoli blood flow increased 5-6 times

③ Dead space

○ Amount that does not contribute to gas exchange at one breath

○ Cause : Trachea from trachea to bronchioles lack respiratory epithelium and fail to participate in gas exchange

○ Degree : The anatomical dead space is about 140 mL, but the physiological dead space is about 150 mL, given that the bronchial dilated upon inspiration.

○ Alveolar ventilation volume (the amount of air reaching the alveoli) = ventilation rate (breath rate per minute) × (1 breath volume-dead space)

④ Ventilation volume and partial pressure of gas in the alveoli

○ Acidosis, Alkalosis General (See. 6)

○ Ventilation volume ↑ → CO2 release ↑ → respiratory alkalosis

○ Ventilation volume ↓ → CO2 in plasma ↑ → respiratory acidosis

⑶ Transpulmonary Pressure-Volume Graph

① Compliance 

○ The degree to which the volume changes with pressure change

○ More surfactant increases the extension

② Inspiration : Confrontation between force to inflate alveoli and surface tension

○ Graphs that don’t seem to increase in volume

○ When treating surfactant : Reduced surface tension → Easy alveolar expansion → Moving graph in the direction of increasing volume

③ Exhalation : Strength of alveoli and surface tension strengthen each other

○ A graph that seems to increase in volume

○ When treating surfactant : Decrease in surface tension → negative alveolar contraction → move graph in the direction of increasing volume

4. Gas transport of blood

⑴ Breathing pigment : Special proteins that carry oxygen

① Hemocyanin : Breathing pigments of arthropods and molluscs, blue (including Cu)

② Hemoglobin : Breathing pigments of most vertebrates and invertebrates, red (including Fe)

③ Myoglobin : More oxygen affinity than hemoglobin, red (including Fe)

○ Diving mammals, heart and muscles are high in myoglobin

○ Myoglobin cannot enter the blood

⑵ Oxygen transport

① Function of hemoglobin : Oxygen transport

○ One red blood cell contains 250 million Hb → carries 1 billion molecules of oxygen (99%)

○ 198 mL / L of 200 mL / L of total blood oxygen

○ Less than 1% oxygen dissolved in plasma or red blood cell substrate

○ Respiratory pigment has higher saturation with higher oxygen partial pressure

○ Hemoglobin binds to oxygen in the lungs (100% saturation) and dissociates only about 30 to 40% at the tissue ends

② Structure : Allosteric enzyme, α2 β2 (quaternary structure, HbA), each unit consisting of heme and globin

○ Myoglobin only consists of tertiary structure

○ Heme : It has an organic ring structure called porphyrin, with Fe2+ in the center

○ Fetus : HbF (Hb Fetus) is present

○ Embryo ~ 8 weeks : ζ2 ε2 

○ About 6 weeks pregnant, HbF begins to be produced in the liver

○ Around 8 months of pregnancy, HbA begins to form in the bone marrow

○ In newborns, 70% are HbF and 30% are HbA

○ Rapid HbA (Hb Adult) replacement between 3 and 6 months after birth (HbF destruction)

○ Oxygen affinity : α2 γ2 > α2 β2

○ Oxygen released from maternal hemoglobin binds to fetal hemoglobin

○ Cause : BPG binding site sequence difference, γ chain of HbF and β chain of HbA differ about 38% in amino acid sequence

○ BPG affinity : γ chain β chain (See. 4-⑶-④)

○ HbA₂ : About 2% of hemoglobin in adults (98% is HbA), α₂δ₂

○ See : Hemocyanin is a respiratory pigment with copper, not iron, found in arthropods and molluscs a lot.

③ Ligands that bind to Hb’s heme (competitive inhibition of oxygen)

○ oxy Hb : Hb + O₂ → HbO₂(red)

○ saturated oxy HB : Hb + 4O₂ → Hb(O₂)₄

○ reduced Hb : Hb + H⁺ → HHb (reddish brown)

○ met Hb : OH^- (Fe³⁺) occurs occasionally, but resolves itself in vivo

○ carboxy Hb : CO (affinity ) causes carbon monoxide poisoning

○ cyano Hb : Causes of death of CN^- (affinity ) and cyanide (KCN)

○ (Note) Carbon dioxide and 2,3-BPG bind to globin and do not act as an inhibitor, but lower red blood cell oxygen transport ability.

④ Cooperative : In the fourth structure, when the substrate is bound to one monomer, the affinity of the substrate of the surrounding monomer increases.

○ Myoglobin forms the shape (MM type) expected by the Michaelis-Menten equation because of the constant affinity of the substrate.

○ Myoglobin is not an allosteric protein such as hemoglobin

○ Myoglobin has higher oxygen affinity than hemoglobin, so oxygen storage at low oxygen partial pressure; The presence of multiple myocytes

○ Seals, which are submersible mammals, store about twice as much oxygen per kilogram of body weight as myoglobin ↑.

○ Hemoglobin shows the sigmoid type (S-shape) because the affinity of the substrate is gradually increased

○ Hemoglobin is an allosteric protein to which two or more ligands can bind

○ Even if only one oxygen molecule is bound to hemoglobin, the subunit becomes a structure with high affinity with oxygen

○ Conversely, only one oxygen molecule escapes from saturated hemoglobin, resulting in a low oxygen affinity.

○ Stability : Oxygen carrying capacity is greatly reduced even when the partial pressure of oxygen in alveoli and arterial blood reaches 100 mmHg to 60 mmHg ×

⑶ Bore effect : Oxygen Affinity Change of Hemoglobin by Four Factors (pH, pCO2, Temperature, 2,3-BPG)

① H⁺ effect

○ [H⁺] ↑ → pH ↓ → Changes in ionic bonds in Hb (eg histidine of β chain) → Hb conformation change → oxygen affinity ↓

○ Oxygen and dissociated hemoglobin combine with hydrogen ions to prevent acidification of blood

○ Ion Bond Change 1 : -COOH ↔ -COO- + H⁺ (Place : Globin)

○ Ion Bond Change 2 : -NH2 + H+ ↔ -NH3+ (Location : Globin)

○ Oxygen affinity change during exercise 1 : PH ↓ → oxygen affinity ↓ due to lactic acid and fatty acid production

② CO₂ effect

○ CO₂ ↑ → CO₂ binding or acid increase at N-terminus → Hb conformational change → oxygen affinity ↓

○ CO_{2 bonding at the N-terminus} 

○ Acid increase : If pCO₂ is high, pH is reduced to H + derived from carbonic acid.

○ Reduced oxygen affinity allows hemoglobin to dissociate oxygen better in tissue cells

③ Temperature effect

○ Temperature ↑ → Hb conformation change → Oxygen affinity ↓

○ Actively metabolizing or exercising cells release heat

○ Enzymes rapidly lose their activity as their intramolecular bonds weaken at temperatures after their activation temperature

④ 2,3-BPG (2,3-bisphosphoglycerate) effect

○ 2,3-BPG : Active production of glycolysis, isomer of 1,3-BPG, an intermediate product of glycolysis

○ Mammalian erythrocytes have high concentrations of 2,3-BPG

○ 2,3-BPG ↑ → Stabilizes deoxyhemoglobin by combining with β globin in the middle of hemoglobin → additional oxygen affinity ↓

○ Oxygen affinity change during exercise 2 : Tissue cell oxygen debt phenomenon → Some G3Ps convert to 2,3-BPG → Oxygen bond in β globin ↓

⑤ When moving to a high altitude mountain

○ 1^st. Reduction of partial pressure of oxygen in the atmosphere

○ 2^nd. Decreases the amount of oxygen binding of hemoglobin in the lungs

○ Increase respiratory rate to compensate for insufficient oxygen binding

○ Respiratory algorithm : Increasing respiratory rate releases excess CO2, increasing blood pH

○ 3^rd. Decreased oxygen supply to tissue cells → Increased 2,3-BPG in red blood cells

○ Reduced oxygen affinity of hemoglobin releases more oxygen from oxygen hemoglobin

○ 4^th. Reduced oxygen supply to the kidneys

○ 4^th-1^st. Increased erythropoietin secretion in the kidneys

○ 4^th-2^nd. Promote red blood cell production in bone marrow → increase red blood cell count

⑷ Carbon dioxide transport

① Plasma : 8%, simple diffusion (melting)

○ CO₂ (g) → CO₂ (aq)

② Combined with hemoglobin : HbCO₂, about 22%

③ Bicarbonate ion : HCO₃^-, about 70%

○ 1^st. CO₂ (aq) simply diffuses from plasma to red blood cells

○ 2^nd. Promoted by CO₂ (aq) + H₂O (l) → H₂CO₃ (aq), carbonic anhydrase (CA)

○ 3^rd. H₂CO₃ → H+ + HCO₃^-

○ 4^th. H⁺ combines with Hb to become HHb (See. ⑶-①)

○ 5^th. HCO₃^- is one-to-one reverse cotransport with Cl^- and discharged out of plasma

○ 6^th. Osmotic pressure causes water to enter as Cl^- increases in erythrocytes → volume increases

⑸ Pulmonary and body circulation : Circulation and respiratory system harmony

① Pulmonary Circulation (12% Blood Retention)

○ Right ventricle → Pulmonary artery → Pulmonary capillary → Pulmonary vein → Left atrium

○ Blood with O₂↓, CO₂↑ → Blood with O₂↑, CO₂↓

② Circulation (79% blood retention)

○ Left ventricle → aorta → artery → capillary → vein → vena cava → right atrium

○ Blood with O₂↑, CO₂↓ → Blood with O₂↓, CO_2</sub↑

○ Aortic partial pressure : 80 to 100 mmHg

○ Venous oxygen partial pressure : 40 mmHg

○ Supply nutrients and oxygen to tissue cells

5. Control of breathing

⑴ Control of number : Cortex → Cortex spinal cord → Motor neurons

⑵ Self-regulating central : Pontoon, training → voluntary, rhythmic activity

① Soft water : Basic breathing control

○ Soft water is more affected by carbon dioxide than oxygen

② Pons : Adjusts for smooth transition between inspiration and exhalation, breathing rate

③ Input and receiver

○ Chemical receptors in the central nervous system (especially cerebrospinal fluid) (pO₂, pCO₂, H⁺)

○ H⁺ cannot cross the brain-vascular barrier so chemical receptors determine H⁺ by the amount of CO₂

○ Increase metabolism through exercise → CO₂ ↑ → Increase respiration → Excessive CO₂ emissions → Normalize pH

○ Input of chemical receptors (H⁺, pO₂, pCO₂) of aortic bodies (next to the aortic arch) and carotid bodies (next to the carotid artery)

○ O₂ concentration does not have a significant effect on breathing, but increases respiration rate when O₂ levels are low

○ Plasma epinephrine and potassium concentration receptors

○ Muscle and joint kidney receptor input

○ Renal Receptor Input to Lung

○ Stimulation (temperature, etc.) input through other receptors and under Thalamus

④ Breathing control process

○ Breathing exercise : Sympathetic stimulation, adrenaline secretion

○ Respiratory movement suppression : Parasympathetic stimulation, acetylcholine secretion

6. Acidosis and Alkalosis

⑴ Steady state

① PH : 7.41 to 7.45

② O₂ : 40 mmHg (tissue) or more 100 mmHg (lung) or less

③ CO₂ : 40 mmHg (lung) or more 46 mmHg (tissue) or less

④ HCO₃^- : 24 mmEqmol

⑵ Acidosis and Alkalosis

① Acidosis : pH 7.35 or less

② Alkalosis : pH 7.45 or more

⑶ Metabolic alkalosis : Metabolism Excessive HCO3-

① Excess HCO₃^- reacts with H⁺ resulting in high pH

② Compensation : Increased partial pressure of CO₂ by lowering breathing rate to lower pH

③ Example : Vomiting (exhaust acid from the stomach)

⑷ Metabolic acidosis : If HCO₃^- is low due to metabolism

① Less HCO₃sup>-</sup>, H⁺ remains in the blood, resulting in lower pH

② Compensation : Lowers CO₂ partial pressure by increasing respiration rate to increase pH

③ Example : Diarrhea (Bicarbonate Release)

⑸ Respiratory alkalosis : When the partial pressure of CO2 is lowered in relation to breathing

① Lower CO₂ partial pressure results in higher blood pH

② Compensation : Suppresses HCO₃^-reaction to lower pH

③ Example : Hyperventilation, limited lung disease (e.g., Pulmonary fibrosis)

⑹ Respiratory acidosis : High CO₂ partial pressure associated with respiration

① Low CO₂ pH due to no CO₂ emissions

② Compensation : Activate HCO₃<sup-</sup> reaction to increase pH

③ Example : Obstructive pulmonary disease (e.g., asthma)

7. Lung disease

⑴ Tobacco hazards : 100,000 chemicals, 20 species Class A carcinogens, tar, carbon monoxide, nicotine are the most hazardous substances

① Tar (tobacco, less than 10 mg) : Including 40 kinds of carcinogens, perturbing blood, destroying cells, causing chronic inflammation, disturbed immune system, cilia (ex. Elastin) damage

② carbon monoxide : Incomplete combustion products, most substances in cigarette smoke, the main causes of chronic hypoxia, premature aging, arteriosclerosis

③ Nicotine (one open 0.1 to 0.6 mg) : 7 seconds reach brain, addictive, narcotic, insecticide, herbicide, blood pressure rise

④ Benzopyrene, dimethylnitrosamine : Carcinogen

⑤ Cyanide : Death Gas Poison

⑥ Niphthylamine : Antiseptic

⑦ Naphthalene : Mothballs

⑧ DDT : Pesticide

⑵ Chronic obstructive pulmonary disease (COPD)

① Symptom : Ventilation disorders caused by narrowing the airways and increasing resistance to air flow

② Characteristic : Total lung capacity and residues are higher than normal (compensation), respiratory function usually lower than normal

③ Example 1. Chronic bronchitis : Bronchial mucus hypersecretion → chronic inflammation of the lower airways

④ Example 2. Bronchial asthma : Allergic reactions, viral infections, alveolar contractions, increased mucus secretion, increased airway resistance in the airways, chronic inflammation, particulates exacerbate asthma

⑤ Example 3. Emphysema : Causes of wound tissue formation due to bronchitis and asthma, small airway destruction and obstruction reduce alveoli and surface area, inability to regenerate

⑶ Restrictive Lung Disease

① Symptom : Ventilation disorders caused by decreased lung extension (compliance, compliance)

② Characteristic : Total lung capacity and residues are less than normal, performing a respiratory function equivalent to normal in a limited range

③ Example 1. Pulmonary fibrosis

③ Example 2. Pneumoconiosis, tuberculosis

④ Example 3. Occupational lung disease

○ Asbestos, coal dust, silicon, paper dust, pollen, etc., accumulate in macrophages that remove it

○ Increased scar tissue → Fibrous tissue sutures wounds instead of lung tissue → Fibrocystic cysts and lung flexibility decreases

⑷ Lung cancer

① It contains a burning carcinogen of tobacco smoke

② Particulates, such as tar, remain on the lung surface for a long time causing mutations and cancer

⑸ Pulmonary edema (pulmonary edema)

① Moisture in the pulmonary vein due to excess lymph retrieval capacity (pulmonary capillary tissue fluid) leaves the alveoli and pools into water → difficulty breathing

② Cause : Heart failure increases blood pressure in pulmonary veins, lowers external pressure

Input : 2015.7.19 11:19