Patho Chap 16Respiration PDF

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Chap 16 Notes on Respiration...

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Patho Chapter 16 – Respiration Respiration = Respiration has 3 functions. One function is Ventilation ( a mechanical process that moves air into and out of the lung). The second function is Gas Exchange (between lungs and the blood, and blood to the tissue). The last function is Oxygen Utilization (Cellular Respiration involving Oxygen and ATP). There are two types of Respiration

a) External Respiration = Ventilation and Gas exchange within the lungs. b) Internal Respiration = Gas Exchange from the blood to the tissues of cells. Movement of Gas = Gas exchange within the lungs is due to movement of gas from a high to low concentration by diffusion. Oxygen (O2) Concentration = O2 (lungs) > O2 (blood coming in). Oxygen diffuses from lungs to the blood. Carbon Dioxide (CO2) = CO2 (lungs) < CO2 (blood)

Anatomy of Respiratory System = The respiratory system contains two zones, the conduction zone and the respiratory zone. a) Conduction zone = involved with getting air from the mouth and nose to where the gas exchange will occur. Its made up of the nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles; their function is to filter, warm, and moisten air and conduct it into the lungs. b) Respiratory zone = the site of O2 and CO2 exchange with the blood. The respiratory bronchioles and the alveolar ducts are responsible for 10% of the gas exchange. The alveoli are responsible for the other 90%. Key Components 

Alveoli = air sacs that are in the lungs where gas exchange occurs. It’s a single cellular layer. Has huge surface are (about 760ftsq). Alveoli cluster together. The surfaces facing the air are lined by an epithelium made of two types of cells, type I and type II alveolar cells (pneumocytes). Type I (gas exchange and makes up 95% of alveole) / Type II (secretes pulomanary surfactancts. Involved with reuptake of sodium and water helping to prevent fluid build up.

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Pathway of Air = Air enters through mouth and nose (nasal cavity)  Pharynx  Larynx (vocal chords and glottis)  Trachea  Pulmonary Primary Bronchi  Secondary Bronchi  Tertiary Bronchi  Terminal Bronchi (pulmonary bronchioles)  Respiratory Bronchioles  Terminal alveolar sacs (Site of gas exchange).

Lungs = The lungs are contained within Thoracic Cavity along with the heart, trachea, esophagus, thymus. Structures inside lungs   

Parietal pleura = attached to inside of thoracic wall Visceral pleura = next to parietal. Connected to lung wall. Intraplueral space = thin film of liquid resides here

Role of Diaphram in Ventilation = At the bottom of the thoracic cavity is the diaphragm (a muscle). Below the diaphragm is the abdominal cavity. 

In Ventilation = air moves from higher to lower pressure known as the pressure difference between two areas of the conduction zone due to changes in the lung volume. The pressure difference allows us to inspire or expire air. The pressure difference is generally around 3mmHg. a) Inspiration (Inhalation) = a process of bringing air in. This happens because the intrapulmonary or intra-alveolar pressure is less than atmospheric pressure. Air is brought in when the diaphragm contracts, moving the ribs upward (by intercostal muscles). When this happens, after air is brought in, the volume of the lungs increases which decreases the intrapulmonary pressure. Change in pressure is due to changes in lung volume. So when lung volume increases, pressure decreases. Vice-versa. (Boyles law = pressure is inversely related to volume) b) Expiration = happens when intrapulmonary pressure is greater than atmospheric pressure. The diaphragm relaxes, moving the ribs downward, volume of the lung decreases and the intrapulmonary pressure increases leading to air flowing out.

Characteristics of Lungs and some relevant diseases 1) Compliance = this allows the lung to expand and change their volumes. 2) Elasticity = Recoiling from stretching allows for expiration 3) Surface Tension = Surface tension is modified by surfactants. Surfactants help decrease H-bonding between H20 molecules in the alveoli. Surfactants allow the small alveoli to stay inflated, allowing residual volume of air in the lungs.

RDS (Respiratory Distress Syndrome) = respiratory distress common in premature infants born six weeks or more before their due dates. It usually develops within the first 24 hours after birth. Symptoms include rapid, shallow breathing and a sharp pulling in of the chest below and between the ribs with each breath. Treatment includes corticosteroids to help with the maturing of lungs, breathing support, and oxygen therapy. Acute RDS = Condition in which fluid collects in the lungs' air sacs, reduces the effects of surfactants leading to the depriving organs of oxygen. People with ARDS have severe shortness of breath and often are unable to breathe on their own without support from a ventilator. Treatment includes oxygen, fluid management, and medication.

Spirometry = technique used to measure various lung volumes and capacities. Can be used to diagnose disorders.

Volumes of the Lungs a) Tidal Volume = amount of air expired or inspired. b) Expiratory reserve volume = extra amount of air you can expire out beyond normal expiration. c) Inspiratory reserve volume = extra amount of air you can bring in d) Residual volume = amount that in lungs that you can’t get out. Cannot change.

Capacity Factors a) Vital capacity = max amount of air that can be forcefully expired after maximal inspiration. b) Total lung capacity = amount of air/gas in the lungs after maximal inspiration c) Inspiratory Capacity = amount of gas that can be expired after normal inspiration. d) Functional Capacity = amount of gas left in lungs after normal expiration.

Diseases and Disease States = There are two major categories of diseases : Restrictive and Obstructive. 

Restrictive diseases = the lung tissue itself is damaged and there’s a decrease in vital capacity but forced expiratory volume is normal. Example : Emphysema, Pulmonary Fibrosis

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Obstructive diseases = lung tissue is normal, vital capacity is normal but forced expiratory volume is reduced. Example : Bronchial asthma

FEV-1 (Forced Expiratory Volumes) = most commonly used tests. Normal values based on age. If less than 80% of normal value there’s some sort of obstructive disease present.

1) Asthma = caused by inflammation, mucus secretions that interfere with gas exchange, constriction of bronchioles (histamine or other bronchiole constrictors), allergic immune repsonses. Sometimes it can be triggered by cold air, low humidity, aspirin, or exercise. Referred to sometimes as the hyper responsive airway. Symptoms = dyspnea (difficulty breathing), wheezing Treatments = bronchodilators like albuterol in inhalers, Beta-2 selective agonists. 2) Emphysema = destruction of alveoli (where gas exchange occurs) results in decrease of effectiveness of gas exchange due to decreased surface area. Caused by smoking, which triggers inflammation and destruction of alveoli. 3) COPD (Chronic Obstructive Pulmonary Disease) = Airways narrow and alveoli are damaged. Smoking allows fine particular matter to get to alveoli. Particles will damage alveoli and cause remodeling of blood vessels in the lungs. Can lead to pulmonary hypertension. Severe case is called Cor Pulmonale (right side heart failure. No cure for this). 4) Pulmonary Fibrosis = fibrous tissues accumulate in lungs and damage alveoli. Inhalation of small particles also leads to this. Example : minors exposed to dust from cold (black lung) Gas Exchange = we use barometer to measure pressure. At sea-level, atmospheric pressure is 760 TORR (1 atm). Daltons Law = Total pressure of gas mixtures is equal to the sum of the pressures of each gas. Partial Pressure

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In the pulmonary system, high concentration of Oxygen leads to dilation which allows better exchange of oxygen from the alveoli into blood to occur.

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In the systemic circulation, if theres low O2 concentration it leads to dilation because tissues are in need of oxygen.

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If there are increased partial pressures of some gas it could lead to certain disorders, such as in deep sea divers who develop oxygen toxicity because they are breathing at an increased atmospheric pressure of oxygen.

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Nitrogen Necrosis occurs when nitrogen is inhaled under elevated pressure causing dizziness.

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Decompression sickness = Nitrogen comes out of blood. Bubbles can cause stroke.

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Oxygen Concentration in arterial blood is a good measurement indicator of respiratory function.

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PO2 decreases at elevated heights. Control of Respiration

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Motor neurons located in the brain stem controls the relaxation and contraction of the diaphragm and the intercostal muscles.

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The brain stem includes the medulla oblongata and pons. Both are involved to regulate blood pressure and respiration. The brain stem controls involuntary breathing.

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The Cerebral cortex controls voluntary breathing and allows us to contract the diaphragm and intercostal muscles consciously.

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In the Medulla, there are centers that control rhythmicity

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Pons influences the medulla and promotes inspiration (apneustic center)

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The Pneumotaxic center inhibits inspiration. Chemoreceptors monitor pH and CO2 and O2.

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Increase in CO2 will be a stimulation of breathing.

Last of Respiratory System

Loading = the process by which hemoglobin binds oxygen to form oxyhemoglobin in the lungs. Unloading = the process by which oxyhemoglobin, once in the metabolizing tissues, is unloaded as oxygen is released and diffuses into the plasma and ultimately into our cells. The direction in which oxygen binds with deoxygenated hemoglobin is dependent on the partial pressure of oxygen. Partial pressure of oxygen is related to concentration of oxygen. Oxygen moves from high to low. High PO2 = favors loading. Strong bond between hemoglobin and oxygen also favors loading. Systemic Arteries = rich with oxygen. PO2 = 100mmHg (or Torr) leads to 97% oxyHb. Systemic Veins = PO2 = 40mmHg. Leads to 75% oxygen. At rest, about 22% of oxygen goes from blood to the tissue. During Light exercise, 39% of oxygen goes from the blood to the tissue. During Heavy exercise, 80% of oxygen goes from the blood to the tissue. 2,3 DPG = increases unloading of oxygen from the blood to the tissues by lowering the affinity of Hb for Oxygen.    

When OxyHb is low, more 2,3 DPG is made. When OxyHb is high, less 2,3 DPG is made. OxyHb can get low because of Anemia or High altitude (where there PO2 is less) In adults, HbA binds 2,3 DPG. In fetus’, HbF does not bind 2,3 DPG since it has greater affinity for O2 in the child in utero.

CO2 = hemoglobin is important for CO2. CO2 is carried in 3 different forms. a) CO2 is Dissolved in blood plasma. b) CO2 combines with Hb to form CarbaminoHb. c) Bicarbonate ion = CO2 binds to water molecules forming carbonic acid. Carbonic Acid then breaks down into a hydrogen ion and bicarbonate ion. This process takes place in the red blood cells. Bicarbonate can then diffuse out of the cell and into the plasma. The hydrogen ion will attach to Hb and attract chloride ions. The attraction

of chloride ions into the RBC and the diffusion of Bicarbonate (HCO3-) out of the RBC is known as the Chloride Shift. Reverse Chloride Shift = Opposite of Chloride shift. The hydrogen ion dissociates from Hb. Once it dissociates from Hb, the hydrogen ion can combine with Bicarbonate (which comes in) to make Carbonic Acid. This causes Cl- to diffuse from the cell (it comes out) Acid – Base Balance = Another key function of the respiratory system that functions to maintain the pH of blood. Normal blood pH is between 7.35-7.45.     

Bicarbonate (weak base) = major buffer in blood Volatile Acid = Carbonic acid (since it can be exhaled as a gas) Non-Volatile Acids = acids such as lactic acid, fatty acids, ketones that are buffered by bicarbonate. These acids cannot be regulated by breathing. Overstress can cause the loss of bicarbonate. The Kidneys can increase the excretion of hydrogen ions which can increase the production of Bicarbonate.

Acidosis = happens when pH falls below 7.35. a) Respiratory Acidosis = happens when Hypoventilation causes an increase in CO2 retention. Increase in CO2 can lead to accumulation of carbonic acid which causes the blood pH to fall below normal. b) Metabolic Acidosis = Increased production of nonvolatile acids or the loss of blood bicarbonate (by diarrhea) causes bood pH to fall below normal. Alkalosis = happens when pH rises above 7.45 a) Respiratory Alkalosis = A rise in blood pH due to either in decrease of CO2 by hyperventilation or the loss of carbonic acid b) Metabolic Alkalosis = A rise in blood pH caused by either the loss of nonvolatile acids by way of vomiting, or by excessive accumulation of bicarbonate....