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Respiratory System
Respiration involves four processes Respiratory system↓
1. Pulmonary ventilation (breathing): movement of air into and out of lungs 2. External respiration: exchange of O2 and CO2 between lungs and blood **Circulatory system ↓
- Transport** of O2 and CO2 in blood 4. Internal respiration: exchange of O2 and CO2 between systemic blood vessels and tissues
- The process of doing gas exchange in the bodies tissues Major Respiratory Organs ● Nasal Cavity ● Oral cavity ● Larynx: voice box and opening to trachea and lower part of our airway ● Pharynx ● Trachea ● Lungs L/R ● Diaphragm ● Left Lung: 2 lobes : reason for asymmetry: to make room for the heart ● Right Lung: 3 lobes ● Nasopharynx: how most air comes in: serves purpose of humidifying air that comes in and trapping particulates that are in the air; mucosa in nasopharynx traps particulates ● Oropharynx ● Laryngopharynx: where larynx is located Lower Respiratory System
- Lower respiratory system consists of : – Larynx, trachea, bronchi, and lungs
- Broken into two zones
- Respiratory zone: site of gas exchange
- Consists of microscopic structures such as respiratory bronchioles, alveolar ducts, and alveoli : Simple squamous epithelia (gas exchange)
- Conducting zone: conduits that transport gas to and from gas exchange sites
- Includes all other respiratory structures
- Cleanses, warms, and humidifies air (no gas exchange)
Tissue Composition of Tracheal Wall Contains ● Goblet cell: produces mucus ● Cilia: move particles trapped in mucus away ● Mucosa and submucosa ● Pseudostratified ciliated columnar epithelium ● Lamina propria (connective tissue) ● Seromucous gland in submucosa ● Trachealis: muscles malleable enough to displace trachea enough to swallow The Larynx ● Hyaline Cartilage: cartilage in larynx ensures airway stays open ● Thyroid Cartilage: gives the adam's apple; adds to different pitches of voice in the two sexes ● Epiglottis: covers over the airway everytime we swallow to prevent food or liquid from entering the airway ● Vocal folds: bands of tissue that can close over the glottis or open up; when it closes down it produces sound Tracheal wall ● Trachealis is the muscle that ensures airways stays open ● Made of pseudostratified ciliated coloomnar epithelium to trap pathogens Conducting Zone Passages ● Left Main Primary Bronchi: has a rounded course; to accommodate heart ● Carina: “bow of a ship” meeting point of left and right bronchus’s ○ If food accidentally goes into airway it will most likely go into right bronchus; reason: more of a straight shot while left bronchus is curved Respiratory Zone Structures ● Terminal Bronchioles: have strips of smooth muscle ○ Relax: allowing bronchioles to dilate ○ Constrict: allowing bronchioles to close down ● Respiratory Bronchioles: lead to alveolus/alveoli ● Alveolar Pores: allows air to completely fill alveoli ● Alveoli: thin-walled, simple squamous epithelium: to allow rapid and easy diffusion ● Bronchoconostriction = asthma
- Innervation of the lungs - Lungs are innervated by parasympathetic and sympathetic motor fibers, as well as visceral sensory fibers - Nerves enter through pulmonary plexus on lung root - Run along bronchial tubes and blood vessels - Parasympathetic fibers cause bronchoconstriction, whereas sympathetic fibers cause bronchodilation List of Pressures ● This is ventilation ● Intrapleural Pressure ● -4mm Hg (756mm Hg) Always Negative : or there is no way of opening the lungs bc it creates a suction ● Pressure between parietal and visceral pleura ● Main source of function to pull in air “suction” ● If the number ever becomes positive the lung will collapse - Transpulmonary Pressure ● The difference in pressure from outside the lungs vs pressure inside the lungs - Intrapulmonary Pressure ● Pressure within the lungs Extra Information ● Negative pressure= “suction” drawing in air ● Positive Pressure= “pushing” ● Ventilation: movement of the diaphragm and the ribs changing the shape of the thoracic wall ● Pleural Fluid: allows there to be a negative pressure in between the two pleura Pneumothorax ● Air in the thorax: in between the visceral and parietal pleura ● Air comes in through wound causing lung to collapse ● Tension Pneumothorax: the pressure can become so great, putting pressure on the heart and restricting vessels ● Collapsed Lung: atelectasis Pulmonary Ventilation ● Boyle’s law : relationship between pressure and volume of a gas - Gases always fill the container they are in
- If amount of gas is the same and container size is reduced, pressure will increase
- So pressure (P) varies inversely with volume (V)
- Mathematically:
- P ₁ V ₁ = P ₂ V ₂ **Inspiration **Increasing volume, decreasing pressure****
- Inspiratory muscles contract (diaphragm descends (flattens out) ; rib cage rises).
- Thoracic cavity volume increases. a. “Pump handle”: inferior part of sternum moves forward/anteriorly
- Lungs are stretched; intrapulmonary volume increases.
- Intrapulmonary pressure drops (to1 mm Hg).
- Air (gases) flows into lungs down its pressure gradient until intrapulmonary pressure is 0 (equal to atmospheric pressure). *** external intercostals contract*** **Expiration **Decreasing volume, increasing pressure****
- Inspiratory muscles relax (diaphragm rises (folds up); rib cage descends due to recoil of costal cartilages).
- Thoracic cavity volume decreases.
- Elastic lungs recoil passively; intrapulmonary volume decreases.
- Intrapulmonary pressure rises (to 1 mm Hg).
- Air (gases) flows out of the lungs down its pressure gradient until intrapulmonary pressure is 0. external intercostals relax Changes in In Intrapulmonary & Intrapleural Pressures during Inspiration and Expiration ● Intrapulmonary pressure : Pressure inside lung decreases as lung volume increases during inspiration; pressure increases during expiration ● Intrapleural pressure: Pleural cavity pressure becomes more negative as the chest wall expands during inspiration. Returns to initial value as chest wall recoils. ● Volume of breath: During each breath, the pressure gradients move 0.5 liter of air into and out of the lungs.
● Vital Capacity: inspiratory reserve volume + tidal volume + expiratory reserve volume ○ Everything minus residual volume ○ Example: Blowing candles out all at once ● Functional Residual Capacity: what is left in the lungs below what we normally use (tidal volume): air left in lungs for gas exchange below tidal volume Dead Space ● Anatomical dead space: does not contribute to gas exchange
- Consists of air that remains in passageways: in trachea, bronchi; parts of conducting side of respiratory system ~150 ml out of 500 ml TV ● Alveolar dead space: space occupied by nonfunctional alveoli
- Can be due to collapse or obstruction Example: Lungs With pneumonia: some of that alveolar space isn’t open to do gas exchange instead it is filled with fluid. ● Total dead space: sum of anatomical and alveolar dead space ○ Due to damaged alveoli or just passageways that don’t do gas exchange Alveolar Ventilation ● Minute ventilation: total amount of gas that flows into or out of respiratory tract in 1 minute
- Normal at rest = ~ 6 L/min
- Normal with exercise = up to 200 L/min
- Only rough estimate of respiratory efficiency ● Alveolar ventilation rate (AVR): flow of gases into and out of alveoli during a particular time
- Better indicator of effective ventilation Basic Properties of Gases ● Dalton’s law of partial pressures
- Total pressure exerted by mixture of gases is equal to sum of pressures exerted by each gas
- Partial pressure ● Pressure exerted by each gas in mixture ● Directly proportional to its percentage in mixture ● Total atmospheric pressure equals 760 mm Hg ● Nitrogen makes up ~78.6% of air; therefore, partial pressure of nitrogen, P ₂, ○ can be calculated : 0.786 x 760mm Hg = 597mm Hg due to N₂ ● Oxygen makes up 20.9% of air, so Pₒ₂ equals: 0.209 x 760mm Hg = 159mm Hg
● Air also contains 0.04% CO2, 0.5% water vapor, and insignificant amounts of other gases ● At high altitudes, partial pressures declines, but at lower altitudes (under water), partial pressures increase significantly ● Henry’s law
- For gas mixtures in contact with liquids:
- Each gas will dissolve in the liquid in proportion to its partial pressure
- At equilibrium, partial pressures in the two phases will be equal
- Amount of each gas that will dissolve depends on:
- **Solubility: CO₂ is 20 more soluble in water than O₂, and little N₂ will dissolve ★ Not all gases are equally soluble in water
- **Temperature: as temperature of liquid rises, solubility decreases
- Example of Henry’s law: hyperbaric chambers External Respiration ● External respiration (pulmonary gas exchange) involves the exchange of O and CO2 across respiratory membranes ● Exchange is influenced by:
- Partial pressure gradients and gas solubilities
- Thickness and surface area of respiratory membrane: thin membrane for rapid diffusion of gases
- Ventilation-perfusion coupling : matching of alveolar ventilation with pulmonary blood perfusion ★ Partial pressure gradients and gas solubilities
- Steep partial pressure gradient for O₂ exists between blood and lungs
- Venous blood PO2 = 40 mm Hg
- Alveolar PO2 = 104 mm Hg
- Drives oxygen flow into blood
- Equilibrium is reached across respiratory membrane in ~0. seconds, but it takes red blood cell ~0.75 seconds to travel from start to end of pulmonary capillary » Ensures adequate oxygenation even if blood flow increases 3x
- Partial pressure gradient for CO2 is less steep
- Venous blood PCO2 = 45 mm Hg
- Alveolar PCO2 = 40 mm Hg
● Association of oxygen and hemoglobin (cont.)
- Loading and unloading of O2 is facilitated by a change in shape of Hemoglobin
- As O2 binds, Hb changes shape, increasing its affinity for O2 increases
- As O2 is released, Hb shape change causes a decrease in affinity for O
- Fully saturated (100%): all four heme groups carry O
- Partially saturated: when only one to three hemes carry O
- Rate of loading and unloading of O2 is regulated to ensure adequate oxygen delivery to cells
- Factors that influence hemoglobin saturation:
- PO
- Other factors such as: **- Temperature ↑
- Blood pH ↓
- PCO2 ↑ The 3 Above cause active tissues to get the most O ₂ - Concentration of BPG *** They ALL encourage O ₂ **to leave Hemoglobin in active tissues****
The amount of oxygen carried by hemoglobin depends on the PO ₂ (the amount of oxygen) available locally. This relationship ensures optimal oxygen pickup and delivery.
- The oxygen-hemoglobin dissociation curve will help you understand how the properties of hemoglobin (Hb) affect oxygen binding in the lungs and oxygen release in the tissues.
- The y-axis tells you how much O2 is bound to Hb. At 100%, each Hb molecule has 4 bound oxygen molecules.
- If more O₂ is present, more O₂ is bound. However, because of Hb’s properties (O₂ binding strength changes with saturation), this is an S-shaped curve.
- The x-axis tells you the relative amount (partial pressure) of O2 dissolved in the fluid surrounding the Hb. - In the lungs, where PO2 is high (100 mm Hg), Hb is almost fully saturated (98%) with O2. - In the tissues of other organs, where PO2 is low (40 mm Hg), Hb is less saturated (75%) with O2.
- Influence of PO2 on hemoglobin saturation ↑↑ (same thing)
- In arterial blood:
- PO2 is 100 mm Hg and contains 20 ml of oxygen per 100 ml blood ( volume %)
- Hb is 98% saturated
- Further increases in PO2 (as in deep breathing) produce minimal increases in O2 binding
- In venous blood, PO2 is 40 mm Hg and contains 15 volume % oxygen
- Hb is still 75% saturated
- Venous reserve : oxygen remaining in venous blood that can still be used The effect of temperature, PCO2, and blood pH on the oxygen-hemoglobin dissociation curve
- Higher temperatures: hemoglobin releases O2 MORE EASILY
- Lower temperatures: hemoglobin holds onto O2 STRONGLY
- Less CO2: Hemoglobin holds onto O2 STRONGLY
- High CO2: Hemoglobin releases O2 MORE EASILY - Influence of other factors on hemoglobin saturation (cont.)
- As cells metabolize glucose, they use O2, causing:
- Increases in PCO2 and H+ in capillary blood
- Declining blood pH (acidosis) and increasing Pco2 cause Hb-O2 bond to weaken
Transport and Exchange of CO2 and O ● Internal Respiration: oxygen release and carbon dioxide pickup at the tissues (blood) O ● Small percentage of oxygen is dissolved as free gas in the blood plasma ● Bulk of oxygen in RBCs is bound to hemoglobin ● Getting Oxygen out into the body’s tissues: oxygen dissociates from hemoglobin due to all of the bohr effects and diffuses into the body’s tissues where it’s needed. CO ● Small percentage of CO2 is dissolved in the blood plasma ● Main way CO2 is carried: small percentage of co2 will combine with water to give carbonic acid which dissociates to hydrogen ion and bicarbonate (spontaneous and slow reaction to carry CO2) ● Bicarbonate will travel in the plasma fine, and the hydrogen ions can bind to plasma proteins (the acidity is buffered by plasma proteins(Albumin)) ● Other way CO2 is carried by dissolving into the plasma and binding onto hemoglobin (the protein part) ● Other way CO2 is carried is when it combines with water to give carbon acid which dissociates to hydrogen ion and bicarbonate (Spontaneous and FAST reaction to carry CO2) FAST DUE TO: Carbonic anhydrase being involved ● MOST CO2 is carried in the plasma as bicarbonate Transport in the Lungs: all of this ↑↑↑↑↑↑↑↑↑↑↑ but reversed EXTERNAL RESPIRATION
- Influence of CO2 on blood pH
- Carbonic acid–bicarbonate buffer system : helps blood resist changes in pH
- If H+ concentration in blood rises, excess H+ is removed by combining with HCO3– to form H2CO3, which dissociates into CO2 and H2O
- If H+ concentration begins to drop, H2CO3 dissociates, releasing H+
- HCO3– is considered the alkaline reserve of carbonic acid- bicarbonate buffer system
- Changes in respiratory rate and depth affect blood pH
- Slow, shallow breathing causes an increase in CO2 in blood, resulting in a drop in pH (INCREASE ACIDITY)
- Rapid, deep breathing causes a decrease in CO2 in blood, resulting in a rise in pH (DECREASE ACIDITY)
- Changes in ventilation can help adjust pH when disturbances are caused by metabolic factors
- Breathing plays a major role in acid-base balance of body Buildup of co2 → increased acidity: Hypercapnia Lack of co2 → decreased acidity: Hypocapnia Factors Influencing Breathing Rate and Depth
- Chemical factors
- Most important of all factors affecting depth and rate of inspiration
- Changing levels of PCO2, PO2, and pH are most important
- Levels of these chemicals are sensed by:
- Central chemoreceptors : located throughout brain stem
- Peripheral chemoreceptors : found in aortic arch and carotid arteries
- Influence of PCO
- Most potent and most closely controlled ★ If blood PCO2 levels rise ( hypercapnia ), CO2 accumulates in brain and joins with water to become carbonic acid
- Carbonic acid dissociates, releasing H+, causing a drop in pH (increased acidity)
- Increased H+ stimulates central chemoreceptors of brain stem, which synapse with respiratory regulatory centers
- Respiratory centers increase depth and rate of breathing, which act to lower blood PCO2, and pH rises to normal levels ★ If blood PCO2 levels decrease, respiration becomes slow and shallow
- Apnea : breathing cessation that may occur when PCO2 levels drop abnormally low
- Swimmers sometimes voluntarily hyperventilate to enable them to hold their breath longer » Causes a drop in PCO2, which causes a delay in respiration, as PCO2 levels need to build back up » Can cause dangerous drops in PO2 levels ★ Influence of PO
- Peripheral chemoreceptors in aortic and carotid bodies sense arterial O levels
- Declining PO2 normally has only slight effect on ventilation because of huge O2 reservoir bound to Hb
○ The right side will drain into the lymphatic duct Lymph Transport ▪ Lymph system is a low-pressure system like venous system; needs help (pushing) returning lymph back to the upper part of the thorax ▪ Lymph is propelled by same mechanisms:
- Milking action of skeletal muscle
- Pressure changes in thorax during breathing
- Valves in lymph vessels help to prevent backflow
- Pulsations of nearby arteries
- Contractions of smooth muscle in walls of lymphatics ▪ Physical activity increases flow of lymph; immobilization of area keeps needed inflammatory material in area for faster healing Lymphoid Cells -- T cells and B cells protect against antigens → (anything the body perceives as foreign) ▪Examples: bacteria, toxins, viruses, mismatched RBCs, cancer cells ― T cells: manage immune response, and some also attack and destroy infected or cancer cells ― B cells: produce plasma cells , which secrete antibodies ▪Antibodies mark antigens for destruction by phagocytosis or other means Reticular connective tissue in a human lymph node ● Reticular cells on reticular fibers ● Macrophage ● Reticular fiber ● Lymphocytes ● Medullary Sinus ● Stroma: soft skeleton in some tissues Lymphoid Organs Primary Lymphoid Organs ● Thymus: t-cells mature and learn what to look for ● Red Bone marrow: where all the lymphocytes come from, B-cells mature Secondary Lymphoid Organs ● Tonsils: surrounding oropharynx ● Spleen ● Peyer’s Patches: aggregated lymphoid nodules in small intestine: like having tonsils around the intestines
● Appendix: like another peyer’s patch Lymph Node ● Afferent Lymphatic Vessels: lead into the lymph node; have valves that prevent lymph backflow ● Efferent Lymphatic Vessels: lead out of lymph node; at the hilum ● Cortex: outer tissue ○ Lymphoid follicle ○ Germinal center ○ Subcapsular sinus ● Medulla: interior tissue ○ Medullary cord ○ Medullary sinus Spleen ● LARGEST lymphatic organ ● Has WHITE PULP tissue ○ Collection of white blood cells ○ Find immune cells in white pulp ● Has RED PULP tissue ○ “RBC grave yard” ○ Older/fragile rbc pass through here causing them to rupture and break MALT ▪ Mucosa-associated lymphoid tissue (MALT)
- Lymphoid tissues in mucous membranes throughout body ▪ Protects from pathogens trying to enter body ▪ Found in mucosa of respiratory tract, genitourinary organs, and digestive tract; largest collections of MALT found in
- Tonsils
- Peyer’s patches
- Appendix Palatine Tonsil
- For tonsils to attack pathogens the pathogen has to go deep into that tissue into the tonsilar crypt.
- That’s why tonsils get infected easily
- Defensins : antimicrobial peptides that inhibit microbial growth; proteins (built in antibiotics
- Other chemicals: lipids in sebum and dermicidin in sweat are toxic to some bacteria Second Line of Defense: Cells and Chemicals ▪ Innate system necessary if microorganisms invade deeper tissues; includes:
- Phagocytes
- Natural Killer (NK) cells
- Inflammatory response (macrophages,mast cells,WBCs,and inflammatory chemicals)
- Antimicrobial proteins (interferons and complement proteins)
- Fever Phagocytes ▪ Phagocytes : white blood cells that ingest and digest (eat) foreign invaders ▪ Neutrophils : most abundant phagocytes, but die fighting; become phagocytic on exposure to infectious material; also respiratory burst ▪ Macrophages : develop from monocytes and are chief phagocytic cells; most robust phagocytic cell
- Free macrophages: wander through tissue spaces; example: alveolar macrophages
- Fixed macrophages: permanent residents of some organs; examples: stellate macrophages (liver) and microglia (brain) ▪ Phagocytosis Process starts when phagocyte recognizes and adheres to pathogen’s carbohydrate “signature” ― Some microorganisms have external capsules that hide their surface carbohydrates, helping them evade phagocytosis ▪ Opsonization : immune system uses antibodies or complement proteins as opsonins that coat pathogens » Act as “handles” for phagocytes to grab on to, enhancing phagocytosis
- Some pathogens are not killed with acidified lysosomal enzymes (e.g., tuberculosis bacteria) ― Helper T cells trigger macrophage to produce respiratory burst , which kills pathogens resistant to lysosomal enzymes by: ▪Releasing cell-killing free radicals ▪Producing oxidizing chemicals (e.g., H2O2)
▪Increasing pH and osmolarity of phagolysosome
- Defensins (in neutrophils) also help by piercing membrane of pathogen; found where any part of the body is open to the outside Natural Killer (NK) Cells ▪ Nonphagocytic, large granular lymphocytes that police blood and lymph
- Can kill cancer and virus-infected cells before adaptive immune system is activated ▪ Attack cells that lack “self” cell-surface receptors ▪ Kill by inducing apoptosis in cancer cells and virus-infected cells
- Apoptosis: force cells to self destruct ▪ Secrete potent chemicals that enhance inflammatory response Inflammation: Tissue Response to Injury ▪ Four cardinal signs of acute inflammation:
- Redness
- Heat
- Swelling
- Pain
- Sometimes a fifth sign , impairment of function, is seen if movement or use of area is hampered ▪ Inflammatory chemical release
- Chemicals are released into ECF by injured tissues, immune cells, or blood proteins ― Example: histamine released by mast cells is key inflammatory chemical ― Release of cytokines that promote inflammation ▪ Other inflammatory mediators besides histamine - Kinins, prostaglandins(PGs) : paracrine gland secretes to increase inflammation locally, and complement proteins ― All cause vasodilation of local arterioles ― All make capillaries leaky: more fluid comes out into the tissues ― Many attract leukocytes to area ― Some have other inflammatory roles, such as triggering pain receptors, or prompting release of more inflammatory chemicals - BASICALLY ALERT IMMUNE SYSTEM TO A PROBLEM
