Respiratory Pressures and Laryngeal Muscles

Respiratory Pressures

• Intrapleural pressure is the pressure within the pleural cavity, between the lungs and chest wall
  • It is typically negative, lower than atmospheric pressure
  • The negative pressure helps keep lungs inflated and prevents collapse
• Intrapulmonary pressure (alveolar pressure) is the pressure within the lung's air sacs (alveoli)
  • Varies during the respiratory cycle
  • It generally equalizes with atmospheric pressure during normal breathing
• Atmospheric pressure (barometric pressure) is the pressure exerted by Earth's atmosphere
  • Measured in millimeters of mercury (mmHg)
  • At sea level, it is typically around 760 mmHg

Laryngeal Muscles and Vocal Cord Movement

• Laryngeal muscles control the position and tension of the vocal cords within the larynx
  • The larynx is located at the top of the trachea (windpipe)
• The muscles adjust the size of the opening between the vocal cords (glottis)
  • This produces different sounds as air passes through
• Intrinsic and extrinsic muscles are two sets within the larynx that move the vocal cords
  • Intrinsic muscles are located within the larynx, are responsible for fine-tuning vocal cord position and tension
  • Extrinsic muscles attach to the larynx from the outside, helping move it

Specific Muscles

• The posterior cricoarytenoid muscle abducts (separates) the vocal cords, allowing for inhalation
• The lateral cricoarytenoid muscle adducts (brings together) the vocal cords, for sound production
• Intrinsic muscles include the thyroarytenoid
  • It controls vocal cord tension along with the lateral cricoarytenoid for adduction
• Extrinsic muscles include the sternothyroid
  • It lowers the larynx and lengthens vocal cords for deeper tones
• The cricothyroid muscle raises the larynx and shortens vocal cords for higher tones
• Muscle contraction adjusts the position and tension of vocal cords
  • This changes the glottis' size and shape and produces different sounds
• The nervous system controls the precise movements of the laryngeal muscles

Ventilation

• Ventilation is the process of breathing, including both inhalation and exhalation

Inhalation

• The diaphragm and external intercostal muscles contract
• Intrapulmonary volume expands in all directions, including vertically
• Intrapulmonary pressure drops
• Air is drawn in as the pressure drops to reach equilibrium between intrapulmonary and atmospheric pressure
• The thoracic cavity expands, increasing its volume and expanding the lungs
  • Decreased pressure inside the lungs relative to the outside
  • Air flows into the lungs through the airways

Exhalation

• Internal intercostals and transverse thoracis muscles relax
• Intrapulmonary volume decreases, and pressure increases
• Air is expelled to re-establish equilibrium between intrapulmonary and atmospheric pressure
• Diaphragm and external intercostal muscles relax
• The elastic recoil of the lungs causes a decrease in volume
  • This causes air to flow out of the lungs

Lung Volumes

• Four pulmonary volumes exist:
  • Tidal volume: air inhaled/exhaled during normal breathing (500 mL)
  • Inspiratory reserve volume: air forcefully inhaled after normal inspiration (3000 mL)
  • Expiratory reserve volume (ERV): maximal air exhaled after normal exhalation (1100 mL)
  • Residual volume: air left in the lung after maximal exhalation (1200 mL)
  • Minute volume: normal air inspired/expired in 1 minute of normal pulmonary ventilation

Lung Capacities

• Vital capacity is the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume: 4600 mL
• Inspiratory capacity is tidal volume plus inspiratory reserve volume; the air a person can inspire maximally after normal expiration: 3500 mL
• Functional residual capacity is expiratory reserve volume plus residual volume; the air remaining in lungs after normal expiration: 2300 mL
• Forced Expiratory Vital Capacity (FEV) is the air expelled from the lungs in 1 second
• Total lung capacity is the sum of inspiratory and expiratory reserve volumes plus tidal volume and residual volume: 5800 mL

Internal Surface Area of the Lungs

• The alveoli are the site of pulmonary gas exchange that increases surface area
  • They are numerous, about 300 million in each lung
  • A large surface area to volume ratio exists
  • The alveolar walls are very thin for efficient gas diffusion between air and blood
• The tracheobronchial tree consists of the trachea and network of air tubes in the lungs
  • The trachea divides into left and right main bronchus
  • Each main bronchus divides into smaller bronchi which terminate in microscopic tubes and sacs
  • The bronchial tree delivers air to the alveoli where gas exchange with the bloodstream occurs

Compliance

• Compliance is the measure of how easily a structure stretches
  • Defined as the change in volume per unit change in pressure
• In respiratory physiology, compliance is the ability of lungs to stretch/expand during inhalation and return during exhalation
  • It is a measure of air ease moving in and out of the lungs
• Lung compliance involves elasticity of lung tissue, surface tension within the alveoli, and airway resistance
  • High the compliance means the lungs expand easily with minimal effort, for efficient gas exchange
  • Low compliance requires more force to expand the lungs making breathing more difficult
• Clinically measured as change in lung volume per unit change in transpulmonary pressure

Reduced Compliance

• Reduced compliance makes it harder to expand the lungs and thorax
• Potential conditions are:
  • Pulmonary fibrosis: deposition of inelastic fibers in lung tissue
  • Infant respiratory distress syndrome and pulmonary edema: collapse of the alveoli
  • Asthma, bronchitis, and lung cancer: increased resistance to airflow
  • Kyphosis and scoliosis: deformities of the thoracic wall that reduce expansion ability

Increased Compliance

• With Emphysema the lungs and thorax have lost elasticity
• It becomes easier to expand the lungs and thorax from destruction of elastic tissue
• Expiration is less efficient (COPD - barrel chest)

Lung Disorders and Compliance

• Obstructive lung disorders, (asthma and COPD) are characterized by increased resistance to airflow
  • Leads to difficulty exhaling air, increased air trapping, reduced lung volume, and decreased compliance
  • Compliance is decreased due to increased resistance to airflow
• Restrictive lung disorders (pulmonary fibrosis and sarcoidosis), are characterized by reduced lung volume and capacity
  • The lungs become stiff and lose expansion ability, resulting in decreased lung compliance
  • Compliance decreases by reducing lung volume and capacity

Blood Flow Through the Kidney

• Blood flow trace from the abdominal aorta to the inferior vena cava (IVC):
  • Abdominal aorta → renal artery → segmental artery → interlobar artery → arcuate artery → afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries → arcuate vein → interlobar vein → segmental vein → renal vein → IVC

Filtrate/Urine Trace

• Filtrate/urine proceeds from Bowman’s capsule to the urethra:
  • Bowman’s capsule → proximal convoluted tubule → loop of Henle → distal convoluted tubule → collecting duct → minor calyx → major calyx → renal pelvis → ureter → bladder → urethra

Nephron Parts and Functions

• The nephron filters blood and produces urine.
• Renal Corpuscle:
  • The glomerulus is a network of capillaries for filtration.
  • Bowman's capsule surrounds the glomerulus and collects filtered fluid.
• Proximal Convoluted Tubule (PCT):
  • Extends from Bowman's capsule and reabsorbs nutrients, glucose, amino acids, and electrolytes from the filtrate, returning them to the bloodstream.
• Loop of Henle:
  • A U-shaped tube extending from the PCT that establishes a concentration gradient in the kidney.
  • This reaction allows for reabsorption of water and electrolytes.
• Distal Convoluted Tubule (DCT):
  • Connects to the Loop of Henle and regulates potassium and sodium ion concentrations in the blood.
  • It secretes waste products into the urine.
• Collecting Duct:
  • Receives urine from nephrons and regulates water and electrolyte concentration for fluid electrolyte balance.

Urine Formation

• Glomerular Filtration:
  • The renal filtrate is plasma, without blood cells and proteins with about 99% reabsorbed
  • The filtration membrane includes fenestrated endothelium, a basement membrane, and filtration slits formed by podocytes.
  • Filtration pressure changes are primarily caused by glomerular capillary pressure changes.
• Tubular Reabsorption
  • Filtrate is reabsorbed by passive transport, including simple and facilitated diffusion, active transport and symport
  • The thin segment of the nephron loop specializes in passive transport
  • The rest of the nephron and collecting ducts perform active/passive transport, and symport
    • Active transport moves mainly Na+ across the wall of nephron
    • Other ions and molecules move primarily with symport
    • Passive transport moves water, urea, and lipid-soluble, nonpolar compounds
• Tubular Secretion
  • Substances enter the proximal or distal convoluted tubules and collecting ducts
  • Hydrogen ions, K+, and some substances not produced in the body/secreted by antiport mechanisms
• Active transport spoons returns good (glucose or amino acids) substances to the blood
• Salt can be removed with salt transportprotein and regulate excess to urine

Urinalysis Results

• Increased salt (NaCl) concentration in the urine indicates a high salt diet
  • it is possible a salt transport protein problem
• Protein in the urine indicates a high protein diet
  • It is possible kidney damage(Maybe Glomerulus capillary damage)
• Amino acids in the urine indicates a high protein diet
  • It is possible an amino acid transport protein problem
• Blood cells in the urine may indicate kidney damage
  • This could be ureter or bladder damage or a kidney stone
• Glucose is found in the urine for recent consumption of a large meal or diabetes

Acids, Bases, and Buffers

• An acid is a proton donor that releases hydrogen ions (H+)
• Properties include a pH value less than 7
• Strong acids have a higher concentration of H+ ions, and weak acids have a lower concentration
• A base is a proton acceptor that binds to (accepts) H+
• Properties include a pH value greater than 7
• Strong bases have a higher concentration of OH- ions and weak bases have a lower concentration.
• Acids and bases neutralize each other, forming a salt and water in neutralization
  • The resulting solution's pH is 7 (neutral)
• Buffers resist pH changes when acids or bases are added
• The bicarbonate buffering system is an important mechanism for regulating the pH of bodily fluids
  • Bicarbonate ions (HCO3-) act as a base
  • Hydrogen ions (H+) act as an acid

Bicarbonate Buffering

• When excess acid (H+) is introduced, it reacts with bicarbonate ions (HCO3-)
  • This reaction produces carbonic acid (H2CO3), which breaks down into carbon dioxide (CO2) and water (H2O)
  • The carbon dioxide is then transported to the lungs and exhaled, helping to remove excess acid
• When excess base is introduced, bicarbonate ions react releasing hydrogen ions and carbonic acid

Acid-Base Imbalances

• Respiratory acidosis is caused by excess carbon dioxide (CO2) in the blood with the lungs unable to remove enough
  • Conditions include COPD, pneumonia, or asthma
  • Symptoms are shortness of breath, confusion, and lethargy
• Respiratory alkalosis is a deficiency of carbon dioxide in the blood, caused by rapid or shallow breathing (hyperventilation)
  • Possible effectors are anxiety, fever, or high altitude
  • Symptoms are dizziness, tingling in toes, and muscle cramps
• Metabolic acidosis happens when there is an excess of acid in the blood.
  • This can be due to a variety of conditions, such as uncontrolled diabetes, kidney disease, or severe diarrhea
  • Symptoms include fatigue, nausea, and rapid breathing
• Metabolic alkalosis happens when there is an excess of a base in the blood.
  • This can be due to a variety of conditions, such as vomiting, excessive use of antacids, or kidney disease
  • Symptoms are muscle weakness, nausea, and confusion
• The body restores acid-base balance by adjusting the respiratory rate or renal excretion of bicarbonate ions

Compensation

• Compensation restores acid-base balance with pH, partial pressure of carbon dioxide (PaCO2), or bicarbonate (HCO3-) levels
• Respiratory compensation adjusts the respiratory rate to regulate the PaCO2 levels
• Metabolic compensation changes the HCO3- levels in order to regulate the blood pH
• Complete restoration may not be achieved and compensation depends condition and body ability
• The primary cause of respiratory acidosis is a decrease in ventilation
  • This leads to high levels of carbon dioxide (CO2) can be due to COPD, asthma, pneumonia, or a drug overdose.
• Respiratory alkalosis can be caused by increase in ventilation
  • This leads to a decrease in CO2 levels in the blood and can be caused by hyperventilation, anxiety, high altitude, or pulmonary disease.
• Metabolic acidosis can occur from over production from acids, less of bicarbonate (HCO3-) from body or by with the kidneys.
  • Caused by conditions such as diabetic ketoacidosis, lactic acidosis, renal failure, or diarrhea.
• Metabolic alkalosis is from loss of acids from the body.
  • Caused by condition such as vomiting, prolonged use , or excessive ingestion of antacids.