Chapter 22: The Respiratory System Flashcards
General Function of the Respiratory System:
o 1. Filters inspired air.
o 2. Provides for gas exchange.
o 3. Helps regulate blood pH.
o 4. Olfaction (sense of smell).
o 5. Produces sounds and resonance for vocalization.
o 6. Way of getting rid of small amounts of water and heat.
Nasal Cavity:
o External and internal nares.
o Nasal septum.
o Warms, humidifies, filters incoming air (rich network of capillary plexuses and thin-walled veins).
o Nasal conchae and nasal meatuses increase surface area of internal nose.
o Nasal mucous membrane = First line of defense! (ciliated pseudostratified columnar epithelium).
Paranasal Sinuses:
o Drain into nasal cavity.
o Resonance for speech.
o Cavities lined by mucous membranes that drain into.
Epistaxis:
Nosebleed
Rhinitis:
Excessive mucus production with inflammation of nasal mucosa, leads to a runny nose.
Rhinoplasty:
Plastic Surgery of the Nose.
Pharynx:
o Extends from CHOANAE = INTERNAL NARES = POSTERIOR NASAL APERTURES to the level of the cricoid cartilage of the larynx.
o Moves air and food to distal locations.
o Contains openings for Eustachian tubes.
o Houses our tonsils.
o Wall = mostly skeletal muscles lined by mucous membranes.
o Divisions:
o Nasopharynx.
o Oropharynx.
o Laryngopharynx.
Larynx:
o 1.5 inch passageway connecting the laryngopharynx to the trachea.
o Primary function: patent airway!
o Keep food and ingested fluids out of airways.
o Another function: produce sound!
o 9 separate pieces of cartilage
o Thyroid cartilage = “Adam’s apple”
o Cricoid cartilage = “ring” shaped
o Epiglottis = leaf-shaped “trap door”
o GLOTTIS:
o True vocal cords —inferior.
o Rima glottis = space between the true vocal folds, this closes when we swallow.
o FALSE VOCAL CORDS = vestibular folds.
o LARYNGITIS = inflammation of larynx.
o CANCER OF LARYNX = almost entirely in people who smoke.
Trachea:
o Extends from larynx to superior border T5.
o 4 to 5 inch long windpipe, three-quarters an inch in diameter.
o C-shaped hyaline cartilage rings = maintains patency of airway = 16 to 20 partial rings.
o Trachealis muscle on posterior side (smooth muscle).
o Carina = inferior trachea at bifurcation = generates a very strong cough reflex.
o Tracheostomy = incision into trachea inferior to cricoid cartilage, must suction frequently!
Primary Bronchi:
o PRIMARY BRONCHUS = division of the trachea into the hilum of each lung.
o RIGHT primary bronchus is shorter, wider, and more vertical, things more likely to get stuck!
o Supported by hyaline cartilage, histology includes ciliated pseudostratified columnar epithelium, elastic c.t., and smooth muscle.
o As you go deeper down the “bronchial tree,” there is less and less cartilage, more and more smooth muscle, but ALWAYS elastic c.t. and an epithelial membrane of some type!
“Trends” in Histology from Upper to Lower Conducting Zones:
o Decreasing amounts of: Cartilage, Glands, Goblet cells, Height of columnar epithelial cells, Size of lumen.
o Increasing amounts of: Smooth muscle, Elastic tissue.
Bronchioles:
o Bronchiole tree = 20 to 25 orders of branching, blood supply from bronchial arteries that come off thoracic aorta. o Once they get less than 1 mm in diameter, then there is no cartilage. o BRONCHOCONSTRICTION (smooth muscle contraction with narrowing of airways). o BRONCHODILATION (smooth muscle relaxation with lumen of airways increasing in size… sympathetic nervous system stimulation with beta two adrenergic receptors!).
Narrowing of Bronchioles:
o 1. Bronchoconstriction. o 2. Obstruction. o Inflammation: o Infection. o Irritation (pollution, allergens). o Cystic fibrosis o Genetic defect in Chromosome #7 o Abnormal Chloride pump o Cl- stays inside surface cell o Na+ stays with it o Water comes in, leaving mucus in lumen thick, viscous, and dry, clogs the airways.
Terminal Bronchioles:
o Less than 0.5 mm in diameter.
o Over 65,000 terminal bronchioles between the two lungs (one bronchiole may divide into 50 to 80 terminal bronchioles!!!).
o No mucous glands, no goblet cells, very few cilia if any = great need for MACROPHAGES.
o Each one divides into 2/more respiratory bronchioles.
Respiratory Bronchioles:
o Beginning of RESPIRATORY ZONE (vs. the “conducting zone”), where gas exchange can begin.
o Each respiratory bronchiole divides into 2 to 10 alveolar ducts.
o Alveolar ducts end in alveolar sacs.
o Alveolar sacs are clusters of individual alveoli (one alveolus, several alveoli).
Alveolus:
o Air pouch 0.2 to 0.5 mm in diameter; may contain alveolar pores.
o Specialized cells:
o Squamous (Type I) alveolar cells (simple squamous epithelial cells for gas exchange)(95 percent of surface area of alveolus).
o Great (Type II) alveolar cells = septal cells (secrete surfactant).
o Alveolar macrophages = dust cells.
o Outer surface = network of blood capillaries branching off the pulmonary arteries.
o Fibroblasts produce reticular and elastic fibers that surround alveoli.
Respiratory Membrane:
o Consists of 4 layers of tissue = 0.5 microns thick (tissue paper is 15X thicker).
o Alveolar wall with 3 cell types.
o Basement membrane underlying alveolar wall.
o Capillary basement membrane.
o Capillary wall = simple squamous = endothelium.
o Estimated that the two lungs contain 300 million alveoli with a combined surface area of 750 square feet = size of a racquetball court!
Ventilation-Perfusion Coupling:
o Pulmonary BLOOD VESSELS have a weird feature = they CONSTRICT in response to localized hypoxia (remember: most blood vessels would reflexively vasodilate with hypoxia).
o This diverts pulmonary blood from poorly ventilated areas to better-ventilated regions of the lungs!
o Too much vasoconstriction can cause pulmonary hypertension leads to right-sided CHF!
Lungs:
o Located on either side of mediastinum.
o Right lung is broader but shorter (3 lobes).
o Left lung is 10 percent smaller (2 lobes only).
o Apex of lungs is just superior to clavicles.
o Base of lungs sits on top of the diaphragm.
o R and L Phrenic nerves innervate the diaphragm (C3, C4, C5 keeps the diaphragm alive).
o Lungs surrounded by pleural membrane (visceral pleura, parietal pleura, pleural cavity in between).
Pleuritis:
Inflammation of pleura. Not enough fluid= pleural friction rub. Too much fluid= pleural effusion.
Thoracentesis:
Removal of excess fluid in pleural cavity.
Atelectasis:
collapse of a portion/all of lung.
Pneumothorax:
Air in the pleural space.
Hemothorax:
Blood in the pleural space.
RDS:
Respiratory distress syndrome= deficiency of surfactant in infants.
Physiology of Breathing:
o 1. Pulmonary ventilation = “breathing” (atmospheric air enters/leaves alveoli).
o 2. Alveolar gas exchange = gas exchange at the respiratory membrane (external respiration).
o 3. Transport of gases in the blood.
o 4. Systemic gas exchange = gas exchange between the systemic capillaries leads to interstitial fluid leads to cells (internal respiration).
Basic Facts About Pulmonary Respiration:
o Airflow is governed by the same principles of flow, pressure & resistance that govern blood flow:
o FLOW = difference in pressure between 2 points divided by resistance.
o Air always diffuses FROM areas of higher pressure TO areas of lower pressure.
o Atmospheric pressure: A column of air 100 km high exerts 1 atmosphere of pressure = enough to force a column of mercury up a tube 760 mm at sea level.
o Intrapulmonary pressure: The pressure of air inside the alveoli of the lungs
o What matters to the FLOW of air is the DIFFERENCE between atmospheric pressure and intrapulmonary pressure.
o VOLUME changes can cause changes in the PRESSURE of gases.
o Boyle’s Law: The pressure of a given quantity of gas is inversely proportional to its volume (assuming a constant temp).
Pulmonary Ventilation:
o Pulmonary ventilation refers to the flow of air from the atmosphere INTO and OUT OF the alveoli of the lungs.
o Inhalation: Air flows INTO the lungs if the atmospheric pressure (760 mm) is greater than the intrapulmonary pressure (758 mm).
o Exhalation: Air flows OUT of the lungs if the atmospheric pressure (760 mm) is LESS than the intrapulmonary pressure (762 mm).
Primary Muscles of Inhalation:
o Depression of diaphragm accounts for 75 percent of quiet inspiration.
o Depression of diaphragm by 1 to 1.5 cm causes a 1 to 3 mm pressure difference.
o Contraction of External intercostal muscles account for 25 percent of quiet inspiration.
Quiet vs. Force Inhalation:
o When the diaphragm descends 1 – 1.5 cm, about 500 mL of air comes into the lungs = TIDAL VOLUME.
o Stronger contraction of the diaphragm (descending down 7 to 10 cm) & accessory muscles can allow for forced inhalation of 2000 -3000 mL of air!
o Accessory muscles of forced inhalation include: scalene muscles, pectoralis minor, sternocleidomastoid, serratus anterior.
Steps for Inhalation:
o 1. Inspiratory muscles contract (diaphragm descends; rib cage rises).
o 2. Thoracic cavity volume increases.
o 3. Lungs are stretched; intrapulmonary volume increases.
o 4. Intrapulmonary pressure drops (to -1mm Hg).
o 5. Air (gases) flow into lungs down its pressure gradient until intrapulmonary pressure is 0 (equal to atmospheric pressure).
Steps for Exhalation:
o 1. Inspiratory muscle relax (diaphragm rises; rib cage descends due to recoil of costal cartilages).
o 2. Thoracic cavity volume decreases.
o 3. Elastic lungs recoil passively; intrapulmonary volume decreases.
o 4. Intrapulmonary pressure rises (to +1 mm Hg.)
o 5. Air (gases) flows out of lungs down its pressure gradient until intrapulmonary pressure is 0.
Quiet (Passive) Exhalation:
o In a healthy person, the relaxation of the diaphragm and external intercostal muscles leads to exhalation.
o This is a PASSIVE process which depends primarily on the natural elasticity of the lungs and the elasticity of the chest wall.
Muscles of Forced Exhalation:
o Internal intercostal muscles are active in FORCED exhalation. o Other accessory muscles: o Abdominal muscles. o Latissimus dorsi. o Quadratus lumborum. o Serratus posterior inferior.
Valsalva Maneuver:
o When the diaphragm contracts, it INCREASES abdominal pressure.
o If we take a deep breath, then close the rima glottidis and contract our abdominal muscles, we increase abdominal pressure even more = Valsalva Maneuver
o We use the valsalva maneuver in defecation, childbirth, and even urination.
o This decreases heart rate via stimulation of the Vagus nerve (CN X).
Factors Affecting Pulmonary Ventilation:
o FLOW = difference in pressure between 2 points divided by resistance.
o Note: Air pressure differences determine the DIRECTION of the flow of air.
o RESISTANCE to air flow can affect the RATE of airflow and the EASE of air flow.
o 1. obstruction of airways.
o 2. pulmonary (lung) compliance.
o 3. surface tension of the alveoli.
o 4. changes in pressure of pleural cavity.
