Exam 4

type I alveolar cells

flat squamous epithelial cells across which gas exchange takes place

type II alveolar cells

produce surfactant, a lipoprotein substance that decreases surface tension in alveoli and allows for greater ease of lung inflation

during inspiration…

contraction of diaphragm and expansion of chest cavity →

increase thoracic cavity volume →

decrease intrapleural P →

increase transpulmonary P and lungs expand →

alveolar P < atm P →

air moves into lungs

lung compliance

• ability of lungs to stretch (expand)

• low compliance (more stiff) due to:

  • reduce elasticity of lungs

  • block bronchi or smaller airways

  • increase surface tension in alveoli

  • impair flexibility of thoracic cage

ventilation (V)

• because of weight of lung and gravity when standing, intrapleural pressure is more negative at apex than at base

  • at rest, alveoli at apex are more fully expanded than those at base

  • during inspiration, alveoli at base expand more

perfusion (Q)

• in upright position, distance of upper apices above heart level exceed perfusion capabilities of pulmonary arterial P

  • blood flow in upper part of lungs < in base of lungs

V/Q mismatch

• with shunt (oirway obstruction), there is perfusion w/o ventilation = low V/Q = 0

  • occurs in atelectasis, foreign body aspiration

• with dead air space (blood flow obstruction), there is ventilation w/o perfusion, resulting in a high V/Q = infinity

  • occurs in pulmonary embolism

influenza

clinical manifestations:

• abrupt onset of fever and chills, rigors, malaise, muscle aching, headache, profuse watery nasal discharge, nonproductive cough and sore throat

• 1 distinguishing feature of influenza viral infection is rapid onset (1 to 2 min) of profound malaise

pneumonia

• inflammation of lung parenchyma in LRT, lung consolidation w/ alveoli filled w/ exudate

• classification according to type of agent:

  • typical— infection by bacteria that cause inflammation and exudation of fluid into air-filled spaces of alveoli

  • atypical— caused by viral and mycoplasma infections that involve alveolar septum and interstitium of lung

typical pneumonia

inflammation and exudation of fluid into air-filled spaces of alveoli

atypical pneumonia

lack lung consolidation, production of moderate amounts of sputum, moderate elevation of WBC count and lack of alveolar exudate

pneumococcal pneumonia

sxs:

• sudden onset of malaise, severe, shaking chills and fever

• during congestive stage, productive cough (mucopurulent sputum) and limited breath sounds w/ fine crackles

• as disease progresses, character of sputum changes → blood tinged or rust colored to purulent

• pleuritic pain: sharp pain that is more severe w/ respiratory movements

tuberculosis (TB)

• transmission:

  • airborne infections spread by droplet nuclei

    • minute, invisible particles of organisms suspended in air

• pathogenesis:

  • cell mediated immune response

    • confers resistance to organism

    • development of tissue hypersensitivity to tubercular antigens

  • cell mediated immune response initiated that contains infection

    • infected macrophages degrade mycobacteria and present antigens to T lymphocytes

    • sensitized T lymphocytes stimulate macrophages to increase lytic enzymes

      • also damages lung tissue

    • results in gray-white, circumscribed granulomatous lesion = Ghon focus

      • contains tubercle bacilli, macrophages and T cells

    • T cell hypersensitivity rxn produces tissue necrosis → central portion of Ghon focus undergoes soft, caseous necrosis

lung cancer

• primary risk factor: cigarette smoking

• other risks:

  • cigars, pipes, passive exposure

  • environmental and occupational carcinogens

    • asbestos

  • genetic susceptibility

  • benign chronic lung disorders

  • diet

  • gender

paraneoplastic syndromes

• produced in lung cancer

• ectopic hormones secreted by tumor cells or from autoantibodies released in response to tumor that cross-reacts w/ other tissues

• symptoms occur at sites distant from tumor or its metastasis

clinical manifestations of lung cancer

• chronic cough, SOB, whezzing

• compression of nerves or veins, erosion of blood vessels, GI obstruction

• hemoptysis, retrosternal pain, hoarseness, dysphagia, dyspnea w/ pleural effusion

• nonmetastatic paraneoplastic manifestations involving endocrine, neurologic, and connective tissue function

• nonspecific sxs: cachexia, anorexia, and weight loss

disorder of pleura

• pleural effusion: abnormal collection of fluid in pleural cavity

• hemothorax: type of pleural effusion in which there is blood in pleural cavity

• pneumothorax:

  • presence of air in pleural space

  • causes partial or complete collapse of affected lung

spontaneous pneumothorax

• occurs when air-filled blisters on lung surface ruptures

• allows atmospheric air from airways to enter pleural cavity

• air flows from alveoli into pleural space, causing involved portion of lung to collapse as a result of its own recoil

tension pneumothorax

• occurs when injury to chest or respiratory structures permits air to enter but not leave pleural space

• results in a rapid increase in pressure w/in chest →

  • compression atelectasis of unaffected lung

  • shift in mediastinum to opposite side of chest

emphysema

• loss of lung elasticity

• abnormal enlargement of airspaces distal to terminal bronchioles

  • hyperinflation of lungs and increase in total lung capacity (TLC)

• destruction of alveolar walls and capillary beds

pathogenesis of emphysema

antiprotease production and secretion may be inadequate to neutralize excess protease production resulting in breakdown of elastin

clinical manifestations of emphysema

• “pink puffers”

  • lack of cyanosis, use of accessory muscles and pursed-lip (“puffer”) breathing

    • enhance airflow and prevents airway collapse

• barrel chest

  • loss of lung elasticity and hyperinflation of lungs → airways collapse during expiration

  • air becomes trapped in alveoli and lungs, producing an increase in anteroposterior dimensions of chest

• decrease breath sounds

chronic obstructive bronchitis

• airway obstruction of major and small airways

• pathogenesis:

  • hypersecretion of mucus in large airways, associated with hypertrophy of submucosal glands in trachea and bronchi

clinical manifestations of chronic obstructive bronchitis

• “blue bloaters”

  • cyanosis

  • fluid retention associated w/ right-sided heart failure

• sputum overproduction, an early manifestation

• hemoptysis

gastrin

• produced by G cells in antrum of stomach

• stimulates secretion of gastric acid and pepsinogen

cholecystokinin (CCK)

• produced by I cells in intestinal mucosa

• stimulates contraction of gall bladder

• stimulates secretion of pancreatic enzymes

secretin

• produced by S cells in mucosa of duodenum and jejunum

• released in response to acidic chyme in duodenum

• inhibits gastric acid secretion by inhibiting gastrin

parietal cells secrete…

• HCl (gastric acid)

  • chemically breaks down and disinfects ingested food

• intrinsic factor (IF)

  • necessary for absorption of vitamin B12

chief cells secrete…

• pepsinogen

  • converted to pepsin when exposed to low pH of gastric juices

    • enzyme that initiates proteolysis