CASE 4 Flashcards
Respiration
- pulmonary ventilation
- external respiration
- transport of respiratory gases
- internal respiration
pulmonary ventilation
air moves in and out the lungs, gases are constantly changed and refreshed
external respiration
oxygen diffuses from lungs to blood and CO2 is moved from tissue
transport of respiratory gases
oxygen is moved towards tissue. CO2 is moved from tissue
internal respiration
oxygen diffuses from blood to tissue cells, CO2 diffuses from tissue cells to blood
Tracheal wall
- consists of mucosa, submucosa, adventitia, hyaline cartilage
mucosa
- pseudostratified epithelium (most of respiratory system)
- cilia propel debris mucus toward the pharynx
submucosa
- connective tissue layer in the mucosa
- contains seromucous glands that help produce mucus sheets
- 16-20 c shaped rings of cartilage
adventitia
- outermost layer of connective tissue
Right and left main (primary) bronchi
- divided from trachea
- right bronchus is wider, shorter, more vertical than left, inhaled foreign object gets stuck there
lobar (secondary) bronchi
- subdivided from each bronchus
- right has three
- left has two
- each supplying one lung lobe
segmental (tertiary) bronchi
- branched of lobar bronchi
- divide repeatedly into smaller and smaller bronchi, bronchioles
order of division of bronchi
- trachea
- right and left main bronchi
- lobar bronchi
- segmental bronchi
- bronchioles
As conducting tubes become smaller these changes occur
- support structures change
- epithelium type changes
- amount of smooth muscle increases
support structures change
- irregular plates of cartilage replace the cartilage rings
- bronchioles dont have cartilage
epithelium type changes
- mucosal epithelium thins from pseudostratified columnar –> columnar –> cuboidal (terminal bronchioles)
amount of smooth muscle increases
- more smooth muscle and lack of cartilage allows the bronchioles to provide resistance to air passage under certain conditions
respiratory zone begins
terminal bronchioles feed into respiratory bronchioles –> winding alveolar ducts –> terminal clusters of alveoli called alveolar sacs
walls of alveoli
- primarily of single layer of squamous epithelial cells
type 1 alveolar cells
- surrounded by thin basement membrane (gas exchange)
- scattered across type 1 alveolar cells are cuboidal type 2 alveolar cells.
type 2 alveolar cells
- secrete surfactant, coats the gas exposed alveolar surfaces
- secrete antimicrobial proteins which are important for natural immunity
respiratory membrane
capillary and alveolar walls and their fused basement
alveoli have 3 features:
- they are surrounded by elastic fibers of the same type that surrounds the entire bronchial tree
- open alveolar pores connecting adjacent alveoli allow air pressure throughout the lung to be equalized and provide alternate air routes to any alveoli whose bronchi have collapsed due to disease
- alveolar macrophages crawl freely along internal alveolar surface. Immune function
lung root
pleurae (pair of serous membranes) connected to the mediastinum by vascular and bronchial attachments
costal surface
anterior, posterior and lateral surfaces lie in contact with ribs
lung apex
- narrow tip of lung
- is deep into the clavicle
lung base
inferior surface that rests on diaphragm
lung hilum
cavity on the mediastinal surface of each lung
- pulmonary and systemic blood vessels enter and leave lungs
Cardiac notch
- cavity that is molded for the heart
- in left lung (smaller lung)
left lung
- superior and inferior lobe is divided by the oblique fissure
right lung
- superior, middle and inferior lobes are subdivided by oblique fissure and horizontal fissures
The pleurae
- form a thin double layered serosa
1. parietal pleura
2. visceral pleura
parietal pleura
covers thoracic wall and superior face of diaphragm
visceral pleura
- covers the external lung surface (inner layer)
interpleural fluid
in between parietal pleura and visceral pleura, which fills the pleural cavity.
- allows lungs to glide easily over the thorax wall during breathing
surface tension
- draws the liquid molecules closer together and reduces their contact with the dissimilar gas molecules
- resists any force that tends to increase the surface area of the liquid
function of surfactant
- made up of lipids and proteins produced by type 2 alveolar cells
- decreases cohesiveness of water molecules –> the surface tension of alveolar fluid is reduced –> less energy is needed to overcome those forces to expand the lungs and discourage alveolar collapse.
lung compliance
- stretchiness of lungs
- measure of change in volume that occurs with a given change in transpulmonary pressure
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- more the lung expands –> more complance.
- determined by
1. distensibility of lung tissue
2. alveolar surface tension - healthy lungs have high compliance
Lung capacity, 4 respiratory volumes
- tidal volume TV
- inspiratory reserve volume (IRV)
- Expiratory reserve volume (ERV)
- residual volume (RV)
Tidal volume (TV)
amount of air that moves into and then out of the lungs with each breath (500 ml)
inspiratory reserve volume (IRV)
the amount of air that can be inspired forcibly beyond the TV (2100 to 3200 ml)
expiratory reserve volume (ERV)
amount of air that can be expelled from lungs after normal TV expiration (1000 to 1200 ml)
residual volume (RV)
air that remains in the lungs even after the strongest expiration (1200 ml)
- prevents lungs from collapsing and keeps alveoli open
4 respiratory capacities
- inspiratory capacity (IC)
- functional residual capacity (FRC)
- vital capacity (VC)
- total lung capacity (TLC)
inspiratory capacity (IC)
total amount of air that can be inspired after a normal tidal volume expiration
- TV + IRV
functional residual capacity (FRC)
amount of air remaining in the lungs after a normal tidal volume expiration
- RV + ERV
vital capacity (VC)
total amount of exchangable air
- TV + IRV + ERV
total lung capacity (TLC)
sum of all volumes (6000 ml)
dead space
- inspired air that never contributes to gas exchange in alveoli
- anatomical dead space, 150 ml
- you also have alveolar dead space
- both added up is total dead space
respiratory rate
number of breaths per minute
alveolar ventilation rate (AVR), considers the volume of dead space
AVR = frequency (breaths/minute) x (TV - dead space) x (ml/breath)
- bigger volume is biffer AVR
Mechanisms of breathing pressures
- atmospheric pressure Patm = 760 mmHg
- intrapulmonary pressure Ppul: pressure in alveoli. Rises and falls with phases of breathing, always equalizes with atmospheric pressure
- Intrapleural pressure Pip: pressure in pleural cavity, fluctuates with breathing phases. Is always 4 mmHg less than Ppul caused by processes
why interpleural pressure Pip is always less than Ppul
- lungs tendency to recoil, lungs always take the smallest size possible
- surface tension of alveolar fluid, molecules of fluid lining in alveoli attract each other. Surface tension acts to draw the alveoli to their smallest possible dimension
Transpulmonary pressure
- difference between intrapulmonary and intrapleural pressure (Ppul -Pip).
- prevents lungs from collapsing
- size of this pressure detrmines size of lungs –> greater the transpulmonary pressure, larger the lungs
pulmonary ventilation
- consists of inspiration and expiration
- depends on volume changes in thoracic cavity
- volume changes lead to pressure changes
- Boyle’s law = P1 x V1 = P2 x V2
ventilation-perfusion coupling
- for optimal gas exchange, coupling between ventilation and perfusion is needed
- ventilation: amount of gas reaching the alveoli
- perfusion: blood flow in pulmonary capillaries
- ratio: V (g/min) / Q (L/min)
ventilation-perfusion control
- PO2 controls perfusion by changing arteriolar diameter
- PCO2 controls ventilation by changing bronchiolar diameter. Increase –> bronchioles dilate . Decrease –> bronchioles constrict
Influence of local Po2 on perfusion
- alveolar ventilation is inadequate, local Po2 is low because blood takes O2 away more quickly than ventilation can replenish it
- in alveoli where ventilation is maximal, high Po2 dilates pulmonary arterioles and blood flow into the associated pulmonary capillaries increases.
Inspiration
- inspiratory muscles; diaphragm and external intercostal muscles
- action of diaphragm: when diaphragm contracts, moves inferiorly and flattens, the thoracic cavity increases
- action of intercostal muscles; external intercostal contract lift rib cage and pull sternum superiorly –> ribs swing outward –> expanding diameter of thorax
expiration
- depends on muscle elasticity, inspiratory muscles relax, rib cage descends and lungs recoil. volume in thoracic cavity decreases
- volume decreases –> compresses alveoli and Ppul rises above Patm –> forces gases to flow out of the lungs
Forced expiration
- is an active process produced by contracting abdominal wall muscles, primarily the oblique and transversus muscles
1. increase the intraabdominal pressure –> forces organs superiorly against the diaphragm
2. depress the rib cage. The internal intercostal muscles also help depress the rib cage and decrease thoracic volume.
