Structural zones
upper respiratory tract |
lower respiratory tract |
- nose |
- larynx |
- pharynx |
- trachea |
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- bronchi |
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- lungs |
Nasal cavities
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bony framework frontal bone, nasal bones, maxilla
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cartilaginous framework lateral nasal cartilages, septal cartilage, alar cartilage
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nasal cavity hollow space behind nose that air flows through
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septum thin wall made of cartilage/bone, divides inside of nose into two chambers
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mucous membrane thin tissue lining nose, sinuses & throat, warms & moistens air breathed in & makes sticky mucus that cleans the air of particles/dust
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turbinates curved, bony ridges lined with mucous membrane - warm & moisten air
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sinuses hollow, air-filled chambers in bones around your nose - mucus from sinuses drains into nasal cavity
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c |
- external nose is visible on face
- internal nose is large cavity beyond nasal vestibule, divided by septum into right/left nares
O2 transport
in the blood, some O2 is dissolved in plasma as a gas (about 1.5%) |
most O2 (about 98.5%) is carried attached to Hb |
oxygenated Hb = oxyhaemoglobin |
** the higher the Po2, the more O2 combines with Hb |
Volume-pressure relationship - Boyles law
pressure of a gas in a closed container is inversely proportional to the volume of the container |
Ventilation-perfusion coupling
blood flow to each area of the lungs matches the extent of airflow to alveoli in that area
in the lungs, vasoconstriction in response to hypoxia diverts pulmonary blood from poorly ventilated areas of the lungs to well-ventilated regions
in all other body tissues, hypoxia causes dilation of blood vessels to increase blood flow |
Alveoli
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type I cell simple squamous epithelial cells - site of gas exchange
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type II cell cuboidal epithelial cells, microvilli, secrete surfactant, lowers surface tension
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alveolar macrophages remove dust
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fibroblasts reticular/elastic fibers
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cup-shaped out-pouchings which participate in gas exchange, alveolar sac comprises two or more alveoli that share a common opening
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Respiration
1) pulmonary ventilation |
2) external (pulmonary) respiration |
3) internal (tissue) respiration |
External respiration (pulmonary) is gas exchange between alveoli & blood
Internal respiration (tissue) is gas exchange between systemic capillaries & tissues of the body
the rate of pulmonary & systemic gas exchange depends on...
1. partial pressure difference of the gases
2. SA available for gas exchange
3. diffusion distance
4. molecular weight & solubility of gases
Gross anatomy of lungs
pneumothorax - air
hemothorax - blood/pus
Pulmonary lobule
respiratory bronchioles give way to alveolar ducts & the simple cuboidal epithelium changes to squamous which comprises the alveolar ducts, sacs & alveoli.
bronchioles mark the start of the respiratory zone |
each pulmonary lobule is wrapped in elastic connective tissue & contains a lymphatic vessel, an arteriole, a venule & a terminal bronchiole.
Trachea - windpipe
- semi-rigid pipe made of semi-circular cartilaginous rings
- located anterior to esophagus
- approx. 12cm - extends from inferior portion of larynx
- divides into right & left primary bronchi
- composed of four layers:
1. mucosa (mucous-secreting epithelium)
2. submucosa
3. hyaline cartilage
4. adventitia |
Functional zones
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conducting zone involved with bringing air to site of external respiration, consists of nose/pharynx/layrnx/trachea/bronchi/bronchioles/terminal bronchioles.
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respiratory zone main site of gas exchange, consists of respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli.
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air passing through the respiratory tract transverses the...
1. nasal cavity
2. pharynx
3. larynx
4. trachea
5. primary bronchi
6. secondary bronchi
7. tertiary bronchi
8. bronchioles
9. alveoli (150 million/lung)
CO2 transport
transported in blood in three different forms: |
7% = dissolved in plasma (gas) |
70% = converted into carbonic acid by carbonic anhydrase before dissociated into bicarbonate & protons |
23% is attached to Hb forming carbaminohaemoglobin (Hb-CO2) but not at same binding sites as oxygen |
CO2 + H2O <---> H2CO3 <---> HCO3-
..................... CA
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Bronchial tree
- epithelium |
- goblet cells |
- ciliated cells |
- glands |
- hyaline cartilage |
- smooth muscle |
- elastic fibers |
trachea --> primary bronchi --> secondary bronchi --> tertiary bronchi --> bronchioles --> terminal bronchioles |
all branches from trachea to terminal bronchioles are conducting airways & do not participate in gas exchange.
Pulmonary circulation
lungs receive blood via two sets of arteries:
1. pulmonary arteries carry deoxygenated blood from right heart to lungs for oxygenation
2. bronchial arteries branch from aorta & deliver oxygenated blood to lungs primarily perfusing the muscular walls of the bronchi & bronchioles.
Cilia
cilia in upper respiratory tract move mucous & trapped particles down toward pharynx.
cilia in lower respiratory tract move them up toward larynx. |
Pulmonary ventilation - breathing
- movement of air between atmosphere & alveoli, consisting of inhalation/exhalation
- changes to intra-thoracic volume allow ventilation to occur |
rate of airflow & effort required depend on
1. alveolar surface tension
2. compliance of the lungs
3. airway resistance
Larynx - voice box
composed of nine pieces of cartilage, forms a short passageway connecting the laryngopharnx with the trachea |
Pharynx
hollow tube that starts posterior to internal nares & descends to opening of larynx in neck, formed by complex arrangement of skeletal muscles that assist in deglutition
functions as...
1. passageway
2. resonating chamber
3. housing for tonsils |
O2 transport
in the blood, some O2 is dissolved in plasma as a gas (about 1.5%) |
most O2 (about 98.5%) is carried attached to Hb |
oxygenated Hb = oxyhaemoglobin |
the higher to Po2, the more O2 combines with Hb
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