respiration. ontogenesis of respiration. respiration. ontogenesis of respiration
TRANSCRIPT
Respiration. Ontogenesis of Respiration. Ontogenesis of respiration.respiration.
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The Respiratory System
• Cells continually use O2 & release CO2
• Respiratory system designed for gas exchange
• Cardiovascular system transports gases in blood
• Failure of either system– rapid cell death from O2
starvation
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Respiratory System Anatomy• Nose• Pharynx = throat• Larynx = voicebox• Trachea = windpipe• Bronchi = airways• Lungs
- upper respiratory tract is above vocal cords– lower respiratory tract is below vocal cords
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External Nasal Structures
• Skin, nasal bones, & cartilage lined with mucous membrane
• Openings called external nares or nostrils
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Nose -- Internal Structures
• Large chamber within the skull• Roof is made up of ethmoid and floor is hard palate• Internal nares are openings to pharynx• Nasal septum is composed of bone & cartilage• Bony swelling or conchae on lateral walls
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Functions of the Nasal Structures
• Olfactory epithelium for sense of smell
• Pseudostratified ciliated columnar with goblet cells lines nasal cavity– warms air due to high vascularity– mucous moistens air & traps dust– cilia move mucous towards pharynx
• Paranasal sinuses open into nasal cavity– found in ethmoid, sphenoid, frontal & maxillary– lighten skull & resonate voice
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Pharynx • Muscular tube (5 inch long) hanging
from skull– skeletal muscle & mucous membrane
• Extends from internal nares to cricoid cartilage
• Functions– passageway for food and air– resonating chamber for speech production– tonsil (lymphatic tissue) in the walls
protects entryway into body• Distinct regions -- nasopharynx, oropharynx
and laryngopharynx
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Nasopharynx
• From internal nares to soft palate– openings of auditory (Eustachian) tubes from middle ear
cavity– adenoids or pharyngeal tonsil in roof
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Oropharynx
• From soft palate to hyoid bone– fauces is opening from mouth into oropharynx– palatine tonsils found in side walls, lingual tonsil in
tongue
• Common passageway for food & air
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Laryngopharynx
• Extends from hyoid bone to cricoid cartilage• Common passageway for food & air & ends as
esophagus inferiorly
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Larynx
• Cartilage & connective tissue tube• Anterior to C4 to C6• Constructed of 3 single & 3 paired cartilages
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Vocal Cords
• False vocal cords (ventricular folds) found above vocal folds (true vocal cords)
• True vocal cords attach to arytenoid cartilages
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Trachea and Bronchial Tree
• Full extent of airways is visible starting at the larynx and trachea
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Trachea
• Ciliated pseudostratified columnar epithelium • Hyaline cartilage as C-shaped structure closed by
trachealis muscle
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Bronchi and Bronchioles
• Primary bronchi supply each lung
• Secondary bronchi supply each lobe of the lungs (3 right + 2 left)
• Tertiary bronchi supply each bronchopulmonary segment
• Repeated branchings called bronchioles form a bronchial tree
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Pleural Membranes & Pleural Cavity
• Visceral pleura covers lungs --- parietal pleura lines ribcage & covers upper surface of diaphragm
• Pleural cavity is potential space between ribs & lungs
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Gross Anatomy of Lungs
• Base, apex (cupula), costal surface, cardiac notch• Oblique & horizontal fissure in right lung results in 3 lobes• Oblique fissure only in left lung produces 2 lobes
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Mediastinal Surface of Lungs
• Blood vessels & airways enter lungs at hilus• Forms root of lungs• Covered with pleura
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Structures within a segment of Lung• Branchings of single
arteriole, venule & bronchiole are wrapped by elastic CT
• Respiratory bronchiole– simple squamous
• Alveolar ducts surrounded by alveolar sacs & alveoli– sac is 2 or more alveoli
sharing a common opening
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Cells Types of the Alveoli
• Type I alveolar cells– simple squamous cells where gas exchange
occurs
• Type II alveolar cells (septal cells)– free surface has microvilli– secrete alveolar fluid containing surfactant
• Alveolar dust cells– wandering macrophages remove debris
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Alveolar-Capillary Membrane
• Respiratory membrane = 1/2 micron thick
• Exchange of gas from alveoli to blood
• 4 Layers of membrane to cross– alveolar epithelial wall of type I cells– alveolar epithelial basement membrane– capillary basement membrane– endothelial cells of capillary
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Details of Respiratory Membrane
• Find the 4 layers that comprise the respiratory membrane
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Double Blood Supply to the Lungs
• Deoxygenated blood arrives through pulmonary trunk from the right ventricle
• Bronchial arteries branch off of the aorta to supply oxygenated blood to lung tissue
• Venous drainage returns all blood to heart• Pulmonary blood vessels constrict in
response to low O2 levels so as not to pick up CO2 on there way through the lungs
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Respiration
• Respiration is exchange of primarily oxygen and carbon dioxide between atmosphere and human body
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Respiration: Steps
• Respiration is achieved in four steps1. Pulmonary ventilation: Inspiration + Expiration2. External respiration: Diffusion across alveolar-
capillary membrane3. Gas transport: Transport of O2 and CO24. Internal respiration: Exchange between ICF
and tissue capillary
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Breathing or Pulmonary Ventilation• Air moves into lungs when pressure
inside lungs is less than atmospheric pressure– How is this accomplished?
• Air moves out of the lungs when pressure inside lungs is greater than atmospheric pressure– How is this accomplished?
• Atmospheric pressure = 1 atm or 760mm Hg
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Boyle’s Law
• As the size of closed container decreases, pressure inside is increased
• The molecules have less wall area to strike so the pressure on each inch of area increases.
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Dimensions of the Chest Cavity
• Breathing in requires muscular activity & chest size changes• Contraction of the diaphragm flattens the dome and increases
the vertical dimension of the chest
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• Diaphragm moves 1 cm & ribs lifted by external intercostal muscles
• Intrathoracic pressure falls and 2-3 liters inhaled
Quiet Inspiration
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• Passive process with no muscle action• Elastic recoil & surface tension in alveoli pulls
inward• Alveolar pressure increases & air is pushed out
Quiet Expiration
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Intra-pleuralPressures
Helps keep parietal & visceral pleura stick together and alveoli inflated
•Always subatmospheric (756 mm Hg)•As diaphragm contracts intrapleural pressure decreases even more (754 mm Hg)
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Summary of Breathing
• Alveolar pressure decreases & air rushes in• Alveolar pressure increases & air rushes out
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External Respiration• Exchange of gas
between air & blood
• Gases diffuse from areas of high partial pressure to areas of low partial pressure
• Deoxygenated blood becomes oxygeneted
• Compare gas movements in pulmonary capillaries to tissue capillaries
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Internal Respiration• Exchange of gases
between blood & tissues• Conversion of oxygenated
blood into deoxygenated• Observe diffusion of O2
inward– at rest 25% of available
O2 enters cells– during exercise more O2
is absorbed• Observe diffusion of CO2
outward