Respiration. Ontogenesis of respiration. Respiration. Ontogenesis of respiration

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

04/20/23 Shina Alagia 3

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


External Nasal Structures

• Skin, nasal bones, & cartilage lined with mucous membrane

• Openings called external nares or nostrils


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


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


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


Nasopharynx

• From internal nares to soft palate– openings of auditory (Eustachian) tubes from middle ear

cavity– adenoids or pharyngeal tonsil in roof


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


Laryngopharynx

• Extends from hyoid bone to cricoid cartilage• Common passageway for food & air & ends as

esophagus inferiorly


Larynx

• Cartilage & connective tissue tube• Anterior to C4 to C6• Constructed of 3 single & 3 paired cartilages


Vocal Cords

• False vocal cords (ventricular folds) found above vocal folds (true vocal cords)

• True vocal cords attach to arytenoid cartilages


Trachea and Bronchial Tree

• Full extent of airways is visible starting at the larynx and trachea


Trachea

• Ciliated pseudostratified columnar epithelium • Hyaline cartilage as C-shaped structure closed by

trachealis muscle


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


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


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


Mediastinal Surface of Lungs

• Blood vessels & airways enter lungs at hilus• Forms root of lungs• Covered with pleura


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


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


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


Details of Respiratory Membrane

• Find the 4 layers that comprise the respiratory membrane


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


Respiration

• Respiration is exchange of primarily oxygen and carbon dioxide between atmosphere and human body


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


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


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.


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


• Diaphragm moves 1 cm & ribs lifted by external intercostal muscles

• Intrathoracic pressure falls and 2-3 liters inhaled

Quiet Inspiration


• Passive process with no muscle action• Elastic recoil & surface tension in alveoli pulls

inward• Alveolar pressure increases & air is pushed out

Quiet Expiration


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)


Summary of Breathing

• Alveolar pressure decreases & air rushes in• Alveolar pressure increases & air rushes out


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


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

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Respiration. Ontogenesis of respiration. Respiration. Ontogenesis of respiration