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Anatomy and Physiology of Respiration

Respiratory System

Respiratory System

  • This is where gas exchange happens

  • The respiratory system work hand in hand with the circulatory to supply oxygen to the human body

  • This system helps the body absorb oxygen from the air so that the organs can function.

Upper Respiratory Tract

Lower Respiratory Tract

Nasal Passages​

Mouth

Pharynx

Trachea

Bronchi

Lungs

Upper & Lower Respiratory Tract
Cartilaginous Rings & Trachea

Cartilaginous Rings

  • Ridges in the trachea

  • Maintains the trachea from collapsing

Bronchioles

  • The bronchioles are the airways of the lung that branch off from the bronchi.

  • The bronchioles pump air into small sacs called alveoli, where oxygen and carbon dioxide are exchanged.

Trachea

  • A stiff, flexible tube that serves as a pathway fro air to enter the body.

  • It split into smaller sized airways call bronchioles, then these bronchioles will split into many generations.

Generations 

  • As the bronchioles narrow, they become terminal bronchioles, marking the end of the conducting zone of the respiratory system.

  • The process of how air is going to be replenished

Generations
Bronchioles

Epiglottis

  • An amount of cartilage located in the throat

  • Protects the airway 

  • It is a cartilaginous structure

  • It protects the laryngeal opening by covering it when we swallow

  • Allows air to pass through the larynx and lungs

Epiglottis

Lungs

  • End organ of the respiratory system

  • It inflates like a balloon as air enters

  • Removes oxygen from the air and passes it through the lungs

Diaphragm

  • Major muscle of the respiratory system

  • It is below the ribs, located below the lungs

  • Situated at subcostal area

  • During inspiration, diaphragm pulls the lungs downward.

  • The diaphragm also contracts and flattens during inspiration.

  • During expiration, diaphragm relaxes.

  • Allows the chest to expand and pull in air.

Lungs
Diaphragm & Thoracic cage

Thoracic cage

  • Also known as the chest cavity

  • Protects the ribs

  • During inhale inspiration it increases, and it relaxes as air is released from the lungs

Thoracic Cage
Abdominal musculature

Abdominal musculature

  • Pushing abdominal contents upwards by providing additional force during rapid expiration

Ribs & Intercostal muscles

Ribs

  • Main structure of the thoracic cage

  • Aids respiration

  • Attached by cartilages

  • Divided into 3 portions:

    • Upper (manubrium sternum)

    • Middle (sternal body)

    • Bottom (xiphoid process)

Intercostal muscles

  • Areas between ribs

  • Can be either internal or external

  • Aid in both inspiration and expiration

  • Shifts the ribs and chest cavity back to their initial position

Respiratory Muscles

Respiratory Muscles​

Inspiration

Expiration

Quiet Respiration

  • diaphragm

  • intercostals

Forced Respiration

  • diaphragm

  • intercostals

  • scalene

  • sternocleidomastoid

Quiet Respiration

  • no muscles

Forced Respiration

  • rectus abdominis

  • oblique

  • transverse abdominis

  • transversus thoracis

  • internal intercostals

Movement of Air
Pleural fluid

Movement of Air

  • lung attachment only at the hilum from the mediastinum

  • lung floats in the thoracic cavity, surrounded by thin layer of pleural fluid

Pleural fluid

  • located between the layers of the pleura

  • lubricates against thoracic cavity

  • reduces friction between the membranes when breathing

Alveolar Pressure
Pleura

Pleura

  • membrane that covers the lungs and lines the thoracic cavity

Pleural Pressure

Alveolar Pressure

  • Pressure inside the lung alveoli

  • Pressure in alveoli must fall slightly below atmospheric pressure to cause inward flow of air

Pleural Pressure

  • Pressure of fluid in the space between lung pleura and chest wall pleura

  • Slight negative pressure (-5 cm water) to have the suction needed to hold the lungs open to resting level

Stretchbility

Stretchability

  • The extent to which lungs expand for each unit increase in transpulmonary pressure

  • Normal total compliance of both lungs together in average human adult = 200ml/cm of water pressure

  • Elastic forces of lung tissue itself-determined by elastin and collagen fibers interwoven in lung parenchyma

  • In deflated lungs - contracted & kinked

  • In expanded lungs - they are stretched and unkinked

  • Elastic force caused by surface tension of fluid that lines the inside walls of the alveoli & there other lung spaces

  • Accounts for â…” of the total elastic forces in the normal lungs

Surface Tension
Surfatant

Surface Tension

  • Water molecules have a strong attraction for one another

  • Water surface is always attempting to contract (raindrops)

  • Tight contractile membrane of water molecules around the surface

  • In the alveoli, the water surface also attempts to contract

  • This attempts to force air out through the bronchi, causing alveoli to collapse

Surfactant

  • Surface active agents reduces surface tension

  • Secreted by surfactant secreting epithelial cells (10% of the surface area of the alveoli)

  • These cells are granular, constraints lipid inclusions = type II alveolar cells

  • Most important components:

    • Dipalmitoylphosphatidylcholin

    • surfactant apoproteins

    • calcium ions 

Pulmonary Capacities
Pulmonary Volumes

Pulmonary Volumes

  • The amount of air in the lungs at different stages of the respiratory cycle

  • Used to calculate capacity of lungs

 

Tidal Volume

  • volume of air inspired and expired with each normal breath. 

  • An average of 500ml for

       every breath a person

       takes

 

Inspiratory Reserve

Volume

  • extra volume of air that

       can be inspired over &

       above the normal tidal

       volume, usually about 3000ml. (you made an

       aside from tidal volume) 

 

Expiratory Reserve Volume

  • extra amount of air that can be expired by forceful expiration after the end of normal tidal expiration, normally amounts to 1100ml.

 

Residual Volume

  • volume of air remaining in the lungs after forceful expiration -  average of 1200ml.

Pulmonary Capacities

Inspiratory Capacity

  • amount of air a person can breathe beginning at the normal expiratory level and distending the lungs to the maximum amount 

  • Tidal Volume + Inspiratory Reserve Volume = Inspiratory Capacity

  • About 3500ml

 

Functional Residual Capacity 

  • amount of air that remains in the lungs at the end of normal expiration 

  • Expiratory Reserve Volume + Residual

       Volume = Functional Residual Capacity

  • About 2300ml

 

Vital Capacity

  • Maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent

  • Inspiratory Respiratory Volume + Tidal Volume + Expiratory Respiratory Volume = Vital Capacity

  • About 4600ml

 

Total Lung Capacity

  • Maximum volume to which lungs can be expanded with greatest possible inspiratory effort 

  • Vital Capacity + Residual Volume = Total Lung Capacity

  • About 5800ml

 

Left side of the lungs - oxygenated blood

Right Side of the lungs - deoxygenated blood

Minute Respiratory Volume

Minute Respiratory Volume

  • Total amount of air over into the respiratory passages each minute

  • Tidal Volume x Respiratory Rate = Minute Respiratory Volume

  • Averages about 6 liters/minute

Alveolar Ventilation
Dead Space

Alveolar Ventilation

  • Rate at which air reaches these areas
    - alveoli, alveolar sacs, alveolar ducts, respiratory bronchioles

  • Air travels by diffusion from terminal bronchioles into alveoli

  • Respiratory Rate x (Tidal Volume - Dead Space Volume) = Alveolar Ventilation

  • Average 4200ml

  • One of the major factors determining the concentrations of oxygen and carbon dioxide in the alveoli

Dead Space

  • Respiratory passages where no gas exchange taking place

  • Air in dead space expired first before any of the air in the alveoli reaches the atmosphere

  • Normal dead space is 150ml.

  • Deoxygenated blood

Functions of Respiratory Passageways

  • Trachea, Bronchi, & Bronchioles

    • trachea known as the first generation respiratory passageway & the 2 main right bronchi are 2nd gen

  • There are about 20-25 generations before air reaches alveoli

  • Multiple cartilage rings protect trachea from collapsing, and the other walls are composed of smooth muscles

  • Bronchioles are not prevented from collapsing, they expand by the same transpulmonary pressures that expand alveoli

  • The bronchioles are composed entirely of smooth muscles

2 Arms of the Autonomic Nervous System that innervates the Pulmonary System
Functions of Respiratory Passageways

2 Arms of the Autonomic Nervous System that innervates the Pulmonary System

  • SYMPATHETIC

    • norepinephrine & epinephrine results in dilatation of the bronchial tree because of the stimulation of the beta receptors

  • PARASYMPATHETIC

    • acetylcholine from vagus nerves, causes constriction of bronchioles

    • may be activated by reflexes that originate in the lung - noxious gases, dust, cigarette smoke, or respiratory infection

Local Factors

  • during allergic reaction 2 substances released

    • histamine

    • slow reactive substance of anaphylaxis

    • Originates from mast cells

Local Factors
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