Respiratory System

BIO 232

Anatomy and Physiology II

 

Respiration Includes Four Processes

•      Pulmonary ventilation - movement of air into and out of the lungs

•      External respiration - gas exchange between the blood and the air-filled chambers of the lungs

•      Transport of Respiratory gases - transport of O2 and CO2 between the lungs and the tissues of the body

•      Internal respiration - gas exchanges between systemic blood and the tissue cells

The Nose

•      2 nasal cavities

•      Olfactory receptors upper recesses

•      Lacrimal glands - drain into noise

•      Nasal cavities connect cranial cavities

•      Nasal cavities empty into nasopharynx

•    Auditory (Eustachian) tubes to middle ears

The External Nose

 

 

 

Upper Respiratory Tract

 

 

 

 

Pharynx & Larynx

•      Pharynx

•    Common passage for air & food

•      Larynx - voice box

•    Gateway to the trachea

•      Glottis - opening  to the trachea between vocal cords

Larynx

 

 

 

 

 

 

The Trachea

•      Trachea & esophagus meet at pharynx

•      Trachea lies in front of esophagus

•      C shaped cartilaginous rings

•      Cilia of epithelial lining

•      Keep lungs clean - sweep mucous upward

Bronchi (Air tubes)

•      Trachea divide into 2 bronchi

•      These branch to bronchioles

•      These terminate in alveoli

•      These make up the lungs

Respiratory Zone

 

 

 

 

Alveoli

•      300 million tiny air sacs

•      Polyhedral in shape

•      Large surface area

•      60-80 square meters - 760 square feet

Anatomy of Respiratory Membrane

 

 

 

 

 

 

Lung Surfactant

•      Surface tension (ST) of water is the result of attractive forces between water molecules near an air-water interface

•      Alveolar walls are coated with water molecules

•      The ST is always trying to reduce the size of the alveoli - if the film was pure water they would collapse

•      Surfactant  in the water film - interferes with the cohesiveness of water molecules - Reduces surface tension

•     Mixture of lipids & proteins

Respiratory Membrane & Capillaries

 

 

 

 

 

 

Thoracic Cavity

•     Diaphragm

•     Dome shaped muscle - divides body into two halves

•     Below - abdominal cavity

•     Above - thoracic cavity

Thoracic Cavity: Three Parts

•      Right Pleural cavity

•      Left Pleural cavity

•      Mediastinum

•    Heart, great vessels, trachea, esophagus, thymus & lymph nodes

•      Each lung enveloped by double layer pleural membranes (Pleurae)

•      Visceral Pleura & parietal pleura

Breathing or Ventilation

•      Movement of air into and out of the lungs occurs as a result of a pressure difference induced by changes in lung volume.

•      Intrapulmonary/Intrapleural pressure

•    Visceral & parietal membranes - normally stuck together

•    Intrapleural space - potential not real

Intrapulmonary & Intrapleural Pressures

•      Air enters lungs during inspiration because atmospheric pressure is greater than intrapulmonary or alveolar pressure

•      Note atmospheric pressure doesn’t change - intrapulmonary pressure must

•      Quiet inspiration - 4 mm Hg - subatmospheric or negative pressure

•      Expiration is the converse

Inspiration

•     Diaphragm - dome shaped when relaxed

•    During quiet inspiration the diaphragm contracts - lowers

•     External intercostal & parasternal muscles

•     Rib cage moves upward and outward

Inspiration

•    Thoracic cavity increase during inspiration - lungs expand

•    Air pressure within the alveoli lowers (negative pressure)

•    Immediately rebalanced - air rushes in

Forced Inspiration

•     Scalenes & pectoralis minor & even sternocleidomastoid participate

•     Contraction of these muscles elevates & stabilized the ribs

•    Stabilization of the ribs makes intercostals more effective

Expiration

•     Diaphragm relaxes

•     Abdominal organs displaced during inspiration rebound & push against diaphragm

•     Rib cage moves down & inward

•     Elastic lungs recoil - air is forced out

Forced Expiration

•     Internal intercostals contract (excluding interchondrial part)

•    Depresses rib cage

•     Abdominal muscle also aid

•    Oblique & transversus abdominus

•    They contract & force internal organs up against the diaphragm

Lung Volumes

•      Tidal Volume (TV)

•    Volume of gas inspired or expired in an unforced respiratory cycle

•      Inspiratory Reserve Volume (IRV)

•    Maximum volume of gas that can be inspired during forced                 breathing in addition to tidal volume

Lung Volumes

•      Expiratory Reserve Volume

•    Maximum volume expelled during forced breathing in addition to tidal volume

•      Residual Volume

•    Volume of gas remaining in the lungs after a maximum expiration

Lung Capacities

•      Inspiratory capacity (IC)

•     Maximum amount of gas that can be inspired at the end of a tidal expiration

•     Sum of tidal & respiratory reserves volumes

•      Functional residual capacity (FRC)

•     Combined residual and expiratory reserve volumes

•      Vital capacity (VC)

•     Sum of tidal, inspiratory reserve and expiratory reserves volumes

•      Anatomical dead space

•     Air that fills the conducting passageways (150 ml)

Respiratory Volumes and Capacities

Internal Respiration

•     O2 - from systemic Capillaries to cell of the body

•     CO2 - from cells to systemic capillaries

Oxygen Transport

•    Plasma - 0.3ml O2 / 100ml

•    Whole Blood - 20ml O2 /100 ml

Hemoglobin

•      2 - a polypeptide chains (141 AA long)

•      2 - b polypeptide chains (146 AA long)

•      Each polypeptide chain is combined with one heme group (iron containing)

•      Heme group binds O2  - See cooperative binding

•      About 250 -280 million Hb / RBC

•      Thus each RBC can carry over a million molecules of O2

Loading and Unloading Reactions

•      In the Lungs

•    Deoxyhemoglobin + O2 ฎ Oxyhemoglobin  (HbO2)       

•      In the Tissues

•      Oxyhemoglobin ฎ Deoxyhemoglobin  +  O2

Carbon Dioxide Transport

•     1. Dissolved CO2 (1/10 total)

•     2. Carbaminohemoglobin (1/5 total)

•     3. Bicarbonate (7/10 total)

•    CO2 + H2O H2CO3  H+ + HCO3 -

•    Carbonic anhydrase catalyzes the rxn

Chloride Shift

•     Production of bicarbonate occurs in RBCs

•     The H+ combines with Hb

•     H+ + Hb ฎ HbH

•      HCO3 - diffuses out  & Cl- are attracted in

•     In the lungs we get a reversed chloride shift

O2 Release & CO2 Pickup at the Tissues

O2 Pickup & CO2 Release in the Lungs

 

 

 

 

 

Medullary Respiratory Centers

•      Dorsal respiratory group (DRG)

•    Near the root of CN IX

•    Pacesetting center - inspiratory center

•      Ventral Respiratory group (VRG)

•    Network that extends within the ventral brain stem from the spinal cord tot he junction of the pons and medulla

•    Neurons involved in inspiration & expiration

•    Seems to be most involved in forced breathing

Pons Respiratory Centers

•     Controls medullary neurons

•     Pneumotaxic center

•    More superior center - continously transmits inhibitory signals to the inspiratory center of the medulla

•    Fine tune breathing rhythm & prevent overinflation of the lungs

Pons Respiratory Centers

•     Apneustic center

•    Appear to provide inspiratory drive by continously stimulating the medullary inspiratory center

•    Unless inhibited by the pneumotaxic center or sensory input from the lungs

•    Prolongs inspiration - also breath holding

Neural Pathways of Respiration

 

 

 

 

 

Neural & Chemical Influences