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Circulatory Systems

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					       Circulatory System
 Cardiovascular System = Heart,
  blood vessels, and blood
  -Transports H2O, nutrients, waste, O2,
  CO2, hormones, and immune cells.
  -Regulates heat, pH, and pressure.
  -Associated with lymphatic system.
 Lymphatic System = Lymphatic
  vessels, lymphatic hearts, & lymph
Human Cardiovascular
          Vascular Terms
 Anastamosis = intercommunication
  between separate vessels (net like).
 Portal System = vessels that carry
  blood from capillaries to capillaries.
 Sinus = region for “pooling” of fluids.
 Aortic arch = arterial arches that
  extend from ventral to dorsal between
  pharyngeal openings.
  Gnathostomes have 6 early in devel.
               Vascular
 Arteries = Large; carry blood away
  from heart
 Arterioles = Smaller; carry blood away
  from heart
 Capillaries = Very small; gas & nutrient
  exchange occur here
 Veinules = Smaller; carry blood to
  heart
 Veins = Large; carry blood to heart
         Vertebrate Blood
 Blood = connective tissue; cells (in
  vertebrates) in a water-based matrix.
 Plasma = matrix around blood cells.
  Transports: H2O, nutrients, waste,
  CO2, hormones
 Erythrocytes = Contain hemoglobin;
  transport O2; No nuclei in mammals.
 Leucocytes = Immune cells.
 Platelets = Cell fragments, involved in
  clotting after damage.
Vertebrate Blood




     Plasma
   Hematopoesis – Blood Devel.
 Hematopoesis = blood development.
 Blood islands form in splanchnic
  mesoderm in yolk sac = 1st site of
  hematopoesis (always nucleate cells).
  Early fetal human red blood cells have
  nuclei.
 Additional stem cells in splanchnic
  mesoderm around heart migrate to
  hematopoetic areas (spleen, kidneys, liver,
     Vascular Development
 Mostly from splanchnic mesoderm.
 Angiogenesis = blood vessel
  formation
 Blood islands in yolk sac merge to form
  vessels that then extend into rest of
  embryo.
  Cardiovascular system starts in yolk
  sac and spreads to rest of embryo.
Human Blood Islands
   Basic Chordate Arterial Circ.
 Blood moves from posterior and
  ventral to the pharynx (heart/sinus
  venosus)
 Anteriorly under the pharynx (ventral
  aorta)
 Dorsolaterally up through the
  pharynx (pharyngeal/aortic arches)
 Then to the body anteriorly and
  posteriorly from the dorsal pharynx
  (dorsal aorta).
   Lancelet Arterial Circulation
dorsal aorta (paired - median)




                      sinus venosus (median)
                 ventral aorta (median)
Lancelet Venous Circulation

Anterior & posterior cardinal veins (paired)




                   sinus venosus (median)
hepatic vein (median)
 Lancelet Circulation



                                        anterior
ventral   dorsal                        cardinal
 aorta    aorta                           vein
                   common
                   cardinal
 s.v.                vein      s.v.
                                        posterior
                                        cardinal
    dorsal                    hepatic
                                          vein
    aorta                      vein
Basic Amniote Circulation
    Early Human Embryo Arterial
  left & right
 dorsal aortas



aortic                       IV
arch II                III


aortic
arch I                                                 umbilical
     ventral aorta            heart
                                                        artery
     (truncus arteriosus) sinus venosus
                              atrium
                             ventricle     vitelline
                           bulbis cordis    artery
  Early Human Embryo Arterial
 left & right
dorsal aortas



                              IV VI
                          III



                                                  umbilical
   ventral aorta             heart
                                                   artery
   (truncus arteriosus)
                                      vitelline
                                       artery
Early Human Embryo Arterial

                              descending aorta

                           IV VI pulmonary
                       III
         carotids



                                                   umbilical
ventral aorta            heart
                                                    artery
(truncus arteriosus)
                                       vitelline
                                        artery
Early Human Embryo Arterial
          Embryonic Arteries

                        I
                       II
  ventral aorta
                       III
                       IV
                             V
                       VI
  dorsal aorta
                   HEART




I II III IV V VI
      Human Embryonic Arteries
external carotid
 internal carotid
                         I
common carotid          II
                        III
                              aortic arch
                        IV
     subclavian         VI

 pulmonary artery             ductus arteriosus
                    HEART
                                  (before birth)



                              descending aorta
Human Embryonic Arteries
Human Aortic Arches
Human Fetal Circulation
                    Upper Left
                     Arch VI
   Early Human Embryo Circulation
 left & right anterior                          left & right posterior
    cardinal veins                                  cardinal veins

left & right
 common
  cardinal
    veins


      ventral aorta         heart
     (truncus arteriosus) sinus venosus
                              atrium
                             ventricle      vitelline       allantoic
                           bulbis cordis   (hepatic)     (umbilical) veins
                                              veins
 Early Human Embryo Circulation
                      superior
left & right anterior               left & right posterior
                       vena
   cardinal veins                       cardinal veins
                        cava
                                           azygous vein

          jugular                   inferior
           veins                      vena
                                      cava
                             hepatic
                     heart
                              portal
                      hepatic vein
                               vitelline          allantoic
                       vein
                              (hepatic)        (umbilical) veins
                                 veins
Human Anterior Venous
    Development
Basic Vertebrate Circulation
     Blood Vessel Structure
 Endothelium = simple squamous
  epithelium lining inside of blood
  vessels (tunica intima)
 Tunica externa = fibrous connective
  tissue surrounding the outside of the
  vessel
 Tunica media = between the tunica
  intima and tunica externa; elastic
  connective tissue and/or smooth
  muscle.
        Vessel Structure
 Arteries = Large; carry blood away
  from heart;
  thick tunica media composed
  primarily of smooth muscle;
  accommodate high blood pressure
 Capillaries = Very small; gas &
  nutrient exchange occur here;
  lack tunica media and tunica externa
         Vessel Structure
 Veins = Vessels that carry blood to
 the heart; thin tunica media made
 primarily of connective tissue
 one-way valves promote the return
 of blood under low pressure
Vertebrate Vessels

vein    tunica intima
                        artery
       (endothelium)




         capillary
Adult Human Arterial system
Adult Human Arterial system
      external carotid    subclavian
       internal carotid   axillary
     common carotid
             vertebral          humeral circumflex
                                 internal thoracic
                aorta*          lateral thoracic
              coeliac*          brachial
 superior mesenteric*          deep brachial
                 renal         radial
              gonadal          ulnar
  inferior mesenteric*         common iliac
                               external iliac
                               internal iliac
                                femoral circumflex
                               deep femoral

                              femoral


                             popliteal
                             anterior tibial
                             posterior tibial
Pulse Points
Carotid & Radial Pulse Points
Human Venous System




Azygous vein
Human Venous System
Human Arm Venous System
Human Leg Venous System
Human Varicose veins
          Hematopoesis
 In non-amniotes occurs primarily in
  the spleen, kidneys, and liver.
  Especially the spleen.
 Hagfishes, lampreys, & lungfishes =
  no spleen
 In amniotes occurs in bone marrow
  (especially in humans and other
  mammals) as well as in other tissues.
  No bone marrow in birds.
Subphylum Vertebrata



                                    *



                    spleen
                                        hemato-


                    lost
                                        poesis in
                                        marrow

              discrete spleen

blood cells            *erythrocytes lack nuclei
Lancelet Circulation
        Vertebrate Circulation
            dorsal
            aorta




                               Iliac
      ventral                 artery
       aorta
                 subclavian
external
            heart artery
carotid
        Vertebrate Circulation
      anterior & posterior
         cardinal veins      renal portal
jugulars



       heart                        hepatic
                                     portal
                   lateral
      subclavian abdominal iliac
         vein       vein   vein
          Aortic Arches
 Gnathostomes = Arch I lost in adults;
  6 arches early in development
 Sarcopterygiians = Pulmonary arteries
  from arch VI
 Tetrapods & Actinopts. = Arch II lost
 Amniotes = Arch V lost
 Mammals = left Arch IV forms aorta;
  right Arch IV forms base of subclavian
 Birds = right Arch IV forms aorta
Gnathostome Embryo Aortic Arches
                          external    internal
                           carotid     carotid
                    I
                   II
                   III   ventral      dorsal
                   IV     aorta       aorta
                   V
                   VI
I II III IV V VI
                         heart


                             dorsal
                             aorta
Chondrichthyan Aortic Arches

                    I
                   II
                   III
                   IV
                   V
                   VI
I II III IV V VI
                         heart
       Teleost Aortic Arches

                    I
                   II
                   III
                   IV
                   V
                   VI
I II III IV V VI
                         heart
      Lungfish Aortic Arches

                    I
                   II
                   III
                   IV
                   V
                   VI
I II III IV V VI
                         heart

                                 pulmonary
                                   artery
    Amphibian Aortic Arches
                           external   internal
                            carotid    carotid
                      I
                     II
                     III

                     IV
                     V
                     VI
I II III   IV V VI
                            heart

                                      pulmonary
                                        artery
           Lizard Aortic Arches
                           external   internal
                            carotid    carotid
                      I
                     II
                     III

                     IV
                     V
                     VI
I II III   IV V VI
                            heart

                                      pulmonary
                                        artery
           Bird Aortic Arches
                           external   internal
                            carotid    carotid
                      I
                     II
                     III

                     IV
                     V
                     VI
I II III   IV V VI
                            heart

                                      pulmonary
                                        artery
    Lepidosaur Aortic Arches
                           external   internal
                            carotid    carotid
                      I
                     II
                     III

                     IV
                     V
                     VI
I II III   IV V VI
                            heart

                                      pulmonary
                                        artery
    Mammalian Aortic Arches
                           external   internal
                            carotid    carotid
                      I
                     II
                     III

                     IV
                     V
                     VI
I II III   IV V VI
                            heart

                                      pulmonary
                                        artery
Subphylum Vertebrata


   arch II lost
                                               arch V
                                               lost
                                     arch II
                                     lost
                             arch VI
                             forms pulmonary
                  arch I     connection
                  lost;
                  6 arches form in development
          Amniota




left arch IV         right arch
forms aorta; right   IV forms
arch IV forms        aorta
right subclavian
Gnathostome Adult Aortic Arches

Aortic Arch   Chondrichthys   Actinopterygii    lungfishes
     I             lost            lost             lost
    II          gill arch          lost          gill arch
    III         gill arch       gill arch        gill arch
    IV          gill arch       gill arch        gill arch
    V           gill arch       gill arch        gill arch
    VI          gill arch       gill arch          arch
                                               & pulmonary
                                                  artery
Gnathostome Adult Aortic Arches
Aortic Arch    amphibians             turtles            lizards
     I              lost               lost               lost
    II              lost               lost               lost
    III           common              common             common
                  carotids            carotids           carotids
    IV        l. and r. aortic    l. and r. aortic   l. and r. aortic
                   arches              arches             arches
    V            aortic arch            lost               lost
                (lost in frogs)
    VI        aortic arch &        pulmonary          pulmonary
               pulmonary             artery             artery
                 artery
Gnathostome Adult Aortic Arches
Aortic Arch   crocodilians           birds           Mammalia
     I             lost               lost              lost
    II             lost               lost              lost
    III         common           com. carotids /      common
                carotids           subclavian      carotids & ext.
                                     bases          carotid base
    IV        l. and r. aortic       l. lost           l. aorta
                  arches            r. aorta       r. subclavian
    V              lost                lost               lost
    VI         pulmonary           pulmonary        pulmonary
                 artery              artery           artery
          Venous System
 Gnathostomes = renal portal vein
 Tetrapods = inferior vena cava from
  right hepatic; anterior cardinal veins
  form internal & external jugular veins
 Mammals = inferior vena cava
  connects to & replaces renal portal
 Some Mammals (humans, cats, etc.) =
  lose the left anterior cardinal vein (the
 right anterior cardinal vein = superior vena
 cava)
  Venous System
                    anterior
           sinus    cardinal
          venosus
                     common
hepatic              cardinal
 vein
hepatic
portal              posterior
                    cardinal
Shark Venous System
   internal   anterior
   jugular    cardinal
 subclavian
                common
 hepatic        cardinal
  vein
              posterior
 hepatic      cardinal
 portal


              renal
              portal
Amphibian Venous System
      external   internal
      jugular    jugular
                             anterior
                             cardinal
   subclavian
                              common
   hepatic                    cardinal
    vein
                            posterior
   hepatic                  cardinal
   portal
                                posterior
                                vena cava
                            renal
                            portal
                               iliac
Reptile Venous System
     external   internal
     jugular    jugular
                             anterior
                             cardinal
  subclavian
  hepatic
   vein
  hepatic
  portal                       posterior
                               vena cava

                           renal
                           portal
                              iliac
Mammal Venous System
     external   internal
     jugular    jugular
                           anterior
                           cardinal
  subclavian
  hepatic
   vein
  hepatic
  portal                       posterior
                               vena cava
                           renal
                            vein


                             iliac
Gnathostome Venous System
  Veins       Chondrichthys    Actinopterygii    lungfishes
 ant. card.    ant. cardinal    ant. cardinal    ant. cardinal
com. card.    com. cardinal    com. cardinal    com. cardinal
post. card.   post. cardinal   post. cardinal  post. cardinal
                                              (rt. = posterior
                                               “vena cava”)
 hepatic      2 hepatic veins 2 hepatic veins 2 hepatic veins
hep. portal   hepatic portal   hepatic portal   hepatic portal
renal port.    renal portal     renal portal     renal portal
Gnathostome Venous System
   Veins       amphibians            turtles       Lepidosauria
ant. card.     ant. cardinal     ant. cardinal     ant. cardinal
              (jugular vein & (jugular vein & (jugular vein &
              brachiocephalics) brachiocephalics) brachiocephalics)
com. card.    com. cardinal   com. cardinal com. cardinal
              (s. vena cavas)  (s. vena cavas) (s. vena cavas)
post. card. post. cardinal          l. lost         l. lost
                             r. azygous vein r. azygous vein
 hepatic     l. hepatic vein l. hepatic vein l. hepatic vein
            r. p. vena cava r. p. vena cava r. p. vena cava
hep. portal hepatic portal hepatic portal hepatic portal
renal port.    renal portal       renal portal      renal portal
Gnathostome Venous System
   Veins       crocodilians         birds          Mammalia
ant. card.  ant. cardinal     ant. cardinal     ant. cardinal
           (jugular vein & (jugular vein & (jugular vein &
           brachiocephalics) brachiocephalics) brachiocephalics)
com. card. com. cardinal com. cardinal com. cardinal
            (s. vena cavas)   (s. vena cavas)   (s. vena cavas
                                                -left s. v. c. lost in some)

post. card.         l. lost         l. lost         l. lost
            r. azygous vein r. azygous vein r. azygous vein
 hepatic     l. hepatic vein l. hepatic vein l. hepatic vein
             r. i. vena cava r. i. vena cava r. i. vena cava
hep. portal hepatic portal hepatic portal hepatic portal
renal port.    renal portal      renal portal             lost
         Hepatic Portal Vein
 Vein from yolk sac to heart (vitelline vein)
 impinged on by hepatic diverticulum and
 forms hepatic capillaries.

                      gut

                                    liver (with hepatic veins)
           heart


                    hepatic portal vein
                                           vitelline vein
                                           (from yolk sac)
Subphylum Vertebrata



                              *

                            jugular veins;
                             rt. hepatic =
                            posterior
                            vena cava
       renal portal; subclavians
                      *renal portal lost
                  Heart
 Heart = Muscular pump, moves blood
  via rhythmic contraction.
 Contraction involuntary & initiated within
  the heart. (not-neuronal)
  Modified branching (cardiac) muscle
  cells transmit contraction signal.
 Chamber = Cavity for blood collection
  separated by valves
 Valves = Flaps of tissue that prevent
  back-flow of fluid (in this case blood)
    Human Heart Development
 Formed from splanchnic mesoderm.
 Endocardial tissue = forms simple
  squamous epithelium that lines the heart
  chambers and forms the heart valves
 Myocardial = epithelium forms heart muscle
 Hollow endocardial primordia form by
  splanchnic mesoderm ingression, then fuse to
  form a the endocardium (endothelium).
 Epithelial splanchnic mesoderm surrounds
  the endocardium forming the cardiac muscle
  of the myocardium.
Human Heart Development




                    endocardium

                    myocardium
Human Heart Development


                (ventral aorta)




                Sinus Venosus
    Heart Chambers & Valves
 Sinus venosus = slightly muscular chamber;
 receives blood from cardinal veins = sinoatrial node
 (“pacemaker”) in amniotes.
 Sinoatrial valve = between s.v. & atrium.
 Atrium = slightly muscular chamber.
 Atrioventricular valve = between atrium &
 ventricle.
 Ventricle = highly muscular chamber.
 Conus arteriosus/ Bulbus arteriosus =
 chamber after ventricle (muscular with valves
 = conus; elastic, no valves = bulbus ;
 embryonic = bulbis cordis)
Human Heart Development
   Human Heart Development
 Sinus Venosus lost except some cells
  that become the sinoatrial node
  (“pacemaker”)
 Sinoatrial valve lost.
 Atrium divides into right and left.
 Atrioventricular valve divides to form
  (right) tricuspid and (left) bicuspid/mitral
  valves
 Ventricle divides into right and left.
   Human Heart Development
 Bulbis cordis lost.
 Ventral aorta (truncus arteriosus)
 divides to become
 - (left) ascending aorta that will
 maintain connection to aortic arches III
 & IV and
 - (right) pulmonary trunk artery that
 will maintain connection to aortic arch
 VI.
Human Heart Blood Flow
Human Heart Blood Flow
Heart Chambers & Valves
Heart Position/Stethoscope
Blood Flow From Heart
          high oxygen




 low oxygen
Heart Chambers & Valves




                     Teleost
         Heart Chambers
 Sarcopterygiians = at least partially
  developed interatrial septum
 Tetrapods = complete interatrial
  septum
 Amniotes = conus arteriosus lost
  during devel; sinus venosus incorp.
  into right atrium; at least partially
  developed interventricular septum
 Mammals & Archosaurs = complete
  interventricular septum
Heart Chambers & Valves
Heart Chambers & Valves
Subphylum Vertebrata



    arteriosus
    bulbus


                                    complete
                                    interatrial
                                    septum
                 partial interatrial
                 septum
      heart (sinus venosus, atrium, ventricle,
      conus arteriosus)
          Amniota




complete                        complete
interventricular                interventricular
septum                          septum
            conus arteriosus lost in adult;
            incomplete interventricular septum;
            sinus venosus lost (in rt. atrium)
            Gnathostome Heart
Chambers     Chondrichthys   Actinopterygii      lungfishes
 Sinus       sinus venosus   sinus venosus     sinus venosus
Venosus
 Atrium         atrium           atrium        atrium (partially
                                                 l.-r. divided)
Ventricle      ventricle        venticle          ventricle
  Conus          conus           bulbus            conus
Arteriosus     arteriosus    arteriosus (not     arteriosus
                               muscular)
             Gnathostome Heart
Chambers      amphibians           lizards                  turtles
 Sinus       sinus venosus   sinoatrial node sinoatrial node
Venosus                      (incorp. in rt. atrium) (incorp. in rt. atrium)

 Atrium        left atrium      left atrium              left atrium
              right atrium     right atrium             right atrium
Ventricle      ventricle     ventricle (partial. ventricle (partial.
                             left-right divided)      left-right divided)
  Conus         conus                lost                     lost
Arteriosus    arteriosus
             Gnathostome Heart
Chambers       crocodilians                 birds                Mammalia
 Sinus       sinoatrial node sinoatrial node sinoatrial node
Venosus      (incorp. in rt. atrium) (incorp. in rt. atrium) (incorp. in rt. atrium)

 Atrium         left atrium              left atrium             left atrium
               right atrium             right atrium            right atrium
Ventricle      left ventricle          left ventricle           left ventricle
              right ventricle         right ventricle          right ventricle
                (connected by
             foramen of Panizza)
  Conus              lost                    lost                     lost
Arteriosus
        Lymphatic System
 Plasma in capillaries is forced into the
  tissues by blood pressure.
 Edema = swelling of tissues due to
  accumulation of fluid (plasma/lymph).
 Usually, edema is avoided because…
  plasma in tissues diffuses into blind
  lymphatic capillaries and is called
  lymph.
Lymphatic System

   artery


            capillaries


  vein
       Lymphatic System
 Lymphangitis = inflamation of a lymph
 vessel. (ROOT WORDS)
 Lymphangitis of the vessel indicated by
 the arrow caused the edema in the
 middle finger.
         Lymphatic System
 Lymph vessels = thin walled vessels
  with valves (similar in structure to veins,
  but with weak contractile ability); return
  lymph to venous system.
 Lymph nodes (lymphatic cisterns) =
  expanded lymph vessels filled with
  connective tissue and leukocytes.
  Immunological filters.
 Lacteals = lymph vessels in villi of the
  jejuno-ileum (small intestine) absorb fats.
Lymph Vessel
Lymph Node & Lg. Vessel
    (in mesentary proper)
Human Cephalic Lymph System
Human Lymphatic System
         Lymphatic System
 Contractile lymph vessels exist in most
 vertebrates (Form localized Lymph Hearts in
 hagfishes, lungfishes, amphibians, turtles, liz.
 & snakes, & ostriches+related birds)
 Lacteals = lymph vessels in the intestinal
  villi – Only in TETRAPODS.
 Lymph nodes / sacs / cisterns =
  expanded lymph vessels filled with
  connective tissue and leukocytes. Only in
  AMNIOTES.
Human Lymphatic System
Subphylum Vertebrata




                        lymph
                        nodes &
                        cisterns

                 lacteals
 General Respiratory Systems
 Ventilation = movement of air or water
  across a respiratory surface.
 Apnea = cessation of ventilation
 Unidirectional ventilation = air/water
  moves 1 direction over resp. surface
 Bidirectional ventilation = air/water
  moves 2 directions over resp. surface.
  (tidal)
 Concurrent & Counter current
  exchange
                Concurrent
          Same Direction Current



    water or air

        blood


from body (heart)                  to body
          Counter Current
          Counter Current System



   water or air


                          blood


to body                  from body (heart)
Human Trachea & Lung
   Development
   Human Respiratory System

       nasal cavity
         pharynx
          larynx
         trachea
        bronchus
  in
lung    bronchiole
         alveolus
Human Respiratory System
Human Larynx
Human Lungs
Human Ventilation
Aquatic Respiratory Structures
 Skin is a significant respiratory surface
  in many NON-amniotes.
 Gills = aquatic pharyngeal respiratory
  surfaces. (Internal = within pharynx;
  External = protrude from pharynx)
            salamander (axolotl)




 reedfish                          lungfish
Internal Gills
 Chondrichthys




       Actinopterygii
                  Gills
 Gill = bony pharyngeal arch and two sets
  of filaments.
 Absent in Amniotes and adult
  Lissamphibians
 Each filament bears many lamellae
  (small, flat projections) & blood passes
  through capillaries in the lamellae.
 Blood movement through lamellae sets
  up a counter current system.
Gills
Counter Current
Gill Filament

           afferent
                      lamella




efferent
       Lungs/Swimbladders
 Lung(s) = aerial gut diverticulum
  respiratory surface. (Osteichthys)
  In fishes called swimbladder & usually
  used for buoyancy as well.
 Pneumatic duct = Connection to
  digestive tract in Actinopterygii & Dipnoi.
  Trachea (in Tetrapods) is a pneumatic
  duct held open with cartilage rings.
      Lungs/Swimbladders
 Respiratory lungs/swimbladders are
  often compartmentalized.
 Faveoli = non-mammal lung chambers.
 Alveoli = rounded mammal lung
  chambers.
Lungs/Swimbladders (Osteichthys)
 Ancestral lungs/swimbladders:
  Ventral trachea/pneumatic duct.
  Two “lungs”
 Swimbladder of non-reedfish
  actinopterygiians:
  Dorsal pneumatic duct.
  One lung dorsal to esophagus.
  (Pneumatic duct lost in some teleosts.)
Lungs/Swimbladders


              lungfish
 Amia calva




                Polypterus
   carp




                salamander
    bass
Craniate Respiration




                             alveoli
                                            gill
                                            filaments
                                            lost

                  lungs                trachea
                  (swimbladder)        (with
                                       cartilage
                                       “rings”)
respiratory gills with filaments
Class Actinopterygii




          single dorsal lung with
          dorsal connection to
          digestive tract
Aerial Respiratory Modifications
 Ancestrally - amphibians & “fishes”
  - “Swallow” air – push into lungs
  - Elastic lungs recoil to push air out.
 Prehepatic diaphragm (mammals)
  - Negative pressure pulls air into lungs
  - Body cavity contraction pushes air out.
 Posthepatic diaphragm (crocodilians)
  - Negative pressure pulls air into lungs
  - Liver pushes air out of lungs.
“swallow” air    Ventilation
                              prehepatic




                posthepatic
          Bird Respiration
 Parabronchi (birds) = one-way,
  passageways through the lung faveoli.
 Lungs not very compressible.
 Air Sacs (birds) = membranous sacs
  for containing air (9 off of each lung)
 Air moved by expansion & contraction
  of air sacs.
 Countercurrent, constant flow of O2 rich
  air over capillaries even when exhaling.
Avian Lungs
Avian Inhalation
Avian Exhalation
Avian Respiration
         Amniota



                          *


                          air sacs;
prehepatic
                          parabronchi
diaphragm

              * posthepatic diaphragm

				
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posted:4/17/2013
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