• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Circulatory system

Circulatory system






Total Views
Views on SlideShare
Embed Views



0 Embeds 0

No embeds


Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
Post Comment
Edit your comment

    Circulatory system Circulatory system Presentation Transcript

    • Circulatory System
      • The circulatory system of craniates consists
      • + heart + capillaries or sinusoids
      • + arteries + blood vascular system
      • + veins or venous sinuses + lymphatic system
      • The blood is an important agent for circulation:
      • 1. Carries oxygen, nutrients, hormones, waste products
      • and other substances
      • 2. Conducts heat
      • Lymph channels – terminate in venous channels
        • Collect interstitial fluids and lipids
        • - short section where capillary emerges from arteriole
        • has smooth muscle fibers that given an adequate neural or hormonal stimulus close off entrance of capillary bed
        • ex: blushing of skin
      - connects arterioles and venules directly - - assure uninterrupted circulation between arterial and venous sides of capillary beds when other capillaries are constricted
      • -system of veins bounded by capillary beds
      • Renal portal system
      • Hepatic portal system
      • Hypophyseal portal system
      Arteries Veins or Venous Sinuses Capillaries or Sinusoids Function Carry blood away from heart Blood towards the heart Site of gas exchange Structure Muscular and elastic walls  can distend Less muscle and elastic tissue, more fibrous tissue than arteries  less distention Endothelium; some mesenchyme & smooth muscle fibers Lumen diameter = size of RBC Precapillary sphincter Capillary shunts Special terms Smallest: Arterioles (diameter <=0.3mm) – dilate and constrict reflexly thereby assist in regulating blood pressure Smallest: Venules – provide direct connection to capillaries Portal system Capillary bed or network – all individual capillaries served by a single arteriole Covering Loose connective tissue adventitia Loose connective tissue adventitia
    • Structure of Blood Vessels
    • Portal Systems Hepatic portal system Renal portal system Renal portal system Hepatic portal system Hypophyseal portal system Blood from capillaries of the tail digestive tract, pancreas and spleen Hypothalamus (contains pituitary regulating hormones) To capillaries of kidney liver Adenohypophysis Continue to Heart Heart Heart
    • Pathway of Blood Arteries Arterioles (Precapillary sphincter) Capillaries (capillary shunts) Venules Veins
    • Development
      • Mechanisms of vessel formation
        • Vascularization
          • Process of vessel formation from endothelial precursors with the formation of vessels potentially occurring prior to the onset of blood flow
          • May be an inductive interaction with the surrounding tissue (notochord and the axial dorsal aorta)
        • Angiogenesis
          • The remodeling of existing vessels and can occur both prenatally and postnatally
    • Angiognesis
    • Blood Serum-plasma without fibrinogen (clotting substance)
      • Hemopoiesis
      • -formation of blood cells
      • -earliest sign: large number of blood islands (produce hemocytoblasts, which are stem cells from which all later blood cells arise)
      • -blood islands also have extensive network of endothelial-lined spaces. These connect to other blood channels to establish an early circulatory system
      • Hemopoiesis (cont.)
      • -descendants of hemocytoblasts form in the tissues within the body
      Deteriorating these formed elements in the blood of craniates are done by Macrophages through phagocytosis and amboeboid WBCs in any traumatized tissue of the body Hemopoietic source Product Liver, kidney, spleen Craniate RBCs spleen Craniate WBCs Bone marrow Amniote RBCs and Granular Leukocytes Intestinal submucosa Teleost granular leukocytes Lymphatic tissues lymphoctes
    • Formed Elements
    • Formed Elements Lifespan: 3-4 months Number: 25 trillion Reduces hemoglobin- when oxygen is freed
    • Formed Elements
    • Formed Elements Platelets -participate with fibrinogen in the clotting of blood -tiny fragments of stem cells (megakaryotes) found in the bone marrow
    • Heart and Its Evolution
      • Muscular pump that occupies pericardial cavity
      Heart Arteries Walls Endocardium Myocardium Epicardium Intima Media Adventitia Muscle Cardiac Smooth
    • Heart
      • Visceral pericardium – lying on epicardium;
      • = visceral pleuroperitoneum
      • Pericardial cavity – space between pericardia
      • Coronary arteries and veins
    • Single Circuit Blood passes from heart to the gills From gills directly to all parts of the body Systemic circuit – oxygenated blood to organs and returns oxygen depleted blood to the heart Pulmonary circuit – deoxygenated blood from heart to lungs Returns to the heart Double Circuit Fishes Craniates who abandoned gills
    • Hearts of Gill-Breathing Fishes
      • 4 chambers
        • Sinus venosus
          • Sinoatrial aperture
        • Atrium
          • Atrioventricular aperture
        • Ventricle
          • Semilunar valves
        • Conus arteriosus (truncus arteriosus) or Bulbus arteriosus
      Except dipnoans
    • 1. Ventricular contraction – creates suction 2. Filling of sinus venosus 3. Atrium relaxes – blood from sinus venosus  valves  sinoatrial aperture  atrium Atrial contraction  atrioventricular septum  valves  relaxing ventricle Conal constriction
    • Hearts of Dipnoans and Amphibians
      • Modifications in heart – correlated with aerial respiration
        • Separates oxygenated blood returning from swim bladders or lungs from deoxygenated blood from other organs
        • Establishment of a partial or complete interatrial septum  right (O 2 poor) and left atrial (O 2 rich) chambers
        • Formation of a partial interventricular septum (dipnoans & Siren) or ventricular trabeculae (amphibians)
            • - Fxn: maintain separation of oxygenated and unoxygenated blood
          • - trabeculae – shelves or ridges projecting from the ventricular wall into the chamber and running mostly cephalo caudad
        • Formation of a spiral valve in the conus arteriosus
        • -valves direct O 2 poorblood into aortic arches that lead to gills or lungs and channelize oxygenated blood into arches that supply other organs
        • 4. Shortened ventral aorta
            • - Blood moves from conus arteriosus directly to appropriate vessels
    • Hearts of Amniotes
      • 2 atria, 2 ventricles
        • + 1 ventricular chamber in turtles and squamates
        • Sinus venosus in birds and mammals  sinoatrial (SA) node
        • Sinus venosus in crocodiles is partially incorporated to wall of right atrium
    • Hearts of Amniotes
      • Interatrial septum – completely separates right and left atria
        • Interarterial foramen or foramen ovale – confluence of right and left atria during embryonic development; closes during birth, becomes fossa ovalis in medial wall of right atrium
      • Sinus venosus  right atrium
      • Pulmonary veins  left atrium
      • One-way valves guard the passageways from atria into ventricles.
      • Each valves consist of one or more fibrous flaps or cusps, connected chiefly in mammals by tendonous cords (chordae tendineae) to papillary muscles that project from the ventricular walls
    • Heart valves
    • Innervation of the Heart
      • Hagfish heart – no external innervation; only modified intrinsic cells that respond to circulatory signals
    • Innervation of the Heart
      • Vertebrate heart
        • Autogenic – require no external neural stimulus  only to produce a regular beat that can be increased or slowed reflexly by CNS
        • Pulsation depends on appropriate concentrations of certain electrolytes (Na, K, Ca ions)
        • Purkinje fibers – intrinsic conduction system composed of atypical cardiac muscle that constitute a conduction network with high conductile competence
    • Innervation of the Heart
    • ARTERIAL CHANNELS AND THEIR MODIFICATIONS Circulatory System ARTERIAL CHANNELS supply most organs with oxygenated blood, although they carry deoxygenated blood to respiratory organs
      • (paired in early embryogenesis) – emerges from the heart and passes forward beneath the pharynx
      • (paired above the pharynx only) – extends caudad in the roof of the coelom
      • SIX PAIRS OF AORTIC ARCHES – connects the ventral aorta with the dorsal aorta
      FIGURE 14.16 Page 327
      • SQUALUS
      • VENTRAL AORTA extends forward under the pharynx
      • and connects with the developing aortic arch (fig. 14.17)
      • FIRST TO DEVELOP aortic arches in mandibular arch
      • posttrematic arteries -> sprout crosstrunks
      • crosstrunks = grows caudad in the holobranch and by
      • further budding establish the last four pretrematic
      • arteries
      AORTIC ARCH OF FISHES FIGURE 14.17 Page 328 AORTIC ARCH FATE 1 st pair (before the 6 th pair appears) ventral segments – disappears dorsal segments – efferent spiracular arteries 2 nd pair first pretrematic arteries 3 rd pair posttrematic arteries 4 th pair posttrematic arteries 5 th pair posttrematic arteries 6 th pair posttrematic arteries
      • SQUALUS
      • Aortic Arches II to VI becomes occluded at one
      • Site. (broken lines in fig. 14.17(a))
      • -> Afferent Branchial Arteries – segments ventral to the occlusion
      • -> Efferent Branchial Arteries – dorsal segments (III to VI)
      • Capillary Beds develops within the nine
      • demibranch
      • Afferent Brachial Arterioles connect the
      • afferent brachial arteries with the capillaries.
      • Efferent Brachial Arterioles return oxygenated
      • blood from the capillaries to the pretrematic
      • and posttrematic arteries
      • Δ blood entering an aortic arch from the ventral aorta must pass through gill capillaries before proceeding to the dorsal aorta
      AORTIC ARCH OF FISHES FIGURE 14.17(a) Page 328
      • TELEOST
      • Similar developmental
      • changes : convert the
      • embryonic aortic arches into
      • afferent and efferent brachial
      • arteries
      • Δ The specific number
      • converted determines the
      • number of functional gills.
      • 1 st and 2 nd aortic arches tends to disappear. (fig. 14.18a)
      AORTIC ARCH OF FISHES FIGURE 14.18(a) Page 329
      • PROTOPTERUS (fig. 14.18b)
      • 3 rd and 4 th embryonic arches do not become interrupted by gill capillaries.
      • 4 th pharyngeal arches bear external gills.
      • 6 th aortic arch - pulmonary vein sprouts off the left and right and vascularizes swim bladder
      • * other archinopterygians – swim bladders are supplied from the dorsal aorta
      AORTIC ARCH OF FISHES FIGURE 14.18(b) Page 329
    • SUMMARY OF AORTIC ARCH OF FISHES AORTIC ARCH SQUALUS TELEOST PROTOPTERUS DIPNOANS, AMIA, POLYPTERUS 1 st pair (before the 6 th pair appears) ventral segments – disappears dorsal segments – efferent spiracular arteries disappear 2 nd pair first pretrematic arteries disappear 3 rd pair posttrematic arteries posttrematic arteries not become interrupted by gill capillaries 4 th pair posttrematic arteries posttrematic arteries - not become interrupted by gill capillaries - bear external gills 5 th pair posttrematic arteries posttrematic arteries 6 th pair posttrematic arteries posttrematic arteries Pulmonary Vein
      • Consists of six pairs of
      • embryonic aortic arches
      • (fig. 1.6)
      • 1 st and 2 nd – transitory
      • and regress fairly soon
      • (fig. 14.19 and 14.20)
      • After arches I and II
      • disappear : arch III
      • (carotid arch) and the
      • paired dorsal aorta
      • anterior to arch III
      • constitute the internal
      • carotid arteries (fig.
      • 14.18C, 14.19, 14.20)
      AORTIC ARCH OF TETRAPODS FIGURE 14.19 Page 330 FIGURE 14.20 Page 331 FIGURE 14.18(c) Page 329
      • 6 th pair – vasculized the lung
      • bud to form Pulmonary
      • Arteries (fig. 1.6 and 14.20d)
      • Amniotes with the
      • exception of some limbless
      • squamates lose the 5 th
      • aortic arch during
      • embryonic life. (fig. 14.18f-h
      • and 14.19e-h)
      • Frogs and some
      • Salamanders i ndependently
      • lose the 5 th aortic arches.
      AORTIC ARCH OF TETRAPODS FIGURE 14.18(f-h) Page 329 FIGURE 14.19(e-h) Page 330
      • Most terrestrial urodeles retain four pairs of aortic arches. (fig 14.18c)
      • Perennibrachiate urodeles
      • * 3 aortic arches (5th arch either disappear or unite in part with the 4th during embryogenesis) (fig.14.18d and 14.21)
      • * Gill Bypass: Larval afferent and efferent branchial arterioles that carry blood from the aortic arches into the gills and back functions throughout life and a short section of the 3rd, 4th, 5th (fused to 6th in Necturus)
      • -> constricted while the animal is using its gills but when the dissolved oxygen in the pond becomes low enough to cause the animal to gulp air, the gills shrink, and the bypasses carry more blood
      • * Bulbus Arteriosus – maintains a steady non-pulsating arterial pressure in the gills
      AORTIC ARCH OF TETRAPODS FIGURE 14.18(c-d) Page 329 FIGURE 14.21 Page 332
      • ANURANS
      • Retain four aortic arches (III through VI).
      • 3 rd , 4 th , 5 th – supply the larval external gills during the five or six days these gills function (after) supplies internal gills until metamorphosis
      • 6 th – sprouts a pulmonary artery that vascularizes the developing lung bud
      • Changes (fig 14.18e):
      • 1. Aortic Arch V disappears
      • 2. Dorsal aorta between the aortic arches III and IV (ductus caroticus) disappears
      • 3. Segment of aortic arch VI dorsal to the pulmonary artery (ductus arteriosus) disappears
      • Δ Result of changes 1&2: blood entering aortic arch III (carotid arch) can pass only to the head
      • 3: blood entering arch VI (pulmonary arch) can now pass only to the lungs and skin
      • Systemic arch (4 th ) – distribute blood to the rest of the body
      • Ventricular Trabeculae – separates oxygenated blood in the left atrium and deoxygenated blood in the right atrium
      • HOW? : expulsion from the ventricle of right atrial blood and by action of the spiral valve in the conus arteriosus
      • Ventricular Systole :
      • (1) the valve is flipped into a position that closes off the entrance to the systemic and carotid arches (diverting oxygenated blood into the common aperture that leads to the two pulmonary arches ( fig 14.12b))
      • (2) back pressure builds up in the pulmonary arteries because of filling of the lung capillaries, spiral valve flips into an alternate position that directs exygenated blood into the systemic and carotid arches
      • Retain III, IV, VI and the ductus carotices
      • Ductus arteriosus and ductus caroticus are of small diameter and carry little blood.
      • In adult – exhibits three adult
      • aortic arches – III, IV, base of VI
      • No ductus arteriosus and ductus
      • caroticus except basal lizards and
      • sometimes limbless squamates.
      • INNOVATION : instead of
      • aeveloping a spiral valve to shunt
      • fresh and deoxygenated blood
      • Into appropriate arches, the
      • embryonic ventral aorta splits
      • into three separate channels: two
      • aortic trunks (left and right
      • systemic arches) and a
      • pulmonary trunk (figs 4.18f, arv,
      • alv, and prv; 14.19e and
      • 14.22,2,3,4)
      AORTIC ARCH OF NONAVIAN REPTILES FIGURE 14.18(f) Page 329 FIGURE 14.19(e) Page 330 FIGURE 14.22(2,3,4) Page 332
      • (1) the pulmonary trunk emerges from the right
      • ventricle and leads to the left and right
      • pulmonary arches (fig 14.19e, vessel in blue) -
      • deoxygenated blood sent to the lungs
      • (2) one aortic trunk emerges from the left
      • ventricle and carries oxygenated blood to the
      • right systemicarch and the carotid arches
      • (fig.14.23)
      • (3) second aortic trunk emerges from the right
      • ventricle and leads to the left systemic arch
      • * from (1)(2)(3) – one would expect than blood
      • in the left systemic arch would be low in oxygen
      • because it comes from the right ventricle –
      AORTIC ARCH OF NONAVIAN REPTILES FIGURE 14.19(e) Page 330 FIGURE 14.23 Page 332
      • Foramen of Panizza : an aperture that connects the two aortic trunks at their base
      • During normal respiration : Left-Right Shunt (assure delivery of oxygenated blood to all parts of the body):
      • - the valve at the exit from the right ventricle into the aortic trunk remains closed
      • - the blood from the right ventricle can pass only to the lungs
      • - some oxygenated blood from the left ventricle is shunted through the foramen of panizza to the left systemic arch
      • Submerged in water : Right-Left Shunt (diverts considerable blood away from the lungs and into the systemic circulation):
      • - pulmonary arteries constrict reflexly, causing a backup of blood in the right ventricle
      • - the valve between the right ventricle and its aortic trunk is forced to open (fig. 14.23b)
      • - some right-ventricular blood is shunted to the aortic trunk that emerges from the left ventricle
      • -> utilization of the shunt is facilitated by a mild reduction in the blood pressure within the left ventricle
      AORTIC ARCH OF NONAVIAN REPTILES FIGURE 14.23(a) Page 332 FIGURE 14.23(b) Page 332
      • - have a cavum venosum at the upper limit of the Interventricular septum
      • Cavum venosum : receives deoxygenated blood from the right atrium and is confluent with both the left and right ventricles (fig 14.24)
      • - How do reptiles avoid mixing of oxygenated and deoxygenated blood in the heart?
      • (1) Ventricular Diastole: blood from the right atrium – venous blood – passes through the cavum venosum and enters the right ventricle (cavum pulmonale)
      • (2) Ventricular Systole: when cavum venosum discharge the deoxygenated blood into the cavum pulmonale to the lungs
      • (3) Ventricular Diastole: blood from the left atrium – enters the left ventricle (cavum arteriosum)
      • * MUSCULAR ACTIVITY : displaces the septal wall, blocking the passageways between the cavum venosum, the right atrium, and the cavum pulmonale and opening the passage between the cavum venosum and cavum arteriosum
      • BLOOD FLOW : Right atrium -> Cavum venosum -> Cavum Pulmonale -> Pulmonary Artery -> Lungs -> Pulmonary Veins -> Left Artery -> Cavum arteriosum -> Cavum venosum -> Aortic trunk -> Left and Right systemic arches
      • When submerged in water or radiant heat is applied to reptile:
      • - pulmonary arteries are constricted
      • - deoxygenated blood in the cavum venosum is shunted away from the cavum pulmonale and into the left aortic arch
      • * if oxygen is insufficient: additional adaptation provides energy for metabolic needs by glycolysis, an anaerobic process
      • Basal Lizard – retain 5 th aortic arch and ductus caroticus on both sides
      • Limbless lizard and snakes -left lung atrophies and may lose entire
      • left sixth aortic arch, retaining only a single pulmonary artery
      • * snakes – left third aortic arch also disappears
      • * adult snake – retain only the right third, the left and right fourth, ductus caroticus, ventral segment of the right sixth aortic arch to the right pulmonary artery arises
      • First tetrapods in which there is no opportunity in mixing
      • oxygenated and deoxygenated blood in the heart after
      • hatching. (fig. 14.6)
      • - complete interventricular septum
      • - division of embryonic ventral aorta into two trunks (pulmonary trunk from right ventricle/ single aortic trunk from the left) (fig. 14.19 g and h)
      • Truncus arteriosus and bulbus cordis – vessel carrying the blood from the heart to the early aortic arches
      • Pulmonary Trunk – leads to the sixth aortic arches
      • Aortic Trunk – leads to the third and 4 th aortic arches
      • Ductus Arteriosus – shunts blood away from the lungs and into the dorsal aorta
      • Dorsal Aorta – supplies the embryonic respiratory membranes with the blood
      • Right –Left Shunt – divert blood away from the lungs functions in unhatched chicks and fetal mammals
      AORTIC ARCH OF BIRDS & MAMMALS FIGURE 14.6 Page 319 FIGURE 14.19(g-h) Page 330
    • AORTIC ARCH OF BIRDS & MAMMALS FIGURE 14.25 Page 334 FIGURE 14.26 Page 334 Part Birds Mammals 1 st Aortic Arch x x 2 nd Aortic Arch x x 3 rd Aortic Arch internal carotid internal carotid 4 th Aortic Arch x - arch of aorta directed to the right (fig. 14.25) Base remains - arch of aorta directed to the left (14.26) 5 th Aortic Arch x x 6 th Aortic Arch Right - x Left - Pulmonary artery Right – x Left - Pulmonary Artery Ductus Caroticus x x Ductus Arteriosus closes before hatching closes with the first gasp of air into the lungs Paired embryonic ventral aorta left and right common carotid and external carotid arteries left and right common carotid and external carotid arteries
      • Respiratory surface develops on pharyngeal derivative – buds off the nearest aortic arch usually vascularize the surface
      • Pharyngeal arch develops an external or internal gill – aortic arch in that pharyngeal arch vascularizes that gill
      • Pharyngeal floor evaginates to form a lung bud – a sprout from the nearest aortic arch vascularis the bud
      • Vascularization of pharyngeal derivatives for the respiration has phylogenetic roots that extend back to the first chordate.
      • Paired in the head above the pharynx in embryos and some adult fishes and gill-breathing amphibians
      • Remains paired in the head in all adults as the internal carotid arteries
      • Unpaired in the trunk where it gives off a series of paired somatic branches to the body wall and appendages and a series of paired and unpaired visceral branches.
      • Continues to the tail as caudal artery
      • Subclavian Arteries – enlarges segmental arteries (see figs 14.16 and 14.20)
      • - arise in embryos as branches of the paired or unpaired dorsal aortas or from the third aortic archs (somebirds) or fourth aortic arches (some mammals) close to the aorta
      • - transverse the axilla = axillary artery
      • - Parallels the humerus – brachial artery
      • -Divides in the forearm = ulnar and radial arteries
      • Vertebral Artery – passes cephalad in the beck to contribute blood to the curcle of willis (fig. 16.27)
      • - not well developed in birds and some reptile
      • Vertebromuscular branches – dorsally directed and branches to the epaxial muscle, skin and vertebral column
      • Parietal Branches – encircle the body wall to the midventral line
      • 1. Intercostal branches – in long ribs
      • 2. Sacral – in Sacral Vertebrae
      • 3. Lumbar – in Lumbar Vertebrae
      • Iliac- segmental arteries that supply the pelvic fins or limbs
      • 1. Femoral – in the thigh
      • 2. Popliteal – in the knee
      • 3. Tibial – in the shank
      • *Anatomose (unite end to end) – ensure that if one of the anastomosing vessels supplying a region becomes occluded, the vessel approaching from the opposite direction will fill the affected arterial tree beyond the occlusion
      • A. Series of unpaired visceral branches (splanchnic vessels) pass via dorsal mesenteries to the unpaired viscera, chiefly digestive organs suspended in the coelom
      • Necturus – most number of vessels
      • Celiac, Cranial (Superior) mesenteric and caudal (inferior) mesenteric – as few as 3 may occur in mammals, birds, Squalus
      • Anatomoses between two successive visceral branches occur along the entire length of the gut
      • Anatomosing Visceral Branches in Mammals:
      • 1. cranial (superior) Pancreaticoduodenal branch of the celiac – caudal (inferior) Pancreaticoduodenal branch of the celiac mesentery
      • 2. middle colic branch of the cranial mesenteric – left colic branch of the caudal mesenteric
      • 3. cranial rectal branch of the caudal mesenteric – middle rectal branch of the internal iliac
      • * common in greater and lesses curvatures of the stomach
      • B. Paired Visceral Branches – include arteries to the urinary bladder, reproductive tract, gonads, kidneys and adrenals
      • * series of gonadal and renal arteries occur in basal craniates, several pairs in reptiles and usually a single pair in mammals
      • Embryonic dorsal aorta of amniotes ends at the level of the future hind limbs by bifurcation into the left and right allantoic (umbilical) arteries
      Internal Iliacs sprout off the umbilical arteries as limbs develop, and as the umbilicals become branches of the external and internal iliacs ALLANTOIC ARTERIES OF AMNIOTES
      • Vasa vasorum – vessels of the vessels, found in the walls of arteries and veins.
      • Coronary arteries and veins – vessels in the heart.
      • (in urodels, the coronary supply consists of many small arteries
      Origin: Elasmobranch- from hypobranchial arteries around the gill chambers Frogs – carotid arch Reptiles – from aortic trunk and brachiocephalic Mammals- from the base of the ascending aorta CORONARY ARTERIES
      • -‘wonderful networks’
      • -segments of arteries that are highly tortuous
      • Examples:
      • -glomeruli
      • -arterial networks in the pseudobranch of sharks
      • Cetacians and pinnipeds
        • Location: trunk and within bony vertebral canal that houses the spinal cord. They are drained by arteries that are en route to the brain
        • Function: constitute a reservoir of RBCs that were oxygenated before a dive, they supply oxygen to the brain when submerged.
      • Birds that wade in icy waters, polar bears and arctic seals
        • Location: thigh (retia having arteries and veins side by side)
        • Function: countercurrent results in the transfer of heat
      • Fishes
        • Location: swim bladders (retia are called red gland)
        • Function: provide countercurrents that help maintain an appropriate level of gaseous oxygen in the bladder
      • Mammals
        • Location: testes in scrotal sacs have a rete, pampiniform plexus, in each inguinal canal
        • Function: heat is transferred from spermatic artery to spermatic vein, assuring that the temperature within the scrotal sacs is lower than the body temperature, a necessity for the viability of sperm in those species.
        • Cardinals [ant, pos, common cardinals]
        • Renal portal
        • Lateral abdominal
        • Hepatic portal
        • Hepatic sinuses
        • Coronary veins
      • Lungs and tetrapods
        • Pulmonary stream
        • Postcava from the kidneys
        • -drains the whole body
      • CCardinal streams
      • C1. Cardinal veins
        • Where blood [except that from the digestive organs] enter to the sinus venosus that which receives blood returning to the heart
        • I nterior cardinal (precardinal) veins
        • Blood from the head other than the lower jaw
        • Empties into the common cardinal
      • E Embryonic Posterior cardinal (postcardinal) vein
        • Continuous with the caudal vein
        • Receives renal veins as they pass through the kidneys
        • Empty into the common common cardinals
        • Posterior cardinal sinuses
      • Renal Portal System
      • Caudal vein continues forward beneath the gut as a subintestinal vein
      • When the old postcardinals are lost, blood from the tail enter the peritubular capillaries
      • Lateral Abdominal Stream
      • Lateral abdominal vein
        • from the pelvic and receives an iliac vein
        • Receives a brachial vein at the pectoral level before entering the common cardinals
        • Subclavian vein – between the brachial and the common cardinals
        • Cloacal vein – metameric series of parietal veins from the lateral body wall
      • Hepatic Portal Stream and Hepatic Sinuses
      • Omphalomesenteric (vitelline) veins
        • One of the first vessels to appear in any craniates embryo
        • Yolk sac to heart
        • Breaks into sinusoidal channels due to the enlarging liver during development
        • The vitelline vein from caudal to the liver disappears, while another associates with the subintestinal vein to become the hepatic portal system
      • Subintestinal vein
        • Joins the vitelline vains and drains the digestive organs
      • Hepatic system
        • two v.veins between the liver and the sinus venosus
      Living agnathans No renal portal sys No left common cardinal Ray-finned fishes Most have no abdominals Pelvic fins: postcardinals Blood from swim bladders  hepatic/hepatic portal/postcardinal/commoncardinal dipnoan Pelvic fins: unpaired ventral abdominal emptying into sinus venosus Swim bladders: left atrium
      • Embryonic venous channels is the same as that of the sharks
      • Cardinal Veins and the Precavae
        • Post cardinals, precardinals, common cardinals
      • Azygos  old right common cardinals precava]
        • Receives shunts from the Hemiazygos
      • Both drain intercostals spaces
      Urodeles - Persist bet caudal and common cardinals Anurans - Anterior to kidneys disappears - Connection with the caudal is lost Amniotes Anterior to kidneys disappears in embryonic stage due to POSTCAVA development mammals Ant. of the RIGHT postcardinal persist –AZYGOS LEFT: HEMIAZYGOS
      •   Amniotes:
      • cats and humans lose most of the left precava
        • BRACHIOCEPHALIC VEIN, a transverse vessel drains the left side of the head left anterior limb to the right precava
        • Coronary sinus – remnant of the left precava
          • On the surface of the <3 that receives coronary veins then empties into the right atrium
              • Superior vena cava – right precava
            • precava of nonavian reptiles: sinus venosus
            • birds and humans: right atrium
      common cardinals Precavae Anterior cardinals Internal Jugular veins
      • Postcava
            • subcardinal venous plexus – receives renal veins from kidneys
            • postcava – a subcardinal that predominates. Grows into the mesentery in which is the liver is developing, becomes associated with hepatic sinuses
              • kidneys to heart via hepatic sinuses
      • tetrapods:
            • hepatic sinuses fuse forming a median vessel that becomes part of the postcava
            • mammals: caudal (inferior) vena cava
            • crocodilians: blood from the hindlimb passes directly to the postcava bypassing the kidneys
            • birds: all blood directly to the postcava
      • AAbdominal Stream
        • body wall at the site for future hindlimbs
        • cepahalad to the lateral body wall
        • receives veins from the developing forelimbs
        • common cardinals or sinus venosus
    • TETRAPODS Amphibian
      • Ventral abdominal vein – connects with the venous channels in the falciform ligament connecting liver to the body wall
      • one of these channels enlarges making all the blood form the ventral abdominal pass through the falciform ligament to the liver
      • portal stream- between the capillaries of the developing hind limb and that of the liver
      • due to the disappearance of the segments of the lateral abdomninal vein anterior to the liver
      • aids in the draining of the digestive organs and spleen
      Non-avian reptiles
      • Lateral abdominals do not unite
      • Uses the falciform ligament as a bridge from the coelom to the liver capillaries
      • Loses connection with the commons
      • (2) allantoic veins –temporary tributaries as the abdominals pass thru the ventral body wall
      • -regress when the allantois is lost prior to hatching
      Birds None of the embryonic abdominal stream is seen Mammals - Fetal life only -umbilical [allantoic] vein- all that is left of the abdominals No connection with the drainage of the hindlimbs Grows out the umbilical cord and vascularizes the placenta Unite to form a single umbilical vein -functions only to drain the placenta Round ligament of the liver Ductus venosus – eroded by umbilical vein After birth becomes the ligamentum venosum
      • Renal Portal system
      TETRAPODS Amphibians External [transverse] iliac vein – blood from hindlimbs to renal port -alternate route to heart - seen also in REPTILES Snakes Crocodilians Rps is seen as primitive relationship Some blood from hindlimbs bypass the kidneys Birds Hindlimb blood bypass the kidneys Therian mammals disappears
      • HHepatic Portal System
        • Similar in all craniates
        • Stomach, pancreas, intestines spleen
        • Terminates at the capillaries of the liver
        • Tributaries: abdominal stream [from amphibians up]
      • : veins from the swim bladders [bony fishes
      • Coronary veins
      TETRAPODS Amphibians Frogs: No definitive coronary system One c.v enters the left precava,the other empties into the ventral abdominal Reptiles Coronary veins  coronary sinus or directly into the right atrium Coronary sinus lies at the coronary sulcus [between left atrium and ventricle] Mammals
    • Caudal end of dorsal aorta Umbilical arteries Umbilical cord Placenta Umbilical Vein Ductus Venosus Liver Postcava Right atrium Interarterial foramen Left atrium Left ventricle Systemic arch Major venous channels Right ventricle Pulmonary Trunk Lungs
    • Fetal Adult foramen ovale fossa ovalis ductus arteriosus ligamentum arteriosum extra-hepatic portion of the fetal left umbilical vein ligamentum teres hepatis (the &quot;round ligament of the liver&quot;) intra-hepatic portion of the fetal left umbilical vein (the ductus venosus) ligamentum venosum proximal portions of the fetal left and right umbilical arteries umbilical branches of the internal iliac arteries distal portions of the fetal left and right umbilical arteries medial umbilical ligaments (urachus)
    • MAJOR CIRCULATORY CHANGES WHICH ADAPT THE ORGANISM FOR PULMONARY RESPIRATION The interarterial valve is pressed against the interarterial foramen by the sudden increase in pressure in the left atrium that results from the greatly increased volume of blood entering from the lungs. The umbilical arteries and vein are severed at the umbilicus. Eventually, the umbilical arteries from bladder to navel are converted into lateral umbilical ligaments. No blood flows through the umbilical vein since source has been cut off. This becomes the round ligament of the liver and the it becomes the ligamentum venosum. The ductus arteriosus closes as a result of nerve impulses passing to its muscular wall.
    • Failure of the foramen ovale to close or of the ductus arteriosus to constrict results in…. CYANOSIS - Blueness of the skin, lips and nail bed in humans
    • Amphioxus - transverse muscle in the artrial wall provides a “cough” reflex to dislodge grains and of sand Gnathostomes - possesses a complex jointed pharyngeal skeleton requiring both inspiratory and expiratory muscles to pump water over the gills
      • Osteichthyans
      • air sac
      • buccopharyngeal muscles used to pump water over the gills are also used to pump a pulse of air into an air sac
      See fig. 14.40 
    • Gill – breathing fishes can resort to pulse pumping when challenged by low-oxygen partial pressures. A species may shift strategies during its life history ( a gill-breathing larva shifting to pulse pumping at metamorphosis). Any shift to aspiration mode would potentially conserve energy. Aspiration breathing is seen in all amniotes. Fossil rhipidistian fishes with lungs were incapable of pulse pumping due to their heavy overlapping ribs and scales. The large body size and ribs of early tetrapods preclude pulse pumping.
    • The LYMPHATIC SYSTEM consists of… 1. thin-walled LYMPH CHANNELS 2. LYMPH (fluid) 3. LYMPH HEARTS 4. LYMPH NODES (birds and mammals) 5. solitary or aggregated masses of LYMPH NODULES ex. SPLEEN
    • The system begins in LYMPH CAPILLARIES or in LYMPH SINUSOIDS . Fluid empties to a vein. Valves at these exits prevent the influx of venous blood into the lymph channels.
    • Capillaries and sinusoids penetrate most of the soft tissues of the body other than the liver and the nervous system. They also collect interstitial fluids. A lymphatic network consisting of long, narrow, discrete tubular vessels with a modicum of smooth muscle in the walls is found only in birds and mammals.
    • LACTEALS - lymphatics in intestinal villi - CHYLE – lymph found in these vessels; milky appearance HEMOLYMPH - lymphatics which contain red blood cells - Living agnathans, cartilaginous fishes and humans
    • Lymph channels that drain the body wall, limbs, and tail of craniates empty into nearby veins at the base of the tail, trunk and neck. Lymph channels draining viscera are often paired in most craniates but in mammals, a single thoracic duct commences in a large abdominal lymph sinus, the cisterna chyli and empties into a branchicephalic of left subclavian vein, or into external or internal jugular veins.
      • ANURANS
      • Have numerous sinusoids which form huge lymph reservoirs separated by connective tissue septa that attaches the skin to the underlying muscles
      Subcutaneous lymph sinuses – buffers the underlying muscles from the drying effect of air
    • FACTORS THAT CONTROL THE FLOW OF LYMPH Lymph hearts at advantageous locations along lymph pathways in fishes, amphibians and reptiles (except postembryonic birds). Frogs: 2 pairs of lymph hearts Urodeles: 16 pairs Caecilians: 100 pairs Amphibians have more tissue fluids to manipulate than other craniates so their lymph hearts move a proportionately larger volume of fluid than the hearts of other craniates. Semilunar valves at the exit of the hearts prevent backflow. Lymph hearts are not present in birds after hatching but embryonic birds have them. None has been described in humans.
    • CRANIATE LYMPH FLOW is maintained… … .by activity of the skeletal muscles as they contract and relax … .by movements of the viscera … .by rhythmical changes in intrathoracic pressure that results from breathing
    • LYMPH NODES are masses of hemopoietic tissue interposed along the course of lymph channels of birds and mammals.
    • They are the “swollen glands” you feel in the neck, axilla and groin in humans when there is inflammation in areas drained. The endothelium of the sinusoidal passageways include phagocytes that ingest bacteria and other particles. The nodes are the 2 nd line of defense against bacterial infections acquired through the skin, the first line being granulocytes that assemble at the invaded area.
    • LYMPHOID MASSES Spleen Thymus (absent in hagfishes) Tonsils (in humans) Peyer’s Patches (in amniotes) Bursa of fabricius (in young birds)