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Skull of a chick (c) and a human fetus (d) show bones or portions of bones derived from neural crest cells (shaded). Abbreviations: angular (An), basibranchial (Bb), basihyal (Bh), basisphenoid (Bs), ceratobranchial (Cb), dentary (D), epibranchial (Eb), entoglossum (Eg), exoccipital (Eo...

Skull of a chick (c) and a human fetus (d) show bones or portions of bones derived from neural crest cells (shaded). Abbreviations: angular (An), basibranchial (Bb), basihyal (Bh), basisphenoid (Bs), ceratobranchial (Cb), dentary (D), epibranchial (Eb), entoglossum (Eg), exoccipital (Eo), ethmoid (Eth), frontal (F), jugal (J), nasal (N), cartilage nasal capsule (Nc), parietal (P), palatine (Pl), premaxilla (Pm), postorbital (Po), prefrontal (Prf), parasphenoid (Ps), pterygoid (Pt), quadrate (Q), scleral ossicle (Sci), supraoccipital (Soc), squamosal (Sq), stapes (Stp). Abbreviations: ceratohyal (Ch), hyomandibula (Hy), Meckel’s cartilage (Mk), neural arch (Ne), occipital arch (Oa), orbital cartilage (Oc), polar cartilage (Pc), palatoquadrate (Pq), trabecula (Tr). Labial cartilages are not included. Figure 9.1: (a) sclerotome divides (b) halves join with adjacent halves of next sclerotome (c) junction forms centrum. Figure 9.2: Developing vertebral column showing intersegmental position. Figure 9.3: Vertebral types based on articular surface of centra. Figure 9.4: Modifications from labyrinthodont to modern amniote vertebrae. Hypocentrum is diagonal lines. Pleurocentrum is red.  Figure 9.6: Regions of vertebral column Figure 9.5: Single cervical vertebrae of anuran. Figure 9.7: atlas and axis cervical vertebrae. Figure 9.8: Dorsal view of sacral vertebrae of vertebrates. Figure 9.9: Pigeon vertebral column.  Figure 9.11: Synsacrum and pelvic Figure 9.10: Pigeon skeleton: trunk, tail, and girdle left lateral (a) and ventral (b) pectoral girdle. views. Figure 9.12: Rib types - Dorsal and ventral ribs.  Figure 9.13: Unicate processes of bird. Figure 9.14: Vertebrae and ribs of alligator. Figure 9.15: Ribs and gastralia of alligator. Figure 9.16: Keeled sternum of bird. Figure 9.17: Tetrapod sterna. Figure 9.18: Heterotopic bones (book figure 7.11). Figure 9.19: Placoderm skull; neurocranium in blue; splanchnocranium in yellow. Figure 9.20: Development of cartilaginous neurocranium. Figure 9.21: Neurocranium of human skull. Figure 9.22: Sphenoid bone.  Figure 9.24: Sphenoid bone. Figure 9.23: Human skull (a) cribriform plate (b) crista galli (c) frontal bone (d) sphenoid bone (e) temporal bone (f) sella turcica. Figure 9.25: Temporal bone of human skull. Figure 9.26: Multiple nature of temporal bone of mammals. Figure 9.27: Intramembranous ossification of human skull. Embryonic, cartilaginous neurocranium is black. Neurocranial bones are red. Other is dermal mesenchyme. Figure 9.28: Splanchnocranium of human. Skeletal derivatives of 2nd through 5th pharyngeal arches. Figure 9.29: Caudal end of Meckel’s cartilage and developing middle ear cavity. Figure 9.30: Derivatives of the human visceral skeleton (red). Figure 9.31: Skeletal derivatives of pharyngeal arches. Figure 9.32: Pattern that tetrapod dermatocrania may have evolved. Figure 9.33: Dog skull showing dermatocranium Figure 9.34: Endochondral bones (red) of (pink), chondrocranium (blue), and mammalian skull. splanchnocranium (yellow). Figure 9.35: Pectoral girdle phylogenetic lines. Dermal bones are red. Replacement bones are black.  (a) (b) Figure 9.36: Pectoral girdles of (a) Polypterus and (b) shark.. Dermal bones are red. Replacement bones are black.. Figure 9.37: Left halves of pelvic girdles showing parallel evolution. Figure 9.38: Dorsal view of left forelimb or forefin of Devonian tetrapods.  Figure 9.40: Left pectoral fin of Devonian fish [left] and forelimb of early tetrapod [right]. Figure 9.39: Cladogram of lobe-Fin fishes and amphibians. Figure 9.41: Evolution of fins to limbs. Figure 9.42: Plantigrade, digitigrade, and unguligrade feet. Ankle bones are black. Metatarsals are grey. Figure 9.43: Unguligrade adaptations in horse and camel. Bones lost are white.  (a) (b) (c) Figure 9.44: Serpentine locomotion (a) and rectilinear locomotion (b & c). (a) (b) Figure 9.45: Sidewinding locomotion (a) and concertina locomotion (b).  The Muscular System Myofibre (myotube in development) Myocyte (myoblast in development) Fig. 10.1 Actin, myosin in cytoplasm Myofibres 3 types of muscle: Skeletal muscle Cardiac muscle Smooth muscle  Skeletal (voluntary) muscle From the outside in: whole muscle wrapped in epimysium fascicles bound together by connective tissue = perimysium muscle fibres bound together by endomysium inside a fascicle Fig. 10.2 Characteristics of skeletal muscle fibres: large – 0.1 to 0.5mm diameter, many cm in length multinucleate – 100s of nuclei (syncytium) peripherally located nuclei striated Sarcomeric organisation of muscle fibre IN CYTOPLASM OF 1 CELL  Structure of the sarcomere in a MYOFIBRIL Thin actin filament Z line M line attached to Z line Z line A band I band H band Thick myosin filament Many MYOFIBRILS in the cytoplasm of a MYOFIBRE How does the sarcomere contract? ATP hydrolysis causes flexing of cross-bridges  What is the stimulus to contract? Motor end plate 1 motor neurone may innervate few or 1000s of muscle fibres Table 10-3 Groups of Somatic Muscles Muscle Groups Innervation (based on shark) Axial muscles Extrinsic ocular muscles Oculomotor (III), trochlear (IV), and abducens (VI) nerves Branchiomeric muscles Mandibular muscles Trigeminal (V) nerve Hyoid muscles Facial (VII) nerve Branchial muscles Glossopharyngeal (IX) and vagus (X) nerves Epibranchial muscles Dorsal rami of occipital and anterior spinal nerves Hypobranchial muscles Ventral rami of spino-occipital nerves, form hypobranchial nerve Trunk and tail muscles Epaxial muscles Dorsal rami of spinal nerves Hypaxial muscles Ventral rami of spinal nerves Appendicular muscles Dorsal group Ventral rami of spinal nerves Ventral group Ventral rami of spinal nerves Fig. 10.23  Action potential from the end plate gets to every sarcomere in T- tubule system, Ca release, acts on actin to allow cross-bridges Triad Ca ions C T C ATP from mitochondria Muscle fibre types 1. Twitch (phasic) muscles 1 muscle fibre – 1 motor end plate. All or none, most muscles 2. Tonic muscles 1 muscle fibre – multiple end plates. More action potentials = more contraction so frequency of nerve stimulation regulated force of contraction, small muscles, don’t fatigue, eye  Twitch muscle fibre types – SLOW and FAST SLOW TWITCH or SLOW OXIDATIVE = rich vascular, myoglobin, oxidative, mitochondria, red muscle e.g. postural muscles, resistant to fatigue e.g. dark meat of chicken leg, dark band on lateral edge of fish meat Fig. 10.4 Fig. 10.5 FAST TWITCH or FAST GLYCOLYTIC Rapid movements of brief duration, energy from anaerobic metabolism of glygolysis, glycogen content high, mitochondrial content lower, little myoglobin, appear white, called white muscle, fatigue quickly, O2 debt e.g. biceps, triceps, white meat of chicken, most fish muscle. Many muscles have both fibre types Additional factors important in output of muscles - Elasticity Connective tissue components Can only contract about third of length. Strap & fusiform longer Architecture fibres so longer contractions. Pennate more force due to con. tiss. elasticity and more myofilaments in a fibre. Fig. 10.7 Focus 10.1 Focus 10.2 Organisation of muscles Epimysium – tendon – periosteum Muscle belly usually proximal ORIGIN = proximal (doesn’t move) INSERTION = distal (usually moves) Usually arranged in antagonistic groups of flexors and extensors Movement of muscle groups: Flexion / extension e,g, elbow, hand Protraction / retraction e.g. shoulder, thigh Adduction / abduction e.g. leg Rotation e.g, foot Pronation / supination e.g. hand Satellite cells for regeneration and repair  MUSCLE ORIGINS AND NAMING Muscles from mesoderm of the embryo 1. Somites --- somatic muscles, also muscle of limbs Fig. 10.8 Fig. 10.8 2. Lateral plate mesoderm somatic muscles of flank 3. Splanchnic mesoderm visceral muscles Head muscles from head paraxial mesoderm as well as the most rostral somites Fig. 10.9 Fig. 10.11 Fig. 10.12 Fig. 10.13 Fig. 10.14 Fig. 10.15 Fig. 10.16 Fig. 10.17 Fig. 10.18 Fig. 10.19 Fig. 10.20 Fig. 10.21 Fig. 10.21 Fig. 10.22 Fig. 11.1 Fig. 11.2 Fig. 11.3 Fig. 11.4 Focus 11.1 Fig. 11.5 Fig. 11.6 Fig. 11.7 Fig. 11.8 Fig. 11.9 Fig. 11.9 Fig. 11.10 Fig. 11.11 Fig. 11.12 Fig. 11.13 Fig. 11.14 Fig. 11.15 Fig. 11.16 Fig. 11.17 Fig. 11.18 Fig. 11.19 Fig. 11.20 Fig. 11.20 Fig. 11.20 Fig. 11.21 Fig. 11.22 Fig. 11.23 Fig. 11.24 Fig. 11.25 Fig. 11.26 Fig. 11.27 Fig. 11.28 Fig. 11.29 Fig. 11.30 Fig. 11.31 Fig. 11.32 Fig. 11.33 Fig. 11.34 Fig. 11.35 Fig. 11.36 Copyright 1999 The Smithsonian Book of North American Mammals edited by Don E. Wilson and Sue Ruff. All rights reserved. Urogenital System Comparative Vertebrate Anatomy Lecture Notes 9 - Circulatory System Vertebrate Circulatory Systems:  transport gases, nutrients, waste products, hormones, heat, & various other materials  consist of heart, arteries, capillaries, & veins: o Arteries  carry blood away from the heart  have muscular, elastic walls  terminate in capillary beds o Capillaries  have very thin walls (endothelium only)  are the site of exchange between the blood and body cells o Veins  carry blood back to the heart  have less muscle in their walls than arteries but the walls are very elastic  begin at the end of capillary beds o Heart  a muscular pump (cardiac muscle)  contains a pacemaker to regulate rate but rate can also be influenced by the Autonomic Nervous System Vertebrate Hearts: (see HHMI Biointeractive - click on Vertebrate circulatorium) Cartilaginous fishes  single-circuit heart with 4 chambers: sinus venosus, atrium, ventricle, & conus arteriosus o the sinus venosus receives blood & is filled by suction when the ventricle contracts & enlarges the pericardial cavity o the atrium is a thin-walled muscular sac; an A-V valve regulates flow between atrium & ventricle  o the ventricle has thick, muscular walls o the conus arteriosus leads into the ventral aorta (and a series of conal valves in the conus arteriosus prevent the backflow of blood) Teleosts - heart is similar to that of cartilaginous fishes, except a bulbus arteriosus (a muscular extension of the ventral aorta) is present rather than a conus arteriosus (a muscular extension of the ventricle) Used by permission of John W. Kimble Lungfish & amphibians - modifications are correlated with the presence of lungs & enable oxygenated blood returning from the lungs to be separated from deoxygenated blood returning from elsewhere (see HHMI Biointeractive):  Partial or complete partition within atrium (complete in anurans and some urodeles)   Partial interventricular septum (lungfish) or ventricular trabeculae (amphibians) to maintain separation of oxygenated & unoxygenated blood  Formation of a spiral valve in the conus arteriosus of many dipnoans and amphibians. The spiral valve alternately blocks & unblocks the entrances to the left and right pulmonary arches (sending unoxygenated blood to the skin & lungs).  Shortening of ventral aorta, which helps ensure that the oxygenated & unoxygenated blook kept separate in the heart moves directly into the appropriate vessels 5 = ventricle, 11 = right atrium, 12 = left atrium, 13 = conus arteriosus Amniotes: 1 - Heart consists of 2 atria & 2 ventricles &, except in adult birds & mammals, a sinus venosus 2 - Complete interatrial septum 3 - Complete interventricular septum only in crocodilians, birds, & mammals; partial septum in other amniotes  Used by permission of John W. Kimball Arterial channels - supply most tissues with oxygenated blood (but carry deoxygenated blood to respiratory organs). In the basic pattern: 1 - the ventral aorta emerges from heart & passes forward beneath the pharynx 2 - the dorsal aorta (paired above the pharynx) passes caudally above the digestive tract 3 - six pairs of aortic arches connect the ventral aorta with the dorsal aortas Aortic arches of fishes - general pattern of development of arches in cartilaginous fishes: 1 - Ventral aorta extends forward below pharynx & connects developing aortic arches. The first pair of arches develop first. 2 - Segments of first pair are lost & remaining sections become efferent pseudobranchial arteries 3 - Other pairs of arches (2 - 6) give rise to pre- & posttrematic arteries 4 - Arches 2 - 6 become occluded; dorsal segments = efferent branchial arteries & ventral segments = afferent branchial arteries 5 - Capillary beds develop within nine demibranchs Result: Blood entering an aortic arch from ventral aorta must pass through gill capillaries before proceeding to dorsal aorta Teleosts: o the same changes convert 6 pairs of embryonic aortic arches into afferent & efferent branchial arteries o arches 1 & 2 are usually lost Lungfish: o the pulmonary artery branches off the 6th aortic arch and supplies the swim bladder (& this is the same way that tetrapod lungs are supplied) Aortic arches of tetrapods - embryos have 6 pairs of aortic arches: o but the 1st & 2nd arches are temporary & not found in adults o the 3rd aortic arches & the paired dorsal aortas anterior to arch 3 are called the internal carotid arteries o the 4th aortic arches are called the systemic arches o the 5th aortic arch is usually lost o the pulmonary arteries branch off the 6th arches & supply blood to the lungs  Source: http://www.uta.edu/biology/campbell/cva/3452circ.htm Further modifications of tetrapod arches: Amphibians: o Urodeles - most terrestrial urodeles have 4 pairs of arches; aquatic urodeles typically have 3 pairs (III, IV, & VI) o Anurans - have 4 arches early in development (larval stage); arch VI develops a pulmonary artery (to lungs) while arches III, IV, & V supply larval gills. At metamorphosis:   aortic arch 5 is lost  the dorsal aorta between arches 3 & 4 is lost, so blood entering arch 3 (carotid arch) goes to the head  a segment (ductus arteriosus) of arch 6 is lost so blood entering this arch goes to the skin & lungs  aortic arch 4 (systemic arch) on each side continue to the dorsal aorta & distributes blood to the rest of the body  Oxygenated blood from the left atrium & deoxygenated blood from the right are largely kept separate in the ventricle by:  Ventricular trabeculae  Spiral valve in the conus arteriosus o Reptiles - 3 aortic arches in adults (III, IV, & VI)  Ventral aorta - no spiral valve but truncus arteriosus is split into 3 separate passages: 2 aortic trunks & a pulmonary trunk. As a result:  pulmonary trunk emerges from the right ventricle & connects with 6th aortic arches (deoxygenated blood from right atrium goes to lungs)  one aortic trunk comes out of left ventricle & carries oxygenated blood to the right 4th aortic arch & to carotid arches  the other aortic trunk appears to come out of right ventricle & leads to left 4th aortic arch. So, does the left 4th arch carry oxygenated blood?  Turtles, snakes, & lizards - the interventricular septum is incomplete where right & left systemic arches (4th) leave the ventricle & trabeculae in that region of the heart form a ‘pocket’ called the cavum venosum. Oxygenated blood from the left ventricle is directed into cavum venosum, which leads to the 2 systemic arches. As a result, both the left & right systemic arches receive oxygenated blood. (see HHMI Biointeractive)  Source: http://www.ulg.ac.be/physioan/chapitre/ch2s2.htm Crocodilians - ventricular septum is complete but a narrow channel called the Foramen of Panizza connects the base of the right & left systemic trunks (see HHMI Biointeractive) Source: http://www.auburn.edu/academic/classes/zy/0301/Topic16/Topic16.html Role of the Foramen of Panizza in the crocodilian circulatory system:  When a crocodilian is above water and breathing air, the semilunar valve in the right aorta remains closed because of higher pressure in the left & right aorta (higher than in the right ventricle). As a result, the right aorta receives blood from the left aorta (so both aortas carry oxygenated blood) and blood from the right ventricle (low in oxygen) passes only into the pulmonary artery (and goes to the lungs). Source: http://www.stanford.edu/~chaoyc/VL/review/problem/lf_example1.html#  When a crocodilian is under water and not breathing, right ventricular pressure increases due to pulmonary resistance (vasoconstriction of blood vessels supplying the lungs). As a result, the semilunar valve in the right aorta is now forced open so some of the blood from the right ventricle now enters the right aorta rather than the pulmonary artery. This means that, rather than going to the lungs (where there is little or no oxygen anyway because the crocodilian is under water & not breathing), some of the blood enters the systemic (body) circulation. This means that vital organs & tissues (such as skeletal muscles and the central nervous system) will get an increased blood supply and additional oxygen. This, in turn, allows a crocodilian to stay underwater longer (which is most important because many crocodilians hunt by remaining underwater and 'ambushing' prey that come for a drink or to cool off). Oreillette droite = right atrium, Oreillette gauche = left atrium, Ventricule droit = right ventricle, Ventricule gauche = left ventricle Source: http://www.ulg.ac.be/physioan/chapitre/ch2s2.htm Secret of the crocodile heart (Franklin, C.E., and M. Axelsson. 2000. An actively controlled heart valve. Nature 406:847) By examining the heart of a crocodile, researchers have discovered how it is that an air-breathing creature can manage to cruise through the murk, for several hours without surfacing. The crocodile has a unique type of valve in its heart which actively controls blood flow between the lungs and the rest of the body. University of Queensland researcher, Craig Franklin, together with University of Goteborg colleague Michael Axelsson have been studying the heart of the estuarine crocodile, Crocodylus porosus. "These valves represent an absolute evolutionary novelty,” said Dr Franklin. “They are further proof of the complexity and sophistication of the 'plumbing' and general anatomy of the crocodile family," Dr Franklin said. Unlike the passive flap-like valves of other vertebrates, the crocodile valve has cog teeth made up of nodules of connective tissue. The cog teeth mesh together, diverting blood away from lungs and into their bodies. The researchers have found that these “teeth” are controlled by the amount of adrenalin in the bloodstream."When the crocodile is relaxed, the absence of adrenalin acts to close the cog-teeth valves," Dr Franklin said. He said this mechanism may allow the crocodiles to dive for several hours without needing to resurface to breathe. The valves are situated in the crocodile's right ventricle, which pumps blood to the pulmonary artery feeding the lungs as well as to the left aorta which supplies the body. The cog-teeth valve can divert blood going to the lungs back into the body, a phenomenon known as a shunt. "In contrast, mammalian hearts are very inflexible with the blood supply to the lungs a separate activity to that feeding the body." - Abbie Thomas - ABC Science Online Birds & mammals - no mixing of oxygenated & unoxygenated blood; complete interventricular septum + division of ventral aorta into 2 trunks:  Pulmonary trunk that takes blood to the lungs  Aortic trunk that takes blood to the rest of the body Result of modifications: All blood returning to right side of heart goes to the lungs; blood returning from lungs to the left side of heart goes to systemic circulation. Venous channels - In early vertebrate embryos, venous channels conform to a single basic pattern. As development proceeds, these channels are modified by deletion of some vessels & addition of others. The primary venous pathways include:  cardinals  renal portal  lateral abdominal   hepatic portal  coronary  pulmonary Source: http://www.auburn.edu/academic/classes/zy/0301/Topic16/Topic16.html The venous channels in sharks:  Cardinal streams - sinus venosus receives all blood returning to heart. Most blood enters sinus venosus via Common Cardinals. Blood from head is collected by Anterior Cardinals. Postcardinals receive renal veins & empty into Common Cardinals.  Renal Portal stream - Early in development, some blood from caudal vein continues forward as Subintestinal (drains digestive system); this connection is then lost. During development, afferent renal veins (from old postcardinals) invade kidneys, & old postcardinals near top of kidneys are lost; all blood from tail must now enter kidney capillaries.  Lateral Abdominal stream - LA vein starts at pelvic fin (where it receives iliac vein) & passes along lateral body wall; receives brachial vein, then turns, becomes Subclavian vein, & enters Common Cardinal vein.  Hepatic Portal stream & Hepatic sinuses - Among 1st vessels to appear in vertebrate embryos are Vitelline veins (from yolk sac to heart). One Vitelline vein joins with embryonic Subintestinal vein (that drains digestive system) & becomes the Hepatic Portal System. Between liver & sinus venosus, 2 Vitelline veins are known as Hepatic sinuses.  Source: http://www.uta.edu/biology/restricted/3452circ.htm Venous channels in other fishes are much like those of sharks except:  Cyclostomes have no renal portals  In most bony fishes the lateral abdominals are absent & the pelvic fins are drained by postcardinals Venous channels of tetrapods - early embryonic venous channels are very similar to those of embryonic sharks. Changes during development include:  Cardinal veins & precavae - embryonic tetrapods have posterior cardinals, anterior cardinals, & common cardinals o Urodeles - posterior cardinals persist between caudal vein & common cardinals in adults o Anurans, most reptiles, & birds - posterior cardinals are lost anterior to kidneys  o Mammals - right posterior cardinal persists (azygos); part of left posterior cardinal persists (hemiazygos) Terminology note: Common cardinals in tetrapods are called PRECAVAE; anterior cardinals are called INTERNAL JUGULAR VEINS. o Some mammals (e.g., cats & humans) lose the left precava; the left brachiocephalic carries blood from left side to right precava (sometimes called SUPERIOR VENA CAVA).  Postcava - Both posterior cardinals begin to develop in embryos, but only one persists & becomes the POSTCAVA. The Postcava passes directly through the liver (sort of an ‘expressway’ for blood from kidneys & the posterior part of the body to the heart). The Postcava is sometimes called the INFERIOR VENA CAVA. In crocodilians, birds, & mammals, veins from hindlimbs connect directly to Postcava.  Abdominal stream: o Early tetrapod embryos - paired lateral veins (like lateral abdominals of sharks) begin in caudal body wall near hind limbs, continue cranially, receive veins from forelimbs, & empty into cardinal veins or sinus venosus. As development continues:  Amphibians - 2 abdominal veins fuse at midventral line & form VENTRAL ABDOMINAL VEIN. Blood in this vessel goes into liver capillaries & abdominals anterior to liver are lost (so abdominal stream no longer drains anterior limbs).  Reptiles - 2 lateral abdominals do not fuse but still terminate in liver capillaries (so do not drain anterior limbs; see diagram below).  Birds - retain none of their embryonic abdominal stream as adults  Mammals - no abdominal stream in adults  Renal Portal system: o Amphibians & some reptiles - acquires a tributary (external iliac vein; not homologous to mammalian external iliac) which carries some blood from the hind limbs to the renal portal vein. This channel provides an alternate route from the hind limbs to the heart. o Crocodilians & birds - some blood passing from hind limbs to the renal portal by-passes kidney capillaries, going straight through the kidneys to the postcava (see diagram above) o Mammals - renal portal system not present in adults   Hepatic Portal system - similar in all vertebrates; drains stomach, pancreas, intestine, & spleen & terminates in capillaries of liver  Pulmonary veins - carry blood from lungs to left atrium in lungfish & tetrapods Circulation in a mammalian fetus & changes at birth: In a developing fetus, blood obtains oxygen (& gives up carbon dioxide) via the placenta, not the lungs. As a result, blood flow must largely bypass the lungs so that oxygentated blood can get to other developing tissues. Getting oxygenated blood from the placenta back to the heart & out to the body as quickly and efficiently as possible involves a series of vessels & openings found only in a mammalian fetus:  blood (with oxygen & nutrients acquired in placenta) passes into umbilical vein  blood largely bypasses the liver via the ductus venosus  blood returns to the heart & enters right atrium, but much of the blood then bypasses the right ventricle & enters the left atrium via the foramen ovale  blood that does enter the right ventricle largely bypasses the pulmonary circulation via the ductus arteriosus Major changes at birth: 1 - Ductus arteriosus closes 2 - Foramen ovale sealed off 3 - Blood no longer flows through umbilical vein Lymphatic system - found in all vertebrates; consists of lymph vessels, lymph nodes, &, in some species, lymph hearts  Lymph vessels o found in most soft tissues of the body & begin as blind-end lymph capillaries that collect interstitial fluid o valves present (in birds & mammals) that prevent backflow o empty into 1 or more veins (e.g., caudal, iliac, subclavian, & posterior cardinal)  Lymph nodes - located along lymph vessels; contain lots of lymphocytes & macrophages (phagocytic cells)  Lymph hearts - consist of pulsating smooth muscle that propels lymph fluid through lymph vessels; found in fish, amphibians, & reptiles Comparative Vertebrate Anatomy Lecture Notes - Respiratory System Respiration is the process of obtaining oxygen from the external environment & eliminating CO2.  External respiration - oxygen and carbon dioxide exchanged between the external environment & the body cells  Internal respiration - cells use oxygen for ATP production (& produce carbon dioxide in the process) Adaptations for external respiration: 1 - Primary organs in adult vertebrates are external & internal gills, swim bladders or lungs, skin, & the buccopharyngeal mucosa 2 - Less common respiratory devices include filamentous outgrowths of the posterior trunk & thigh (African hairy frog), lining of the cloaca, & lining of esophagus Respiratory organs:  Cutaneous respiration o respiration through the skin can take place in air, water, or both o most important among amphibians (especially the family Plethodontidae)  Gills (see Respiration in Fishes) o Cartilaginous fishes:  5 ‘naked’ gill slits  Anterior & posterior walls of the 1st 4 gill chambers have a gill surface (demibranch). Posterior wall of last (5th) chamber has no demibranch.  Interbranchial septum lies between 2 demibranchs of a gill arch  Gill rakers protrude from gill cartilage & ‘guard’ entrance into gill chamber  2 demibranchs + septum & associated cartilage, blood vessels, muscles, & nerves = holobranch o Bony fishes (teleosts): (See 'Ventilation in Teleost Fishes')   usuall y have 5 gill slits  operc ulum proje cts back ward over gill cham bers  interb ranch ial septa are very short or absent o Agnathans:  6 - 15 pairs of gill pouches  pouches connected to pharynx by afferent branchial (or gill) ducts & to exterior by efferent branchial (or gill) ducts  Larval gills: o External gills  outgrowths from the external surface of 1 or more gill arches  found in lungfish & amphibians o Filamentous extensions of internal gills  project through gill slits  occur in early stages of development of elasmobranchs o Internal gills - hidden behind larval operculum of late anuran tadpoles Swim bladder & origin of lungs - most vertebrates develop an outpocketing of pharynx or esophagus that becomes one or a pair of sacs (swim bladders or lungs) filled with gases derived directly or indirectly from the atmosphere. Similarities between swim bladders & lungs indicate they are the same organs. Vertebrates without swim bladders or lungs include cyclostomes, cartilaginous fish, and a few teleosts (e.g., flounders and other bottom-dwellers). Swim bladders:  may be paired or unpaired (see diagram above)  have, during development, a pneumatic duct that usually connects to the esophagus. The duct remains open (physostomous) in bowfins and lungfish, but closes off (physoclistous) in most teleosts.  serve primarily as a hydrostatic organ (regulating a fish's specific gravity)  gain gas by way of a 'red body' (or red gland); gas is resorbed via the oval body on posterior part of bladder   may also play important roles in: o hearing - some freshwater teleosts (e.g., catfish, goldfish, & carp) 'hear' by way of pressure waves transmitted via the swim bladder and small bones called Weberian ossicles (see diagram below) o sound production - muscles attached to the swim bladder contract to move air between 'sub-chambers' of the bladder. The resulting vibration creates sound in fish such as croakers, grunters, &midshipman fish. o respiration - the swim bladder of lungfish has number subdivisions or septa (to increase surface area) & oxygen and carbon dioxide is exchanged between the bladder & the blood Source: http://www.notcatfish.com/ichthyology/weberian_apperatus.htm Lungs & associated structures  Larynx o Tetrapods besides mammals - 2 pair of cartilages: artytenoid & cricoid o Mammals - paired arytenoids + cricoid + thyroid + several other small cartilages including the epiglottis (closes glottis when swallowing) o Amphibians, some lizards, & most mammals - also have vocal cords stretched across the laryngeal chamber  Source: http://www.worldzone.net/music/singingvoice/images/glottis.gif  Trachea & syrinx o Trachea  usually about as long as a vertebrates neck (except in a few birds such as cranes)  reinforced by cartilaginous rings (or c-rings)  splits into 2 primary bronchi &, in birds only, forms the syrinx at that point  Lungs o Amphibian lungs  2 simple sacs  internal lining may be smooth or have simple sacculations or pockets  air exchanged via positive-pressure ventilation o Reptilian lungs  simple sacs in Sphenodon & snakes  Lizards, crocodilians, & turtles - lining is septate, with lots of chambers & subchambers  air exchanged via positive-pressure ventilation o Avian lungs - modified from those of reptiles:  air sacs (diverticula of lungs) extensively distributed throughout most of the body  arrangement of air ducts in lungs ----> no passageway is a dead- end  air flow through lungs (parabronchi) is unidirectional o Mammalian lungs:   multichambered & usually divided into lobes  air flow is bidirectional: Trachea primary bronchi secondary bronchi tertiary bronchi bronchioles alveoli  air exchanged via negative pressure ventilation, with pressures changing due to contraction & relaxation of diaphragm & intercostal muscles Comparative Vertebrate Anatomy Lecture Notes - Digestive System Digestive tract - ‘tube’ from mouth to vent or anus that functions in:  ingestion  digestion  absorption  egestion Major subdivisions include the oral cavity, pharynx, esophagus, stomach, small & large intestines, and cloaca. Accessory organs include the tongue, teeth, oral glands, pancreas, liver, & gall bladder. Differences in the anatomy of vertebrate digestive tracts is often correlated with the nature & abundance of food:  readily absorbed (e.g., hummingbirds) vs. requiring extensive enzymatic activity (e.g., carnivores)  constant food supply (e.g., herbivores) vs. scattered supply (e.g., carnivores) The embryonic digestive tract of vertebrates consists of 3 regions: 1 - midgut - contains yolk or attached yolk sac 2 - foregut - oral cavity, pharynx, esophagus, stomach, & small intestine 3 - hindgut - large intestine & cloaca Mouth & oral cavity. The oral cavity begins at the mouth & ends at the pharynx. Fish have a very short oral cavity, while tetrapods typically have longer oral cavities. The mammalian mouth is specialized to serve as a suckling and masticatory organ (with muscular cheeks).  Palate = roof of the oral cavity o primary palate - internal nares lead into the oral cavity anteriorly o secondary palate - nasal passages are located above the secondary palate and open at the end of the oral cavity Teeth are derivations of dermal armor.  Placoid scales - show gradual transition to teeth at the edge of the jaw  Composition of teeth - primarily dentin surrounded by enamel  Vary among vertebrates in number, distribution in the oral cavity, degree of permanence, mode of attachment, & shape Toothless vertebrates are found in every class of vertebrates and include agnathans, sturgeons, some toads, turtles, birds, & baleen whales. A right whale swims at or near the surface of the water with its mouth open. Water and food enter through a gap in the front baleen plates, and food is caught in the matted baleen fringes inside. Toothed vertebrates:  Fish - teeth are numerous & widely distributed in the oral cavity & pharynx  Early tetrapods - teeth widely distributed on the palate; most amphibians & some reptiles still have teeth on the vomer, palatine, & pterygoid bones  Crocodilians, toothed birds, & mammals - teeth are limited to the jaws TEETH: 1 - have tended toward reduced numbers & distribution 2 - most vertebrates (through reptiles) have succession of teeth 3 - most vertebrates (except mammals) replace teeth in ‘waves’ (back to front; every other tooth)  4 - mammals generally develop 2 sets of teeth: milk (deciduous) teeth & permanent teeth Morphological variation in teeth:  vertebrates other than mammals - all teeth are shaped alike (homodont dentition)  mammals - teeth exhibit morphological variation: incisors, canines, premolars, & molars (heterodont dentition) o incisors = cutting o canines = piercing & tearing o premolars & molars = macerating Tongue:  Gnathostome fish & primitive amphibians - tongue is a simple crescent-shaped elevation in the floor of the oral cavity caused by the underlying hyoid skeleton & is called the primary tongue  Most amphibians - primary tongue (or hypobranchial eminence) + glandular field (or tuberculum impar) ('stuffed' with hypobranchial musculature)  Reptiles & mammals - primary tongue + glandular field (or tuberculum impar) + lateral lingual swellings (more hypobranchial muscle)  Birds - lateral lingual swellings are suppressed & intrinsic muscle is usually lacking Tongue mobility:  Turtles, crocodilians, some birds, & whales - tongue is largely immobilized in the floor of the oral cavity & cannot be extended  Snakes, insectivorous lizards & amphibians, & some birds - tongue sometimes long and may move in and out of the oral cavity (seehttp://www.autodax.net/feedingmovieindex.html)  Mammals - tongue is attached to the floor of the oral cavity (via the frenulum) but can still be extended out of the oral cavity  Using a keen sense of smell, anteaters are able to effectively track down ant nests on the forest floor. Once a nest is found, the mammal usually rips it open with its sharp foreclaws to expose its delectable contents. The anteater then proceeds to catch and eat the ants by repetitively flicking its long sticky tongue in and out of the nest. The giant anteater's unique tongue can measure as long as two feet (60 cm). Functions of vertebrate tongues:  capturing & gathering food (see woodpecker tongue below)  taste  manipulate fluids & solids in oral cavity  swallowing  thermoregulation  grooming  human speech Oral glands - secrete a variety of substances including:  saliva o Lubrication and binding: the mucus in saliva is extremely effective in binding masticated food into a slippery bolus that (usually) slides easily through the esophagus without inflicting damage to the mucosa. Saliva also coats the oral cavity and esophagus, and food basically never directly touches the epithelial cells of those tissues. o Solubilizes dry food: in order to be tasted (by taste buds), the molecules in food must be solubilized. o Oral hygiene: The oral cavity is almost constantly flushed with saliva, which floats away food debris and keeps the mouth relatively clean. Saliva also contains  lysozyme, an enzyme that lyses many bacteria and prevents overgrowth of oral microbial populations. o Initiates starch digestion: in most species, amylase is present in saliva and begins to digest dietary starch into maltose. Amylase does not occur in the saliva of carnivores. o Provides alkaline buffering and fluid: this is of great importance in ruminants, which have non-secretory forestomachs. o Evaporative cooling: clearly of importance in dogs, which have very poorly developed sweat glands - look at a dog panting after a long run and this function will be clear.  poison (lizards, snakes, and mammals)  anticoagulant (vampire bats; video) Pharynx - part of digestive tract exhibiting pharyngeal pouches (at least in the embryo) that may give rise to slits  Fish - pharynx is respiratory organ  Tetrapods: o pharynx is the part of the foregut preceeding the esophagus & includes:  glottis (slit leading into the larynx)  openings of auditory (eustachian) tubes  opening into esophagus Mammals - an epiglottis is positioned over the glottis so that, when a mammal swallows, the larynx is drawn forward against the epiglottis & the epiglottis blocks the glottis (which prevents food or liquids from entering the trachea)  Source: http://www.stroke.cwc.net/niweb/faq.htm Esophagus:  a distensible muscular tube connecting the pharynx & the stomach  may have diverticulum called the crop (see diagram of pigeon below) Stomach = muscular chamber(s) at end of esophagus  serves as storage & macerating site for ingested solids & secretes digestive enzymes  Vertebrate stomachs: o Cyclostomes - weakly developed; similar to esophagus o Fish, amphibians, & reptiles - increasing specialization (more differentiated from the esophagus) o Birds - proventriculus (glandular stomach) and ventriculus (muscular stomach, or gizzard) o Mammals - well-developed stomach; ruminants have multichambered stomachs:  Reticulo-rumen (reticulum and rumen) Reticulum and rumen are often discussed together since each compartment is separated by a low partition. Eighty percent of the capacity of the stomach is related to the reticulo-rumen. The contents of the reticulum and rumen intermix freely. The rumen is the main fermentation vat where billions of microorganisms attack and break down the relatively indigestible feed components of the ruminant's diet. Omasum After fermentation in the reticulum and rumen, food passes to the omasum. The omasum acts as a filter pump to sort liquid and fine food particles. Coarse fibre particles are not allowed to enter the omasum. Also, the omasum may be the site for absorption of water, minerals and nitrogen. Abomasum Source: http://www.uta.edu/biology/restricted/3452dig.htm The abomasum is the true stomach and the only site on the digestive tract that produces gastric juices (HCl and the enzymes, pepsin and rennin). Ingesta only remains here for 1 to 2 hours. The intestine is located between the stomach & the cloaca or anus & is an important site for digestion & absorption. Vertebrate intestines are differentiated to varying degrees into small & large intestines.  Fishes - relatively straight & short intestine in cartilaginous fishes & in primitive bony fishes (lungfish & sturgeon). However, the intestine of cartilaginous fishes has a spiral valve.  Amphibians - intestines differentiated into coiled small intestine and short, straight large intestine Reptiles & Birds - coiled small intestines & a relatively short large intestine (that empties into the cloaca) Mammals - small intestine long & coiled and differentiated into duodenum, jejunum, & ileum. The large intestine is often relatively long (but not as long as the small intestine). A cecum is often present at the junction of the small & large intestines in herbivores.  Source: http://www.uta.edu/biology/restricted/3452dig.htm Accessory organs - Liver, gall bladder, & pancreas  Liver & gall bladder o liver produces bile which is stored in the gall bladder (cyclostomes, most birds, and some mammals, including cervids, have no gall bladder) o bile aids in digestion by emulsifying fats (breaking fats down into tiny particles that permits more efficient digestion by enzymes)  Pancreas - secretes pancreatic juice (bicarbonate solution to neutralize acids coming from the stomach plus enzymes to help digest carbohydrates, fats, and proteins) into the intestine Ceca - blind diverticula that serve to increase the surface area of the vertebrate digestive tract  Fishes - pyloric & duodenal ceca are common in teleosts; these are primary areas for digestion and absorption (not fermentation chambers)  Tetrapods - ceca are present in some herbivores; may contain bacteria that aid in the digestion of cellulose  Source: http://ourworld.compuserve.com/homepages/gr_frank/dig_anat.htm Cloaca:  chamber at end of digestive tract that receives the intestine, & urinary & genital ducts, & opens to the exterior via the vent  shallow or non-existent in lampreys, ray-finned fishes, & mammals (except monotremes)  if no cloaca is present, the intestine opens directly to the exterior via anus Source: http://trc.ucdavis.edu/mjguinan/apc100/modules/Reproductive/bird/male0/male10.html