The Dissection of Vertebrates A Laboratory Manual

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small median sacral artery and then enters the tail as the caudal artery (but you will not look for it). In contrast to the similar branching patterns of most of the paired arteries and veins of the aorta and posterior vena cava, the patterns of the iliac arteries and veins differ. Near the origin of the external iliac arteries, the posterior vena cava begins with the confluence of two large tributaries, the common iliac veins. Each common iliac vein, in turn, is formed by the confluence of the internal and external iliac veins. The median sacral vein, which accompanies the median sacral artery, usually joins one of the common iliac veins and continues in the tail as the caudal vein. Return to the external iliac arteries and follow one of them distally. It passes through the abdominal wall and enters the hindlimb as the femoral artery. Just before it passes through the body wall, it gives rise from its medial surface to the deep femoral artery. The latter gives rise to several branches and then passes deep into the medial side of the thigh (see also Figure 7.32). The internal iliac artery mainly supplies muscular and visceral structures in the pelvic canal. Its first branch, the umbilical artery, supplies the urinary bladder. The femoral vein and deep femoral vein empty into the external iliac vein. The umbilical vein usually empties into the internal iliac vein. Vessels Associated with the Viscera In this section, the vessels that supply and drain the viscera are examined. The arterial system consists of three vessels, the celiac, anterior mesenteric, and posterior mesenteric arteries, and their branches. Their origin from the aorta have already been identified. The structures supplied by these arteries are drained by tributaries that ultimately form the hepatic portal vein, which returns blood to the liver (Figures 7.58, 7.61, and 7.62). The hepatic portal breaks up into capillaries within the liver. These re-collect into several hepatic veins, which then enter the posterior vena cava. Reflect the viscera to the right, and locate the origins of the celiac and anterior mesenteric arteries as they first arise from the aorta, as it emerges through the diaphragm, and then extend toward the right. The celiac is a short trunk that divides into three branches. Two of these, the hepatic and left gastric arteries, slant anteriorly toward the right in this view. The third, the splenic artery, is the largest and extends almost directly toward the right. You can easily follow the hepatic for about 2 cm in this view, but change perspective to follow it more distally. Reflect the viscera (including the duodenum and head of the pancreas) to the left, and locate the hepatic portal vein, sitting primarily on the caudate lobe of the liver, and the common bile duct as it extends toward the duodenum; these structures were exposed earlier (page 191). The hepatic portal is difficult to see if it is not injected. Carefully dissect along the hepatic portal vein, freeing it as much as possible from connective tissue without destroying any of its branches. (In some specimens the vein is injected with yellow latex, which greatly facilitates dissection.) In doing so, you should reveal the hepatic artery (Figures 7.61 and 7.63). Ascertain that this is indeed the hepatic artery by reflecting the viscera to the right again, gently but firmly grasping the hepatic artery with blunt forceps, and then reflecting the viscera to the left again, thus verifying that the gripped vessel is the one you saw from the other view. This method of using forceps to identify a vessel can be used to advantage in many situations. Follow the hepatic artery anteriorly. Near the anterior margin of the caudate lobe, it usually gives off several branches, three of which can be followed into the lobes of the liver. The fourth, the gastroduodenal artery, follows the common bile duct as it heads toward the duodenum. Trace it until it divides into posteriorly curving and anteriorly curving branches dorsal to the pylorus. The posterior branch, the anterior pancreaticoduodenal artery, passes between the duodenum and pancreas. The anterior branch, the right gastroepiploic artery, passes to the distal part of the greater curvature of the stomach. Follow the right gastroepiploic artery with the duodenum in natural position but with the stomach reflected anteriorly (i.e., so you view its dorsal surface). The arteries are followed closely by corresponding veins. Trace the right gastroepiploic vein and anterior pancreaticoduodenal vein; their confluence forms the gastroduodenal vein, which enters the hepatic portal vein. With the stomach reflected anteriorly, gently pull the tail of the pancreas posteriorly. Dissect away the connective tissue and fat between the pancreas and stomach to reveal a system of arteries and veins. Then, reflect the viscera to the right and grasp the left gastric artery with forceps, and again reflect the stomach anteriorly. Trace the left gastric artery as it passes onto the lesser curvature of the stomach. The left gastric vein accompanies the artery. The splenic artery passes to the left toward the spleen (verify this by reflecting the viscera to the right and grasping the vessel with forceps). The gastrosplenic vein, which accompanies the splenic artery, is conspicuous even in uninjected specimens. It is formed by the confluence of the gastric vein and the splenic vein. Follow the splenic artery and vein. After one or two small branches to the stomach, the vein and artery divide. Follow the vein first, with both the stomach and spleen reflected anteriorly. In this view, one tributary, the anterior splenic vein, heads almost directly laterally and drains the left side of the spleen; the other, the posterior splenic vein, passes posterolaterally and drains the right SECTION V—CARDIOVASCULAR SYSTEM 205
Right medial lobe of liver Gallbladder Right gastroepiploic a. & v. Gastroduodenal a. & v. Anterior pancreaticoduodenal a. & v. Hepatic portal v. Hepatic a. Celiac trunk Splenic a. Anterior mesenteric a. Anterior mesenteric v. Head of pancreas Posterior vena cava Left lateral lobe of liver 206 CHAPTER 7 THE CAT Right gastric a. & v. Liver, caudate lobe Posterior mesenteric v. Gastrosplenic v. Posterior pancreaticoduodenal a. & v. Duodenum Intestinal branches of anterior mesenteric a. Middle colic a. Tail of pancreas Spleen Left gastric a. & v. Dissection area Greater curvature of stomach Splenic v. Left gastroepiploic aa. & vv. Anterior splenic a. & v. FIGURE 7.61 Detail of vessels of the viscera, showing liver (reflected) stomach, duodenum, pancreas, and spleen (reflected) of the cat in ventral view. side of the spleen. The anterior and posterior splenic arteries also follow this pattern, but the right splenic artery lies deep to the vein and is not apparent at first. Trace the left splenic artery and vein into the spleen. Some of their branches will be seen to stretch across to the greater curvature of the stomach. These are the left gastroepiploic arteries and veins. Work your way back proximally along the gastrosplenic vein. Its confluence with the anterior mesenteric vein, oriented nearly anteroposteriorly, forms the hepatic Posterior splenic a. & v. portal vein. Dissect along the anterior mesenteric vein for about 3 cm. With the viscera reflected to the right, trace the anterior mesenteric artery as it angles posteriorly to the right. Note the anterior mesenteric vein converging toward the artery. Continue to expose the anterior mesenteric artery. You will need to move through the coils of the intestines individually and tear the mesentery binding the coils together. As the artery and vein extend distally, they give off numerous branches, which mainly supply and drain the jejunum, ileum, cecum, and proximal portion of the colon (Figure 7.49).
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The Dissection of Vertebrates A Lab
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Acquisitions Editor: Tamsin Kent Ma
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To our readers: Despite our best ef
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Ear 67 Key Terms: Sensory Organs 68
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C HAPTER 8 THE PIGEON Introduction
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The past two decades have witnessed
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students know they are not responsi
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The study of vertebrate anatomy is
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Anterior Anterodorsal (a) (b) Poste
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PROTOSTOMATA ECHINODERMATA ENTEROPN
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ately to attribute its cause to phy
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UROCHORDATA SOMITICHORDATA CEPHALOC
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the hagfishes considered the sister
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PETROMYZONTOIDEA PLACODERMI GNATHOS
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The sister group of the Actinoptery
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ACTINOPTERYGII ACTINISTA DIPNOI RHI
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AMPHIBIA REPTILIA AMNIOTA TESTUDINE
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Anterior dorsal cartilage Annular c
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Ovary Mesentery Kidney FIGURE 2.5 V
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Pineal organ Olfactory sac Naris Or
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and posterior cardinal veins join t
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Examine a specimen of a dogfish ske
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Precerebral cavity Precerebral fene
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Neural canal Centrum Notochord Dors
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Posterior Anterior Ceratotrichia Ra
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(a) (b) (e) Epidermis Placoid scale
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Interbranchial septum Spiracle Spir
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Shark head, dorsal view (a) Pores o
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Ampullae of Lorenzini Labial fold L
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Gill ray Superficial constrictor m.
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Oral cavity Hemibranch, with lamell
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Falciform ligament Liver, right lob
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Pylorus Stomach Line of attachment
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Left coracohyoid m. (cut) Right cor
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1 2 3 4 5 6 Anterior intestinal a.
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Falciform ligament Liver, right lob
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The gastric vein accompanies the ga
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Liver (cut) Esophagus Epididymis Le
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parietal peritoneum lining the pleu
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Supraorbital canal passes onto vent
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Antorbital process (cut) Dorsal obl
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Anterior utriculus Membranous labyr
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superficial ophthalmic nerve suprac
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Olfactory sac Olfactory bulb Termin
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This sequence, however, does not ap
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hypophysis, just behind the optic n
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Cleithrum Operculum Orbit Premaxill
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Postcranial Skeleton The vertebral
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Anterior margin Growth rings Embedd
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Pharynx Heart Head kidney Liver Eso
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Pharynx Heart Duodenum Esophagus He
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Procoracoid cartilage First trunk v
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Trabecular horn Antorbital process
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Neural canal Prezygapophysis Verteb
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Mouth Head Eye Neck Lips Gular fold
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urinary bladder. It is supported fr
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Stomach Liver Hepatic portal v. Pan
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Male Urogenital System In males the
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Right lung (reflected) Stomach (cut
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External carotid a. Left branch of
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108 CHAPTER 5 THE MUDPUPPY Internal
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Right lung Stomach Dorsal aorta Rig
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Phalanges Metacarpals Carpals Prepo
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that helps form the roof of the bra
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Radio-ulna Radius Ulna Articular fo
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KEY TERMS: EXTERNAL ANATOMY cloaca
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Falciform ligament Right lobe of li
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Posterior vena cava (cut) Dorsolumb
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Right external carotid a. Right int
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Truncus arteriosus Right atrium Bul
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of the paired renal portal veins, w
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Skull Cervical vertebrae Hyoid appa
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group of jaw-closing muscles. Just
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Postorbital process Alisphenoid Fro
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Frontal b. Cribriform plate of ethm
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ceratohyoid choanae condyloid canal
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capitulum of a rib. Thoracics also
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Posterior Hemal process Hemal arch
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side of the trochlea. The supracond
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Head Neck Bicipital tuberosity Inte
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Left femur, anterior view Left femu
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Pinna Palperbrae Eye Rhinarium Exte
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Carpus, 147 Cat brain and cranial n
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Dentary bone in cat, 138-139 in fro
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Flocculonodular lobe, 222 Folia, of
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Hypophyseal pouch, 24 Hypophysis in
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Liver (continued) in mudpuppy, 96 i
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Neural crest, 8 Neural plate, 31 Ne
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Pelvis in cat, 147, 152 in frog, 11
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Pylorus, 49 Pyramids, 222 Pyriformi
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Squamosal bones in cat, 136 in frog
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Ulnare, 232 Umbilical artery/vein,
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