Dogfish Shark Dissection Part 2 PDF

SPINY DOGFISH SHARK DISSECTION: PART 2 Squalus acanthias BIO 415L Presented by Dr. Sarah Polekoff DOGFISH STRUCTURES Muscular System (Cutting Line Identify the following Liver (right, median, & left 1): structures of internal anatomy lobes)...

SPINY DOGFISH SHARK DISSECTION: PART 2 Squalus acanthias BIO 415L Presented by Dr. Sarah Polekoff DOGFISH STRUCTURES Muscular System (Cutting Line Identify the following Liver (right, median, & left 1): structures of internal anatomy lobes) during the dissection (fig. Gall bladder Spiracle 3.17-3.19): Dorsal aorta Meckel’s cartilage Oviduct (female) Adductor mandibulae m. External nares Siphon (male) External pharyngeal slit Labial groove Stomach Scapular process Buccal cavity Liver Myomere Upper jaw Pancreas Myoseptum Spiracle Spleen Pectoral adductor m. Tongue Small intestine Ampullae of lorenzini Internal gill slits/gill rays Rectal gland External gill slits Colon Heart Kidney  MUSCULAR SYSTEM  MYOMERE and MYOSEPTUM: Z- shaped myomeres, separated by connective tissue sheets termed myosepta.  EPAXIAL vs HYPAXIAL MUSCULATURE and the HORIZONTAL SKELETOGENOUS SEPTUM:  Dorsal epaxial musculature and the ventral hypaxial musculature divided by the horizontal skeletogenous septum, a connective tissue sheet lying in the frontal plane  MUSCULAR  MECKEL’S CARTILAGE:  Ventral half of the mandibular arch forms the lower jaw  ADDUCTOR MANDIBULAE M.:  Extends between upper and lower jaws and closes the mouth  PECTORAL ABDUCTOR vs ADDUCTOR M.:  Abductor is dorsally located.  Pulls the pectoral fin dorsally.  Adductor is ventrally  Pulls the pectoral fin ventrally.  LINEA ALBA:  Linea alba is connective tissue separating left and right myomeres midventrally MUSCULAR SYSTEM (Cont’d) SCAPULAR PROCESS: attaches to the coracoid bar between the fins AMPULLAE OF LORENZINI: sensitive to electrical fields (they can help a shark sense prey by detecting the electrical fields generated by activities of the prey). The ampullae are concentrated on the head   EXTERNAL PHARYNGEAL SLIT: divided by INTERNAL ANATOMY four interbranchial septa.  Water leaves the pharynx as the water passes over the respiratory structures or gills and gill lamellae  INTERNAL GILL SLITS/GILL RAYS vs. EXTERNAL GILL SLITS INTERNAL ANATOMY SPIRACLE and SPIRACULAR VALVE:  Relatively large opening into the pharynx.  Posterior to each eye.  Anterior wall contains a fold of tissue, the spiracular valve, that can be folded over the opening to close the spiracle.  A row of five external pharyngeal slits, separated by four interbranchial septa INTERNAL ANATOMY  LABIAL GROOVE: labial pocket lies on either side of the mouth. Mouth and pocket are separated by a flap, the labial fold, which is supported by the labial cartilage.  BUCCAL CAVITY = mouth  UPPER JAW (FYI): palatoquadrate cartilages fuse anteriorly. Levator palatoquadrati elevates the palatoquadrate  TONGUE: floor is formed by the primary tongue. Not a true tongue as occurs in tetrapods. The boundary between the oral cavity and pharynx is not clearly defined in the adult, though the oral cavity is often considered to end at the posterior margin of the teeth. INTERNAL ANATOMY  PANCREAS: two parts linked by a narrow isthmus. A flattened, oval ventral lobe (Figure 3.24) adheres to and almost completely hides the ventral surface of the duodenum, the anterior segment of the intestine. The narrow, elongated dorsal lobe of the pancreas extends posteriorly. INTERNAL ANATOMY STOMACH:  Externally: no distinction between the stomach and esophagus.  Internally:  Esophagus bears finger-like projections or papillae  Stomach bears longitudinal ridges termed rugae main part of the stomach is the body.  Pylorus: The smaller, narrower, posterior part is the pyloric region. Constricts at the pylorus, which marks the separation between the stomach and intestine. INTERNAL ANATOMY  SPLEEN: triangular spleen is the large, dark organ at the posterior end of the stomach. The spleen is a lymphoid organ, not a digestive organ, and functions in the production and storage of blood cells. INTERNAL ANATOMY  SMALL INTESTINE: intestine of the shark is subdivided into a short duodenum, a valvular intestine, and a narrow colon (Figures 3.24 and 3.25).  Valvular intestine bears a spiral valve, an internal subdivision that increases the effective length of the intestine  COLON: lacking a spiral valve, extends from the valvular intestine  RECTAL GLAND: salt-excreting digitiform gland INTERNAL ANATOMY HEART: within pericardial cavity  Sinus venosus: the thin, triangular, posterior, sac-like chamber attached to the transverse septum. It receives venous blood from the body and passes it anteriorly into the atrium  Atrium (Single): large and appears to envelop the ventricle, often giving the impression that there are two. This single atrium passes its blood to the ventricle. INTERNAL ANATOMY  Ventricle: most conspicuous structure of the heart  Conus arteriosus, through which blood leaves the heart  Enters the ventral aorta.  DORSAL AORTA: several branches that you are not responsible for INTERNAL ANATOMY LIVER (RIGHT, MEDIAN, & LEFT LOBES) and GALL BLADDER (Right margin):  Most conspicuous is the liver  Occupies most of the anterior part of the cavity.  NOTE: Do not cut off these lobes (otherwise, you will have to contend with a continuous leakage of the oil present in the liver that reduces the shark’s specific gravity). INTERNAL ANATOMY SIPHON (MALE): structure associated with the reproductive system Lies on the ventral surface of the fin musculature. Associated with each clasper. Elongated, sac-like siphon lies just deep to the skin on the ventral surface of the pelvic fin. The siphon expels fluid through this route that contributes to seminal fluid.  INTERNAL ANATOMY OVIDUCT (FEMALE): lies on the ventral surface of each kidney. Each oviduct is a narrow tube unsupported by a mesentery in immature specimens, but more conspicuous and supported by a mesotubarium in mature individuals  INTERNAL ANATOMY  KIDNEY:  Paired kidneys are long, narrow structures on either side of the dorsal aorta on the roof of the body cavity (Figures 3.33 and 3.34).  They extend nearly the length of the cavity. As they lie dorsal to the parietal peritoneum lining the pleuroperitoneal cavity, the kidneys are retroperitoneal.  Afferent renal veins bring blood to kidney. Efferent renal veins collect blood from the kidneys. BABY SHARK … SHARK SHARK SHARK SHARK SHARK SHARK NEUROLOGICAL SYSTEM Shark Brains NEUROLOGICAL SYSTEM Dorsal view (left) of Squalus brain and midsagittal section through Squalus brain (right). CC BY Kristin Conroy & Elizabeth Swislosky. NEURO-ANATOMY References Iuliis, G. D., & Pulerà, D. (2019). The Dissection of Vertebrates (3rd Edition). Elsevier S & T. https://bookshelf.vitalsource.com/ books/9780124105003