. Chordate morphology. Morphology (Animals); Chordata. tricle, but no spiral valve. There is a distal rins: of valves in Cryplohranchus. The distal end of the truncus is much expanded in some salamanders, as a bulbus arteriosus; this term is also used sometimes for the conus area of the trun- cus. In Salamandra there are proximal and distal series of valves and a very small spiral valve. The amphibian heart differs from the reptilian or mam- mal heart in that the sinus venosus is retained. In the previ- ous groups it has been reduced or lost. In the amphibian heart one can observe the trabecul
. Chordate morphology. Morphology (Animals); Chordata. tricle, but no spiral valve. There is a distal rins: of valves in Cryplohranchus. The distal end of the truncus is much expanded in some salamanders, as a bulbus arteriosus; this term is also used sometimes for the conus area of the trun- cus. In Salamandra there are proximal and distal series of valves and a very small spiral valve. The amphibian heart differs from the reptilian or mam- mal heart in that the sinus venosus is retained. In the previ- ous groups it has been reduced or lost. In the amphibian heart one can observe the trabeculae carnae, the strands of muscle tissue making up the muscular walls. These trabecu- lae are best observed in the atrial walls where they are separated by membranous areas. Embryo/og/ca/ development The amphibian heart devel- ops much like that of the preceding groups. There is a sig- moid flexure in the vertical (sagittal) plane. The sinus venosus and atrium are dorsal, and the ventricle postero- ventral with the truncus leads forward from it. A fenes- trated interatrial septum appears which extends toward the atrioventricular opening. The atrioventricular cushions margin this opening above and below and give rise to the flap valves extending into the ventricle. The pulmonary veins develop along with the interatrial septum. At first they open into the sinus venosus, but this opening moves to the left so that an entrance into the left auricle is effected. In the plethodontids (lungless salamanders), neither interatrial septum nor pulmonary veins develop. In the aquatic types, the septum remains incomplete and fenestrated or degene- rates in the adult. Choanate fishes The heart of Prolopterus or Leptdosiren is four-chambered (Figure 11-5). The sinus venosus leads by way of the broad opening into the auricular chamber which is expanded on either side of a thin, perforate septum. The blood from the sinus enters to the right of the septum, the blood from the pulmonary vein to the l
Size: 1140px × 2193px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionameri, bookcollectionbiodiversity
