The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ventricles, and is filled with cerebrospinal fluid (CSF).
The Doliolida are an order of small marine animals of the subphylum Tunicata. They are in the class Thaliacea, which also includes the salps and pyrosomes. The doliolid body is small, typically 1–2 mm long, and barrel-shaped; it features two wide siphons, one at the front and the other at the back end, and eight or nine circular muscle strands reminiscent of barrel bands.
The cloacal membrane is the membrane that covers the embryonic cloaca during the development of the urinary and reproductive organs.
The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation. Due to its large overlap with development of the urinary system, the two systems are typically described together as the urogenital or genitourinary system.
The urorectal septum is an invagination of the cloaca. It divides it into a dorsal part and a ventral part. It invaginates from cranial to caudal, formed from the endodermal cloaca, and fuses with the cloacal membrane. Malformations can cause fistulas.
Octamerella is an extinct genus of prehistoric nautiloids from the oncocerid family Hemiphragmoceratidae that lived in what is now Europe and North America during the Middle Silurian.
Brevicoceras is an extinct nautiloid genus from the order Oncocerida with wide distribution in the Middle Devonian in Eastern North America, Russia and Morocco. Nautiloids form a broad group of shelled cephalopods that were once diverse and numerous but are now represented by only a handful of species in two genera.
Acleistoceras is a genus of the oncocerid, nautiloid family Acleistoceratidae that lived in the shallow seas that covered much of North America during the Devonian; living from 409—383.7 mya, existing for approximately 25.3 million years.
Mandaloceratidae is a family in the nautiloid cephalopod order Discosorida, from the Middle and Upper(?) Silurian characterized by short, essentially straight shells referred to as breviconic, typically with a faintly exogastric shape produced by the profile of the body chamber.
Stereotoceras is a Middle and Upper Devonian genus in the oncocerid family Brevicoceratidae that formed a smooth, depressed, gyroconic shell with the dorsum much flatter that the venter. Sutures are straight ventrally but have dorsal lobes. Growth lines outline a ventral hyponomic sinus but are otherwise transverse. The siphuncle in ventral, nummuloidal, with discrete, irregular, actinosiphonate deposits at the septal foramina.
Pentameroceras is a straight to slightly exogastric breviconic oncocerid from the middle Silurian of North America and Europe belonging to the Trimeroceratidae.
Ophioceras is a genus of closely coiled tarphycerid nautiloid cephalopods, the sole representatives of the family Ophidioceratidae, characterized by an evolute shell with narrow, subrounded, annulated whorls and a subcentral siphuncle composed of thin connecting rings that show no evidence of layering. The mature body chamber is strongly divergent and is the longest proportionally of any tarphycerid. The aperture has a deep hyponomic sinus and ocular sinuses, and so resembles some lituitids.
Poterioceratidae is a family of nautiloid cephalopods included in the Oncocerida that lived during the period from the Early Devonian to the Early Carboniferous (Mississippian). Members of the Poterioceratidae are distinguished by a subcircular to compressed exogastric shell that has no hyponomic sinus and a central to subcentral siphuncle composed of subquadrate to nummuloidal segments in which the septal necks are more strongly curved on the upper, or dorsal side. This is opposite from the Karoceratidae in which siphuncle segments are inflated ventrally but straight dorsally. Some poterioceratid genera have actinosiphonate structures or annular deposits within the siphuncle. In others it is empty.
Neoaganides is a small, 1–2 cm diameter subdiscoidal to subglobular goniatitid belonging to the family Pseudohaloritidae that lived from the Late Pennsylvanian to the Late Permian, existing for some 56 million years.
Shouchangoceras is a genus of goniatitid pseudohaloritid ammonoids and is the type genus for the pseudohaloritid subfamily Shouchangoceratinae. The genus is characterized by a compressed shell as much as 5 cm in diameter, with a strongly constricted mature peristome that has shallow dorsolateral sinus, a moderately deep rounded ventral sinus, but without conspicuous lappets, and ornamented by moderately strong transverse ribs and numerous stronger longitudinal lirae, producing a weakly reticulate pattern. Lobes are attenuate. The siphuncle is within the dorsal septal flecture.
The development of the digestive system in the human embryo concerns the epithelium of the digestive system and the parenchyma of its derivatives, which originate from the endoderm. Connective tissue, muscular components, and peritoneal components originate in the mesoderm. Different regions of the gut tube such as the esophagus, stomach, duodenum, etc. are specified by a retinoic acid gradient that causes transcription factors unique to each region to be expressed. Differentiation of the gut and its derivatives depends upon reciprocal interactions between the gut endoderm and its surrounding mesoderm. Hox genes in the mesoderm are induced by a Hedgehog signaling pathway secreted by gut endoderm and regulate the craniocaudal organization of the gut and its derivatives. The gut system extends from the oropharyngeal membrane to the cloacal membrane and is divided into the foregut, midgut, and hindgut.
Dolorthoceras is a nautiloid cephalopod from the upper Paleozoic found in Lower Devonian to Lower Permian strata in North America, Europe, Asia, and Australia.
Aletoceras is a genus of Oncocerida nautiloids from the middle Devonian of North America included in the family Brevicoceratidae.
Hexameroceras is a genus of nautiloid cephalopods belonging to the order Oncocerida that lived during the middle and late Silurian. Its fossils have been found in North America in Indiana, New York, Ohio, and Wisconsin, and in Europe in the Czech Republic.
Allodelphinidae is a family of primitive platanistoid river dolphins found in marine deposits in the eastern North Pacific region, Alaska, and Japan.
