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Comparative Anatomy E ndocrine Organs. Kardong Chapter 15 . Part 17. Endocrine Organs. Ductless organs Secrete hormones Derived from the 3 germ layers. Pituitary Gland. Figure 17.1. Phylogeny of the vertebrate pituitary. Pituitary Gland ( Hypophysis ). Derived from ectoderm
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Comparative AnatomyEndocrine Organs Kardong Chapter 15 Part 17
Endocrine Organs • Ductless organs • Secrete hormones • Derived from the 3 germ layers
Pituitary Gland Figure 17.1. Phylogeny of the vertebrate pituitary.
Pituitary Gland (Hypophysis) • Derived from ectoderm • Two divisions • Neurohypophysis (post. pit.) • Adenohypophysis (ant. pit.) Figure 17.2. Anterior and posterior pituitary.
Pituitary Gland (cont.’d) • Neurohypophysis • Infundibulum of diencephalon • Stores hormones • Adenohypophysis • Cells evaginate away from stomadeum • Secretes hormones • Rathke’s Pouch Figure 17.3. Embryogenesis of the amniote pituitary .
Caudal Neurohemal Organ • Endocrine gland unique to some fish (teleosts and elasmobranchs) • Urophysis • Neurosensory organ (releases neurosecretions = neurohormones) • Occurs at tip of tail off of spinal cord Figure 17.4. Urophysis (caudal neurohemal organ).
Pineal • Derived from ectoderm • Produces melatonin • Gonadal regulator • Photoperiodism Figure 17.5. Location of the pineal gland in the human brain.
Derived from Mesoderm Figure 17.6. Adrenal gland tissue in lower vertebrates.
Adrenal Gland (cont.’d) • Adrenal cortex (steroidogenic) • Derived from mesoderm • Adrenal medulla • Derived form ectoderm • From neurocrest cells (aminogenic) Figure 17.8. Cross section of adrenal gland (top) and anatomical position of the adrenal glands.
Gonads • Derived from mesoderm • Within kidney tissue in some ray-finned fish • Corpuscles of Stannius (inhibits calcium uptake); in large salmon, can be 0.5 mm in diameter; also found in Amia (40-50 in number)
Endodermal Origin • Pancreatic Islets of Langerhans • Thyroid gland • Foramen cecum- reminant of thyroid invagination • Bursa of Fabricius • Outpocket of cloaca • Thymus in nature Figure 17.11. Mammalian thyroid development.
Pharyngeal Pouches • Derived from endoderm • Fish • Pouches 2, 3, 4, 5 (dorsal)- thymus • Pouch 5 (ventral)- ultimobranchial bodies • Amphibians • Pouches 3, 4, 5 (dorsal)- thymus • Pouch 5 (ventral)- ultimobranchial bodies Figure 17.12. Contributions of the embryonic pharyngeal pouches to development of endocrine glands.
Pharyngeal Pouches (cont.’d) • Mammals • Pouches 3 & 4 (dorsal)- thymus • Pouches 3 & 4 (ventral)- parathyroids • No ultimobranchialbodies (incorporated directly into the thyroid as parafollicular cells – C cells) Figure 17.13. Contributions of the embryonic pharyngeal pouches to development of endocrine glands.