Comparative Anatomy E ndocrine Organs Kardong Chapter 15 Part 17.
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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.
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 ultimobranchial bodies
(incorporated directly into the thyroid as parafollicular cells – C cells)
Figure 17.13. Contributions of the embryonic pharyngeal pouches to development of endocrine glands.
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