Comparative AnatomyEndocrine Organs

KardongChapter 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.

Figure 17.6. Adrenal gland tissue in lower vertebrates.

Derived from Mesoderm

Figure 17.7. Adrenal gland tissue in higher 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)

Figure 17.9. Vertebrate thyroid morphology in vertebrates.

Figure 17.10. Pancreas and islets of Langerhans.

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.

The End