1. Comparative Anatomy Sensory and Endocrine Organs
Note Set 14
Chapter 15 & 17

2. Sense Organs Monitor external & internal environment
Somatic or visceral receptors
Specific or general

3. Special Somatic Receptors Neuromasts
In skin of fish and amphibians
Monitors mech, elect, and chem stimuli
Ampullae of Lorenzini in shark snout
Figure 16.1: Ampullae of Lorenzini in shark.

4. Special Somatic Receptors (cont.) Neuromasts
Pit organs along shark gill region
Lateral line canal
Linear series
Derived from ectodermal placodes
Figure 16.2: External openings of neuromast organs in Squalus.
Figure 16.3: Neuromast organ and lateral line canal in a fish.

5. Special Somatic Receptors Membranous Labyrinth
Vertebrates have pair of fluid filled membranous labyrinths
Filled with endolymph
Surrounded by perilymph
Figure 16.5: Membranous labyrinths of human.
Figure 16.4: Left membranous labyrinth of craniates; semicircular canals (1, 2, & 3), sacculus (s) and utriculus (u).

6. Special Somatic Receptors (cont.) Membranous Labyrinth
Semicircular canals, utriculus, and sacculus
Inside canals:
Otoliths
Sensory hairs- perceive motion
Angular motion detected by semicircular canals
Linear motion detected by utriculus and sacculus
Figure 16.6: Vestibular apparatus.

7. Figure 16.7: Human anatomy of the ear.
Figure 16.8: Anlagen of amniote inner ear (otocyst). Embryonic head (a) and cross section of head (b).

8. Special Somatic Receptors (cont.) Membranous Labyrinth
Lagena
Out pocketing of sacculus wall
Gives rise to cochlea in mammals
Organ of Corti
Figure 16.9: Cochlea and organ of corti
in mammal.

9. Special Somatic Receptors (cont.) Membranous Labyrinth
Weberian ossicles
Fish transmit sound waves
Modified transverse process
Sinus impar (some fish)
Assists in transport of sound
(a)
(b)
Figure 16.10: (a) weberian ossicles (b) weberian apparatus for transmitting swim bladder vibrations to ear.

10. Special Somatic Receptors (cont.) Membranous Labyrinth
Middle Ear of Tetrapods
Canal from evagination of 1st pharyngeal pouch
Eustachian tube
Communication btwn pharynx and middle ear
Figure 16.11: Position of eustachian tube.

11. Special Somatic Receptors (cont.) Membranous Labyrinth
Middle Ear of Tetrapods
Bones:
Malleus, incus, and stapes
Derived from 1st and 2nd visceral arches
Stapes is columella in reptiles and birds
Figure 16.12: Middle ear bones.

12. Special Somatic Receptors (cont.) Membranous Labyrinth
Middle Ear of Tetrapods
Figure 16.13: Development of the middle ear bones.

13. Special Somatic Receptors (cont.) Membranous Labyrinth
Outer Ear of Tetrapods
Pinnae
Ear drum set back into skull
Crocs, birds, and mammals
Tympanic membrane on outside
Frogs
External auditory meatus
Canal leading to tympanic membrane

14. Special Somatic Receptors Infrared Receptors
Pits that open to surface
Btwn epidermal scales
Loreal pits
Pit vipers
Btwn nostril and eye
thermosensitive
Labial pits
Pythons
Other thermosensitive pits
Appear similar to neuromasts

15. Special Somatic Receptors Light Receptors
Photoreceptors
Lateral eyes
Median eye (3rd or pineal eye)
On top of head
Has lens and cornea
Do not form retinal images
Ex: lamprey, ganoid fish, larval anurans, lizards
Figure 16.14: Parietal eye.
Figure 16.15: Parapineal organ of iguana.

16. Special Somatic Receptors (cont.) Light Receptors
Median eye (3rd or pineal eye) (cont.)
Part of epiphyseal complex
Anterior parapineal is often photosensitive
Lamprey- both pineal and parapineal are photosensitive
Lizard- parapineal becomes 3rd eye
Frontal organs
3rd eye in larval frogs
Photosensitive
Figure 16.16: Epiphyseal complex of lamprey and embryonic and adult lizard.

17. Special Chemoreceptors Olfactory Organs
Ectodermal placodes
Sink into head
Internal naris- opening inside
Lungfish and tetrapods
External naris- opening outside
Fish
Higher vertebrates possess both types
Figure 16.17: Internal and external naris shown and vomeronasal organ.

18. Special Chemoreceptors (con’t) Olfactory Organs
Vomeronasal organ (Jacobson’s Organ)
Olfactory mechanisms isolated form nasal
Snakes and lizards
Insert forked tongue into organ
(a)
(b)
Figure 16.18: Snake collecting scent molecules (a) that are then delivered to the vomeronasal organ by the tongue (b).

19. Special Chemoreceptors Organs of Taste
Taste buds
Similar to neuromasts
In oral cavity and pharynx
Figure 16.19: Anatomy of the taste bud.

20. Endocrine Organs Ductless organs Secrete hormones
Derived from the 3 germ layers
Figure 16.20: Embryonic germ layers.

21. Pituitary Gland
Figure 16.21: Phylogeny of the vertebrate pituitary.

22. Pituitary Gland (Hypophysis)
Derived from ectoderm
Two divisions
Neurohypophysis (post. pit.)
Adenohypophysis (ant. pit.)
Figure 16.22: Anterior and posterior pituitary.

23. Pituitary Gland (cont.)
Neurohypophysis
Infundibulum of diencephalon
Stores hormones
Adenohypophysis
Cells evaginate away from stomadeum
Secretes hormones
Rathke’s pouch
Figure 16.23: Embryogenesis of the amniote pituitary.

24. Caudal Neurohemal Organ
Endocrine gland unique to some fish
Urophysis
Neurosensory organ
Occurs at tip of tail off of spinal cord

25. Pineal Derived from ectoderm Produces melatonin Gonadal regulator
Photoperiodism
Figure 16.24: Location of the pineal gland in the human brain.

26. Adrenal Gland Adrenal Medulla Adrenal Cortex Derived form ectoderm
From neurocrest cells
Adrenal Cortex
Derived from mesoderm
Figure 16.25: Cross section of Rt adrenal gland (top) and anatomical position of the adrenal glands.

27. Gonads Derived from mesoderm Within kidney tissue in some rayfin fish
Corpuscles of Stannius

28. Endodermal Origin Pancreatic Islets of Langerhans Thyroid gland
Foramen Cecum- reminant of thyroid evagination
Bursa of Fabricius
Outpocket of cloaca
Thymus in nature
Figure 16.27: Mammalian thyroid development.

29. Pharyngeal Pouches Derived from endoderm Fish Amphibians
Pouches 2, 3, 4, 5 (dorsal)- thymus
Pouch 5 (ventral)- ultimobranchial bodies
Amphibians
Pouches 3, 4, 5 (dorsal)- thymus
Figure 16.28: Contributions of the embryonic pharyngeal pouches to development of endocrine glands.

30. Pharyngeal Pouches (cont.)
Mammals
Pouches 3 & 4 (dorsal)- thymus
Pouches 3 & 4 (ventral)- parathyroids
No ultimobranchial bodies
Figure 16.29: Contributions of the embryonic pharyngeal pouches to development of endocrine glands.

31. Literature Cited
Figure
Figure 16.2, 16.4, 16.8, (b), 16.15, & Kent, George C. and Robert K. Carr. Comparative Anatomy of the Vertebrates. 9th ed. McGraw-Hill, 2001.
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32. Literature Cited
Figure
Figure
Figure
Figure 16.21, 16.23, 16.27, & Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002.
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