Comparative AnatomyComparative AnatomySensory OrgansSensory Organs

KardongKardongChapter 17 Chapter 17

Part 16

Sense OrgansSense Organs

Monitor external and internal environmentMonitor external and internal environment Somatic or visceral receptorsSomatic or visceral receptors Specific or generalSpecific or general

Special Somatic ReceptorsSpecial Somatic ReceptorsNeuromastsNeuromasts

In skin of fish and amphibiansIn skin of fish and amphibians Monitors mechanical, electrical, and Monitors mechanical, electrical, and

chemical stimulichemical stimuli Ampullae of Lorenzini in shark snoutAmpullae of Lorenzini in shark snout

Figure 16.1. Ampullae of Lorenzini in shark.

Special Somatic Receptors Special Somatic Receptors (cont.’d)(cont.’d)

NeuromastsNeuromasts Pit organs along shark gill Pit organs along shark gill

regionregion Lateral line canalLateral line canal

Linear seriesLinear series Derived from ectodermal Derived from ectodermal

placodes placodes Figure 16.2. External openings of neuromast organs in Squalus.

Figure 16.3. Neuromast organ and lateral line canal in a fish.

Special Somatic ReceptorsSpecial Somatic ReceptorsMembranous Labyrinth Membranous Labyrinth

Vertebrates have pair of fluid filled Vertebrates have pair of fluid filled membranous labyrinthsmembranous labyrinths

Filled with endolymphFilled with endolymph Surrounded by perilymphSurrounded 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).

Fig. 16.6. Membranous labyrinths of vertebrates (book figure 17.34).

Special Somatic Receptors (cont.’d)Special Somatic Receptors (cont.’d)Membranous LabyrinthMembranous Labyrinth

The vestibular apparatusThe vestibular apparatus Semicircular canals, Semicircular canals,

utriculus, and sacculusutriculus, and sacculus Inside canals:Inside canals:

OtolithsOtoliths Sensory hairs - perceive Sensory hairs - perceive

motion (modified motion (modified neuromast)neuromast)

Angular acceleration Angular acceleration detected by the cristae of detected by the cristae of semicircular canalssemicircular canals

Linear motion and gravity Linear motion and gravity detected by maculae of detected by maculae of utriculus and sacculus.utriculus and sacculus.

Figure 16.7. Vestibular apparatus.

Figure 16.8. Human anatomy of the ear.

Figure 16.9. Anlagen of amniote inner ear (otocyst). Embryonic head (a) and cross section of head (b).

Special Somatic Receptors (cont.’d)Special Somatic Receptors (cont.’d)Membranous Labyrinth Membranous Labyrinth

LagenaLagena Out pocketing of Out pocketing of

sacculus wallsacculus wall Gives rise to cochlea in Gives rise to cochlea in

mammalsmammals Organ of CortiOrgan of Corti

Figure 16.10. Cochlea and organ of Corti in mammal.

Special Somatic Receptors (cont.’d)Special Somatic Receptors (cont.’d)Membranous LabyrinthMembranous Labyrinth

Weberian ossiclesWeberian ossicles Fish transmit sound wavesFish transmit sound waves Modified transverse Modified transverse

processprocess Sinus impar (some fish)Sinus impar (some fish)

Assists in transport of Assists in transport of soundsound

Figure 16.11. (a) Weberian ossicles (b) Weberian apparatus for transmitting swim bladder vibrations to ear.

(a)

(b)

Special Somatic Receptors Special Somatic Receptors (cont.’d)(cont.’d)

Membranous Labyrinth Membranous Labyrinth

Middle Ear of TetrapodsMiddle Ear of Tetrapods

Canal from evagination of 1Canal from evagination of 1stst pharyngeal pouchpharyngeal pouch

Eustachian tubeEustachian tube Communication between Communication between

pharynx and middle earpharynx and middle ear

Figure 16.12. Position of Eustachian tube.

Outer, Middle, and Inner Ear of a Bat

Figure 16.13. Bat ear(book figure 17.44).

Special Somatic Receptors Special Somatic Receptors (cont.’d)(cont.’d)

Membranous Labyrinth Membranous Labyrinth

Middle Ear of TetrapodsMiddle Ear of Tetrapods Bones:Bones:

Malleus, incus, and Malleus, incus, and stapesstapes

Derived from 1Derived from 1stst and 2 and 2ndnd visceral archesvisceral arches

Stapes is columella in Stapes is columella in reptiles and birdsreptiles and birds

Figure 16.14. Middle ear bones.

Special Somatic Receptors Special Somatic Receptors (cont.’d)(cont.’d)

Membranous Labyrinth Membranous Labyrinth

16.15. Sensory receptors: Cristae (in semicircular canals)and maculae (within sacculusand utriculus of inner ear (book figure 17.45).

Special Somatic Receptors Special Somatic Receptors (cont.’d)(cont.’d)

Membranous Labyrinth Membranous Labyrinth Middle Ear of TetrapodsMiddle Ear of Tetrapods

Figure 16.16. Development of the middle ear bones.

Outer Ear of TetrapodsOuter Ear of Tetrapods PinnaePinnae Ear drum set back into skullEar drum set back into skull

Crocs, birds, and mammalsCrocs, birds, and mammals Tympanic membrane on outsideTympanic membrane on outside

Frogs Frogs External auditory meatusExternal auditory meatus

Canal leading to tympanic membraneCanal leading to tympanic membrane

Special Somatic Receptors Special Somatic Receptors (cont.’d)(cont.’d)

Pits that open to surfacePits that open to surface Between epidermal scalesBetween epidermal scales

Loreal pitsLoreal pits Pit vipersPit vipers Between nostril and eyeBetween nostril and eye thermosensitivethermosensitive

Labial pitsLabial pits PythonsPythons Other thermosensitive pitsOther thermosensitive pits Appear similar to neuromastsAppear similar to neuromasts

Special Somatic ReceptorsSpecial Somatic ReceptorsInfrared ReceptorsInfrared Receptors

16.17. Infrared receptors in snakes(book figure 17.30).

Special Somatic ReceptorsLight Receptors

Pineal Complex

Depending upon the species, the epithalamus may evaginate toproduce up to four discrete organs.

• Paraphysis (most anterior)• Dorsal sac• Parietal organ – no retinal image• Epiphysis(two or more present = Pineal complex)

Fig. 16.19. Pineal complex (a). Generalizedparietal eye (b) (book figure 17.28)

Special Somatic ReceptorsLight Receptors (cont.’d)

Figure 16.20. Pineal complex in lower vertebrates (book figure 17.29).

Pineal Complex (cont.’d)

Figure 16.21. Parietal eye of iguana (book figure 17.19).

Special Somatic Receptors Special Somatic Receptors (cont.’d) (cont.’d)

Light ReceptorsLight Receptors Median eye (3Median eye (3rdrd or pineal eye) or pineal eye)

(con’t)(con’t) Part of epiphyseal (pineal) Part of epiphyseal (pineal)

complexcomplex Anterior parapineal is often Anterior parapineal is often

photosensitive photosensitive Lamprey- both epiphysis Lamprey- both epiphysis

and parietal organand parietal organBoth photosensitiveBoth photosensitive Lizard- parietal becomes 3Lizard- parietal becomes 3rdrd

eyeeye Frontal organsFrontal organs

33rdrd eye in larval frogs eye in larval frogs PhotosensitivePhotosensitive

Figure 16.22. Epiphyseal (pineal) complex of lamprey and embryonic and adult lizard.

Special Somatic ReceptorsSpecial Somatic Receptors Light Receptors Light Receptors

PhotoreceptorsPhotoreceptors Lateral eyesLateral eyesA reflective surface, the A reflective surface, the tapetum lucidum, tapetum lucidum, is found in the choroidis found in the choroidlayer in some nocturnallayer in some nocturnalmammals and produces themammals and produces the““eye-shine” in car headlightseye-shine” in car headlights

Figure 16.23. Lateral eyes(book figure 17.18).

Special ChemoreceptorsSpecial ChemoreceptorsOlfactory OrgansOlfactory Organs

Ectodermal placodesEctodermal placodes Sink into headSink into head Internal naris- opening insideInternal naris- opening inside

Lungfish and tetrapodsLungfish and tetrapods External naris- opening outsideExternal naris- opening outside

Fish Fish Higher vertebrates possess both Higher vertebrates possess both

typestypesFigure 16.24. Internal and external naris shown and vomeronasal organ.

Special ChemoreceptorsSpecial Chemoreceptors (cont’d.) (cont’d.)

Olfactory OrgansOlfactory Organs

Vomeronasal organ Vomeronasal organ (Jacobson’s Organ)(Jacobson’s Organ) Olfactory mechanisms Olfactory mechanisms

isolated form nasalisolated form nasal Snakes and lizardsSnakes and lizards Insert forked tongue into Insert forked tongue into

organorgan

(a)

(b)

Figure 16.25. Snake collecting scent molecules (a) that are then delivered to the vomeronasal organ by the tongue (b).

Snake Vomeronasal Organ (cont.’d)

Figure. 16.26. Tongue flicking (book figure 17.14).

Special ChemoreceptorsSpecial ChemoreceptorsOrgans of TasteOrgans of Taste

Taste budsTaste buds Similar to neuromastsSimilar to neuromasts

In oral cavity and pharynxIn oral cavity and pharynx

Figure 16.27. Anatomy of the taste bud.

Special ChemoreceptorsSpecial ChemoreceptorsOrgans of TasteOrgans of Taste (cont.’d)(cont.’d)

Figure 16.28. Distribution of taste buds on the human tongue (book figure 17.15).