Comparative Anatomy Sensory Organs Kardong Chapters 15 Part 16

Sense Organs Monitor external and internal environment Monitor external and internal environment Somatic or visceral receptors Somatic or visceral receptors Specific or general Specific or general

Special Somatic Receptors Neuromasts In skin of fish and amphibians In skin of fish and amphibians Monitors mechanical, electrical, and chemical stimuli Monitors mechanical, electrical, and chemical stimuli Ampullae of Lorenzini in shark snout Ampullae of Lorenzini in shark snout Figure Ampullae of Lorenzini in shark.

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

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

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

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

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

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

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

Middle and Inner Ear of a Bat Bat ear.

Special Somatic Receptors (cont.) Membranous Labyrinth Middle Ear of Tetrapods Bones: Bones: Malleus, incus, and stapes Malleus, incus, and stapes Derived from 1 st and 2 nd visceral arches Derived from 1 st and 2 nd visceral arches Stapes is columella in reptiles and birds Stapes is columella in reptiles and birds Figure 16.13: Middle ear bones.

Special Somatic Receptors (cont.) Membranous Labyrinth Crista and macula of inner ear.

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

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

Pits that open to surface Pits that open to surface Between epidermal scales Between epidermal scales Loreal pits Loreal pits Pit vipers Pit vipers Between nostril and eye Between nostril and eye thermosensitive thermosensitive Labial pits Labial pits Pythons Pythons Other thermosensitive pits Other thermosensitive pits Appear similar to neuromasts Appear similar to neuromasts Special Somatic Receptors Infrared Receptors Infrared receptors in snakes (book figure 17.30).

Special Somatic Receptors Light Receptors Pineal Complex Depending upon the species, the epithalamus may evaginate to produce up to four discrete organs. Paraphysis (most anterior) Dorsal sac Parietal organ – no retinal image Epiphysis (two or more present = Pineal complex) Fig Pineal complex (a). Generalized parietal eye (b) (book figure 17.28)

Pineal Complex (cont.) Figure Parietal eye of iguana (book figure 17.19).

Special Somatic Receptors Light Receptors Photoreceptors Photoreceptors Lateral eyes Lateral eyes

Special Somatic Receptors (cont.) Light Receptors Median eye (3 rd or pineal eye) (con’t) Median eye (3 rd or pineal eye) (con’t) Part of epiphyseal (pineal) complex Part of epiphyseal (pineal) complex Anterior parapineal is often photosensitive Anterior parapineal is often photosensitive Lamprey- both epiphysis and parietal organ Lamprey- both epiphysis and parietal organ Both photosensitive Lizard- parietal becomes 3 rd eye Lizard- parietal becomes 3 rd eye Frontal organs Frontal organs 3 rd eye in larval frogs 3 rd eye in larval frogs Photosensitive Photosensitive Figure Epiphyseal (pineal) complex of lamprey and embryonic and adult lizard.

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

Special Chemoreceptors (cont.) Olfactory Organs Vomeronasal organ (Jacobson’s Organ) Vomeronasal organ (Jacobson’s Organ) Olfactory mechanisms isolated form nasal Olfactory mechanisms isolated form nasal Snakes and lizards Snakes and lizards Insert forked tongue into organ 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).

Snake Vomeronasal Organ

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