66: Phylogeny and development of the skin sense organs, taste, and olfactory organs Flashcards
What are the types of sensory organs in vertebrates?
- Somatic Sensory Organs: Detect external environmental stimuli.
- Visceral Sensory Organs: Monitor internal environmental conditions.
- General Sensory Organs: Distributed across the body, sensing various stimuli.
- Special Sensory Organs: Located primarily in the head, specialized for specific senses.
What is the function of the lateral line system in aquatic vertebrates?
The lateral line system features pores with hair-like structures connected to nerve endings, enabling the detection of pressure changes and vibrations in the water.
What are the functions of the olfactory organ?
- Sensory Perception: Primarily involved in the detection of smells.
- Pheromone Detection: Plays a crucial role in recognizing pheromones.
- Prey Detection: Assists in identifying prey through scent.
What types of sensory receptors are found in the skin?
Types include chemo-, mechano-, photo-, baro-, proprio-, osmo-, thermo-, and electromagnetic receptors.
What is a neuromast?
A neuromast is a sensory organ in aquatic vertebrates that aids in the perception of water movement, pressure, and vibrations.
What are some skin-sensitive structures in terrestrial vertebrates?
- Tadpoles: Tactile papillae on the lips.
- Snakes: Tentacles on snouts, with the tongue serving as the primary touch organ.
- Reptiles: Enhanced touch sensitivity in feet and tails for climbing.
- Birds: Lack nerve endings in the epidermis but possess tactile receptors in the dermis, including Herbst and Grandry corpuscles, and Merkel nerve endings.
How are olfactory receptors organized in the olfactory epithelium?
- Neurons: Covered with non-motile cilia immersed in mucus to capture odor molecules.
- Odorant-Binding Proteins: Serve as olfactory receptors that bind odor molecules.
- Supporting Cells: Provide metabolic and structural support to the epithelium.
- Basal Cells: Function as stem cells, capable of differentiating into either supporting or olfactory cells.
- Bowman’s Gland: Secretes proteins that help dissolve and trap odors.
What is the vomeronasal (Jacobson’s) organ, and what is its function?
- Structure: A paired sac lined with olfactory epithelium, known as the vomeronasal or Jacobson’s organ, found in most tetrapods.
- Function: Detects low volatility odorants close up (e.g., from food) and pheromones.
- What is the location and mechanism of vomeronasal (Jacobson’s) organ?
o In Some Amniotes: Located in the oral cavity vault. Snakes, for instance, use their forked tongues to bring air-sampled odorants to it.
o More Commonly: Situated at the nasal cavity base, linking to the oral cavity via a nasopalatine duct that opens into the incisive foramen. Animals like horses and cats exhibit the flehmen response—lifting the upper lip to close the nostrils and inhaling through the mouth—to expose this organ to air odorants.
How does the olfactory organ develop in embryos?
- Origins: Formed from neural crest cells and placode cells at the nervous system’s periphery.
- Development Process:
o Olfactory Placodes: Form from placode cells, also contributing to eye lens formation.
o Olfactory Vesicle: Develops and projects sensory neurons into the olfactory bulb.
o Microvillous Neurons: Derive specifically from neural crest cells.
What is the function and presence of Jacobson’s organ (vomeronasal organ) in animals?
- Function: Facilitates chemical communication, including sexual readiness and prey tracking.
- Presence:
o Common in: Tetrapods, with significant development in monotremes, marsupials, insectivores, and many carnivores.
o Variable in: Primates, underdeveloped in Old World monkeys and apes.
o Absent/Underdeveloped in: Most turtles, crocodiles, birds, certain bats, and aquatic mammals.
o Amphibians: Found within the main nasal cavity.
o Reptiles: Has a separate cavity for chemical delivery via the tongue and oral membranes.
What is the function of choanae?
- Definition: Posterior nostrils that open into the oral cavity.
- Primary Function: Allows air passage for nasal breathing, crucial for the respiratory adaptation in tetrapods and lungfish ancestors.
What is the function of olfaction in fishes?
Solely for olfaction, isolated from the respiratory system.
What are the cell types in the olfactory organ?
- Olfactory Receptor Cells
- Basal Cells
- Supporting Cells
What are tactile organs in terrestrial vertebrates?
Tactile papillae in tadpoles, tentacles on snake snouts, sensitive feet and tails in climbing reptiles.
