Study Notes on Human Anatomy: General and Special Senses

Gustation – Sense of Taste
Anatomical Structures and Functions:

  • Gustatory receptors: Housed in specialized taste buds.

  • Taste buds: Contain about 4040 gustatory cells each, located along the sides of epithelial projections (papillae).

  • Papillae: Epithelial projections on the dorsal surface of the tongue where taste buds lie. There are four types:

    1. Filiform Papillae: Located on the anterior 2/3 of the tongue; do not house taste buds and have no sensory role. ( friction and bringing things to mouth)

    2. Fungiform Papillae: Primarily on the tip and sides of the tongue; each contains a few taste buds.

    3. Vallate (Circumvallate) Papillae: Arranged in an inverted V shape on the posterior dorsal surface; least numerous but largest, containing a high number of taste buds. Each is surrounded by a deep, narrow depression.

    4. Foliate Papillae: Extend as ridges on the posteriolateral sides of the tongue; house only a few taste buds during childhood; not well developed on the human tongue.

Taste Sensations:

The tongue can detect five basic taste sensations, with a possible sixth:

  • Salty: Metal ions.

  • Sweet: Organic compounds. (Sugar glucose)

  • Sour: Acids. (Low ph (7))

  • Bitter: Alkaloids. (Tylenol (above 7) when not coated bitter asf)

  • Umami: Detects amino acids, providing a pleasant taste. (Chicken soup veggie broth tasty asf)

  • Water: Possible detection in the pharynx.



Olfaction – Sense of Smell
Anatomical Structures and Functions:

  • Receptor cells: Bipolar neurons that detect odors and synapse with olfactory bulbs.

  • Olfactory bulbs: Where receptor cells synapse. CN1

  • Supporting cells: Sandwich the olfactory nerves and sustain and maintain the receptors cushion as well.

  • Basal cells: Function as stem cells to replace olfactory epithelium components. (When damaged(ex hot oven and heat hits you and burn nose)

  • Olfactory System: can recognize 50-60 different primary odors

  • Olfactory epithelium: Covers the inferior surface of the cribriform plate, nasal conchae, and nasal septum.

  • Glands (in olfactory epithelium): Secrete thick, pigmented mucus.

Number of Primary Odors:

The olfactory system can recognize approximately 50−6050-60 different primary odors.



Vision, Sense of Sight
Anatomical Structures and Functions:

  • Visual Receptors (Photoreceptors): Located in the eyes to detect light, color, and movement.

  • Accessory Structures of the Eye:

    • Conjunctiva: Provides a superficial covering over the anterior exposed surface of the eye.

    • Eyebrows, Eyelashes, & Eyelids: Prevent foreign objects from contacting the eye.

    • Lacrimal Glands: Keep the exposed surface moist, clean, and lubricated. (Allow us to cry)

    • Extra-Ocular Muscles: Control eye movement.

  • Cavities and Chambers of the Eye: The internal space of the eye is divided by the lens into two separate cavities:

    • Anterior Cavity: Space anterior to the lens and posterior to the cornea; contains aqueous humor.

    • Posterior Cavity: Area behind the lens; contains vitreous humor.

    • The iris further subdivides the anterior cavity into two chambers:

      • Anterior Chamber: Between the iris and cornea.

      • Posterior Chamber: Between the lens and iris.

  • Humors of the Eye:

    • Vitreous Humor: Maintains the shape of the eye; composed of thick gelatinous material.

    • Aqueous Humor: Removes waste products; secreted into the posterior chamber, flows around the lens, through the pupil, and into the anterior chamber, draining via the canal of Schlemm (scleral venous sinus).

Visual Information Transmission and Processing:

  • Each optic nerve conducts visual stimulus information.

  • At the optic chiasm, some axons from the optic nerve decussate (cross).

  • The optic tract on each side contains axons from both eyes.

  • Visual stimulus information is processed by the thalamus and then interpreted by visual association areas in the cerebrum.

Hearing and Equilibrium
Anatomical Structures and Functions Associated with Hearing and Equilibrium:

  • External Ear Composition:

    • Pinna/Auricle, Helix/Antihelix, Tragus/Antitragus: Collect and funnel sounds.

    • External Auditory Canal (Meatus): Directs sound waves inward.

    • Tympanic Membrane: Functions to funnel sounds into the canal, vibrating in response to sound waves.

  • Middle Ear Structure:

    • Contains an air-filled tympanic cavity.

    • Medially, bony walls containing the oval window and round window separate the middle ear from the inner ear.

    • Houses the auditory ossicles (Malleus - Hammer, Incus - Anvil, Stapes - Stirrup) which transmit vibrations from the tympanic membrane to the inner ear.

  • Inner Ear Components: Receptors for hearing and equilibrium are housed in fluid-filled tubes/chambers:

    • Membranous Labyrinth: Contains endolymph.

    • Bony Labyrinth: Contains perilymph.

    • Vestibule, semicircular canals, utricle, saccule, ampulla/cupula, maculae, cochlea: These structures, including the cochlear, tympanic, and vestibular ducts, organ of Corti, and tectorial membrane, are responsible for converting sound waves into mechanical movement and sensing equilibrium.

Anatomical Position and Function of the Auditory Tube (Eustachian Tube):

  • Anatomical Position: Maintains an open connection with the atmosphere, opening into the nasopharynx (upper throat) from the middle ear.

  • Function: Air movement through this tube due to chewing, yawning, and swallowing allows for pressure equalization on both sides of the tympanic membrane, which is crucial for clear hearing and preventing discomfort.