Special Senses Anatomy - C. Martonos.pdf

Organs of Special Senses Vet Prep Structural and Functional Biology Dr. Cristian Martonos Previous lecturer Dr. Melissa Kehl The Ear Learning Objectives: 1. List the main segments of the ear. 2. Describe the main features of each segment and their function. 3. Differentiate between the organs of hea...

Organs of Special Senses Vet Prep Structural and Functional Biology Dr. Cristian Martonos Previous lecturer Dr. Melissa Kehl The Ear Learning Objectives: 1. List the main segments of the ear. 2. Describe the main features of each segment and their function. 3. Differentiate between the organs of hearing and sense of balance and name the cranial nerve serving each sense. The Ear 3 non-communicating segments: 1) External ear 2) Middle ear 3) Inner ear External Ear Middle Ear Inner Ear External ear Captures air vibrations and directs them towards the tympanic membrane Auricle (pinna) Parts: Auricle (pinna) – funnel shaped Ear canal Vertical canal Vertical part Horizontal part Horizontal Canal Middle Ear Functions: sound modulation Located in the tympanic part of the temporal bone of skull Middle Ear Tympanic membrane (ear drum) is connected to oval window by 3 auditory ossicles. sound Communicates with the pharynx via the auditory tube, to ensure air pressure inside the middle ear is equal to outside air pressure. Inner Ear Housed deep inside the temporal bone (24) Vestibulocochlear nerve (cranial nerve VIII) (21) – cochlear nerve (hearing) and vestibular nerve (balance) Comprises: Organ for hearing (cochlea – 16 ) Organs for balance (vestibular apparatus) semicircular canals – 13 utricle – 14 saccule – 15 Temporal Bone 23 – brain 22 – meninges 7 – auditory tube 21 – vestibulocochlear nerve 4 – tympanic membrane Textbook of Veterinary Anatomy fig 9.24 The Eye Learning Objectives: 1. List the three tunics of the eye and describe their sub-components and functions. 2. Describe how the optic nerve emerges from the retina. 3. Describe the main compartments of the eye. 4. Differentiate the aqueous humor from the vitreous body. 5. List the main protective adnexa of the eye. 6. List the intrinsic and extrinsic muscles of the eye and differentiate between their type (involuntary vs voluntary), their specific functions and innervation(somatic vs. autonomic-PsNS and SNS). Eye bulb – has 3 layers (tunics): Structural integrity Allows light to enter the eye Modulates the amount of light Modulates vision focus Provides blood supply and innervation Nervous Tunic Lateral View Reacts to light stimuli and outputs nervous impulses for the brain, to be interpreted as images Fibrous tunic 1. Cornea (transparent anterior ¼) 2. Sclera (opaque posterior ¾) – “white of the eye” Sclera Cornea Sclera Lateral View - sagittal section Vascular tunic 1. Choroid (14) Dense network of blood vessels in heavily pigmented connective tissue Tapetum lucidum – dorsal part, light reflecting area, avascular, when light hits reflects in iridescence (nocturnal adaptation) 2. Ciliary body (4) Thickening of choroid Has ciliary muscles attached to lens (3) to focus 3. Iris (7) Suspended between cornea and lens Opening in the center is the pupil Smooth muscle constrict and dilate pupil to regulate amount of light reaching the retina. Nervous Tunic (Retina) Anterior, thinner pigmented layer – has no photoreceptors Posterior, thicker layer of the retina contains photoreceptors and connects to the optic nerve (cranial nerve II) The optic disk is the region where axons emerge from the eye bulb. This creates a “blind spot” CHOROID Intrinsic Muscles of the Eye Are under involuntary control Ciliary muscles – Changes the shape of the lens for focusing. – Poorly developed in domestic animals. Pupillary muscles (in the iris) – Constrictor pupillae (circular fibers) – Dilator pupillae (linear, radial fibers) – Regulate the amount of light Extrinsic Muscles Are under voluntary control 4 Rectus (straight) muscles: – – – – Dorsal rectus (1) Ventral rectus (3) Lateral rectus (2) Medial rectus (4) 2 Oblique (curved) muscles: – Dorsal oblique (6) – Ventral oblique (5) Retractor bulbi mm. (7) Compartments and Chambers of the Eye The space between the cornea and the lens is divided by the iris in 2 CHAMBERS: 3 2 1) Anterior chamber from cornea to iris (3) 2) Posterior chamber from iris to lens (2) They communicate through the pupil They contain aqueous humor Vitreous chamber (4) from lens to fundus 4 Does not communicate with anterior compartment Contains vitreous humor 2 3 Adnexa of the Eye The orbit is incomplete in the dogorbital ligament Superior palpebra Eyelids (palpebrae) Lateral commissure Medial commissure Inferior palpebra Palpebral fissure Third eyelid (plica semilunaris) Concave fold of palpebral conjunctiva that protrudes from the medial angle of the eye. Supported by a T shaped cartilage Contains the superficial gland of the third eyelid Lacrimal gland Function: Make tears, and these keep the surface of the eye moist and clean, and provide nourishment. Lacrimal gland (9) located dorso-lateral to eye, secretes serous fluid Secretion flows over cornea Passes through lacrimal puncta and into lacrimal canaliculi (1, 5) Drains into nasolacrimal duct (3) The Nose Learning Objectives: 1. Describe the location of the olfactory mucosa in relation to the nasal cavity. 2. Describe the path of the olfactory nerve in relation to the canine skull. Olfactory mucosa The olfactory mucosa covers thin scrolls of bone belonging to the ethmoidal bone called ethmoidal conchae (red arrow). It is located in the caudal region of the nasal cavity >250 million olfactory receptors in their noses Olfactory sense The olfactory nerve (cranial nerve I) - made up of numerous axons that arise in the olfactory mucosa and pass through the cribriform foramina to the olfactory bulbs of the brain. The Tongue Learning objectives: 1. Describe the location of the taste buds in relation to the tongue. 2. Describe the sensory nerves servicing the taste sense and their distribution on the tongue. Main Functions of the Tongue: Prehension – picking up food Mastication – chewing the food Deglutition – swallowing the food Grooming Heat loss (in panting) in dogs Gustatory sensation - taste Taste buds and lingual papillae Taste buds have receptor cells that get stimulated by soluble substances. There are taste buds on vallate, foliate, and fungiform papillae. Taste vs Touch sensations – innervation The lingual branch of the Glossopharyngeal n. (IX) is sensory (taste + touch) from the caudal one third of the tongue. The lingual nerve is sensory from the rostral two thirds of the tongue: Touch sensation is sent to the brain from the trigeminal n. (V) Taste sensation is sent to the brain from a part of the facial n. (VII)