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Gross Anatomy SESSION 13 Dr. Firas M. Ghazi Orbital region Curricular Objectives By the end of this session students are expected to: Theory 1. Define the orbital region and review the location of its main content 2. Recall the location, boundaries and landmarks of orbit and the spaces related 3. Outline the layered structure of the eyelids and the muscles acting on it 4. Describe the conjunctival sac and its functional importance 5. List the structures of the lacrimal apparatus and acknowledge their function 6. Summarize the nervous control of lacrimation 7. List the main content of the orbital cavity 8. Underline the names, attachment, action and nerve supply of extra ocular muscles 9. Paraphrase the process of eye blinking, its anatomical control & functional importance 10. Outline the three coats of the eye ball and their subdivisions 11. Discuss the structure & nutrition of the cornea & its importance in the process of vision 12. Summarize the parts and functions of the ciliary body 13. Review the two muscles of the iris, their actions and nerve supply 14. Describe the different parts of the retina and its role in the process of vision 15. Outline the cavities and other content within the eye ball 16. Review the structure, attachment and function of the lens 17. Discuss the applied anatomy of corneal, accommodation and light reflexes Practical 1. Label the major content of the orbital region 2. Identify major landmarks and foramina within the orbital cavity 3. State the main structures passing through major foramina of the orbit 4. List and locate the main spaces adjacent to the orbital cavity 5. Mark the parts of the eyelids & name the space with which upper eyelid communicates 6. Label the muscles contributing to eye blinking and state their nerve supply 7. Recognize the conjunctival sac and its parts 8. Locate the different parts of lacrimal apparatus & name the nerve supplying the gland 9. Distinguish the extra ocular muscles and state the nerve supply of each 10. Trace the optic nerve and state its function 11. Identify the three coats of the eye ball and their different parts 12. Locate the eye structures involved in corneal, light and accommodation reflexes 13. State the nerves involved in corneal reflex 14. Label the structures of living human eye visible by direct inspection Selected references and suggested resources Clinical Anatomy by Regions, Richard S. Snell, 9th edition Grant's Atlas of Anatomy, 13th Edition McMinn's Clinical Atlas of Human Anatomy, 7th Edition Anatomy for Babylon medical students (facebook page) Anatomy for Babylon medical students (youtube channel) Human Anatomy Education (facebook page) Human anatomy education (youtube channel) Feedback and suggestions http://goo.gl/forms/SjyjGeUpvH Further assistance on: University website: http://staff.uobabylon.edu.iq/site.aspx?id=93 Page 1 Gross Anatomy SESSION 13 Dr. Firas M. Ghazi Session check list Clinical highlights Clinical problems include refractive errors, red eye, foreign body, Cataract, & Glaucoma Many eye problems like exophthalmus, and retinopathy are caused by systemic diseases Suggested links and videos 1. http://www.healthline.com/human-body-maps/eye (3D interactive eye anatomy ) 2. https://youtu.be/TXFt1Ikl__I (Eye ball and extrinsic muscles) 3. https://youtu.be/RE1MvRmWg7I (function of the eye) 4. https://youtu.be/p_xLO7yxgOk (accommodation reflex) 5. https://youtu.be/cldYYtejPwo (corneal reflex) Orbital Cavity It contains the eyeball, the extraocular muscles, the optic nerve and three more cranial nerves Eye lids They consist of five layers (From superficial to deep): Skin, Superficial fascia, Orbicularis oculi (palpebral fibers), Orbital septum, & Conjunctiva The Orbital septum is the framework of eyelids it is made of palpebral fascia which extends from the orbit margins and the tarsal plate The sub-aponeurotic space (scalp) is continuous with upper eyelid deep to orbicularis oculi The conjunctival sac is a potential space between the palpebral and bulbar conjunctiva The superior & inferior fornices are made by reflection of conjunctiva from lids to eye ball Lacrimal apparatus (the pathway of the tears) The lacrimal apparatus consists of all the structures concerned with secretion and drainage of lacrimal (tear) fluid Lacrimal gland & Ducts >> Conjunctival sac >> Lacrimal puncta >> Lacrimal canaliculi >> Lacrimal sac >> Nasolacrimal duct Ducts of the lacrimal gland pierce the lateral part of the superior fornix Lacrimation is under parasympathetic control Extra-ocular muscles and the eye movement Are muscles within the orbital cavity but outside the eyeball There are six muscles moving the eyeball and one muscle elevate the upper eyelid They move the eye outward (abduct) inward (adduct) upward (elevate) downward (depress) Conjugate movements is said to occur when both eyes move in the same direction Nerve supply of the extra-ocular muscles: L6(SO4)3 Levator palpebrae superioris is composed of two parts. One with skeletal muscle fibers and other with smooth muscle fibers. Each part is innervated differently Memorizing the muscles and the nerves responsible for individual eye movement is of great clinical importance to help diagnose many ophthalmological and neurological illnesses Three coats of the eye ball They eye ball is made of three layers forming its internal structure 1. Fibrous coat (external layer): Sclera/ Cornea/ Corneoscleral junction (limbus) 2. Vascular (uveal) coat (middle layer): Choroid/ Ciliary body/ Iris 3. Nervous coat (internal layer): Retina/ Macula lutea/ Fovea centralis/ Optic disc Further assistance on: University website: http://staff.uobabylon.edu.iq/site.aspx?id=93 Page 2 Gross Anatomy SESSION 13 Dr. Firas M. Ghazi The cornea is avascular and nourished by permeation from capillaries at the limbus, aqueous humour, and lacrimal fluid The corneal reflex is the closure of the eyelids on touching the cornea The ciliary body is a complex of three structures. Its main functions are: a) Secrete aqueous humour b) Suspend the lens via suspensory ligaments c) Focus the lens to adapt for near vision The iris has two muscles a) Constrictor pupillae (parasympathetic supply) b) Dilator pupillae (sympathetic supply) The retina is multilayered structure contain photoreceptor cells called rods and cones The optic disc is where all nerve fibers from retinal ganglion cells collect to exit as optic nerve Circulation of aqueous humor The aqueous humor flow in this direction: Posterior chamber >> pupil >> anterior chamber >> Iridocorneal angle >> canal of Schlemm Obstruction of aqueous humor flow will increase intraocular pressure (glaucoma). Lens It tend to assume spherical shape but the contraction of ciliary body make it less convex Its main function is the accommodation for near vision Nice to know: When the eye is open and looking straight ahead, the upper lid just covers the upper margin of the cornea. Knowing this fact help diagnose exophthalmos Ptosis is the drooping of upper eyelid as a result of paralysis of Levator palpebrea superioris The red eye effect seen in flash photography is due to light being reflected from the highly vascular choroid layer. Lab activity list For each task below, identify the listed structures then answer the related questions Task 1 (Orbit and orbital content): Orbital opening/ orbital margin/ Supraorbital notch (Foramen) Roof/ floor/ medial wall/ lateral wall/ apex Inferior orbital fissure/ Superior orbital fissure/Optic canal/ Nasolacrimal canal Extra ocular muscles/ eyeball/ optic nerve What are the structures passing through the superior orbital fissure? What are the structures passing through the optic canal? Task 2 (Spaces related to different walls of the orbit): Anterior cranial fossa/ middle cranial fossa/ Pterygopalatine fossa Maxillary sinus/ ethmoid sinuses The inferior orbital fissure connects the orbit with two spaces. Name them The superior orbital fissure connects the orbit with _____________________ Further assistance on: University website: http://staff.uobabylon.edu.iq/site.aspx?id=93 Page 3 Gross Anatomy SESSION 13 Dr. Firas M. Ghazi Task 3 (Eye lids/ palpebrae): Upper and lower eye lids/ lashes/ palpebral fissure Skin and conjunctival surfaces of the eyelids/ mucocutaneous junction Superior and inferior tarsal plates/ Medial and Lateral palpebral ligaments Levator palpebrae superioris/ orbicularis oculi (palpebral & orbital parts) Superior and inferior fornices Levator palpebrae superioris muscle insert into ______________________ Which muscle control forceful closure of the eyelids? Which muscle opens the eye? Task 4 (The lacrimal apparatus): Lacrimal gland/ conjunctival sac/ Lacus lacrimalis Lacrimal punctum/ Lacrimal canaliculus and Lacrimal sac/ Nasolacrimal duct What is the function of the lacrimal fluid? Which nerve supply the lacrimal gland? Closure of the nasolacrimal duct will cause ____________________ Task 5 (The extraocular muscles): Superior rectus/ Inferior rectus/ Medial rectus/ Lateral rectus Superior oblique/ Inferior oblique Superior and inferior recti rotate the eye ball medially why? To which part of the orbit the four recti attach? How to identify the recti from the oblique muscles? The Levator palpebrae superioris muscle lies __________________ to recti (superficial/deep) Task 6 (Coats of the eye ball): Sclera/ Cornea/ Corneoscleral junction (limbus) Choroid/ Ciliary body/ Iris Retina/ Macula lutea/ Fovea centralis/ Optic disc >>> Optic nerve Which of the structures above provide attachment to the extraocular muscles? Which cranial nerve supplies the cornea? Which of these structures is called the blind spot and why? The structure that has cones only is ___________________ Task 7 (Content and spaces of the eye ball): Anterior compartment: Anterior chamber/ Pupil/ Posterior chamber Lens Posterior compartment: Vitreous body Draw a diagram showing the refractive apparatus of the eye Lens can become more spherical by _________________ Further assistance on: University website: http://staff.uobabylon.edu.iq/site.aspx?id=93 Page 4 Gross Anatomy SESSION 13 Dr. Firas M. Ghazi Review questions: 1. Name the muscles that can elevate the eye 2. Which nerve is injured if the eye cannot be abducted? 3. What are the afferent and efferent limbs of corneal reflex? 4. Draw a simple diagram labeling the eye structures and nerves involved in accommodation reflex? 5. Regarding the picture on the right A. Structure (1) meets the cornea at…….. B. Colored structure (2) is called……… 5 4 C. The space behind structure (3) is called……. D. Which muscle opposes the action of structure (4)? 2 E. Parasympathetic ganglion supplying (5) is…….. F. Which one of these structures is involved in 1 corneal reflex? 3 Homework 1- There is a difference in the pattern of blood supply of the sclera and cornea. A. Explain B. How does that affect the healing process of these two structures? C. Soft plastic contact lenses worn for long periods must be permeable to the air. Why? 2- A 40-year-old male presented with headache and impaired vision of his left eye. Examination revealed that his left eye was displaced downward and laterally, with ptosis, and dilated pupil. A. Which nerve is most likely affected? B. List the extra ocular muscles that are NOT likely affected. C. Explain the ptosis in this case. D. What muscle causes pupil to dilate? What nerve supply it? 3- At one station of clinical OSCE examination, a 6th year medical student was prompted to examine the light reflex of a patient`s eye. Later on he had to interpret his findings by recalling his anatomical knowledge regarding this reflex. A. What is the afferent limb of this reflex? B. What is the efferent limb of this reflex? C. Name the muscle constricting the pupil 4- What is Horner’s syndrome and what features of this syndrome are seen in the picture below? Horner’s syndrome: Image source: http://dxline.info/diseases/horner-syndrome Further assistance on: University website: http://staff.uobabylon.edu.iq/site.aspx?id=93 Page 5