Optometry Head and Neck & Neuro PDF

Anatomy of Head and Neck Solomon  Skull Formed by two sets of bones 8 cranial bones (calvaria/cranium) – enclose brain 14 facial bones - forms face These 22 bones combine to form the cranial cavity and the facial features Most bones of the skull are fla...

Anatomy of Head and Neck Solomon  Skull Formed by two sets of bones 8 cranial bones (calvaria/cranium) – enclose brain 14 facial bones - forms face These 22 bones combine to form the cranial cavity and the facial features Most bones of the skull are flat bones Except for the mandible, all bones are firmly united by interlocking sutures Has vault and base nes of skull Facial bones form the anterior aspect The cranial bones enclose the brain Functions The bones of the skull provide A case to house the brain, the cranium Framework for the face cavities to house the organs of sight, taste, hearing & smell passages for air and food attachment sites for the teeth and muscle anial vault The cranial vault or calvaria forms the superior, lateral, and posterior aspects of skull 4  Cranial Base Cranial base forms the skull’s inferior aspect Three prominent ridges divide the base into fossae The brain rests on these cranial fossae  Cavities of Inthe Skullto the large cranial cavity there addition are many smaller cavities such as Middle ear, inner ear, Nasal, and Orbits cavities Several bones contain air filled sinuses Sinuses surround the nasal cavity thus referred to as the  Cranium Composed of eight flat bones surrounding and protecting the brain  Paired - parietal and temporal  Unpaired - frontal, occipital, sphenoid and ethmoid 7 Frontal bone Forms the anterior portion of the cranium; the forehead, roofs of the orbits, and most of the anterior cranial fossa Parts  Zygomatic process  Supraorbital notch (foramen) - transmit supraorbital nerve and vessels Frontal sinuses Sutures - coronal, frontonasal, frontomaxillary, zygomaticofrontal 8 Parietal bones Forms most of the superior & lateral aspects of the skull  Coronal Articulates with other cranial bones to form three major sutures  Lambdoid  Squamous suture Articulate s with each other at 9 Occipital bone Forms most of the posterior wall and base of skull Articulates with parietal, temporal and the first cervical vertebrae Bound foramen magnum Parts  Squamous  basilar Sutures- lambdoid, occipitomastoid 10  Occipital bone: landmarks Foramen magnum – large oval opening; communicate cranial cavity with vertebral canal Occipital condyles – oval processes on either side of foramen magnum; articulate with atlas to form atlanto-occipital joint External occipital protuberance – midline projection posteriorly External occipital crest - a ridge in the median plane from external occipital protuberance to foramen magnum Nuchal lines  Superior nuchal line  Inferior nuchal line 11 12  Temporal Bone Forms  Inferolateral aspects of the skull  Parts of the cranial floor Divided into four regions  Squamous  Tympanic  Mastoid  petrous 13  Temporal Bone Form the middle cranial fossa Houses internal and middle ear External acoustic meatus Landmarks – Jugular foramen: entry point for the internal jugular vein – Internal acoustic meatus: entry point for the auditory nerve – Stylomastoid foramen: exit for facial nerve – Carotid canal: entrance for the carotid artery – Mandibular fossa – inferiorly, receives condyle of mandible to form temporomandibular joint 14 15 Sphenoid bone Bone spanning the width of middle cranial fossa Resembles bat with stretched wings Articulates as central wedge with all cranial bones Parts  Consists of central body and three processes; greater and lesser wings and pterygoid process superior surface is termed as Sella turcica  Tuberculum sellae – anterior horn  Hypophyseal fossa - for pituitary gland  Dorsum sellae – posterior horn contain sphenoidal sinuses 16  Foramina Optic foramina – between body and lesser wing Superior orbital fissure – between greater and lesser wings Foramen rotundum, ovale and spinosum on greater wing 17  Ethmoid bone Forms anterior part of cranial floor, medial wall of orbit, superior portion of nasal septum Lies between nasal bones & sphenoid Contain sinuses 18  Facial bones Consists of 14 bones – Paired - maxilla, zygomatic, palatine, nasal, lacrimal, inferior nasal conchae – Unpaired - mandible and vomer 1. Nasal bones Forms bridge of the nose Thin, rectangular shape Fused medially Articulate with the  Frontal bone and  Maxillary bones  Nasal cartilages 19  2. Mandible Forms the lower jaw Largest, strongest bone of the face the only movable bone of the skull Houses lower dentition Two parts - the body and the two rami Symphysis menti - between right and left parts Mental foramen - transmit mental nerve and vessels 20 21 3. Maxillary bone Forms upper jaw and central portion of facial skeleton Surround anterior nasal aperture and unite in medial plane Articulates with all facial bones except mandible Forms upper dentition Surfaces - nasal, orbital, infratemporal, and anterior Parts – Body and Four processes - frontal, alveolar, zygomatic and palatine Body – houses maxillary sinus 22 4. Zygomatic bones Commonly called the cheekbones Form prominences of cheeks and inferolateral margins of orbits Articulate with the frontal, temporal, sphenoidal and maxillary bones Three processes - frontal, temporal and maxillary 23 Inferior Nasal Conchae  6. Lacrimal Bones Forms part of the medial border of each orbit Articulates with frontal, ethmoid & maxillae Forms part of Lacrimal fossa 25 7. Palatine bones L- shaped Parts Horizontal plate Vertical plate Orbital surface 26  8. Vomer Single, triangular bone Forms part of the nasal septum 27 nasal septum 28  Skull joints Sutures Immovable joint between skull bones 4 prominent Coronal suture - between frontal and the two parietal bones Sagittal suture - between the two parietal bones Lambdoid suture - between the two parietals and occipital bone Squamous suture - between parietal and temporal bones 29 30  Temporomandibular joint (TMJ) Formed by between mandible and temporal bone Is a modified hinge synovial joint Allow elevation & depression & protrusion & retraction. Supported by:- Muscles of mastication , Temporomandibular ligament, Stylomandibular ligament , Sphenomandibular ligament and Synovial membrane Nerve supply – Auriclotemporal and masseteric branches of mandibular nerve Arterial supply – the superficial temporal, middle meningeal and anterior tympanic branches of maxillary artery and ascending pharyngeal arteries. 32 33 Foramin a in the skull A) Anterior cranial fossa(ACF ) B) Middle cranial fossa(MCF ) C) Posterior cranial fossa(PCF )  Paranasal Sinuses The paranasal sinuses are air-filled extensions of the respiratory part of the nasal cavity into the following cranial bones: 4 paranasal sinuses Frontal, Ethmoid, Sphenoid, and Maxilla Communicate with the nasal cavity by ducts Function  Decrease skull bone weight  Warm, moisten and filter incoming air  Add resonance to voice 35  They are named according to the bones in which they are located 36  Age difference in the skull bone Skull at birth The cranium is large The bone of the face are small  1/8th of the size of the skull at birth  1/3rd of the size of the skull in adults There is no paranasal sinuses & teeth The maxillae are short Frontal (Metopic) suture between the two frontal bones Bones are connected by membranous sutures and fontanels Fontanels Membranous part of sutures Functions of fontanels:- Provide flexibility to skull To determine the progress of growth in the surrounding bones Degree of hydration of the baby State of the intracranial pressure  Fontanelle… Anterior Fontanelle closed during 18 month years old Posterior fontanelle begins to close during the first few months after birth by the end of the 1st year, it is small and no longer clinically palpable Sphenoidal and mastoid fontanelles, overlain by the temporalis muscle, fuse during infancy and are less important clinically  The Scalp A stiff structure coving the skull Hair bearing area over the neurocranium 41 Nerves of the scalp 10 nerves on each side, 5 in front of the auricle and 5 behind the auricle In front of the auricle – Motor - branch of facial nerve – Sensory -branches of all the 3 Behind the auricle divisions of trigeminal Motor - facial nerve Sensory – branches cervical spinal nerves 42 43  Blood supply Arteries of the scalp – numerous anastomoses between external and internal carotid arteries – Branches of the external carotid artery  Superficial temporal artery  Occipital artery  Posterior auricular artery – Branches of the internal carotid, via the ophthalmic artery  Supraorbital artery  Supratrochlear artery 44 45 Veins of the scalp Veins draining into the anterior facial vein – Supraorbital vein – Supratrochlear vein Veins draining into maxillary / external jugular veins – Superficial temporal vein – Occipital vein – Posterior auricular vein 46 Lymphatic drainage of the scalp and face Submandibular lymph nodes – forehead Parotid lymph nodes from the area of the scalp anterior to the auricle Mastoid (retro auricular) & occipital LN from the scalp behind the auricle Submental LN: from Lower Lip and chin 47  Fac The face is the anterior aspect of the head e of the face is determined by the Basic shape underlying bones The face plays an important role in communication. The face provides our identity as an individual human. Superiorly – the margins of the hair Inferiorly – the chin Laterally – the auricle (Ears) N.B. the forehead is common for the scalp and the face 48  Skin – Very vascular; wounds bleed profusely but heal rapidly – Rich in sebaceous and sweat glands – Lax except in ear and nose – Elastic and thick Superficial fascia – Contain facial muscles, nerves, vessels and fat (buccal fat pad in cheeks) Deep fascia – Absent except over parotid gland and buccinator muscle 50  Muscles of the face Lie in subcutaneous tissue Inserted in to the skin Named as muscles of facial expression Arranged in groups around the orbit, nose, mouth and auricles – functionally considered as regulators of openings Supplied from branches of facial nerve 51 Muscle Action Occipitofrontali Elevates eyebrows and wrinkles skin s (1, 2) of forehead; protracts scalp (indicating surprise or curiosity) Retracts scalp; increasing effectiveness of frontal belly Orbicularis oculi Closes eyelids (2, 3) Passing tear into lacrimal puncta by (orbital drawing the eye sphincter) Corrugator Draws eyebrow medially and inferiorly, supercilii 2 creating vertical wrinkles above nose (demonstrating concern or worry) Procerus plus Depresses medial end of eyebrow; transverse part wrinkles skin over dorsum of nose of nasalis 4 (conveying disdain or dislike) Alar part of Depresses ala laterally, dilating anterior Muscle Action Levator labii Part of dilators of mouth; retract Superioris 4 (elevate) and/or evert upper lip; Zygomaticus (showing sadness) minor 4 Zygomaticus Part of dilators of mouth; elevate labial major 4 commissure—bilaterally to smile (happiness); unilaterally to sneer (disdain) Buccinator Presses cheek against molar teeth; (cheek 4 works with tongue to keep food muscle) between occlusal surfaces and out of oral vestibule; resists distension (when blowing) Levator anguli Part of dilators of mouth; widens oral oris 4 fissure, as when grinning or grimacing Muscle Action Risorius 4 Part of dilators of mouth; Depressor depresses labial commissure anguli oris 5 bilaterally to frown (sadness) Depressor labii Part of dilators of mouth; retracts inferioris 5 (depresses) and/or everts lower lip (pouting, sadness) Mentalis 5 Elevates and protrudes lower lip; elevates skin of chin (showing doubt) Platysma 6 Depresses mandible (against resistance); tenses skin of inferior face and neck (conveying tension and Stress) erves of Face Sensory Nerves of the face Two sources Skin around the angle of the mandible by Greater auricular nerve (C 2, 3 ) The rest of the face by Trigeminal branches (CN V) 58  All facial muscles are innervated by the facial nerve (CN VII) via its 1.Posterior auricular branch 2.Temporal 3.Zygomatic 4.Buccal 5.Marginal mandibular 6.Cervical 60  Blood vessels of the face Arteries six arteries which have free anastomosis 1.From ophthalmic Supply artery the- two Supratro muscles and skin arteries chlear originatingofin the orbit forehead and  Supraorb scalp and ital superior conjunctiva 2. From external carotid Maxillary artery artery – 6 arterial Terminal branches Branches of & 2 Terminal branches Superficial External temporal artery Carotid Artery 61 Superficial Temporal Artery: supply facial muscles and skin of temporal frontal & temporal regions 62  Branches of External carotid artery 1. Facial Artery 2. Occipital artery 3. Posterior occipital artery 4. Superior thyroid artery 5. Lingual artery 6. Ascending pharyngeal artery 64 A. Facial artery arise from external carotid artery in the neck major blood supply of the face The main branches – Superior labial – upper lip – Inferior labial – lower lip – Lateral nasal – nose – Angular artery 65  Veins of Face 1. Supratrochlear veins Drain Anterior part of scalp 2. Supraorbital veins and forehead 3.Facial vein formed by union of supratrochlear and supraorbital veins at the medial angle of the orbit Tributaries - veins accompanying facial artery normally drain from angle of eye, nose and lips inferiorly but it may run Free anastomosis facial vein communicates with  Pterygoid venous plexus through deep facial vein  Cavernous sinuses through ophthalmic veins This area (nose, medial angle of eye and the upper lip) form danger 68 4.Superficial temporal : drain forehead and scalp 5.Retromandibular vein Formed by union of superficial temporal & maxillary veins Descend within parotid gland and at end divide into anterior and posterior divisions 69  The Parotid Region The posterolateral part of the facial region Space between mastoid process and neck and ramus of mandible Contents  Parotid gland – the largest salivary gland  Facial nerve and its branches (5)  External carotid artery and its branches  Facial vein  Lymph nodes 70  Structures with in the gland: superficial to deep – Facial nerve and its branches – Retromandibular vein – External carotid artery and its branches 71 Parotid Gland Is the largest of three paired salivary glands Is found on the Lateral part of head Inferior to external acoustic meatus Posterior to the ramus of the mandible Its duct, Stensen duct, approximately 5 cm long, opens into the vestibule of the oral cavity opposite the upper 2nd molar teeth 72 Facial nerve branch at risk during surgery here 73  Salivary Glands Saliva: mixture of water, ions, mucus, enzymes Saliva function: keep mouth moist starts enzymatic digestion cleansing and dissolving Lubricates pharynx to facilitate swallowing antibacterial and antiviral Other salivary glands 1. Submandibular glands 2. Sublingual glands 74 Submandibular Glands Is the second largest salivary gland in the floor of the oral cavity Its duct, Wharton's duct, opens into the floor of the oral cavity on the sides of the lingual frenulum Sublingual Glands Are the smallest and most deeply situated of the major salivary glands Lie in the floor of the mouth Numerous small sublingual ducts, duct of Rivinus, open into the floor of the mouth along the sublingual folds 75  Muscles of mastication Move mandible at TMJ All are supplied by mandibular nerve Masseter – Action – elevates mandible Temporalis – Action – elevate and retract mandible Lateral Pterygoid – Action  together – depress and protrude mandible  Alone – side to side movement Medial pterygoid – Action  together – elevates and protrude mandible  Alone - produce grinding motion 76  Neck Head and neck are anatomically complex areas of the body. Neck is transition area that joins head with trunk and limbs The posterior neck is higher than the anterior neck to connect It extends  Anteriorly from mandible to manubrium of sternum  Posteriorly from superior nuchal line to intervertebral disc between CVII and TI vertebrae.  Content Many important structures are crowded together in the neck Bones Cervical vertebrae and hyoid bone Muscles SCM, scalene, platysma, laryngeal muscles, deep muscles of the neck Vessels Subclavian vessels, common carotid artery, internal and external jugular vein, vertebral vessels, lymphatics Nerves Cervical nerve plexus, roots of brachial plexus, vagus nerve, cervical sympathetic trunk Viscera Trachea, esophagus, thyroid and parathyroid glands Bones of the neck  Bones A) Hyoid bone of neck  Is U-shaped mobile bone  Does not articulate with any other bones.  Lies at the level of C3  Is suspended in position by muscles, stylohyoid ligament and thyrohyoid membrane.  Function o provides a movable base for the tongue  Bones of the neck…. Cervical Vertebrae(7) Encloses the spinal cord and meninges. The transverse processes of all cervical vertebrae have foramina for the vertebral vessels, except C7. Typical (3rd–6th) have the following characteristics: oVertebral body is small oThe vertebral foramen is large and triangular. oTheir spinous processes are short and bifid.  B) Cervical vertebrae A) 3-6 typical vertebrae :- th  cervical vertebrae Atypical cervical vertebrae (C1, C2, and C7): C1 vertebra or atlas: o Lacks a spinous process or body o Consists of two lateral masses connected by anterior and posterior arches. C2 vertebra or axis: o Has dens (odontoid process) projects superiorly from its body.  Joints of the Vertebral Column 1. Atlanto-Occipital Joints Are a condylar synovial joint that occurs between atlas and occipital condyles. Indicate yes movement Allow flexion, extension, and lateral flexion of the head. 2. Atlantoaxial Joints  Are synovial joint of atlas and axis Allow a wide range of rotation of the atlas torial membrane  Fascia of neck Structures in the neck are surrounded by layers of fascia: a) Superficial fascia- surrounded by a layer of subcutaneous tissue b) Deep cervical fascia- o Investing o Pretracheal o Prevertebral Natural cleavage planes to separate tissue during surgery Limit the spread of abscesses/infections.  Compartments The neck has four major compartments, which are enclosed by an outer musculofascial collar 1. Vertebral compartment o Contains the cervical vertebrae and associated postural muscles; 2. Visceral compartment  Contains important glands (thyroid, parathyroid, and thymus)  Parts of respiratory & digestive tracts that pass between the head & thorax. 3. Two vascular compartments  Contain the major blood vessels and the vagus nerve Four major compartments of Neck  The Neck Region To allow clear communications regarding the location of structures, injuries, or pathologies, the neck is divided into regions. The four major regions are: (1). Sternocleidomastoid region (2). Posterior cervical region (3). Lateral cervical region (4). Anterior cervical region 91 Sternocleidomastoid region (A) Posterior cervical region (B) Lateral cervical region (posterior triangle) (C) Anterior cervical region (anterior triangle) (D)  The Anterior Contents Neck Region Common carotid artery (cc) Internal carotid artery (ic) External carotid artery (ec) Hyoid bone Thyroid & cricoid cartilage Thyroid gland 93 Muscles of Anterior Triangle of the neck Digastric Anterior Belly Mylohyoid Stylohyoid Digastric Posterior Belly  Function Muscle Innervation Suprahyoid Muscles Mylohyoid Mylohyoid Elevation of hyoid nerve from Support and elevation of floor of inferior mouth Digastric alveolar branch Raises hyoid bone Anterior of mandibular Opens mouth by lowering mandible Belly nerve [V3] Digastric Facial nerve Posterior [VII] Belly Stylohyoid Facial nerve Pulls hyoid bone upward [VII] Geniohyoid Branch from Elevates and pulls hyoid bone anterior ramus forward of C1 Fixe mandible and hyoid bone Infrahyoid Muscles Thyrohyoid Fibers from Depresses hyoid bone Platysma muscle Prevertebral muscles  Posterior to the cervical viscera  Anterolateral to the cervical vertebral column  Muscle Innervation Function Anterior Prevertebral muscles Longus Colli Branches from Flexes neck with anterior rami of rotation C2 to C6 (torsion) to opposite side if acting unilaterally Longus Branches Flex head Capitis anterior rami of C1–C3 spinal nerves Rectus Branches from Capitis anterior rami of Anterior C1, C2 Anterior Anterior rami of Flex head Scalene C4 to C7 Elevation of rib I  Muscle Innervation Function Lateral Prevertebral muscles Rectus Branches from Flexes head and helps Capitis anterior rami of C1, stabilize it Laterali C2 s Spleniu Posterior rami of Together: draw head s middle cervical back-wards Capitis spinal nerves Individually: draw and rotate head to one side Levator Dorsal scapular Elevates scapula Scapul nerve ae Middle Anterior rami of Elevation of rib I Scalen C3--C7 e Posteri Anterior rami of Flexes neck laterally;  Lateral cervical muscles Muscles Location Action Both muscles together flex Long thick the neck Sternocleidomas muscle at the An individual muscle will toid side of the draw the head to that neck shoulder. 101 Neurovasculatures of supply of head and neck  A. Subclavian artery Subclavian arteries on both sides arch upwards out of the thorax to enter the root of the neck Right subclavian artery begins posterior to the sternoclavicular joint as terminal branches of brachiocephalic trunk Left subclavian artery begins lower in the thorax than the right subclavian artery as a direct branch of the arch of the aorta. Continuing laterally across rib I, it becomes the axillary artery as it crosses its lateral border.  Parts of subclavian Isartery divided into three parts by the anterior scalene muscle: 1st part from the origin of the artery to the anterior scalene muscle 2nd part lies posterior to the anterior scalene muscle 3rd part lateral to lateral to the anterior scalene muscle All branches from the right and left subclavian arteries arise from the first part of the artery.  3 rd st 1 rt part pa B. Common carotid arteries o Have different origins on the right and left sides Right common carotid artery originates from the brachiocephalic trunk Left common carotid artery begins in the thorax as a direct branch of the arch of the aorta Ascend within the carotid sheath divide at the level of the upper border of the thyroid cartilage into the external and internal carotid arteries. Carotid sinus Dilation of the proximal part of the internal carotid artery(ICA) Contains receptors (Baroreceptors) that monitor changes in blood pressure Innervated by the CN IX through the carotid sinus nerve Carotid body Small, reddish-brown ovoid mass of receptors in the area of the bifurcation of CCA These receptors are called Chemoreceptors Monitor changes in blood chemistry, primarily oxygen content Innervated by branches from both the glossopharyngeal [IX] and vagus [X] nerves  Internal carotid artery After its origin, the internal carotid artery ascends toward the base of the skull Has no branches in the neck, ascends within the carotid sheath in company with vagus nerve and internal jugular vein, Enters the cranial cavity through the carotid canal in the temporal bone. Supply the Brain, eyes & contents of the orbits, part of nose, & the forehead Gives rise to ophthalmic artery, anterior and middle cerebral arteries.  2. External carotid artery Giving off branches immediately after the bifurcation of the common carotid arteries Supplies structures in the neck, face, scalp, tongue and maxilla. Give off :- 1. Superior thyroid artery, 2. Lingual 3. Facial 4. Ascending pharyngeal, 5. Occipital 6. Posterior auricular 7. Maxillary 8. Superficial temporal artery  External Carotid Artery: Branches 112  3. Internal jugular vein It starts as a continuation of the sigmoid sinus It exits the skull through the jugular foramen and enters the carotid sheath. Right internal jugular vein is larger than left since it receives sigmoid sinus Join with the subclavian veins posterior to the sternal end of the clavicle to form the right and left brachiocephalic veins Has tributaries like Inferior petrosal sinus, Anterior division of retromandibular & facial, lingual, pharyngeal, occipital, superior and middle thyroid veins  VEIN IN ROOT OF NECK Maxillary veins  External Jugular Vein begins near the angle of the mandible (just inferior to the auricle) by the union of the posterior division of the retromandibular vein with the posterior auricular vein It drains most of the scalp and side of the face Superior to the clavicle, the EJV receives the cervicodorsal, suprascapular, and anterior jugular veins.  Subclavian Vein Begin at the lateral margin of rib I as continuations of the axillary veins Passing medially on each side, just anterior to the anterior scalene muscles It joins the internal jugular vein to form the brachiocephalic vein The only tributary to the subclavian veins are the external jugular veins The veins accompanying the numerous arteries in this region empty into other veins It also receives the thoracic duct, and right lymphatic duct  Nerves Numerous cranial and peripheral nerves: Pass through the anterior triangle of the neck as they continue to their final destination Send branches to nearby structures The cranial nerves in these categories include  Facial [VII]  Glossopharyngeal [IX]  Vagus [X] and Recurrent laryngeal nerves  Accessory [XI]  Hypoglossal [XII] The peripheral nerves in these categories include  Cervical plexus  Phrenic nerve  Sympathetic trunk Cervical portion of the sympathetic trunks lie anterolateral to the vertebral column, extending superiorly to the level of the C1 vertebra or cranial base It is connected to each cervical spinal nerve by a gray ramus communicans Is covered by the prevertebral fascia Contains preganglionic and postganglionic sympathetic fibers 122  Gan Threeglia ganglia are usually described along the course of the sympathetic trunk in the cervical region The postganglionic sympathetic fibers are distributed in branches from these ganglia. Cervical plexus Is formed by the ventral primary rami of C1 to C4 consists of irregular series of (primary) nerve loops and branches that arise from the loops Each participating ramus, except the first, divides into ascending and descending branches The first ramus unite with the branches of the adjacent spinal nerve to form the loops Superficial branches of the plexus that initially pass posteriorly are cutaneous (sensory) branches  Branches Cutaneousof cervical plexus (Sensory) Motor branches Lesser occipital nerve Phrenic Greater auricular nerve nerve (C2, C3) Transverse cervical Ansa nerve (C2, C3) Arising cervicalis Supraclavicular from the nerve loop between the anterior rami of C2 and C3 nerve (C3, C4) Branches arising from the remaining anterior cervical nerve roots that supply Dorsal scapular nerve (C4 and C5), long thoracic nerve (C5–C7)  Ansa cervicalis Superior root of the ansa cervicalis, conveying fibers from spinal nerves C1 and C2 Inferior root of the ansa cervicalis arises from a loop between spinal nerves C2 and C3 The superior and inferior roots of the ansa cervicalis unite, forming a secondary loop, the ansa cervicalis, consisting of fibers from the C1–C3 spinal nerves Branch from the secondary loop to supply the infrahyoid muscles except thyrohyoid Lymph nodes of neck region Occipital nodes Retroauricular (mastoid) nodes: Parotid nodes Buccal(facial) nodes Submandibular nodes Submental nodes Anterior cervical nodes Posterior cervical node Jugulo-digiastric nodes Enlargement of the neck LN (cervical lymphadenopathy) is a common manifestation of disease processes occurring in the head & neck. 129 Lymphatic drainage  VISCERA OF NECK The cervical viscera are disposed in three layers, named for their primary function Superficial to deep, they are the: 1. Endocrine layer: includes thyroid and parathyroid glands. 2. Respiratory layer: includes larynx and trachea 3. Alimentary layer: includes pharynx and esophagus  Thyroid Gland Largest endocrine gland. High rate of blood flow results intense reddish coloration. “butterfly” shape due to its left and right lobes, which are connected by a narrow isthmus. Located inferior to the thyroid cartilage of the larynx and anterior to the trachea. It secrets thyroid hormone and calcitonin. 133 Thyroid Gland 134  Thyroid Gland Has two kinds of cell 1. Follicle cells: Produce thyroid hormone. Thyroxine (tetraiodothyronine or T4) Triiodothyronine or T3, 2. Parafollicular cells Produce calcitonin. Calcitonin  Secreted in response to elevated ca2+ levels.  Reduces blood calcium levels.  actively secreted during childhood.  Promotes bone formation especially in children. Osteoblasts more active and Osteoclasts are inhibited 135  T4 is the major hormone secreted by the thyroid follicles; most T3 is formed at the Actions target of by tissues Thyroid Hormones conversion of T4 I. Increase basal metabolic rate (BMR),the rate of oxygen consumption under standard conditions (awake, at rest, and fasting). II. Play an important role in the maintenance of normal body temperature. III. Together with human growth hormone and insulin, thyroid hormones accelerate body growth Except for the adult brain, spleen, testes, uterus, and the thyroid gland itself, TH affects virtually every cell in the body 136  Parathyroid Glands Small, brownish-red glands. located on the posterior surface of the thyroid gland. Two different types of cells in the parathyroid gland: chief cells oxyphil cells The function of oxyphil cells is not known. Antagonistic to calcitonin Chief cells are the source of parathyroid hormone: 137 Cont.…. 138  Parathyroid Glands Parathyroid hormone: increases Ca2+ level in blood stimulates osteoclasts and release calcium ions from bone matrix into the bloodstream. Stimulate the kidneys to promote formation of the hormone calcitriol, is active form of vitamin D. Increases the rate of calcium absorption from the gastrointestinal tract into the blood. Prevents the loss of calcium ions during the formation of urine. 139  Larynx (voice box) Is a short, somewhat cylindrical airway ends in the trachea Conducts air into the lower respiratory tract and produces sounds Prevents swallowed materials from entering the lower respiratory tract Lined by pseudostratified ciliated columnar epithelium Supported by a framework of nine pieces of cartilage that are held in place by ligaments and muscles. Glottis – the superior opening of the larynx 140 Skeletal framework Cartilages Ligaments Fibrous membranes Joints 9 cartilages 3 Unpaired cartilages Thyroid Cricoid Epiglottis 3 Paired cartilages Arytenoid Corniculate Cuneiform Cartilages of the Larynx Anterior view Posterior view 142  LARYNX The mucous membrane of the larynx forms two pairs of folds: 1. a superior pair called the ventricular folds (false vocal cords) 2. an inferior pair called the vocal folds (true vocal cords) The tension, length, and position of the vocal folds determine the quality of the sound. 143 CAVITY OF LARYNX Space between Space between 2 vestibular folds vestibular – Rima and vestibuli vocal folds – Space between 2 vocal folds – Rima Ventricle of glottidis. Larynx or Sinus of Larynx The Glottis and Surrounding Structures Glottis in the open position Glottis in the closed position 145 The Laryngeal Musculature Intrinsic muscles: Connect the cartilages to one another. Control vocal folds Open and close glottis Extrinsic muscles of the larynx connect the cartilages to other 146 structures in the throat. They move the larynx as a whole NERVE SUPPLY  Trachea A flexible tube also called windpipe Lies anterior to the esophagus and inferior to the larynx Begins below the larynx (cricoid cartilage) at the level of C6, About 10 cm long and 2.5 cm wide Partly in the neck and partly in the superior mediastinum Bifurcates at the level of T4/5 (sternal angle) 148 149  Trachea… Anterior and lateral walls of the trachea supported by 15 to 20 C-shaped tracheal cartilages Cartilage rings reinforce and provide rigidity to the tracheal wall to ensure that the trachea remains open(patent) at all times Posterior part of tube lined by trachealis muscle Inferiorly, the trachea bifurcates into two smaller tubes, called the right and left primary bronchi 150 Trachea 151 Pharynx Common space used by both the respiratory and digestive systems Commonly called the throat Common pathway for both air and food Has three parts namely:  Nasopharynx- receives the choana  Oropharynx- continuous with oral cavity  Laryngopharynx-posterior to the larynx 152  Functions of the Pharynx 1.Acts as a passageway for air and food 2.Provides a resonating chamber for speech sounds 3.Houses the tonsils which participate in immunological reactions against foreign invaders. Trap the pathogens from the food we eat and the inspired air 153  Nasopharynx Superior-most region of the pharynx Covered with pseudostratified ciliated columnar epithelium with goblet cells Located directly posterior to the nasal cavity Normally, only air passes through it Material from the oral cavity and oropharynx is typically blocked from entering the nasopharynx by the soft palate, which 154  Pharynx In the lateral walls of the nasopharynx, auditory /eustachian tube connects nasopharynx to the middle ear  Houses pharyngeal tonsil (adenoids). 155 156  Oropharynx The middle pharyngeal region. Immediately posterior to the oral cavity. Common respiratory and digestive pathway through which both air and swallowed food and drink pass. Lymphatic organs here provide the first line of defense against ingested or inhaled foreign materials. Palatine tonsils are on the lateral wall between the arches, a lingual tonsils are at the base of the tongue. 157 158 Tonsillar (Waldeyer’s) ring Laryngopharynx Inferior, narrowed region of the pharynx Extends inferiorly to the larynx and esophagus Terminates at the superior border of the esophagus and the cricoid cartilage of the larynx Permits passage of both food and air 159  Pharyngeal Muscles Composed of entirely voluntary skeletal muscles: Inner longitudinal muscles o Palatopharyngeus o Stylopharyngeus o Salpingopharyngeus External circular muscles o Superior pharyngeal constrictors o Middle pharyngeal constrictors o Inferior pharyngeal constrictors Muscles assists in deglutition (swallowing). 160 Pharyngeal muscles… 161  Esophagus Muscular food passage tube between pharynx and stomach Has about 25-30 cm long Lies posterior to the trachea. Begins at the inferior end of laryngopharynx Three part Cervical   Thoracic Pierces Abdominal the diaphragm at the level of T10 (Esophageal Hiatus) 162 Has 3 constrictions 1. Cervical constriction- At 15 cm from incisor teeth, due to cricoid cartilage 2. Thoracic constriction: At 25 cm from incisor, due to aorta and left main bronchus 3. Diaphragmatic constriction: At 40cm, due to diaphragm 163 Function of the Esophagus It secretes mucus & transports food into the stomach. It does not produce digestive enzymes, and it does not carry on absorption. Esophagus contains two sphincters: 1.Upper esophageal sphincter Skeletal muscle regulates the movement of food from the pharynx into the esophagus 2. Lower esophageal sphincter Smooth muscle regulates the movement of food from the esophagus into the stomach. 164 4 3  Introduction The eye is the organ of vision and consists of the eyeball and the optic nerve. Most dominant sense organ 70% of body receptors are located in the eye 40 % of the cortex is involved in visual processing Metabolically most active tissue The eye is the lamp of the body. Matthew 6:22  Orbit Bony cavity in anterior side of skull Lodges eye ball and associated structures Shape - four-sided pyramid with a base, apex and four walls Seven bones contribute to the framework of each orbit. These bones are the maxilla, zygomatic, frontal, ethmoid, lacrimal, sphenoid, and palatine bones 166 Accessory Structures of the Eye Eyelids Structures of the eye lid from out side to inside Skin Subcutaneous tissue –contain orbicularis occuli Palpebral fascia – forms  Orbital septum  Tarsal plate  Palpebral ligaments - lateral and medial palpebral ligaments 2 Muscle : orbicularis oculi & levator palpebrae superioris Conjunctiva – lines the eye lid  Conjunctiva…Cont’d The conjunctiva is a thin vascular transparent mucous membrane. It is subdivided into:- Palpebral Conjunctiva Bulbar conjunctiva It lines the eyelids as the palpebral conjunctiva and reflects (folds back) over the anterior surface of the eyeball as the bulbar conjunctiva onjunctiva….. The major function of the conjunctiva is to produce a lubricating mucus that prevents the eyes from drying out. The bulbar conjunctiva covers only the white of the eye, not the cornea  Plica semilunaris It is a pinkish crescentric fold of conjunctiva, present in the medial canthus Permit greater rotation of globe Caruncle The caruncle is a small, ovoid, pinkish mass, situated in the inner canthus, just medial to the plica semilunaris. Plica semilunaris Caruncle 173 The Lacrimal Apparatus Is a group of structures that produces and Lacrimal drains lacrimal fluid or tears. Gland Lacrimal duct Puncta Canaliculi (super & inferior) Lacrimal Sac Nasolacrimal Duct  Lacrimal Gland 0 almond shaped and approximately 2 cm long 0 lies in the fossa for the lacrimal gland in the supero- lateral part of each orbit  Muscles of orbit Extraocular muscles: 4 recti and 2 oblique muscles 177 Eyeball Contains the optical apparatus of the visual system It occupies most of the anterior portion o the orbit, suspended by six extrinsic muscles Spherical in shape with anterior and posterior poles with a diameter of about 2.5 cm The wall is composed of three concentric coats (tunics) –  Outer coat (fibrous): Cornea and sclera 179  Fibrous Tunic (Sclera and Cornea) External fibrous skeleton of the eyeball Provides shape and resistance Sclera – Tough opaque part of the fibrous layer of eyeball – Dense fibrous tissue consisting almost entirely of collagen. – Covering the posterior 5/6th of the eyeball – protects the eye and anchors extrinsic muscles – Anterior part of the sclera is visible through the transparent bulbar conjunctiva as “the white of the eye” – Continues anteriorly with cornea at sclerocorneal 181 182  Cornea Clear, transparent and avascular tissue which overlies the colored iris & pupil It is the eye’s optical window that makes it possible for humans to see. Made up of special More convex than sclera and forms anterior connective tissue 1/6th of eyeball It is thinnest centrally and thicker peripherally  B. Vascular Tunic (Uvea or Uveal 1. Choroid region tract) –A dark brown membrane that forms the posterior portion of the uvea –largest part of the vascular layer of the eyeball –Pigmented and dense vascular bed –Lines (underline) most of the sclera –Contain venous plexus and capillaries –Supplies blood to all eye tunics –Anteriorly ends at ora serrata by merging with ciliary body –Posteriorly pierced by optic nerve –Attached to sclera loosely and retina firmly184  CILIARY BODY Ring-like thickening of the layer posterior to the corneoscleral junction Muscular as well as vascular Connects the choroid with the circumference of the iris. Provides attachment for the suspensory ligament of lens. The contraction and relaxation of the circularly arranged smooth muscle of the ciliary body controls the thickness of lens, and therefore the focus of the lens. Ciliary muscle Ciliary processes  Ciliary process are folds on the internal surface of the ciliary body, secrete aqueous humor. CILIARY BODY IRI S  Iris The colored anterior part of the eye Posses pigment cells; determine eye color Form circular curtain with opening at the center called pupil Regulates the amount of light entering the eye by 2 muscles – Sphincter pupillae (ring muscle) – Dilator pupillae (radial muscle) Close vision and bright light – pupils constrict parasympathetic stimulation TheDistant vision and dim light – pupils dilate quantity of melanin pigment in the iris is one factor in determining the phenotypic eye Sympathetic color of a person. stimulation 188  C. Sensory Tunic: Retina A delicate membrane between choroids and vitreous body It is a thin semi-transparent, multilayered sheet of neural tissue lines the inner aspect of the posterior 2/3 of the wall of the globe. Consists of two functional parts with distinct locations:  Optic part  Non-visual retina 189 Retina RETINA  Retina… The optic part of the retina is sensitive to visual light rays and has 2 layers:  Neural layer  Pigmented layer The neural layer is light receptive The pigmented layer consists of a single layer of cells  reinforces the light absorbing property of the choroid in reducing the scattering of light in the eyeball. Non-visual retina : Anterior continuation of the pigmented layer and a Layer of supporting cells. Extends over the ciliary body (ciliary part of retina) and the posterior surface of the iris (iridial part of retina)  Retina (macula and fovea) Macula: Just lateral to the optic disc The macula is a small oval area of the retina with special photo-receptor cones that is specialized for acuity of vision. Fovea (foveola): is the central part of the macula (about 0.33mm in diameter), and contains only cones It forms a depression in the macula Area of most acute vision.  Blood Supply to the Retina Theneural retina receives its blood supply from two sources – The outer third receives its blood from the choroids (cones and rods of the neural layer) – The inner two-thirds are served by the central artery and vein (enter eye with optic nerve) – Small vessels radiate out from the 193  Inner Chambers and Fluids The lens separates the internal eye into anterior and posterior segments Anterior Segment Composed of two chambers Anterior – between the cornea and the iris Posterior – between the iris and the lens Posterior segment – Filled with a clear gel called vitreous humor (body) 194  Lens The Lens is a is a transparent, biconvex and flexible encapsulated elastic disc situated between the posterior surface of the iris and the vitreous body. Allows precise focusing of light onto the retina The lens is unique in that it doesn’t have any innervation or vascularization.  Vitreous Body Vitreous is clear, avascular, gelatinous body that comprises 2/3 of the volume and weight of the eye. Transparent jelly-like substance Vitreous is about 99% water. The remaining 1% includes collagen & hyaluronic acid, (which give vitreous gel-like form & consistency because of their ability to bind large volume of water) Has a nutritive and supportive role functions  Transmits light  Maintain the spherical shape of the eyeball  Supports the posterior surface of the lens  Holds the neural retina firmly against the pigmented layer  Contributes to intraocular pressure VITREOUS BODY  Arterial Supply of the Orbit The arterial supply to the structures in the orbit, including the eyeball, is by the ophthalmic artery which is a branch of the internal carotid artery. Venous Drainage of the Orbit  Innervation of the Orbit Numerous nerves pass into the orbit and innervate structures within its bony walls. They include the  Optic nerve [II]  Oculomotor nerve [III]  Trochlear nerve [IV]  Abducent nerve [VI]  Autonomic nerves Other nerves such as the ophthalmic nerve [V1] innervate orbital structures and then travel out of the orbit to innervate other regions.  Neuroanatomy Nervous system is the chief controlling and coordinating system of the body Most complex system of the body Enables the body to react to continuous changes in its internal and external environments. Is formed by a network of many billion nerve cells (neurons), and supporting glial cells. Nerve tissue is distributed throughout the body as an integrated communications network.  Functions of Nervous System Sensory input: Receive both internal and external stimuli Integration: Analyzing and storing some of it Making decisions for appropriate responses and perception Conscious awareness of sensory stimuli. Motor output: Causes muscles to contract and glands to secrete.  Anatomical classification of Nervous system Central nervous system:  Brain  Spinal cord CNS is responsible integrating & coordinating sensory information and ordering appropriate motor actions. CNS is a site of learning, memory, intelligence and emotion Peripheral nervous system: Nerve outside the brain and spinal cord  12 Cranial nerves  31 Spinal nerves PNS provide afferent fiber impulse to CNS & carries efferent impulse to muscles, gland s and blood vessels  Functional classification of nervous system  PNS Somatic nervous system Coordinating & voluntary control of body movements through action of skeletal muscles, in response to external stimuli (e.g., touch, hearing & sight) Regulates activities that are under conscious control Autonomic nervous system (ANS) (or visceral nervous system) Acts as a control system, maintaining homeostasis in the body Most of its actions are involuntary, without conscious control Autonomic · Functioning Sympathetic – “fight-or-flight” · Response to unusual stimulus · Takes over to increase activities · Remember as the “E” division = exercise, · Parasympathetic – housekeeping activities · Conserves energy · Maintains daily necessary body functions Autonomic Nervous System (ANS) has two primary divisions: Sympathetic – thoraco-lumbar originate from thoracic & lumbar spinal cord segment Parasympathetic- cranio-sacral they arise from cranium and sacral spinal cord segment  Cells of nervous system Nervous tissue consists of two main cell types:  Neurons (nerve cells)  Neuroglia (glial cells), which support the neurons Neurons are the structural & functional units of nervous system. Neurons  Are excitable cell  Specialized for reception and conduction impulse  Have a high metabolic rate  Unable to survive long without oxygen & glucose  Have an extremely long lasting lifetime.  Neurons do not divide (Amitotic)  Neuron Anatomy · Cell body-- nucleus with a prominent nucleolus and the bulk of the cytoplasm · Dendrites – conduct impulses toward the cell body · Myelin Axons – sheath: Protective covering for axon  Functional Classification · Sensory (afferent)of neurons · Carry impulses from the sensory Neurons receptors to the CNS E.g. from cutaneous sense organs · Motor (efferent) neurons · Carry impulses from the CNS to viscera, muscles, or glands · Interneurons (association neurons) · Found in neural pathways in the Neuron Classification  Structural Classification of · Multipolar Neurons neurons – many extensions from Most common type theofcell body neuron Motor neurons and interneurons Bipolar neurons ·Neurons in special sense – one axon and one dendrite · Unipolar e.g. sensory neuron  Syna pse Neurons communicate with each other at synapses, points of contact between neurons. The communication occurs by means of neurotransmitters, NT: chemical agents released or secreted by one neuron, which may excite or inhibit another neuron  Terminology associated with Nervous system The CNS composed of gray matter and white matter Gray matter consists of nerve cells (cell body) embedded in neuroglia; it has a gray color. White matter consists of nerve fibers embedded in neuroglia; has a white color Cluster of cell bodies within the CNS is called nuclei Cluster of cell bodies within the CNS is called ganglia. A bundle of axonal fibers within the CNS is a tract. A bundle of axonal fibers outside the CNS is called “Nerve” Connective tissue covering of nerve 1. Endoneurium  A membrane covering each nerve fiber 2. Perineurium  Encloses a fascicle (bundle) of nerve fibers 3. Epineurium  Forming the outermost covering of the nerve  Neuroglia (glial cells or glia) Five times as abundant Non-excitable cells Supporting, insulating, and nourishing the neurons can multiply and divide throughout life Neuroglia in CNS Oligodendrocyte Form myelin layers around axons in the CNS Microglia Phagocytotic cells of nervous system Astrocytes Formation of blood brain barrier Help to regulate the passage of molecules from the blood to the brain Ependymal cells Line the ventricles of the brain and the central canal of the spinal cord  Neuroglia in PNS Schwann cells Form myelin layers around axons in the PNS Satellite cells Support neuron cell bodies within the ganglia of the PNS  Protection of the Central Nervous System  Scalp and skin  Skull and vertebral column  Meninges  Cerebrospinal fluid (CSF)  Blood-brain barrier (BBB)  Meninges The brain, as well as the spinal cord, is surrounded by three layers of membranes called the meninges. Dura mater-tough outer layer · Double-layered external covering · Outer Periosteal layer – attached to surface of the skull · Inner Meningeal layer – outer covering of the brain Arachnoid layer- Middle layer a thin, avascular membrane · Web-like Pia mater- Internal layer · Clings to the surface of the brain  Meninges The dural infoldings divide the cranial cavity into compartments, forming partial partitions (dural septa) between certain parts of the brain and providing support for other parts. The dural infoldings include the: 1. Falx cerebri (cerebral falx)- the largest dural infolding,lies in the, longitudinal cerebral fissure, separates the right and the left cerebral hemispheres. 2. Tentorium cerebelli (cerebellar tentorium)- separates the occipital lobes of the cerebral hemispheres from the cerebellum. 3. Falx cerebelli (cerebellar falx)-separates the right and left cerebellar hemispheres 4. Diaphragma sellae (sellar diaphragm)-covers the hypophysial 11/19/2024 05:00 PM fossa of the sphenoid By Asfaw B. bone. 222 Meninges… 11/19/2024 05:00 PM By Asfaw B. 223  Cerebrospinal Fluid Clear, colorless liquid that circulates in the subarachnoid space. The space between the Pia mater and the arachnoid mater Functions of CSF Mechanical protection (forms a watery cushion) Nutrition Circulation (a pathway for excretion from the CNS) Formation of CSF in the Ventricles Produced from the wall of ventricle Ventricles are four CSF-filled cavities within the brain. The CSF is produced from the choroid plexuses. 224  Ventricles of the brain The irregular shaped cavities filled with cerebrospinal fluid present within the brain are called as ventricles They are: Right and left lateral ventricles : Lie within the cerebral hemispheres Third ventricle: Lie within the diencephalon Fourth ventricle: Lie within the brain stem  Choroid Plexus Choroid plexus hang from the roof of each ventricle The plexuses are clusters of thin walled capillaries enclosed by a layer of ependymal cells The capillaries of the choroid plexus are fairly permeable and fluid filters continuously from the bloodstream into the ventricles he Flow Of CSF  Blood–brain barrier (BBB) Consists mainly of Tight junctions of endothelial cells of capillaries Thick basement membrane surrounding capillaries. Pedicles of astrocytes Substance allowed to pass allowed through the BBB Lipid soluble substances, such as  oxygen, Co2, alcohol, & anesthetic agents, are able to access brain tissue freely. Water-soluble substances, glucose, cross BBB by active transport. Other substances,  Creatinine, urea, and most ions, cross BBB very slowly. Proteins and most antibiotic drugs—do not pass at all  CNS :Spinal Cord (45 cm long) Begins as a continuation of the medulla oblongata and extends through foramen magnum to L1 vertebra and Located within the vertebral canal of the vertebral column Is protected by the  Vertebral column and denticulate ligaments.  Meninges  Cerebrospinal fluid (CSF) Functions of spinal cord:  Sensory & motor innervation of the entire body inferior to the head  2 way conduction pathway b/n the body & the brain  Major center for reflexes  Spinal Cord Regions are Cervical Thoracic Lumbar Sacral Coccygeal Gives rise to 31 pairs of spinal nerves All are mixed nerves  Terminal part of spinal cord Terminates in a tapering cone shaped structure called the conus medullaris Filament of connective tissue, the filum terminale, attaches conus medullaris to the coccyx inferiorly Lower spinal nerve angle sharply downward and form a collection of nerve roots called cauda equina  External features Two enlargements Cervical enlargement – upper limb Lumbar enlargement – lower limb 31 pairs of spinal nerves that arise from the spinal cord by paired roots Anterior root – motor exit Posterior root – sensory entry And they unite outside the spinal cord and become mixed nerve Exit from through the intervertebral foramina Consists of an outer region of white matter and an inner region of gray matter  Gray Matter of 1.the Dorsal/ spinal posterior horncord Receives and processes sensory input Is found at all levels. 2. Ventral/anterior horn Contains motor nuclei. Gives motor output is found at all levels. 3. Lateral horn Contain cell bodies of autonomic motor nuclei Receives viscerosensory input. Is between dorsal and ventral horns. Only found in thoracic & lumbar  White Matter of the spinal Cord Three types of fibers 1. Ascending Carry sensory information from the sensory neurons of the body to the brain Mostly decussate before reaching their final destination 2. Descending Carry motor instructions from the brain to the spinal cord to muscles and glands Mostly decussate before reaching their final destination in the medulla oblongata 3. Commissural – Cross from one side of the cord to the other The ascending & descending tracts make up most of the white matter of the spinal cord The peripheral nervous system Nerves conveying impulses to and from brain or spinal cord. Spinal nerves connect the CNS to sensory receptors, muscles, and glands in all parts of the body 31 pairs of spinal nerves 8 cervical ( C1-C8) 12 thoracic ( T1-T12) 5 lumbar (L1-L5) 5 sacral (S1-S5) 1 coccygeal (C0) Spinal nerves emerge through the IV foramina  Nerve Plexus A network of nerve formed by multiple nerve communication Cervical plexus : supply the structures in the neck Brachial plexus : supply the upper limb Lumbar plexus : supply the lower limb Sacral plexus : supply the lower limb and pelvis 237  Cranial nerves There are 12 pairs of cranial nerves The cranial nerves are designated by roman numerals All the nerves are distributed in the head and neck, except CN X, All cranial nerves originate from the brain except CN-XI Categorized as: Purely sensory CN I, II, and VIII Purely motor nerves: CN III, IV, VI, XI, and XII Mixed nerves: CN V, VII, IX, and X both sensory and motor neurons.  Cranial nerves division based on their origin Cranial nerves I & II from cerebrum Cranial nerves III & IV originate from the midbrain; Cranial nerves V, VI, VII & VIII from Pons Cranial nerves IX, X, XI, & XII arise from medulla oblongata. Function of cranial nerve CN I: OLFACTORY Function: Smell carry impulse from olfactory receptors of nasal cavity to cerebrum CN II: OPTIC Function: Vision Carry impulse from retina of eyeball to thalamus then cerebrum Form the optic chiasm  B. Optic Nerve (CN II): Is derived from the ganglion cells of the retina & enters the skull via the optic canal of the sphenoid bone. Is a special somatic afferent (SSA) Regulate vision and pupillary light reflexes Its unique features: It consists of second-order sensory neurons. Entirely enclosed in meningeal sheaths and subarachnoid space Is not a true peripheral nerve since its fiber has no neurilemmal sheath but it is a tract of the diencephalon 241  Optic….. The fibers of the optic nerve are the axons of the cells in the ganglionic layer of the retina. They converge on the optic disc and exit from the eye, as the optic nerve. 242  Optic Nerve(CN II) – Begin at the lamina cribrosa of the sclera  Unmyelinated nerve fibers before piercing  Myelinated, after piercing the sclera 243 243  CN-II: Optic Nerve Optic chiasma The optic nerve leaves the orbital cavity and unites with the optic nerve of the opposite side to form the optic chiasma. Situated at anterior wall & floor of 3rd ventricle Fibers from nasal half of each retina cross & enter optic tract of opposite side. Optic Tract: The optic tract passes posterolaterally around the cerebral peduncle.  Most fibers of optic tract terminate in lateral geniculate body  Optic radiation  IC  visual cortex (B-17)  Few terminate of optic tract terminate in pretectal 244 nucleus & superior colliculus 245  Lateral Geniculate Body The lateral geniculate body is a small, oval swelling projecting from the thalamus. It synapse the axons of the optic tract. The axons of the nerve cells within the geniculate body leave it to form the optic radiation. 246 Optic Radiation The fibers of the optic radiation are the axons of the nerve cells of the lateral geniculate body. OR passes posteriorly through the retrolenticular part of the IC and terminates in the visual cortex (area 17). The visual association cortex (areas 18 and 19) is responsible for recognition of objects and perception of color. 247  Clinical Function:correlation vision Clinical test for damage: tests peripheral vision and visual acuity Effects of damage: blindness in part or all of the visual field Papilledema: swelling of optic disc (Early sign of 248 increased ICP)  Cranial Nerves controlling Muscles of The eyeball CNIII: OCULOMOTOR o Innervates 4 of the 6 extrinsic eye muscles o Control over intrinsic muscle of the eyeball Function: eye movements, constriction and focusing CNIV: TROCHLEAR: the smallest It innervates the superior oblique muscle of the eyeball Function: eye movements CN VI: ABDUCENS It enervates lateral rectus muscle of the eyeball Function: Eye movements Trigeminal (V) Nerve It is a mixed cranial nerve the largest. It has three branches: a)Ophthalmic: ItsSensory only sensory nerve carry impulses for touch, pain, and thermal b)Maxillary: sensations. ItsSensory motor neuronsonly from the mandibular nerve and supply muscles of mastication. c)Mandibular: Facial (VII) Nerve It gives motor innervation for muscles of fascial expression Its sensory input from anterior 2/3rd of tongue Vestibulochochlear (VIII) Nerve The vestibular branch carries impulses for equilibrium The cochlear branch carries impulses for hearing. Glossopharyngeal (IX) Nerve Innervates the muscle involving in swallowing Stimulate the parotid gland to secrete saliva. Taste buds on the posterior 1/3rd of the tongue Vagus (X) Nerve Its motor neurons supply muscles of the pharynx, larynx, and soft palate that are used in swallowing, vocalization, and coughing. Its both motor and sensory axons supply most organs of the thoracic and abdominal cavities. Accessory (XI) Nerve It conveys motor impulses to the SCM and trapezius muscles to coordinate head movements. CN XII: HYPOGLOSSAL It supplies the muscles of the tongue conducting nerve impulses for speech and swallowing.  The Brain Wrinkled surface Cerebral hemisphere Weighs about 1600 g & female’s about 1450 g Found in the cranial cavity protected with Skull Three layers of meninges Brain CSF stem Cerebellum Inferiorly continuous with the spinal cord at the foramen magnum Principal Parts of Brain The brain is composed of the Cerebrum Diencephalon Thalamus Epithalamus Hypothalamus Cerebellum Brainstem Mid-brain Pons Medulla oblongata 257  Cerebrum (“seat of intelligence”) The largest and most conspicuous portion of the brain. located in the region of the telencephalon It accounts for about 80% is responsible for the higher mental functions including memory, planning, and reason. Consists of Right hemispheres separated by a deep groove called the Left hemispheres median longitudinal fissure  Cerebrum It is the “seat of intelligence.” The folds are called gyri. The deepest grooves between folds are known as fissures. The shallower grooves between folds are termed sulci. 260  The cerebral Hemisphere are connected internally by the corpus callosum Corpus callosum: a broad band of white matter. – Contain axons that extend between the hemispheres.  Functions of the Cerebral Cortex Conscious awareness and thought Reasoning & intellect Emotions Behavior & memory (stores information and retrieves when needed). Receives all sensory modalities (mostly through thalamus) The highest level to controls & directs the 262  Cerebrum The left hemisphere is more important for  language, numerical and scientific skills, and reasoning. The right hemisphere is more important for  Musical and artistic awareness,  Spatial and pattern perception,  Recognition of faces,  Emotional content of language,  Identifying odors, and  Generating mental images of sight, sound, touch, taste, & smell. Lobes of cerebrum Each hemisphere is subdivided into 5 lobes by deep sulci called fissures; Some of the deeper sulci divide each cerebral hemisphere into five major lobes: the Frontal lobe Parietal lobe Occipital lobe Temporal lobe Insula The central sulcus (fissure of Rolando) b/n the frontal lobe and the parietal lobe. The lateral sulcus (fissure of Sylvius) b/n the frontal and temporal lobes. Summarized of the cerebral lobes memory, emotions,. reasoning, 266 Internal structure of the cerebral Composed of hemispheres Outer cover of gray matter, cerebral cortex Internally white matter Collection of gray matter in a white matter called nuclei  Cerebral Cortex Functional organization of the cerebral cortex Three kinds of functional areas: 1. Motor areas Are primarily concerned with the motor functions and Give origin to the projection fibers 2. Sensory areas Receive afferent fibers Are primarily concerned with the sensory functions, Provide conscious awareness of sensation and 3. Association areas – integrate diverse information, communicate “associate” with the motor cortex and sensory association areas to analyze input 268  Some important sensory areas Primary somatosensory area (areas 1, 2, and 3): Receives nerve impulses for touch, proprioception, pain, and thermal sensations. Primary visual area (area 17), Receives visual information and is involved in visual perception sensory areas…. Primary auditory area(areas 41 and 42), Receives information from auditory receptors Is involved in auditory perception Primary gustatory area(area 43), Receives impulses for taste Is involved in gustatory perception. Motor Areas Primary motor area(area 4): controls voluntary contractions of specific or groups of muscles Broca’s speech (areas 44 and 45) Concerned with planning and production of speech. Association Areas Somatosensory association area(areas 5 and 7): Permit us to determine the exact shape and texture of an object.  Prefrontal cortex (frontal association area) (areas 9, 10, 11, and 12) Concerned with: Person’s personality, intellect, complex learning Abilities, recall of information, initiative, judgment, foresight, reasoning, mood, planning for the future, and development of abstract ideas. The numbers, still used today, are from K. Brodmann’s map of the cerebral  Cerebral White Matter Different areas of the cerebral cortex communicate: With each other With the brainstem and spinal cord Types of tracts Commissural fibers Allows communication between cerebral hemispheres Corpus callosum – the largest commissure Association fibers Connect different parts of the same hemisphere E.g. cingulum Projection fibers – run vertically Descend from the cerebral cortex Ascend to the cortex from lower regions E.g. Internal capsule 274  cle The basal ganglia are several groups of nuclei in each cerebral i hemisphere Functions of the Basal Ganglia Concerned with planning, organizing and coordinating voluntary movements. Determine how rapidly a movement is to be performed and how large the movement must be. Inhibit or decrease unwanted muscular activity. Regulate the muscle tone, Control automatic associated movement 275  Dienceph It forms a central core of brain tissue just superior to the midbrain. alon Extends from the brain stem to the cerebrum surrounds the third ventricle Includes: Thalamus, Hypothalamus Epithalamus  Thalamus A large, ovoid, grey matter on each half of brain Situated on each side of third ventricle. Provides crude perception of touch, pressure, pain, & temperature. Act as a relay center for all sensory impulses except olfaction 277 b) Epithalamus-a small region superior and posterior to the thalamus, consists of Pineal gland secretes the hormone melatonin- promote sleepiness. Habenular nuclei- emotional responses to odors 278  Hypothal amus Is a part of diencephalon which lies below the thalamus. Links nervous system to endocrine system via pituitary gland Contain multiple nuclei which controls different body activities The hypothalamus regulate o Hormone secretion o Controls and integrates activities of ANS o Thermoregulation (thermostat) o Food & water intake (hunger & satiety) o Sleep & circadian rhythms o emotional behavior: anger, aggression, fear, pleasure, sex drive, orgasm o Memory 279  Brain · Connects Stemcord spinal with forebrain · It is stalk like in shape · Occupies the posterior cranial fossa of the skull · Parts of the brain stem Made of outer white matter & an inner gray matter However, Midbrainthere are also nuclei of gray matter located  Midbrain This short segment of the brainstem The cerebral aqueduct passes through the midbrain It contains both tracts and nuclei. The anterior part of the midbrain contains a pair of tracts called cerebral peduncles The posterior part of the midbrain, called the tectum 281 Tectum contains four rounded elevations Two superior elevations are known as the superior colliculi reflex centers for certain visual activities The two inferior elevations, the inferior colliculi reflex center for auditory pathway  The Pons Lies directly superior to the medulla and anterior to the cerebellum Bridging the left & right cerebellar hemispheres These connections are provided by bundles of axons. 283  The Pons It consists of both nuclei and tracts. Vestibular nuclei, which are present in the pons and medulla, are part of the equilibrium pathway to the brain. Nuclei associated with cranial nerves V–VIII. Connected to the cerebellum by the middle cerebellar peduncle.  Medulla Oblongata It forms the inferior part of the brain stem. Connected to the cerebellum by the inferior cerebellar peduncle. Nuclei of cranial nerves VIII–XII located here 285  Pyramids of the medulla is formed by the largest motor tracts that pass from the cerebrum to the spinal cord. 90% of the axons in the left pyramid cross to the right side. This crossing is called the decussation of pyramids This why one side of the brain controls movements on the opposite side of the body.  Medulla Oblongata Relays information It Contains:  Cardiac & Respiratory Centers  A portion of the fourth ventricle Regulates several basic autonomic functions – Heartbeat (rate and force) – Blood pressure (vasoconstriction/dilation of arteries) – Breathing (rate and depth) – Others: speech, coughing, sneezing, salivation, swallowing, vomiting, sweating  CEREBELLUM 2nd largest part of the brain Situated in the posterior cranial fossa Two cerebellar hemispheres joined by a narrow median called vermis Form the roof of fourth ventricle The external surface of cerebellum display a large number of narrow ridge-like folds called folia Connects to the brain stem by the superior, middle, and inferior cerebellar peduncles, thick fiber tracts that carry information to and from the cerebellum.  Lobs Primary fissure Anterior lobe Two deep fissures Posterior lobe Primary fissure Posterolateral fissure Three lobes Flocculonodular lobe Anterior lobe Corpus of cerebellar Flocculonodular lobe Posterior lobePosterolateral fissure  Internal structures Composed of an outer covering of gray matter called cerebellar cortex and inner white matter. Embedded in the white matter of each hemisphere are three masses of gray matter forming the intracerebellar nuclei Gray matter Fastigial nucleus Cerebellar cortex Cerebellar cortex Globose nucleus Emboliform Cerebellar nuclei Dentate nucleus Dentate nucleus Fastigial nucleus Emboliform nucleus Globose nucleus White matter － medullary center (Arbor Vitae)  Three functional divisions 1. Vestibulocerebellum 2. Spinocerebellum Archicerebellum Paleocerebellum Flocculonodular lobe Vermis and intermediate zone  Maintains the body posture and balance. Regulate muscle tone.  Coordinate head and eye movements Intermediate zone Vermis Lateral zone 3. Cerebrocerebellum Neocerebellum Largest lobe of the cerebellum. Flocculonodular lobe Coordinate the voluntary motor activity Receives massive input from cerebral cortex. Decide plan ,range, rate, force, strategies , direction, and feed back of movements  Functions of Cerebellum Is a great reservoir for proprioceptive information A coordinator of motor activity conscious and subconscious movements Maintain balance and equilibrium Participates in motor planning Integration of sensory perception 293  Blood Supply of The Brain The brain receives it arterial supply from two pairs of vessels, The vertebral and internal carotid arteries which are interconnected in the cranial cavity to produce an arterial circle of Willis