Brain, Cranial Nerve And Supply

HEAD AND NECK

General structure of NS (1)

• The nervous system has two divisions.

The central nervous system (CNS) consists of the brain and spinal cord.

The peripheral nervous system (PNS) consists of cranial nerves and spinal nerves. The PNS includes the autonomic nervous system (ANS).

The brain is contained within the cranial cavity of the skull, and the spinal cord is contained within the vertebral cavity of the vertebral column.

General structure of NS

Nervous tissue, present in both the CNS and PNS, contains two basic types of cells: neurons and glial cells.

Neurons are cells and therefore have a cell body, axon and the dendrite.

Looking at nervous tissue, there are regions that predominantly contain cell bodies and regions that are largely composed of just axons. These two regions within nervous system structures are often referred to as gray matter (the regions with many cell bodies and dendrites) or white matter (the regions with many axons).

Brain, Cranial Nerve And Supply

A localized collection of neuron cell bodies in the CNS is referred to as a nucleus. In the PNS, a cluster of neuron cell bodies is referred to as a ganglion.

A bundle of axons, or fibers, found in the CNS is called a tract whereas the same thing in the PNS would be called a nerve.

In the peripheral nervous system, axons and dendrites are “wrapped” in specialized cells called Schwann cells

General structure of NS (4)

Neurons may be classified into three groups: sensory neurons, motor neurons, and interneurons.

Sensory neurons (or afferent neurons) carry impulses from receptors to the central nervous system.

Interneurons are found entirely within the central nervous system. They are arranged so as to carry only sensory or motor impulses, or to integrate these functions.

Motor neurons (or efferent neurons) carry impulses from the central nervous system to effectors

General structure of NS (5)

• Glial cells
• oA supportive cell in the central nervous system.
• oUnlike neurons, glial cells do not conduct electrical impulses.

oThe glial cells surround neurons and provide support for and insulation between them.

oGlial cells are the most abundant cell types in the central nervous system. Types of glial cells include oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells.

Neuroglia in the CNS include astrocytes, microglial cells, ependymal cells and oligodendrocytes.

Neuroglia in the PNS include Schwann cells and satellite cells.

Astrocytes support and brace the neurons and anchor them to their nutrient supply lines. They also play an important role in making exchanges between capillaries and neurons.

General structure of NS (6)

Ependymal cells are another glial subtype that line the ventricles of the CNS to help circulate the CSF.

Oligodendrocytes are cells that wrap their process tightly around the fibers producing an insulating covering called myelin sheath.

• Schwann cells are similar in function to oligodendrocytes and microglial cells.
• Satellite cells perform a similar function to astrocytes

General structure of NS (7)

The Brain:

The brain constitutes about 2% of the body weight and lies within the cranial cavity, the parts are:

• Cerebrum
• Cerebellum
• Brain stem
• Midbrain
• Pons

Medulla oblongata

The largest part of the human brain is the cerebrum, which consists of two hemispheres separated by the longitudinal fissure.

At the base of this deep groove is the corpus callosum, a band of 200 million neurons that connects the right and left hemispheres.

• Within each hemisphere is a lateral ventricle.

The surface of the cerebrum is gray matter called the cerebral cortex.

In the human brain the cerebral cortex is folded extensively. The folds are called convolutions or gyri and the grooves between them are fissures or sulci

The Brain: Cerebrum

The cerebral cortex is divided into lobes that have the same names as the cranial bones external to them

• The cerebral cortex is divided into four sections, called lobes.
• Frontal lobe
• Parietal lobe
• Occipital lobe
• Temporal lobe

The Brain: Cerebrum (cont..)

The Precentral (Motor) Area

This lies in the frontal lobe immediately anterior to the central sulcus.

The cell bodies are pyramidal shaped (Betz’s cells) and they initiate the contraction of skeletal muscles.

• Pre-motor Area

This lies in the frontal lobe immediately anterior to the motor area.

The cells are thought to exert a controlling influence over the motor area, ensuring an orderly series of movements.

Broca’s Area

In the lowest part of premotor area just above the lateral sulcus there is a group of nerve cells known as the motor speech (Broca's) area which controls the movements necessary for speech.

The Brain: Cerebrum (Specialized areas)

The Brain: Cerebrum (Specialized areas) cont..

The Frontal Area

• This extends anteriorly from the premotor area to include
• the remainder of the frontal lobe.
• It is associated with reasoning, planning, emotions, behavior and problem solving.
• Sensory Areas of the Cerebrum

Post central (sensory) area: this is the area behind the central sulcus.

Here sensations for pain, temperature, pressure and touch, knowledge of muscular movement and position of joints are perceived.

The Parietal Area

This lies behind the post central and includes the greater part of the parietal lobe of the cerebrum.

Its function is associated with obtaining and retaining accurate knowledge of objects.

The object can be recognized by touch alone because of the knowledge from the past experience (memory) retained in this area.

Sensory Speech Area (Wernike’s)

This is situated in the lower part of the parietal lobe and extends into the temporal lobes. Spoken words are perceived here The Brain: Cerebrum (Specialized areas) cont..

Auditory Area

This receives and interprets impulses transmitted from the inner ear by the cochlear, auditory part of the 8th cranial nerve

Olfactory (Smell) Area

This lies deep within the temporal lobe where impulses from the nose via the olfactory nerves (1st cranial nerves) are received and interpreted.

Taste Area

• This is the area where impulses from special nerve endings
• in the taste buds in the tongue are perceived as a taste.

The Brain: Cerebrum (Specialized areas) cont..

Visual Area

oThis lies behind the parietal-occipital sulcus and includes the greater part of the occipital lobe.

oThe optic nerves pass from the eye to this area which receives and interprets as visual impressions.

The Brain: Cerebrum (Specialized areas) cont..

29

The Brain: Thalamus

Two masses below the corpus callosum.

Sensory input from the skin, viscera and special sense organs is transmitted to the thalamus before redistribution to the cerebrum.

The main function of the thalamus is to relay motor and sensory signals to the cerebral cortex.

Also called Basal ganglia

It has connections to the cerebral cortex and thalamus.

It forms part of the extapyramidal tracts and are thought to be involved in initiating muscle tone in slow and coordinated activities.

• This area of the brain is responsible for body movement and coordination.
• If control is inadequate or absent, movement are jerky, clumsy and uncoordinated.

The Brain: Basal Nuclei

The Brain: Hypothalamus

It is composed a number of groups of nerve cells.

It is linked to the posterior lobe of the pituitary gland by nerve fibres and to the anterior lobe by a complex system of blood vessels.

Through these connections, the hypothalamus controls the output of hormones from both lobes of the gland.

Function: Releasing hormones, regulating body temperature, maintaining daily physiological cycles, controlling appetite

The Brain: Cerebellum

• It occupies posterior cranial fossa.
• It has two hemispheres separated by a narrow strip called vermix.

It is concerned with the coordination of voluntary movement, posture and balance.

Impulses from the cerebellum influence the contraction of skeletal muscle so that balance and posture are maintained.

37

The Brain: Brainstem

The Brainstem

• This is formed by midbrain, pons and medulla oblongata

Midbrain

This consists of groups of cell bodies and nerve fibres (tracts) which connect the cerebrum with the lower parts of the brain and with the spinal cord.

The cell bodies act as relay stations for the ascending and descending nerve fibres.

Pons

It consists mainly of nerve fibres which form a bridge between the two cerebella hemispheres and fibres passing between the higher levels of the brain and spinal cord.

There are groups of cells within the pons which act as relay stations and some of these are associated with cranial nerves.

It is involved in the control of breathing, communication between different parts of the brain, and sensations such as hearing, taste, and balance.

The Brain: Brainstem

The Brain: Brainstem

Medulla Oblongata

It is the outer aspect is composed of white matter, and centrally the grey matter.

Some cells constitute relay stations for sensory nerve cells passing from the spinal cord to the cerebrum.

• In its deeper structure lie vital centres
• Cardiac centre
• Respiratory centre
• Vasomotor centre

Reflex centres of vomiting, coughing, sneezing and swallowing

Other special features in medulla oblongata

Decussation of the pyramids: Motor nerves from the cerebral cortex to the spinal cord cross from one side the other, so that the left hemisphere of the cerebrum controls the right half of the body.

Sensory decussating: Also occurs at the medulla, although some sensory nerves cross over at lower levels of the spinal cord.

The Brain: Brainstem

46

Ventricular System of the Brain

Within the brain there are four irregular shaped cavities containing cerebrospinal fluid. They are called ventricles, these are oRight and left lateral ventricles

Communicate through holes or foramen as summarized below

• Lateral ventricles
• These cavities lie within the cerebral hemispheres, one on each

side of the median plane just below the corpus callosum.

They are separated from each other by a thin membrane, the septum lucidium, and are lined by ciliated epithelium.

• They open into the 3rd ventricle through the interventricular foramina (of Monro).

Third ventricle

It is a cavity situated below the lateral ventricles between the two parts of the thalamus.

It is a slit-like cavity which is continuous with the cerebral aqueduct a narrow channel in the midbrain connecting the 3rd and 4th ventricles.

Ventricular System of the Brain

Fourth ventricle

It is situated below and behind the third ventricle, between the cerebellum and pons.

It communicates with the subarachnoid space by 3 foramina in its roof, and continuous below with central canal of the spinal cord.

CSF drains from the 4th ventricle through a single median aperture and paired lateral apertures into the subarachnoid space.

o These apertures are the only means by which CSF enters the subarachnoid space. If they are blocked, the ventricles distend, producing compression of the cerebral hemispheres.

Ventricular System of the Brain

Cerebro-Spinal Fluid (1)

Cerebrospinal fluid is a clear liquid produced within spaces in the brain called ventricles.

It is also found inside the subarachnoid space of the meninges which surrounds both the brain and the spinal chord.

In addition, a space inside the spinal chord called the central canal also contains cerebrospinal fluid

Cerebrospinal fluid is formed by choroidal epithelial cells of the choroid plexuses in the lateral, 3rd, and 4th ventricles

• Composition of CSF: It consists of
• Water
• Mineral salts
• Glucose
• Plasma proteins: small amount of albumin and globulin
• Small amount of creatinine, urea
• A few leukocytes
• Normal CSF pressure is 10cm of water when supine, and 30cm of water when upright.
• It is slightly alkaline

Cerebro-Spinal Fluid (2)

Flow of CSF (1)

Although cerebrospinal fluid is manufactured in all of the ventricles, it circulates through the system in a specific pattern, moving from the lateral ventricle to the third, and then from the third to the fourth.

From the fourth ventricle, the cerebrospinal fluid passes into the subarachnoid space where it circulates around the outside of the brain and spinal cord and eventually makes its way to the superior sagittal sinus via the arachnoid granulations also called arachnoid villi.

Most CSF flows into the interpeduncular and quadrigeminal cisterns.

CSF from the various cisterns flows superiorly through the sulci and fissures on the medial and superolateral surfaces of the cerebral hemispheres.

CSF also passes into the extensions of the subarachnoid space around the cranial nerves.

In the superior sagittal sinus, the cerebrospinal fluid is reabsorbed into the blood stream.

The main site of CSF absorption into the venous system is through the arachnoid granulations, protrusions of arachnoid villi into the walls of dural venous sinuses, especially the superior sagittal sinus and its lateral venous lacunae.

Flow of CSF (2)

57

Cranial nerves

Cranial nerves are the nerves that emerge directly from the brain (including the brainstem) Each cranial nerve is paired and is present on both sides. The numbering of the cranial nerves is based on the order in which they emerge from the brain, front to back (brainstem).

The terminal nerves, olfactory nerves (I) and optic nerves (II) emerge from the cerebrum or forebrain, and the remaining ten pairs arise from the brainstem, which is the lower part of the brain.

Olfactory nerve (I)

The olfactory nerve, or cranial nerve I, is the first of the 12 cranial nerves.

It is instrumental in the sense of smell (arises from the stimulation of olfactory (or odorant) receptors. The olfactory nerve is the shortest of the 12 cranial nerves The olfactory nerves consist of a collection of many sensory nerve fibers that extend from the olfactory epithelium to the olfactory bulb, passing through the many openings of the cribriform plate of the ethmoid bone.

Optic nerve (II)

The optic nerve (cranial nerve II) receives visual information from photoreceptors in the retina and transmits it to the brain It transmits visual information from the retina to the brain.

The optic nerve leaves the orbit, which is also known as an eye socket, via the optic canal, running posteromedially toward the optic chiasm, where there is a partial decussation (crossing) of fibers from the nasal visual fields of both eyes.

Optic nerve (II) cont..

The optic nerve transmits all visual information including brightness perception, color perception, and contrast. It also conducts the visual impulses that are responsible for two important neurological reflexes: the light reflex and the accommodation reflex.

The light reflex refers to the constriction of both pupils that occurs when light is shone into either eye; the accommodation reflex refers to the swelling of the lens of the eye that occurs when one looks at a near object, as in reading.

Oculomotor nerve (III)

The oculomotor nerve (cranial nerve III) controls eye movement, such as constriction of the pupil and open eyelids.

Controls most of the eye’s movements, including constriction of the pupil and maintaining an open eyelid by innervating the levator palpebrae superioris muscle.

All extraocular muscles, except for the superior oblique muscle and the lateral rectus muscle

Trochlear nerve (IV)

The trochlear nerve (cranial nerve IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.

Trigeminal nerve (V)

The trigeminal nerve is the fifth cranial nerve and it is responsible for sensation and motor function in the face and mouth.

The sensory function of the trigeminal nerve is to provide tactile, motion, position, and pain sensations for the face and mouth; its motor function activates the muscles of the jaw, mouth, and inner ear.

The trigeminal nerve has three major branches on each side—the opthalmic nerve, maxillary nerve, and mandibular nerve—that converge on the trigeminal ganglion.

Brain, Cranial Nerve And Supply

The motor component of the mandibular division (V3) of the trigeminal nerve controls the movement of eight muscles, including the four muscles of mastication: the masseter, the temporal, and the medial and lateral pterygoids.

Trigeminal nerve (V) cont

Abducens nerve (VI)

The abducens nerve (cranial nerve VI) controls the lateral movement of the eye through innervation of the lateral rectus muscle.

Facial nerve (VII)

The facial nerve (cranial nerve VII) determines facial expressions and the taste sensations of the tongue.

Voluntary facial movements, such as wrinkling the brow, showing teeth, frowning, closing the eyes tightly (inability to do so is called lagophthalmos), pursing the lips, and puffing out the cheeks, all test the facial nerve.

Taste can be tested on the anterior 2/3 of the tongue.

Vestibulocochlear nerve (VIII)

The vestibulocochlear nerve (cranial nerve VIII) carries information about hearing and balance.

It emerges from the pons and exits the inner skull via the internal acoustic meatus (or internal auditory meatus) in the temporal bone.

The vestibulocochlear nerve comprises the cochlear nerve that transmits hearing information, and the vestibular nerve that transmits balance information.

Glossopharyngeal nerve (IX)

The glossopharyngeal nerve (cranial nerve IX) is responsible for swallowing and the gag reflex, along with other functions.

It controls muscles in the oral cavity and upper throat, as well as part of the sense of taste (posterior 1/3 of the tongue) and the production of saliva.

Vagus nerve (X)

The vagus nerve (cranial nerve X) is responsible for parasympathetic output to the heart and visceral organs.

The vagus nerve (cranial nerve X) sends information about the body’s organs to the brain and carries some motor information back to the organs.

The vagus nerve is responsible for heart rate, gastrointestinal peristalsis, and sweating, to name a few.

Brain, Cranial Nerve And Supply

Vagus nerve is responsible for such varied tasks as heart rate, gastrointestinal peristalsis, and quite a few muscle movements in the mouth, including speech (via the recurrent laryngeal nerve), swallowing, and keeping the larynx open for breathing (via action of the posterior cricoarytenoid muscle, the only abductor of the vocal folds).

• Afferent fibers that innervate the inner (canal) portion of the outer ear

Vagus nerve (X) cont..

Accessory nerve (XI)

The accessory nerve (cranial nerve XI) controls the muscles of the shoulder and neck.

Responsible for tilting and rotating the head, elevating the shoulders, and adducting the scapula.

Controls the sternocleidomastoid and trapezius muscles of the shoulder and neck.

Hypoglossal nerve (XII)

The hypoglossal nerve (cranial nerve XII) controls the muscles of the tongue.

While the hypoglossal nerve controls the tongue’s involuntary activities of swallowing to clear the mouth of saliva, most of the functions it controls are voluntary, meaning that the execution of these activities requires conscious thought.

Innervates all extrinsic and intrinsic muscles of the tongue, except for the palatoglossus.

Controls tongue movements of speech, food manipulation, and swallowing

Blood supply of the head and neck

The blood supply to the brain is derived from the internal carotid and vertebral arteries which lie in the subarachnoid space.

Venous drainage occurs via cerebral and cerebellar veins that drain to the adjacent dural venous sinuses.

81

Main Arteries and Veins of Neck

Common Carotid Artery

The right common carotid artery arises from the brachiocephalic artery behind the right sternoclavicular joint The left artery arises from the arch of aorta in the superior mediastenum Runs upward through the neck

Divides into external and internal carotid arteries

Carotid Sinus

At its point of division, the common carotid artery shows a localized dilatation, called carotid sinus It serves as a reflex pressoreceptor mechanism A rise in blood pressure causes a slowing of the heart rate and vasodilatation of the arterioles

Common Carotid Artery

• It is embedded in the carotid sheath throughout its course

Closely related with the internal jugular vein and vagus nerve Apart from the two terminal branches, the common carotid artery gives off no branch in the neck

Relations

Anterolaterally: The skin, fascia, sternocleidomastoid, sternohyoid, sternothyroid, and posterior belly of omohyoid Posteriorly: The transverse processes of lower four cervical vertebrae, the prevertebral muscles, sympathetic trunk, vertebral vessels in the lower part of the neck

Relations

Medially: The larynx, pharynx, and below these, the trachea and esophagus, the lobe of thyroid gland Laterally: The internal jugular vein, and posterolaterally, the vagus nerve

External Carotid Artery

• It is one of the terminal branches of the common carotid artery
• It supplies the structures in the neck, face, scalp, tongue and maxilla

Begins at the level of the upper border of the thyroid cartilage Terminates in the substance of the parotid gland by dividing into superficial temporal and maxillary arteries

External Carotid Artery

At its origin, where its pulsation can be felt, the artery lies within the carotid triangle At first, it lies medial to the internal carotid artery It is crossed by the posterior belly of the digastric and the stylohyoid

Branches

• Superior thyroid artery
• Ascending pharyngeal artery
• Lingual artery
• Facial artery
• Occipital artery
• Posterior auricular artery
• Superficial temporal artery

Maxillary artery

Superior Thyroid Artery

• Arises from the external carotid artery near its origin

It gives off a branch to the sternocleidomastoid The superior laryngeal artery pierces the thyrohyoid membrane with the internal laryngeal nerve

Ascending Pharyngeal Artery

It’s a long slender vessel that ascends on the wall of the pharynx, which it supplies

Lingual Artery

• The loop of the artery is crossed superficially by the hypoglossal nerve

It supplies the tongue

Facial Artery

It arises from the external carotid artery, just above the level of the tip of the greater cornu of hyoid bone It arches upward deep to reach the posterior part of the submandibular salivary gland It supplies the face

Occipital Artery

• It arises from the external carotid artery, opposite the facial artery

It passes upward and reaches the back of the scalp Its terminal part accompanies branches of the greater occipital nerve to supply the back of scalp

Posterior Auricular Artery

It arises from the external carotid artery, at the level of the upper border of the posterior belly of the digastric muscle It passes backward to reach the auricle

Superficial Temporal Artery

It is the smaller terminal branch of the external carotid artery It divides into anterior and posterior branches, which supply the skin over the frontal and temporal regions

Maxillary Artery

• It is the larger terminal branch of the external carotid artery in the parotid gland

It arises behind the neck of the mandible It runs upward and forward, leaves the infratemporal fossa by entering the pterygopalatine fossa

Branches of Maxillary Artery

• Inferior alveolar artery
• Middle meningeal artery
• Small branches to the external auditory meatus and the tympanic membrane

Small muscular branches supply the muscles of mastication

Internal Carotid artery

• It is one of the terminal branches of the common carotid artery
• It supplies the brain, the eye, the forehead, and the part of nose
• It begins at the level of the upper border of the thyroid cartilage

Ascends in the neck to the base of the skull

Internal Carotid artery

It enters the cranial cavity through the carotid canal in the petrous part of the temporal bone It lies embedded in the carotid sheath with the internal jugular vein and vagus nerve It gives off no branches in the neck

Relations

Anterolaterally: Below the digastric lie the skin, the fascia, anterior border of sternocleidomastoid and the hypoglossal nerve Above the digastric lie the stylohyoid and the stylopharyngeus muscles, the glossopharyngeal nerve, the pharyngeal branch of vagus nerve, the parotid gland and the external carotid artery

Relations

Posteriorly: The sympathetic trunk, longus capitis muscle, and the transverse processes of the upper three cervical vertebrae Medially: The pharyngeal wall and the superior laryngeal nerve Laterally: The internal jugular vein and the vagus nerve

Arterial blood supply to the brain

• There are two paired arteries which are responsible for the blood supply to the brain
• -vertebral artery

Internal carotid artery

Brain, Cranial Nerve And Supply

These arteries arise in the neck and ascend to the cranium within the cranial vault the terminal branches of the arteries form anastomotic circle called circle of wills From the circle branches arise which supply majority part of the cerebrum

Other parts like pons and spinal cord are supplied by smaller branches from vertebral artery

Brain, Cranial Nerve And Supply

Once in the cranial cavity the internal carotid pass anteriorly through the cavernous sinus distal to cavernous sinus each internal carotid artery give rise to -ophthalmic artery =supplying the structure of orbit -posterior communicating artery =acting as an anastomotic connecting vessels in the circle of wills

Anterior choroidal artery

• -supplies structures in the brain important for motor control and vision
• Anterior cerebral artery

-supplies parts of cerebrum

The internal carotid then continues as the middle cerebral artery which supplies the lateral portion of the cerebrum

Vertebral arteries

The right and left vertebral arteries arise from subclavian arteries Then they ascend the posterior aspect of the neck through the holes in the transverse process of the cervical vertebrae known as foramen transversarium Enters the cranial cavity through foramen magnum then gives the following branches

Meningeal branch –supplying falx cerebelli,a sheet of dura matter

Anterior and posterior spinal arteries- supplying the spinal chord, spanning its entire length Posterior inferior cerebellar artery- supply the cerebellum

The two arteries converge to form the basilar artery

• Branches of this basilar artery supplying the cerebellum and pons

The basilar artery terminates by bifurcating into the posterior cerebral artery

Arterial circle of willis

Terminal branches of vertebral and internal carotid arteries all anastomose to form a circular blood vessels called circle of willis

Circle of willis

121

Three main branches of circle of Willis

• Anterior cerebral artery
• =terminal branches of internal carotid artery
• Internal carotid artery
• =located proximal to the origin of the middle cerebral arteris
• Posterior cerebral artery

-=terminates branches of basilar artery

To complete the circle two connecting vessels are also present

Anterior communicating artery=connects the two anterior cerebral arteries Posterior communicating artery=connects the internal carotid artery and posterior cerebral artery

Veins of the Neck

External Jugular Vein

The external jugular vein is formed behind the angle of the jaw by the union of the posterior auricular vein with the posterior division of the retromandibular vein It descends across the sternocleidomastoid muscle and beneath the platysma muscle It drains into the subclavian vein behind the middle of the clavicle

Anterior Jugular Vein

• The anterior jugular vein descends in the front of the neck close to the midline
• Just above the sternum, it is joined to the opposite vein by the jugular arch

It joins the external jugular vein deep to the sternocleidomastoid muscle

Internal Jugular Vein

The internal jugular vein is a large vein that receives blood from the brain, face, and neck It starts as a continuation of the sigmoid sinus and leaves the skull through the jugular foramen

Internal Jugular Vein

It then descends through the neck in the carotid sheath lateral to the vagus nerve and the internal and common carotid arteries It ends by joining the subclavian vein behind the medial end of the clavicle to form the brachiocephalic vein

Internal Jugular Vein

Throughout its course, it is closely related to the deep cervical lymph nodes The vein has a dilatation at its upper end called the superior bulb and another near its termination called the inferior bulb Directly above the inferior bulb is a bicuspid valve

Tributaries of Internal Jugular Vein

• Inferior petrosal sinus
• Facial vein
• Pharyngeal veins
• Lingual vein
• Superior thyroid vein

Middle thyroid vein

Lymphatic drainage of the head and neck

134

INTRODUCTION

• All the lymph from the region of head and neck drains into deep cervical lymph nodes.
• The efferents from these nodes form the jugular trunk.
• On the right side, jugular trunk drains into right lymphatic duct.

On the left side, jugular trunk drains into thoracic duct.

INTRODUCTION CONTD…

Out of total 400-450 lymph nodes of human body, ~60-70 nodes are located in the region of head and neck.

• Lymph nodes in the head and neck region can be grouped into:
• Superficial nodes.

Deep nodes.

SUPERFICIAL LYMPH NODES

Lie above the investing layer of deep cervical fascia.

Consists of a few small nodes lying superficial to the external jugular and anterior jugular veins.

• Includes:-
• Submental nodes.
• Submandibular nodes.
• Buccal nodes.
• Parotid (preauricular) nodes.
• Mastoid (postauricular or retroauricular) nodes.
• Occipital nodes.
• Superficial cervical nodes.

Anterior cervical nodes.

SUPERFICIAL CERVICAL NODES

These are offshoot of superficial parotid nodes.

Located superficial to upper part of sternocleidomastoid by the side of external jugular vein.

ANTERIOR CERVICAL NODES

• Arranged along the anterior jugular vein.
• AFFERENTS- from
• Anterior triangle of neck below the hyoid bone.
• EFFERENTS- drain into

Lower deep cervical nodes.

DEEP LYMPH NODES

• Deep cervical nodes.
• Waldeyer’s ring.

Nodes of midline.

NODES OF MIDLINE

• Termed in correspondence to the anatomical area where they exist:
• Infrahyoid.
• Prelaryngeal.
• Pretracheal.

Paratracheal.

DEEP CERVICAL LYMPH NODES

All the lymph from the region of head and neck drains directly or indirectly into a vertical chain of deep cervical lymph nodes.

Deep cervical lymph nodes surround the internal jugular vein and extend from base of the skull to the root of neck.

DEEP CERVICAL LYMPH NODES CONTD…

• Subdivided into 2 groups by the intermediate tendon of omohyoid.
• Upper deep cervical nodes.
• Lower deep cervical nodes.

UPPER DEEP CERVICAL NODES-

• Lie along the upper part of internal jugular vein deep to sternocleidomastoid muscle.

LOWER DEEP CERVICAL NODES-

Lie along the lower part of internal jugular vein deep to sternocleidomastoid muscle.

UPPER DEEP CERVICAL LYMPH NODES

JUGULO-DIGASTRIC NODES-

Member of upper deep cervical group.

LOWER DEEP CERVICAL LYMPH NODES

JUGULO-OMOHYOID NODES-

• Member of lower deep cervical group.

These nodes act as principal nodes of tongue.

LOWER DEEP CERVICAL LYMPH NODES CONTD…

VIRCHOW’S NODES-

• Left supraclavicular nodes or left scalene nodes.

Enlarged in malignancy of stomach.

LYMPH NODES OF HEAD &NECK

CLASSIFICATION OF LYMPH NODES-

• Peripheral.
• Terminal.

Peripheral Lymph Nodes-

• Arranged in outer and inner circles.

OUTER CIRCLE-

• Forms a pericervical or cervical collar at the junction of head and neck.
• It includes:-
• Submental nodes.
• Submandibular nodes.
• Buccal nodes.
• Parotid (preauricular) nodes.
• Mastoid (postauricular or retroauricular) nodes.

Occipital nodes.

LYMPH NODES OF HEAD &NECK CONTD…

INNER CIRCLE-

• Surrounds the upper part of respiratory and alimentary passages.
• It includes:-
• Prelaryngeal nodes.
• Pretracheal nodes.
• Paratracheal nodes.

Retropharyngeal nodes.

PRELARYNGEAL NODES

• Located in front of conus elasticus.

PRETRACHEAL NODES-

In front of trachea and above the isthmus of thyroid gland.

SUBMENTAL NODES

• Located in the submental triangle.
• 3 or 4 in number.
• Situated on mylohyoid muscles between the anterior bellies of both digastric muscles.
• AFFERENTS- from
• Tip of tongue.
• Floor of mouth.
• Lower gums opposite the
• incisor teeth.
• 4. Central part of lower lip.
• EFFERENTS- into
• Sub-mandibular nodes.

Jugulo-omohyoid nodes.

SUBMANDIBULAR NODES

Located in the digastric triangle beneath the deep cervical fascia in contact with the submandibular salivary gland.

3 in number.

SUBMANDIBULAR NODES CONTD…

• AFFERENTS- from
• Centre of forehead.
• Medial angle of eye.
• Side of the nose.
• Cheek and angle of mouth.
• Whole of the upper lip.
• Lateral part of lower lip.
• Anterior 2/3rd of the tongue.
• Upper gums.
• Lower gums.
• Frontal, maxillary and most of the ethmoidal sinuses.

Submental lymph nodes.

SUBMANDIBULAR NODES CO NTD…

Mainly jugulo-omohyoid and partly into jugulo-digastric nodes.

BUCCAL NODES

• One member of submandibular nodes.

Lies on the buccinator.

BUCCAL NODES

• AFFERENTS- from
• Part of the cheek.
• Lower eyelid.
• EFFERENTS- into

Upper deep cervical nodes.

PAROTID (PREAURICULAR) NODES

Lie superficial and deep to the fascial capsule of parotid gland and within its substance.

• Divided into 2 groups:-
• Superficial group.
• Deep group.

SUPERFICIAL GROUP-

• Receives afferents from-
• Upper part of forehead.
• Temporal region.
• Upper part of lateral surface of auricle.
• Anterior wall of external acoustic meatus.
• Eyelids.

DEEP GROUP-

• Receives afferents from-
• Nasopharynx.
• Posterior part of the nose.
• Tympanic cavity.
• EFFERENTS- drain into

Upper deep cervical nodes.

MASTOID (POSTAURICULAR) NODES

• Lie superficial to the sternocleidomastoid near its attachment to the mastoid process.
• AFFERENTS- from
• Upper part of cranial surface of auricle.
• Adjoining portion of the scalp.

Posterior wall of external acoustic meatus.

MASTOID (POSTAURICULAR) NODES CONTD…

• EFFERENTS- drain into

Upper deep cervical nodes.

OCCIPITAL NODES

• Located at the apex of posterior triangle superficial to the trapezius.
• AFFERENTS- from
• Posterior part of the scalp.
• EFFERENTS- drain into

Supra-clavicular nodes.