Head and Neck I PDF

ANATOMY | TRANS 8 LE Head and Neck I ALEXANDRIA R. BAYAOA, MD | (10/16/2023) | Version #2...

ANATOMY | TRANS 8 LE Head and Neck I ALEXANDRIA R. BAYAOA, MD | (10/16/2023) | Version #2 02 OUTLINE ✔ Identifying surface anatomical landmarks in the head region ✔ Describe the layers of the scalp noting the dangerous layer. I. Surface Anatomical C. Posterior Triangle ✔ Defining emissary veins and enumerating the more constant Landmarks of the Head D. Contents of the Posterior ones. A. Regions of the Head Triangle ✔ Explaining why transverse scalp lacerations gape and bleed quite 1. Neurocranial Portion 1. Occipital Triangle profusely. 2. Viscerocranial Portion 2. Omoclavicular Triangle ✔ Demonstrate the knowledge & understanding of anatomy of the 3. Child’s Head E. Lateral Cervical Region superficial neck by: B. Surface Anatomy of the VI. Muscles of Facial Identifying surface anatomical landmarks in the neck region Face Expression Describing the disposition of the cervical fascia, noting fascial 1. Parts of the Face A. Muscles of the Scalp planes and explaining how infections in the neck may extend 2. Cranium B. Muscles of the Face downwards to the mediastinum. II. Skull 1. Muscles of the Eyelids ✔ Describing the division of the neck into anterior and posterior A. Adult Skull 2. Muscles of the Nose triangles and their further subdivision into smaller triangles. 1. Facial Bones 3. Muscles of the Lips ✔ Describing the gross anatomy of the parotid gland, noting the 2. Calvaria 4. Muscles of the Mouth structures running through its substance and opening of its duct B. Newborn Skull and Lips into the oral cavity. C. Cranium 5. Muscles of the Cheeks ✔ Describing the submandibular gland and the suprahyoid group of D. Base of the Skull VII. Mandible muscles, their actions and innervations. E. Foramina of the Cranial A. Parts of the Mandible ✔ Describing the infrahyoid muscles including their action and nerve Base B. Muscles of Mastication supply. III. Scalp VIII. Temporomandibular 📋 A. Five Layers of the Scalp Joint I. SURFACE ANATOMICAL LANDMARKS OF THE HEAD 📖 B. Muscles of the Scalp IX. Suprahyoid and Infrahyoid A. REGIONS OF THE HEAD C. Emissary Veins Muscles The head is divided into regions to allow clear communications IV. Fascial Layers of the A. Suprahyoid Muscle Group regarding the location of structures, injuries, or pathologies Neck B. Infrahyoid Muscle Group These head regions consists of two: A. Superficial Cervical Fascia X. Salivary Glands → neurocranial portion of the Neck A. Parotid Gland → viscerocranial portion B. Deep Cervical Fascia of B. Submandibular Gland 📖 Corresponds the Neck C. Sublingual Gland NEUROCRANIAL PORTION C. Fascial Spaces of the XI. Review Questions to the underlying bones or bony features, except for Neck XII. References the auricular region, which consist of the external ear D. Carotid Sheath XIII. Appendix → Frontal E. Danger Space in Neck → Parietal V. Triangles of the Neck → Occipital A. Anterior Triangle → Temporal B. Contents of the Anterior → Auricular (Includes the external ear) Triangle → Mastoid 1. Submental Triangle 2. Submandibular Triangle 3. Carotid Triangle 4. Muscular Triangle Must Lecturer Book Previous Youtube ❗️ Know 💬 📖 📋 Trans 🔺 Video SUMMARY OF ABBREVIATIONS DNM Descending Necrotizing Mediastinitis SCM Sternocleidomastoid muscle CN I Cranial Nerve I (Olfactory Nerve) CN II Cranial Nerve II (Optic Nerve) CN III Cranial Nerve III (Oculomotor Nerve) CN IV Cranial Nerve IV (Trochlear Nerve) Figure 1. Regions of the head[Moore] CN V Cranial Nerve V (Trigeminal Nerve) CN VI CN VII Cranial Nerve VI (Abducens Nerve) Cranial Nerve VII (Facial Nerve) 📖 Includes VISCEROCRANIAL PORTION the facial region, which is divided into five bilateral and three median regions related: CN VIII Cranial Nerve VIII (Vestibulocochlear Nerve) → Superficial features CN IX Cranial Nerve IX (Glossopharyngeal Nerve) ▪ Oral CN X Cranial Nerve X (Vagus Nerve) ▪ Buccal CN XI Cranial Nerve XI (Spinal/Accessory Nerve) → Deeper soft tissue formations CN XII Cranial Nerve XII (Hypoglossal Nerve) ▪ Parotid → Skeletal features LEARNING OBJECTIVES ▪ Orbital ✔ Identify the principal parts of the skull & various foramina ▪ Infra-orbital including important structures passing through them. ▪ Nasal ✔ Identifying the bony and soft tissue structures of the head and ▪ Zygomatic neck appreciated on different radiograph studies. ▪ Mental LE 1 TG 10 & 11 | Reyes, I., Reyes, K., Reyes, L., Reyes, M., TE | Ramos, Punzalan, Quimson AVPAA | J. TIOSEJO PAGE 1 of 14 TRANS 1 Reyes, P., Reyes, R., Reyes, Y., Ricafort, A., Ricafort, B., Ridulme, Rio, Rival, Rivera, A., Rivera, D. ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD CHILD’S HEAD → Oral fissure ▪ Surrounds the opening of the mouth → Vermillion border of the lip ▪ Beginning of the transitional zone between mucous membrane and skin of the lip ▪ Transitional zone - skin region that is thin and hairless ▪ The increasing sensitivity of the transitional zone causes the color of the lip to change compared to the adjacent skin of the face. → Labial commissure ▪ Lateral junction of the lips ▪ Angle between the lips (medial) and the commissure increases as the mouth opens and decreases as it close (angle of the mouth) → Tubercle of upper lip ▪ Median part of the lip → Philtrum Figure 2. Anteriorposterior view of CT showing paranasal sinuses ▪ Superior to the tubercle of upper lip in a child cranium[Moore] ▪ Shallow groove all the way to the nasal septum → Cheek/Maxillary Area 📖 Paranasal sinuses Pneumatized (air-filled) bones contains sinuses or cells that ▪ Lateral continuation of musculofibrous folds of the lips ▪ Contains the buccinator muscle and buccal fat 📋 appear as radiolucencies (dark areas) Air-filled extensions of the respiratory part of nasal cavities → Nasolabial sulcus (smile or laugh lines) ▪ Separates the cheek from the lips 📖 📖 in certain cranial bones Most paranasal sinuses are rudimentary or absent at birth The growth of paranasal sinuses are important in the alteration ▪ Oblique orientation between the ala of the nose and angle of the mouth → Mentolabial sulcus 📋 of face shape and the addition of resonance to the voice Named according to the cranial bones in which they are ▪ Separates the lips from the mental protuberance (chin) located in: ▪ Frontal - less developed 📋 → Malar area 📋 Responsible for giving the prominent cheekbones Contains the malar bone ▪ Ethmoid ▪ Sphenoid ▪ Maxillary - well developed 📖 The B. SURFACE ANATOMY OF THE FACE Despite infinite variations, the human face are constant. underlying bone structures determine the shape of the face. PARTS OF THE FACE Eye Region → Eyebrows (L. supercilia) ▪ Linear growths of hair overlying the supra-orbital margin → Glabella ▪ The hairless region between the eyebrows → Superciliary arches ▪ Located above the eyebrows ▪ Prominent ridges that extend laterally → Eyelids (L. palpebrae) ▪ Mobile ▪ Musculofibrous folds that overlies the eyeball Figure 3. Surface anatomy of face[Moore] ▪ Upper and lower folds that covers the eyeball when closed ▪ Joined at each end of palpebral fissure at medial and CRANIUM lateral canthi of the eye → Epicanthal fold ▪ Fold of skin that covers the medial canthi of the eye ▪ Prominent in Asians → Suprapalpebral sulci and Infrapalpebral sulci ▪ Depressions superior and inferior to the eyelids Nose → Apex ▪ Tip of the nose ▪ Continuous with the forehead (root of the nose/bridge) → Dorsum of the nose ▪ Rounded anterior border between apex and root (bridge) → Naris ▪ Plural = nares ▪ Inferior to the apex ▪ Nasal cavities found in each opening ▪ Medially bounded by nasal septum Figure 4. Radiograph of cranium[Moore] ▪ Laterally bounded by ala of the nose → Nasal septum II. SKULL ▪ Bounds the nares medially A. ADULT SKULL → Ala of the nose The skeleton of the head is composed of 22 bones: ▪ Bounds the nares laterally → Facial bones = 14 Lip region → Calvaria = 8 ANATOMY Head and Neck I PAGE 2 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD 📋 Houses the structure of the ears Frontal (1) → Squamous part ▪ Forms the skeleton of the forehead, articulating inferiorly with the nasal and zygomatic bones. Parietal (2) → Forms the lateral wall of the calvaria Occipital (1) → Consists of the occiput (back of head, convex posterior protuberance of the squamous part of the occipital bone), parts of the parietal bones, and mastoid parts of the temporal bones. Sphenoid (1) 📖 → Not shown in the figure Irregular unaired bone that consists of three pairs of processes: greater wings, lesser wings, and pterygoid processes Figure 5. Anterior view of the skull, including the mandible[Netter] 📖 → Greater wings and Lesser wings Spread laterally from the lateral aspects of the body of the sphenoid 📖 FACIAL BONES → Pterygoid processes Zygomatic (2) Lateral and medial pterygoid plates - extend inferiorly on → Known as cheek bones and malar bones each side of the sphenoid from the junction of the body and → Forming the prominences of the cheeks greater wings → Lie on the inferolateral sides of the orbits Ethmoid (1) 📖 → Rests on the maxillae → Not shown in the figure → Zygomaticofacial foramen: Irregular bone that makes a minor midline contribution to the ▪ Pierces the lateral aspect of each bone neurocranium Maxillae (2) → Primarily part of the viscerocranium → Forms the upper jaw Sutures 💬 → Contains alveolar processes (tooth sockets) that supports the → Coronal maxillary teeth Divides the calvaria to anterior and posterior Nasal (2) ▪ Divides frontal and parietal bones 💬 → Nasions → Sagittal ▪ Intersects between the frontal and nasal bones Divides the calvaria to left and right 📋 Lacrimal (2) ▪ Separates between two parietal bones 📋💬 Small bone forming part of the eye socket → Lambdoid Vomer (1) Located in the occipital region → Flat, unpaired trapezoidal-shaped bones that forms a major Separates parietal and temporal bones from occipital part of the bony nasal septum bones located at the occipital region 📋 Palatine (2) Its horizontal plate forms the hard palate, together with the palatine process of the maxilla B. NEWBORN SKULL 📋 Inferior nasal concha (2) Bone forming the lower part of the lateral wall of the nasal 📋 cavity Turbinate (inverted cone), soft tissue of the nasal cavity Mandible (1) → U-shaped bone with an alveolar part that supports the mandibular teeth 💬 CALVARIA Skull minus the facial bones Dome-like roof Figure 7. Skull of Newborn[Lecture PPT] 📖 Fontanelles → Fibrous membranes separating the bones of the calvaria of neonates → Perceived as “soft spots” in babies 📋 → Anterior fontanelle Large fontanelle bound by the halves of the frontal bone anteriorly and the parietal bones posteriorly ▪ Closes after 18 months Temporal (2) Figure 6. Superior view of the skull [Netter] 📋 → Posterior fontanelle Triangular fontanelle bound by the parietal bones anteriorly and occipital bones posteriorly 📋 → Laterally located Forms the cranial base with the sphenoid bone ▪ Closes at the end of the first year ANATOMY Head and Neck I PAGE 3 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD 📖 The C. CRANIUM skeleton of the head has two parts: → Neurocranium ▪ Bony case of the brain and its membranous coverings, the cranial meninges ▪ In adults, it is formed by a series of eight bones: − four singular bones centered on the midline (frontal, ethmoidal, sphenoidal, and occipital), and − two sets of bones occurring as bilateral pairs (temporal and parietal) ▪ Dome-like roof: − Roof: Calvaria − Floor: Cranial base → Viscerocranium ▪ Facial skeleton ▪ Forms the anterior part of the cranium ▪ Consists of the bones surrounding the mouth (upper and lower jaws), nose/nasal cavity, and most of the orbits (eye sockets or orbital cavities) ▪ Consists of 15 irregular bones: − 3 singular bones centered on or lying in the midline: o Mandible o Ethmoid o Vomer − 6 bones occurring as bilateral pairs: o Maxillae o Inferior nasal conchae o Zygomatic o Palatine o Nasal o Lacrimal Figure 9. Superior view of the Cranial Base[Netter] E. FORAMINA OF THE CRANIAL BASE Figure 8. Lateral view of the skull (See the pterion)[Lecture PPT] 📖 Pterion 📋 Any fracture of the area is extremely dangerous → Thinnest part of the lateral wall of the skull → H-shaped formation of sutures that unite the frontal, parietal, sphenoid, and temporal bones 📖 Divided D. BASE OF THE SKULL into three compartments/depressions which form the 📖bowl-shaped floor of the cranial cavity: Anterior cranial fossa houses the: ▪ Frontal bone ▪ Ethmoid bone 📖 ▪ Sphenoid bone (lesser wing) Middle cranial fossa houses the: ▪ Sphenoid bone (greater wing) Figure 10. Superior view of the Foramina of Cranial Base[Netter] 📖→ Foramen ▪ Parietal bones 📖 ▪ Temporal bone Posterior cranial fossa houses the: ▪ Temporal bone lacerum Filled in by cartilage and fibrous connective tissue ▪ Parietal bones ▪ Occipital bone ANATOMY Head and Neck I PAGE 4 of 14  ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD ❗️theTable 1. Summary of the more important openings in the base of skull and the structures that pass through them → Thick, dense, richly vascularized subcutaneous layer that is well supplied with cutaneous nerves Opening in Skull Structures Transmitted → If there is a wound in this layer, it would be bloody because Anterior Cranial Fossa the blood vessels are enmeshed in the fibrous septa and Perforations in cribriform plate Olfactory nerves (CN I) cannot retract. Aponeurosis/ Aponeurotic Layer Middle Cranial Fossa → Epicranial Aponeurosis or Galea Aponeurotica Optic canal Optic nerve (CN II), → Independent of each other in contraction Ophthalmic artery ▪ Independent contraction of the occipital belly retracts the Superior orbital fissure Oculomotor (CN III), Trochlear scalp/pulls the scalp posteriorly. (CN IV), Abducens (CN VI), ▪ Contraction of the frontal belly protracts the scalp/pulls the Lacrimal, Frontal, and scalp anteriorly. Nasociliary nerves, Ophthalmic trigeminal division nerve of (V1), 💬 → Subaponeurotic space Potential space beneath the epicranius Foramen rotundum Superior ophthalmic vein Maxillary division of the 💬 Loose Connective Tissue veins Most dangerous layer because it contains the emissary trigeminal nerve (V2) Pericranium Layer (Periosteum) Foramen ovale Mandibular division of the trigeminal nerve (V3), Lesser petrosal nerves 💬 → Contains diploic veins Drains the diploic space and eventually drains into the dural venous sinuses Foramen spinosum Foramen lacerum Middle meningeal artery Internal Carotid Artery, 💬 The veins of the scalp anastomose with the pterygoid venous plexus and with the dural venous sinuses via the emissary veins Greater petrosal nerve, deep petrosal nerve Posterior Cranial Fossa B. MUSCLES OF THE SCALP Foramen magnum Medulla oblongata, Spinal part of accessory nerve, and Right and left vertebral arteries Hypoglossal canal Hypoglossal nerve (CN XII) Jugular foramen Glossopharyngeal (CN IX), Vagus (CN X), and Accessory (CN XI) nerves; where the sigmoid sinus becomes internal jugular vein Internal acoustic meatus Facial (CN VII), and Vestibulocochlear (CN VIII) nerves Condylar Canal Emissary vein that passess from sigmoid sinus to vertebral veins in the neck Mastoid foramen Mastoid emissary vein from sigmoid sinus and meningeal branch of occipital artery III. SCALP A. FIVE LAYERS OF THE SCALP Figure 12. Epicranius/ Occipitofrontalis[PPT] Epicranius/ Occipitofrontalis muscle → Responsible in raising the eyebrows (as in the expression of ❗️ surprise) A transverse scalp laceration of the epicranial aponeurosis would gape because the frontalis and occipitalis muscles pull ❗AGAINST each other in opposite directions In contrast, a parallel or longitudinal laceration of the epicranial aponeurosis to the muscle fibers of the occipitofrontalis muscles would not gape Table 2. Frontalis and Occipitalis Muscles Frontalis Occipitalis Characteristics No bony attachments Has bony attachments Origin Epicranial Lateral ⅔ of superior aponeurosis nuchal line ❗️For memorization Figure 11. The Layers of the Scalp [Lecture PPT] Insertion Skin and Posterior auricular on order of layers: SCALP subcutaneous tissue branch of CN VII of eyebrows and (facial nerve) Skin forehead → First layer → Thin layer, except in the occipital region Action Elevates eyebrows; Retracts scalp → Have numerous sebaceous glands and hair follicles wrinkles skin; → Abundant arterial supply, good venous and lymphatic drainage protracts scalp Connective Tissue Layer (Dense) → Where blood supply to the scalp are located ANATOMY Head and Neck I PAGE 5 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD C. EMISSARY VEINS B. DEEP CERVICAL FASCIA OF THE NECK Traverse cranial apertures and make connections between Investing layer intracranial venous sinuses and extracranial veins → Most superficial layer Commonly referred to as “messenger veins” → Encloses the sternocleidomastoid muscle and the trapezius Has clinical significance in determining the spread of infection 💬 from the extracranial fossa to the venous sinuses Example: spread of infection from the mastoid to the venous 💬 muscle Roofs over the anterior and posterior triangles of the neck Pretracheal fascia sinuses or from the paranasal sinuses to the cavernous sinus Prevertebral fascia Table 3. Constant Emissary Veins and Functions → Deepest/ closest to the vertebra Constant C. FASCIAL SPACES OF THE NECK Functions Emissary Veins Fascial spaces formed by the different fascia of the neck Mastoid emissary Connects the sigmoid sinus with the → In between fascias contribute to the formation of fascial spaces vein posterior auricular or occipital veins Posterior to anterior order of fascia behind the pharynx: Parietal emissary Connects the superior sagittal sinus with → Prevertebral Fascia veins the veins of the scalp → Alar Fascia Venous plexus of Connects the sigmoid sinus with the → Buccopharyngeal Fascia the canal hypoglossal internal jugular vein (IJV) 💬 Suprasternal Space (of Burns) 💬 Inferior to the hyoid bone The superficial layer of deep fascia divides into two leaves Condylar emissary Connects the sigmoid sinus and veins in veins the suboccipital triangle via the condylar with one side attaching to the anterior and the other to the canal posterior respectively to the jugular notch (Seen at Figure 15, Venous plexus of Connects the cavernous sinus to the red violet highlight) foramen ovale Occipital emissary pterygoid plexus via foramen ovale Connects the confluence of sinuses with ❗️ → The attachment of the two leaves form a space. Encloses inferior ends of the: ▪ Anterior jugular veins veins occipital vein through the occipital protuberance and receives the occipital ▪ Jugular venous arch diploic vein ▪ Fat ▪ Deep lymph nodes Retropharyngeal Space → Space between the alar fascia (red highlight) and prevertebral fascia (yellow highlight) give rise to retropharyngeal space 💬 (green highlight) Possible for blood, pus, or air to spread downwards to the superior mediastinum of the thorax Buccopharyngeal Space → Space between the alar fascia (red highlight) and buccopharyngeal fascia (purple highlight) gives rise to 💬 buccopharyngeal space (sky blue highlight). Connective tissue that passes around the sides and back of the binding posterior portion of the pharynx to the prevertebral 💬 fascia. The buccopharyngeal space protects the pharynx Figure 13. Emissary Veins[Moore] IV. FASCIAL LAYERS OF THE NECK Figure 15. Fascia and spaces of the neck. D. CAROTID SHEATH Figure 14. Cross section of the fascial layers of the neck[Netter] A. SUPERFICIAL CERVICAL FASCIA OF THE NECK Encloses the platysma muscles which contains the cutaneous vessels and nodes Figure 16. Carotid Sheaths ANATOMY Head and Neck I PAGE 6 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD A tubular structure (fascia) that encloses numerous vessels and A. ANTERIOR TRIANGLE 📖 ❗️ nerves Runs from the cranial base to the root of the neck Contents of the Carotid Sheaths: The boundaries are: the sternocleidomastoid muscle, the midline of the neck, and the lower margin of the body of the mandible Subdivisions and boundaries include: → Medial: Common carotid and internal arteries → Submental triangle → Lateral: Internal jugular vein → Submandibular (Digastric) triangle → Posterior: Vagus nerve → Carotid triangle → Deep cervical nerves → Muscular triangle → Carotid Sinus nerve Table 4. Borders of the Anterior Triangle → Deep cervical lymph nodes Aspect Structures E. DANGER SPACE IN NECK Refers to the thin connective tissue running from the base of the Anterior Median of the neck skull to the diaphragm Posterior Anterior border of the SCM The anterior of danger space is the Alar Fascia and posterior of it Superior Inferior border of the mandible is the Prevertebral Fascia. It extends to the transverse processes Apex Jugular notch of the manubrium of the vertebra laterally Roof Subcutaneous tissue containing the platysma Separated by sagittally-oriented fascia on each side of the neck Floor Pharynx, larynx, and thyroid gland from the parapharyngeal space → Extends from the anterior tubercle of the cervical vertebrae to the fascia of the posterolateral pharyngeal wall called Cloisonne sagittalis Since area is closed on all sides, inflammatory process in this space may arise from penetration of infection from surrounding spaces (retropharyngeal, parapharyngeal and prevertebral) When an abscess in the retropharyngeal space ruptures throughout the alar fascia, this commonly causes an infection → Descending Necrotizing Mediastinitis (DNM) Three pathways of DNM from neck to mediastinum: → Pretracheal route to anterior mediastinum → Lateral pharyngeal route to the lateral mediastinum → Most common: Retropharyngeal and danger space to poster mediastinum DEEP NECK ABSCESS 44 y/o male with diabetes who has a history of toothache or dental cavities in the lower mandibular molar region. Eventually, an abscess formed in the neck due to failure of antibiotics to contain infection. → Remember: Danger space (thin connective tissues that may Figure 18. Anterior Triangle of the Neck [PPT] most likely cause an infection) → Abscess caused by infection in the danger space. B. CONTENTS OF THE ANTERIOR TRIANGLE SUBMENTAL TRIANGLE Contents: V. TRIANGLES OF THE NECK → Submental lymph node The neck is divided into 2 triangles: anterior and posterior Table 5. Borders of the Submental Triangle ❗️ triangle by the sternocleidomastoid muscle (SCM) Use the sternocleidomastoid muscle as a marker to identify easily which is the anterior triangle and posterior triangle Aspect Structures Lateral Right & left anterior bellies of digastric muscle Inferior Body of hyoid Apex Mandibular symphysis Floor Mylohyoid muscle Base Hyoid bone ❗️ Also SUBMANDIBULAR TRIANGLE known as the Digastric Triangle Contents: → Submandibular gland → Facial artery and vein → Hypoglossal nerve (CN XII) → Mylohyoid nerve → Submandibular lymph nodes Table 6. Borders of the Digastric Triangle Aspect Structures Superior Inferior border of the mandible Inferior Posterior belly of the digastric muscle Medial Anterior belly of the digastric muscle Floor Mylohyoid and hyoglossus muscles and middle pharyngeal constrictor Figure 17. Lateral view of the muscles of the Neck [Netter] Sternocleidomastoid muscle (blue highlight), Posterior Triangle (green highlight), Anterior Triangle (yellow highlight) ANATOMY Head and Neck I PAGE 7 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD CAROTID TRIANGLE Contents: → Carotid sheath → External carotid artery → CN XI and XII → Superior root ansa cervicalis → Branches of the cervical plexus → Part of thyroid, larynx, pharynx → Deep cervical lymph nodes Table 7. Borders of the Carotid Triangle Aspect Structures Superior Posterior belly of the digastric Medial Superior belly of the omohyoid Lateral Anterior border of the SCM muscle [PPT] Figure 19. Posterior Triangle of the Neck ❗️ MUSCULAR TRIANGLE Also known as the Omotracheal Triangle Contents: D. CONTENTS OF THE POSTERIOR TRIANGLE OCCIPITAL TRIANGLE → Infrahyoid muscle Occipital artery appears on its apex → Viscera (Thyroid and Parathyroid glands) Contents: Table 8. Borders of the Muscular Triangle → External jugular vein → Parts of the cervical and brachial plexus Aspect Structures → CN XI Superior Hyoid bone → Cervical lymph nodes Medial Medial plane (midline) of the neck Table 10. Borders of the Occipital Triangle Superolateral Superior belly of the omohyoid Inferolateral Anterior border of the SCM muscle Aspect Structures Anterior Posterior border of the SCM Posterior Trapezius Base Inferior belly of omohyoid muscle OMOCLAVICULAR TRIANGLE Also known as the Subclavian/suprascapular triangle Contents: → Third part of the subclavian artery → Part of the subclavian vein → Suprascapular artery → Supraclavicular lymph nodes Table 11. Borders of the Omoclavicular Triangle Aspect Structures Anterior Posterior border of the SCM Posterior Inferior belly of omohyoid muscle Base Middle clavicle [PPT] Figure 18.1. Contents of the Anterior Triangle of the Neck C. POSTERIOR TRIANGLE Wraps around the lateral surface of the neck Region is covered by skin and subcutaneous tissue containing the platysma The boundaries are: the SCM muscle, the trapezius muscle, and the clavicle. Subdivision and boundaries include: → Occipital Triangle → Omoclavicular(Subclavian/Supraclavicular) Triangle Table 9. Borders of the Posterior Triangle Aspect Structures Anterior Posterior border of the SCM Posterior Anterior border of the trapezius Inferior Middle third of the clavicle between the trapezius and the SCM [PPT] Apex Where the SCM and the trapezius meet on Figure 20. Contents of the Posterior Triangle of the Neck the superior nuchal line of the occipital bone E. LATERAL CERVICAL REGION Roof Investing layer of the deep cervical fascia Includes the scalene and prevertebral muscles Floor Formed by muscles covered by the It descends almost vertically from the vertebral column to prevertebral layer of deep cervical fascia the first rib Other muscles: Splenius capitis → Levator scapulae → Middle scalenes → Posterior scalenes ANATOMY Head and Neck I PAGE 8 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD Table 12. Borders of the Lateral Cervical Region Anterior cervical region (anterior triangle) (D) Aspect Structures Submandibular Submandibular gland almost fills Anterior Carotid arteries, vagus nerve, internal jugular (digastric) triangle (4) triangle; submandibular lymph nodes; nerve, deep cervical nodes hypoglossal nerve (CN XII); mylohyoid Posterior Pleura, origin of brachial plexus, and 2nd part nerve; parts of facial artery and vein of subclavian artery Medial Vertebral artery and vein, sympathetic trunk, Submental triangle (5) Submental lymph nodes and small veins thoracic duct that unite to form anterior jugular vein Lateral Emerging branches of the cervical plexus, Carotid triangle (6) Carotid sheath containing common roots of the brachial plexus, 3rd part of the subclavian artery carotid artery and its branches; internal jugular vein and its tributaries; vagus nerve; external carotid artery and some of its branches; hypoglossal nerve (CN XII) and superior root of ansa cervicalis; spinal accessory nerve (CN XI); thyroid gland, larynx, and pharynx; deep cervical lymph nodes; branches of cervical plexus Muscular Sternothyroid and sternohyoid muscles; (omotracheal) triangle thyroid and parathyroid glands (7) VI. MUSCLES OF FACIAL EXPRESSION Embedded in the superficial fascia Most arise from the bones of the skull and are inserted into the skull Serve as sphincters or dilators of the eyelids, nostrils, and lips Origin: 2nd arch mesoderm [Netter] Figure 21. Lateral Cervical Region Table 13. Summary: Cervical Regions/Triangles and Contents Region Main Contents and Underlying Structures Sternocleidomastoid Sternocleidomastoid muscle; superior region (A) part of external jugular vein; greater auricular nerve; transverse cervical nerve Lesser Inferior part of internal jugular vein supraclavicular fossa Figure 22. Muscles of Facial Expression [PPT] (1) A. MUSCLES OF THE SCALP Posterior cervical Trapezius muscle; cutaneous branches NOTE: Refer to Part III-B. Muscles of the Scalp on page 6 region (B) of posterior rami of cervical spinal nerves; suboccipital region or triangle B. MUSCLES OF THE FACE (E) lies deep to superior part of this MUSCLES OF THE EYELIDS region Orbicularis oculi (sphincter) Lateral cervical region (posterior triangle) (C) → Also known as the orbital sphincter → Origin: Medial orbital margin, medial ligament, lacrimal bone Occipital triangle (2) Part of external jugular vein; posterior → Insertion: Skin around margin of the orbit, superior and branches of cervical plexus of nerves; inferior tarsal plates spinal accessory nerve (CN XI); trunks → Consists of 3 parts: of brachial plexus; cervicodorsal trunk; ▪ Orbital part cervical lymph node − Overlies orbital rim and attached to the frontal bone and maxilla medially − Tightly closes the eyelids to protect eyeball against glare Omoclavicular Subclavian artery (third part); part of and dust (subclavian) triangle subclavian vein (sometimes); ▪ Palpebral part (3) suprascapular artery; − Arise from the medial palpebral ligament and are mostly supraclavicular lymph nodes located within the eyelids ANATOMY Head and Neck I PAGE 9 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD − Gently closes the eyelids to keep the cornea from drying → Action: ▪ Lacrimal part ▪ Dilates mouth − Posterior to the lacrimal sac ▪ Elevate labial commissure bilaterally (to smile - happy − Draws the eyelids medially and aids drainage of expression) and unilaterally (to sneer - disdain) tears Zygomaticus minor → When all of the 3 parts of the orbicularis oculi contract, the → Origin: Zygomatic bone, anterior aspect eyes firmly close → Insertion: Skin of upper lip → It protects eyeballs from injury and excessive light → Action: → Closes eyelids and wrinkles forehead vertically ▪ Dilates mouth → Contraction of muscle fibers narrows the palpebral fissure ▪ Retract and evert upper lip → Assists the flow of lacrimal fluid/tears ▪ Deepen nasolabial sulcus Levator palpebrae superioris (dilator) Levator anguli oris → Triangular-shaped muscle located in each upper eyelid → Origin: Infra-orbital margin (canine fossa) → Elevates and retracts the upper eyelid → Insertion: Angle of mouth (modiolus) Occipitofrontalis (dilator) → Action: → Triangular-shaped muscle located in each upper eyelid ▪ Dilates mouth → Elevates and retracts the upper eyelid ▪ Widens oral fissure, as when grinning or grimacing Corrugator supercilii Risorius → Creates vertical wrinkle above the nose → Origin: Parotid fascia and buccal skin → Origin: Medial end of superciliary arch → Insertion: Angle of mouth → Insertion: Skin superior to middle of supra-orbital margin and → Action: superciliary arch ▪ Dilates mouth → Dilators of the eyelids include the levator palpebrae ▪ Depresses labial commissure bilaterally to frown (sadness) superioris and occipitofrontalis muscles Depressor anguli oris → Actions → Origin: Anterolateral base of mandible ▪ Draw eyebrows medially and inferiorly → Insertion: Skin of lower lip ▪ Vertical wrinkles above nose → Action: ▪ Dilates mouth MUSCLES OF THE NOSE ▪ Depresses the labial commissure bilaterally to frown Procerus (with the transverse part of nasalis) (sadness) → Origin: Fascia aponeurosis Depressor labii inferioris → Insertion: Skin of inferior forehead → Origin: Platysma and anterolateral body of mandible → Action: → Insertion: Skin of chin (mentolabial sulcus) ▪ Depresses medial end of eyebrow → Action: ▪ Wrinkles skin of the nose ▪ Dilates mouth Alar part of nasalis (with the levator labii superioris alaeque ▪ Depresses and/or everts lower lip (pouting or sadness nasii) expression) → Origin: Frontal process of maxilla Mentalis → Insertion: Major alar cartilage → Origin: Body of mandible → Action: → Insertion: Skin of chin ▪ Depresses ala laterally → Action: ▪ Dilate anterior nasal aperture (i.e., flare nostrils during ▪ Elevates and protrudes lower lip anger of exertion ▪ Elevates skin of chin (showing doubt) MUSCLES OF THE LIPS Platysma Orbicularis oris → Origin: Skin below the clavicle, upper thorax → Also known as oral sphincter → Insertion: Body of mandible → First sphincter associated with the alimentary system → Action: → Encircles the mouth ▪ Depresses mandible → Controls entry and exit through oral fissures ▪ Tenses skin of inferior face and neck (tension, stress) → Origin: Medial maxilla and mandible; deep surface of perioral MUSCLES OF THE CHEEKS skin; angle of mouth (modiolus) Buccinator → Insertion: Mucous membrane of lips → Thin, flat, rectangular muscle → Action: → Origin: Mandible, alveolar processes of maxilla and mandible, ▪ Tonus: closes oral fissure pterygomandibular raphe ▪ Phasic contraction: compresses and protrudes lips (kissing) → Insertion: Angle of mouth, orbicularis oris or resists distention (when blowing) → Action: MUSCLES OF THE MOUTH AND LIPS ▪ Processes cheek against molar teeth Levator labii superioris alaeque nasii ▪ Works with the tongue to keep food between occlusal → Origin: Frontal processes of the maxilla surfaces and out of the oral vestibule → Insertion: Major alar cartilage → Action: ▪ Depresses ala laterally ▪ Dilate anterior nasal aperture Levator labii superioris → Origin: Infra-orbital margin → Insertion: Skin of upper lip → Action: ▪ Dilates mouth ▪ Retract and evert upper lip ▪ Deepen nasolabial sulcus (sad expression) Zygomaticus major → Origin: Lateral aspect of the zygomatic bone → Insertion: Angle of mouth (modiolus) ANATOMY Head and Neck I PAGE 10 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD → Action: ▪ Bilaterally: protrudes and elevates mandible ▪ Unilaterally and alternately: produces side-to-side movements Temporalis → Origin: Floor of the temporal fossa and deep temporal fascia → Insertion: Coronoid process and ramus of mandible → Action: Elevates the mandible; (posterior fibers retract it) 💬 External/lateral pterygoid Muscle involved in deep mastication → Origin: ▪ Superior head: infratemporal surface of greater wing of sphenoid bone ▪ Inferior head: lateral pterygoid plate → Insertion: Pterygoid fovea, capsule of temporomandibular joint, articular disc → Action: Protracts of the jaw and depresses the mandible 💬 Masseter Origin: Inferior border and medial surface of the maxillary 💬 process of the zygomatic bone and the zygomatic arch Insertion: Angle and lateral surface of the mandible , coronoid [PPT] process and ramus of mandible Figure 23. Muscles Involved in Mastication → Action: Elevates and protrudes the mandible; (deep fibers VII. MANDIBLE retract it) A. PARTS OF THE MANDIBLE Suprahyoid muscles (DGMS) ❗️ → Action: Depresses the mandible These muscles are innervated by the mandibular division of CN V except the following: → Posterior belly of digastric & stylohyoid (innervated by CN VII) ❗️ → Geniohyoid (innervated by C1) Mnemonic: TIMES for grouping according to action → TIM: Elevates the mandible (Temporalis, Internal pterygoid, masseter) → ES: Depresses the mandible (External pterygoid, Suprahyoid) Table 14. Muscles of Mastication Muscle Action Innervation Temporalis Elevates the Mandibular division mandible of CN V (Trigeminal Internal/medial Elevates the nerve/V3) Figure 24. Anterolateral superior view of the mandible[Netter] Main parts of the mandible: 💬 pterygoid Muscle of deep mastication mandible → Ascending ramus Masseter Elevates the → Body mandible ❗️ → Mentum External/lateral Depresses the 💬 Important fossa in the mandible: pterygoid mandible; protracts → Mental foramen: located in the body of the mandible Muscle of deep the jaw → Mandibular foramen mastication → Lingula Suprahyoid Depresses the Mandibular division Coronoid process: located anteriorly muscles (DGMS) mandible of CN V (Trigeminal Condylar process: located posteriorly nerve/ V3) except: → Posterior The temporomandibular joint connects the mandible to the skull belly of and is formed by the following structures: digastric & → Coronoid process stylohyoid → Condylar process (innervated → Head of the mandible by CN VII) → Mandibular notch → Geniohyoid (innervated B. MUSCLES OF MASTICATION by C1) 💬 Internal/medial pterygoid Muscle involved in deep mastication → Origin: Medial surface of lateral plate of pterygoid, pyramidal process of palatine bone, maxillary tuberosity → Insertion: Medial surface of ramus and angle of mandible inferior to mandibular foramen ANATOMY Head and Neck I PAGE 11 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD Figure 28. Movements of the temporomandibular joint. [Moore] Figure 29. Temporomandibular joint in closed and open mouth positions. [Moore] IX. SUPRAHYOID AND INFRAHYOID MUSCLES Figure 25. Actions of the muscles involved in mastication[Lecturer’s PPT] Figure 30. The suprahyoid and infrahyoid muscles[Netter] 💬 A. SUPRAHYOID MUSCLE GROUP Figure 26. Superficial muscles of mastication[Netter] 💬 Muscle group found superior to the hyoid bone Action: Depresses mandible against resistance when infrahyoid muscles fix or depress hyoid bone Table 15. Suprahyoid muscles Muscle Action Innervation Mylohyoid Elevates the hyoid Nerve to muscle bone, floor of the mylohyoid, a mouth and the branch of inferior tongue during alveolar nerve swallowing and (from mandibular speaking nerve, CNV3) Geniohyoid Pulls the hyoid C1 via the 💬 muscle attached to the body of the hyoid anterosuperiorly Shortens the floor of the mouth and hypoglossal nerve (CN XII) bone & the widens the Figure 27. Deep muscles of mastication[Netter] mentum pharynx 💬 Modified hinge VIII. TEMPOROMANDIBULAR JOINT Stylohyoid Elevates and Stylohyoid branch muscle retracts the hyoid of the facial nerve 📖 Actions: gliding (protrusion, retrusion), small degree of rotation type of synovial joint (CN VII) (pivoting), flexion (elevation), and extension (depression) Digastric muscle Depresses the Anterior belly - mandible Mylohyoid bone Elevates the hyoid Posterior belly - bone Branch of the facial nerve (CN VII) ANATOMY Head and Neck I PAGE 12 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD Figure 31. Lateral, slightly inferior view of the floor of the mouth-musculature [Netter] Figure 34. Schematic diagram of the infrahyoid and suprahyoid muscles and their actions [Netter] X. SALIVARY GLANDS Figure 32. Posterosuperior view of the floor of the mouth-musculature [Netter] Figure 35. Salivary Glands[Lecturer’s PPT] A. PAROTID GLAND Figure 33. Anteroinferior view of the floor of the mouth-musculature [Netter] 💬 B. INFRAHYOID MUSCLE GROUP 💬 Muscle group found inferior to the hyoid bone Action: Fix or depress the hyoid bone Table 16. Infrahyoid muscles Muscle Action Innervation Sternohyoid Depresses the hyoid C1-C3 by a branch bone after elevation of Ansa cervicalis during swallowing from the cervical Omohyoid Depresses and plexus → Inferior retracts the hyoid Figure 36. Parotid Gland[Netter] belly Largest salivary gland which is composed mostly of serous acini → Superior It lies in the deep hollow below the external auditory canal/meatus belly behind the ramus of the mandible and in front of the Sternothyroid Depresses the hyoid Thyrohyoid and the larynx Depresses the hyoid C1 via hypoglossal ❗️ sternocleidomastoid muscle Facial Nerve → Divides the gland into superficial and deep lobes and elevates the nerve (CN XII) → Divided into 5 within the gland: larynx ▪ Temporal branch ▪ Cervical branch ▪ Zygomatic branch of facial nerve ▪ Buccal nerve ▪ Submandibular nerve ANATOMY Head and Neck I PAGE 13 of 14 ANATOMY | LE 1 Head and Neck I | Alexandria R. Bayaoa, MD Parotid Duct (Stensen’s Duct) b. Alar → Emerges from the anterior border of the gland and passes c. Buccopharyngeal forward over the lateral surface of the masseter d. Prevertebral → It enters the vestibule of the mouth upon a small papilla 7. The triangle of the neck can the Vagus nerve (CN X) be 💬 opposite the upper 2nd molar tooth Nerve supply: Parasympathetic secretory motor supply which arises from the glossopharyngeal nerve (CN IX) located? a. Carotid b. Submental c. Submandibular B. SUBMANDIBULAR GLAND d. Muscular 8. Which muscle of facial expression depresses the labial commissary bilaterally to frown? a. Levator anguli oris b. Zygomaticus major c. Zygomaticua minor d. Depressor anguli oris 9. Which muscle of mastication protracts the mandible? a. Medial pterygoid b. Lateral pterygoid c. Temporalis d. Masseter 10. The parotid gland is bisected into a superficial and deep lobe by what structure? a. Common carotid artery 💬Figure 37. Cadaveric Image of Submandibular Gland [Lecturer’s PPT] b. Zygomaticus major Located in the digastric triangle c. Facial vein d. Facial nerve C. SUBLINGUAL GLAND 11. What is the motor innervation of the suprahyoid muscle? a. Ansa cervicalis b. Recurrent laryngeal c. Glossopharyngeal d. Facial ANS: 1. B. Lacrimal. The rest are skull bones, while lacrimal is the only facial bone. 2. B. Posterior. The spinal accessory nerve exits via the foramen magnum, a part of the posterior cranial fossa. 3. C. Loose connective tissue. 4. C. Pretracheal. Superficial (facial muscles & Platysma; vessels and nodes); Investing (sternocleidomastoid & trapezius; anterior and posterior triangle of the neck); Pretracheal (Infrahyoid, hyoid, thyroid; blends with the fibrous pericardium), Prevertebral (prevertebral ms.; fascial floor of posterior 💬 Located at the Figure [Netter] 38. Sublingual Gland triangle & axillary sheath) floor of the mouth 5. D. Prevertebral. 6. A. Investing and D. Prevertebral. Carotid sheath is the condensation of XI. REVIEW QUESTIONS the three layers of the deep cervical fascia- prevertebral, paratracheal, and 1. Which of the following is a facial bone? investing layers. 7. A. Carotid. Carotid sheath components include common carotid a. and its a. Ethmoid branches; internal jugular vein and its tributaries; vagus nerve; external b. Lacrimal carotid a. and some of its branches; hypoglossal n. (CN XII) and superior c. Parietal root of ansa cervicalis; spinal accessory n. (CN XI); thyroid gland, larynx, d. Temporal and pharynx; deep cervical lymph nodes; and branches of cervical plexus. 2. From which group of cranial fossa does the spinal 8. D. Depressor anguli oris. accessory nerve exits 9. B. Lateral pterygoid. It depresses the mandible and protracts the jaw. a. Anterior 10. D. Facial nerve. 11. D Facial nerve. The facial nerve (CN VII) is the motor innervation for all the b. Posterior suprahyoid muscles, except the anterior belly of the digastric (trigeminal n. / c. Middle CN V) and the geniohyoid (C1 via hypoglossal n./ CN XII) 3. Which layer in the scalp communicates with intracranial venous sinuses? XII. REFERENCES a. Skin Bayaoa, A. (2023). Head and Neck I (Asynchronous Lecture) b. Aponeurosis Moore, K., Dalley, A., & Agur, A. (2018). Clinically Oriented Anatomy (8th ed.). Wolters Kluwer Health. c. Loose connective tissue Netter, F.H. (2019). Atlas of Human Anatomy (7th ed.) Elsevier d. Connective tissue 2025 Transcription. (2021). Head and Neck I. [Transcription] 4. Which fasciae layer in the neck encloses the thyroid gland? Bregman, R.A., & Afifi, A.K. (n.d.). Plate 9:Muscles of the face and neck. a. Investing Anatomy Atlases b. Superficial c. Pretracheal d. Prevertebral 5. The danger space from the skull base to the mediastinum where abscess can spread from the neck is limited by which fascia? Netter’s Anatomy Dissection (2017). 1.2 Step 6. Infrahyoid and digastric a. Investing muscles; submandibular gland.Youtube. b. Superficial c. Pretracheal d. Prevertebral 6. The carotid sheath is a condensation of which fascial layer? a. Investing ANATOMY Head and Neck I PAGE 14 of 14