Gross U 4

DAY 14 – NECK

Platysma

• Thin, superficial muscle of facial expression in the neck

• Tenses skin of the neck, depresses mandible

• Innervation: Facial nerve (CN VII)

Muscle dividing anterior/posterior neck triangles:

• Sternocleidomastoid (SCM)

  • Origin: Sternum and clavicle

  • Insertion: Mastoid process

  • Action (unilateral): Turns head to opposite side

  • Action (bilateral): Neck flexion (e.g., looking down)

I. Posterior Triangle (pp. 1008–1016)

Scalene muscles

• Anterior & middle scalenes attach to 1st rib; posterior to 2nd rib

• Action: Elevate ribs during inspiration; lateral neck flexion

• Brachial plexus and subclavian artery pass between anterior and middle scalenes

Suprascapular nerve

• Innervates supraspinatus and infraspinatus muscles

Phrenic nerve

• Motor to diaphragm

• Descends anterior to anterior scalene

II. Anterior Triangle (pp. 1018–1024)

Boundaries:

• Anterior: Midline of neck

• Posterior: SCM

• Superior: Mandible

A. Suprahyoid vs. Infrahyoid Muscles

General action:

• Stabilize/elevate or depress hyoid bone during swallowing and speaking

Suprahyoid muscles:

• Mylohyoid: Floor of mouth; elevates hyoid

• Digastric: Two bellies; anterior (V3) and posterior (VII)

Infrahyoid muscles:

• Sternohyoid, omohyoid, sternothyroid, thyrohyoid

• Depress hyoid/larynx

B. Blood Vessels

Internal jugular vein

• Drains brain, face, and neck

• Joins subclavian vein → Brachiocephalic vein

Common carotid artery

• Divides into:

  • Internal carotid a. (brain, eye)

  • External carotid a. (face, scalp)

Carotid sheath contents:

• Common/internal carotid a., internal jugular v., vagus nerve (CN X)

External carotid branches:

• Superior thyroid: Thyroid gland, larynx

• Lingual: Tongue

• Facial: Face

• Terminal branches: Maxillary and superficial temporal arteries

III. Cranial Nerves in the Neck

Vagus nerve (CN X)

• Motor: Pharynx, larynx, soft palate

• Sensory: Larynx, thoracic and abdominal viscera

• Recurrent laryngeal nerve branches near subclavian a. (right) or aortic arch (left)

Hypoglossal nerve (CN XII)

• Motor to intrinsic and extrinsic tongue muscles (except palatoglossus)

• Passes lateral to external carotid artery, then crosses over to the tongue muscles

DAY 15 – FACE

I. Bones of the Face (pp. 840–845)

1. Facial bones:

• Paired: Maxillae, zygomatic, nasal, lacrimal, palatine, inferior nasal conchae

• Unpaired: Mandible, vomer

2. Foramina:

• Frontal bone → Supraorbital foramen

• Maxilla → Infraorbital foramen

• Mandible → Mental foramen

3. Where are the conchae located?

• Inside the lateral walls of the nasal cavity

• Superior and middle conchae are part of the ethmoid bone; inferior concha is a separate bone

4. Alveolar processes:

• Ridges in the maxilla and mandible that house the sockets (alveoli) for the teeth

5. Zygomatic arch is formed by:

• Temporal process of the zygomatic bone

• Zygomatic process of the temporal bone

6. Why is pterion fracture dangerous?

• Overlies the middle meningeal artery

• Fracture can cause epidural hematoma and rapid brain compression

7. External acoustic opening and styloid process are part of:

• Temporal bone

II. Trigeminal Nerve (CN V) (pp. 867–871)

Three divisions:

• V1 (Ophthalmic) – sensory

• V2 (Maxillary) – sensory

• V3 (Mandibular) – sensory and motor

A. V1 – Ophthalmic Branch

• Frontal n.

  • Supratrochlear n.

  • Supraorbital n. → passes through supraorbital foramen

• Lacrimal n. – lateral upper eyelid

• Nasociliary n. – cornea, nasal mucosa, ethmoid air cells

B. V2 – Maxillary Branch

• Superior alveolar nerves – innervate upper teeth

• Infraorbital n. – emerges through infraorbital foramen

• Palatine branches – hard and soft palate

C. V3 – Mandibular Branch

• Motor: Muscles of mastication

  • Masseter, temporalis, medial/lateral pterygoids

  • Also: anterior belly of digastric, mylohyoid, tensor tympani, tensor veli palatini

• Sensory branches:

  • Inferior alveolar n. → mandibular teeth

    • Mental n.: through mental foramen

  • Lingual n. → anterior 2/3 of tongue (general sensation)

III. Facial Nerve (CN VII) (pp. 871–873)

Motor (muscles of facial expression):

• Facial muscles insert into skin and other muscles — not bones.

• Pass through the parotid gland, but do not innervate it.

Sensory:

• Taste from anterior 2/3 of tongue (via chorda tympani, joins lingual n.)

Parasympathetic (glands):

• Lacrimal, submandibular, sublingual glands

IV. Other Structures

A. Parotid Gland

• Secretes: Serous (enzyme-rich) saliva

• Duct enters: Opposite 2nd maxillary molar

• Innervation: Parasympathetics from Glossopharyngeal (CN IX) via otic ganglion

B. Nasal Cartilages

• Alar cartilage: Surrounds nostril

• Lateral nasal cartilage: Lateral support

• Septal cartilage: Midline division of nostrils

DAY 16/17 – SKULL, BRAIN, AND EYE

Bone Review (pp. 845–855)

What bone contains the foramen magnum?

• Occipital bone

What passes through the foramen magnum?

• Medulla oblongata

• Vertebral arteries

• Spinal accessory nerve (CN XI, spinal root)

• Meninges

Crista galli and cribriform plate

• Crista galli: Vertical midline projection of the ethmoid bone; serves as an attachment point for the falx cerebri.

• Cribriform plate: Horizontal portion of the ethmoid bone with tiny foramina.

• What passes through it?: Olfactory nerve axons (CN I)

What bone contains the hypophyseal fossa (sella turcica)?

• Sphenoid bone

What resides here?

• Pituitary gland

Fontanels in infants (pp. 858–859)

• Membranous gaps between cranial bones allowing deformation during birth and brain growth postnatally.

• Close progressively in early childhood; largest is the anterior fontanel (closes ~18 months).

I. Brain

Label:

• Cerebral hemispheres

• Cerebellum

• Brainstem: Midbrain, Pons, Medulla

• Corpus callosum

• Thalamus

• Hypothalamus

A. Features of Cerebral Hemispheres

Definitions:

• Gyrus: Elevated ridge of brain tissue

• Sulcus: Shallow groove between gyri

• Fissure: Deep groove (e.g., longitudinal fissure)

Key Sulci/Fissures:

• Central sulcus: Frontal vs. parietal lobes

• Lateral sulcus: Temporal vs. frontal/parietal

• Longitudinal fissure: Divides left/right hemispheres

Lobes and Functions:

• Frontal: Motor function, executive function, speech (Broca's), behavior

• Parietal: Somatosensation, spatial processing

• Temporal: Hearing, memory, speech (Wernicke's)

• Occipital: Vision

B. Ventricles & CSF

• Choroid plexus: Produces CSF

• Functions of CSF:

  1. Cushions brain (mechanical protection)

  2. Removes waste, circulates nutrients

Path of CSF flow:

• Lateral ventricles → interventricular foramina → third ventricle → cerebral aqueduct → fourth ventricle → median & lateral apertures → subarachnoid space → absorbed by arachnoid granulations into dural venous sinuses

Where does CSF exit 4th ventricle?

• Via median aperture (foramen of Magendie) and lateral apertures (foramina of Luschka)

• Drains into: Subarachnoid space

Hydrocephalus (p. 904):

• Excess CSF accumulation due to obstruction, overproduction, or impaired absorption; leads to increased intracranial pressure.

C. Meninges

1. Dura mater

   • Outer tough layer

   • Forms cerebral falx (between hemispheres) and tentorium cerebelli (above cerebellum)

2. Arachnoid mater

   • Middle layer

   • Subarachnoid space beneath contains CSF and blood vessels

3. Pia mater

   • Thin, vascular layer adhering directly to brain surface

Hematomas:

• Epidural hematoma

  • Arterial (e.g., middle meningeal artery)

  • Between skull and dura

  • Rapid onset (hours)

  • Convex/lens shape on imaging

• Subdural hematoma

  • Venous (bridging veins)

  • Between dura and arachnoid

  • Slow onset (days–weeks)

  • Crescent shape on imaging

D. Blood Supply of the Brain

1. Vertebral System

• Vertebral arteries → Basilar artery → Posterior cerebral arteries

• Supplies: Brainstem, cerebellum, posterior cerebrum

2. Internal Carotid System

• Internal carotid → Anterior cerebral artery & Middle cerebral artery

  • ACA: Medial frontal/parietal lobes

  • MCA: Lateral hemispheres (motor, sensory, language areas)

3. Circle of Willis

• Arterial anastomosis connecting vertebrobasilar and carotid systems

• Includes: Anterior cerebral, anterior communicating, internal carotid, posterior cerebral, and posterior communicating arteries

• Clinical importance: Site of aneurysms and collateral circulation

II. The Eye

A. Bones of the Orbit (pp. 907–909)

• Frontal, Zygomatic, Maxilla, Sphenoid, Ethmoid, Lacrimal

• Why is the medial wall thin?

  • Formed by ethmoid and lacrimal bones — extremely thin (lamina papyracea); easily fractured (orbital blowout fractures)

B. Lacrimal Apparatus (pp. 899–902)

• Lacrimal gland: Produces tears

• Lacrimal canaliculi (puncta): Drain tears into lacrimal sac

• Lacrimal sac → Nasolacrimal duct → Inferior nasal meatus

Innervation for tear production:

• Parasympathetic fibers from Facial nerve (CN VII) via greater petrosal nerve

• Fibers join the lacrimal nerve (branch of V1)

C. Structures of the Eye

• Sclera: Fibrous outer layer; provides shape and protection

• Cornea: Transparent anterior surface; refracts light

• Ciliary body: Produces aqueous humor; controls lens shape via zonules

• Suspensory ligaments: Connect ciliary body to lens

• Iris: Controls pupil size (light entry)

• Lens: Focuses light onto retina; shape controlled by ciliary muscles

• Vitreous body: Gel filling posterior cavity; supports retina

D. Extraocular Muscles and Nerves

• 
  Remember the SO4, LR6, rest 3 rule for cranial nerve innervation.

DAY 19 – ORAL CAVITY AND LARYNX

I. Oral Cavity

Lips and Cheeks (pp. 946–947)

1. Labial frenula:
   Midline mucosal folds that connect the inner surface of each lip to the gingiva (gums); one superior and one inferior.

2. Buccal fat pad (in infants):
   Provides insulation and assists with sucking by giving rigidity to the cheeks.

A. Hard and Soft Palate (pp. 952–955)

1. Hard palate bones & innervation:

   • Formed by the palatine processes of the maxilla (anteriorly) and the horizontal plates of the palatine bones (posteriorly).

   • Innervation: Greater palatine and nasopalatine nerves (branches of V2 - maxillary division of trigeminal nerve).

   • Foramina: Greater and lesser palatine foramina; incisive foramen.

2. Why elevate the soft palate during swallowing?

   • To close off the nasopharynx, preventing food from entering the nasal cavity.

Muscles of the soft palate and their innervation:

• Tensor veli palatini: Tenses the soft palate; opens pharyngotympanic tube.

  • Innervation: Mandibular nerve (V3)

• Levator veli palatini: Elevates the soft palate.

  • Innervation: Vagus (CN X)

• Palatoglossus: Elevates posterior tongue; depresses soft palate.

  • Innervation: Vagus (CN X)

• Palatopharyngeus: Tenses soft palate and pulls pharyngeal wall superiorly.

  • Innervation: Vagus (CN X)

3. Between palatoglossal and palatopharyngeal arches:

   • Palatine tonsils

   • Muscles deep to arches: palatoglossus and palatopharyngeus respectively.

B. Tongue (pp. 955–959)

1. Lingual papillae:

   • Specialized mucosal structures with taste buds (except filiform).

   • Types: Filiform (no taste buds), Fungiform, Circumvallate, and Foliate.

   • Lingual tonsil: Lymphoid tissue on posterior third of the tongue.

2. Intrinsic vs. Extrinsic muscles:

   • Intrinsic: Change shape of the tongue (curling, flattening).

   • Extrinsic: Move the tongue.

     • Genioglossus: Protrudes and depresses tongue.

     • Hyoglossus: Depresses and retracts tongue.

     • Innervation: Hypoglossal nerve (CN XII)

• Geniohyoid:

  • Located superior to mylohyoid, deep to digastric.

  • Elevates hyoid and draws it forward; assists with swallowing.

  • Innervation: C1 via hypoglossal nerve (CN XII)

3. Innervation of the tongue:

   • Facial nerve (VII): Taste to anterior 2/3 (via chorda tympani + lingual nerve).

   • Glossopharyngeal (IX): General & special sensation to posterior 1/3.

   • Hypoglossal (XII): Motor to all intrinsic & extrinsic muscles (except palatoglossus).

   • Vagus (X): Minor taste/general sensation to root of tongue & epiglottic region.

C. Glossopharyngeal nerve (CN IX)

• Sensory: Posterior 1/3 tongue (taste & somatic), pharynx, carotid sinus/body.

• Motor: Stylopharyngeus muscle

• Parasympathetic: Parotid gland via otic ganglion

D. Salivary Glands

1. Three pairs:

   • Parotid (largest; serous)

   • Submandibular (mixed)

   • Sublingual (mostly mucous)

2. Relationship of submandibular duct to lingual nerve:

   • Duct loops around lingual nerve: initially lateral, then inferior, then medial.

3. Openings:

   • Submandibular duct: Opens at the sublingual caruncle beside the frenulum.

   • Sublingual gland: Opens via multiple ducts along the sublingual fold.

II. Larynx (pp. 1040–1049)

A. Functions of the larynx:

• Phonation (voice)

• Protection of airway during swallowing

• Air passage between pharynx and trachea

• Valsalva maneuver (e.g., lifting, defecation)

Action during swallowing:

• Larynx elevates and epiglottis folds posteriorly to cover the laryngeal inlet.

B. Cartilages of the Larynx

• Epiglottis: Leaf-shaped elastic cartilage that covers the laryngeal inlet.

• Thyroid cartilage: Largest, anterior prominence (Adam’s apple), no posterior wall.

• Cricoid cartilage: Only complete ring of cartilage in airway; thicker posteriorly.

• Arytenoid cartilages: Pyramid-shaped, mobile, attach to vocal folds.

Unique feature of cricoid cartilage:

• Only complete cartilaginous ring in the respiratory tract.

C. Internal Structures

1. Vocal folds vs. vocal ligaments:

   • Vocal folds (true vocal cords): Mucosa-covered ligaments; involved in phonation.

   • Vocal ligaments: Elastic tissue within the folds; attach to thyroid and arytenoid cartilages.

Cartilage attachments for vocal ligaments:

• Anterior: Inner surface of the thyroid cartilage

• Posterior: Vocal process of the arytenoid cartilage

Control of vocal ligament tension:

• Via intrinsic laryngeal muscles, altering position of arytenoid cartilages.

• Innervation: Recurrent laryngeal nerve (branch of Vagus CN X)

Rima glottidis:

• Space between the vocal folds; narrowest part of airway.

• Opens during inspiration, closes during swallowing and phonation.

2. Vestibular folds (false vocal cords):

• Superior to true vocal cords

• Do not contribute to phonation

• Function in airway protection

DAY 18 – NASAL CAVITY AND PHARYNX

I. Nasal Cavity (pp. 973–982)

A. Bones of the Nasal Cavity
1. Lateral Walls:

• Superior and middle nasal conchae (part of the ethmoid bone)

• Inferior nasal concha (a separate bone)

• Perpendicular plate of the palatine bone

• Medial surface of the maxilla

• Lacrimal bone

2. Floor:

• Palatine process of the maxilla

• Horizontal plate of the palatine bone

3. Roof:

• Nasal bone

• Frontal bone

• Cribriform plate of the ethmoid

• Sphenoid bone

4. Septum:

• Perpendicular plate of ethmoid (superior part)

• Vomer (inferior part)

• Septal cartilage (anterior)

B. Nasal Septum and Conchae

Three components of the nasal septum:

1. Perpendicular plate of ethmoid

2. Vomer

3. Septal cartilage

Conchae & Meatuses:

• Superior nasal concha (ethmoid) → superior meatus

• Middle nasal concha (ethmoid) → middle meatus

• Inferior nasal concha (own bone) → inferior meatus

Which is an individual bone? Inferior nasal concha
What bone are the other two part of? Ethmoid

Purpose of the conchae:
To increase surface area and turbulence to warm, humidify, and filter inspired air, and to direct airflow toward the olfactory epithelium.

C. Sinuses – 4 paired, air-filled chambers
Label the sinuses:

• Frontal

• Ethmoid air cells

• Sphenoid

• Maxillary

Function:

• Lighten skull

• Produce mucus to trap debris

• Voice resonance

• Humidify air

Most often infected: Maxillary sinus
Why? Because their drainage opening is high on the medial wall, above the sinus floor, making gravity drainage poor.

Drainage locations:

• Sphenoid sinus → sphenoethmoidal recess

• Ethmoid air cells → superior and middle meatus

• Frontal sinus → middle meatus via frontonasal duct

• Maxillary sinus → middle meatus

• Nasolacrimal duct → inferior meatus

D. Olfactory nerve (CN I)
Function: Smell
Cell bodies: In olfactory epithelium of the nasal cavity

Pass through: Cribriform plate of ethmoid bone
Terminate in: Olfactory bulb (anterior cranial fossa)

II. Pharynx (pp. 1051–1057)

Three regions (from superior to inferior):

1. Nasopharynx

2. Oropharynx

3. Laryngopharynx

A. Nasopharynx

• Pharyngotympanic (auditory) tube:

  • Other end is in the middle ear

  • Function: Equalizes air pressure between the nasopharynx and middle ear

• Pharyngeal tonsil (adenoid):

  • Located in the roof of the nasopharynx; part of immune defense

B. Oropharynx

• Palatine tonsils: Located between two folds

  • Anterior fold: Palatoglossal arch

  • Posterior fold: Palatopharyngeal arch

C. Laryngopharynx

• Epiglottis function:

  • Folds over laryngeal inlet during swallowing to prevent food/liquid from entering airway

D. Pharyngeal constrictors

• Muscles: Superior, middle, and inferior constrictors

• Function: Sequential contraction to propel bolus toward the esophagus (peristalsis)

• Innervated by: Vagus nerve (CN X)