(4) Skull / (5) Jaws & Teeth / (6) Chewing & Swallowing

How many bones are there in the skull and what regions and what regions can it be divided into?

• 22 bones in adult cranium

• 6 bones of middle ear and mandible

• Neurocranium is the region of the skull protecting the brain

• Viscerocranium is the region that forms the face

Describe the neurocranium

• forms the shape of the head

• protects the brain

• protects the organs controlling the 5 senses

• allows neurovascular passage between intracranial and extracranial anatomy

Describe the viscerocranium

• forms the shape of the face

• forms the cavities of the anterior skull (orbit, oral, and nasal cavities)

• protects the delicate structures of the cavities

• protects the neurovascular structures of the face

• provide surface attachments for the facial muscles

• bones here tend to be smaller and more delicate

What are the 2 sets of paired bones in the neurocranium?

The parietal and temporal bones

slide 6 picture label the 6

What is the dorsal (top) part of the skull called?

Calvarium

What is the ventral (bottom) part of the skull called?

Cranial base

slide 8, label 8

a. nasal

b. lacrimal

c. inferior nasal concha

d. maxilla

e. mandible

f. palatine

g. zygomatic

h. vomer

At birth how many bones is the skull comprised of?

45

What are cranial sutures?

• Bony articulations that exist between bones of the skull

• Bones almost connect with each other, separated by fibrous tissue compromised mainly of cartilage

• Starts as a series of ossification centers around a fetus brain → allow for rapid growth

• Brain growth slows and the ossification centers become sutures which fuse together mostly during adulthood and can be obliterated with age

What are the 4 major cranial sutures and what do they seperate/connect?

• Sagittal: middle part, separates 2 parietal bones and joins frontal bone and occipital bone

• Coronal: crown, over the top. separates forehead from everything else. connects frontal bone and two parietals

• Squamous: “squashed” on the side of the head

• Lambdoid: “last”, back of the skull

What is the order of obliteration of cranial sutures, first to last?

Sagittal first, followed by coronal, then lambdoid

What is the metopic suture and metopism?

• Metopic suture divides the frontal bone in infants

• It fuses between 3 and 9 months and usually obliterated by age 7

• Occasionally the suture line remains in adulthood which is known as metopism, this is found in about ~6% of the population

What does fossa mean?

Pit, cavity, depression

Anterior cranial fossa

• compromised of the frontal bone, ethmoid bone, and sphenoid bone

• accommodates frontal lobe

• shallowest of the cranial fossa

• has the ethmoid bone

  • the cribriform plate of the ethmoid bone allows the transmission of the olfactory fibers

Middle cranial fossa

• comprised of sphenoid bone and two temporal bones

• accommodates the pituitary gland and the temporal lobes

• the pituitary gland sits in a depression in the sphenoid bone known as sella turcica

Posterior cranial fossa

• comprised of the occipital and two temporal bones

• accommodates the brain stem and cerebellum

• the deepest of the cranial fossa

Temporal fossa

• a shallow depression on the temporal region of the skull

• forms one of the largest landmarks of the skull

• comprised of the parietal, temporal, frontal, and sphenoid bones

• mainly occupied by the temporalis muscle

Define foramen and fissure and state their role

• foramen: an opening, hole, or passage usually through a bone

• fissure: a slit like groove

• they transmit major nerves and blood vessels

Major foramina

• supraoribital foramen: located in the frontal bone, it allows passage of the supraorbital vein, artery, and nerve in orbit

• optic foramen: located in sphenoid, it allows the passage of the ophthalmic artery and nerve from the optic canal into the orbit

• foramen magnum: located in the occipital bone, it allows the passage of the spinal and vertebral arteries and the spinal cord to pass from the skill into the orbit

• foramen magnum: located in the occipital bone, it allows passage of ophthalmic artery and nerve from the optic canal into the orbit

• foramina of cribriform plate: located in the ethmoid bone, allows the passage of the olfactory nerve

• foramen rotundum: located in the sphenoid bone, it allows the passage of the maxillary nerve

• internal acoustic meatus: located in the temporal bone, allows passage of vestibulocochlear and facial nerves

Superior and inferior orbital fissures

Superior:

• located in the sphenoid bone, transmits many nerves including the oculomotor and nasociliary nerves, as well as superior ophthalmic vein

Inferior

• transmits the zygomatic branch of maxillary nerve, the inferior ophthalmic vein, sympathetic nerves

Non-metric traits of the skull

• cannot be measured- either there or not

• not considered pathological although their existence may impact upon anatomical function

• examples are additional facets, foramina, and facets such as supraorbital notches, zygomaticofacial foramen, and wormian bones

Biparietal thinning of the skull

• aka biparietal osteodystrophy

• parietals can eventually become so thin that holes appear

• incidence increases with age

• may be related to osteoperoisis

• affects females more

• the dipole (spongy inner bone) thins, followed eventually by the cortical (outer) bone

Craniosynostosis

• birth defect where bones in a baby’s skull fuse together too early

• if this happens before brain is fully developed it ca slow the growth of the brain, compress it

• severity is variable but it can result in blindness, seizures, or brain damage

• genetic in origin

• causes early death but modern day interventions can stop this

Hydrocephaly

• excess buildup of CSF in cavities (ventricles) deep within the brain

• can cause an increase in the size of the neurocranium (macrocephaly)

• viscerocranium usually unaffected

• can be present at birth (congenital) or the result of injury/illness

What are some of the most vulnerable parts of the brain?

• the middle cranial fossa is the most vulnerable part of the skull as the bones are thin and there are multiple foramina → more likely to die from these injured

• the oribital roof and nasal bones are also vulnerable → risk of infection entering brain

Describe the upper jaw

• part of the viscero-craniumn

• known as the maxilla

• comprised of 2 bones

• together with the 2 palatine bones, forms the hard palate

• holds and supports the upper teeth

• helps shape middle of the face

• shapes the floor of nasal cavity, allowing normal airflow

Describe the mandible

• part of viscero-cranium

• single u-shaped bone

• largest bone in skull

• insertion point for many of the muscles involved with facial expression

• holds and supports the lower teeth

• shapes and contours lower 3rd of the face

• holds tongue

hard palate slide 7

a. sphenoid bone

b. transverse palatine suture

c. median palatine suture

d. primary hard palate

e. alveolus

f. incisive fossa

g. palatine process of maxilla

h. palatine bone

i. secondary hard palate

j. pyramidal process of palatine bones

k. vomer bone

What does the primary palate of the jaw refer to

• lips

• nasal sill

• alveolus

• hard palate anterior to the incisive foramen

What does the secondary palate of the jaw refer to

• hard palate posterior to the incisive foramen and soft palate

What is the incisive fossa (aka incisive foramen) ?

Opening for the 2 incisive canals that run either side of the maxilla. They connect the hard palate to the nasal cavity. Carriers branches of the nasopalatine nerve and the terminal ends of the greater palatine vessels

Mandibular features slide 8

a. oblique line

b. coronoid process

c. mandibular notch

d. mandibular condyle

e. condylar neck

f. ramus

g. masseteric fossa

h. masseteric tuberosity

i. gonial angle

j. body

k. mental protuberance

l. mental foramen

Mental foramen

Part of mandibular canal. Carries the inferior alveolar nerve and the mental vessels. These enter through the mandibular foramen on the medial aspect of the mandible

Masseteric fossa and tuberosity

Attachment points for the masseter muscle

Gonial angle and mental protuberance

Important for facial symmetry

Slide 9 Mandibular featyures

a. condylar neck

b. lingula

c. coronoid process

d. endocoronoid ridge

e. mental spines

f. body

g. extramolar sulcus

h. mandibular notch

i. mandibular condyle

Mental spines

attachments for the intrinsic tongue muscles

Mandibular notch

allows for the passage of the masseteric nerves and vessels

Mandibular condyle

vital to functioning of TMJ

Temporomandibular joint (TMJ)

• consists of articulations between 3 surfaces: head of mandible (mandibular condyle) and the articular tubercle and the mandibular fossa in the temporal bone

• unique mechanism as surfaces never actually touch each other, being separated by a disc

• movement:

  • produced by muscles of mastication, and hyoid muscles

  • allow for protrusion and retraction, elevation and depression

What features of the mandible are s*xually dimorphic?

The gonial angle, projection of the mental protuberance, and the extent of the gonial eversion

Anatomical functions of the teeth

Digestion (chewing, swallowing)

• only part of the skeleton that interacts directly with the environment

• they seize and masticate (chew) food

• incisors bite food into smaller pieces

• canines grasp food and tear it off

• premolars and molars chop/crush these pieces further before swallowing

• breaking down food into smaller bolus is important for digestion

Speech

• make words by controlling airflow out of the mouth

• (th → tongue brushes against upper row of teeth)

• (f / v → pressing lower lip to upper teeth)

Facial structure

• help maintain natural alignment of jawbone and facial muscles

Dentition of teeth

• formed deep within jaw

• erupt through gum tissue once nearly complete

• do not change with age

• shape of tooth is only altered by attrition, breakage, cultural mods, or demineralization

• enamel is outer layer of tooth and the hardest tissue in the human body

Adult teeth classifications

8 incisors (thin cutting edges)

4 canines (single prominent cones)

8 premolars (bicuspids)

12 molars (tricuspid or more)

32 total

Deciduous (children) teeth classifications

8 incisors

4 canines

8 molars

20 in total

Dental eruption

• 3rd molars usually erupt ~17-25 years

• lower M3s usually erupt slightly earlier

• eruption often begins earlier in females

• by ~ age 25 you cannot use dental eruption to age a skeleton

Malocclusion and its 2 most severe forms

• misalignment of the teeth

• difference between size of upper and lower jaw or between jaw and tooth size

• usually inherited but can be from trauma, tumors, poor dental habits, childhood habits

most severe forms:

• retrognathism (overbite) → used to be called prognasis

• prognathism (underbite)

Cleft palate

• developmental defect in hard palate

• caused by arrested development of the maxilla during embryogenesis

• results in communication between oral and nasal cavities

• can cause hearing problems (bc of infections), issues with dental development, and speech problems

• causes unclear

Mandibular tori

Bony growths on the lingual surface of the mandible , also known as protrusion or a hyperostosis

Torus palatinus

bony growth midline on the hard palate

Non-metric dental traits (NMDTs)

• carabelli’s cusps

• shove-shaped teeth

• peg-shaped teeth

• additional grooves, ridges, and roots

• supernumerary teeth

• congenital absence of teeth

Plaque and caries

plaque

• soft, thin film of bacteria, mucin, dead epithelial cells, and food debris that develops on tooth surface

• eventually soft plaque mineralizes to become calculus (hard plaque or tartar)

caries

• caused by acids produced by bacteria in plaque. damages the enamel of the tooth eventually causing a pit of cavity

• if left caries can lead to pain, infection, and tooth loss

Periodntal disease

• gum disease

• causes inflammation of tissues surrounding the teeth

• bacteria break down the tissues surrounding the teeth faster than the body can replace them

• in advanced stages can lead to abscesses and tooth loss

Dental abscesses

• caused by a buildup of pus in the gum or tooth

• can spread to the surrounding bone and to other areas of the body through the blood stream

• if untreated can lead to sepsis

Causes of dental wear

• erosion

  • acids from foods

  • stomach acid

• attrition

  • tooth to tooth contact

• abrasion

  • over brushing, eating coarse foods

• occupational habits

  • holding items in teeth

  • environmental dust

What are the primary bones involved in mastication (chewing)?

• maxilla - fixed

• mandible - movable

• temporal bones - enabled movement

What is the temporomandibular joint?

• modified hinge joint that connects the jawbone to the skull, allowing for movement during chewing and speaking

• modified hinge synovial joint

  • fibrous capsule and ligament

  • articular cartilage and disc

What are the anatomical boundaries of the temporomandibular joint and what movements does it permit?

• anatomical boundaries

  • mandibular fossa

  • articular tubercle of the temporal bone

  • mandibular head

• permits movement in multiple planes

  • elevation - close mouth

  • depression - open mouth

  • protrusion - forward movement

  • retraction - backward movement

  • lateral movement - side to side

What innervates the muscles of mastication?

Mandibular division of the trigeminal nerve (CN V₃)

Muscles of Mastication: Origin, Insertion, & Action of Temporalis

• Origin: temporal fossa floor

• insertion: tip and medial surface of coronoid process

• action: elevates and retrudes jaw

Muscles of Mastication: Origin, Insertion, & Action of Masseter

• origin: maxillary process of zygomatic bone and zygomatic arch

• insertion: angle and lateral ramus of mandible

• action: elevates jaw (+ superior fibers protrude)

Muscles of Mastication: Origin, Insertion, & Action of Lateral Pterygoid

• origin: infratemporal surface/crest of sphenoid and lateral surface of lateral pterygoid plate

• insertion: joint capsule, articular disc, neck of condyloid process of mandible

• action: acting bilaterally, protrudes and depresses chin. acting unilaterally, swings contralaterally

Muscles of Mastication: Origin, Insertion, & Action of Medial Pterygoid

• origin: medial surface of lateral pterygoid plate, pyramidal process of palatine bone, tuberosity of maxilla

• insertion: medial surface of ramus of mandible

• action: elevates jaw with masseter contributes to protrusion and small lateral movements when working unilaterally

Describe the oral cavity

• start of the digestive tract

• extends from the oral fissure to the pharynx

• anatomical boundaries

  • roof - hard and soft palates

  • walls - cheeks and lips

  • floor - muscle

  • lined with stratified squamous epithelium

• contains teeth, tongue (fills most of the cavity), gingivae, palate and tonsils

Oral cavity floor, insert picture from slide 8

• mylohyoid muscle

• covered with non- keratinized stratified squamous epithelium

• innervated by the mandibular division of the trigeminal nerve (CN V₃)

Dorsal surface of the tongue

• rough with dull appearance

• para-keratinized stratified squamous epithelium

• anterior part in oral cavity

• posterior part in oropharynx

• lingual tonsils underly the epithelium of the posterior third (lymphoid tissue)

insert imagef from slide 10

Ventral surface of tongue

• smooth and shiny appearance

• non-keratinized stratified squamous epithelium

• sublingual caruncle and opening of submandibular duct

insert image from slide 10

Muscles of the tongue: Intrinsic vs Extrinsic

• Intrinsic: alter tongue shape

  • originate and insert within the tongue

  • superior and inferior longitudinal fibers

  • transverse fibers

  • vertical fibers

• extrinsic: alter tongue position

  • originate outside the tongue but insert within the tongue

Muscles of the Tongue: Origin, Insertion, & Action of Genioglossus

• origin: genial tubercle of mandible

• insertion: tip and body of tongue

• action: depresses center of tongue, protrudes tongue, deviates tongue

Muscles of the Tongue: Origin, Insertion, & Action of Hyoglossus

• origin: hyoid bone

• insertion: inferolateral aspect of tongue

• action: depresses and retrudes tongue

Muscles of the Tongue: Origin, Insertion, & Action of Styloglossus

• origin: styloid process of temporal bone

• insertion: posterolateral aspect of tongue

• action: retrudes tongue and curls sides

Muscles of the Tongue: Origin, Insertion, & Action of Palatoglossus

• origin: palatine aponeurosis

• insertion: posterolateral aspect of tongue

• action: elevates back of tongue/ depresses soft palate

Neurovasculature of the tongue

• motor

  • hypoglossal (CN XII) for most

  • palatoglossus innervated by Pharyngeal plexus (CN X)

• arterial supply

  • lingual branch of external carotid artery

• sensory

  • differs depending on type and location (insert pic from slide 12)

• venous drainage

  • lingual vein > internal jugular vein

Salivary glands function

• produce saliva which drains into oral cavity

• serous fluid that washes oral cavity

• mucin for lubrication

• amylase for carbohydrate digestion

• lysozyme as an antibacterial

• immunoglobin A for defense

• high pH to reduce acidity and prevent tooth decay

Salivary gland’s accessory organs

• parotid x 2

• sublingual x 2

• submandibular x 2

• and more minor glands: labial, buccal, palatal, lingual

Parotid gland

• largest

• posterior to mandible

• duct opens opposite second molar

• facial nerve and vessels pass through it

• serous saliva

• parasympathetic innervation- glossopharyngeal (IX)

Submandibular gland

• wraps around mylohyoid

• duct opens at the sublingual papilla

• serous and mucosal saliva (3:2)

• parasympathetic innervation - Facial (VII)

Sublingual gland

• located in the floor of the mouth (sublingual fold)

• multiple ducts open into the sublingual fold

• serous and mucosal saliva (1:3)

• parasympathetic innervation - Facial (VII)

Oral cavity roof - anterior hard palate

• Bony skeleton

  • palatine processes of the maxillae

  • horizontal processes of palatine bones

• mucosa

  • oral surface - keratinized stratified squamous epithelium

  • nasal surface - respiratory epithelium

  • underlying lamina propria - contains blood vessels and nerves

• transverse palatine folds *rugae)

  • assist with manipulation of food during mastication

• sensory innervation

  • maxillary division of the trigeminal nerve (CN V₂)

Oral cavity roof - posterior soft palate

• suspended from hard palate and ends at the uvula

• mucosa

  • non-keratinized stratified squamous epithelium

  • underlying lamina propria - contains blood vessels and nerves

Muscles of the soft palate and why they are important

• levator veli palatini, tensor veli palatini, palatoglossus, palatopharyngeus

• most are innervated by pharyngeal plexus (CN X) for most, mandibular division of the trigeminal nerve (CN V₃) for the tensor veli palatini

• prevents food bolus from entering nasal cavity

• prevents food bolus from re-entering oral cavity

• protects the airway when swallowing

• allow expansion during swallowing

• regulates air entering the nose during phonation

• facilitate movement of air through pharynx

Pharynx

• the oropharyngeal isthmus connects the oral cavity and pharynx

• anatomical boundaries:

  • superior - soft palate

  • inferior - posterior 3rd of the tongue

  • lateral - palatoglossal arch

• pharynx is a musculomembranous tube

  • extends from the base of the skull to the esophagus

  • anterior openings - nose, mouth, larynx

  • 3 divisions

Nasopharynx

• extends from the nasal choanae to the tip of the soft palate

  • contains the ostium of the auditory (eustachian) tube

  • additional tonsils

• mucosa

  • lined by pseudostratified ciliated columnar epithelium

Oropharynx

• extends from tip of the soft palate to the superior aspect of epiglottis

• extends anteriorly from the oropharyngeal isthmus

• contains folds and tonsils

mucosa

• lined by non-keratinized stratified squamous epithelium

Laryngopharynx

• extends from epiglottis to the esophagus

• laryngeal inlet located anteriorly and bounded by epiglottis

• posterior 1/3 of tongue runs vertically in the anterior wall

• mucosa

  • lined by non-keratinized stratified squamous epithelium

Muscles of the pharynx

• constrictor muscles

  • 3 pairs of overlapping muscles

  • contract sequentially to push food bolus into esophagus

  • all innervated by pharyngeal plexus (CN X)

• longitudinal muscles

  • shorten and widen pharynx

  • elevate pharynx and larynx

  • open the auditory tube

Esophagus

• muscular tube which extends from laryngopharynx to the stomach (C6-T10)

• passes through

  • neck, thorax, and abdomen

  • diaphragm at esophageal hiatus (T10)

• lower esophageal sphincter prevents reflux

• smooth muscle innervated by the autonomic nervous system

  • upper portion continuous with inferior constructor

  • lower portion continuous with muscle of stomach

Histology of Esophagus

Mucosa

• non-keratinized stratified squamous epithelium

• lamina propria

• muscularis mucosa- longitudinally arranged fibers

Submucosa

• contains mucous glands, blood vessels, lymphatics & nerves

Muscularis externa

• inner circular fibers

• outer longitudinal

Adventitia

• the esophagus is extraperitoneal therefore it is covered with an adventitia

Neurovasculature and Lymphatics of upper 3rd trunk/head

supplied by inferior thyroid artery from subclavian artery

drains into inferior thyroid vein then brachiocephalic vein

lymph drains into deep cervical nodes

Neurovasculature and Lymphatics of middle 3rd trunk/head

supplied by descending aorta

drains into azygos veins then superior vena cava

lymph drains into superior and posterior mediastinal nodes

Neurovasculature and Lymphatics of lower 3rd trunk/head

supplied by celiac trunk from left gastric artery

drains into left gastric veins then portal system

lymph drains into celiac nodes

Innervation of trunk/head

Parasympathetic - vagus nerve (CN X)

Sympathetic - sympathetic trunks/ chains