If the previous episode was about hidden corridors,
this chapter is about living ground.
Because here, beneath the tongue, lies a region that:
Lifts
Moves
Secretes
Coordinates
It is not static anatomy.
It is functional architecture in motion.
And everything converges here:
Air becomes speech
Food becomes swallow
Thought becomes articulation
PART I - THE SUBMANDIBULAR REGION: THE FOUNDATION
Defined as the space between:
Mandible (above)
Hyoid bone (below)
This is a transition zone:
Between head and neck
Between structure and function
Contained within:
Suprahyoid muscles
Tongue musculature
Submandibular and sublingual glands
Boundaries (Think: The Triangle)
From the description on page 230:
Superior → Inferior border of mandible
Inferolateral → Anterior & posterior bellies of digastric
Floor → Mylohyoid muscle
A triangle that supports the tongue above it - like a sling.
PART II - MUSCLES OF THE FLOOR: THE SUSPENSION SYSTEM
From the table on page 231 (Table 15-1), the key players:
Suprahyoid Muscles
Digastric
Stylohyoid
Mylohyoid
Geniohyoid
Core Concept
All attach to the hyoid bone.
And together they:
Elevate the floor of the mouth
Assist swallowing
Help open the jaw
Mylohyoid - The True Floor
From the diagram on page 232 (Fig 15-1):
Forms a muscular sheet
Meets its partner at the midline (median raphe)
Supports the tongue above it
This is the “floorboard” of the oral cavity.
Digastric - The Dual Force
Two bellies:
Anterior → pulls hyoid forward
Posterior → pulls hyoid backward
Together:
Elevate hyoid
Open the mouth when hyoid is fixed
A muscle of balance - pulling in two directions to create control.
PART III - THE TONGUE: SHAPE AND DIRECTION
The tongue is not a single muscle.
It is a muscular orchestra.
Two Systems
From page 233–235:
1. Intrinsic Muscles
Longitudinal
Transverse
Vertical
Function:
Change shape of tongue
2. Extrinsic Muscles
Genioglossus → protrudes
Hyoglossus → depresses
Styloglossus → retracts
Palatoglossus → elevates posterior tongue
Function:
Control direction of movement
From the diagram on page 234 (Fig 15-4):
You can see fibres fanning, crossing, intermingling
No single movement is isolated.
Every action is coordinated complexity.
Innervation Rule
All tongue muscles → Hypoglossal nerve (CN XII)
Exception → Palatoglossus (pharyngeal plexus)
PART IV - SALIVARY GLANDS: THE MOISTURE SYSTEM
Two major glands live here:
Submandibular gland
Sublingual gland
Submandibular Gland
From page 238 and Fig 15-9:
Located in submandibular triangle
Extends into floor of mouth
Drains via Wharton’s duct → sublingual caruncle
Sublingual Gland
Lies beneath tongue
Above mylohyoid
Drains via multiple small ducts (Rivinus)
Sometimes forms a larger duct (Bartholin)
These glands are quiet workers -
ensuring lubrication, digestion, and speech.
Innervation (The Secretory Pathway)
From page 239:
Parasympathetic → Facial nerve (via chorda tympani)
Synapse → Submandibular ganglion
Travel via → Lingual nerve (V3)
A beautiful relay:
Facial nerve → Lingual nerve → Glands
PART V - NERVES: THE COMMUNICATION NETWORK
Trigeminal Nerve (V3)
Lingual nerve:
General sensation to anterior 2/3 of tongue
Carries taste (via chorda tympani)
Hypoglossal Nerve (CN XII)
Motor to tongue
Runs deep across carotid system
Ends at tongue tip
From the diagram on page 240 (Fig 15-10):
You can trace its course beneath muscles toward the tongue
PART VI - BLOOD SUPPLY: THE FLOW
Lingual Artery
Branch of external carotid
Supplies tongue and floor
Key branches:
Deep lingual
Sublingual
Dorsal lingual
Facial Artery
Supplies submandibular gland
Gives submental branch
Venous Drainage
Deep lingual veins
Drain into:
Facial vein
Internal jugular vein
PART VII - LYMPHATIC DRAINAGE: THE HIDDEN EXIT
From page 242:
Submandibular nodes drain:
Lips
Nose
Tongue
Key node:
Jugulodigastric node (principal node of tongue)
This is where disease travels quietly before it is seen.
PART VIII - CLINICAL THREADS
1. Tongue Cancer
Most common oral cavity cancer
Often squamous cell carcinoma
Early spread to deep cervical nodes
2. Hypoglossal Nerve Injury
From page 240:
Causes tongue paralysis on one side
Tongue deviates toward lesion on protrusion
Leads to muscle atrophy
3. Sialography
Imaging of salivary ducts
Used for obstruction
4. Surgical Risk
Sublingual artery variation → bleeding risk
Close anatomical relationships demand precision
Key Takeaways
Submandibular region is a functional bridge between head and neck
Mylohyoid forms the true floor of the mouth
Tongue = intrinsic (shape) + extrinsic (movement)
Hypoglossal nerve controls nearly all tongue movement
Salivary glands are essential for lubrication and digestion
Rich vascular and lymphatic networks create both resilience and risk
