AnTeRIoR TRIAnGLe of neck
DR (BRIG) SUSHIL KUMAR
PROFESSOR & HEAD
DEPT OF ANATOMY
AMRITA SCHOOL OF MEDICINE
FARIDABAD –121002
anatomist91@gmail.com
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FRONT OF NECK
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TRIANGLES OF NECK
2
1
AT 3
AT
PT
4 PT
Ant Triangle
Post Triangle
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TRIANGLES: BOUNDARIES & DIVISIONS
SCM
AT
PT
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TRIANGLES OF NECK
Digastric triangle Mastoid process
Mandible
Digastric (Ant belly)
Hyoid
Post Triangle
Omohyoid (Sup belly) Omohyoid (Inf belly)
Trapezius
Sternocleidomastoid
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TRIANGLES OF NECK
Submental (Suprahyoid) triangle
Digastric (Submaxillary) triangle
Carotid triangle SCM
Occipital triangle
Muscular (Inf Carotid) triangle
Supraclavicular triangle
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ANTERIOR TRIANGLE OF NECK
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ANTERIOR TRIANGLE OF NECK
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MIDLINE STRUCTURES IN NECK
Midline structures: Divided into Suprahyoid &
Infrahyoid structures
Suprahyoid Structures
In Submental triangle:
Submental LNs
Mylohyoid raphe
Infrahyoid Structure
Hyoid bone (C-3)
Thyrohyoid membrane
Notch of thyroid cartilage (C-4)
Cricoid cartilage (C-6)
Tracheal rings
Isthmus of thyroid gland (2nd, 3rd tracheal rings)
Suprasternal notch (disc between T-1 & T-2)
Sternocleidomastoid divides side of neck into:
Anterior & Posterior triangles
9
SUPRA & INFRAHYOID MUSCLES
DG Stylohyoid
DG
ELEVATORS GH MH
Geniohyoid
Hyoid
Mylohyoid
Digastric (both bellies)
Stylohyoid
DEPRESSORS Thyroid
cartilage
Sternohyoid
Sternothyroid
Cricoid
Omohyoid (two bellies)
Sternohyoid Sternothyroid
2/22/2024 Omohyoid
ANTERIOR MIDLINE STRUCTURES
C-3
HYOID
Thyrohyoid Anatomical events at lower border of
membrane Cricoid cartilage: C-6 Vertebra
1. Jn of Larynx with Trachea
C-4
Thyroid 2. Jn of Pharynx with Esophagus
cartilage 3. Inf Thyroid Artery enters gland
4. Middle Thyroid Vein emerges
Cricothyroid
5. Vertebral artery enters FT of C-6
membrane
C-6 6. Sup belly OH crosses C Sheath
Cricotracheal
7. Middle Cervical Ganglion
ligament THYROID GLAND 8. CCA compressed against
Tracheal ring Tr Pr of C-6 (carotid tubercle)
Trachea
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ANTERIOR TRIANGLE:
BOUNDARIES & SUBDIVISIONS
Boundaries
In front: Midline neck structures
Above: Base of mandible
Behind: Anterior border of SCM
Subdivided into:
Muscular triangle
Carotid triangle
Digastric triangle
Submental triangle
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ANTERIOR TRIANGLE: SUBDIVISIONS
D I
N B
A L
M E
1 2
3
Omohyoid
4
1. Digastric
(sup belly)
Sternohyoid 2. Submental
3. Carotid
4. Muscular
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ANTERIOR TRIANGLE:
SUBDIVISIONS & BOUNDARIES
Digastric
Digastric 1 (Ant belly)
(Post belly) Hyoid
2 Omohyoid
(Sup belly)
3
1. Digastric triangle
2. Carotid triangle
Omohyoid 3. Muscular triangle
(Inf belly)
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ANTERIOR TRIANGLE
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SUBMENTAL TRIANGLE
Boundaries
Unpaired; Anterior bellies of both digastric muscles
Apex: At chin
Base: Body of hyoid
Floor: Mylohyoid muscles
Contents
Small veins uniting to form Ant Jugular Vein
LNs
Facial artery Digastric (Ant belly)
Mylohyoid
Masseter Mylohyoid raphe
SM gland (outline) Hyoglossus
Digastric (Post belly)
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Hyoid ASM Intermediate tendon 18
MUSCULAR TRIANGLE
Boundaries
Median line from hyoid to sternum
Inferoposteriorly: Anterior margin of SCM
Posterosuperiorly: Superior belly of omohyoid
Contents:
Mandible
Infrahyoid muscles Midline
Sternohyoid
Omohyoid (Sup belly) Omohyoid
Thyrohyoid Muscular
triangle
Sternothyroid SCM
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MUSCULAR TRIANGLE: STRAP MUSCLES
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INFRAHYOID STRAP MUSCLES OF NECK
Developmentally
• Derivatives of longitudinal rectus sheath; extends from chin to pubic symphysis
• Sheet divided into different parts
• Some parts disappear
Existing parts include:
Geniohyoid (suprahyoid component)
Infrahyoid muscles (between hyoid & sternum)
Sternalis (occasional) in front of sternum
Rectus abdominis & Pyramidalis
Omohyoid attachment to scapula is secondary, following migration from medial end of clavicle
Infrahyoid muscles (4) are arranged in two strata:
Superficial stratum: Sternohyoid & Omohyoid
Deep stratum: Sternothyroid & Thyrohyoid
All are supplied by Ansa cervicalis
Since attached to hyoid & thyroid cartilage, thus, move them
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Boundaries DIGASTRIC (SM) TRIANGLE
Above: Base of mandible & line joining angle of mandible to mastoid Pr
Posteroinferiorly: Digastric (posterior belly) & Stylohyoid
Anteroinferiorly: Digastric (anterior belly)
Roof: Skin, Superficial fascia with Platysma & Deep fascia (Investing layer)
Floor: Mylohyoid & Hyoglossus
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DIGASTRIC TRIANGLE: CONTENTS
In Anterior Region
Submandibular Gland
Facial Vessels
Submental Vessels
Mylohyoid Vessels & Nerve
Submandibular LNs
In Posterior Region
Submandibular land
Parotid gland (lower part)
External Carotid Artery
XII CN
Stylohyoid muscle
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Boundaries
CAROTID TRIANGLE
Posteriorly: SCM
Anteroinferiorly: Omohyoid (superior belly)
Superiorly: Digastric (posterior belly) & Stylohyoid
Roof: Skin, Superficial fascia with Platysma & Deep fascia
Floor: Thyrohyoid, Hyoglossus, Constrictors of Pharynx (Inferior & Middle)
Stylohyoid
Digastric (Post belly)
Hyoid SCM
Omohyoid (Sup belly)
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CAROTID TRIANGLE: CONTENTS
CCA & divisions (ECA & ICA)
• Branches of ECA
Superior Thyroid
Lingual
Facial
Occipital
Ascending Pharyngeal
• IJV & tributaries
• X, XI & XII CNs
• Superior laryngeal nerve
– Internal laryngeal nerve
– External laryngeal nerve
• Sympathetic chain
• Deep Cervical LNs (JD & JO)
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CARITID TRIANGLE & CAROTIDS
8
7 I
E 6
C ECA: Branches
C A 5
4 A
1. Ascending Pharyngeal
2. Superior Thyroid
3. Lingual
1
4. Facial
3
I 5. Occipital
J 6. Posterior Auricular
2 C V 7. Maxillary
C
8. Superficial Temporal
A
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STERNOCLEIDOMASTOID
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STERNOCLEIDOMASTOID
Forms common boundary of neck triangles; Arises by two heads:
Sternal head: Upper part of anterior surface of manubrium sterni
Clavicular head: Superior surface of medial third of clavicle
Insertion: Mastoid process & lateral half of superior nuchal line
XI CN passes deep to SCM, pierces (& supplies) it; reappears just above middle of posterior border
Nerve supply
Spinal accessory nerve (XI CN)
Branches from ventral rami of 2nd - 4th cervical nerves
Actions
Acting alone, SCM tilts head towards same shoulder; simultaneously rotates head so that face turns towards
opposite side (sideways glance)
Acting together from below, muscles draw head forwards, help longus colli to flex cervical vertebral column
(common in feeding)
Two muscles used to raise head when body is supine
When head fixed, help to elevate thorax in forced inspiration
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TORTICOLLIS
Reflex
Compression of XI CN in infection of Head & Neck
Congenital
Bleeding in SCM; causes fibrous shortening of SCM
Psychogenic
Abnormal use of neck
Spasmodic
Defective Basal ganglia function, sustained action
of SCM
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ANSA CERVICALIS
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