Download 10-Anterior triangle2008-11-12 22:064.3 MB

ANTERIOR TRIANGLE
It is in front of the sternomastoid
muscle.

BOUNDARIES
Anteriorly: midline of 
the neck.
Posteriorly: anterior 
border of
sternomastoid.
Superiorly: lower 
margin of the body of
the mandible.
BOUNDARIES
Roof: 
skin, superficial
fascia
(containing
platysma) and
the Investing
layer of deep
cervical fascia.

SUBDIVISIONS
The anterior triangle
is subdivided by :
The anterior and 
posterior bellies of
the digastric and
The superior belly of
omohyoid into (4)
smaller triangles:


SUBDIVISIONS
Submental. 
Submandibular (Digastric).
Carotid. 
Muscular 

DIGASTRIC MUSCLE
The muscle has two 
bellies:
Anterior and Posterior. 
The posterior belly : 
arises from the mastoid
process and inserted into
the intermediate tendon.
The anterior belly 
attached to the lower
border of body of
mandible.
DIGASTRIC MUSCLE
Intermediate 
tendon :
It pierces the 
insertion of
stylohyoid.
It binds to the 
hyoid bone by a
loop of deep fascia.
DIGASTRIC MUSCLE
Nerve supply : 
The facial nerve 
supplies the
posterior belly.
The nerve to 
mylohyoid supplies
the anterior belly.
DIGASTRIC MUSCLE
Action : 
Depression of the
mandible OR
Elevation of the 
hyoid bone.

STYLOHYOID
It originates from the
styloid process.
It runs along the 
upper border of the
posterior belly of
digastric.
It is inserted into the
hyoid bone (between
body and greater
horn).


STYLOHYOID
Nerve supply :
Facial nerve. 
Action : 
Elevation of 
hyoid bone.

SUBMENTAL TRIANGLE
It lies below the chin. 
Its boundaries are: 
Anteriorly: midline of 
the neck.
Laterally: anterior belly
of digastric.

SUBMENTAL TRIANGLE
Inferiorly : body
of the hyoid.
Floor: mylohyoid
muscle.


MYLOHYOID
It is a flat triangular 
sheet that supports
the floor of the
mouth and tongue.
It takes origin from 
the mylohyoid line of
the mandible.
MYLOHYOID
Insertion: 
The anterior fibers 
are inserted into a
fibrous raphe.
The posterior fibers 
are inserted into the
body of hyoid bone.
MYLOHYOID
Nerve supply : 
It is supplied by
the nerve to
mylohyoid (from
inferior alveolar
of mandibular).

MYLOHYOID
Action : 
If the mandible is fixed, it 
elevates the floor of the
mouth as in deglutition.
If the hyoid bone is fixed, it
depresses the mandible and
opens the mouth.

SUBMENTAL TRIANGLE
Contents : 
Submental lymph
nodes.
They receive 
lymph from the
tip of the tongue.

DIGASTRIC TRIANGLE
It lies below the body
of the mandible.
It is bounded by: 
Anteriorly: anterior 
belly of digastric.
Posteriorly: posterior
belly of digastric and
stylohyoid.


DIGASTRIC TRIANGLE
Superiorly: 
lower border of
the body of the
mandible.
Floor: 
mylohyoid and
hyoglossus
muscles.


DIGASTRIC TRIANGLE
Contents: 
A. Anterior part : 
(1) Submandibular 
salivary gland.
(2) Facial artery (deep
to gland).
(3) Facial vein 
(4) submandibular 
lymph nodes (both
superficial to gland).

DIGASTRIC TRIANGLE
(5) Hypoglossal
nerve.
(6) Nerve and 
vessels to
mylohyoid.

DIGASTRIC TRIANGLE
B. posterior part: 
1. Carotid sheath 
(carotid arteries
internal jugular
vein and vagus
nerve).
2. Lower part of 
the parotid
gland.
CAROTID TRIANGLE
It lies behind the hyoid 
bone.
It is bounded by: 
Superiorly: 
posterior belly of 
digastric.
Inferiorly: superior belly
of omohyoid.

CAROTID TRIANGLE
Posteriorly: 
anterior border of 
sternomastoid.
Floor: 
thyrohyoid, 
hyoglossus,
middle and inferior 
constrictors of the
pharynx.
CAROTID TRIANGLE
Contents: 
(1) Carotid sheath and
its contents.
(2) Hypoglossal nerve
and its descending
branch.
(3) Acessory nerve. 


CAROTID TRIANGLE
(4) Internal and
External
laryngeal nerves.
(5) Deep cervical
lymph nodes.


CAROTID SHEATH
It is a condensation
of deep cervical
fascia.
It is attached to the
base of the skull
superiorly and fuses
with the
pericardium
inferiorly.


CAROTID SHEATH
Contents : 
1. Common and 
internal carotid
arteries.
2. Internal jugular 
vein.
3. Vagus nerve. 
4. Deep cervical lymph
nodes form a chain
along the internal
jugular vein.

CAROTID SHEATH
It is crossed by 
the following
nerves:
Glossopharyngea 
l.
Hypoglossal. 
Spinal part of 
acessory.
MUSCULAR TRIANGLE
It lies below the hyoid
bone.
It is bounded by: 
Anteriorly : 
midline of the neck. 
Superiorly: 
superior belly of 
omohyoid.

MUSCULAR TRIANGLE
Inferiorly: 
anterior border of 
sternomastoid
Floor: 
sternohyoid and 
sternothyroid muscles.
MUSCULAR TRIANGLE
Beneath the floor
lie:
Thyroid gland. 
Larynx. 
Trachea. 
Esophagus. 

INFRAHYOID MUSCLES
They are thin, strap
like muscles.
They are composed
of
Sternohyoid. 
Sternothyroid. 
Thyrohyoid. 
Omohyoid. 


INFRAHYOID MUSCLES
Action : 
(1) stabilization of 
the hyoid bone to
make a base for the
movements of the
tongue.
(2) Assist in the 
movements of the
larynx in
swallowing.
INFRA HYOID MUSCLES
Nerve supply : 
All are supplied by 
the ansa cervicalis
(C1,2&3) except
Thyrohyoid (supplied
by C1 through the
hypoglossal nerve).

INFRA HYOID MUSCLES
Origin : 
Sternohyoid & 
Sternothyroid :
posterior surface of the
manubrium.
Insertion : 
Hyoid bone (lower 
border).
Oblique line of thyroid
cartilage.


INFRA HYOID MUSCLES
Thyrohyoid : 
Origin : 
oblique line of 
thyroid cartilage.
Insertion : 
hyoid bone (lower
border).

INFRA HYOID MUSCLES
Omohyoid : 
Inferior belly : 
Origin : suprascapular 
ligament and
suprascapular notch.
Superior belly: 
Origin : 
intermediate tendon. 
Insertion : hyoid bone 
(lower border).