Anterior Triangle 8

7/29/2019 Anterior Triangle 8

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The borders of the ant. triangle:

1- The base: The whole inferior border of the mandible, the base of thistriangle located superiorly.

2- The apex: located where the medial border will mix the lateral border inthe mid line in the jugular notch (suprasternal notch)-the upper part of

the sternum, the apex located inferiorly.

3- The anterior border: formed by Imaginary Midline crossing the middle. Ofthebody (mid-sagittal line).

4- The pos.border: will be the anterior border ofSCM (sternocleidomastoidmuscle in ant. Aspect of the neck).

So many structures find in this triangle so in order to

Anterior triangle of the neck


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simplifying its study we divide this triangle into further four triangles => so

we use mainly two important muscles in this area:

Digastric muscle (one of the suprahyoid muscle. (ant and pos.bellies) alongwith thesup. Belly of omohyoid muscle, those three bellies ofmuscles are used to divide the anterior triangle into four subtriangles:SubmentalSubmandibular (Digastric)CarotidMuscular.

1- Submental triangle:

It is bellow the mental area (bellow the chean?) , smallest one, some anatomist

considered this triangle as one submental triangle, other texts as twotriangles one to the right and one to the left based on the mid-imaginary

line, Borders of this triangle:

The lateral part is the ant.belly of digastric, the medial boundary is mid.sagittal

line, the base by the body of the hyoid bone.

The contents:............................

a small group ofsubmental veins that unit to form larger vein in the superfacialfascia these vein is the ant. jugular vein then it descends all the way down

out of the triangle through the neck to go and drain into external jugular

vein at the root of the neck bellow,,, another thing we can find a group of

lymph nodes that responsible for draining of the lymph from the chean

(submental lymph nodes).


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2- Submandibular triangle(digastric

triangle):

digastric because all the digastric muscle contributing in this triangle,

submandibular because its bellow the mandible, one in each side, its

containing a large part of the submandibular salivary glands.

Remember; we have three salivary glands, one sublingual located beneath the

tongue, and the other two glands are parotid and submandibular (we can

find it in this triangle) so we classified thesubmandibular triangle as

glandular triangle.

The Boundaries: the lateral is the inferior border of the mandible, the medial is

the anterior belly of digastric, posteriorly: post. belly of digastric, the floor:

is bond by two important musclesthe flat sheet that extends from themandible to the mid-line which is mylohyoid muscle which represented the

floor of the mouth, anything above it will be in oral cavity and anything

bellow it will be in the neck- the other muscle behind it, is-hyoglossus

muscle.

P.S.: hyoglossus muscle: its one of the muscles responsible for moving of thetongue, its located at the base of the tongue, -hyo- from hyoid bone and

glossus is part of the tongue).

-The contents:..............................

submandibular gland

the submandibular gland which is the second in size from the major salivary

glands after the sublingual gland, its sleeping in the pos.border of mylohyoid

muscle, part of this gland is located in the cervical region-superficially- and

the other smaller part of the gland is deep within the oral cavity-above

mylohyoid-sothe superficial part of submandibular gland located in the


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submandibular triangle, in addition to the gland there are blood vessels, the

vein and artery located in the submandibular triangle are the fascial

ones(fascial artery and fascial vein)- facial artery which providing blood

supply to the face and the facial veins draining the blood from the face,

however; IF we look to their relation to submandibular gland we can see the

artery loops deep to superficial part of that gland and the vein go to

superfacial aspect of it.

Blood vessels :

In the head and neck region the main blood supply comes from thecommon

carotid artery which divide into and internal go to the brain and external.

the external carotid gives many branches one of them is the fascialartery;the facial artery arise from the ant. aspect of external carotid, when it

arising there it passes deep to pos.belly of digastric and stylohyoid muscle

(from the styloid process to hyoid bone). As The fascial artery crossing the

pos.belly of digastric it will inter to submandibular triangle, once the artery

enter it will go between the submandibular and the floor of the triangle

then the artery loops at the inferior border of the mandible and ascends up

into the face, at the looping area its become very superficial soits very

easily to feel the pulse of these artery and this region we refer to it asfacial pulse.

-Three major areas to measure the pulse in the head and neck region one of

them is The lower border of the mandible.

- However;when the vein comes back it doesnt do all thislooping and deep, it pass directly all the way superficially

to the gland and descends down to drain into internal

jugular. so its a superficial vein.

the nerves

2 important nerves in the submandibular triangle

contents of the

submandibular triangle:

facial veins

facial arteries

2 nerves : hypoglossal n.

& n. to mylohyoid.

organs : the facial part

of submandibular salivary

gland.

group of lymph nodes.


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1- hypoglossal nerve CN (XII)

from the brain through the hypoglossal canal "in the posterior

cranial fossa" then it descends down until it appears at the carotid

triangle then it loops and go deep to the post. belly of digastricmuscle (which is the border between the carotid triangle and

submandibular triangle) there it will find one of its favorite

muscles "hyoglossus muscle" going above mylohyoid to reach the

tongue in the oral cavity.

fxn : motor innervations of the tongue muscles

Sohypoglossal nerve located into two triangles :carotid triangle , submandibular triangle

2- nerve to mylohyoid :

branch from the inf. alveolar nerve (inf. dental n.) just before it

inters the mandibular foramen gives a branch which goes medially

crossing over the floor of the oral cavity near the inf. aspect of

mylohyoid muscle and innervate it , it's name is "nerve tomylohyoid". after that it goes to innervate the anterior belly of

digastric by passing between mylohyoid superiorly and anterior

digastric inferiorly.

submandibular L.N.

located on the lateral and medial border of the sub mandibular

glands.

in the posterior cranial

fossa there are 4 main

openings:1- jugular foramena

2- foramen magnum

3- hypoglossal canal

4- internal auditory

meatus

Q: the posterior bellyof digastric formingborder of which triangleBoth the carotid and thesubmandibular triangle


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Carotid Triangle

the borders :

sup. --> post. belly of digastric

inf. --> sup. belly of omohyoid

post. --> SCM

the contents :

in the contents we have to find 5 different structures

carotid sheaththe most important structure it is part of the deep cervical facia that contain 4

structures :internal jugular vein (IJV) the most lateral ,common --> internal carotid

artery (ICA) the most medial , vagus nerve the most posterior and the internal

group of cervical lymph nodes following the IJV.

nerves:1- ansa cervicalis :

ansa (loop) cervicalis (in the neck), it is usually attached to the anterior part of the

carotid sheath , it's made by the anterior ramie of C1(ant.root) ,C2&C3(pot.root)

it innervate all the infrahyoid muscles except thyrohyoid muscle.

cervical part of sympathetic chain:

it is responsible for the autonomic innervations (sympathetic) while vagus n.(ant.

to it) is the parasympathetic , it has 3 parts cervical thoracic & abdominal, it is

attached to the posterior part of the carotid sheath .


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" ansa cervicalis & sympathetic chain are NOT within the carotid sheath but they

are attached to it from ant. and post. "

2- Hypoglossal nerve :

1stly appears at the carotid triangle then crossthe border deeply (post. belly of

digastric) to get into submandibular triangle then meet the hyoglossus m. then

within it to the tongue.

External carotid artery (ECA):the carotid a. is a branch from the brachiocephalic a. (Right) behind the sterno

clavicular joint & arch of aorta (Left) then ascend up and inter the neck region.

in the neck at the level of adam's apple (upper border of thyroid cartilage, disc C3-

C4 ) the common carotid a. cleaves into internal and external carotid arteries (ICA,

ECA) the ICA continuo through the carotid sheath but the ECA leave the carotid

sheath.

so u can see the ECA within the carotid triangle but it's out the carotid sheath.

Branches:

common carotid a. : has no branches

ICA : has no branches out the skull .

ECA: gives 8 branches after it leaves the carotid sheath

P.S. plz follow the pic while studying its useful :) ---> nxt page


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ECA starts at the level of C3-C4 & terminates behind neck of the mandible we

classify them based on ascending aspect of the artery :

1-ascending pharyngeal a. : the first branch from the medial aspect of the ECA

to the wall of the pharynx then ascend up to the wall of the pharynx providing

blood supply to the muscles forming the wall of the pharynx .

then we will have the next three important anterior branches:


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2-superior thyroid a. : the first one of the ant. branches it goes inferiorly to the

thyroid gland , sup. cuz it reaches thyroid from above. the inf. one come from the

subclavian a.

3-lingual a. :the second one of the ant. it goes to supply the tongue.

4- facial a. : the third and the most superior ant. branch , goes ant. deep to the

digastric m. inter the sub mandibular triangle deep to the sub mandibular gland

then make looping on the lower border of the mandible and goes into the face to

supply it.

then we will have the next two posterior branches:

5-posterior auricular a. : a smaller post. branch that goes behind the auricle

between the external meatus & the mastoid process, supplying the skin behind

the auricle.

6-occipital a.the larger post. branch that ascend all the way behind the mastoid

process to provide blood supply to the posterior half of the head and scalp (

)" we've seen it in the apex of the post. triangle",

then the artery ascends until the neck of the mandible we will have the final two

large branches:

7-superficial temporal a. : it's a super facial a. over the

temporal bone it has two branches anterior and posterior

superficial temporal arteries ,U will feel the puls ant. to the

tragus of the ear which is "the temporal puls"

8-maxillary a. : it's considered the largest branch , it goes deep

to the ramous of the mandible anteriorly into the infratemporal

fossa to provide blood supply to the maxillary teeth , then it

gives a branchout from the maxilla infraorbital a. , JUST to know

:D in this small passage of the maxillary a. it gives 15 branches.

"elle bdo y3rfhom 2lo t7ea 5a9a mny ..! :p"

till now we know 2 of

three regions of the puls

in the head and neck:

the lower border of the

mandible "facial puls" ,

anterior to auricle "the

temporal puls".

and the third oneisanterios to the SCM "the

carotid puls"


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there are two very important structures in the carotid

triangleat the bifurcation area "division area" :

Carotid Sinusa localized dilatation at the terminal rat of common carotid a.

or the beginning part of internal carotid a.

the wall of those arteries become very thin cuz the tunica

media becomes ver thin (the smooth muscles layer) so it

becomes weak and dilate in addition to that the

glussopharyngeal n. (IX) gives many nerve endings and

terminate in this sinus.

the net --> ( decrease the wall thickness and increase the

innervations) .... why? to monitor blood pressure

physiology of carotid sinus :it is a mechanoreceptor (pressoreceptor) when the

bld pressure increase "increase flowing rate" this will result a stretching in the

wall pressing the receptors and activating them those sends impulse all the way

back into the brain across the IX , The closest nerve to it is the vagus (X) which is a

parasympatetic that will send signal to viscera "lungs & heart" to reduce heart

beating (heart rate) then this will reduce bld pressure.

Carotid Bodyoval mass of connective tissue usually behind (post. to ICA) or at the bifurcation

area (between ICA &ECA) and there are also many nerve endings that sense the

O2 rate in the bld.

Remember:

Arteries made of three

layers : tunica intima, tunica

media & tunica adventitia.

the nervous nervosum

located in the tunica

adventitia.


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physiology of carotid body : it is a chemoreceptoe it sense the lower rate of O2

by the high rate of the CO2 in the bld by the glussopharengyal n. (IX) to the brain

sending signals to sympathetic chain which will increase the respiratory rate so

more O2 coming in.

The last thing is the muscular triangle in the next lec. :)

THE HAPPY END

Done by :

Asmaa Al-Mawas

Baraa'h Al-Salamat

Anterior Triangle 8

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