Wk5 - neck lymph nodes

Lymphnodes

Kidney bean-shaped capsules that are clustered in regions along the lymphatic vessels

They filter interstitial fluid from the body of foreign particles and pathogens

interstitial fluid

fluid filled spaces between blood vessels and tissue

Excess blood plasma squeezed out of blood vessels

how many lymph nodes in head + neck region

roughly 300

where are nodes found in the head + neck

grouped along the lower border of the jaw + behind the ears

Deep in the neck along the larger blood vessels

What do the head + neck lymph nodes drain

Skin of the scalp and face

Tissues of nasal cavity

Oral cavity, pharynx, trachea

Upper oesophagus

Salivary glands

Thyroid

primary function of lymph nodes

filter interstitial fluid + return it back to the vascular system

Initiate immune responses to antigens

Allows for B + T-cells to become exposed to a range of antigens

how do lymph nodes filter lymph

use B, T-cells and macrophages in nodes to filter fluid + destroy pathogens

Filtered lymphatic fluid is then emptied into venous blood supply

what happens in lymph nodes during an inflammation/immune response

trans-endothelial migration of lymphocytes into blood vessels occurs at HEV

Triggered by B and T cell endothelial surface receptors

Lymphocytes squeeze into blood vessels across their endothelial lining, artery then carries the lymphocytes to the affected area

anatomy of a lymph node

capsule

Trabeculae

Subscapsular sinus

Cortex + paracortex

Medulla + medullary cords

Hilum

HEV

Primary/secondary follicles

Afferent/efferent lymphatic vessels

capsule

Adipose tissue - dense connective tissue + collagenous fibres

Trabeculae - extensions of capsule inside node, radiates inwards

subcapsular sinus

space between the capsule and cortex

Allows for transportation of lymphatic fluid throughout the node

Cortex

outer part - layer beneath subcapsular sinus

Inner part - paracortex, close to medulla

medulla

innermost layer of node

Contains large blood vessels, sinuses, medullary cords

Cords contain antibody-secreting plasma cells, B-cells, macrophages

Hilum

depression near efferent vessels of node

Where blood vessels enter/exit the node

Region where LHV is found

LHV

longitudinal hilar vessels

Blood vessels that run through hilum

Detectable by doppler

Primary/secondary follicles

Both found in cortex

Primary = no germinal center

Secondary = germinal center

afferent/efferent vessels

afferent = enter node

Efferent = exit node

HEV

high endothelial venule

Where trans-endothelial migration of lymphocytes occurs

Where main artery/vein of lymph nodes filter terminates

Normal size of lymph node

1-2cm

Depends on location

Longitudinal axis should be 1cm or less

factors that make a lymph node abnormal

loses oval shape

Loss of hilar fat

Asymmetrical thickening of cortex

Enlarged

How many lymph node classification levels

7

level 1

underneath the chin + jaw

Above hyoid bone + body of mandible

In front of posterior boundary of submandibular gland

level 1A

submental nodes

Between anterior bellies of digastric muscles

Level 1B

submandibular nodes

Lateral to 1A nodes

Anterior to back of submandibular glands (in front of them)

level 2

Upper internal jugular nodes

Upper third of IJV, posterior to submandibular glands

From skull base to hyoid bone

Bounded posteriorly by SCM

Level 2A

Lies on all sides of IJV - a, p, m, l

Level 2B

posterior to IJV, separated by fat plane

level 3

Midjugular nodes

Middle of neck, extends from hyoid bone to cricoid cartilage

Lies anterior to sternocleidomastoid muscle

Level 4

Low jugular nodes

bottom of neck, extends from bottom of cricoid cartilage to level of clavicle

Lies lateral to carotid arteries

Also deep cervical nodes - retropharyngeal nodes (behind pharynx)

level 5

Posterior triangle nodes

posterior part of neck, bordered anteriorly by SCM and posteriorly by trapezius

Level 5A

upper posterior triangle nodes

Extends from skull base to cricoid cartilage

Level 5B

Lower posterior triangle nodes

Extends from bottom of cricoid cartilage to clavicle

Also supraclavicular nodes - caudal to clavicle, lateral to carotid artery

Level 6

Upper visceral nodes

Extends from hyoid bone to upper sternum - lies between carotid arteries

underneath level 1, anterior to level 3

level 7

Superior mediastinal nodes

around jugular notch level

Extends from upper sternum to brachiocephalic vein, between carotid arteries