Lymphatic Vasculature

Question 1

Function of the endothelium (inner layer) of lymph

Answer 1

Mechanically transports the fluid

Question 2

Structure of lymphatic capillaries

Answer 2

Blind ended (allow fluid to pass through them when pressure is high), fenestrated (large things can enter) capillaries are formed by endothelial cells

Question 3

What do anchoring filaments do?

Answer 3

Pull on endothelial cells to widen gaps when there is increased interstitial fluid

Question 4

How does the unidirectional flow in lymph capillaries work?

Answer 4

Mediated by pressure, lymph drainage into circulation, and peristaltic contraction of vessels

Question 5

Lymph vessels have a smooth muscle layer. What is the function?

Answer 5

Intrinsic reflexive contractility; distension will trigger contraction.
Units between valves are lymphangions which peristaltically contract

Question 6

Lymph flow:

1. Into nodes?
2. Out of nodes?

Answer 6

1. Via afferent vessels (through subcapsular sinsuses by capsule)
2. Via efferent vessels in hilum

Question 7

This is what happens in the lymph node:

Function of macrophages for lymph filtration

What mediates adaptive immunity

Answer 7

Phagocytosis and antigen presentation

B and T lymphocytes

Question 8

1. How do lymphocytes from lymph enter capillaries?

2. How do lymphocytes from blood enter?

Answer 8

1. Through sinuses or enter node tissue

2. Exit specialized veins within node (HEV) to enter node, and can enter sinuses

Question 9

Compare the different intrinsic mechanisms of :

1. Lymph capillaries
2. Lymph vessels

~for lymph movement

Answer 9

1. Anchoring filaments (open/close fenestrations)
2. Reflexive contractility of smooth muscle (lymphangions) triggered by vessel distention; pacemaker cells (spontaneous contractions)

Question 10

5 innervation and humoral (blood borne) signals of lymph vessels

~for lymph movement

Answer 10

1. Sympathetic fibers stimulate smooth muscle (noradrenergic)
2. Adreal catecholamines (NE constricts)
3. Bradykinin, Substance P, NO (blood borne signals that constrict)
4. Cytokines (increase or decrease contractility)
5. Endotoxin (from bacteria) reduces contractility

Question 11

Muscle contractions are important for moving lymph where in the body?

Answer 11

Extremities

Question 12

Inhalation promotes movement of lymph in what direction? Why?

Answer 12

Toward thorax/ducts

Inhalation reduces intrathoracic pressure and increases pressure in abdominopelvic cavity

Question 13

Exhalation promotes drainage from?

Answer 13

Lower extremities
Intrathoracic pressure increases, abdominopelvic pressure decreases

Remember lymph is unidirectional

Question 14

Impaired lymph drainage can lead to increase in

Answer 14

Inflammation (because it helps improve inflammation)

Question 15

Does lymph drain from front to back or vice versa

Answer 15

Lymph drains posterior to anterior (towards thoracic ducts)

Question 16

Drainage in limbs is what direction

Answer 16

Distal to proximal (arms: along subclavian vein to thoracic ducts; legs: through inguinal region)

Question 17

What three things could get in the way of drainage when thoracic ducts exit the superior thoracic aperature?

Answer 17

Sibsons fascia (between rib 1 and transverse process of C7
Anterior scalene
Apical lung pathology

~any obstructions in the limbs can disrupt drainage from those areas as well

Question 18

So how does lymph flow

Answer 18

Lymph fluid is formed in lymph capillaries -> lymph vessels -> lymph nodes -> into thoracic/right lymphatic duct