Ch. 21: The Lymphatic System V1 P1

Covers the lymphatic system’s functions, how lymph forms and flows, lymphatic vessels and ducts, and what happens when lymph drainage is blocked.

What are the three main functions of the lymphatic system?

Fluid recovery, immunity, lipid absorption

How much capillary filtrate enters the lymphatic system daily?

3 L

What happens to most fluid filtered from blood capillaries?

Reabsorbed at the venule end

What else enters lymph along with excess interstitial fluid?

Plasma proteins, chemicals, pathogens

What can impaired lymph drainage cause?

Lymphedema

Where does lymph trigger immune responses?

Lymph nodes

What are lacteals?

Small-intestine lymphatic capillaries that absorb fat

What are the four broad components of the lymphatic system?

Lymph, vessels, tissues, organs

What distinguishes a lymphatic organ from lymphatic tissue?

An organ has a connective tissue capsule

What is lymph derived from?

Interstitial fluid

How does lymph compare with blood plasma?

Less protein, clear and colorless

Why can intestinal lymph appear milky after a meal?

Absorbed fats

In what direction does lymph flow?

Toward the heart

Where does lymph go after lymphatic capillaries?

Collecting vessels

Where does lymph go after collecting vessels?

Lymphatic trunks

Where do lymphatic trunks drain before lymph enters the veins?

Lymphatic ducts

Why are lymphatic capillaries called terminal lymphatics?

They begin lymph flow

Where are lymphatic capillaries generally absent?

Areas without blood vessels

Why are lymphatic capillaries very permeable?

Overlapping endothelial flaps

How do the endothelial flaps of a lymphatic capillary function?

Open inward, close against backflow

What are the three tunics of a larger lymphatic vessel?

Interna, media, externa

What structures occur in the tunica interna of a lymphatic vessel?

Endothelium, one-way valves

What is in the tunica media of a lymphatic vessel?

Elastic fibers, smooth muscle

What is the tunica externa of a lymphatic vessel?

Thin outer layer

Which blood vessels most closely resemble lymphatic collecting vessels?

Veins

What do lymphatic collecting vessels pass through?

Lymph nodes

How many lymphatic trunks does the lecture identify?

11

What are the two major lymphatic ducts?

Right lymphatic duct, thoracic duct

What regions drain into the right lymphatic duct?

Right thorax, arm, neck, and head

Where does the right lymphatic duct empty?

Right subclavian vein

What regions drain into the thoracic duct?

Both legs, abdomen, and left upper body

About how much of the body does the thoracic duct drain?

3/4

What is the cisterna chyli?

Enlarged abdominal sac beginning the thoracic duct

Where does the thoracic duct empty?

Left subclavian vein

How do lymph pressure and speed compare with venous blood?

Lower pressure, slower flow

What mechanisms propel lymph?

Vessel contractions, muscle pump, arterial pulse, breathing, venous suction

What stimulates contraction of lymphatic vessel walls?

Wall stretching

What prevents backward flow of lymph?

One-way valves

How does exercise affect lymphatic return?

Increases it

How can severe obesity contribute to lymphedema according to the lecture?

Fat can obstruct lymph flow