Review Sheet 35: The Lymphatic System and Immune Response, featuring a labeled diagram of the human lymphatic system and related questions.

Let’s go step by step to solve this worksheet.

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Part 1: Match the terms with letters on the diagram

We are given a list of lymphatic system parts and need to match them to the correct letter labeled on the human body diagram.

Here’s how we can think about it:

- Appendix → located in lower right abdomen → matches j
- Axillary lymph nodes → under the arms (armpits) → matches i
- Cervical lymph nodes → neck area → matches b
- Cisterna chyli → sac-like structure at base of thoracic duct, near spine/abdomen → matches k
- Inguinal lymph nodes → groin area → matches g
- Lymphatic vessels → thin lines running throughout body → matches h
- Peyer’s patches → in small intestine → matches f
- Red bone marrow → inside bones like femur or pelvis → matches l
- Right lymphatic duct → drains right upper body → matches m
- Spleen → left side of abdomen, under ribs → matches e
- Thoracic duct → main vessel going up chest → matches c
- Thymus → behind breastbone, above heart → matches d
- Tonsils → back of throat → matches a

✔ All matches look correct based on anatomy.

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Part 2: Why is the lymphatic system one-way, but blood vascular system two-way?

Think of it like this:

- The blood system has arteries that carry blood *away* from the heart and veins that bring it *back*. So it goes out and comes back — that’s “two-way.”
- The lymphatic system only moves fluid *toward* the heart. It starts in tissues, picks up extra fluid and waste, and slowly moves it through vessels until it dumps into big veins near the heart. There’s no loop back — so it’s “one-way.”

Answer:
> It only carries lymph towards the heart.

That’s short and correct!

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Part 3: How do lymphatic vessels resemble veins? And how do lymphatic capillaries differ from blood capillaries?

#### First question: Resemblance to veins

Both lymphatic vessels and veins:
- Have three layers (tunics): inner, middle, outer
- Have valves to prevent backflow (since pressure is low in both systems)

So answer:
> They have three tunics and valves.

✔️ Correct.

#### Second question: Difference between lymphatic capillaries and blood capillaries

Blood capillaries:
- Tight junctions
- No valves
- Carry blood cells and plasma

Lymphatic capillaries:
- Thinner walls
- More permeable (let bigger things in, like proteins or bacteria)
- Have more valves
- Often branch and connect more (anastomose more)

So answer:
> Lymphatics are thinner walled and have more valves and anastamose more.

(Note: “Anastamose” should be spelled “anastomose,” meaning they connect or branch together more.)

But since the student wrote it as-is, and it’s understandable, we’ll keep it unless correcting spelling is required — which it isn’t here.

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## Final Answer:

1. Matching:
- j → appendix
- i → axillary lymph nodes
- b → cervical lymph nodes
- k → cisterna chyli
- g → inguinal lymph nodes
- h → lymphatic vessels
- f → Peyer’s patches
- l → red bone marrow
- m → right lymphatic duct
- e → spleen
- c → thoracic duct
- d → thymus
- a → tonsils

2. The lymphatic system is one-way because it only carries lymph toward the heart. The blood system is two-way because blood flows away from the heart in arteries and returns in veins.

3. Lymphatic vessels resemble veins because they both have three tunics and valves.
Lymphatic capillaries differ from blood capillaries because they are thinner-walled, have more valves, and anastomose more.