---
title: "Blood Components and Blood Vessels"
description: "Plasma, red cells, white cells and platelets each carry a different job, and arteries, veins and capillaries are built for the pressures they meet. Explains why a red blood cell has no nucleus and why"
canonical: https://lightmysky.com/learn/science/blood-components-and-blood-vessels-mt_aWZ2sGXGMn
source: https://lightmysky.com/learn/science/blood-components-and-blood-vessels-mt_aWZ2sGXGMn.md
retrieved: 2026-09-12
---

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# Blood Components and Blood Vessels

Plasma, red cells, white cells and platelets each carry a different job, and arteries, veins and capillaries are built for the pressures they meet. Explains why a red blood cell has no nucleus and why a capillary wall is one cell thick.

Subject: Science · Area: The Human Body · Ages 15 to 16
Page: https://lightmysky.com/learn/science/blood-components-and-blood-vessels-mt_aWZ2sGXGMn

## Ready when they can

- Matches each blood component to what it transports or does.
- Compares wall thickness, lumen size and valves across the three vessel types and ties each to the pressure it carries.
- Explains one structural feature of a red blood cell in terms of carrying more oxygen.

## Lesson: Blood parts and the pipes they travel in

Your blood has four parts and each does one job. Plasma is the liquid that ferries dissolved goods such as nutrients. Red cells haul oxygen using a protein called haemoglobin. White cells hunt germs. Platelets plug leaks by clotting.

Red cells are built for hauling. They have no nucleus, which leaves more room for haemoglobin, so each cell carries more oxygen. White cells defend you by engulfing germs or tagging them with antibodies. Each part matches its job.

Vessels match the pressure they carry. Arteries take blasts straight from the heart, so they have thick muscular walls and a narrow middle. Capillaries are one cell thick so goods swap fast. Veins bring blood back at low pressure, so they have thin walls, a wide middle and valves that stop backflow.

**Tip.** When a question asks why, link the structure to the job. Say what the feature is, then what it allows. No nucleus means more haemoglobin means more oxygen. Thin wall means a short path for diffusion.

**Recap.** Four blood parts split the jobs, and each vessel is built for the pressure it carries.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Heart Structure & Double Circulation](https://lightmysky.com/learn/science/heart-structure-and-double-circulation-mt_TR2oTy9c2M)

## Opens up

- [Heart Rate, Stroke Volume and Cardiac Output](https://lightmysky.com/learn/science/heart-rate-stroke-volume-and-cardiac-output-mt_mjrPFHgvfx)
- [Haemoglobin, the Dissociation Curve and the Bohr Shift](https://lightmysky.com/learn/science/haemoglobin-the-dissociation-curve-and-the-bohr-shift-mt_MmYJArGxrE)