science

Rectal venous plexus

Rectal venous plexus is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rectal venous plexus rather than just read about it. In short: The rectal venous plexus (or hemorrhoidal plexus) is the venous plexus surrounding the rectum. It consists of an internal and an external rectal plexus.

Key takeaways

Rectal venous plexus belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rectal venous plexus to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rectal venous plexus from memory before moving on to harder problems.

Reference excerpt

The rectal venous plexus (or hemorrhoidal plexus) is the venous plexus surrounding the rectum. It consists of an internal and an external rectal plexus. It is drained by the superior, middle, and inferior rectal veins. It forms a portosystemic (portocaval) anastomosis. This allows rectally administered medications to bypass first pass metabolism. Despite the inclusion of the term "rectal" into the name, the venous plexus is positionally, functionally, and clinically primarily related to the anal canal.

Anatomy The rectal venous plexus consists of an external rectal plexus that is situated outside to the muscular wall, and an internal rectal plexus that is situated in the submucosa/deep to the mucosa of the rectum and proximal anal canal at the anorectal junction.

Internal rectal plexus The internal plexus presents a series of dilated pouches which are arranged in a circle around the tube, immediately above the anal orifice, and are connected by transverse branches. The internal plexus (sources differ) forms/is continuous distally/inferiorly with the hemorrhoids (the vascular cushions of the anal canal).

Venous drainage According to the 42nd edition of Gray's Anatomy (2020), the internal rectal plexus is drained mostly by the superior rectal vein (→inferior mesenteric vein→splenic vein→hepatic portal vein). According to the 8th edition of Clinically Oriented Anatomy (2017), the internal rectal plexus is drains mostly into the superior rectal vein superior/proximal to the pectinate line, and into the inferior rectal veins (→internal pudendal vein→internal iliac vein→common iliac vein→inferior vena cava) around the margin of the external anal sphincter inferior/distal to the pectinate line.

External rectal plexus

Venous drainage The proximal/superior part mostly drains into the superior rectal vein (→inferior mesenteric vein→splenic vein→hepatic portal vein) The middle part drains into middle rectal vein(s) (→internal iliac vein→common iliac vein→inferior vena cava) The distal/inferior part drains into inferior rectal veins (→internal pudendal vein→internal iliac vein→common iliac vein→inferior vena cava)

Structure The veins of the hemorrhoidal plexus are contained in very loose connective tissue, so that they get less support from surrounding structures than most other veins, and are less capable of resisting increased blood-pressure.

Anastomoses The rectal venous plexus represents a portosystemic (portocaval) anastomosis. The transition from drainage into the portal system to drainage into the inferior caval system occurs in the region of the anal columns. It communicates anteriorly with the uterine and vaginal venous plexus in the female, and with the vesical venous plexus in the male.

Clinical significance The internal rectal plexus may prolapse into the anal canal to form pathological internal haemerrhoids; these are often strangulated by the contraction of the anal sphincter, causing ulceration and bleeding. The external rectal plexus may be affected by blood clots (thrombi), resulting in external haemerrhoids.

References This article incorporates text in the public domain from page 676 of the 20th edition of Gray's Anatomy (1918)

Illustrations

Worked examples

Example 1 — a first encounter with Rectal venous plexus

Start with the simplest possible case. Write down what Rectal venous plexus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rectal venous plexus before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rectal venous plexus ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rectal venous plexus

In research: Rectal venous plexus appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rectal venous plexus in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rectal venous plexus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cardiovascular system stubs, Rectum, Veins of the torso, so understanding it makes those chapters shorter.
In everyday life: Look for Rectal venous plexus outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Rectal venous plexus in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rectal venous plexus means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rectal venous plexus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rectal venous plexus in simple terms?

The rectal venous plexus (or hemorrhoidal plexus) is the venous plexus surrounding the rectum. It consists of an internal and an external rectal plexus.

Why does Rectal venous plexus matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rectal venous plexus?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rectal venous plexus.