Rectum Flashcards

Explore rectal anatomy, including its pelvic location, curvatures, wall structure, peritoneal relations, vascular supply, and innervation.

Card 1 of 30Question

What is the rectum?

The terminal portion of the large intestine between the sigmoid colon and anal canal.

In This Section

1. What is the rectum?

The terminal portion of the large intestine between the sigmoid colon and anal canal.

2. At approximately which vertebral level does the rectum begin?

At the level of the third sacral vertebra (S3), where the sigmoid colon becomes continuous with the rectum.

3. Where does the rectum terminate?

At the anorectal junction, where it passes through the pelvic diaphragm and continues as the anal canal.

4. What is the approximate length of the adult rectum?

Approximately 12 to 15 cm, with individual variation.

5. Which bony structures lie posterior to the rectum?

The sacrum and coccyx.

6. What are the two principal curvatures of the rectum in the sagittal plane?

The sacral flexure and anorectal flexure.

7. Which muscle maintains the anorectal angle and contributes to fecal continence?

The puborectalis muscle, part of the levator ani.

8. What is the rectal ampulla?

The dilated distal portion of the rectum that serves as a temporary reservoir for feces.

9. What are the transverse rectal folds?

Permanent folds of the rectal wall containing mucosa, submucosa, and circular smooth muscle.

10. What is the middle transverse rectal fold commonly called?

Houston's valve, a prominent transverse rectal fold usually located on the right wall.

11. How does the rectum differ externally from the colon?

It lacks distinct taeniae coli, haustra, and epiploic appendages.

12. How is the outer longitudinal muscular layer arranged in the rectum?

The three taeniae coli spread out to form a continuous longitudinal smooth muscle layer.

13. How does the peritoneal covering of the rectum change from superior to inferior?

The upper third is covered anteriorly and laterally, the middle third anteriorly, and the lower third has no peritoneal covering.

14. Which peritoneal pouch lies between the rectum and urinary bladder in males?

The rectovesical pouch.

15. Which peritoneal pouch lies between the rectum and uterus in females?

The rectouterine pouch, also called the pouch of Douglas.

16. Which reproductive organ lies directly anterior to the middle and lower rectum in females?

The vagina, separated from the rectum by the rectovaginal septum.

17. Which structures lie anterior to the lower rectum in males?

The prostate, seminal vesicles, and ampullae of the ductus deferens, separated by rectovesical fascia.

18. What is the mesorectum?

Fatty connective tissue surrounding much of the rectum and containing its blood vessels, lymphatics, and lymph nodes.

19. What is the mesorectal fascia?

A fascial envelope surrounding the mesorectal fat and associated neurovascular structures.

20. Which artery provides the principal arterial supply to the rectum?

The superior rectal artery, the terminal continuation of the inferior mesenteric artery.

21. From which artery do the middle rectal arteries usually arise?

The internal iliac artery or one of its branches; their presence and origins are variable.

22. Which arteries contribute to the blood supply of the anorectal junction and distal rectum?

The inferior rectal arteries, branches of the internal pudendal arteries.

23. Through which vein does blood from the upper rectum primarily enter the portal circulation?

The superior rectal vein, which drains into the inferior mesenteric vein.

24. Which veins provide systemic venous drainage from the middle and lower rectal regions?

The middle and inferior rectal veins, which drain toward the internal iliac venous system.

25. Why is the rectal venous network an important portosystemic anastomotic site?

It connects superior rectal tributaries of the portal system with middle and inferior rectal tributaries of the systemic circulation.

26. Which lymph nodes primarily receive lymph from the upper rectum?

Pararectal nodes followed by inferior mesenteric lymph nodes.

27. Which lymph nodes receive much of the lymphatic drainage from the middle and lower rectum?

Internal iliac lymph nodes, with additional drainage through pararectal pathways.

28. Which nerves provide parasympathetic innervation to the rectum?

The pelvic splanchnic nerves arising from spinal segments S2 to S4.

29. Through which autonomic plexus does sympathetic innervation reach the rectum?

The inferior hypogastric plexus, with contributions through the superior hypogastric and inferior mesenteric plexuses.

30. What is the anatomical principle of total mesorectal excision in rectal cancer surgery?

Removal of the rectum and mesorectum along the mesorectal fascial plane while preserving adjacent autonomic nerves when possible.