Rectum

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Rectum
deep inguinal lymph nodes
FunctionStore feces prior to defecation
Identifiers
Latinrectum intestinum
MeSHD012007
TA98A05.7.04.001
TA22998
FMA14544
Anatomical terminology]


The rectum (pl.: rectums or recta) is the final straight portion of the

anal verge. The word rectum comes from the Latin rectum intestinum
, meaning straight intestine.

Structure

The rectum lies in front of the sacrum. It lies behind the bladder in males (left), and the vagina and uterus in females (right).

The rectum is a part of the

Latin bottle) is a cavity, or the dilated end of a duct, shaped like a Roman ampulla.[5] The rectum joins with the sigmoid colon at the level of S3, and joins with the anal canal as it passes through the pelvic floor muscles.[5]

Unlike other portions of the colon, the rectum does not have distinct

taeniae coli.[6] The taeniae blend with one another in the sigmoid colon five centimeters above the rectum, becoming a singular longitudinal muscle that surrounds the rectum on all sides for its entire length.[7][6]

Blood supply and drainage

The blood supply of the rectum changes between the top and bottom portions.

The superior rectal artery is a single artery that is a continuation of the inferior mesenteric artery, when it crosses the pelvic brim.[8] It enters the mesorectum at the level of S3, and then splits into two branches, which run at the lateral back part of the rectum, and then the sides of the rectum. These then end in branches in the submucosa, which join with (anastamose) with branches of the middle and inferior rectal arteries.[8]


  • Arteries of the pelvis
    Arteries of the pelvis
  • Blood vessels of the rectum and anus
    Blood vessels of the rectum and anus

Microanatomy

The microanatomy of the wall of the rectum is similar to the rest of the

muscularis propria of two bands of muscle, an inner circular band and an outer longitudinal one.[10] There are a higher concentration of goblet cells in the rectal mucosa than other parts of the gastrointestinal tract.[9]

The lining of the rectum changes sharply at the line where the rectum meets the anus. Here, the lining changes from the column-shaped cells of the rectum to multiple layers of flat cells.[9]

  • Cross-section microscopic shot of the rectal wall
    Cross-section microscopic shot of the rectal wall
  • Dog rectum cross-section (40×)
    Dog rectum cross-section (40×)
  • Microscopic cross-section of the rectum of a dog (400×), showing a high concentration of goblet cells in amongst the column-shaped lining. Goblet cells can be seen as the circular cells with a clear inner material (cytoplasm).
    Microscopic cross-section of the rectum of a dog (400×), showing a high concentration of goblet cells in amongst the column-shaped lining. Goblet cells can be seen as the circular cells with a clear inner material (cytoplasm).

Function

The rectum acts as a temporary storage site for feces. The rectum receives fecal material from the descending colon, transmitted through regular muscle contractions called peristalsis.[11] As the rectal walls expand due to the materials filling it from within, stretch receptors from the nervous system located in the rectal walls stimulate the desire to pass feces, a process called defecation.[11]

An

puborectalis, prevent leakage of feces (fecal incontinence). As the rectum becomes more distended, the sphincters relax and a reflex expulsion of the contents of the rectum occurs. Expulsion occurs through contractions of the muscles of the rectum.[11]

The urge to voluntarily defecate occurs after the rectal pressure increases to beyond 18 mmHg; and reflex expulsion at 55 mmHg. In voluntary defecation, in addition to contraction of the rectal muscles and relaxation of the external anal sphincter, abdominal muscle contraction, and relaxation of the puborectalis muscle occurs. This acts to make the angle between the rectum and anus straighter, and facilitate defecation.[11]

Clinical significance

The inside of a normal human rectum in a 70-year-old, seen during colonoscopy
Retroflexed view of the human rectum seen at colonoscopy showing anal verge
digital rectal exam is conducted to investigate or diagnose conditions including of the prostate
.

Examination

For the diagnosis of certain ailments, a

ultrasound
probe may be inserted into the rectum to view nearby structures such as the prostate.

proctoscope
is another instrument that is used to visualise the rectum.

Body temperature can also be taken in the rectum. Rectal temperature can be taken by inserting a medical thermometer not more than 25 mm (1 inch) into the rectum via the anus. A mercury thermometer should be inserted for 3 to 5 minutes; a digital thermometer should remain inserted until it beeps. Normal rectal temperature generally ranges from 36 to 38 °C (96.8 to 100.4 °F) and is about 0.5 °C (1 °F) above oral (mouth) temperature and about 1 °C (2 °F) above axilla (armpit) temperature.[citation needed] Availability of less invasive temperature-taking methods including tympanic (ear) and forehead thermometers has facilitated reduced use of this method.

Route of administration

Some medications are also administered via the rectum (

Latin: per rectum).[13] By their definitions, suppositories are inserted, and enemas are injected into the rectum.[14][15] Medications might be given via the rectum to relieve constipation, to treat conditions near the rectum, such as fissures or haemorrhoids, or to give medications that are systemically active when taking them by mouth is not possible.[16] People do not tend to like medications administered by this route because of both cultural issues, discomfort, and issues that may affect the medication working, such as leakage.[16]

Constipation

One cause of

diabetes mellitus, as well as severe illness.[17] High calcium levels and low thyroid activity may also cause constipation.[17]

Testing may be carried out to investigate the cause. This may include

anal manometry to measure pressures in the anus and rectum, electrophysiological studies, and magnetic resonance proctography.[17]

In general however, constipation is treated by improving factors such as hydration, exercise, and dietary fibre.

Laxatives may be used. Constipation that persists may require enemas or suppositories. Sometimes, use of the fingers or hand (manual evacuation) is required.[citation needed] Although peristalsis in the colon delivers material to the rectum, laxatives such as bisacodyl or senna that induce peristalsis in the large bowel do not appear to initiate peristalsis in the rectum. They induce a sensation of rectal fullness and contraction that frequently leads to defecation, but without the distinct waves of activity characteristic of peristalsis.[18]

Inflammation

Cancer

Other diseases

Other diseases of the rectum include:

  • Rectal prolapse, referring to the prolapse of the rectum into the anus or external area. This is commonly caused by a weakened pelvic floor after childbirth
  • In the context of
    splenic flexure
    as a watershed region.

Society and culture

Sexual stimulation

Due to the proximity of the anterior wall of the rectum to the vagina in females or to the prostate in males, and the shared nerves thereof, rectal stimulation or penetration can result in sexual arousal.

History

Etymology

English rectum is derived from the Latin intestinum rectum[19] 'straight gut',[20][21] a calque[22][23] of Ancient Greek ἀπευθυσμένον ἔντερον, derived from ἀπευθύνειν, to make straight,[24] and ἔντερον, gut,[24] attested in the writings of Greek physician Galen.[22][23] During his anatomic investigations on animal corpses, Galen observed the rectum to be straight instead of curved as in humans.[22][23] The expressions ἀπευθυσμένον ἔντερον and intestinum rectum are therefore not appropriate descriptions of the rectum in humans. Apeuthysmenon[25] is the Latinization of ἀπευθυσμένον and euthyenteron[26] has a similar meaning (εὐθύς 'straight[24]). Much of the knowledge of the anatomy of the rectum comes from detailed descriptions provided by Andreas Vesalius in 1543.[27]

See also

References

  1. ^ Nosek, Thomas M. "Section 6/6ch2/s6ch2_30". Essentials of Human Physiology. Archived from the original on 2016-03-24.
  2. ^ "12. Colon and Rectum" (PDF), AJCC Cancer Staging Atlas, American Joint Committee on Cancer, 2006, p. 109
  3. ^ .
  4. ^ Wang, Yun Hwa W.; Wiseman, Jeffrey (2023). "Anatomy, Abdomen and Pelvis, Rectum". StatPearls. StatPearls Publishing. Retrieved 24 May 2023.
  5. ^ a b Gray's Anatomy 2016, pp. 1146–7.
  6. ^ a b Gray's Anatomy 2016, p. 1137.
  7. ^ Sneh Agarwal (January–March 2012). "Anatomy of the Pelvic Floor and Anal Sphincters" (PDF). JIMSA. 25 (1).
  8. ^ a b c d Gray's Anatomy 2016, p. 1151.
  9. ^ a b c Wheater's 2013, p. 273.
  10. ^ Wheater's 2013, pp. 252–4.
  11. ^ a b c d Ganong's 2019, p. 492-4.
  12. .
  13. ^ Davidson's 2018, p. 17.
  14. ^ "Definition of ENEMA". www.merriam-webster.com. Retrieved 2020-07-04.
  15. ^ "Definition of SUPPOSITORY". www.merriam-webster.com. Retrieved 2020-07-04.
  16. ^
    PMID 31680970
    .
  17. ^ a b c d e f g h Davidson's 2018, pp. 786–7.
  18. PMID 5717099
    .
  19. ^ Federative Committee on Anatomical Terminology (FCAT) (1998). Terminologia Anatomica. Stuttgart: Thieme.
  20. ^ Schreger CH (1805). "Synonymia anatomica. Synonymik der anatomischen Nomenclatur". In Fürth (ed.). im Bureau für Literatur.
  21. ^ Lewis CT, Short C (1879). A Latin dictionary founded on Andrews' edition of Freund's Latin dictionary. Oxford: Clarendon Press.
  22. ^ a b c Hyrtl J (1880). Onomatologia Anatomica. Geschichte und Kritik der anatomischen Sprache der Gegenwart. Wien: Wilhelm Braumüller. K.K. Hof- und Universitätsbuchhändler.
  23. ^ a b c Triepel H (1910). Die anatomischen Namen. Ihre Ableitung und Aussprache. Mit einem Anhang: Biographische Notizen (Dritte Auflage ed.). Wiesbaden: Verlag J.F. Bergmann.
  24. ^ a b c Liddell HG, Scott R, Jones HS, McKenzie R (1940). A Greek-English Lexicon. Oxford: Clarendon Press.
  25. ^ Kossmann R (1895). "Die gynäcologische Anatomie und ihre zu Basel festgestellte Nomenclatur". Monatsschrift für Geburtshülfe und Gynaekologie. 2 (6): 447–472.
  26. ^ Gabler E, Winkler TC (1881). Latijnsch-Hollandsch woordenboek over de geneeskunde en natuurkundige wetenschappen (2nd ed.). Leiden: A.W. Sijthoff.
  27. .

Sources

External links

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