Anatomy of the rectum

Anatomy of the rectumAnatomical features of the rectum. Functions of the rectum. Blood supply and innervation of rectum
~ 3 min

In this note, we will consider the anatomy of the rectum (rectum).

Rectum (rectum)
Rectum (rectum)

It is the terminal part of the large intestine. Characteristic features, such as haustrae and taeniae, are absent in the rectum. It performs the function of removing the formed fecal masses.

It is located in the pelvic cavity from the level of the left sacro-iliac joint to the perineum.

Rectum (rectum)
Rectum (rectum)
Rectum (rectum)
Rectum (rectum)

Anteriorly from the rectum in men, there are the urinary bladder, seminal vesicles, and prostate.

Rectum (rectum)
Rectum (rectum)

In women, this is the location of the uterus and vagina.

Posteriorly, there is the sacrum.

Laterally, there are iliac vessels.

Rectum (rectum)
Rectum (rectum)

The rectum consists of three parts:

1. Supraampular part (pars supraampullaris)

2. Ampulla (ampulla recti)

Ampulla (ampulla recti)
Ampulla (ampulla recti)

3. Anal canal (canalis analis),

Anal canal (canalis analis)
Anal canal (canalis analis)

which ends with the anus (anus).

Anus (anus)
Anus (anus)

In the sagittal plane, the rectum has 2 flexures:

1. Sacral flexure (flexura sacralis)

Sacral flexure (flexura sacralis)
Sacral flexure (flexura sacralis)

2. Perineal flexure (flexura perinealis)

Perineal flexure (flexura perinealis)
Perineal flexure (flexura perinealis)

The wall of the rectum consists of several layers:

Mucous membrane (tunica mucosa).

Mucous membrane (tunica mucosa)
Mucous membrane (tunica mucosa)

The suprampullar part and the rectal ampulla contain transverse folds (plicae transversales).

Transverse folds (plicae transversales)
Transverse folds (plicae transversales)

There are several longitudinal folds in the anal canal, which are called anal columns (columnae anales).

Anal columns (columnae anales)
Anal columns (columnae anales)

Between them are the recesses called the anal sinuses (sinus anales),

Anal sinuses (sinus anales)
Anal sinuses (sinus anales)

into which the excretory ducts of the anal glands open. Transverse folds called anal valves (valvulae anales) are formed between the inferior ends of the anal columns.

Anal valves (valvulae anales)
Anal valves (valvulae anales)

At the border of the ampulla and the anal canal, there is a small mucous torus called the anorectal line (linea anorectalis).

The second layer of the wall is the submucosa (tela submucosa). The hemorrhoidal venous plexus (plexus venosus haemorrhoidalis) is located here.

Hemorrhoidal venous plexus (plexus venosus haemorrhoidalis)
Hemorrhoidal venous plexus (plexus venosus haemorrhoidalis)

Next follows the muscular layer (tunica muscularis).

Muscular coat (tunica muscularis)
Muscular coat (tunica muscularis)
Muscular coat (tunica muscularis)
Muscular coat (tunica muscularis)

The circular layer of the muscular coat forms the internal anal sphincter (m. sphincter ani internus),

Internal anal sphincter (m. sphincter ani internus)
Internal anal sphincter (m. sphincter ani internus)

while the external anal sphincter (m. sphincter ani externus) is formed by the striated muscles of the perineum.

External anal sphincter (m. sphincter ani externus)
External anal sphincter (m. sphincter ani externus)
External anal sphincter (m. sphincter ani externus)
External anal sphincter (m. sphincter ani externus)

The superior part of the rectum is covered with the peritoneum intraperitoneally, the middle part is covered mesoperitoneally, and the inferior part is covered with adventitia.

Blood supply

  • Superior rectal artery (a. rectalis superior)
  • Middle rectal artery (a. rectalis media)
  • Anterior rectal artery (a. rectalis inferior)

Venous drainage

The venous blood drains through the eponymous veins into the inferior mesenteric vein (v. mesenterica inferior).

Lymph drainage

  • Superior rectal lymph nodes (nodi lymphatici rectales superiores)
  • Middle rectal lymph nodes (nodi lymphatici rectales medii)
  • Inferior rectal lymph nodes (nodi lymphatici inferiores)
  • Pararectal lymph nodes (nodi lymphatici pararectales)
  • Sacral lymph nodes (nodi lymphatici sacrales)
  • Left colic lymph nodes (nodi lymphatici colici sinistri)
  • Inferior mesenteric lymph nodes (nodi lymphatici mesenterici inferiores)
  • Inguinal lymph nodes (nodi lymphatici inguinales), which drain lymph from the anal area.

Innervation

Rectal plexus (plexus rectalis) forms along the course of the rectum.

  1. Afferent innervation is carried out by fibers from the sacral plexus, and the anal region is innervated by the pudendal nerve (n. pudendus).
  2. Sympathetic innervation is provided by fibers of the inferior pancreatic plexus (plexus hypogastricus inferior).
  3. Parasympathetic innervation is carried out by the pelvic splanchnic (nn. splanchnici pelvini).
  4. Efferent innervation of the external anal sphincter is provided by the fibers of the pudendal nerve.
Dictionary

Anatomy of the rectum

Digestive system
systema digestorium
Lips
labium
Oral cavity
cavitas oris
Cheeks
buccae
Tongue
lingua
Pharynx
pharynx
Esophagus
oesophagus
Stomach
ventriculus/gaster
Duodenum
duodenum
Liver
hepar
Pancreas
pancreas
Gallbladder
vesica fellea
Jejunum
jejunum
Ileum
ilium
Caecum
intestinum caecum
Vermiform appendix
appendix vermiformis
Ascending colon
colon ascendens
Transverse colon
colon transversum
Descending colon
colon descendens
Sigmoid colon
colon sigmoideum
Rectum
rectum
Supraampullar part
pars supraampullaris
Rectal ampulla
ampulla recti
Anal canal
canalis analis
Sacral flexure
flexura sacralis
Perineal flexure
flexura perinealis
Transverse folds
plicae transversales
Anal columns
columnae anales
Anorectal line
linea anorectalis
Anal valves
valvulae anales
Anal sinuses
sinus anales
Anal pecten
pecten anales
Anocutaneous line
linea anocutanea
Linea alba
linea alba
Mucous membrane
tunica mucosa
Muscular layer
tunica muscularis
Serous coat or adventitia
tunica serosa / adventitia
Hemorrhoidal venous plexus
plexus venosus haemorrhoidalis
Internal anal sphincter
m. sphincter ani internus
External anal sphincter
m. sphincter ani externus
Mesentery of the rectum
mesorectum
Superior rectal artery
a. rectalis superior
Middle rectal artery
a. rectalis media
Inferior mesenteric vein
v. mesenterica inferior
Superior rectal lymph nodes
nodi lymphatici rectales superiores
Middle rectal lymph nodes
nodi lymphatici rectales medii
Inferior rectal lymph nodes
nodi lymphatici inferiores
Pararectal lymph nodes
nodi lymphatici pararectales
Sacral lymph nodes
nodi lymphatici sacrales
Left colonic lymph nodes
nodi lymphatici colici sinistri
Inferior mesenteric lymph nodes
nodi lymphatici mesenterici inferiores
Inguinal lymph nodes
nodi lymphatici inguinales
Rectal plexus
plexus rectalis
Pudendal nerve
n. pudendus
Inferior pancreatic plexus
plexus hypogastricus inferior
Pelvic splanchnic nerves
nn. splanchnici pelvini
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