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    Related Topics

    From Digestive System

    Lips
    Fleshy borders of the mouth that aid in speech and food intake.
    Duodenal Bulb
    Initial section of duodenum closest to the stomach.
    Descending Colon
    Vertical segment of the colon on the left side.
    Lesser Omentum
    Connects stomach and liver.
    Ileum
    Final and longest portion of the small intestine.
    Hepatic Flexure
    Bend between ascending and transverse colon.
    Anus
    Opening through which feces are expelled.
    Uvula
    Dangling soft tissue at the back of the soft palate.
    Tail of Pancreas
    Tapered end of pancreas near spleen.
    Internal Anal Sphincter
    Involuntary muscle around anal canal.
    Main Pancreatic Duct
    Primary duct draining pancreatic juices.
    Peritoneum
    Serous membrane lining the abdominal cavity.
    Jejunum
    Second portion of the small intestine.
    Haustra
    Pouch-like segments of colon.
    Teniae Coli
    Longitudinal muscle bands of colon.
    Sigmoid Colon
    S-shaped final segment of the colon.
    Minor Duodenal Papilla
    Opening for accessory pancreatic duct.
    Round Ligament of Liver
    Remnant of fetal umbilical vein.
    Esophagus
    Muscular tube conveying food from the pharynx to the stomach.
    Gallbladder
    Stores and concentrates bile.
    Hard Palate
    Bony anterior portion of the roof of the mouth.
    Quadrate Lobe
    Small lobe located between gallbladder and round ligament.
    Palatine Tonsils
    Lymphatic tissues on either side of the oropharynx.
    Lower Esophageal Sphincter
    Muscle at the junction of esophagus and stomach.
    Stomach
    Muscular sac that begins digestion of protein.

    Rectum

    Reviewed by our medical team

    Straight section of the colon leading to anus.

    Overview

    The rectum is the final portion of the large intestine and serves as a temporary storage site for feces before defecation. It is a muscular, tubular structure that connects the sigmoid colon to the anal canal. Though part of the digestive tract, the rectum also plays a role in continence and sensory feedback during the defecation process.

    Location

    The rectum is located in the pelvic cavity. It:

    • Begins at the level of the S3 vertebra (continuation of the sigmoid colon)

    • Terminates at the anorectal junction, about 2–3 cm above the anal verge

    • Is situated posterior to the bladder in males and posterior to the vagina and uterus in females

    • Lies anterior to the sacrum and coccyx

    Structure

    The rectum is approximately 12–15 cm long and consists of:

    • Upper third: Covered by peritoneum anteriorly and laterally

    • Middle third: Covered by peritoneum only on the anterior surface

    • Lower third: Located below the peritoneal reflection and entirely extraperitoneal

    Internally, the rectum has:

    • Transverse rectal folds (valves of Houston): Three semilunar mucosal folds that help support fecal mass

    • Muscularis externa: Thick longitudinal and circular muscle layers that aid in peristalsis and continence

    • Mucosa: Lined with columnar epithelium that transitions to squamous epithelium at the anal canal

    Function

    The rectum plays critical roles in:

    • Temporary fecal storage: Holds feces until voluntary elimination is appropriate

    • Defecation reflex: Triggers rectal contraction and internal anal sphincter relaxation when filled

    • Coordination with pelvic floor muscles: Works with the levator ani and anal sphincters to allow or delay defecation

    Physiological Role(s)

    The rectum contributes to digestive physiology and continence through:

    • Sensory detection: Detects stretch from fecal accumulation, signaling the need to defecate

    • Pressure modulation: Helps regulate intra-abdominal pressure during bowel movements

    • Continence preservation: Maintains fecal continence in collaboration with the internal and external anal sphincters

    • Neural regulation: Governed by autonomic (parasympathetic via pelvic splanchnic nerves) and somatic innervation (pudendal nerve)

    Clinical Significance

    The rectum is involved in numerous clinical conditions and is a common site for examination and procedures:

    • Rectal cancer: A common malignancy, especially in older adults; evaluated by colonoscopy and treated via surgery, radiation, or chemotherapy

    • Hemorrhoids: Dilated veins in the rectal or anal region; internal hemorrhoids are typically painless but may bleed

    • Rectal prolapse: Full-thickness protrusion of the rectal wall through the anus; common in older adults and chronic straining

    • Fecal incontinence: Loss of voluntary bowel control due to sphincter damage, nerve injury, or severe constipation

    • Rectal examination: Digital rectal exam (DRE) is essential in assessing prostate size, rectal masses, and sphincter tone

    • Ulcerative colitis: Inflammatory bowel disease that almost always starts in the rectum (proctitis)

    • Rectocele: Herniation of the rectum into the vaginal wall, typically due to pelvic floor weakness

    The rectum’s anatomical position and unique role in both digestion and defecation make it a critical focus in colorectal surgery, gastroenterology, and pelvic floor medicine.

    Did you know? The appendix, once thought to be useless, may play a role in storing beneficial gut bacteria for digestion.