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    Related Topics

    From Digestive System

    Cardia
    Upper opening of the stomach.
    Lips
    Fleshy borders of the mouth that aid in speech and food intake.
    Quadrate Lobe
    Small lobe located between gallbladder and round ligament.
    Esophagus
    Muscular tube conveying food from the pharynx to the stomach.
    Hard Palate
    Bony anterior portion of the roof of the mouth.
    Caudate Lobe
    Lobe of liver near inferior vena cava.
    Palatine Tonsils
    Lymphatic tissues on either side of the oropharynx.
    Haustra
    Pouch-like segments of colon.
    Major Duodenal Papilla
    Opening for bile and pancreatic ducts into duodenum.
    External Anal Sphincter
    Voluntary muscle around anus.
    Lower Esophageal Sphincter
    Muscle at the junction of esophagus and stomach.
    Nasopharynx
    Superior region of pharynx behind the nasal cavity.
    Soft Palate
    Muscular posterior part of the roof of the mouth.
    Lingual Frenulum
    Fold of mucous membrane anchoring the tongue to the floor of the mouth.
    Descending Colon
    Vertical segment of the colon on the left side.
    Jejunum
    Second portion of the small intestine.
    Upper Esophageal Sphincter
    Muscle ring that controls entry into the esophagus.
    Duodenal Bulb
    Initial section of duodenum closest to the stomach.
    Gallbladder
    Stores and concentrates bile.
    Sublingual Glands
    Salivary glands beneath the tongue.
    Common Bile Duct
    Conveys bile from liver and gallbladder to duodenum.
    Ileocecal Valve
    Controls flow from ileum to cecum.
    Greater Omentum
    Fatty fold of peritoneum covering intestines.
    Oropharynx
    Middle region of the pharynx behind the oral cavity.
    Teeth
    Structures in the jaws for mechanical breakdown of food.

    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 is believed to play a role in storing beneficial bacteria for the digestive system.