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    Related Topics

    From Digestive System

    Rugae of Stomach
    Internal folds allowing expansion of the stomach.
    Lower Esophageal Sphincter
    Muscle at the junction of esophagus and stomach.
    Anus
    Opening through which feces are expelled.
    Greater Omentum
    Fatty fold of peritoneum covering intestines.
    Mesentery
    Fold of peritoneum anchoring intestines.
    Caudate Lobe
    Lobe of liver near inferior vena cava.
    Peritoneum
    Serous membrane lining the abdominal cavity.
    Mesocolon
    Peritoneal fold attaching colon to posterior wall.
    Ileum
    Final and longest portion of the small intestine.
    Gingiva
    Gums; soft tissue covering the bones of the jaw.
    External Anal Sphincter
    Voluntary muscle around anus.
    Hepatic Flexure
    Bend between ascending and transverse colon.
    Cheeks
    Lateral walls of the oral cavity composed of muscle and fat.
    Epiploic Appendages
    Fat-filled pouches attached to colon.
    Main Pancreatic Duct
    Primary duct draining pancreatic juices.
    Neck of Pancreas
    Short section between head and body.
    Stomach
    Muscular sac that begins digestion of protein.
    Falciform Ligament
    Connects liver to anterior abdominal wall.
    Palatine Tonsils
    Lymphatic tissues on either side of the oropharynx.
    Duodenal Bulb
    Initial section of duodenum closest to the stomach.
    Ileocecal Valve
    Controls flow from ileum to cecum.
    Round Ligament of Liver
    Remnant of fetal umbilical vein.
    Upper Esophageal Sphincter
    Muscle ring that controls entry into the esophagus.
    Nasopharynx
    Superior region of pharynx behind the nasal cavity.
    Jejunum
    Second portion of the small intestine.

    Lips

    Reviewed by our medical team

    Fleshy borders of the mouth that aid in speech and food intake.

    Overview

    The lips (labia oris) are mobile, muscular folds that form the entrance to the oral cavity. Though often considered in aesthetic or speech contexts, they are functionally significant in the digestive system, acting as the primary barrier and controller of food entry into the mouth. They participate in eating, speaking, swallowing, and facial expression, and are richly supplied with nerves and blood vessels, making them highly sensitive.

    Location

    The lips are located at the anterior boundary of the oral cavity. They consist of:

    • The upper lip (labium superius), extending from the base of the nose to the opening of the mouth

    • The lower lip (labium inferius), extending from the mouth opening to the chin

    They meet at the angles of the mouth (labial commissures) and are bordered laterally by the cheeks. Internally, the lips connect to the gums via the labial frenula (superior and inferior).

    Structure

    Each lip consists of several layers:

    • Skin: External surface covered by keratinized stratified squamous epithelium

    • Vermilion border: Transition zone between outer skin and inner mucosa; rich in capillaries, giving lips their red appearance

    • Orbicularis oris muscle: Main muscular component that encircles the mouth and provides movement

    • Subcutaneous tissue: Contains blood vessels, nerves, and minor salivary glands

    • Mucous membrane: Inner lining of the lips composed of non-keratinized stratified squamous epithelium

    The lips are highly vascularized via branches of the facial artery (superior and inferior labial arteries) and innervated by branches of the trigeminal nerve (CN V).

    Function

    The lips play several mechanical and sensory roles in digestion and orofacial behavior:

    • Food intake: Help in grasping and holding food during the initial phase of ingestion

    • Containment: Seal the oral cavity during chewing to prevent food spillage

    • Sensory detection: Detect texture, temperature, and position of food

    • Articulation: Aid in speech production, particularly bilabial sounds (e.g., "p", "b", "m")

    • Expression: Crucial in non-verbal communication through movements and expressions

    Physiological Role(s)

    In the digestive system, the lips contribute to:

    • Pre-oral phase of digestion: Initiate feeding by directing food into the oral cavity

    • Oral competence: Help maintain closure of the mouth to regulate air pressure and saliva retention

    • Sucking mechanism: Essential in infants for breastfeeding and later in creating negative pressure for drinking through straws

    • Tactile feedback: Provide sensory information needed for safe and efficient mastication and swallowing

    Clinical Significance

    The lips are involved in a variety of clinical conditions and procedures:

    • Cleft lip: A congenital defect where the upper lip fails to fuse properly, often associated with cleft palate

    • Herpes labialis: Common viral infection caused by herpes simplex virus (HSV-1), producing cold sores

    • Cheilitis: Inflammation of the lips, which may be due to infection, irritation, or nutritional deficiencies (e.g., B-complex vitamins)

    • Trauma and injury: Lacerations and burns may require careful repair to preserve function and aesthetics

    • Oral cancer: Squamous cell carcinoma can develop, especially in the lower lip due to sun exposure or tobacco use

    • Reconstructive surgery: Lip reconstruction may be necessary after tumor excision or trauma

    • Speech and feeding therapy: Abnormal lip tone or coordination can impact feeding and speech development, especially in children

    Routine examination of the lips is important in dental, ENT, and general medical assessments. Their vascularity and innervation also make them important sites for systemic and local signs of disease.

    Did you know? The average adult human stomach produces about 1.5 liters of gastric juices each day.