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    From Nervous System

    Pituitary Gland
    Endocrine gland controlling other hormone glands.
    Substantia Nigra
    Involved in movement and reward.
    Frontal Lobe
    Controls reasoning, planning, movement, emotions, and problem-solving.
    Thoracic Spinal Cord
    Middle portion of the spinal cord.
    Internal Capsule
    White matter structure that carries information to and from the cerebral cortex.
    Arachnoid Mater
    Middle meningeal layer.
    Arbor Vitae
    White matter of the cerebellum.
    Cervical Spinal Cord
    Upper part of the spinal cord.
    Lumbar Plexus
    Nerve network for abdominal wall and thigh.
    Vagus Nerve
    Major parasympathetic nerve supplying thoracic and abdominal organs.
    Tectum
    Dorsal part of midbrain controlling visual and auditory reflexes.
    Cervical Plexus
    Network of nerves supplying neck and shoulder.
    Pia Mater
    Innermost layer of meninges.
    Cerebellum
    Coordinates movement and balance.
    Temporal Lobe
    Involved in auditory perception and memory.
    Cerebral Aqueduct
    Connects third and fourth ventricles.
    Pons
    Connects upper and lower parts of the brain.
    Cerebellar Hemispheres
    Lateral portions of the cerebellum.
    Cerebral Peduncles
    Connect the cerebrum to the brainstem.
    Cingulate Gyrus
    Processes emotions and behavior regulation.
    Fourth Ventricle
    Cavity between brainstem and cerebellum.
    Fornix
    Fiber tract involved in memory.
    Spinal Cord
    Transmits neural signals between brain and body.
    Pineal Gland
    Secretes melatonin to regulate sleep-wake cycles.
    Third Ventricle
    Midline cavity of the diencephalon.

    Sacral Spinal Cord

    Reviewed by our medical team

    Bottom portion of the spinal cord.

    1. Overview

    The sacral spinal cord is the lower portion of the spinal cord, which extends from the lumbar region to the coccyx. It is responsible for transmitting sensory and motor information between the brain and the lower parts of the body, including the pelvic organs, lower limbs, and perineum. The sacral spinal cord is crucial for controlling a variety of functions, such as movement, sensation, and autonomic functions related to bladder and bowel control. It also plays an essential role in sexual function and in maintaining posture and balance. The sacral spinal cord contains nerve roots that form part of the sacral plexus, which provides innervation to the lower extremities and pelvic region.

    2. Location

    The sacral spinal cord is located at the lower end of the spinal cord, just above the coccyx (tailbone). It is positioned in the sacral canal, which is part of the vertebral column and houses the sacral and coccygeal spinal nerve roots. The sacral spinal cord begins at the level of the first sacral vertebra (S1) and extends down to the coccyx, where it forms the cauda equina (a bundle of nerve fibers). The sacral spinal cord is below the lumbar spinal cord and is part of the spinal cord’s transition from the thoracic region to the sacrum. The nerves that emerge from this region serve the lower limbs, pelvis, and perineal region, providing both sensory and motor innervation.

    3. Structure

    The structure of the sacral spinal cord includes several key components that allow it to perform its sensory, motor, and autonomic functions. These include:

    • Gray matter: The sacral spinal cord contains gray matter, which is primarily composed of nerve cell bodies. It is organized into dorsal (sensory) and ventral (motor) horns. The gray matter in the sacral region receives sensory input from the lower limbs and pelvic organs, processes motor commands, and directs these signals to the appropriate muscles and tissues.

    • White matter: The white matter in the sacral spinal cord consists of myelinated axons that transmit sensory and motor information between the spinal cord and the brain. The white matter in the sacral region contains both ascending tracts (which carry sensory information) and descending tracts (which carry motor information). The white matter also includes autonomic fibers that regulate functions such as bladder control and sexual function.

    • Sacral nerve roots: The sacral spinal cord gives rise to five pairs of sacral spinal nerves (S1 to S5). These nerves emerge from the spinal cord and exit through the sacral foramina, which are openings in the sacrum. The sacral nerves form part of the sacral plexus, which provides sensory and motor innervation to the lower limbs and pelvic region. Additionally, some sacral nerves contribute to autonomic functions, such as bladder and bowel control.

    • Cauda equina: The cauda equina, or "horse’s tail," is a bundle of nerve roots that extend beyond the end of the spinal cord (around the L1-L2 vertebrae). It consists of the sacral and lumbar nerve roots and serves the lower limbs and pelvic organs. The cauda equina facilitates the communication between the brain and the lower body, particularly for movement and sensation.

    4. Function

    The sacral spinal cord plays a critical role in motor control, sensory processing, and autonomic functions related to the pelvic region and lower body. Some of the primary functions of the sacral spinal cord include:

    • Motor control: The sacral spinal cord controls the muscles of the lower limbs and pelvic region through the motor neurons that emerge from the ventral horn. These motor neurons transmit signals to the muscles of the legs, feet, and pelvic floor, enabling movement such as walking, running, and maintaining posture.

    • Sensory processing: The sacral spinal cord receives sensory information from the lower limbs and pelvic organs through the dorsal roots. This information includes touch, temperature, pain, and proprioception (sense of body position). The sensory pathways in the sacral spinal cord send this information to the brain for processing and interpretation.

    • Autonomic regulation: The sacral spinal cord is involved in autonomic functions, particularly those related to bladder and bowel control. The parasympathetic fibers of the sacral spinal cord regulate the contraction of the bladder and bowel muscles, enabling urination, defecation, and sexual function.

    • Sexual function: The sacral spinal cord plays a role in sexual function by controlling the muscles involved in sexual arousal and orgasm. It also helps regulate autonomic responses related to sexual function through the parasympathetic nervous system.

    • Reflexes: The sacral spinal cord is involved in various reflexes, such as the patellar reflex (knee-jerk reflex) and the ankle jerk reflex. These reflexes help maintain posture, balance, and coordination during movement, as well as protect the body from injury by providing quick, automatic responses to stimuli.

    5. Physiological Role(s)

    The physiological roles of the sacral spinal cord are essential for maintaining the function of the lower body and pelvic organs. Some of its key physiological roles include:

    • Movement and locomotion: The sacral spinal cord is involved in controlling the muscles of the lower limbs, including the quadriceps, hamstrings, and calf muscles, as well as the muscles of the pelvic floor. These muscles are essential for walking, running, and other motor activities involving the lower body.

    • Posture and balance: The sacral spinal cord helps maintain posture and balance by controlling the muscles of the legs and pelvic region. It coordinates reflexes that keep the body upright and stable during movement, such as when standing or walking.

    • Bladder and bowel control: The sacral spinal cord plays a critical role in the regulation of bladder and bowel function. The parasympathetic fibers in the sacral spinal cord regulate the muscles that control urination and defecation. These functions are vital for maintaining proper elimination of waste from the body.

    • Sexual function: The sacral spinal cord is involved in the autonomic regulation of sexual function. It helps coordinate sexual arousal, ejaculation, and other reproductive processes by controlling the smooth muscle contractions and blood flow to the genital area.

    • Autonomic regulation: In addition to bladder and bowel control, the sacral spinal cord also regulates other autonomic functions, such as blood flow and temperature regulation in the lower limbs and pelvic organs.

    6. Clinical Significance

    The sacral spinal cord is clinically significant because damage or injury to this region can result in a wide range of neurological impairments affecting movement, sensation, and autonomic function. Some key clinical conditions related to the sacral spinal cord include:

    • Sacral spinal cord injury: Injury to the sacral spinal cord, such as from trauma or compression, can lead to partial or complete paralysis (paraplegia) of the lower limbs, loss of sensation, and impairment of bladder and bowel control. The severity of the injury depends on the level of the spinal cord affected and the extent of damage to the neural pathways.

    • Cauda equina syndrome: Cauda equina syndrome occurs when there is compression of the nerve roots at the lower end of the spinal cord, leading to symptoms such as severe lower back pain, weakness in the legs, sensory loss, and loss of bladder or bowel control. This condition requires immediate medical attention and surgical intervention to prevent permanent damage.

    • Spinal cord tumors: Tumors affecting the sacral spinal cord can compress the nerve roots and disrupt normal function. Symptoms may include pain, weakness, numbness, and loss of bowel and bladder control. Treatment often involves surgery, radiation, or chemotherapy to remove or shrink the tumor.

    • Multiple sclerosis (MS): Multiple sclerosis is an autoimmune disease that affects the myelin covering of nerve fibers in the spinal cord and brain. In MS, the sacral spinal cord can be affected, leading to symptoms such as weakness, numbness, and bladder dysfunction.

    • Diabetic neuropathy: In individuals with diabetes, prolonged high blood sugar levels can damage the nerves in the sacral spinal cord, leading to symptoms such as pain, numbness, and loss of function in the lower limbs and pelvic region.

    The sacral spinal cord plays a vital role in regulating movement, sensation, and autonomic functions in the lower body and pelvic organs. Damage to this area can lead to debilitating conditions that affect mobility, bladder and bowel control, and sexual function. Early diagnosis and appropriate treatment are crucial for managing conditions related to sacral spinal cord injury or dysfunction and improving patient outcomes.

    Did you know? The spinal cord sends signals from your brain to other parts of the body and vice versa.