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    From Nervous System

    Sacral Spinal Cord
    Bottom portion of the spinal cord.
    Cerebellar Hemispheres
    Lateral portions of the cerebellum.
    Parietal Lobe
    Processes sensory information such as touch, temperature, and pain.
    Lateral Ventricles
    Paired brain cavities producing CSF.
    Cerebrum
    Largest part of the brain responsible for voluntary actions, learning, and memory.
    Foramina of Luschka
    Lateral apertures of fourth ventricle.
    Tectum
    Dorsal part of midbrain controlling visual and auditory reflexes.
    Pia Mater
    Innermost layer of meninges.
    Choroid Plexus
    Produces cerebrospinal fluid.
    Midbrain
    Controls visual and auditory systems and body movement.
    Cerebral Peduncles
    Connect the cerebrum to the brainstem.
    Arbor Vitae
    White matter of the cerebellum.
    Ventral Root
    Carries motor information from spinal cord.
    Pituitary Gland
    Endocrine gland controlling other hormone glands.
    Conus Medullaris
    Terminal end of the spinal cord.
    Hippocampus
    Essential for memory formation.
    Pons
    Connects upper and lower parts of the brain.
    Cranial Nerves
    Twelve pairs of nerves that emerge from the brain.
    Cerebral Aqueduct
    Connects third and fourth ventricles.
    Cingulate Gyrus
    Processes emotions and behavior regulation.
    Temporal Lobe
    Involved in auditory perception and memory.
    Third Ventricle
    Midline cavity of the diencephalon.
    Fornix
    Fiber tract involved in memory.
    Epithalamus
    Contains the pineal gland, involved in circadian rhythms.
    Foramen of Magendie
    Median aperture of fourth ventricle.

    Sacral Plexus

    Reviewed by our medical team

    Nerve network for pelvis and lower limb.

    1. Overview

    The sacral plexus is a network of nerves located in the lower back and pelvis. It is formed by the anterior rami of the L4, L5, S1, S2, S3, and S4 spinal nerves. The sacral plexus plays a key role in providing motor and sensory innervation to the lower limbs, pelvis, and perineal region. It is responsible for controlling a variety of movements, including walking, running, and maintaining posture, as well as transmitting sensory information from the legs and pelvic organs. The sacral plexus gives rise to several important peripheral nerves, such as the sciatic nerve, which is the largest nerve in the body and is crucial for lower limb mobility and sensation.

    2. Location

    The sacral plexus is located in the pelvic cavity, specifically in front of the sacrum, which is the triangular bone at the base of the spine. It lies deep within the pelvis, posterior to the pelvic arteries and veins, and within the pelvis major. The sacral plexus is situated at the level of the sacrum and the lower lumbar region, with its roots emerging from the L4 to S4 spinal nerves. It is positioned near the hip joint and lower extremities, providing nerve branches that extend to the lower limbs and pelvic region.

    3. Structure

    The sacral plexus is made up of several nerve roots, branches, and smaller nerve fibers. Its structure is as follows:

    • Roots: The sacral plexus is formed by the anterior rami (branches) of the L4 to S4 spinal nerves. The L4 and L5 roots join to form the lumbosacral trunk, which contributes fibers to the sacral plexus. The S1, S2, S3, and S4 spinal nerves contribute directly to the plexus.

    • Major branches: The major branches of the sacral plexus include:

      • Sciatic nerve (L4-S3): The sciatic nerve is the largest nerve in the body and is the primary nerve of the lower limb. It innervates the posterior thigh, the entire leg below the knee (except for the medial leg), and the foot. It is responsible for motor control and sensation in the lower limb.

      • Pudendal nerve (S2-S4): The pudendal nerve supplies motor and sensory innervation to the perineal muscles, external genitalia, and anus. It is involved in functions such as bladder control, sexual function, and defecation.

      • Superior gluteal nerve (L4-S1): This nerve innervates the gluteus medius, gluteus minimus, and tensor fasciae latae muscles, which are responsible for hip abduction and stabilization during walking.

      • Inferior gluteal nerve (L5-S2): This nerve innervates the gluteus maximus muscle, which is responsible for hip extension and external rotation.

      • Posterior femoral cutaneous nerve (S1-S3): The posterior femoral cutaneous nerve provides sensory innervation to the skin of the posterior thigh, buttock, and perineum.

      • Nerve to quadratus femoris (L4-S1): This nerve innervates the quadratus femoris and inferior gemellus muscles, which are involved in hip joint rotation.

      • Nerve to obturator internus (L5-S2): This nerve innervates the obturator internus muscle, which is involved in the lateral rotation of the hip joint.

    • Smaller branches: In addition to the major branches, the sacral plexus gives rise to smaller branches that innervate muscles of the pelvic floor, hip, and leg, as well as the skin of the perineum and lower leg.

    4. Function

    The sacral plexus is responsible for transmitting both motor and sensory information, playing a crucial role in the movement and sensation of the lower limbs and pelvic region. Some of its key functions include:

    • Motor function: The sacral plexus controls the motor functions of the lower limbs, including the muscles involved in walking, running, and maintaining balance. It innervates the gluteal muscles, quadriceps, hamstrings, and muscles of the lower leg and foot, allowing for coordinated movement and gait. It also controls pelvic floor muscles involved in defecation, urination, and sexual function.

    • Sensory function: The sacral plexus provides sensory innervation to the skin and tissues of the lower limbs, pelvis, and perineum. It conveys sensory information such as touch, pain, temperature, and proprioception from these areas to the brain. It helps individuals sense the position of their body in space and respond to external stimuli.

    • Reflexes: The sacral plexus is involved in several reflex activities, such as the patellar reflex (knee-jerk) and the ankle jerk reflex. These reflexes are essential for maintaining posture and reacting to changes in body position.

    • Autonomic functions: The sacral plexus plays a role in autonomic functions, particularly those related to the pelvic region. It helps regulate bladder and bowel function and contributes to sexual arousal and function through the pudendal nerve.

    5. Physiological Role(s)

    The physiological roles of the sacral plexus are essential for the normal function of the lower body and pelvic region. Some of these roles include:

    • Movement and locomotion: The sacral plexus coordinates the movement of the lower limbs, including hip extension, knee flexion, and foot movement. It is essential for walking, running, climbing, and other motor activities involving the legs.

    • Balance and posture: The sacral plexus helps maintain balance by controlling muscles involved in maintaining an upright posture, such as the gluteus medius and minimus, and by providing sensory feedback from the legs to the brain for coordination and balance.

    • Bladder and bowel control: The sacral plexus plays a vital role in the regulation of bladder and bowel function. It coordinates the muscles of the pelvic floor to allow for voluntary control over urination and defecation.

    • Sexual function: The sacral plexus is involved in sexual function, including arousal and ejaculation. The pudendal nerve, in particular, is responsible for sensations in the genital area and the motor control required for sexual activity.

    • Postural reflexes: The sacral plexus contributes to postural reflexes, such as maintaining balance during movement and correcting body position in response to external forces or changes in posture.

    6. Clinical Significance

    The sacral plexus is clinically significant due to its role in motor and sensory functions of the lower body and pelvic region. Damage to the sacral plexus or its branches can result in a range of neurological and functional impairments. Some key clinical conditions related to sacral plexus dysfunction include:

    • Sacral plexopathy: Sacral plexopathy refers to damage or injury to the sacral plexus, often caused by trauma, compression, or surgical interventions. Symptoms include weakness, pain, and sensory loss in the lower limbs and pelvic region. It can also cause difficulties with bladder and bowel control.

    • Sciatica: Sciatica refers to pain, numbness, or weakness along the path of the sciatic nerve, which is the largest nerve arising from the sacral plexus. Sciatica can be caused by compression or irritation of the sciatic nerve and is often characterized by radiating pain in the lower back, buttocks, and down the leg.

    • Foot drop: Foot drop is a condition in which an individual has difficulty lifting the front part of the foot, often caused by damage to the peroneal nerve, which is a branch of the sacral plexus. This condition can make walking difficult and may be accompanied by muscle weakness or paralysis in the lower leg.

    • Pudendal nerve dysfunction: Dysfunction of the pudendal nerve, which arises from the sacral plexus, can lead to symptoms such as pelvic pain, sexual dysfunction, and problems with bladder or bowel control. Pudendal neuralgia, a chronic pain condition, can result from compression or irritation of this nerve.

    • Cauda equina syndrome: Cauda equina syndrome occurs when there is compression of the nerve roots in the lower spinal cord, including those that form the sacral plexus. This condition can cause severe symptoms, including urinary retention, bowel incontinence, and lower limb paralysis. It is a medical emergency requiring prompt treatment.

    The sacral plexus is essential for lower body movement, sensation, and autonomic function. Damage or dysfunction in this region can lead to significant impairments in mobility, sensation, and pelvic control. Early diagnosis and intervention are critical for managing sacral plexus-related disorders and improving patient outcomes.

    Did you know? The cerebellum, located at the back of the brain, coordinates voluntary movements such as posture and balance.