is a cylindrical cord inside the spinal cavity which is about as thick as a pencil.

extends from the foramen magnum of the skull downward (caudally) for about 45 cm (18 inches) to the level of the first lumbar vertebra (L1) in adults.

The upper end of the organ is continuous with the lowermost part of the brain (

Its lower end tapers off as the cone-shaped which is located in the vicinity of the first lumbar vertebra

Extending caudally from the conus is a non-neural fiber called the

filum terminale is attached at?

filum consists of??

It is slightly flattened dorsally and ventrally with two prominent enlargements known as

Emerging from these enlargements are

spinal cord is divided into how many segments

Each pair typically passes through a pair of

cervical

thoracic

lumbar and sacral

coccygeal

The roots of all nerves pass caudally below the conus terminalis (below L1 vertebral level) resemble flowing coarse strands of hair. For this reason, the lumbar and sacral roots are collectively called the

The spinal cord and the roots of its nerves are protected not only by the

is a tough, fibrous membrane that emerges with the filum terminale;

a delicate and transparent membrane which runs caudally to the S2 vertebral level, where it joins the filum terminale

thin highly vascular which is tightly attached to the spinal cord and its roots

Cross-sectionally, the spinal cord has a tiny___.containing ____ and a dark portion of H-shaped or butterfly-shaped "gray matter

It is divided into more or less symmetrical left and right halves by a deep groove called the

Extending out from the spinal cord are the

H-shaped gray matter of the spinal cord has two pairs of columns that form the two vertical bars of the H which are called the

The pairs that form the cross bars of the H is knows as___ which functions in cross reflexes.

which run dorsally and function in afferent input;

which run ventrally and function in efferent somatic output

At each segment of the spinal cord, a pair of nerves branches and exits the

One nerve of the pair exits to the left, entering the

Each nerve has a ventral (anterior) and a dorsal (posterior) root which meet shortly after leaving the spinal cord to form a

spinal nerves are named for their

The numbering of each of the spinal nerve other than the cervical nerves corresponds to the

A short distance after the dorsal and ventral roots join together to form a

the nerve divides into several branches called

what branch of ramus innervate the skin of the back, the skin on the back of the head, and the tissues and intrinsic (deep) muscles of the back.

a ramus innervate the skin tissues, and muscles of the neck, chest, abdominal wall, both pairs of the limbs, and the pelvic area.

innervates the vertebrae, spinal meninges, and spinal blood vessels

are composed of sensory (general visceral afferent) and motor nerve fibers associated with the autonomic nervous system innervating the visceral structure

complex networks of nerves formed by the ventral rami of the spinal nerves (except T2 through T12

complex networks of nerves formed by the ventral rami of the spinal nerves (except T2 through T12

composed of the ventral rami of the spinal nerves C1 through C4. Its branches supply the muscles, skin of the neck, and posterior part of the scalp.

is the most important branch of the cervical plexus is formed by the rami of C3, C4 and C5 These nerves descend into the thorax to innervate the diaphragm

is made up primarily of the ventral rami of C5 to C8 and T1 spinal nerves. This extends downward and laterally, passing behind the clavicle and into the armpit. This plexus give rise to five major nerves that supply a number of neck and shoulder muscles in addition to the entire upper extremity

supplies the anterior arm muscles (biceps brachii) and the skin of the lateral forearm

supplies the deltoid muscle and the skin over the deltoid muscle

supplies the flexor muscles in the anterolateral aspect of the forearm and the hand and the skin in the radial half of the palm

supplies the flexor muscles in the anteromedial aspect of the forearm and the hand and the skin of the same region

is the largest branch of the brachial plexus and supplies the muscle and skin of the posterior aspect of the arm. forearm and hand

composed of fibers of the ventral rami of L1 to L4 nerves. Supplies the motor and sensory fibers to the anterior and lateral abdominal wall, external genitals and the thigh

is the largest branch of the plexus and innervates the iliopsoas and the quadriceps femoris muscles and the skin on the anteromedial aspect of thigh, and

innervates the adductor muscles of thigh and the skin

is composed of fibers of the ventral rami of L4, L5, S1 through S3 spinal nerves. Its branches supply the structures in the buttocks, the perineum and the lower extremity.

the thickest and longest nerve in the body which extends from the pelvic area to the foot and dividing above the knee into the common peroneal and tibial nerves. This nerve supplies the gluteus maximus and the hamstring muscles.

nerve supplies the posterior calf muscles

supplies the lateral and anterior muscles of the leg

innervates the gluteus medius and gluteus minimus, and tensor fascia lata muscles

innervates the gluteus maximus muscle

innervates the voluntary muscles of the perineum, especially the sphincters of the urethra and anus.

formed by the coccygeal nerve (Co1) and sacral nerves S4 and S5. A few nerve filaments supply the skin in the cоссух region.

are the second through twelfth thoracic nerves (T2 to T12). The ventral of the intercostal nerves innervate muscles and skin in the thoracic and abdominal walls.

innervate the intercostalmuscles and the abdominal wall and its overlying skin.

innervate intercostal muscles and the skin on the lateral and anterior thoracic walls.

both sensory and motor fibers that together with the cranial nerves form the

cervical plexus participating

brachial plexus participating

lumbar plexus participating

sacral plexus participating

coccygeal participatint

innervates deltoid

innvervates diaphragm

Hamstring muscles

biceps brachii

coracobrachialis

quadriceps femoris muscles

gastrocnemius

triceps brachii

external intercostals

gluteus maximus

two nerve in sacral

involve a series of responses to receptors in the skin and muscles. - These reflexes help us to move and maintain a correct posture.

occur in certain organs, for example, when the urinary bladder becomes distended and evokes the urge to urinate. - these reflexes also help to regulate blood pressure by affecting the smooth muscle in blood vessels, and also influence the action of glands.