Folding to the Somatic PNS

surface ectoderm

• epidermis of the skin, hair, nails, sweat and mammary glands

• half of the pituritary gland and tooth enamel

• membranous structure of the inner ear

• lens of the eye

neural tube

• brain and spinal cord

• retina (plate of nerves)

• half of the pituitary gland

neural crest

• segmented cranio-caudally

• ganglia of the peripheral nervous system and is part of the adrenal gland

notochord

gives rise to the nucleus pulposus of the intervertebral discs

somites

give rise to the skeletal muscle and the skeleton except for the skull, dermis of the skin, connective tissue of the body wall

intermediate mesoderm

gives rise to the urogenital system (kidneys, gonads, ovaries); associated with ducts and glands

lateral plate mesoderm

gives rise to the smooth muscle and connective tissue of the viscera, the cardiovascular and lymphatic systems, the spleen, and part of the adrenal gland

endoderm

gives rise to the epithelium lining internal organs (trachea, bronchi, lungs, GI tract, pharynx, thyroid gland, tympanic cavity, auditory tube, tonsils, and parathyroid glands)

transverse folding

somatic motor pathway

carries motor commands from the nervous system to the skeletal muscles

somatic sensory

carries bodily sensations directly to the nervous system

visceral motor pathway (autonomic nervous system)

controls involuntary functions in the smooth muscle, cardiac muscle, and glands (fight or flight; rest and digest)

visceral sensory pathway

carries information from internal organs, glands, and blood vessels to the central nervous system to monitor the body's internal environment

sclerotome

the medial part of a somite; goes on to form the vertebrae

somitomere

the undifferentiated paraxial mesoderm around the neural tube that the cranial half of each sclerotome fuses with during vertebral formation

dermomyotome

the lateral part of a somite; forms the skin and skeletal muscle

expaxial

above the body’s axis and forms the back muscle and skin

hypaxial

below the body’s axis

somatopleure

the body-wall layer (ectoderm and somatic mesoderm)

splanchnopleure

the gut-wall layer (endoderm and splanchnic mesoderm)

coelom

body cavity where the space opens between the somatopleure and the splanchnopleure

allantois

extraembryonic membrane at the caudal end of the embyro

septum transversum

grows around the gut tube to become the diaphragm

mesentery

double-layered membrane that suspends the gut tube in the body cavity

vertebra

a bone of the spinal column built from parts of 2 adjacent sclerotomes

foramen

opening where the gap between vertebrae that a spinal nerve passes through

ganglion

a cluster of nerve cell bodies outside the central nervous system

afferent

carrying a signal towards the central nervous system (sensory)

efferent

carrying a signal away from the central nervous system (motor)

ramus

a branch of a spinal nerve where dorsal and ventral rami are