UNIT 11 - EMBRYOLOGY

Nerve fibers

________ within peripheral nerves may be classified as afferent (sensory) or efferent (motor) and as somatic (innervating skin and skeletal muscle) or visceral (innervating vessels and viscera)

Meningocoele

________- protrusion of the meninges through an opening in the vertebral arches to form a cyst beneath the skin.

Meningomyelocoele

________- like menigocoele but both the meninges and the spinal cord protrude.

Neuroblast

________- immature neurons which become the structural and functional cells of the central nervous system; a neuron would only persist if a functional synapse is formed; classification:

Spongioblast

________- develop into the connective tissue of the CNS called neuroglia.

Somatopleure

________ (somatic mesoderm + ectoderm) that forms body wall is distinguished from that forming fetal membranes (chorion and amnion)

Myeloschisis

________- cleft in the neural tube cause by failure of this part to close during neurulation.

Splanchnopleure

________ (splanchnic mesoderm + endoderm) merges bilaterally to form gut and mesentery, differentiated from extra- embryonic yolk sac (and allantois)

Notochord

________- gives rise to the nucleus pulposus, a gel- like substance surrounded by annulus fibrosus found between vertebrae.

Sclerotome

________ (ventromedial region) gives rise to vertebrae, ribs, and endochondral bones at the base of the skull.

Mesoderm blocks

________ located just lateral to the notochord, which induced somite development.

Ventricles

________- spaces wherein CSF- secreting choroid plexuses are found.

neural tube

The early embryo is flat, but the vertebrate body plan features a cylindrical theme- various cylindrical structures (derivatives of the gut, ________, notochord, etc .)

Rostral

________ to the notochord, mesenchyme forms less- developed somites, called somitomeres; these migrate into pharyngeal arches and form muscles of the jaw, face, pharynx, & larynx.

Meninges

________- covering of the CNS; composed of pia mater, arachnoid, and dura mater; derived from neural crest cells.

Spinal cord

________- from the posterior portion of the neural tube (where there is an underlying notochord)

Myotome

________ (intermediate region) gives rise to skeletal muscles of the body.

tube

The ________- shaped embryo undergoes three flexures that make it C- shaped.

D Diplomyelia

________- 2 spinal cords develop beside each other usually in one set or meninges and in one vertebral canal.

Hydranencephaly

________- thin- walled and greatly enlarged lateral ventricle filled with CSF.

A Hypoplasia

________ (aplasia)- reduced or absence of development of one or more segments of the spinal cord.

Myotomes of somitomeres

________ migrate to pharyngeal arches to provide skeletal musculature.

mesenchyme

Head (occipital) somites develop from proliferation of local ________ lateral to the cranial end of the notochord.

Dermatome

________ (lateral region) gives rise to the dermis of skin.

C Syringomyelia

________- abnormal cavitation of the spinal cord.

Myelodysplasia

________- a general term for a malformation of the spinal cord.

Hydrocephalus

________- accumulation of the excessive amount of cerebrospinal fluid in the cranial cavity.

gray matter

Inverted arrangement of white and ________ is brought about by unequal growth of the basal and alar regions of the brain vesicles.

pharynx

The ________ (foregut) develops five bilateral diverticula that internally demarcate the pharyngeal arches.

cylindrical head process

The ________ elongates by additional growth from its base (located in front of the primitive node)

Cerebellar hypoplasia

________ and atrophy- failure of the cerebellum to develop due to destruction of the cerebellar cortex.

Cerebellar abiotrophy

________- premature degeneration of Purkinje cell layer of the cerebellar cortex.

head process

As the ________ elongates upward & forward, a subcephalic pocket (space) is formed ventral to the ________, between the ________ and extra- embryonic tissue.

anterior half dozen

The elongation incorporates the most ________ somites into the future head.

excess accumulation of CSF

B. Hydromyelia- dilation of the central canal due to ________.

Pontine flexure A slight dorsal

________ bending in the rhombencephalon.

visceral efferent

The ________ (autonomic) pathway involves two neurons: 1] a preganglionic neuron that originates in the CNS and 2] a postganglionic neuron l__ocated entirely in the PNS__.

Neuroblast

immature neurons which become the structural and functional cells of the central  nervous system; a neuron would only persist if a functional synapse is formed; classification

Spongioblast

develop into the connective tissue of the CNS called neuroglia

Primary

prosencephalon, mesencephalon, rhombencephalon

Secondary

telencephalon, diencephalon, mesencephalon, metencephalon,  myelencephalon

Spinal cord

from the posterior portion of the neural tube (where there is an underlying notochord)

Meninges

covering of the CNS; composed of pia mater, arachnoid, and dura mater; derived from  neural crest cells

Notochord

gives rise to the nucleus pulposus, a gel-like substance surrounded by annulus  fibrosus found between vertebrae

Ventricles

spaces wherein CSF-secreting choroid plexuses are found

The visceral efferent (autonomic) pathway involves two neurons

1] a preganglionic neuron that originates in the CNS and 2] a postganglionic neuron l__ocated entirely in the PNS__

The bilateral margins of this pocket are lateral body folds

which constitute the continuity between the elevated embryo and the relatively flat extra-embryonic tissue

Cerebellar hypoplasia and atrophy

failure of the cerebellum to develop due to destruction of the cerebellar cortex

Cerebellar abiotrophy

premature degeneration of Purkinje cell layer of the cerebellar cortex

Hydrocephalus

accumulation of the excessive amount of cerebrospinal fluid in the cranial cavity

Hydranencephaly

thin-walled and greatly enlarged lateral ventricle filled with CSF

Myelodysplasia

a general term for a malformation of the spinal cord

a. Hypoplasia (aplasia)

reduced or absence of development of one or more segments of the spinal cord

b. Hydromyelia

dilation of the central canal due to excess accumulation of CSF

c. Syringomyelia

abnormal cavitation of the spinal cord

d. Diplomyelia

2 spinal cords develop beside each other usually in one set or meninges and in one vertebral canal

e. Diastematomyelia

2 spinal cords develop with a partition between them

Myeloschisis

cleft in the neural tube cause by failure of this part to close during neurulation

Meningocoele

protrusion of the meninges through an opening in the vertebral arches to form a cyst beneath the skin

Meningomyelocoele

like menigocoele but both the meninges and the spinal cord protrude