Development of the Brain, spinal cord and cranial nerves

Question 1

What does the ectoderm give rise to?

Answer 1

The skin, CNS (Brain and spinal cord), PNS *peripheral nerves) pituitary gland, teeth and nose mucosa

Question 2

What does the mesoderm give rise to?

Answer 2

GI tract, heart, RBC, skeletal muscles, heart and mesenchyme cells that give rise to the bone and cartilage.

Question 3

What does the endoderm give rise to?

Answer 3

Digestive tract and Lungs

Question 4

How does the mesoderm form?

Answer 4

During gastrulation process on day 16. The cells of the ectoderm in contact with the endoderm proliferate and move across to form the primitive streak which confirms bilateral symmetry in the embryo. The proliferating cells invaginate into the cephalic end of the primitive streak called the primitive node and displace the hypoblast which forms the mesoderm.

Question 5

What is the primitive node?

Answer 5

The primitive node is at the cephalic end of the primitive streak.

Question 6

What is the primitive pit?

Answer 6

The slightly elevated area around the primitive node called the primitive pit.

Question 7

Where does the nervous system develop from the trilaminar disc?

Answer 7

The ectoderm.

Question 8

What is the process of neuralation?

Answer 8

Notochord stimulates the ectoderm differentiates-> neuroectoderm differentiates -> neural epithelial cells which form a thickened layer called the -> neural plate which changes shape and folds inward to create neural folds with a neural groove. The neural groove -> neural tube when the neural folds converge. Before the neural folds fuse, parts of the neural tube separate and migrate as neural crest cells to form the spinal cord and cranial nerves

Question 9

What does the neural crest give rise to?

Answer 9

The PNS(cranial nerves and spinal nerves) and the spinal cord.

Question 10

What does the neuroectoderm give rise to?

Answer 10

Tissue of the nervous system.

Question 11

What does the paraxial mesoderm give rise to?

Answer 11

The somites which are the dermis, skeletal muscle, cartilage tendons and vertebrae

Question 12

What are somites?

Answer 12

Precursor mesodermal paired cells on either side of the notochord that gives rise to the dermis, skeletal muscle, cartilage, tendons and vertebrates

Question 13

How does the spinal cord develop?

Answer 13

The neural tube has 3 zones: the matrix, marginal and mantle zone. The marginal zone gives rise to cells called neuroblasts and glioblasts which migrate into the mantle zone and form two plates.
The alar plate forms the dorsal side of the neural tube and contains the afferent sensory neurons which later becomes the grey matter of the spinal cord. The basal plate forms the ventral portion of the neural tube which contains the efferent motor neurons and forms the white matter of the spinal cord. The basal and alar plate are separated by the sulcus limitans. The sulcus limitans extends from the spinal cord to the rostral mdbrain.

Question 14

What is the ventral medial fissure?

Answer 14

The ventral horn of the spinal cord formed by the basal plate bulge.

Question 15

What is the dorsal septum?

Answer 15

The dorsal horn of the alar plate fusing together.

Question 16

What is the meninges?

Answer 16

The three-layer membrane that protects both the spinal cord and brain. Inner layer is pia mater, middle layer is a web like structure called the arachnoid and the tough outer layer is the dura mater.

Question 17

What is the dura mater?

Answer 17

Tough Outer layer of tissue which protects the brain and spinal cord. It arises from the paraxial mesoderm that surrounds the neural tube

Question 18

What is the pia mater?

Answer 18

Inner delicate layer directly surrounding the brain and spinal cord. It arises from neural crest cells.

Question 19

What is the arachnoid mater?

Answer 19

Web like tissue which forms the middle layer of the meninges. It arises from neural crest cells.

Question 20

What is the conus medullaris?

Answer 20

Terminal end of the spinal cord at level L1 but the neural tube continues beyond this

Question 21

How do the cranial nerves develop?

Answer 21

Cranial nerves derive from neural crest cells and thickened patches of ectoderm called the ectodermal placodes.
Neural crest cells separated from the neural tube and ectodermal patches break away from the ectoderm and they migrate through the embryo in the cranium and trunk and divide into the cranial nerves, pharyngeal arches, skeletal tissue and connective tissue components, sensory ganglia of cranal nerve 5, 6, 7, 9 and 10 AND THE

Question 22

What cranial nerve does pharyngeal arch 1 give rise to?

Answer 22

Cranial nerve 5- trigeminal nerve

Question 23

What cranial nerve does pharyngeal arch 2 give rise to?

Answer 23

Facial nerve- cranial nerve 7

Question 24

What cranial nerve does pharyngeal arch 3 give rise to?

Answer 24

Glossopharyngeal nerve -cranial nerve 9

Question 25

What cranial nerve does pharyngeal arch 4 and 6 give rise to?

Answer 25

Vagus nerve

Question 26

What are the special sensory cranial nerves?

Answer 26

Olfactory, optic and vestibulocochlear

Question 27

WHat is the somatic efferent nerves?

Answer 27

Trochlear, abducens, hypoglossal and oculomotor nerve which are homologous with the ventral roots of the spinal nerves

Question 28

What do neural crest cells give rise to in the trunk?

Answer 28

Schwann cells, chromaffin cells of adrenal medulla and sympathetic chain ganglia.