TBL 28: Cranial fossae, meninges, brain, & pituitary gland

Question 1

What are the three cranial fossas?

Answer 1

Anterior, Middle, & Posterior cranial fossa

Question 2

What bones form the anterior cranial fossa? What does it house?

Answer 2

Bones: Frontal, cribiform plate of ethmoid plate, & lesser wings of sphenoid bone

Contains: Frontal lobe of cerebrum + CN I & II

Question 3

What bones make up the middle cranial fossa? What does it contain?

Answer 3

Bones: Greater wing of sphenoid bone, body of sphenoid bone, Petrous & squamous part of the temporal bone

Contents: temporal lobes of cerebrum, CN III, IV, V (trigeminal ganglion), & pituitary gland

Question 4

What is the hypophyseal fossa?

Answer 4

Found on the body of the sphenoid bone in the middle cranial fossa. It houses the pituitary gland.

Question 5

What is the dorsum sellae?

Answer 5

Square posterior wall of the sphenoid bone behind the hypophyseal fossa

It’s lateral walls contain the pterygoid canals that allow for the greater petrosal & deep petrosal nerves to enter the pterygopalatine fossa

Question 6

What bones form the posterior cranial fossa? Contents?

Answer 6

Occipital + petrous temporal bone

Contains

• Clivus = medulla oblongata + pons of brainstem
• Occipital bone = Cerebellum

Question 7

What is the tentorial notch? Function?

Answer 7

Found within the cerebellar tentorium (which separates the occipital lobes of the cerebrum from the cerebellum) and it allows for the midbrain to pass from the posterior to the middle cranial fossa

Question 8

What’s the purpose of the hypoglossal canal?

Answer 8

These allow CN XII to exit the posterior cranial fossa.

Question 9

Describe the layers of the cranial dura

Answer 9

Bone –> Periosteal layer of dura mater –> Meningeal layer of dura mater –> Arachnoid mater –> Subarachnoid space–> Pia mater

Question 10

What is the difference b/w the periosteal and meningeal layer of the cranial dura?

Answer 10

Periosteum lines the inner surface of the cranium and doesn’t continue into the spinal cord

Meningeal layer lines the brain and continues as the meningeal layer of the spinal cord at the foramen magnum

Question 11

What’s found in the subarachnoid space? Fuction?

Answer 11

CSF in subarachnoid space!

1. Cushions brain
2. Nourishes brain & spinal cord
3. Holds fibrous arachnoid against the dura mater

Question 12

What are dural infoldings?

Answer 12

These are invaginations of the meningeal layer of the cranial dura, where the meningeal layer will separate from the periosteal layer

Question 13

What’s the smallest dural infolding? largest?

Answer 13

Smallest = horizontal sellar diaphragm –> covers the diaphragm

Largest = vertical cerebral falx –> separates the two hemispheres of the cerebrum

Question 14

What allows for a venous pathway for metastasis of distant tumors to the brain?

Answer 14

The internal vertebral venous plexus that connects to the basillar plexus which connects to the inferior petrosal sinus (connecting cavernous sinus & sigmoid sinus)

Question 15

What provides somatic sensory innervation of the dura mater?

Answer 15

CN V1, V2, V3, and peripheral fibers from DRG of C2 & C3

This is why dural pain is always referred pain in the scalp, face, neck, or nasal/oral mucosa

Question 16

Name the three sections of the brain and their subsections

Answer 16

Forebrain (diencephalon, telencephalon)
Midbrain (mesencephalon)
Hindbrain (metencephalon & Myelencephalon)

Question 17

What do the two parts of the forebrain form?

Answer 17

Diencephalon - HIPO (Hypothalamus, Infundibular stalk, Pars nervosa, & optic vesicles)

Telencephaon - Cerebral hemispheres

Question 18

What is the derivative of the mesencephalon?

Answer 18

The midbrain or the cranial part of the brainstem

Question 19

What do the two parts of the hind brain form?

Answer 19

Metencephalon - pons & the cerebrum

Mylencephalon - medulla oblongata

Question 20

Describe the formation of the ventricular system of the brain. Then describe how it flows through the brain and what produces CSF.

Answer 20

Neural tube normally closes at the cranial and caudal neuropores. The lumen then goes and forms the central canals in the spinal cord and also the vascular system in the brain

In the telencephalon, neural tube lumen forms the lateral ventricles. In diencephalon, forms the 3rd ventricle. In mesencephalon, it forms the cerebral aqueduct. Finally, in metencephalon & mylencephalon, it forms the 4th ventricle.

Choroid plexuses are found in the lateral ventricles, and they produce CSF. The CSF flows down to the 3rd ventricle, then through the cerebral aqueduct, and into the 4th ventricle. From there, the fluid goes directly into the central canals of the spinal cord & also to the subarachnoid space of the cerebral hemispheres, cerebellum, & spinal cord

Question 21

What are subarchnoid cisterns?

Answer 21

Along the cranial base, at certain locations, the subarachnoid space gets larger to prevent spinal nerves and arteries at the base from being compressed

Question 22

What are ependyma? What’s its role?

Answer 22

Ependyma is ciliated simple, cubodial epithelium that lines the central canal of the spinal cord & the ventricular system of the brain

It helps to move the CSF along the vascular system

Question 23

What are arachnoid granulations? Functions?

Answer 23

These are mostly found in the superior sagittal sinus but they are protrusions of the arachnoid mater through the meningeal dura. They are covered by endothelium of the sinus.

Allows for CSF to go through the meningeal layer and endothelium into the sinus

Question 24

What are microglial cells?

Answer 24

These act as phagocytes and are the immune cells of the brain and help to clear any CNS debris

PROTECT BRAIN FROM INVADING MICROORGANISMS

Question 25

What are astrocytes?

Answer 25

Stellate cells w/ various functions such as homeostasis These are the most abundant type of glial cells and they are provide support for the endothelial cells of blood vessels

Question 26

Describe the blood-brain barrier and the role of astrocytes

Answer 26

The endothelial cells of blood vessels passing through the brain are linked by tight junctions that prevent any toxins or harmful substances from entering the brain Astrocytes have processes that extend out and contact the outer basement membrane of the vessels. From inside to outside it goes endothelium ==> basement membrane ==> Processes of Astrocytes

Question 27

Describe the course of the vertebral arteries

Answer 27

They branch off of the subclavian artery and they rise up through the transverse foramina of the cervical vertebrae. Near the foramen magnum, they pierce the dura & arachnoid to enter the subarachnoid space of the spinal cord Then, they continues through the foramen magnum into the subarachnoid space of the medulla oblongata At the inferior border of the pons, the two vertebral arteries unite to form the basillar artery

Question 28

What is the cerebral arterial circle of willis?

Answer 28

It's found on the inferior surface of the midbrain A huge anastomosing group involving the basillar artery, internal carotid artery, posterior cranial artery, & anterior cranial artery

Question 29

How does the portal system of the parathyroid gland help regulate the secretion of hormones by the anterior lobe?

Answer 29

Hypothalamus can directly send hormonal cues for secretion to the pituitary via the hypothalamus arteries that go into the superior hypophyseal arteries of the anterior lobe of the pituitary gland. This aids in quick, targeted signals for secretion

Question 30

What hormones are secreted by the anterior pituitary gland?

Answer 30

FLAT PiG F = FSH - regulation of menstrual cycle L = LH - important in production of testosterone & regulation of ovulation A =ACTH - Synthesis & release of cortisol from Adrenal cortex T = TSH - synthesize storage & release of thyroid hormone P = Prolactin - stimulates milk production during pregnancy i = ignore G = Growth hormone - needed to grow big

Question 31

Hormones of the posterior pituitary gland?

Answer 31

Oxytocin = stimulates uterine contractions during childbirth & milk ejection during nursing ADH = acts on the distal convoluted tubule and helps to increase the reabsorption of water to concentrate urine

Question 32

What is the hypothalamohypophyseal? What are the two types of nuclei & what do they each secrete?

Answer 32

There are clusters of secretory neurons in the hyopthalamus that send their axons through the infundibular stalk into the posterior lobe of the pituitary gland There are two types of secretory neurons: paraventricular & supraoptic nuclei. The paraventricular nuclei secrete the oxytocin and the supraoptic nuclei secrete ADH