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Y2S1 ANATOMY > Anatomy of the hypothalamus and the pituitary > Flashcards

Anatomy of the hypothalamus and the pituitary Flashcards

1
Q

What is the origin of the hypothalamus?

A
  • First we have the BRAIN, which is formed of:

1) FOREBRAIN

  • The forebrain will then differentiate into:

1A) TELENCEPHALON

2A) DIENCEPHALON, which will form the:

  • THALAMUS
  • HYPOTHALAMUS

2) MIDBRAIN

3) HINDBRAIN

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2
Q

What is THE DIENCEPHALON?

A
  • It is a relay (where neurons intercross) between the brainstem and the cerebral cortex, it has:

1) Posterior structures:

  • Epithalamus
  • Thalamus (located on both sides of the third ventricle with an intra-thalamic connection)
  • Metathalamus

2) Ventral (anterior) structures:

  • Hypothalamus (located anteriorly and inferiorly to the thalamus)
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3
Q

In the posterior aspect of the diencephalon, what forms the epithalamus?

A

1) Pineal gland

2) Habenular Nuclei

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3
Q

What forms the metathalamus of the posterior aspect of the diencephalon?

A

The swellings of the posterior aspect of the thalamus known as Geniculate bodies

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3
Q

Where is the thalamus located?

A

On both sides of the 3rd ventricle with a inter-thalamic connection

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3
Q

Where is the hypothalamus connected?

A
  • It is located at the base of the brain in the inter-peduncular fossa “between the peduncles of the midbrain”, above the optic chiasm
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4
Q

What is the cerebral peduncle of the midbrain?

A
  • It is a V-shaped structure from the midbrain, where there is a space between the two peduncles (stems) called the inter-peduncle fossa, where the infundibulum comes out
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5
Q

What is the first cranial nerve?

A

Olfactory nerve

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6
Q

What form the optic chiasm?

A

The two optic nerves (1 for each eye “cranial nerve 2”), they will go back and form it, where you will find the pituitary gland behind it

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7
Q

What is the second cranial nerve?

A

Optic nerve

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8
Q

Where is the 3rd ventricle located?

A
  • The hypothalamus lies under the thalamus and they both sandwich the 3rd ventricle.
  • The 3rd ventricle is in the interpendicular fossa of the cerebral pendicles.
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9
Q

What is the superior relation of the hypothalamus?

A

The thalamus, where we can find the hypothalamic sulcus separates it from the thalamus

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10
Q

What is the inferior relation of the hypothalamus?

A

We find the midbrain posteroinferior to it

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11
Q

What is the blood supply of the hypothalamus?

A

Circle of Willis

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12
Q

What are the functions of the hypothalamus?

A

It has nuclei (cell bodies) that control the:

1) Hunger/Satiety
2) Thirst
3) Sexual behaviour
4) Temperature regulation
5) Sleep and cardiac rhythm

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13
Q

What is a neuroendocrine cell?

A

They are cells of the nervous system that act as endocrine cells (hypothalamus), secreting hormones into the median eminence, which is rich in capillaries, from those blood vessels they:

1) Head to the anterior pituitary (“ADENOHYPOPHYSIS” where cells from the oral cavity ascended)

2) RELAYED DIRECTLY TO THE POSTERIOR PITUITARY (“Neurohypophysis”, neural tissue with direct contact through the nerves)

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14
Q

What are the different hypothalamic nuclei?

A
  • Pre-workout for Strech Treadmill Mumba

1) Preoptic Zone: Preoptic Nucleus:

  • Lateral preoptic nucleus
  • Medial Preoptic Nucleus

2) Supraoptic zone:

  • Supraoptic
  • Paraventricular
  • Periventricular
  • Lateral hypothalamic

3) middle Tubular zone:

  • Lateral hypothalamic
  • Arcuate
  • Periventricular

4) Posterior region:

  • Mamillary nucleus
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15
Q

Where is the preoptic area located? and what nuclei does it contain?

A
  • Close to the third ventricle
  • It has the:

1) Lateral preoptic Nuclei

2) Medial preoptic nuclei

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16
Q

Where is the anterior supraoptic region located? and what nuclei does it contain?

A
  • The Anterior/Supraoptic region is located between the preoptic area and the stem

It has the:

1) Periventricular Nucleus (around the third ventricle)

2) Paraventricular Nucleus (On the either side of the 3rd ventricle)

3) Supraoptic Nucleus

4) Lateral Hypothalamic nucleus (it extends and it is seen in the middle “controls the hunger & satiety”)

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17
Q

Where is the middle tubular region located? and what nuclei does it contain?

A

It has the:

1) Lateral hypothalamic nucleus (extends in the anterior region “controls hunger and satiety”)

2) Periventricular nucleus (located around the 3rd ventricle)

3) Arcuate Nucleus

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18
Q

What is the function of the preoptic nucleus?

A
  • It contains the lateral and medial nucleus which regulates the release of gonadotropic hormones (LH, FSH) from the adenohypophysis
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19
Q

What is the median eminence?

A

It is an area at the base of the hypothalamus that contains a capillary bed, where the hypothalamic neurosecretory fibers discharge their releasing factors into

The axon terminal of the preoptic nucleus terminates into the blood vessel here

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20
Q

What is the function of the anterior/supra-optic region?

A
  • It contains the paraventricular, supraoptic, and the lateral hypothalamic

1) The lateral hypothalamic, stimulated by ghrelin, it induces eating

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21
Q

Damage to which nuclei leads to anorexia and starvation (failure to thrive)?

A
  • Lateral injury makes you Lean

The LATERAL HYPOTHALAMIC NUCLEUS OF THE ANTERIOR/SUPRAOPTIC REGION

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22
Q

wHAT IS THE FUNCTION OF THE SUPRAOPTIC & PARAVENTRICULAR NUCLEUS?

A
  • SAD POX

1) The supraoptic secretes ADH

2) The Paraventricular secretes Oxytocin

  • The axons from the hypothalamus go directly into the posterior pituitary through the infundibular stalk, and it does not end in the median eminence
  • The terminal ends of those axons are called “Herring Bodies”
23
Q

Lesion to which of the nucleus causes diabetes insipidus?

A

To the supraoptic and paraventricular, found in the anterior/supra-optic region

24
Q

What is a Herring boies?

A

They are the terminal axons of the anterior/supraoptic nuclei that end in the posterior pituitary

25
Q

What are the functions of the middle/tubular region?

A

1) Arcuate/infundibular nucleus: Contains neurons that produce the releasing and inhibiting hormones of the hypothalamic (GHRH most imp)

  • The arcuate nucleus axons ends in the median eminence, releasing its hormones into the blood vessels

2) The periventricular nucleus releases the thyrotropin-releasing hormone

26
Q

Describe the pituitary gland

A
  • A small oval structure (1cm in diameter) that is named as the master endocrine gland
27
Q

Where is the pituitary gland located?

A
  • In the middle of the cranial fossa, inside the sella turcica (hypophyseal fossa) of the sphenoid bone
  • The sella turcica is a saddle-like depression for the pituitary gland
  • It is covered by the dura matter only (with no arachnoid or pia matter
  • In the roof there is a hole for that passage of the infundibular stalk
28
Q

Why is the arachnoid and pia matter not present in the covering of the pituitary gland?

A

1) Because the CSF is located in the subarachnoid space which would elicit intracranial pressure

2) The pituitary gland would be compressed, which might lead to an empty sella turcica syndrome (where the pituitary gland is shrunk and disappears)

29
Q

What is a sphenoid bone?

A

It is a butterfly-like structure that has a body, a lesser wing (separates the middle cranial fossa from the anterior cranial fossa), and a greater wing that has openings

30
Q

What is the superior orbital fissure?

A

It is an opening between the lesser and greater wings of the sphenoid bone

31
Q

What are the nerves that pass through the superior orbital fissure?

A

1) 3rd cranial nerve: The oculomotor nerve

2) 4th Cranial nerve: Trochlear nerve

3) 5th cranial nerve: The trigeminal nerve

32
Q

What are the branches of the trigeminal nerve?

A

1) Maxillary branch, this branch does not pass through the superior orbital fissure but rather the foramen rotundum

2) Mandibular branch (foremen ovale)

3) Ophthalmic Branch

33
Q

Tumors that spread to which aspect of the sphenoid bone will compress the eye nerves (passes through the superior orbital fissure)

A

The ones that spread up and anterior

34
Q

What are the subdivisions of the pituitary gland?

A

1) Anterior lobe (adenohypophysis)

1a) Pars distalis/anterior: It is a true gland that contains endocrine cells and secretes hormones

1b) Pars intermedia: Colloid-filled cysts and cells that secrete melanocyte-stimulating hormone (MSH)

1c) Pars tuberalis: It surrounds the median eminence and the infundibular stem of the neurohypophysis and it contains portal venules of the hypophyseal portal system

2) Posterior lobe (neurohypophysis)

  • Formed of three parts which is connected to the hypothalamus via the hypothalamo-hypophyseal tract, it stores hormones secreted by the hypothalamic nuclei

1) Pars nervosa
2) Infundibular stem
3) Median eminence

35
Q

What structures secrete melanocyte-stimulating hormones?

A

The pars intermedia of the anterior lobe

36
Q

What is the infundibulum?

A
  • It consists of an infundibular stem, the hypophyseal portal vessels, and the pars tuberalis
  • The stem cells carry neural fibers from the hypothalamus to the pars nervosa (posterior pituitary
  • The infundibular stalk is what actually connects the pituitary gland to the brain
37
Q

What is the median eminence?

A
  • The point where the hypothalamic axons end
  • It is an area at the base of the hypothalamus that contains a capillary bed into which the hypothalamic neurosecretory fibers discharge their releasing factors
38
Q

Describe the development of the adenohypophysis (anterior pituitary)

A

1) It develops from a finger-like ectoderm that grows up from the roof of the mouth “the ectoderm of the oropharynx” (Rathke’s pouch) towards the base of the diencephalon

1) Anterior wall: Pars distalis
2) Posterior wall: Pars intermedia
3) Colloid follicle (their remnants) is present between the distalis and intermedia

39
Q

The anterior wall of the rathke’s pouch forms which structure of the anterior pituitary?

A

The pars distalis

40
Q

The posterior wall of the rathke’s pouch forms which part of the anterior pituitary?

A

The pars intermedia

41
Q

What forms the infundibulum?

A

The infundibular stem and the pars tuberalis (the pars tuberalis wraps around and anchors the infundibular stem)

42
Q

Describe the development of the neurohypophysis

A

It develops from the down growth evagination, from the diencephalon towards rathke’s pouch (from the neuroectoderm)

43
Q

Describe the process of pituitary development

A

1) The adenohypophysis starts bulging from the oral cavity upwards, it then detaches from the pharynx, the nasopharyngeal tonsils are located at this point where you will see a small depression that has gone up, it will then wrap itself around the posterior lobe

2) The neurohypophysis is from the nervous tissue that develops downwards

44
Q

What is a congenital anomaly that can arise in the pituitary gland?

A

Craniopharyngiomas

45
Q

What is a craniopharyngioma?

A

If the Rathke’s pouch is left in the roof of the nasopharynx (as an accessory anterior lobe in the pharyngeal wall/pharyngeal hypophysis) it may give origin to tumors called craniopharyngiomas inside the sphenoid bone

  • Basically, it grows and grows to it reaches the roof then it ruptures
46
Q

What are the relations of the pituitary gland?

A

1) Superiorly: Diaphram sellae

2) Inferiorly: Sphenoid air sinus

3) Anterio-superiorly: Optic chiasm (pituitary overgrowth can cause visual symptoms)

4) Posteriorly: Dorsum seller, basilar artery, and pons mamillary bodies

5) Laterally: Cavernous sinuses and its contents

47
Q

What are the complications that can arise from the overgrowth of the pituitary gland?

A

1) Breaks down into the sinuses

2) Compression of the basilar artery which is present posteriorly

3) Goes up and compresses the optic chiasm which can cause blurred vision

48
Q

Describe the structure of the dura mater

A

1) Diaphragm sellae: It separates the pituitary gland from the hypothalamus, The infundibulum passes through the central aperture of the diaphragm sella

2) It surrounds the pituitary gland and it is adherent to it

49
Q

Why don’t we have a subdural and subarachnoid space?

A

Because the gland should be protected from the effects of high CSF pressure

50
Q

What is the empty sella syndrome?

A

When the central aperture is large, the pia and arachnoid can herniate through it into the pituitary fossa, and CSF can accumulate compressing and atrophying the gland

51
Q

What is the cavernous sinus?

A
  • The mother of all sinuses
  • A common site of thrombosis in case of a spread to a face infection
  • The internal carotid artery is located close to the cavernous sinus
  • Infection to the cavernous sinus can cause exophthalmos
  • The internal carotid artery is near the cavernous sinus, In case of an infection, the artery may rupture open and a fistula between the sinus & artery occurs (left to right shunt) Instead of leaving, blood goes back to the eye through the veins
52
Q

What is an adenoma?

A
  • It is the commonest tumor of the pituitary gland (chromophobe cells), which compresses the structures that are related to the gland
53
Q

What are the signs and symptoms of an adenoma to the pituitary gland?

A

1) Pressure on the cavernous sinus: Exophthalmos and paralysis of the muscles of the eyeball that are supplied by the 3rd, 4th, and 6th cranial nerves

2) Pressure on the central part of the optic chiasm: Loss of right and left temporal field vision

3) Downward growth of the tumor: Break sella turcica (enlargement of the hypophyseal fossa, seen as a ballooning of the sella turcica in a plain X-ray)

54
Q

What connects the neurohypophysis (posterior pituitary) to the hypothalamus?

A
  • It receives axonal projections from the neurons that have cell bodies in the supraoptic and periventricular nuclei of the hypothalamus which synthesizes oxytocin and ADH
  • The hypothalamo-hypophyseal axon tracts project into the neurohypophysis where the axon terminal “Herring bodies” secrete oxytocin and ADH into the venous sinusoid
  • Pituicytes are found (provide support and nutrients)
  • Herring bodies are the terminal parts of the axons
55
Q

What connects the adenohypophysis (anterior pituitary) to the hypothalamus?

A
  • It communicates with the hypothalamus through the portal blood vessels, where the axons project in the median eminence and the hormones are secreted into the capillary bed there
  • The cell bodies located in the nuclei of the hypothalamus secrete releasing and inhibiting hormones to it
56
Q

Describe the blood supply of the pituitary gland

A

There are two sources of blood:

1) Arterial

1a) Superior hypophyseal

  • Supplies the infundibulum
  • Supplies the anterior pituitary by forming a capillary network where the vessels go downwards and form sinusoid (hypophyseal portal system)

1b) Inferior hypophyseal (supplies the posterior lobe of the pituitary gland)

2) Portal venous

  • The hypophyseal veins drain into the cavernous sinus
57
Q

How can we excise a pituitary tumor?

A
  • Transnasal Trans-sphenoidal approach, where we approach the gland through the roof of the nasal cavity (removing part of the sphenoid bone) and then we pass through the sphenoidal sinus
58
Q

The inferior hypophyseal artery supplies which lobe of the pituitary gland?

A

The posterior lobe

59
Q

The superior hypophyseal artery supplies which part of the pituitary gland?

A
  • Loop upwards then proceed downwards to the anterior pituitary

1) The infundibulum

2) The anterior pituitary (by forming a capillary network that passes down from the sinusoid into the anterior lobe of the pituitary gland (forming the hypophyseal portal system)

Y2S1 ANATOMY (15 decks)

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