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Endocrine System > Anatomy and Histology of the Pituitary Gland > Flashcards

Anatomy and Histology of the Pituitary Gland Flashcards

1
Q

What is the pituitary gland?

A

It is an oval structure located beneath the hypothalamus of the brain & attached to it by a stalk

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2
Q

What is the stalk that connects the pituitary gland to the hypothalamus?

A

Infundibulum

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3
Q

What is the master endocrine gland?

A

The pituitary gland influences the activity of other endocrine gland

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4
Q

What is the location of the pituitary gland?

A

In the sella turcica of the sphenoid bone

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5
Q

What are the relations to the sella turcica?

A

Superior: The diaphragm sellae (a dural fold) covers the sella turcica and separates it from the optic chiasm, which is just above.
Inferior: The sphenoidal sinus lies below the sella turcica.
Lateral: The cavernous sinuses, which contain critical structures like the internal carotid artery and cranial nerves III, IV, V1, V2, and VI.
Posterior: The dorsum sellae separates the sella turcica from the brainstem.

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6
Q

What is the Tuberculum sellae? Function?

A

Anterior elevation forming the front boundary of the sella turcica
–> Serves as a landmark separating the sella turcica from the sphenoidal sinus below.

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7
Q

What is the hypophyseal fossa? Function?

A

The central depression that houses the pituitary gland (hypophysis).
–> It is a crucial structure for hormonal control of multiple body functions.

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8
Q

What is the dorsum sellae? Function?

A

The posterior bony boundary of the sella turcica.
–> Protects the pituitary gland posteriorly and supports the tentorium cerebelli.

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9
Q

What are the clinoid processes?

A

Anterior clinoid processes: Projections from the sphenoid bone that serve as attachment points for the tentorium cerebelli.

Posterior clinoid processes: Located on the dorsum sellae, these help anchor the tentorium cerebelli and contribute to the stability of the brainstem and cerebellum.

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10
Q

What are the divisions of the hypophysis?

A

Anatomical and physiological parts

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11
Q

What is the anterior lobe of the hypophysis?

A

Adenohypophysis, 75% of gland weight

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12
Q

What is the adenohypophysis mainly?

A

Glandular tisse

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13
Q

What is the posterior lobe of the hypophysis?

A

Neurohypophysis contains axon terminals for neurons in the hypothalamus

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14
Q

What are the different parts of the hypophysis?

A
  1. Ectodermal outgrowth (Rathke’s much) in the roof of the primordial mouth (stomodeum)
  2. Ectodermal down growth in the floor of the hypothalamus (neurohypophyseal bud)
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15
Q

What are the three components of the adenohypophysis?

A
  1. Pars distalis
  2. Pars tuberalis
  3. Pars intermedia
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16
Q

What are the two parts of the neurohypophysis?

A
  1. Pars nervosa
  2. Infudibulum
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17
Q

What are the components of the infundibulum of the neurohypophysis?

A

Stem and median eminence

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18
Q

Which part of the neurohypophysis (infidibulum) is conjucted to the hypothalamus?

A

Median eminence

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19
Q

What is the embryonic structure of the thalamus and the hypothalamus?

A

Diencephalon

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20
Q

What is the pars tuberalis?

A

Surrounds the stalk of pituitary gland

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21
Q

What is the pars intermedia?

A

Posterior wall to the Rathke’s pouch, close to nervosa

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22
Q

What are the relations of hypophysis? (anteriorly)

A
  1. Sphenoid air sinus
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23
Q

What is the clinical significance of the sphenoid air sinus?

A

Access to the pituitary gland, surgical resection

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24
Q

What is the sphenoid air sinus? What is its importance?

A

One large cavity: anterior and posterior

Important: 1. Lightens the skull weight
2. Responds to sound

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25
Q

What are the relations of the hypophysis (posteriorly)? (3)

A
  1. Dorsum sellae
  2. Basillary artery
  3. Pons
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26
Q

What is the dorsum sellae?

A

A bone

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27
Q

Where is the basilar artery?

A

Behind the dorsum emerges from 2 vertebral arteries

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28
Q

What are the pons?

A

Part of the brain stem

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29
Q

What are the relations of the hypophysis (superiorly)?

A
  1. Sellar diaphragm
  2. Optic chasma
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30
Q

What is the sellar diaphragm?

A

It separates the dorsum sellae, pentrates the infundibulum

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31
Q

Where is the pituitary gland cut?

A

At the sellar diaphragm

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32
Q

Where is the optic chiasma?

A

Crosses above the pituitary gland, bitemporal

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33
Q

What are the relations of the hypophysis inferiorly?

A
  1. Sphenoid sinus
  2. Body of sphenoid
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34
Q

What are the relations of the hypophysis laterally?

A

Cavernous sinus

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35
Q

What does the cavernous sinus contain?

A
  1. Part of the internal carotid artery
  2. The 6th cranial nerve
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36
Q

What makes up the wall of the cavernous sinus?

A
  1. 3rd cranial nerve (occulomotor)
  2. 2 divisions of VI (ophthalmic and maxillary)
  3. 4th cranial nerve (Trochlear)
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37
Q

What is the vascalture to the pituitary gland like?

A

Highly vasculature –> Hypophyseal portal system

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38
Q

What happens in the hypophyseal portal system?

A

Blood flows from one capillary network to a 2nd capillary network via a portal vein before returning to the heart

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39
Q

What are the components of the hypophyseal portal system?

A

1st blood capillary –> in the median eminence
2nd blood capillary –> in the anterior pituitary

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40
Q

Where is the 1st blood capillary of the hypophyseal portal system found?

A

Between the hypothalamus and infundibulum

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41
Q

What joins the blood capillaries of the hypophyseal portal system?

A

The veins join together from the portal vein –>, making a plexus in the anterior pituitary gland

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42
Q

Where is the 1st capillary plexus located?

A

At the junction of the hypothalamus and infundibulum

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43
Q

Where is the 2nd capillary plexus located?

A

In the anterior pituitary

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44
Q

What are examples of the vasculature to the anterior pituitary gland?

A

Superior hypophyseal artery
1st capillary plexus
Hypophyseal portal veins
2nd capillary plexus
Anterior hypophyseal veins

45
Q

What is the vasculature to the posterior pituitray?

A

Inferior hypophyseal artery
Capillary plexus
Posterior hypophyseal veins

46
Q

In the neurohypophysis what does the capillary plexus store?

A

Stores the hormones in the nerve bundles/ending

47
Q

The inferior hypophyseal artery is a branch of?

A

Internal carotid artery

48
Q

What does the superior hypophyseal artery supply?

A

Pars tuberalis
Infudibulum

49
Q

What does the inferior hypophyseal artery supply?

A

Pars distalis
Pars intermedia
Pars nervosa

50
Q

What is the hypothalamus?

A

Connection between the nervous and endocrine systems

51
Q

what is the site of action of the hypothalamus?

A

The pituitary gland and neural pathways exist between them

52
Q

Which structures control all the hormones produced by the pituitary gland?

A

Hypothalamus

53
Q

What are the main releasing and inhibitory factors of the hypothalamus? (6)

A
  1. TRH
  2. CRH
  3. SRH
  4. GnRH
  5. PRH
  6. Prolactin inhibitory factor –> inhibits prolactin secretion
54
Q

What are the basophilic hormones from the pituitary gland?

A
  1. ACTH
  2. TSH
  3. FSH
  4. LH
55
Q

WHat are the acidophilic hormones of the pituitary gland?

A

Prolactin
Growth Hormone

56
Q

What are the hormones released from the posterior pituitary gland?

A

ADH
Oxytocin

57
Q

What are the targets of ACTH?

A

ADrenal cortex

58
Q

What are the targets of TSH?

A

Thyroid

59
Q

What are the targets of FSH?

A

Ovaries & Testis

60
Q

What are the targets of LH?

A

Testis and Ovaries

61
Q

What is the target of Prolactin?

A

Mammary gland –> milk sceretion

62
Q

What are the targets of growth hormone?

A

Adipose tissue
Muscle
Bone

63
Q

What are the targets of Oxytocin?

A

Uterus –> contraction
Mammery gland –> myoepithelial contraction

64
Q

What are the targets of ADH?

A

Kidney –> water absorption

65
Q

What are the main components of the pars distalis?

A

The cords of epithelial cells interspersed with capillaries

66
Q

What is the function of the few fibroblasts present in the pars distills?

A

Produce reticular fibers that support the cord of the hormone-secreting cells

67
Q

What % of the mass of the hypophysis does pars distalis account for?

A

75%

68
Q

Where are the hormones produced by the pars distalis stored?

A

Stored as secretory granules, once stimulated by releasing hormones –> they can be released

69
Q

Why is pars distalis not seen in thyroid?

A

Because hormones are synthesised extracellularly

70
Q

What are the cells that are recognizable under the common stains in the pars distalis?

A
  1. Chromophobes –> hate colour
  2. Chromophils –> love colour
  3. Acidophils –> secrete somatotrophs, mammotrophs
  4. Basophils –> gonadotrophs, corticotrophs, thyrotrops
71
Q

WHat are examples of somatotrophs?

A

GH

72
Q

What are examples of mammotrophs?

A

Prolactin

73
Q

WHat are examples of gonadotrophs?

A

FSH & LH

74
Q

What are examples of corticotrophs?

A

ACTH

75
Q

What are the acidophilic cells of the pituitary land?

A
  1. Somatotrophs
  2. Mammotrophs
76
Q

What are the examples of basaphilic cells?

A
  1. Corticotrophs
  2. Thyrotrophs
  3. Gonadotrophs
77
Q

Which is the only cell type which secretes more thanne hormone?

A

Gonadotrophs

78
Q

What are somatotrophs?

A

They are cytoplasmic secretory granules, and they have euchromatic nuclei, occur in clumps and clusters

79
Q

What do somatotrophs secrete?

A

Secrete somatotropin (GH)

80
Q

What % of pars distalis is somatotophs?

A

50%

81
Q

What are eurochrmoatic nuclei?

A

They are active nuclei that keep on synthesizing GH without stopping

82
Q

What % of pars distalis is mammotrophs?

A

20%

83
Q

What are mammotrophs?

A

They resemble somatotrophs
Occur singly

84
Q

During lactation, what are the changes caused due to an increase in organelle size and number?

A
  1. Release prolactin
  2. Promotes mammary gland development
  3. Promotes lactation after birth
85
Q

What are the different examples of basophilic cells?

A

Corticotrophs
Thyrotrophs
Gonadotrophs

86
Q

What are Corticocotrophs?

A

15 to 20% of basophilic cells
Scattered round to ovoid cells
Eccentric nucleus
Few organelles

87
Q

What do corticotrophs secrete?

A

ACTH

88
Q

What are thyrotrophs?

A

5% of the population of basophilic cells
Small secretory granules

89
Q

What do thyrotrophs secrete?

A

TSH

90
Q

What are gonadotrophs?

A

5 to 10% of basophilic cells
Round cells
Secretory granules which vary in diameter

91
Q

What do gonadotrophs secrete?

A

FSH and LH

92
Q

What are chromophobes?

A

Heterogeneous population of cells

93
Q

What kinds of cells make of the chromophobe cell population?

A
  1. Nonspecific stem cells
  2. Undifferentiated progenitor cells
  3. Degranulated chromophils
94
Q

What is the pars intermedia?

A

Thin zone between pars distalis and pars nervosa

95
Q

Where does pars intermedia develop from?

A

From the dorsal wall of Rathke’s pouch

96
Q

What is the pars intermedia made of?

A

Many cuboidal cell lines, colloid-containing cysts

97
Q

What invades the pars intermedia?

A

Cords of basophils along the network of capillaries invade the area

98
Q

During fetal life, what do the basophils that invade the pars intermedia secrete?

A

MSH –> melanocyte stimulating hormone

99
Q

What is the physiological significance of pars intermedia?

A

SIgnificance is still uncelar

100
Q

What is the pars tubralis?

A

Funnel-shaped, which surrounds the infundibulum

101
Q

What is the pars tuberalis made of?

A

Basophilic and gonadotrophic cells

102
Q

What does the pars tuberalis secrete?

A

LH & FSH

103
Q

WHat is the neurohypophysis made of?

A

Infundibulum
Pars nervosa

104
Q

What are the secretory neurons of the neurhypophysis?

A

Supraoptic neuron –> ADH
Paraventricular neuron –> Oxytocin

105
Q

What are the features of neurhypophysis?

A
  1. No secretory cells (no cells with granules)
  2. Pituicytes
  3. Unmyelinated axons
  4. Axon terminal swellings –> Herring bodies
106
Q

What are pituicytes?

A

Special glial cells whose function is to support or regulate the function of the surrounding cells

107
Q

What are axon terminal swellings?

A

Parts where ASH or ACTH is stored

108
Q

What are Herring bodies?

A

Large bodies, neuronal bodies

109
Q
A

Endocrine System (25 decks)

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