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

Anatomy and Histology of the Pituitary Gland Flashcards

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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
What are the relations of the hypophysis (posteriorly)? (3)
1. Dorsum sellae 2. Basillary artery 3. Pons
26
What is the dorsum sellae?
A bone
27
Where is the basilar artery?
Behind the dorsum emerges from 2 vertebral arteries
28
What are the pons?
Part of the brain stem
29
What are the relations of the hypophysis (superiorly)?
1. Sellar diaphragm 2. Optic chasma
30
What is the sellar diaphragm?
It separates the dorsum sellae, pentrates the infundibulum
31
Where is the pituitary gland cut?
At the sellar diaphragm
32
Where is the optic chiasma?
Crosses above the pituitary gland, bitemporal
33
What are the relations of the hypophysis inferiorly?
1. Sphenoid sinus 2. Body of sphenoid
34
What are the relations of the hypophysis laterally?
Cavernous sinus
35
What does the cavernous sinus contain?
1. Part of the internal carotid artery 2. The 6th cranial nerve
36
What makes up the wall of the cavernous sinus?
1. 3rd cranial nerve (occulomotor) 2. 2 divisions of VI (ophthalmic and maxillary) 3. 4th cranial nerve (Trochlear)
37
What is the vascalture to the pituitary gland like?
Highly vasculature --> Hypophyseal portal system
38
What happens in the hypophyseal portal system?
Blood flows from one capillary network to a 2nd capillary network via a portal vein before returning to the heart
39
What are the components of the hypophyseal portal system?
1st blood capillary --> in the median eminence 2nd blood capillary --> in the anterior pituitary
40
Where is the 1st blood capillary of the hypophyseal portal system found?
Between the hypothalamus and infundibulum
41
What joins the blood capillaries of the hypophyseal portal system?
The veins join together from the portal vein -->, making a plexus in the anterior pituitary gland
42
Where is the 1st capillary plexus located?
At the junction of the hypothalamus and infundibulum
43
Where is the 2nd capillary plexus located?
In the anterior pituitary
44
What are examples of the vasculature to the anterior pituitary gland?
Superior hypophyseal artery 1st capillary plexus Hypophyseal portal veins 2nd capillary plexus Anterior hypophyseal veins
45
What is the vasculature to the posterior pituitray?
Inferior hypophyseal artery Capillary plexus Posterior hypophyseal veins
46
In the neurohypophysis what does the capillary plexus store?
Stores the hormones in the nerve bundles/ending
47
The inferior hypophyseal artery is a branch of?
Internal carotid artery
48
What does the superior hypophyseal artery supply?
Pars tuberalis Infudibulum
49
What does the inferior hypophyseal artery supply?
Pars distalis Pars intermedia Pars nervosa
50
What is the hypothalamus?
Connection between the nervous and endocrine systems
51
what is the site of action of the hypothalamus?
The pituitary gland and neural pathways exist between them
52
Which structures control all the hormones produced by the pituitary gland?
Hypothalamus
53
What are the main releasing and inhibitory factors of the hypothalamus? (6)
1. TRH 2. CRH 3. SRH 4. GnRH 5. PRH 6. Prolactin inhibitory factor --> inhibits prolactin secretion
54
What are the basophilic hormones from the pituitary gland?
1. ACTH 2. TSH 3. FSH 4. LH
55
WHat are the acidophilic hormones of the pituitary gland?
Prolactin Growth Hormone
56
What are the hormones released from the posterior pituitary gland?
ADH Oxytocin
57
What are the targets of ACTH?
ADrenal cortex
58
What are the targets of TSH?
Thyroid
59
What are the targets of FSH?
Ovaries & Testis
60
What are the targets of LH?
Testis and Ovaries
61
What is the target of Prolactin?
Mammary gland --> milk sceretion
62
What are the targets of growth hormone?
Adipose tissue Muscle Bone
63
What are the targets of Oxytocin?
Uterus --> contraction Mammery gland --> myoepithelial contraction
64
What are the targets of ADH?
Kidney --> water absorption
65
What are the main components of the pars distalis?
The cords of epithelial cells interspersed with capillaries
66
What is the function of the few fibroblasts present in the pars distills?
Produce reticular fibers that support the cord of the hormone-secreting cells
67
What % of the mass of the hypophysis does pars distalis account for?
75%
68
Where are the hormones produced by the pars distalis stored?
Stored as secretory granules, once stimulated by releasing hormones --> they can be released
69
Why is pars distalis not seen in thyroid?
Because hormones are synthesised extracellularly
70
What are the cells that are recognizable under the common stains in the pars distalis?
1. Chromophobes --> hate colour 2. Chromophils --> love colour 3. Acidophils --> secrete somatotrophs, mammotrophs 4. Basophils --> gonadotrophs, corticotrophs, thyrotrops
71
WHat are examples of somatotrophs?
GH
72
What are examples of mammotrophs?
Prolactin
73
WHat are examples of gonadotrophs?
FSH & LH
74
What are examples of corticotrophs?
ACTH
75
What are the acidophilic cells of the pituitary land?
1. Somatotrophs 2. Mammotrophs
76
What are the examples of basaphilic cells?
1. Corticotrophs 2. Thyrotrophs 3. Gonadotrophs
77
Which is the only cell type which secretes more thanne hormone?
Gonadotrophs
78
What are somatotrophs?
They are cytoplasmic secretory granules, and they have euchromatic nuclei, occur in clumps and clusters
79
What do somatotrophs secrete?
Secrete somatotropin (GH)
80
What % of pars distalis is somatotophs?
50%
81
What are eurochrmoatic nuclei?
They are active nuclei that keep on synthesizing GH without stopping
82
What % of pars distalis is mammotrophs?
20%
83
What are mammotrophs?
They resemble somatotrophs Occur singly
84
During lactation, what are the changes caused due to an increase in organelle size and number?
1. Release prolactin 2. Promotes mammary gland development 3. Promotes lactation after birth
85
What are the different examples of basophilic cells?
Corticotrophs Thyrotrophs Gonadotrophs
86
What are Corticocotrophs?
15 to 20% of basophilic cells Scattered round to ovoid cells Eccentric nucleus Few organelles
87
What do corticotrophs secrete?
ACTH
88
What are thyrotrophs?
5% of the population of basophilic cells Small secretory granules
89
What do thyrotrophs secrete?
TSH
90
What are gonadotrophs?
5 to 10% of basophilic cells Round cells Secretory granules which vary in diameter
91
What do gonadotrophs secrete?
FSH and LH
92
What are chromophobes?
Heterogeneous population of cells
93
What kinds of cells make of the chromophobe cell population?
1. Nonspecific stem cells 2. Undifferentiated progenitor cells 3. Degranulated chromophils
94
What is the pars intermedia?
Thin zone between pars distalis and pars nervosa
95
Where does pars intermedia develop from?
From the dorsal wall of Rathke's pouch
96
What is the pars intermedia made of?
Many cuboidal cell lines, colloid-containing cysts
97
What invades the pars intermedia?
Cords of basophils along the network of capillaries invade the area
98
During fetal life, what do the basophils that invade the pars intermedia secrete?
MSH --> melanocyte stimulating hormone
99
What is the physiological significance of pars intermedia?
SIgnificance is still uncelar
100
What is the pars tubralis?
Funnel-shaped, which surrounds the infundibulum
101
What is the pars tuberalis made of?
Basophilic and gonadotrophic cells
102
What does the pars tuberalis secrete?
LH & FSH
103
WHat is the neurohypophysis made of?
Infundibulum Pars nervosa
104
What are the secretory neurons of the neurhypophysis?
Supraoptic neuron --> ADH Paraventricular neuron --> Oxytocin
105
What are the features of neurhypophysis?
1. No secretory cells (no cells with granules) 2. Pituicytes 3. Unmyelinated axons 4. Axon terminal swellings --> Herring bodies
106
What are pituicytes?
Special glial cells whose function is to support or regulate the function of the surrounding cells
107
What are axon terminal swellings?
Parts where ASH or ACTH is stored
108
What are Herring bodies?
Large bodies, neuronal bodies
109

Endocrine System (25 decks)

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