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Endocrine > Histology of the Pituitary Gland, Hypothalamus, and Pineal Gland > Flashcards

Histology of the Pituitary Gland, Hypothalamus, and Pineal Gland Flashcards

1
Q

what does the endocrine system consist of?

A

i. Glands—pituitary gland
ii. Isolated groups of cells within organs
1. Ie. Islets of Langerhans in pancreas
iii. Individual cells scattered among parenchymal cells
1. Ie. DNEs (diffuse neuroendocrine cells)

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2
Q

how are endocrine cells arranged?

A

a. Endocrine cells are typically arranged as cords/follicles
i. Always very close to fenestrated capiallaries
1. Endocrine cells release their Hs into fenestrated capillariesallows for distribution thruout the body

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3
Q

describe Hs

A

i. chemical substnaces that control and regulate the activity of certain cells/organs
1. Critical for life and every activity of daily living (homeostasis)—digestion, metabolism, growth, development, reproduction, mood
2. Slower onset and longer duration than nervous control
3. 5 major classes

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4
Q

5 major classes of Hs and some examples

A

a. AA derivatives—dopamine, epi
b. Small neuropeptides—GnRH
c. Large proteins—LH, FSH
d. Steroids—cortisol, estrogen
e. Vitamin derivatives—vitamin D

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5
Q

target cells

A

i. cells on which the Hs act
1. Contain surface or cytoplasmic Rs for specific Hs
a. Protein hormonesattach to surface Rsactivate secondary messengers
b. Lipid soluble Hscross cell membranebind to intracellular Rs

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6
Q

location of hypothalamus

A
  1. Floor of the diencephalon

2. Forms part of the wall of the 3rd ventricle

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7
Q

function of the hypothalamus

A

i. master switchboard
1. Connects nervous and endocrine systems
2. Controls the endocrine system by sending messages to the pituitary, which in turn release Hs to stimulate endocrine glands/cells
3. Role in autonomic, endocrine, and limbic systems

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8
Q

how does the hypothalamus regulate?

A
  1. Making releasing Hs or inhibiting Hs that will come down and cause action on the pituitary gland
  2. Hypothalamus also makes some of its own Hs—oxytocin, vasopressin—stores these in posterior pituitary for release
  3. Oversees ANS and helps to stimulate the adrenal medulla via SNS
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9
Q

hypothalamic nuclei and the Hs they secrete

A
  1. Cluster of neuronsmultiple hypothalamic nuclei
  2. Supraoptic and paraventricular nuclei BOTH produce ADH and oxytocin which are stored in the posterior pituitary
    a. Supraoptic nucleus primarily produces ADH
    b. Paraventricular nucleus primarily produces oxytocin
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10
Q

pituitary gland

A

a. Aka hypophysis—“master gland”
b. Suspended by a stalk from the hypothalamus
c. Size of a pea

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11
Q

location of the pituitary gland

A

i. In the sella turcica within the sphenoid bone of the skull
ii. Posterior to the optic chiasm

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12
Q

nonfunctional pituitary adenoma*

A
  1. pituitary tumor >1 cm
    a. Compress optic chiasm—bitemporal hemianopsia—issues with peripheral vision
    b. Compresses pituitary—hypopituitarism
    c. Headache is common
    d. Causes overproduction of a H and loss of peripheral vision
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13
Q

sellar diaphragm

A

i. Dura mater that extends over and covers the pituitary within the sell turcica

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14
Q

embryonic origins of the pituitary gland

A
  1. Oral ectodermbecomes anterior pituitary—adenohypophysis
    a. Gland
    b. Oral ectoderm–>evaginates from roof of mouthforms Rathe’s pouch–>grows cranially–>pinches off at the base of pouch to separate it from the oral cavity
  2. Neuroectoderm–>becomes posterior pituitary—neurohypophysis
    a. Nervous tissue
    b. Neuroectoderm –>evaginates from floor of diencephalon–>grows caudally as a stalk–>never detaches from brain–>remains as infundibular stalk
    ii. These are united anatomically but function differently
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15
Q

craniopharyngioma

A

a. regressing stalk of Rathke’s pouch can leave residual tissue which may become this tumor
i. Benign childhood brain tumor that usually is suprasellar
ii. Similar to pituitary adenomas, can compress optic chiasm and cause bilateral hemianopsia
iii. Derived from remnants of Rathke’s pouch—often contains cystic spaces and calcifications

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16
Q

regions of the adenohypophysis

A
  1. Pars distalis—anterior portion, biggest part
  2. Pars tuberalis—surrounds infundibular stalk
  3. Pars intermedia—division b/w anterior and posterior
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17
Q

regions of the neurohypophysis

A
  1. Pars nervosa

2. Infundibular stalk

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18
Q

pars distalis

A

i. Largest portion of the pituitary gland
ii. Made up of:
1. Glandular epithelial cells arrange in thick cordssecrete the 6 Hs of the anterior pituitary
2. Fenestrated capillaries (sinusoids)part of the secondary plexus
3. Some CT stroma

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19
Q

Hs of the adenohypophysis

A 
FLAT PIG
FSH
LH
ACTH
TSH
prolactin
GH
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20
Q

FSH

A

a. Gonadotrophs (basophils)
b. Stimulated by: GnRH from hypothalamus
c. Inhibited by:
i. Inhibin
ii. Feedback inhibition of estrogen in females
d. Effects:
i. FSH stimulates ovarian follicle maturation and estrogen production in females
ii. Stimulates Sertoli cells to produce sperm in males

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21
Q

LH

A

a. Gonadotrophs (basophils)
b. Stimulated by: GnRH from hypothalamus
c. Inhibited by:
i. Feedback inhibition by estrogen and progesterone in females and testosterone in males
d. Effects:
i. LH triggers ovulation and stimulates ovarian production of estrogen and progesterone in females
ii. Promotes Leydig cell production of testosterone in males

22
Q

Kallman Syndrome*

A

i. Delayed or absent puberty and anosmia (no sense of smell)
ii. Hypogonadotrophic hypogonadism—don’t get enough FSH and LH to go to gonads
iii. Caused by genetic mutation that prevents movement of GnRH into the anterior pituitary
iv. Prevents migration of GnRH neurons to arcuate nucleus and olfactory neurons to olfactory bulb

23
Q

adrenocorticotropic H (ACTH)

A

a. Corticotrophs (basophils)
b. Stimulated by: CRH from hypothalamus
c. Inhibited by: feedback inhibition by glucocorticoids (ie. Cortisol)
d. Effects:
i. Stimulates the adrenal cortex to release glucocorticoids and androgens

24
Q

Thyroid Stimulating H

A

a. Thyrotrophs (basophils)
b. Stimulated by: TRH from hypothalamus
c. Inhibited by: feedback inhibition by thyroid Hs (T3-4)
d. Effect:
i. Stimulates thyroid gland to release T3 & T4control metabolism

25
Q

GH

A

a. Somatotrophs (acidophils)
b. Stimulated by:
i. GHRH (growth H releasing H) from hypothalamus
ii. Hypoglycemia, low levels FA’s, high blood levels of AAs, exercise
c. Inhibited by:
i. Somatostatin
ii. Feedback inhibition by GH and IGF-1
iii. Hyperglycemia, hyperlipidemia, obesity, emotional deprivation
d. Effect:
i. Indirectly stimulates overall growth of bone and soft tissue via production of insulin like growth factor (IGF-1) aka somatomedin

26
Q

acromegaly*

A

i. excessive adult production of GH
ii. growth of face (prognathism), hands, feet—only the things that can continue to grow will
iii. increase in viscera
iv. overproduction of glucose leads to diabetes
v. due to loss of feedback control of GH secretion of GH secreting tumor in pituitary

TX: surgery, radiation, GH receptor antagonist

27
Q

pituitary dwarfism*

A

i. Growth retardation resulting in abnormally short adult stature
ii. Caused by a variety of hereditary and metabolic disorders
iii. Pituitary dwarfism is caused by insufficient GH
iv. Problem can be in hypothalamus or pituitary
v. Non pituitary dwarfism results from inadequate nutrition early in life

28
Q

Hereditary dwarfism including achondroplasia*

A

disorder of GH secretion

with normal trunk size but short limbs and large head

29
Q

hypochondroplasia*

A

disorder of GH secretion

i. similar except for normal head

30
Q

diastrophic dwarfism*

A

disorder of GH secretion

with progressive, crippling skeletal deformities

31
Q

misuse of GH

A

i. Steroids—changes in foot and head size can cause acromegaly

32
Q

chromophils

A

a. Granules in the cells readily take up H&E stain
b. Divided into:
i. Acidophils—acid loving, takes up eosin—pink
1. Cells–>hormone synthesized
a. Mammotrophs–>prolactin
b. Somatotrophs–>GH
ii. Basophils—base loving, takes up hemtoxylin—purple/blue
1. Cells-hormone synthesized
a. Gonadotrophs–>gonadtropins (FSH, LH)
b. Corticotrophs–>adenocorticotropic (ACTH)
c. Thyrotrophs–>thyrotropin (TSH)

33
Q

chromophobes

A

a. No taking up the stain, lacks affinity
b. Stain poorly
c. Only their nuclei are visible
d. Do NOT produce hormones—function unknown
e. Smaller than chromophils

34
Q

pars intermedia

A

i. Between pars distalis and pars nervosa
ii. Function unknown
iii. Frequently has a cleft—remnant of Rathke’s
iv. Consists of small basophils and colloid filled follicles lined by pale cuboidal cells

35
Q

infundibulum

A

i. Suspends pituitary gland from hypothalamus
ii. Composed of 2 parts:
1. Pars tuberalis—surrouds infundibular stalk—part of anterior pituitary
2. Infundibular stalk—neural portion—part of posterior pituitary
a. A thin neural stalk connecting the median eminence of the hypothalamus to the pars nervosa
b. Composed of 2 parts:
i. Median eminence
ii. Infundibular process

36
Q

pars tuberalis

A

i. Forms a sheath surrounding the infundibular/neural stalk—neural portion; part of posterior pituitary
ii. Part of the adenohypophysis
iii. Function unknown

37
Q

ADH

A

a. Primarily produced by supraoptic nucleus in hypothalamus but also produced in the paraventricular nucleus
b. Function
i. Regulates serum osmolarity via V2 receptors in DCT and CD–>causes water retention and concentrates urine
ii. Potent vasoconstrictor at high does—via V1 Rs
c. Release regulated by:
i. Hypothalamic osmoreceptors and baroreceptors

from neurohypophysis

38
Q

oxytocin

A

a. Primarily produced by paraventricular nucleus in hypothalamus but al produced in the supraoptic nucleus
b. Function:
i. Contraction of SM
1. Uterine contractions during labor and after to contract uterus back down to normal size
2. Breast myoepithelial cells facilitate milk ejection
ii. Feel good H

neurohypophysis

39
Q

how does the neurohypohysis release Hs

A
  1. Hypothalamic nuclei produces and secretes the H–>travels down the axons via the infundibular stalk into the pars nervosa–>stored until signaled to be released into blood to take effect
40
Q

pars nervosa

A
  1. Pituicytes
    a. Glial like cells
    b. Appear to support numerous unmyelinated nerve fibers traveling from hypothalamus
  2. Herring bodies
    a. Expanded axon terminals
    b. Filled with the stored neurohypophysis Hs, ADH, and oxytocin
41
Q

pituitary blood supply

A

i. Internal carotid A
1. Superior hypophyseal As–>supply median eminence and infundibulum
2. Inferior hypophyseal As–>supply pars nervosa
ii. No direct blood supply to the anterior pituitary

42
Q

hypothalamohypohyseal portal circulation

A

i. Superior hypophyseal As give rise to the primary capillary plexus in median eminenve
1. Collect hypothalamic releasing and inhibitory Hs
ii. Primary capillary plexus is drained by hypophyseal portal Vs and delivers blood into the secondary capillary plexus in pars distalis
1. Collect anterior pituitary secretions and sends them into circulation via fenestrated capillaries
iii. Inferior hypophyseal As give rise to the third capillary plexus
1. Supplies and collects Hs from posterior pituitary—ADH and oxytocin
2. Sends them into circulation via their own hypophyseal Vs

43
Q

venous drainage of the pituitary

A

i. Anterior pituitary gland secretes Hs–>diffuse into capillaries–>venous sinuses (petrosal and cavernous)
ii. Posterior pituitary gland secretes Hs–>diffuse into capillaries–>hypophyseal Vs–>venous sinuses (petrosal and cavernous)

44
Q

pineal gland general

A

a. Aka epiphysis cerebri
b. Neuroendocrine transducer handling photic information from the retina
c. Develops from a posterior outpocketing of the roof of the diencephalon in midline of the 3rd ventricle
d. Cone shaped, size of pea
e. Roles in growth, development, and regulation of circadian rhythms
f. Main fcn is to manufacture melatonin and serotonin
g. Contains a capsule derived from pia mater

45
Q

pinealocytes

A

i. Pinealocytes
1. Neuron likefuncitonal cells
2. Large pale, irregular nuclei
3. Regulated by beta adrenergic Rs
4. Main fcn is to produce melatonin and serotonin
a. Melatonin—synthesized at night
i. Synthesized from tryptophan
ii. Fcns to maintain circadian rhythmssecreted after exposure to darkness
1. Contributes to drowsiness when lights are turned down
iii. Acts to delay sexual development until puberty by inhibiting GnRH and GH secretion
1. When puberty arrives, melatonin production decreases

46
Q

precocious puberty*

A
  1. Pineal tumors linked to precocious puberty

a. Decreases melatonin–>sexual maturity early

47
Q

jet lag*

A
  • treat with melatonin

1. disrupted circadian rhythm

48
Q

seasonal affective disorder*

A
  • treat with melatonin

- to help regulate emotional responses due to decreased daylight during winter

49
Q

serotonin

A

synthesized during the day

50
Q

neuroglia cells

A

i. Neuroglial cells
1. Interstitial cells
2. Smaller, dense nuclei
3. Support pinealocytes

51
Q

what makes up pineal gland?

A

pinealocytes
neuroglia cells
calcified granular material–brain sand that inc as you age
contains NO neurons

Endocrine (15 decks)

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