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Histology > Lecture 38 > Flashcards

Lecture 38 Flashcards

1
Q

Pituitary gland in brain location

A

Hypothalamus connected to pituitary gland via infundibulum aka pituitary stalk

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2
Q

Embryo has 2 tubes

A

Neural tube forms majority of nervous system. Gut tube forms majority of digestive system

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3
Q

Pituitary gland - development

A

4th week of development: ep cells lining roof of mouth proliferate and migrate to form loop structure. At the same time, floor of
diencephalon bulges

Floor of diencephalon continues to
proliferate. Roof of mouth makes complete loop, and space within it is Rathke’s pouch.

Soon, the roof of mouth ep cells will separate and migrate with the floor of diencephalon.

Overall: roof of mouth becomes anterior lobe (pars distalis) and pars tuberalis, and maybe pars intermedia; floor of diencephalon becomes posterior lobe (pars nervose)

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4
Q

Pituitary gland structure

A

2 lobes: pars distalis (anterior lobe) and pars nervosa (posterior lobe)

Pars intermedia is part of pars distalis and are ep cells that align next to pars nervosa

Pars tuberalis is part of pars distalis, and is wrapped around infundibulum and part of the pars nervosa.

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5
Q

Pituitary-hypothalamus communication

A

Infundibulum connects hypothalamus to pituitary. Median eminence extends into pars nervosa, and this extension point is called infundibular process. Infundibulum = median eminence + infundibular process

Paraventricular and supraoptic make hormones and direct release into pars nervosa.

Hypothalamus-hypophysiotropic nucleus influences pars distalis. HHN does not make hormones. Pars distalis makes hormones. HHN sends signals and releases substances that influence the pars distalis. HHN axons terminate in the median eminence. They cannot have direct pathway with pars distalis bc pars distalis was embryologically derived from ep cells lining roof of mouth, unlike with pars nervosa.

Pars nervosa = posterior lobe = neurohypophysis

Pars distalis = anterior lobe = adenohypophysis

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6
Q

Blood supply in hypothalamus to pars nervosa

A

Pars nervosa receive blood directly from inferior hypophysial artery, which forms a capillary plexus in the pars nervosa. When PVN and SN produce hormones and give to pars nervosa, it is released into this
capillary plexus, which allows the hormones to travel through vascular system.

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7
Q

Blood supply in hypothalamus to pars distalis

A

Pars distalis receives blood indirectly via superior hypophysial artery, which forms a capillary plexus in the median eminence. This capillary plexus makes a secondary capillary plexus in the pars distalis. Bc there are 2 plexuses that communicate with each other, this is a hypothalamo-hypophysial portal system, which takes what is released in median eminence and transports it into secondary capillary plexus in the pars distalis

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8
Q

Overall hypothalamus to pars nervosa

A

its hormones are made by PVN and SN, which travel along axons into pars nervosa, released directly into capillary plexus. Their
hormones (oxytocin, antidiuretic hormone) travel in bloodstream to target tissues

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9
Q

Overall hypothalamus to pars distalis

A

HHN releases activating or inhibiting substances into primary capillary plexus in the median eminence. The substances
travel through HHPS into secondary capillary plexus of pars distalis. These substances activate or inhibit 2 cell types in pars distalis: basophils and acidophils. These cells make hormones (ACTH, FSH LH, TSH, GH, prolactin), which are released into vascular system, acting on target organs

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10
Q

H and E: pituitary gland

A

Pars distalis is dark, pars nervosa is light

Pars intermedia has colloid-filled follicles called remnants of Rathke’s pouch

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11
Q

H and E: Pars Distalis

A

Chromophils: acidophil attract acidophilic dye, basophil attracted to basophilic dyes + stipple appearance. They are strongly
attracted to dye bc these cells make hormones and package the hormones into secretory vesicles

Chromophobes are lighter, bc these cells do not produce hormones. These cells already secreted hormones or did not produce hormones in the first place.

Fenestrated capillaries here too bc hormones are released here to travel to vascular system

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12
Q

Types of acidophils and their hormones

A
  1. Somatotrophs make growth hormone
  2. Mammotrophs make prolactin
    - acts on mammary glands
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13
Q

Types of basophils and their hormones

A
  1. Gonadotrophs make LH and FSH
    - act on male and female reproductive system
  2. Thyrotrophs make TSH
    - acts on thyroid gland
  3. Corticotrophs make ACTH
    - acts on adrenal cortex
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14
Q

Gonadotrophs

A

A basophil. Makes LH and FSH.

FSH

  • controls menstrual cycle and stimulate growth of eggs in follicular cells in ovaries
  • stimulates and maintains spermatogenesis in Sertoli cells

LH

  • stimulates leydig cells to produce androgenic hormones (i.e. testosterone)
  • aids in egg maturation in ovary and provides hormonal trigger for ovulation to occur

Pathway stimulated by gonadotrophin releasing hormone, GnRH

Pathway inhibited by inhibin hormone, released by follicular and Sertoli cells

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15
Q

Thyrotrophs

A

Basophil.

TSH

  • goes to thyroid gland
  • Stimulates the production of T3 (triiodothyronine) and T4 (thyroxine)
  • Essential to maintain metabolic rates, heart and digestive functions, and much more
  • pathway stimulated by Thyrotrophin releasing hormone (TRH)
  • pathway inhibited by T3
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16
Q

Corticotrophs

A

Basophil

ACTH
- goes to adrenal cortex
- Stimulates the adrenal gland to produce:
• Aldosterone (mineralocorticoid)
• Cortisol (glucocorticoid)
• Androgenic steroids

  • pathway stimulated by corticotropic releasing hormone (CRH)
  • pathway inhibited by cortisol
17
Q

Somatotrophs

A

Acidophil

GH
- Stimulates hepatocytes to produce
insulin-like growth factor (IGF-1)
- IGF-1 stimulates chondrocytes located
in the epiphyseal plates of long bones
- Increases fat breakdown and protein
synthesis

  • pathway stimulated by growth hormone releasing hormone
  • pathway inhibited by somatostatin peptide
18
Q

Mammotrophs

A

Acidophil

Prolactin
- Promotes the growth and development
of mammary glands within breast tissue
- Stimulates the mammary glands to produce milk

  • pathway stimulated by prolactin releasing factor (PRF) and thyrotropin releasing factor (TRF)
  • pathway inhibited by dopamine
19
Q

Tract that PVN and SN hormones travel on

A

PVN and SN neurons have axons called hypothalamo-neurohypophysial tract that go directly to pars nervosa. The hormones made by the nuclei travel along the tract and
release directly into pars nervosa

20
Q

H and E: pars nervosa

A

Herring body is identifying feature

Filled with neuropil

Has capillaries

Pituicytes are a glial-cell type. It is a type of astrocyte, so it is a supporting cell

21
Q

Herring body

A

In pars nervosa

This is a feature that contains secretory vesicles. Stipple appearance in H and E.

PVN and SN send hormones along tract, and if you take cross section through the pituitary gland, it makes cross section through axons,
causing herring bodies. Herring bodies are axonal swellings located along the axons and contain the hormones that were made by the nuclei that get packaged to secretory vesicles.

22
Q

Hormones released in Pars nervosa

A

PVN releases ADH

Supraoptic nucleus releases oxytocin

PVN and SN can produce either of the 2 listed hormones, but they have their hormone preference

23
Q

ADH in pars nervosa

A

Increases blood pressure by causing moderate vasoconstriction of blood vessels
- ADH acts on tunica media of blood vessels to cause moderate vasoconstriction, increasing BP

Increases the water permeability of collecting ducts thereby allowing for more water reabsorption and thus reduced urine output
- acts on collecting ducts in the kidneys. ADH acts on aquaporin channels located on walls of collecting ducts, opening these channels to allow more water absorption, causing less urine output

24
Q

Oxytocin in pars nervosa

A

Induces the contraction of myometrium during childbirth

Acts on the myoepithelial cells of mammary glands causing milk to enter the lactiferous ducts from where it can be excreted

25
Q

Summary

A

Histology (25 decks)

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