Pineal, Hypothalamus, and Pituitary Glands Flashcards Preview

Histology > Pineal, Hypothalamus, and Pituitary Glands > Flashcards

Flashcards in Pineal, Hypothalamus, and Pituitary Glands Deck (23):
1

Pineal Gland Location and structure

- adjacent to the third ventricle ( right at the back of the third ventricle)
- encapsulated by CT (trabeculae) creating lobules

- Contains pinealocytes
- Glial cells (phagocytic)

Corpora arenacea (brain sand)
- accumulation of material that cant be secreted

2

Functions of Pineal

- Controls the sleep awake cycle
- secretes serotonin and melatonin
- During the day time, serotonin levels peak
- As we approach night, serotonin is converted to melatonin by HIOM
- At night, we have peak melatonin levels

3

Innervation of Pineal

- Direct autonomic sympathetic input from superior cervical ganglion promotes melatonin synthesis

- Visual input from retina through suprachiasmatic nucleus (hypothalamus) inhibits melatonin synthesis during the day

4

Pinealocytes

- main cell types producing serotonin and melatonin

- secretes product into fenestrated capillaries in the pineal so that it can be carried elsewhere through the body to carry out its function

5

Hypothalamus

- Immediately above the pituitary
- adjacent to the 3rd ventricle

- Contain Nuclei (clusters of cells with similar function)
- mainly cell bodies of neurons

- Anterior hypothalamus - regulates parasympathetic autonomic NS
- Posterior Hypothalamus - regulates sympathetic autonomic NS

6

Ventromedial Nuclei

- Project to the median eminence of the pituitary
- Median eminence is infundibular region of the stem region of pituitary that has a prominent vascular bed (fenestrated capillaries)

- capillaries are called primary capillary plexus
- hormones pass into the capillaries and down into the pars distalis of pituitary

7

Supraoptic Nuclei

- synthesizes vasopressin/ADH
- Hormone goes to kidney and promotes fluid uptake

- Axons project through the stalk and stem and into the pars nervosa in the pituitary
- Synthesizes hormone in hypothalamus and releases them in the pituitary

- Hormones are stored in the herring bodies which can be released at a later time

8

Paraventricular Nuclei

- Synthesizes oxytocin
- regulates birth and nurture of infant

- Project axons through the stalk and stem and into the pars nervosa in the pituitary

- Hormones are stored in herring bodies which can be released at a later time
- herring bodies are terminal vesicles

9

Hypothalamo-Hypophyseal Portal System

- Fenestrated capillaries of median eminence originate from superior hypophyseal artery

- Inferior hypophyseal artery branches and supplies vasculature for pars nervosa

10

Hypothalamic Releasing Hormones

- GRH
- PRH
- TRH
- GnRH
- CRH
- MRF (melanocyte stimulating hormone releasing factor)

11

Neurohypophysis

- Neuronal component of pituitary
- Consists of infundibular stalk which is filled with axonal projections from the hypothalamus
- Pars nervosa - containing the herring's bodies filled with oxytocin and vasopressin

- embryologically arises from neronal tissue growing down from base of the brain

- contains unmyelinated axons

12

Adenohypophysis

- Epithelial component of pituitary
- Pars Distalis - major component
- Pars intermedia - small region between distalis and nervosa
- Pars Tuberalis - sleeve or collar around part of the infundibular stalk

- embryologicaly grows from oral epithelial tissue

13

Pituicytes

- highly branched glial cells
- found throughout the neurohypophysis

14

ADH

- vasopressin
- secrted by cell bodies in the supraoptic nucleus
- promotes water reabsorption in kidney collecting ducts

15

Oxytocin

- secreted by paraventricular nucleus
- Stimulates milk ejection in mammary gland and uterine smooth muscle contractions

16

Neurophysin

- carrier glycoprotein associated with oxytocin and vasopressin

17

Pars Distalis

- 3/4 of pituitary gland

- controlled by releasing/inhibiting hormones released at median eminence
- drained down to the highly fenestrated capillaries in the pars distalis

- Contains Chromophobes and Chromophils

18

Chromophobes

- lack granules
- either follicular (support) or undifferentiated cels
- stain poorly

19

Chromophils

- Secretory cells
- Stain well

Acidophils
- stain yellow/orange
- simple proteins
Basophils
- stain purple/blue
- glycoproteins

20

Acidophils

- secrete Mammotrophs (Prolactin)
- secrete somatotrophs (GH)

21

Basophils

Secrete:
- Thyroid stimulating hormone
- Gonadotrophs (FSH and LH)
- Corticotrophs (ACTH, B-lipotropin, B-endorphin, MSH)

- Corticotrophs are secreted as one big product (pro-opio-melano-cortin) that is chopped up to have different functions

22

Pars Tuberalis

- Forms a partial collar around infundibular stalk
- histologically stains as basophils
- Secretes mostly gonadotrophins (LH and FSH)

- contains primary capillary plexus

23

Pars Intermedia

- Right between nervosa and distalis
- most of the hormone secreted here is malanoctye stimulating hormone (MSH)
- melanotrophs