Endocrine System π Flashcards
Components of the Endocrine System:
- 4 Major Endocrine Organs
- 4 Endocrine components w/in solid organs
- 2 Diffuse neuroendocrine system (DNES)
Major Endocrine Organs:
Pituitary, Pineal, Adrenal, Thyroid - Gland
Endocrine components w/in solid organs:
Pancreas, Testis, Ovary, Kidneys
Diffuse neuroendocrine system:
Most of the time scattered in GIT, Respiratory tract
Pituitary gland
- Other name
- Housed where?
- Parts
- Hypophysis cerebrii
- Housed in sella turcica
- Adenohypophysis (anterior part) and Neurohypophysis (posterior part)
What is the master endocrine gland?
Pituitary gland
Embryology of the Pituitary gland
- Originates from which structure/s?
- How is it formed?
- Partly from the developing brain (neural ectoderm) and partly from the developing oral cavity (oral ectoderm)
- 3rd week of development:
Neurohypophyseal bud grows caudally from the diencephalon but it is still connected through the future infundibulum -> becomes the posterior pituitary
An outpocketing grows cranially from the roof of the pharynx and eventually becomes the anterior pituitary
Late 2nd month of development:
The hypophyseal pouch would detach from the roof of the pharynx and merge with the neurohypophyseal bud.
Fetal period:
During this period, the anterior and posterior parts of the pituitary would complete their development.
Determine the divisions of the Pituitary Gland
- Typically glandular
- Resemble CNS tissue
- Dark-staining
- Pale staining
- Adenohypophysis/Anterior lobe
- Neurohypophysis/Posterior lobe
- Adenohypophysis
- Neurohypophysis
Pars distalis
- Relative size and location
- Group of cells
- Largest and most anterior
- Chromophils - secretory cells of the anterior pituitary with hormones stored in the cytoplasmic granules; further classified into acidophils and basophils
Acidophils:
>Somatotophs (constitute half the cells in PD)
>Lactotrophs: PRL
Basophils:
>Corticotrophs: synthesize POMC which forms ACTH and LPH upon cleavage
>Gonadotrophs: FSH & LH
>Thyrotrophs: leas abundant
Chromophobes:
- few to no secretory granules
- have pale nuclei and cytoplasm
- SMALLER than chromophils
- represent a heterogeneous grp including SCs, undx progenitor cells
Funnel-shaped region hugging around the infundibulum of the neurohypophysis. What cells does this area contain?
Pars tuberalis
>Contain mostly gonadotrophs
Thin zone of basophilic cells between pars distalis and pars nervosa. Cells?
Pars intermedia
>Often invaded by basophils and chromophobes
>Usually contain small, colloid-filled cysts of various sized derived from the lumen of the embryonic hypophyseal pouch
Neurohypophysis (Posterior Pituitary)
- Composition
- Unique char in relation to hormones
- Consists mainly of unmyelinated axons of large secretory neurons with cell bodies in the supraoptic and paraventricular nuclei of the HP
- DOES NOT contain the cells that synthesize the two hormones it stores (ADH and OT)
Pars Nervosa
- Location
- Function
- Translocation of hormones down the hypothalamic-hypophyseal tract utilizes this protein
- Neurohypophysis (Posterior pituitary)
- Storage site of OT and ADH
- Neurophysin
Infundibular stalk
- Location
- Function
- Neurohypophysis
2. Bridges the hypothalamic and hypophyseal regions in the median eminence
Identify the type of cell in the posterior pituitary.
- Highly branched glial cells that resemble astrocytes (helper cells) because it comes from diencephalon
- Most abundant cell type in posterior pituitary
- Axonal dilatations where hormones accumulate
- Pituicytes
- Pituicytes
- Neurosecretory bodies (Herring Bodies)
Hormones of the posterior pituitary gland? Synthesized where? Function?
- ADH/Arginine Vasopressin
- synthesized in the supraoptic nucleus
- increases water permeability of renal collecting ducts - Oxytocin
- synthesized in the PVN
- stimulates contraction of the mammary gland myoepithelial cells and uterine smooth muscle
Hypothalamic-Hypophyseal Tract System
- Pathway
- ADH and OT undergo what transport and accumulate where temporarily before release and uptake by what?
- What enables distribution of the hormones throughout the body? Be specific.
- SON + PVN -> infundibulum -> Pars Nervosa of Neurohypophysis
- ADH and OT undergo axonal transport and accumulate temporarily in the axons of the hypothalamic-hypophyseal tract before release and uptake by capillaries
- Inferior hypophyseal artery
Hypothalamic-Hypophyseal Portal System 1. Carries neuropeptides from where to where? 2. Blood supply? 3. Venous drainage? 4. Superior Hypophyseal Arteries >Supplies what? >Divides into what as it passes down the infundibulum. Branches? 5. Inferior Hypophyseal Arteries >Supplies what? >Arises as a single branch from?
- From the median eminence to the adenohypophysis to simulate or inhibit hormone release by endocrine cells
- Internal Carotid A.
- Hypophyseal V.
- Superior Hypophyseal Arteries
>Supplies the median eminence and infundibular stalk
>Divides into anterior and posterior branches as it passes down the infundibulum
>Branches:
A. artery of trabecula - goes down to supply pars distalis
B. Primary plexus of fenestrated capillaries which rejoin to form venules that branch again as larger secondary capillary plexus in your adenohypophysis - Inferior Hypophyseal Arteries
>Supplies neurohypophysis
>From ICA