L02 - Development, Structure of Pituitary Gland Flashcards
Anatomical position of Pituitary gland?
in sella turcica / hypophysial fossa
(depression of sphenoid bone on floor of anterior cranial cavity)
Anatomically connected to brain but sits outside BBB
Describe the formation of pituitary gland?
- Neural component (neuroectoderm) evaginates from the floor of diencephalon»_space; grows caudally»_space; Posterior pituitary (neurohypophysis)
- Oral component (oropharynx ectoderm) arises as an outpocket from the roof of primitive mouth»_space; migrate superiorly, forms Rathke’s pouch and lose connection with oral cavity»_space; Anterior pituitary (adenohypophysis)
2 lobes fuse to form p. gland
Origin of Pars Intermedia?
dorsal part of the Rathke’s pouch
Origin of pars nervosa?
from neuroectoderm, continuous with posterior lobe of pituitary
Origin of pars distalis?
Anterior side of Rathke’s pouch
Origin of pars tuberalis?
Extension of Rathke’s pouch» surround infundibulum
Define the 3 regions of the anterior pituitary?
separated by indistinct boundaries:
▪ pars distalis = anterior region
▪ pars intermedia = divide 2 lobes
▪ pars tuberalis = wrap around infundibulum
Arterial and venous supply of pituitary gland?
1) L/R superior hypophyseal arteries form 2 plexuses of Hypophyseal Portal System:
i) Primary capillary plexus supply Infundibulum/ neural stalk + Median eminence
ii) Secondary capillary plexus drain Adenohypophysis/ anterior lobe
2) L/R inferior hypophyseal arteries supply Neurohypophysis/ post. lobe + infundibulum
> > efferent hypophyseal veins»_space; cavernous sinus
Which lobe of the pituitary does not have direct arterial supply?
Anterior***
anterior lobe is mainly supplied by the Hypohyseal portal system
List the hypothalamuc nuclei linked to the anterior pituitary?
Ant =
• Dorsal medial, ventral medial and infundibular nuclei
• paraventricular nuclei (PVN) (Parvocellular neurosecretory neurons)
Which region of the anterior pituitary is hormone secreting?
Pars distalis
Describe the ultrastructure of Pars Distalis in ant. pit.?
Hormone-secreting cells in clusters/ cords
surrounded by fibrous tissue, capillaries
Define the 5 secretory cell types in pars distalis and their staining + major secretion.***
Acidophilic:
- Somatotrope = Somatotrophin or GH
- Lactotrope = Prolactin
Basophilic:
- Gonadotrope = FSH, LH
- Thyrotrope = TSH
- Corticotrope = ACTH
Define the 3 cell types in pars distalis by H&E staining.
1) Chromophobes (no staining)
2) Chromophils:
a) Acidophils = red
b) Basophils = violet
Define the colours of the 3 cell types in pars distalis by PAS staining.
1) Chromophobes (no staining)
2) Chromophils:
a) Acidophils = Orange/yellow
b) Basophils = Magenta
RBC, vessels = green
Describe the organization of cells and staining of Pars intermedia?
Cords and follicles, at junction between anterior, posterior lobes, remnant from Rathke’s pouch
weakly basophilic with basophilic granules
Describe the organization of cells of Pars tuberalis?
funnel-shaped region wrapping around infundibulum
Arranged in cords along blood vessels
weak Gonadotrophin-secretion
List all the hormones secreted form the anterior pituitary (9)
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
- Growth hormone (GH) or somatotropin
- Melanocyte-stimulating hormone (MSH)
- Beta-endorphin
- Lipotropin
- Prolactin
List all the hormones secreted from posterior pituitary?
- Antidiuretic hormone (ADH)
* Oxytocin
Which hormones secreted from ant. pituitary are trophic?
- Thyroid-stimulating hormone (TSH)
- Adrenocorticotropic hormone (ACTH)
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
Describe how hypothalamic neurons control the pars distalis in Anterior pituitary? ** think about the portal system**
dorsal medial, ventral medial and infundibular nuclei of hypothalamus»_space; produce neurohormones
> > carried along axon and stored in Median Eminence in infundibulum, rich vascular supply by primary capillary plexus
> > Secrete into surrounding perivascular connective tissue spaces
> > transport by hypothalamo-hypophysial portal system to Ant. pituitary (pars distalis)
> > Pars distalis release hormones into secondary capillary plexus into venous sys.
Describe how hypothalamic neurons control posterior pituitary hormone secretion?
supraoptic and paraventricular nuclei of the hypothalamus
> > produce posterior pituitary hormones
> > transported along hypothalamo-hypophyseal axon tract
> > vesicles accumulate and stored at axonal ends = HERRING BODIES
> > release into blood capillaries and veins
How are neurohormones in the pars nervosa carried from thalamus to axon endings?
Via specific transport protein Neurophysin > carry Vp and oxytocin within pars nervosa
Name the releasing/ inhibiting hormones of FSH and LH?
GnRH = stim
Name the releasing/ inhibiting hormones of ACTH
CRH = stim
Name the releasing/ inhibiting hormones of TSH
TRH = stim
Name the releasing/ inhibiting hormones of Prolactin
PRH = stim
PIH +Dopamine = inhibit
Name the releasing/ inhibiting hormones of GH/ somatotropin
Growth hormone releasing hormone = stim
Somatostatin = inhibit
Name and describe function of the glial cell in posterior pituitary?
Pituicytes = modified glial cells in post. pituitary
Support, nourish and control activity of neurosecretory axons
