Hypophysis (pituitary)
Name another hormone that stimulates GH secretion
- Ghrelin
Dopamine inhibits which adenohypophysis hormone
- PRL by Lactrotropes
Major cells of the adenohypophysis
- chromophils - chromophobes
Name 3 Basophils and their product
- corticotrope: adrenocorticotropic hormone (ACTH) and beta lipotropin - Gonadotrope: follicle stimulating hormone (FSH) and luteinizing hormone (LH) - Thyrotrope: thryotropic hormone (TSH)
Follicle-stimulating hormone (FSH) stimulate
- development of ovarian follicles and spermatogenisis
Location of pars intermedia
- pars distalis and pars nervosa
adenohypophysis is developed from
An outpocketing of the oral ectoderm, which forms a structure called Rathke's pouch
Milk ejection reflex consists of
Neuronal afferent limb and hormonal efferent limb
Pituicytes
Non-neuronal cells that do not produce hormones, that have tropic and support role
Gigantism
Overproduction of growth hormone before closure of bone epiphyses causes unusual proportional growth
Functions of oxytocin
- Causes contraction of smooth muscle cells in myometrium of pregnant uterus - Causes contraction of myoepithelial cells in the lactating mammary gland
List the releasing and inhibiting hormones from the hypothalamus
- Growth hormone releasing hormone (GHRH) - Somatostatin - Dopamine - Corticotropin-releasing hormone (CRH) - Gonadotropin- releasing hormone (GnRH) - Thyrotropin- releasing hormone
Gonadotropin-releasing hormone (GnRH) stimulates which adenohypophysis hormone
- LH and FSH by gonadotropes
Name the two hormones found at the Neurohypophysis
- Oxytocin - Antidiurectic hormone
Types of cells found at the neurohypophysis
- Pituicytes - Unmyelinated axons
Name the 2 acidophils (type of chromphil cells) and their product
- Somatrope: growth hormone (GH) - Lactrotrope: prolactin (PRL)
Name two hormones that also stimulate PRL secretion via Lactrotropes
- TRH and Vasoactive inhibitory peptide (VIP)
Of the two lobes, which can produces its own hormones and which receives hormones produced from the hypothalamus
- adenohypophysis calls make their own hormones - neurophypohysis receives hormones from the hypothalamus
Chromophobes
- another cell type found in the adenohypophysis - small cells, occur in clusters, heterogenous population
Hypophysis is composed of two lobes
- anterior (adenohypophysis) - posteriors (neurohypophysis)
Name the cells found in Pars intermedia
- basophils and chromophobes
Growth hormone-releasing hormone (GHRH) stimulates which adenohypophysis hormone
- growth hormone by somatotropes
Somatostain inhibits which adenohypophysis hormone
- growth hormone by somatotropes
Describe hormonal efferent limb
- hypothalamic terminal axons release oxytocin into neurohypophysis. Then travels to the mammary gland via blood cause the myoepithelial cells to contract, enhancing milk ejection.
Two major mechanisms for adenohypophysis regulation
- hypothalamus produces stimulating or inhibitory hormones that affect hormone production of basophils or acidophils - negative feedback; product of target organs inhibits hormone production by acidophils and basophils
Functions of antidiuretic hormone (ADH)
- increases blood pressure by acting on vascular smooth muscle - promotes fluid resorption at the collecting ducts in the kidney
Neurohypophysis is supplied by
- inferior hypophyseal artery
What happens to Rathkes pouch during development
- it fragments into small cysts called Rathkes cysts which remain in pars intermedia
luteinizing hormone (LH) stimulates
- maturation of ovarian follicles and androgen secretion by testis
Location of the primary plexus of the hypothalamo-hypophyseal
- median eminence and infundibular processes
Via H&E, how do the neurohypophysis and adenohypophysis differe
- neurohypophysis is pale staining - adenohypophysis is dark staining
Describe direct innervation of hypothalamus
- neurons from hypothalamus extend into the neurohypophysis, where they secrete hormones into the blood to travel to target organs
Describe indirect innervation of hypothalamus
- neurons release hormones into venus portal system to adenohypophysis. There the production of hormones via cells of the anterior pituitary is regulated. Then those hormones are secreted into blood and to their target organs
Protein that oxytocin and ADH associate with in granules
- neurophysins
The two hormones that neurohypophysis receives from hypothalamus
- oxytocin - vasopressin (Antidiuretic hormone)
Location of the secondary plexus of the hypothalamo-hypophyseal portal system
- pars distalis
Three parts of the neurohypophysis
- pars nervosa - infundibular process - median eminence
Thyrotropic hormone (TSH)
- stimulates synthesis of thyroid hormones, T3 & T4
Describe the neuronal afferent limb
- suckling stimulates afferent nerve endings in the nipple, impulses travels to hypothalamus
The main blood supply for the primary plexus of the hypothalamo-hypophyseal portal system
- superior hypophysis artery
What type of axons can be found in neurohypophysis
- unmyelinated axons, whose cell bodies are found in the hypothalamus
Chromaphils have __________ acidophils and ________basophils
2 acidophils - somatrope - lactrotrope 3 basophils - corticotrope - gomadotrope - thyrotrope
Herring bodies
Accumulation of secretory granules in the nerve terminals and neuronal axon. Characteristic of neurohypophysis.
At which part of the adenohypophysis, would we find the most cells
Pars distalis
Brain endocrine axis consist of
Pituitary gland and hypothalamus
Growth hormone stimulates
Production of insulin-like growth factor (IGF-1) by liver cells. When secreted they target muscle and bone to produce growth
Adrenocorticotropic hormone (ACTH) stimulates
Synthesis of glucocorticoids and gonadocorticoids by adrenal cortex
Thyrotropin-releasing hormone (TRH) stimulates which adenohypophysis hormone
TSH by thyrotropes
What is a portal system?
blood flows through two capillary beds that's are connected in series before returning to the heart
Acromegaly
overproduction of growth hormone after epiphyses closure causes enlarged hands and feet
Three parts of the adenohypophysis
pars distalis, pars intermedia, pars tuberalis
The hypophysis is another name for
pituitary gland
Graces disease
Autoimmune disease where receptors are produced against TSH receptors and promotes the affects of TSH hormone. Over production of T3 and T4 hormones
location of hypophysis
Base of the brain. In a small depression of the sphenoid bone, Sella turcica (Turkish saddle)
Rathke cysts is lined by
Cuboidal cells
Insufficiency or absence of ADH results in
Diabetes insipidus
Hypothalamus contributes to homeostasis via
Direct and indirect innervation
T/F. Neurohypophysis does not receive direct innervation from hypothalamus
False, recieves direct innervation from hypothalamus
T/F Hypothalamo-hypophyseal portal system is an arterial portal system
False. It is a venous portal system. The primary and secondary capillary plexus are connected via hyphyseal portal vein
T/F. Similar to neurohypophysis, the adenohypophysis receives direct innervation from hypothalamus
False. It receive indirect innervation
T/F. Lactrotropes similar to other cell types store their excess secretory granules within their cytoplasm until stimulated to release
False. Lactrotropes secretory granules are destroyed by lysosomal enzymes via crinophagy
arterial portal system
First capillary bed (primary plexus) is connected to another capillary bed (secondary plexus) via arteries
Venous portal system
First capillary bed (primary plexus) is connected to another capillary bed (secondary plexus) via vein
Compared to the blood brain barrier, the plexus have
Highly permeable fee started capillaries
The blood supplied to adenohypophysis is known as
Hypothalamo-hypophyseal portal system
The neurons found between hypothalamus and neurohypophysis make up the
Magnocellular neurosecretory system
Prolactin hormone stimulates
Mammary gland development and lactation.
neruohypophysis develops from
Neuroectoderm in the floor of the diencephalon. Maintains its connection via infundibulum
Corticotropin-releasing hormone (CRH) stimulates which adenohypophysis hormone
- ACTH by corticotropes