Pathology 104 Read G&H chap 13

November 12, 2003

ENDOCRINES

Pituitary = Hypophysis

Pituitary = Hypophysis 1. Overall functions

of the pituitary: 1. to provide neural and hormonal control

over the major endocrine systems of the body.

2. to allow the brain to secrete hormones as true endocrines.

2. Development

The pituitary arises from both the neurotube and ectoderm.

The adenohypophysis buds off of the epithelium of the roof of the mouth.

The neurohypophysis is an extension of the floor of the brain.

3. Anatomy:

Draw arrows from the names to the parts of the pituitary.

Fill in the ( )'s beside each term with:

N for neurohypophysis or A for adenohypophysis.

Indicate the pairs of terms which are synonyms.

Locate the meninges, sella turcica and optic chiasm

Hypothalamus

( ) Pars distalis

( ) Anterior lobe

( ) Pars intermedia

( ) Pars nervosa See FIGURES 13-1

( ) Posterior lobe and 13-2

( ) Infundibulum

( ) Neuro stalk

( ) Pars tuberalis

( ) Median eminence

Posterior pituitary

List the two hormones that are released from the posterior lobe?

Hormone Function

_ADH________ _WATER RESORPTION FROM THE KIDNEY__________

_OXYTOCIN___ _CONTRACTION OF MYOEPITHELIAL CELLS IN BREAST

CONTRACTION OF SMOOTH MUSCLE OF UTERUS

Where are the hormones of posterior pituitary synthesized?

_SUPRAOPTIC AND PARAVENTRICULAR NUCLEI___________________

Define a Herring Body. _AXON AND AXON TERMINALS CONTAINING___

_SECRETORY GRANULES WITH OXYTOCIN AND ADH________________

Define a Pituicyte. _GLIAL CELL OF THE NEUROPITUITARY________

Anterior pituitary

Structure:

Describe the remnants of Rathke's cleft in adult humans.

_A SERIES OF COLLOID-FILLED CYSTS_________________________

What fills the cysts of the pituitary?

_COLLOID__________________________________________________

Cells & hormones:

List the two main categories of cells in the anterior pituitary.

_CHROMOPHILS AND CHRAOMOPHOBES____________________________

List the main subcategories of each of these categories.

_BASOPHILS________________________________________________

_ STEM CELLS, DEGRANULATED CHROMOPHILS OTHERS ??__________

Fill in the cell types of the adenohypophysis.

Name of Staining Hormone Target organ

cell type pattern produced for hormone

1. _SOMATOTROPE__ _ACIDOPHILIC _GROWTH HORMONE _LIVER ETC_*__

2. _MAMMOTROPE___ _ACIDOPHILIC _PROLACTIN_____ _BREAST_______

3. _GONADOTROPE__ _BASOPHIL___ _LH AND FSH____ _GONADS_______

4. _THYROTROPE___ _BASOPHIL___ _TSH___________ _THYROID______

5. _CORTICOTROPE_ _BASOPHIL___ _ACTH___________ _ADRENAL CORTEX

* Note: Growth hormone acts via somatomedins from the liver.

Hormone secretion from the pars distalis is controlled in two ways:

A. By hormones secreted by the brain.

List an example of a hypothalamic releasing hormones and a hypothalamic inhibiting hormone.

Stimulatory inhibitory

TRH CRH GRH GnRH SRH PIF

Where are the cells which secrete these hormones located?

_HYPOTHALAMUS________________________________________

Mark their location on the diagram of the pituitary.

How do these releasing hormones get to their target?

_____ hypothalamo-hypophyseal portal system_____________

Define the five components of a portal blood system.

ARTERY CAPILLARY PORTAL VESSEL CAPILLARY VEIN

1 2 3 4 5

Locate 1-5 on the diagram of the pituitary

B. By feedback of the hormones from the target organs.

Advanced question on the staining of the pituitary

Does a polychrome stain stain Herring bodies the same color

as acidophils or basophils? How about H+E stain?

With a polychrome stain the herring bodies would stain the

same general color as those of acidophils, since both are

simple peptides without any carbohydrate (ALLOWING PAS STAINING).

With H+E acidophils, basophils and herring bodies would STAIN similarLY, i.e. eosinophilic.

The Thyroid gland

The thyroid lies at the base of the larynx as a pair of lobes.

It is composed of epithelium-lined follicles surrounded by a

minimum of highly vascular C.T.

Two cell types in the thyroid secrete two unrelated hormones.

Follicular cells secrete thyroxine.

Parafollicular cells secrete calcitonin.

Follicle cells form a simple cuboidal epithelium around follicles.

Their apexes are at the lumen and basal lamina, outside.

The follicles are filled with colloid, consisting mainly of

thyroglobulin.

Follicular cells secrete in both an endocrine and exocrine

manner to produce thyroxine.

A. Synthesis and iodination of thyroglobulin:

Follicular cells secrete thyroglobulin into the lumen of

the follicles in a typical exocrine manner, via:

RER --> Golgi --> Secretory vesicles --> Fusion across the

apical membrane

Thyroglobulin is iodinated after secretion.

Enzymes in the apical cell membrane add iodine to the

tyrosine units of the thyroglobulin in follicles.

Iodinated thyroglobulin is a storage precursor for thyroxine.

B. Release of thyroxine:

Follicular cells phagocytize droplets of colloid.

Lysosomes fuse with the phagosomes to hydrolyze

the thyroglobulin to amino acids.

Two molecules of iodinated tyrosine are fused and

modified to produce one thyroxine molecule.

The thyroxine is secreted across the base of the cells.

C. Thyroxine is secreted in two forms, T3 and T4.

T4 is the main secretory form.

T3 is the more active form.

Various tissues convert T4 to T3.

Functions of thyroid hormones:

to regulate temperature by stimulating metabolism

to regulate electrolytes, water, protein and fat metabolism

to stimulate normal development (especially of the CNS)

to maintain normal excitability of the CNS

Regulation of thyroxine secretion:

(See yesterday's lecture notes on control by the

pituitary including TRF, TSH, and the "thyrostat").

Both hypothyroid and hyperthyroid conditions can cause

goiter, an enlargement of the thyroid gland.

If the pituitary over produces TSH:

the thyroid will be overactive.

too much thyroxine will be secreted.

the gland will enlarge.

A deficiency of iodine will cause:

circulating levels of thyroxine to decrease.

circulating levels of TSH to increase.

follicular cells to synthesize and hydrolyze

thyroglobulin at an increased rate.

follicles to enlarge.

Parafollicular cells (=C or clear cells):

are located in the C.T. between the follicles,

(and are difficult to see unless specially stained).

secrete calcitonin, which decreases blood Ca++ levels,

mainly by inhibiting osteoclast activity.

The parathyroid gland

A pair of parathyroid glands are located on the posterior side

of each lobe of the thyroid.

They secrete parathyroid hormone = parathormone = PTH.

This peptide increases blood calcium levels in several ways:

by increasing osteoclast activity

by causing osteocytes to absorb Ca++

by decreasing bone formation

by increasing absorption of Ca++ from kidneys and gut

Histologically, the parathyroid is unspectacular (to say the least).

The small, numerous principal (=chief) cells stain poorly.

They secrete parathormone.

A few larger, acidophilic oxyphil cells are scattered about.

Their function is unknown.

The Adrenal gland

The adrenal is two glands in one.

The adrenal cortex, from mesoderm, secretes steroid hormones.

The adrenal medulla, from neurocrest, secretes catecholamines.

The adrenal cortex has three layers with different functions.

Each consists of epithelial cells arranged along sinusoids.

(enlarged capillaries with fenestrated epithelium.)

A. Zona glomerulosa

The cells are small, with dark nuclei and arranged in clusters.

Its hormone, aldosterone, (a mineralocorticoid):

1. increases Na+ resorption from distal convoluted tubules

of the kidneys and from the stomach.

2. increases blood pressure and blood volume.

The renin-angiotensin system regulates aldosterone synthesis.

B. Zona fasciculata

This zone has larger polyhedral cells with paler nuclei.

Their cytoplasm appears pale and highly vacuolated due to

numerous lipid droplets.

The cells secretes glucocorticoids, mainly cortisol.

Cortisol has diverse functions,

mainly to regulate carbohydrate and protein metabolism,

also to suppress the immune system and inflammation.

ACTH from the pituitary regulates this zone.

C. Zona reticularis

Its small, darker cells are arranged in irregular clusters.

They secrete androgens (in both men and women).

Secretion is stimulated by ACTH.

Before birth an extra, inner, transient "fetal zone" is present.

It cooperates with the placenta to provide steroid hormones

for the fetus.

The Adrenal medulla

Neural crest cells migrate into the embryonic adrenals and

differentiate into endocrine cells, instead of nerve cells

(except for a few ganglion cells).

These chromaffin cells secrete epinephrine and norepinephrine.

Epinephrine (adrenalin) produces the familiar "flight or

fight" physiological changes in response to stress.

Norepinephrine maintains blood pressure and vascular tone.

Preganglionic sympathetic fibers regulate secretion.

Blood supply

Capsular arteries furnish two blood supplies:

A. Cortical sinusoids descend through the cortex and

drain into the medullary sinusoids.

B. Medullary arterioles traverse the cortex and deliver

arterial blood directly into the medullary sinusoids.

Medullary sinusoids drain into medullary veins.