BIOL 324 Histology Endocrine System 12/10/15-12/15/15

Diffuse neuroendocrine system (DNES)

cells with different function then just the secretion of hormones but found throughout the body.

Examples of DNES cells

-gut (enteroendocrine cells)

-lung (small dense core granule cells)

-skin (merkel cells)

-testes and ovaries

Multiple function organs

secrete hormones (endocrine) in part, but also have another main function. Not simply endocrine in nature. Example: DNES cells

Discrete endocrine glands

only thing they do is secrete hormones

1. hypophysis/pituitary

2. thyroid

3. parathyroid

4. adrenal

5. pineal

Where is the Pituitary

located anterior to brain stem and hanging off the base of the brain.

Development of pituitary

given inferior surface of brain, it is flat early on, but at some point, a little stalk of tissue grows out, increases in size and extends down from the brain tissue. It develops an infundibulum and neurohypophysis

Infundibulum

-neural tissue, first part of pituitary to grow down from inferior brain

Neurohypophysis in development

neural tissue that includes the infundibulum and bulbous bottom part that forms to make the pituitary.

Rathke's pouch

the part onthe roof of the mouth that swells up upon contact with the pituitary gland bulbous part. IT ends up braking away from the roof of the mouth and wrapping around the infundibulum

adenohypophysis in development

part of the pituitary that is glandular tissue, as it came from the room of the mouth.

posterior pituitary/neurohypophysis

neural tissue part of pituitary with 3 parts:

1. pars nervosa

2. infudibulum

3. median eminance (closer to base of brain)

pars nervosa

the swollen, bulbous part at the end of the infundibulum

anterior pituitary/adenohypophysis parts

glandular tissue part of pituitary with 3 parts

1. pars tuberalis

2. pars distalis

3. pars intermedia

circulatory system of pituitary

-This allows for coordination of activity between the neural and glandular tissue parts of the pituitary

arteries in accordance with the pituitary gland

-includes the (1) superior hypophyseal arteries and the (2) inferior hypophyseal artery.

-These sets involved in function of pituitary help supply blood to the pituitary and hypothalamus

-arterial blood goes directly to nervous tissue-nerohypophysis

superior hypophyseal arteries

2 pairs of arteries coming from the internal carotid arteries extending to the region of the median eminence and base of infundibulum. It splits into 2 like a fork to surround the base of the hypothalamus/brain by one going around the front and the other going around behind. They breakup immediately into capillaries.

inferior hypophyseal artery

the artery that comes from the bottom of the bulbous pars nervosa to supply nervous tissue directly with blood.

Primary capillary plexuses

-the superior hypophyseal arteries give rise to these bundles of tissue which allow for the diffusion of things through blood, like hormones.

-They pass through here and then to hypophyseal portal veins

nature of capillaries

-they are the location of where diffusion occurs, allowing substances in and out of circulation.

-Other vessels not as porus, so not for diffusion.

-sends from arteries to here to veins to heart

hypophyseal portal veins

-on later side of primary capilary plexus

-promote diffusion for capillaries, and are passageways to deliever that blood to another location.

-1 for each primary plexus that drains into the pars distalis of the adenohypophysis (the granular part of they pituitary)

Whats special about portal veins

while veins commonly take blood back to heart, these veins are short and act as shunts that take blood from a capillary bed to another capillary bed.

secondary capillary plexus

-later end of the portal veins around pituitary

-is designed to diffuse things in an out of circulation

-must leave pituitary and send to general circulation

hypophyseal veins

the end result of the superior hypophyseal arteries.

1. superior h.a.

2. primary capillary plexuses

3. hypophyseal portal veins

4. secondary capillary plexus

5. hypophyseal veins

Neurohypophysis tissue

-from brain, made of generally large, linear neurons (mostly), starting in hypothalamus

-2 groupings of cell bodies in hypothalamus that extend all the way down to the pars nervosa (end neurohypophysis)

-2 nuclei

-hypothalamus-hypophyseal tract

Nuclei of pituitary

-groups of cell bodies in the nervous system.

1. Supraoptic

2. paraventicular nuclei

hypothalamus-hypophyseal tract

-axons from supraoptic and paraventricular nuclei start separated but join as a single group before

going to pas nervosa

-these neurons are secretory, secreting peptide hormones made by the hypothalamus

Hormones of hypothalamus-hypophyseal tract

1. antidiuretic hormone (ADH)

2. Oxytocin

ADH

-secreted by supraoptic nucleus that was formed in hypothalamus

-has an influence on low blood pressure and volume blood.

-this hormone "changes the size of the container," decreasing the size of the circulatory system make the lumen of vessels smaller to raise pressure.

-this hormone also influences kidneys to conserve water by stimulating smooth muscle cells in the wall of arteries.

-collecting ducts (kidneys)*

what is the relationship between blood volume and pressure?

-as blood volume decreases, blood pressure decreases (Direct relationship)

-ADH stimulates smooth muscle cells in the walls of arteries to decrease the size of the circulatory system lumen and this increases blood pressure without affecting volume.

How does ADH influence the kidneys

The hormone causes the kidney to conserve water by affecting collecting ducts to not secrete urine but actually having the liquid go back into the blood.

diabetes insipidis

receptors of kidneys don't comibe ADH from either lack of ADH or receptor problems. the result is a lot of urine that is lost quickly so they have to drink a lot of water

Polyurea

problems with ADH cause excessive urination

Oxytocin

-secreted from pars nervosa, characterized having to do with lactation and many female effects. Particularly with first kind of release of milk (affecting mammary glands). even before, causes contractions in uterus.

-"Love hormone" for social activities

Neurophysin

-binding protein and transport protein part of the Hormones of hypothalamus-hypophyseal tract

-combines to ADH or oxytocin to travel down to and store in the pars nervosa

-storage accumulates overtime, creating a distinct histological appearance, showing herring bodies

herring bodies

swollen axon terminals containing granules of neurophysin mixed with Oxytocin and ADH.

Pituicytes

supportive cells mixed in with axons of neurons in the pituitary that are distinctively pigmented.

Adenohypophysis

-has 5 different kinds of cells in 3 different regions

-secretes hormones of a given class- tropic hormones

tropic hormones

-secreting hormones that simulate another location to target and activate cells to increase activity.

Hypothalamus

-functions to control the release of hormones from the adenohypophysis by secreting hypothalamic regulating factors

-where do they go and what do they do? must understand generalized mechanism

hypothalamic regulating factors

1. releasing factors stimulate secretion

2. inhibiting factors inhibit secretion

Mechanism of releasing factors

Example testosterone

1. stimulus in hypothalamus

2. releasing factor released by hypothalamus

3. primary capillary plexuses picks up this factor

4. plexuses drain to the hypophyseal portial veins,

5. portal veins shove blood to pars distalis secondary adenohypophysis

6. pars distalis cells with receptors for factor are stimulated and secrete tropic hormones

7. tropic hormones travels to target cells through circulatroy system

8. target cells release an effector hormone

9. effector hormone travels through circulatory system to hypothalamus so it senses

How are regulating factors feedback loops?

1. the production of a releasing factor travels through the circulatory system to the pars distalis.

2. Pars distalis cells secrete tropic hormones to affect target cells

3. target cells secrete effector hormone that travels through circulatory system

4. hypothalamus sees high concentration of effector hormone. This relieves the stimulus of hypothalamus to secrete releasing factor.

pars distalis

-its the largest part of pituitary with 3 cell types

1. somatotropic

2. lactotropic

[ ^all acidophils]

3. gonadotropic

4. thyrotropic

5. adenocorticotropic

[^basophils]

somatotropic

-secrete growth hormones that influence long bone growth

-acidophil

lactotropic

-secretes prolactin to influence lactation in mammary glands in females. In males, influence testes production of testosterone with coordination with LH

-acidophil

gonadotropics

-some secretes LH, some secrete FSH, others secrete both

-in females this influences ovulation

-in males this influences leydig cells to secrete testosterone and influence cell division

-acidophil

thyrotropic

-secretes thyroid stimulating hormone (TSH) to stimulate the thyroid to secrete T3 and T4 thyroid hormones.

-Affects metabolism

-basophil

adenocorticotropic

-produce adrenocorticotropin (ACTH) that affects adrenal cortex to produce gluccocorticoids affecting metabolism

-basophil

glucocorticoids

steroid hormones from cortexaffecting sugar metabolism

acidophils

has an affinity for acid dye, staining pink

basophils

has an affinity for basic dyes

pars intermedia

-smallest part of the pituitary

-secretes MSH, but we don't know the importance of the hormone in humans

-cells are possibly a modified version of adrenocorticotropic cells

MSH

-Melanocyte stimulating hormone

-similar to ACTH

pars tuberalis

-part of pituitary that has gonadotropic cells with LH and FSH components to them.

-despite these components, they seem to also have melatonin receptors, which means they have a relationship to pineal gland with relation to daylight cycles.