(04) Endocrine System - Pineal Gland

Question 1

1. What is pineal gland aka?
2. a cone shaped projection from roof of what?
3. Develops as a neuroectodermal evagination of what?

Answer 1

1. epiphysis cerebri
2. third ventricle
3. the dorsocaudal part of the diencephalon (epithalamus)

Question 2

(Pineal Gland - location/structure)

1. Located caudal to what? with a capsule that is dorsally what and ventrally what?
2. By virtue of this anatomic location, what may impede vascular drainage in the nearby dural sinuses?

Answer 2

1. anterior choroid plexus; dorsally pia mater and ventrally ependyma
2. pineal tumors

Question 3

1. Parenchyma of pineal gland consists of what?

2. These cells are acidophilic or basophilic?
3. many processes?
4. what kind of nucleus

5. what do these cells secrete?

Answer 3

1. pinelocytes

2. acidophilic
3. yes
4. leptochromatic
5. melatonin

Question 4

1. Stroma of pineal gland consists of what?
2. size?
3. nuclei dark or light?
4. function?

Answer 4

1. glial cells (astrocytes)
2. small
3. dark
4. supportive

Question 5

1. What is a unique histological feature of the pineal gland?
2. What are they?
3. Increase or Decrease with age?
4. Can they be seen on radiographs?
5. Functional Significance known?

Answer 5

1. Corpora Arenacea (brain sand)
2. calcaneous concretions (calcium phosphates and carbonates)
3. increase
4. yes (serve as a useful clue for identification of this organ on histological sections)
5. no

Question 6

(Vascularity of Pineal Gland)

1. Sinusoidal (leaky)* capillaries
2. Is there a blood brain barrier? what does this mean?

Answer 6

2. no, secretions have easy access to blood

Question 7

(Melatonin)

1. What kind of thing is it?
2. What is the precursour?

Answer 7

1. an indoleamine (a family of neurotransmitters from the AA tryptophan)
2. serotonin

Question 8

(Role of Melatonin)

1. inhibit or stimulate secretion of gonadotropin releasing hormone from the hypothalamus?
2. results in increase or decrease production of hormones (FSH, LH) by the gonads?
3. What is the result?
4. Because Melatonin receptors are present in a large number of structures what occurs?

Answer 8

1. inhibit
2. decrease
3. melatonin influences the seasonal sexual acitivty of animals (ie setting seasonal cyclea and influencing coat color changes and hibernation)
4. affects from this hormone can be quite wide ranged

Question 9

(Pathway to Melatonin Production)

1. Melatonin production is linked to what and influences what as a result?

2. During the dark phase of the photoperiod (light dark/cycle) there is a stimulation of what that results in what?

Answer 9

1. light/dark visual signals; influences circadian rhythm (daily cycle of biological activity during a 24 hour period)

2. stimulation of pinealocyte that produces melatonin

Question 10

(Pathway of melatonin production cont)

1. In lower vertebrates (eg amphibians) the pineal is a what and is stimulated directly or indirectly?

2. Light/dark info is transmitted through what?
3. In this species melatonin results in an aggregation of what which results in what?
4. What causes an overall darkening of the skin?

Answer 10

1. a photoreceptor; directly

2. thin skull bones (direct stimulation or inhibition of pineal gland)
3. pigment granules; lightening of skin color
4. melanocyte stimulating hormone will cause a dispersal of pigment granules

Question 11

(Pathway of melatonin production)

1. How is pineal gland stimulated in mammals?

2. What is the pathway for said stimulation?

Answer 11

1. indirectly

2. light signal to retina –> suprachiasmatic nucleus (hypothalamus) –> cranial cervical ganglion –> pineal (via postganglionic fibers which then directly stimulate the pinealocyte to produce melatonin)

*This is an exmpale of the simulation of the sympathetic nervous system resulting in the stimulation of a cell that produces a hormone